diff --git a/cranelift/codegen/src/isa/aarch64/lower.isle b/cranelift/codegen/src/isa/aarch64/lower.isle
index 7b69dd977f..50a97d9203 100644
--- a/cranelift/codegen/src/isa/aarch64/lower.isle
+++ b/cranelift/codegen/src/isa/aarch64/lower.isle
@@ -2,7 +2,7 @@
 
 ;; The main lowering constructor term: takes a clif `Inst` and returns the
 ;; register(s) within which the lowered instruction's result values live.
-(decl lower (Inst) ValueRegs)
+(decl lower (Inst) InstOutput)
 
 ;;;; Rules for `iconst` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
diff --git a/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest b/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest
index dd88d5e08c..d11e3f178d 100644
--- a/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest
+++ b/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.manifest
@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 8bf92e18323e7041
+src/prelude.isle 957023853b23dacb
 src/isa/aarch64/inst.isle 3678d0a37bdb4cff
-src/isa/aarch64/lower.isle 1bc1f817a4721801
+src/isa/aarch64/lower.isle 90accbfcadaea46d
diff --git a/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.rs b/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.rs
index d796860501..94b4f9d3a6 100644
--- a/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.rs
+++ b/cranelift/codegen/src/isa/aarch64/lower/isle/generated_code.rs
@@ -25,6 +25,12 @@ pub trait Context {
     fn value_reg(&mut self, arg0: Reg) -> ValueRegs;
     fn value_regs(&mut self, arg0: Reg, arg1: Reg) -> ValueRegs;
     fn value_regs_invalid(&mut self) -> ValueRegs;
+    fn output_none(&mut self) -> InstOutput;
+    fn output(&mut self, arg0: ValueRegs) -> InstOutput;
+    fn output_pair(&mut self, arg0: ValueRegs, arg1: ValueRegs) -> InstOutput;
+    fn output_builder_new(&mut self) -> InstOutputBuilder;
+    fn output_builder_push(&mut self, arg0: &InstOutputBuilder, arg1: ValueRegs) -> Unit;
+    fn output_builder_finish(&mut self, arg0: &InstOutputBuilder) -> InstOutput;
     fn temp_writable_reg(&mut self, arg0: Type) -> WritableReg;
     fn invalid_reg(&mut self) -> Reg;
     fn put_in_reg(&mut self, arg0: Value) -> Reg;
@@ -102,13 +108,13 @@ pub trait Context {
     fn rotr_opposite_amount(&mut self, arg0: Type, arg1: ImmShift) -> ImmShift;
 }
 
-/// Internal type SideEffectNoResult: defined at src/prelude.isle line 308.
+/// Internal type SideEffectNoResult: defined at src/prelude.isle line 345.
 #[derive(Clone, Debug)]
 pub enum SideEffectNoResult {
     Inst { inst: MInst },
 }
 
-/// Internal type ProducesFlags: defined at src/prelude.isle line 330.
+/// Internal type ProducesFlags: defined at src/prelude.isle line 367.
 #[derive(Clone, Debug)]
 pub enum ProducesFlags {
     ProducesFlagsSideEffect { inst: MInst },
@@ -116,7 +122,7 @@ pub enum ProducesFlags {
     ProducesFlagsReturnsResultWithConsumer { inst: MInst, result: Reg },
 }
 
-/// Internal type ConsumesFlags: defined at src/prelude.isle line 341.
+/// Internal type ConsumesFlags: defined at src/prelude.isle line 378.
 #[derive(Clone, Debug)]
 pub enum ConsumesFlags {
     ConsumesFlagsReturnsResultWithProducer {
@@ -995,10 +1001,28 @@ pub enum AtomicRMWOp {
     Umin,
 }
 
+// Generated as internal constructor for term output_reg.
+pub fn constructor_output_reg<C: Context>(ctx: &mut C, arg0: Reg) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 86.
+    let expr0_0 = C::value_reg(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
+// Generated as internal constructor for term output_value.
+pub fn constructor_output_value<C: Context>(ctx: &mut C, arg0: Value) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 90.
+    let expr0_0 = C::put_in_regs(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
 // Generated as internal constructor for term temp_reg.
 pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 73.
+    // Rule at src/prelude.isle line 110.
     let expr0_0 = C::temp_writable_reg(ctx, pattern0_0);
     let expr1_0 = C::writable_reg_to_reg(ctx, expr0_0);
     return Some(expr1_0);
@@ -1007,26 +1031,26 @@ pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg>
 // Generated as internal constructor for term lo_reg.
 pub fn constructor_lo_reg<C: Context>(ctx: &mut C, arg0: Value) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 108.
+    // Rule at src/prelude.isle line 145.
     let expr0_0 = C::put_in_regs(ctx, pattern0_0);
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
     return Some(expr2_0);
 }
 
-// Generated as internal constructor for term value_regs_none.
-pub fn constructor_value_regs_none<C: Context>(
+// Generated as internal constructor for term side_effect.
+pub fn constructor_side_effect<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 313.
+        // Rule at src/prelude.isle line 350.
         let expr0_0 = C::emit(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -1036,15 +1060,15 @@ pub fn constructor_value_regs_none<C: Context>(
 pub fn constructor_safepoint<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 319.
+        // Rule at src/prelude.isle line 356.
         let expr0_0 = C::emit_safepoint(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -1068,7 +1092,7 @@ pub fn constructor_consumes_flags_concat<C: Context>(
             result: pattern3_1,
         } = pattern2_0
         {
-            // Rule at src/prelude.isle line 353.
+            // Rule at src/prelude.isle line 390.
             let expr0_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
             let expr1_0 = ConsumesFlags::ConsumesFlagsTwiceReturnsValueRegs {
                 inst1: pattern1_0.clone(),
@@ -1098,7 +1122,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst: ref pattern3_0,
                     result: pattern3_1,
                 } => {
-                    // Rule at src/prelude.isle line 378.
+                    // Rule at src/prelude.isle line 415.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_0);
                     let expr2_0 = C::value_reg(ctx, pattern3_1);
@@ -1109,7 +1133,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst2: ref pattern3_1,
                     result: pattern3_2,
                 } => {
-                    // Rule at src/prelude.isle line 384.
+                    // Rule at src/prelude.isle line 421.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_1);
                     let expr2_0 = C::emit(ctx, pattern3_0);
@@ -1128,7 +1152,7 @@ pub fn constructor_with_flags<C: Context>(
                 result: pattern3_1,
             } = pattern2_0
             {
-                // Rule at src/prelude.isle line 372.
+                // Rule at src/prelude.isle line 409.
                 let expr0_0 = C::emit(ctx, pattern1_0);
                 let expr1_0 = C::emit(ctx, pattern3_0);
                 let expr2_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
@@ -1148,7 +1172,7 @@ pub fn constructor_with_flags_reg<C: Context>(
 ) -> Option<Reg> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/prelude.isle line 397.
+    // Rule at src/prelude.isle line 434.
     let expr0_0 = constructor_with_flags(ctx, pattern0_0, pattern1_0)?;
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -3409,7 +3433,7 @@ pub fn constructor_i128_alu_bitop<C: Context>(
 }
 
 // Generated as internal constructor for term lower.
-pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueRegs> {
+pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let Some(pattern1_0) = C::first_result(ctx, pattern0_0) {
         let pattern2_0 = C::value_type(ctx, pattern1_0);
@@ -3430,7 +3454,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 24;
                         let expr5_0 = C::imm_shift_from_u8(ctx, expr4_0);
                         let expr6_0 = constructor_lsr_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Clz => {
@@ -3442,7 +3466,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 24;
                         let expr5_0 = C::u8_into_imm12(ctx, expr4_0);
                         let expr6_0 = constructor_sub_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Cls => {
@@ -3454,7 +3478,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 24;
                         let expr5_0 = C::u8_into_imm12(ctx, expr4_0);
                         let expr6_0 = constructor_sub_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Ctz => {
@@ -3469,7 +3493,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0 = C::u64_into_imm_logic(ctx, expr5_0, expr6_0);
                         let expr8_0 = constructor_orr_imm(ctx, expr1_0, expr4_0, expr7_0)?;
                         let expr9_0 = constructor_a64_clz(ctx, expr0_0, expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                     &Opcode::Popcnt => {
@@ -3482,7 +3506,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr5_0: u8 = 0;
                         let expr6_0 = VectorSize::Size8x16;
                         let expr7_0 = constructor_mov_from_vec(ctx, expr4_0, expr5_0, &expr6_0)?;
-                        let expr8_0 = C::value_reg(ctx, expr7_0);
+                        let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                         return Some(expr8_0);
                     }
                     _ => {}
@@ -3506,7 +3530,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 16;
                         let expr5_0 = C::imm_shift_from_u8(ctx, expr4_0);
                         let expr6_0 = constructor_lsr_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Clz => {
@@ -3518,7 +3542,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 16;
                         let expr5_0 = C::u8_into_imm12(ctx, expr4_0);
                         let expr6_0 = constructor_sub_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Cls => {
@@ -3530,7 +3554,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr4_0: u8 = 16;
                         let expr5_0 = C::u8_into_imm12(ctx, expr4_0);
                         let expr6_0 = constructor_sub_imm(ctx, expr0_0, expr3_0, expr5_0)?;
-                        let expr7_0 = C::value_reg(ctx, expr6_0);
+                        let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                         return Some(expr7_0);
                     }
                     &Opcode::Ctz => {
@@ -3545,7 +3569,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0 = C::u64_into_imm_logic(ctx, expr5_0, expr6_0);
                         let expr8_0 = constructor_orr_imm(ctx, expr1_0, expr4_0, expr7_0)?;
                         let expr9_0 = constructor_a64_clz(ctx, expr0_0, expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                     &Opcode::Popcnt => {
@@ -3560,7 +3584,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0: u8 = 0;
                         let expr8_0 = VectorSize::Size8x16;
                         let expr9_0 = constructor_mov_from_vec(ctx, expr6_0, expr7_0, &expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                     _ => {}
@@ -3604,7 +3628,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr4_0 = constructor_a64_rotr_imm(
                                                     ctx, expr0_0, expr1_0, expr3_0,
                                                 )?;
-                                                let expr5_0 = C::value_reg(ctx, expr4_0);
+                                                let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                                                 return Some(expr5_0);
                                             }
                                         }
@@ -3619,7 +3643,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I32;
                             let expr5_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr6_0 = constructor_a64_rotr(ctx, expr4_0, expr5_0, expr3_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         &Opcode::Rotr => {
@@ -3651,7 +3675,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr1_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -3663,7 +3687,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr3_0 = constructor_a64_rotr(ctx, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -3685,7 +3709,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0: u8 = 0;
                         let expr8_0 = VectorSize::Size8x16;
                         let expr9_0 = constructor_mov_from_vec(ctx, expr6_0, expr7_0, &expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                 }
@@ -3707,7 +3731,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr3_0 = constructor_umulh(ctx, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Smulhi => {
@@ -3717,7 +3741,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr3_0 = constructor_smulh(ctx, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Band => {
@@ -3728,7 +3752,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic_commutative(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bor => {
@@ -3739,7 +3763,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic_commutative(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
@@ -3750,7 +3774,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic_commutative(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::BandNot => {
@@ -3761,7 +3785,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::BorNot => {
@@ -3772,7 +3796,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::BxorNot => {
@@ -3783,7 +3807,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_alu_rs_imm_logic(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Rotl => {
@@ -3815,7 +3839,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr4_0 = constructor_a64_rotr_imm(
                                                     ctx, expr0_0, expr1_0, expr3_0,
                                                 )?;
-                                                let expr5_0 = C::value_reg(ctx, expr4_0);
+                                                let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                                                 return Some(expr5_0);
                                             }
                                         }
@@ -3830,7 +3854,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I64;
                             let expr5_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr6_0 = constructor_a64_rotr(ctx, expr4_0, expr5_0, expr3_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         &Opcode::Rotr => {
@@ -3862,7 +3886,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr1_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -3874,7 +3898,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr3_0 = constructor_a64_rotr(ctx, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ishl => {
@@ -3885,7 +3909,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr3_0 =
                                 constructor_do_shift(ctx, &expr0_0, expr1_0, expr2_0, pattern7_1)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ushr => {
@@ -3896,7 +3920,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_put_in_reg_zext64(ctx, pattern7_0)?;
                             let expr3_0 =
                                 constructor_do_shift(ctx, &expr0_0, expr1_0, expr2_0, pattern7_1)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sshr => {
@@ -3907,7 +3931,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_put_in_reg_sext64(ctx, pattern7_0)?;
                             let expr3_0 =
                                 constructor_do_shift(ctx, &expr0_0, expr1_0, expr2_0, pattern7_1)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -3929,7 +3953,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0: u8 = 0;
                         let expr8_0 = VectorSize::Size8x16;
                         let expr9_0 = constructor_mov_from_vec(ctx, expr6_0, expr7_0, &expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                 }
@@ -3963,7 +3987,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr12_0: Type = I64;
                             let expr13_0 = constructor_adc_paired(ctx, expr12_0, expr4_0, expr9_0)?;
                             let expr14_0 = constructor_with_flags(ctx, &expr11_0, &expr13_0)?;
-                            return Some(expr14_0);
+                            let expr15_0 = C::output(ctx, expr14_0);
+                            return Some(expr15_0);
                         }
                         &Opcode::Isub => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -3984,7 +4009,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr12_0: Type = I64;
                             let expr13_0 = constructor_sbc_paired(ctx, expr12_0, expr4_0, expr9_0)?;
                             let expr14_0 = constructor_with_flags(ctx, &expr11_0, &expr13_0)?;
-                            return Some(expr14_0);
+                            let expr15_0 = C::output(ctx, expr14_0);
+                            return Some(expr15_0);
                         }
                         &Opcode::Imul => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4006,7 +4032,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr14_0 = C::zero_reg(ctx);
                             let expr15_0 = constructor_madd64(ctx, expr2_0, expr7_0, expr14_0)?;
                             let expr16_0 = C::value_regs(ctx, expr15_0, expr13_0);
-                            return Some(expr16_0);
+                            let expr17_0 = C::output(ctx, expr16_0);
+                            return Some(expr17_0);
                         }
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4016,7 +4043,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4026,7 +4054,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4036,7 +4065,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::BandNot => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4046,7 +4076,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::BorNot => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4056,7 +4087,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::BxorNot => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4066,7 +4098,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_i128_alu_bitop(
                                 ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Rotl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4095,7 +4128,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr21_0 = C::value_regs_get(ctx, expr10_0, expr20_0);
                             let expr22_0 = constructor_orr(ctx, expr17_0, expr19_0, expr21_0)?;
                             let expr23_0 = C::value_regs(ctx, expr16_0, expr22_0);
-                            return Some(expr23_0);
+                            let expr24_0 = C::output(ctx, expr23_0);
+                            return Some(expr24_0);
                         }
                         &Opcode::Rotr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4124,7 +4158,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr21_0 = C::value_regs_get(ctx, expr10_0, expr20_0);
                             let expr22_0 = constructor_orr(ctx, expr17_0, expr19_0, expr21_0)?;
                             let expr23_0 = C::value_regs(ctx, expr22_0, expr16_0);
-                            return Some(expr23_0);
+                            let expr24_0 = C::output(ctx, expr23_0);
+                            return Some(expr24_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4134,7 +4169,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: usize = 0;
                             let expr3_0 = C::value_regs_get(ctx, expr1_0, expr2_0);
                             let expr4_0 = constructor_lower_shl128(ctx, expr0_0, expr3_0)?;
-                            return Some(expr4_0);
+                            let expr5_0 = C::output(ctx, expr4_0);
+                            return Some(expr5_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4144,7 +4180,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: usize = 0;
                             let expr3_0 = C::value_regs_get(ctx, expr1_0, expr2_0);
                             let expr4_0 = constructor_lower_ushr128(ctx, expr0_0, expr3_0)?;
-                            return Some(expr4_0);
+                            let expr5_0 = C::output(ctx, expr4_0);
+                            return Some(expr5_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -4154,7 +4191,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: usize = 0;
                             let expr3_0 = C::value_regs_get(ctx, expr1_0, expr2_0);
                             let expr4_0 = constructor_lower_sshr128(ctx, expr0_0, expr3_0)?;
-                            return Some(expr4_0);
+                            let expr5_0 = C::output(ctx, expr4_0);
+                            return Some(expr5_0);
                         }
                         _ => {}
                     }
@@ -4178,7 +4216,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr9_0 = C::zero_reg(ctx);
                             let expr10_0 = constructor_orr_not(ctx, expr8_0, expr9_0, expr4_0)?;
                             let expr11_0 = C::value_regs(ctx, expr7_0, expr10_0);
-                            return Some(expr11_0);
+                            let expr12_0 = C::output(ctx, expr11_0);
+                            return Some(expr12_0);
                         }
                         &Opcode::Bitrev => {
                             // Rule at src/isa/aarch64/lower.isle line 983.
@@ -4192,13 +4231,15 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr7_0 = C::value_regs_get(ctx, expr0_0, expr6_0);
                             let expr8_0 = constructor_rbit(ctx, expr5_0, expr7_0)?;
                             let expr9_0 = C::value_regs(ctx, expr8_0, expr4_0);
-                            return Some(expr9_0);
+                            let expr10_0 = C::output(ctx, expr9_0);
+                            return Some(expr10_0);
                         }
                         &Opcode::Clz => {
                             // Rule at src/isa/aarch64/lower.isle line 1001.
                             let expr0_0 = C::put_in_regs(ctx, pattern5_1);
                             let expr1_0 = constructor_lower_clz128(ctx, expr0_0)?;
-                            return Some(expr1_0);
+                            let expr2_0 = C::output(ctx, expr1_0);
+                            return Some(expr2_0);
                         }
                         &Opcode::Cls => {
                             // Rule at src/isa/aarch64/lower.isle line 1057.
@@ -4231,7 +4272,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr26_0: u64 = 0;
                             let expr27_0 = constructor_imm(ctx, expr25_0, expr26_0)?;
                             let expr28_0 = C::value_regs(ctx, expr24_0, expr27_0);
-                            return Some(expr28_0);
+                            let expr29_0 = C::output(ctx, expr28_0);
+                            return Some(expr29_0);
                         }
                         &Opcode::Ctz => {
                             // Rule at src/isa/aarch64/lower.isle line 1031.
@@ -4246,7 +4288,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = constructor_rbit(ctx, expr5_0, expr7_0)?;
                             let expr9_0 = C::value_regs(ctx, expr8_0, expr4_0);
                             let expr10_0 = constructor_lower_clz128(ctx, expr9_0)?;
-                            return Some(expr10_0);
+                            let expr11_0 = C::output(ctx, expr10_0);
+                            return Some(expr11_0);
                         }
                         &Opcode::Popcnt => {
                             // Rule at src/isa/aarch64/lower.isle line 1117.
@@ -4273,7 +4316,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr18_0: u64 = 0;
                             let expr19_0 = constructor_imm(ctx, expr17_0, expr18_0)?;
                             let expr20_0 = C::value_regs(ctx, expr16_0, expr19_0);
-                            return Some(expr20_0);
+                            let expr21_0 = C::output(ctx, expr20_0);
+                            return Some(expr21_0);
                         }
                         &Opcode::Uextend => {
                             if let Some(pattern7_0) = C::def_inst(ctx, pattern5_1) {
@@ -4300,7 +4344,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         let expr4_0: u64 = 0;
                                         let expr5_0 = constructor_imm(ctx, expr3_0, expr4_0)?;
                                         let expr6_0 = C::value_regs(ctx, expr2_0, expr5_0);
-                                        return Some(expr6_0);
+                                        let expr7_0 = C::output(ctx, expr6_0);
+                                        return Some(expr7_0);
                                     }
                                 }
                             }
@@ -4310,7 +4355,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: u64 = 0;
                             let expr3_0 = constructor_imm(ctx, expr1_0, expr2_0)?;
                             let expr4_0 = C::value_regs(ctx, expr0_0, expr3_0);
-                            return Some(expr4_0);
+                            let expr5_0 = C::output(ctx, expr4_0);
+                            return Some(expr5_0);
                         }
                         &Opcode::Sextend => {
                             if let Some(pattern7_0) = C::def_inst(ctx, pattern5_1) {
@@ -4341,7 +4387,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 ctx, expr3_0, expr2_0, expr5_0,
                                             )?;
                                             let expr7_0 = C::value_regs(ctx, expr2_0, expr6_0);
-                                            return Some(expr7_0);
+                                            let expr8_0 = C::output(ctx, expr7_0);
+                                            return Some(expr8_0);
                                         }
                                         if let Some(()) = C::not_i64x2(ctx, pattern11_0) {
                                             let pattern13_0 = C::u8_from_uimm8(ctx, pattern9_2);
@@ -4365,7 +4412,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 ctx, expr5_0, expr4_0, expr7_0,
                                             )?;
                                             let expr9_0 = C::value_regs(ctx, expr4_0, expr8_0);
-                                            return Some(expr9_0);
+                                            let expr10_0 = C::output(ctx, expr9_0);
+                                            return Some(expr10_0);
                                         }
                                     }
                                 }
@@ -4377,7 +4425,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0 = C::imm_shift_from_u8(ctx, expr2_0);
                             let expr4_0 = constructor_asr_imm(ctx, expr1_0, expr0_0, expr3_0)?;
                             let expr5_0 = C::value_regs(ctx, expr0_0, expr4_0);
-                            return Some(expr5_0);
+                            let expr6_0 = C::output(ctx, expr5_0);
+                            return Some(expr6_0);
                         }
                         _ => {}
                     }
@@ -4397,7 +4446,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                     let expr1_0 = VectorSize::Size8x16;
                     let expr2_0 = constructor_vec_cnt(ctx, expr0_0, &expr1_0)?;
-                    let expr3_0 = C::value_reg(ctx, expr2_0);
+                    let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                     return Some(expr3_0);
                 }
             }
@@ -4442,7 +4491,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull8(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4473,7 +4523,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull8(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4504,7 +4555,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull8(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4535,7 +4587,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull8(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4590,7 +4643,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull16(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4621,7 +4675,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull16(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4652,7 +4707,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull16(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4683,7 +4739,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull16(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4738,7 +4795,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull32(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4769,7 +4827,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_smull32(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4800,7 +4859,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull32(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4831,7 +4891,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                         let expr3_0 = constructor_umull32(
                                                             ctx, expr0_0, expr1_0, expr2_0,
                                                         )?;
-                                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                        let expr4_0 =
+                                                            constructor_output_reg(ctx, expr3_0)?;
                                                         return Some(expr4_0);
                                                     }
                                                 }
@@ -4860,7 +4921,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr13_0 = constructor_shll32(ctx, expr9_0, expr12_0)?;
                     let expr14_0: bool = false;
                     let expr15_0 = constructor_umlal32(ctx, expr13_0, expr11_0, expr7_0, expr14_0)?;
-                    let expr16_0 = C::value_reg(ctx, expr15_0);
+                    let expr16_0 = constructor_output_reg(ctx, expr15_0)?;
                     return Some(expr16_0);
                 }
             }
@@ -4874,7 +4935,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     // Rule at src/isa/aarch64/lower.isle line 22.
                     let expr0_0: u64 = 0;
                     let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                    let expr2_0 = C::value_reg(ctx, expr1_0);
+                    let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                     return Some(expr2_0);
                 }
             }
@@ -4886,7 +4947,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let pattern6_0 = C::u64_from_imm64(ctx, pattern4_1);
                     // Rule at src/isa/aarch64/lower.isle line 9.
                     let expr0_0 = constructor_imm(ctx, pattern2_0, pattern6_0)?;
-                    let expr1_0 = C::value_reg(ctx, expr0_0);
+                    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                     return Some(expr1_0);
                 }
             }
@@ -4899,14 +4960,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         // Rule at src/isa/aarch64/lower.isle line 17.
                         let expr0_0: u64 = 1;
                         let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     if pattern4_1 == false {
                         // Rule at src/isa/aarch64/lower.isle line 14.
                         let expr0_0: u64 = 0;
                         let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                 }
@@ -4920,21 +4981,21 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         // Rule at src/isa/aarch64/lower.isle line 989.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_rbit(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Clz => {
                         // Rule at src/isa/aarch64/lower.isle line 1004.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_a64_clz(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Cls => {
                         // Rule at src/isa/aarch64/lower.isle line 1071.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_a64_cls(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Ctz => {
@@ -4942,7 +5003,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_rbit(ctx, pattern2_0, expr0_0)?;
                         let expr2_0 = constructor_a64_clz(ctx, pattern2_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     _ => {}
@@ -4965,7 +5026,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                         let expr2_0 = constructor_vector_size(ctx, pattern2_0)?;
                         let expr3_0 = constructor_add_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     &Opcode::Isub => {
@@ -4975,7 +5036,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                         let expr2_0 = constructor_vector_size(ctx, pattern2_0)?;
                         let expr3_0 = constructor_sub_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     _ => {}
@@ -5015,7 +5076,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_small_rotr_imm(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -5029,7 +5090,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr3_0 = constructor_sub(ctx, expr0_0, expr1_0, expr2_0)?;
                         let expr4_0 = constructor_put_in_reg_zext32(ctx, pattern7_0)?;
                         let expr5_0 = constructor_small_rotr(ctx, pattern3_0, expr4_0, expr3_0)?;
-                        let expr6_0 = C::value_reg(ctx, expr5_0);
+                        let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                         return Some(expr6_0);
                     }
                     &Opcode::Rotr => {
@@ -5058,7 +5119,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 expr0_0,
                                                 pattern13_0,
                                             )?;
-                                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                             return Some(expr2_0);
                                         }
                                     }
@@ -5069,7 +5130,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_put_in_reg_zext32(ctx, pattern7_0)?;
                         let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                         let expr2_0 = constructor_small_rotr(ctx, pattern3_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     _ => {}
@@ -5095,7 +5156,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr5_0 = C::ty_bits(ctx, pattern3_0);
                         let expr6_0 = C::imm_shift_from_u8(ctx, expr5_0);
                         let expr7_0 = constructor_lsr_imm(ctx, expr4_0, expr3_0, expr6_0)?;
-                        let expr8_0 = C::value_reg(ctx, expr7_0);
+                        let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                         return Some(expr8_0);
                     }
                     &Opcode::Smulhi => {
@@ -5109,7 +5170,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr5_0 = C::ty_bits(ctx, pattern3_0);
                         let expr6_0 = C::imm_shift_from_u8(ctx, expr5_0);
                         let expr7_0 = constructor_asr_imm(ctx, expr4_0, expr3_0, expr6_0)?;
-                        let expr8_0 = C::value_reg(ctx, expr7_0);
+                        let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                         return Some(expr8_0);
                     }
                     &Opcode::Band => {
@@ -5119,7 +5180,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_alu_rs_imm_logic_commutative(
                             ctx, &expr0_0, pattern3_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Bor => {
@@ -5129,7 +5190,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_alu_rs_imm_logic_commutative(
                             ctx, &expr0_0, pattern3_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Bxor => {
@@ -5139,7 +5200,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_alu_rs_imm_logic_commutative(
                             ctx, &expr0_0, pattern3_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::BandNot => {
@@ -5149,7 +5210,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_alu_rs_imm_logic(
                             ctx, &expr0_0, pattern3_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::BorNot => {
@@ -5159,7 +5220,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_alu_rs_imm_logic(
                             ctx, &expr0_0, pattern3_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::BxorNot => {
@@ -5170,7 +5231,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr2_0 = constructor_alu_rs_imm_logic(
                             ctx, &expr0_0, expr1_0, pattern7_0, pattern7_1,
                         )?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Ishl => {
@@ -5180,7 +5241,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                         let expr2_0 =
                             constructor_do_shift(ctx, &expr0_0, pattern3_0, expr1_0, pattern7_1)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Ushr => {
@@ -5190,7 +5251,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_put_in_reg_zext32(ctx, pattern7_0)?;
                         let expr2_0 =
                             constructor_do_shift(ctx, &expr0_0, pattern3_0, expr1_0, pattern7_1)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Sshr => {
@@ -5200,7 +5261,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_put_in_reg_sext32(ctx, pattern7_0)?;
                         let expr2_0 =
                             constructor_do_shift(ctx, &expr0_0, pattern3_0, expr1_0, pattern7_1)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     _ => {}
@@ -5237,7 +5298,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                             if let Some(pattern13_0) =
@@ -5251,7 +5312,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                         }
@@ -5271,7 +5332,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr3_0 = constructor_madd(
                                                     ctx, pattern3_0, expr0_0, expr1_0, expr2_0,
                                                 )?;
-                                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                                 return Some(expr4_0);
                                             }
                                             &Opcode::Ishl => {
@@ -5316,7 +5377,9 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             pattern18_0,
                                                                         )?;
                                                                     let expr3_0 =
-                                                                        C::value_reg(ctx, expr2_0);
+                                                                        constructor_output_reg(
+                                                                            ctx, expr2_0,
+                                                                        )?;
                                                                     return Some(expr3_0);
                                                                 }
                                                             }
@@ -5336,7 +5399,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_add_extend(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_1) {
@@ -5359,7 +5422,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                             if let Some(pattern13_0) =
@@ -5373,7 +5436,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                         }
@@ -5393,7 +5456,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr3_0 = constructor_madd(
                                                     ctx, pattern3_0, expr0_0, expr1_0, expr2_0,
                                                 )?;
-                                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                                 return Some(expr4_0);
                                             }
                                             &Opcode::Ishl => {
@@ -5438,7 +5501,9 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             pattern18_0,
                                                                         )?;
                                                                     let expr3_0 =
-                                                                        C::value_reg(ctx, expr2_0);
+                                                                        constructor_output_reg(
+                                                                            ctx, expr2_0,
+                                                                        )?;
                                                                     return Some(expr3_0);
                                                                 }
                                                             }
@@ -5458,14 +5523,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_add_extend(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/aarch64/lower.isle line 30.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Isub => {
@@ -5490,7 +5555,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                             if let Some(pattern13_0) =
@@ -5504,7 +5569,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     expr0_0,
                                                     pattern13_0,
                                                 )?;
-                                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                                 return Some(expr2_0);
                                             }
                                         }
@@ -5550,7 +5615,9 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                         pattern18_0,
                                                                     )?;
                                                                 let expr3_0 =
-                                                                    C::value_reg(ctx, expr2_0);
+                                                                    constructor_output_reg(
+                                                                        ctx, expr2_0,
+                                                                    )?;
                                                                 return Some(expr3_0);
                                                             }
                                                         }
@@ -5568,14 +5635,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_sub_extend(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/aarch64/lower.isle line 101.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_sub(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imul => {
@@ -5586,7 +5653,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = C::zero_reg(ctx);
                             let expr3_0 =
                                 constructor_madd(ctx, pattern3_0, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Udiv => {
@@ -5596,7 +5663,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = constructor_put_in_reg_zext64(ctx, pattern7_0)?;
                             let expr2_0 = constructor_put_nonzero_in_reg_zext64(ctx, pattern7_1)?;
                             let expr3_0 = constructor_a64_udiv(ctx, expr0_0, expr1_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sdiv => {
@@ -5621,7 +5688,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr3_0 = constructor_a64_sdiv(
                                                 ctx, expr0_0, expr1_0, expr2_0,
                                             )?;
-                                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                             return Some(expr4_0);
                                         }
                                     }
@@ -5635,7 +5702,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             )?;
                             let expr3_0: Type = I64;
                             let expr4_0 = constructor_a64_sdiv(ctx, expr3_0, expr2_0, expr1_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Urem => {
@@ -5646,7 +5713,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: Type = I64;
                             let expr3_0 = constructor_a64_udiv(ctx, expr2_0, expr0_0, expr1_0)?;
                             let expr4_0 = constructor_msub64(ctx, expr3_0, expr1_0, expr0_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Srem => {
@@ -5657,7 +5724,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: Type = I64;
                             let expr3_0 = constructor_a64_sdiv(ctx, expr2_0, expr0_0, expr1_0)?;
                             let expr4_0 = constructor_msub64(ctx, expr3_0, expr1_0, expr0_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         _ => {}
@@ -5673,7 +5740,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::zero_reg(ctx);
                             let expr1_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr2_0 = constructor_sub(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bnot => {
@@ -5718,8 +5785,9 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                     expr1_0,
                                                                     pattern17_0,
                                                                 )?;
-                                                            let expr3_0 =
-                                                                C::value_reg(ctx, expr2_0);
+                                                            let expr3_0 = constructor_output_reg(
+                                                                ctx, expr2_0,
+                                                            )?;
                                                             return Some(expr3_0);
                                                         }
                                                     }
@@ -5733,7 +5801,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::zero_reg(ctx);
                             let expr1_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr2_0 = constructor_orr_not(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Uextend => {
@@ -5757,7 +5825,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             pattern12_0,
                                             &expr1_0,
                                         )?;
-                                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                         return Some(expr3_0);
                                     }
                                 }
@@ -5767,7 +5835,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 // Rule at src/isa/aarch64/lower.isle line 488.
                                 let expr0_0 = C::sink_atomic_load(ctx, &pattern8_0);
                                 let expr1_0 = constructor_load_acquire(ctx, pattern7_0, expr0_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/aarch64/lower.isle line 476.
@@ -5777,7 +5845,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0 = C::ty_bits(ctx, pattern3_0);
                             let expr4_0 =
                                 constructor_extend(ctx, expr0_0, expr1_0, expr2_0, expr3_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Sextend => {
@@ -5803,7 +5871,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             &expr1_0,
                                             &expr2_0,
                                         )?;
-                                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                         return Some(expr4_0);
                                     }
                                 }
@@ -5816,7 +5884,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0 = C::ty_bits(ctx, pattern3_0);
                             let expr4_0 =
                                 constructor_extend(ctx, expr0_0, expr1_0, expr2_0, expr3_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         _ => {}
@@ -5840,7 +5908,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_uqadd(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::SaddSat => {
@@ -5850,7 +5918,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_sqadd(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::UsubSat => {
@@ -5860,7 +5928,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_uqsub(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::SsubSat => {
@@ -5870,7 +5938,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_sqsub(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Band => {
@@ -5880,7 +5948,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_and_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Bor => {
@@ -5890,7 +5958,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_orr_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Bxor => {
@@ -5900,7 +5968,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_eor_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::BandNot => {
@@ -5910,7 +5978,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr3_0 = constructor_bic_vec(ctx, expr0_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ishl => {
@@ -5921,7 +5989,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_vec_dup(ctx, expr1_0, &expr0_0)?;
                             let expr3_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr4_0 = constructor_sshl(ctx, expr3_0, expr2_0, &expr0_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Ushr => {
@@ -5935,7 +6003,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr5_0 = constructor_vec_dup(ctx, expr4_0, &expr0_0)?;
                             let expr6_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr7_0 = constructor_ushl(ctx, expr6_0, expr5_0, &expr0_0)?;
-                            let expr8_0 = C::value_reg(ctx, expr7_0);
+                            let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         &Opcode::Sshr => {
@@ -5949,7 +6017,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr5_0 = constructor_vec_dup(ctx, expr4_0, &expr0_0)?;
                             let expr6_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr7_0 = constructor_sshl(ctx, expr6_0, expr5_0, &expr0_0)?;
-                            let expr8_0 = C::value_reg(ctx, expr7_0);
+                            let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         _ => {}
@@ -5965,7 +6033,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr1_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr2_0 = constructor_neg(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bnot => {
@@ -5973,7 +6041,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr1_0 = constructor_vector_size(ctx, pattern3_0)?;
                             let expr2_0 = constructor_not(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         _ => {}
@@ -5995,7 +6063,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = C::put_in_reg(ctx, pattern8_1);
                         let expr2_0 = constructor_vector_size(ctx, pattern3_0)?;
                         let expr3_0 = constructor_mul(ctx, expr0_0, expr1_0, &expr2_0)?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                 }
diff --git a/cranelift/codegen/src/isa/s390x/lower.isle b/cranelift/codegen/src/isa/s390x/lower.isle
index ed9af2fbcd..d60f1e4e63 100644
--- a/cranelift/codegen/src/isa/s390x/lower.isle
+++ b/cranelift/codegen/src/isa/s390x/lower.isle
@@ -2,12 +2,12 @@
 
 ;; The main lowering constructor term: takes a clif `Inst` and returns the
 ;; register(s) within which the lowered instruction's result values live.
-(decl lower (Inst) ValueRegs)
+(decl lower (Inst) InstOutput)
 
 ;; A variant of the main lowering constructor term, used for branches.
 ;; The only difference is that it gets an extra argument holding a vector
 ;; of branch targets to be used.
-(decl lower_branch (Inst VecMachLabel) ValueRegs)
+(decl lower_branch (Inst VecMachLabel) InstOutput)
 
 
 ;;;; Rules for `iconst` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -148,39 +148,39 @@
 ;; containing the carry result, but we do not support the `iflags` mechanism.
 ;; However, the only actual use case is where `iadd_ifcout` feeds into `trapif`,
 ;; which is implemented by explicitly matching on the flags producer.  So we can
-;; get away with just allocating a second temp so that the reg-renaming code
+;; get away with just using an invalid second output, and the reg-renaming code
 ;; does the right thing, for now.
-(decl value_regs_ifcout (Reg) ValueRegs)
-(rule (value_regs_ifcout reg)
-      (value_regs reg (writable_reg_to_reg (temp_writable_reg $I64))))
+(decl output_ifcout (Reg) InstOutput)
+(rule (output_ifcout reg)
+      (output_pair reg (value_regs_invalid)))
 
 ;; Add two registers.
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout x y)))
-      (value_regs_ifcout (add_logical_reg ty x y)))
+      (output_ifcout (add_logical_reg ty x y)))
 
 ;; Add a register and a zero-extended register.
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout x (zext32_value y))))
-      (value_regs_ifcout (add_logical_reg_zext32 ty x y)))
+      (output_ifcout (add_logical_reg_zext32 ty x y)))
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout (zext32_value x) y)))
-      (value_regs_ifcout (add_logical_reg_zext32 ty y x)))
+      (output_ifcout (add_logical_reg_zext32 ty y x)))
 
 ;; Add a register and an immediate.
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout x (u32_from_value y))))
-      (value_regs_ifcout (add_logical_zimm32 ty x y)))
+      (output_ifcout (add_logical_zimm32 ty x y)))
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout (u32_from_value x) y)))
-      (value_regs_ifcout (add_logical_zimm32 ty y x)))
+      (output_ifcout (add_logical_zimm32 ty y x)))
 
 ;; Add a register and memory (32/64-bit types).
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout x (sinkable_load_32_64 y))))
-      (value_regs_ifcout (add_logical_mem ty x (sink_load y))))
+      (output_ifcout (add_logical_mem ty x (sink_load y))))
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout (sinkable_load_32_64 x) y)))
-      (value_regs_ifcout (add_logical_mem ty y (sink_load x))))
+      (output_ifcout (add_logical_mem ty y (sink_load x))))
 
 ;; Add a register and zero-extended memory.
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout x (sinkable_uload32 y))))
-      (value_regs_ifcout (add_logical_mem_zext32 ty x (sink_uload32 y))))
+      (output_ifcout (add_logical_mem_zext32 ty x (sink_uload32 y))))
 (rule (lower (has_type (fits_in_64 ty) (iadd_ifcout (sinkable_uload32 x) y)))
-      (value_regs_ifcout (add_logical_mem_zext32 ty y (sink_uload32 x))))
+      (output_ifcout (add_logical_mem_zext32 ty y (sink_uload32 x))))
 
 
 ;;;; Rules for `ineg` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -1352,66 +1352,66 @@
 
 ;; Store 8-bit integer type, main lowering entry point.
 (rule (lower (store flags val @ (value_type $I8) addr offset))
-      (value_regs_none (istore8_impl flags val addr offset)))
+      (side_effect (istore8_impl flags val addr offset)))
 
 ;; Store 16-bit integer type, main lowering entry point.
 (rule (lower (store flags val @ (value_type $I16) addr offset))
-      (value_regs_none (istore16_impl flags val addr offset)))
+      (side_effect (istore16_impl flags val addr offset)))
 
 ;; Store 32-bit integer type, main lowering entry point.
 (rule (lower (store flags val @ (value_type $I32) addr offset))
-      (value_regs_none (istore32_impl flags val addr offset)))
+      (side_effect (istore32_impl flags val addr offset)))
 
 ;; Store 64-bit integer type, main lowering entry point.
 (rule (lower (store flags val @ (value_type $I64) addr offset))
-      (value_regs_none (istore64_impl flags val addr offset)))
+      (side_effect (istore64_impl flags val addr offset)))
 
 ;; Store 64-bit reference type, main lowering entry point.
 (rule (lower (store flags val @ (value_type $R64) addr offset))
-      (value_regs_none (istore64_impl flags val addr offset)))
+      (side_effect (istore64_impl flags val addr offset)))
 
 ;; Store 32-bit big-endian floating-point type.
 (rule (lower (store flags @ (bigendian)
                     val @ (value_type $F32) addr offset))
-      (value_regs_none (fpu_store32 (put_in_reg val)
-                                    (lower_address flags addr offset))))
+      (side_effect (fpu_store32 (put_in_reg val)
+                                (lower_address flags addr offset))))
 
 ;; Store 32-bit little-endian floating-point type (z15 instruction).
 (rule (lower (store flags @ (littleendian)
                     val @ (value_type (and $F32 (vxrs_ext2_enabled))) addr offset))
-      (value_regs_none (fpu_storerev32 (put_in_reg val)
-                                       (lower_address flags addr offset))))
+      (side_effect (fpu_storerev32 (put_in_reg val)
+                                   (lower_address flags addr offset))))
 
 ;; Store 32-bit little-endian floating-point type (via GPR on z14).
 (rule (lower (store flags @ (littleendian)
                     val @ (value_type (and $F32 (vxrs_ext2_disabled))) addr offset))
       (let ((gpr Reg (lshr_imm $I64 (mov_from_fpr (put_in_reg val)) 32)))
-        (value_regs_none (storerev32 gpr (lower_address flags addr offset)))))
+        (side_effect (storerev32 gpr (lower_address flags addr offset)))))
 
 ;; Store 64-bit big-endian floating-point type.
 (rule (lower (store flags @ (bigendian)
                     val @ (value_type $F64) addr offset))
-      (value_regs_none (fpu_store64 (put_in_reg val)
-                                    (lower_address flags addr offset))))
+      (side_effect (fpu_store64 (put_in_reg val)
+                                (lower_address flags addr offset))))
 
 ;; Store 64-bit little-endian floating-point type (z15 instruction).
 (rule (lower (store flags @ (littleendian)
                     val @ (value_type (and $F64 (vxrs_ext2_enabled))) addr offset))
-      (value_regs_none (fpu_storerev64 (put_in_reg val)
-                                       (lower_address flags addr offset))))
+      (side_effect (fpu_storerev64 (put_in_reg val)
+                                   (lower_address flags addr offset))))
 
 ;; Store 64-bit little-endian floating-point type (via GPR on z14).
 (rule (lower (store flags @ (littleendian)
                     val @ (value_type (and $F64 (vxrs_ext2_disabled))) addr offset))
       (let ((gpr Reg (mov_from_fpr (put_in_reg val))))
-        (value_regs_none (storerev64 gpr (lower_address flags addr offset)))))
+        (side_effect (storerev64 gpr (lower_address flags addr offset)))))
 
 
 ;;;; Rules for 8-bit integer stores ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;; Main `istore8` lowering entry point, dispatching to the helper.
 (rule (lower (istore8 flags val addr offset))
-      (value_regs_none (istore8_impl flags val addr offset)))
+      (side_effect (istore8_impl flags val addr offset)))
 
 ;; Helper to store 8-bit integer types.
 (decl istore8_impl (MemFlags Value Value Offset32) SideEffectNoResult)
@@ -1429,7 +1429,7 @@
 
 ;; Main `istore16` lowering entry point, dispatching to the helper.
 (rule (lower (istore16 flags val addr offset))
-      (value_regs_none (istore16_impl flags val addr offset)))
+      (side_effect (istore16_impl flags val addr offset)))
 
 ;; Helper to store 16-bit integer types.
 (decl istore16_impl (MemFlags Value Value Offset32) SideEffectNoResult)
@@ -1455,7 +1455,7 @@
 
 ;; Main `istore32` lowering entry point, dispatching to the helper.
 (rule (lower (istore32 flags val addr offset))
-      (value_regs_none (istore32_impl flags val addr offset)))
+      (side_effect (istore32_impl flags val addr offset)))
 
 ;; Helper to store 32-bit integer types.
 (decl istore32_impl (MemFlags Value Value Offset32) SideEffectNoResult)
@@ -1854,10 +1854,10 @@
 ;;;; Rules for `atomic_store` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ;; Atomic stores can be implemented via regular stores followed by a fence.
-(decl atomic_store_impl (SideEffectNoResult) ValueRegs)
+(decl atomic_store_impl (SideEffectNoResult) InstOutput)
 (rule (atomic_store_impl store)
-      (let ((_ ValueRegs (value_regs_none store)))
-         (value_regs_none (fence_impl))))
+      (let ((_ InstOutput (side_effect store)))
+         (side_effect (fence_impl))))
 
 ;; 8-bit atomic store.
 (rule (lower (atomic_store flags val @ (value_type $I8) addr))
@@ -1880,7 +1880,7 @@
 
 ;; Fence to ensure sequential consistency.
 (rule (lower (fence))
-      (value_regs_none (fence_impl)))
+      (side_effect (fence_impl)))
 
 
 ;;;; Rules for `icmp` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2066,7 +2066,7 @@
 ;; Unconditional branch.  The target is found as first (and only) element in
 ;; the list of the current block's branch targets passed as `targets`.
 (rule (lower_branch (jump _ _) targets)
-      (value_regs_none (jump_impl (vec_element targets 0))))
+      (side_effect (jump_impl (vec_element targets 0))))
 
 
 ;;;; Rules for `br_table` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2082,8 +2082,8 @@
             (cond ProducesBool
               (bool (icmpu_uimm32 $I64 idx (vec_length_minus1 targets))
                     (intcc_as_cond (IntCC.UnsignedGreaterThanOrEqual))))
-            (_ ValueRegs (value_regs_none (oneway_cond_br_bool cond
-                                            (vec_element targets 0)))))
+            (_ InstOutput (side_effect (oneway_cond_br_bool cond
+                                         (vec_element targets 0)))))
         ;; Scale the index by the element size, and then emit the
         ;; compound instruction that does:
         ;;
@@ -2098,7 +2098,7 @@
         ;; PC-rel offset to the jumptable would be incorrect.
         ;; (The alternative is to introduce a relocation pass
         ;; for inlined jumptables, which is much worse, IMHO.)
-        (value_regs_none (jt_sequence (lshl_imm $I64 idx 2) targets))))
+        (side_effect (jt_sequence (lshl_imm $I64 idx 2) targets))))
 
 
 ;;;; Rules for `brz` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2107,9 +2107,9 @@
 ;; - element 0: target if the condition is true (i.e. value is zero)
 ;; - element 1: target if the condition is false (i.e. value is nonzero)
 (rule (lower_branch (brz val_cond _ _) targets)
-      (value_regs_none (cond_br_bool (invert_bool (value_nonzero val_cond))
-                                     (vec_element targets 0)
-                                     (vec_element targets 1))))
+      (side_effect (cond_br_bool (invert_bool (value_nonzero val_cond))
+                                 (vec_element targets 0)
+                                 (vec_element targets 1))))
 
 
 ;;;; Rules for `brnz` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2118,9 +2118,9 @@
 ;; - element 0: target if the condition is true (i.e. value is nonzero)
 ;; - element 1: target if the condition is false (i.e. value is zero)
 (rule (lower_branch (brnz val_cond _ _) targets)
-      (value_regs_none (cond_br_bool (value_nonzero val_cond)
-                                     (vec_element targets 0)
-                                     (vec_element targets 1))))
+      (side_effect (cond_br_bool (value_nonzero val_cond)
+                                 (vec_element targets 0)
+                                 (vec_element targets 1))))
 
 
 ;;;; Rules for `brif` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2129,9 +2129,9 @@
 ;; generated by common code here.  Others will fail to lower.
 
 (rule (lower_branch (brif int_cc (ifcmp x y) _ _) targets)
-      (value_regs_none (cond_br_bool (icmp_val $false int_cc x y)
-                                     (vec_element targets 0)
-                                     (vec_element targets 1))))
+      (side_effect (cond_br_bool (icmp_val $false int_cc x y)
+                                 (vec_element targets 0)
+                                 (vec_element targets 1))))
 
 
 ;;;; Rules for `trap` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2167,7 +2167,7 @@
 ;;;; Rules for `debugtrap` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (rule (lower (debugtrap))
-      (value_regs_none (debugtrap_impl)))
+      (side_effect (debugtrap_impl)))
 
 
 ;;;; Rules for `trapif` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -2205,6 +2205,6 @@
 
 (rule (lower (trapif (IntCC.UnsignedGreaterThan)
                      (iadd_ifcout x y) trap_code))
-      (value_regs_none (trap_if_impl (mask_as_cond 3) trap_code)))
+      (side_effect (trap_if_impl (mask_as_cond 3) trap_code)))
 
 
diff --git a/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest b/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest
index 7a3dec4b1b..8fc14e1cbb 100644
--- a/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest
+++ b/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest
@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 8bf92e18323e7041
+src/prelude.isle 957023853b23dacb
 src/isa/s390x/inst.isle d91a16074ab186a8
-src/isa/s390x/lower.isle 5626c0ef61594d61
+src/isa/s390x/lower.isle 1cc5a12adc8c75f9
diff --git a/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.rs b/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.rs
index 8fbd651ada..77ef5db1df 100644
--- a/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.rs
+++ b/cranelift/codegen/src/isa/s390x/lower/isle/generated_code.rs
@@ -25,6 +25,12 @@ pub trait Context {
     fn value_reg(&mut self, arg0: Reg) -> ValueRegs;
     fn value_regs(&mut self, arg0: Reg, arg1: Reg) -> ValueRegs;
     fn value_regs_invalid(&mut self) -> ValueRegs;
+    fn output_none(&mut self) -> InstOutput;
+    fn output(&mut self, arg0: ValueRegs) -> InstOutput;
+    fn output_pair(&mut self, arg0: ValueRegs, arg1: ValueRegs) -> InstOutput;
+    fn output_builder_new(&mut self) -> InstOutputBuilder;
+    fn output_builder_push(&mut self, arg0: &InstOutputBuilder, arg1: ValueRegs) -> Unit;
+    fn output_builder_finish(&mut self, arg0: &InstOutputBuilder) -> InstOutput;
     fn temp_writable_reg(&mut self, arg0: Type) -> WritableReg;
     fn invalid_reg(&mut self) -> Reg;
     fn put_in_reg(&mut self, arg0: Value) -> Reg;
@@ -136,13 +142,13 @@ pub trait Context {
     fn same_reg(&mut self, arg0: Reg, arg1: WritableReg) -> Option<()>;
 }
 
-/// Internal type SideEffectNoResult: defined at src/prelude.isle line 308.
+/// Internal type SideEffectNoResult: defined at src/prelude.isle line 345.
 #[derive(Clone, Debug)]
 pub enum SideEffectNoResult {
     Inst { inst: MInst },
 }
 
-/// Internal type ProducesFlags: defined at src/prelude.isle line 330.
+/// Internal type ProducesFlags: defined at src/prelude.isle line 367.
 #[derive(Clone, Debug)]
 pub enum ProducesFlags {
     ProducesFlagsSideEffect { inst: MInst },
@@ -150,7 +156,7 @@ pub enum ProducesFlags {
     ProducesFlagsReturnsResultWithConsumer { inst: MInst, result: Reg },
 }
 
-/// Internal type ConsumesFlags: defined at src/prelude.isle line 341.
+/// Internal type ConsumesFlags: defined at src/prelude.isle line 378.
 #[derive(Clone, Debug)]
 pub enum ConsumesFlags {
     ConsumesFlagsReturnsResultWithProducer {
@@ -886,10 +892,28 @@ pub enum ProducesBool {
     ProducesBool { producer: ProducesFlags, cond: Cond },
 }
 
+// Generated as internal constructor for term output_reg.
+pub fn constructor_output_reg<C: Context>(ctx: &mut C, arg0: Reg) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 86.
+    let expr0_0 = C::value_reg(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
+// Generated as internal constructor for term output_value.
+pub fn constructor_output_value<C: Context>(ctx: &mut C, arg0: Value) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 90.
+    let expr0_0 = C::put_in_regs(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
 // Generated as internal constructor for term temp_reg.
 pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 73.
+    // Rule at src/prelude.isle line 110.
     let expr0_0 = C::temp_writable_reg(ctx, pattern0_0);
     let expr1_0 = C::writable_reg_to_reg(ctx, expr0_0);
     return Some(expr1_0);
@@ -898,26 +922,26 @@ pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg>
 // Generated as internal constructor for term lo_reg.
 pub fn constructor_lo_reg<C: Context>(ctx: &mut C, arg0: Value) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 108.
+    // Rule at src/prelude.isle line 145.
     let expr0_0 = C::put_in_regs(ctx, pattern0_0);
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
     return Some(expr2_0);
 }
 
-// Generated as internal constructor for term value_regs_none.
-pub fn constructor_value_regs_none<C: Context>(
+// Generated as internal constructor for term side_effect.
+pub fn constructor_side_effect<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 313.
+        // Rule at src/prelude.isle line 350.
         let expr0_0 = C::emit(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -927,15 +951,15 @@ pub fn constructor_value_regs_none<C: Context>(
 pub fn constructor_safepoint<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 319.
+        // Rule at src/prelude.isle line 356.
         let expr0_0 = C::emit_safepoint(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -959,7 +983,7 @@ pub fn constructor_consumes_flags_concat<C: Context>(
             result: pattern3_1,
         } = pattern2_0
         {
-            // Rule at src/prelude.isle line 353.
+            // Rule at src/prelude.isle line 390.
             let expr0_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
             let expr1_0 = ConsumesFlags::ConsumesFlagsTwiceReturnsValueRegs {
                 inst1: pattern1_0.clone(),
@@ -989,7 +1013,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst: ref pattern3_0,
                     result: pattern3_1,
                 } => {
-                    // Rule at src/prelude.isle line 378.
+                    // Rule at src/prelude.isle line 415.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_0);
                     let expr2_0 = C::value_reg(ctx, pattern3_1);
@@ -1000,7 +1024,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst2: ref pattern3_1,
                     result: pattern3_2,
                 } => {
-                    // Rule at src/prelude.isle line 384.
+                    // Rule at src/prelude.isle line 421.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_1);
                     let expr2_0 = C::emit(ctx, pattern3_0);
@@ -1019,7 +1043,7 @@ pub fn constructor_with_flags<C: Context>(
                 result: pattern3_1,
             } = pattern2_0
             {
-                // Rule at src/prelude.isle line 372.
+                // Rule at src/prelude.isle line 409.
                 let expr0_0 = C::emit(ctx, pattern1_0);
                 let expr1_0 = C::emit(ctx, pattern3_0);
                 let expr2_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
@@ -1039,7 +1063,7 @@ pub fn constructor_with_flags_reg<C: Context>(
 ) -> Option<Reg> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/prelude.isle line 397.
+    // Rule at src/prelude.isle line 434.
     let expr0_0 = constructor_with_flags(ctx, pattern0_0, pattern1_0)?;
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -7877,7 +7901,7 @@ pub fn constructor_fcmp_reg<C: Context>(
 }
 
 // Generated as internal constructor for term lower.
-pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueRegs> {
+pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     let pattern1_0 = C::inst_data(ctx, pattern0_0);
     match &pattern1_0 {
@@ -7888,19 +7912,19 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 &Opcode::Debugtrap => {
                     // Rule at src/isa/s390x/lower.isle line 2169.
                     let expr0_0 = constructor_debugtrap_impl(ctx)?;
-                    let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                    let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 &Opcode::Nop => {
                     // Rule at src/isa/s390x/lower.isle line 47.
                     let expr0_0 = C::invalid_reg(ctx);
-                    let expr1_0 = C::value_reg(ctx, expr0_0);
+                    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                     return Some(expr1_0);
                 }
                 &Opcode::Fence => {
                     // Rule at src/isa/s390x/lower.isle line 1882.
                     let expr0_0 = constructor_fence_impl(ctx)?;
-                    let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                    let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 _ => {}
@@ -7918,13 +7942,13 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr1_0 = C::memflags_trusted(ctx);
                     let expr2_0 = C::memarg_symbol(ctx, pattern4_1, expr0_0, expr1_0);
                     let expr3_0 = constructor_load_addr(ctx, &expr2_0)?;
-                    let expr4_0 = C::value_reg(ctx, expr3_0);
+                    let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                     return Some(expr4_0);
                 }
                 // Rule at src/isa/s390x/lower.isle line 1163.
                 let expr0_0: i64 = 0;
                 let expr1_0 = constructor_load_ext_name_far(ctx, pattern4_1, expr0_0)?;
-                let expr2_0 = C::value_reg(ctx, expr1_0);
+                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                 return Some(expr2_0);
             }
         }
@@ -7945,13 +7969,13 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::memflags_trusted(ctx);
                             let expr1_0 = C::memarg_symbol(ctx, pattern4_0, pattern7_0, expr0_0);
                             let expr2_0 = constructor_load_addr(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                     }
                     // Rule at src/isa/s390x/lower.isle line 1175.
                     let expr0_0 = constructor_load_ext_name_far(ctx, pattern4_0, pattern4_2)?;
-                    let expr1_0 = C::value_reg(ctx, expr0_0);
+                    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                     return Some(expr1_0);
                 }
             }
@@ -7965,7 +7989,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 // Rule at src/isa/s390x/lower.isle line 29.
                 let expr0_0: Type = F32;
                 let expr1_0 = constructor_imm(ctx, expr0_0, pattern4_0)?;
-                let expr2_0 = C::value_reg(ctx, expr1_0);
+                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                 return Some(expr2_0);
             }
         }
@@ -7978,7 +8002,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 // Rule at src/isa/s390x/lower.isle line 35.
                 let expr0_0: Type = F64;
                 let expr1_0 = constructor_imm(ctx, expr0_0, pattern4_0)?;
-                let expr2_0 = C::value_reg(ctx, expr1_0);
+                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                 return Some(expr2_0);
             }
         }
@@ -8062,7 +8086,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_istore8_impl(
                             ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                         )?;
-                        let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                        let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                         return Some(expr1_0);
                     }
                     if pattern5_0 == I16 {
@@ -8070,7 +8094,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_istore16_impl(
                             ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                         )?;
-                        let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                        let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                         return Some(expr1_0);
                     }
                     if pattern5_0 == I32 {
@@ -8078,7 +8102,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_istore32_impl(
                             ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                         )?;
-                        let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                        let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                         return Some(expr1_0);
                     }
                     if pattern5_0 == I64 {
@@ -8086,7 +8110,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_istore64_impl(
                             ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                         )?;
-                        let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                        let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                         return Some(expr1_0);
                     }
                     if pattern5_0 == R64 {
@@ -8094,7 +8118,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = constructor_istore64_impl(
                             ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                         )?;
-                        let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                        let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                         return Some(expr1_0);
                     }
                     if pattern5_0 == F32 {
@@ -8104,7 +8128,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern2_2, pattern4_1, pattern2_3)?;
                             let expr2_0 = constructor_fpu_store32(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                            let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                             return Some(expr3_0);
                         }
                         if let Some(()) = C::vxrs_ext2_enabled(ctx, pattern5_0) {
@@ -8115,7 +8139,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern2_2, pattern4_1, pattern2_3,
                                 )?;
                                 let expr2_0 = constructor_fpu_storerev32(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                                let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -8131,7 +8155,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern2_2, pattern4_1, pattern2_3,
                                 )?;
                                 let expr6_0 = constructor_storerev32(ctx, expr4_0, &expr5_0)?;
-                                let expr7_0 = constructor_value_regs_none(ctx, &expr6_0)?;
+                                let expr7_0 = constructor_side_effect(ctx, &expr6_0)?;
                                 return Some(expr7_0);
                             }
                         }
@@ -8143,7 +8167,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern2_2, pattern4_1, pattern2_3)?;
                             let expr2_0 = constructor_fpu_store64(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                            let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                             return Some(expr3_0);
                         }
                         if let Some(()) = C::vxrs_ext2_enabled(ctx, pattern5_0) {
@@ -8154,7 +8178,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern2_2, pattern4_1, pattern2_3,
                                 )?;
                                 let expr2_0 = constructor_fpu_storerev64(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                                let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -8167,7 +8191,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern2_2, pattern4_1, pattern2_3,
                                 )?;
                                 let expr3_0 = constructor_storerev64(ctx, expr1_0, &expr2_0)?;
-                                let expr4_0 = constructor_value_regs_none(ctx, &expr3_0)?;
+                                let expr4_0 = constructor_side_effect(ctx, &expr3_0)?;
                                 return Some(expr4_0);
                             }
                         }
@@ -8179,7 +8203,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr0_0 = constructor_istore8_impl(
                         ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                     )?;
-                    let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                    let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 &Opcode::Istore16 => {
@@ -8188,7 +8212,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr0_0 = constructor_istore16_impl(
                         ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                     )?;
-                    let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                    let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 &Opcode::Istore32 => {
@@ -8197,7 +8221,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr0_0 = constructor_istore32_impl(
                         ctx, pattern2_2, pattern4_0, pattern4_1, pattern2_3,
                     )?;
-                    let expr1_0 = constructor_value_regs_none(ctx, &expr0_0)?;
+                    let expr1_0 = constructor_side_effect(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 _ => {}
@@ -8210,17 +8234,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             match pattern2_0 {
                 &Opcode::Copy => {
                     // Rule at src/isa/s390x/lower.isle line 53.
-                    let expr0_0 = C::put_in_regs(ctx, pattern2_1);
+                    let expr0_0 = constructor_output_value(ctx, pattern2_1)?;
                     return Some(expr0_0);
                 }
                 &Opcode::Breduce => {
                     // Rule at src/isa/s390x/lower.isle line 752.
-                    let expr0_0 = C::put_in_regs(ctx, pattern2_1);
+                    let expr0_0 = constructor_output_value(ctx, pattern2_1)?;
                     return Some(expr0_0);
                 }
                 &Opcode::Ireduce => {
                     // Rule at src/isa/s390x/lower.isle line 596.
-                    let expr0_0 = C::put_in_regs(ctx, pattern2_1);
+                    let expr0_0 = constructor_output_value(ctx, pattern2_1)?;
                     return Some(expr0_0);
                 }
                 _ => {}
@@ -8262,7 +8286,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr1_0 = C::mask_as_cond(ctx, expr0_0);
                                     let expr2_0 =
                                         constructor_trap_if_impl(ctx, &expr1_0, pattern2_3)?;
-                                    let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                                    let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
@@ -8328,7 +8352,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 = C::intcc_as_cond(ctx, &expr5_0);
                             let expr7_0 = constructor_bool(ctx, &expr4_0, &expr6_0)?;
                             let expr8_0 = constructor_lower_bool(ctx, expr0_0, &expr7_0)?;
-                            let expr9_0 = C::value_reg(ctx, expr8_0);
+                            let expr9_0 = constructor_output_reg(ctx, expr8_0)?;
                             return Some(expr9_0);
                         }
                     }
@@ -8345,7 +8369,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 = C::intcc_as_cond(ctx, &expr5_0);
                             let expr7_0 = constructor_bool(ctx, &expr4_0, &expr6_0)?;
                             let expr8_0 = constructor_lower_bool(ctx, expr0_0, &expr7_0)?;
-                            let expr9_0 = C::value_reg(ctx, expr8_0);
+                            let expr9_0 = constructor_output_reg(ctx, expr8_0)?;
                             return Some(expr9_0);
                         }
                     }
@@ -8364,7 +8388,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         // Rule at src/isa/s390x/lower.isle line 884.
                         let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                         let expr1_0 = constructor_popcnt_byte(ctx, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                 }
@@ -8380,7 +8404,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr2_0 =
                             constructor_lower_address(ctx, pattern5_2, pattern5_1, expr1_0)?;
                         let expr3_0 = constructor_zext32_mem(ctx, expr0_0, &expr2_0)?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                 }
@@ -8396,7 +8420,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 =
                             constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                         let expr2_0 = constructor_zext32_mem(ctx, expr0_0, &expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                 }
@@ -8418,7 +8442,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr0_0)?;
                             let expr2_0 = constructor_loadrev16(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8428,7 +8452,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr1_0)?;
                             let expr3_0 = constructor_zext32_mem(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                     }
@@ -8445,7 +8469,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_loadrev16(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8454,7 +8478,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr2_0 = constructor_zext32_mem(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                     }
@@ -8480,7 +8504,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I64;
                             let expr5_0: u8 = 32;
                             let expr6_0 = constructor_lshr_imm(ctx, expr4_0, expr3_0, expr5_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         &Opcode::Smulhi => {
@@ -8493,7 +8517,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I64;
                             let expr5_0: u8 = 32;
                             let expr6_0 = constructor_ashr_imm(ctx, expr4_0, expr3_0, expr5_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         _ => {}
@@ -8512,7 +8536,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_mov_from_fpr(ctx, expr1_0)?;
                             let expr3_0: u8 = 32;
                             let expr4_0 = constructor_lshr_imm(ctx, expr0_0, expr2_0, expr3_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                     }
@@ -8529,7 +8553,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr0_0)?;
                             let expr2_0 = constructor_loadrev32(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8538,7 +8562,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr0_0)?;
                             let expr2_0 = constructor_load32(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                     }
@@ -8555,7 +8579,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_loadrev32(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8563,7 +8587,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_load32(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8588,7 +8612,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0: Type = I64;
                             let expr4_0 = constructor_regpair_hi(ctx, &expr2_0)?;
                             let expr5_0 = constructor_copy_reg(ctx, expr3_0, expr4_0)?;
-                            let expr6_0 = C::value_reg(ctx, expr5_0);
+                            let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         &Opcode::Smulhi => {
@@ -8600,7 +8624,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0: Type = I64;
                             let expr4_0 = constructor_regpair_hi(ctx, &expr2_0)?;
                             let expr5_0 = constructor_copy_reg(ctx, expr3_0, expr4_0)?;
-                            let expr6_0 = C::value_reg(ctx, expr5_0);
+                            let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         _ => {}
@@ -8616,7 +8640,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             // Rule at src/isa/s390x/lower.isle line 1135.
                             let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr1_0 = constructor_mov_from_fpr(ctx, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8633,7 +8657,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr0_0)?;
                             let expr2_0 = constructor_loadrev64(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8642,7 +8666,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, expr0_0)?;
                             let expr2_0 = constructor_load64(ctx, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                     }
@@ -8659,7 +8683,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_loadrev64(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8667,7 +8691,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_load64(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8690,7 +8714,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 =
                             constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                         let expr1_0 = constructor_loadrev64(ctx, &expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -8698,7 +8722,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 =
                             constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                         let expr1_0 = constructor_load64(ctx, &expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                 }
@@ -8720,7 +8744,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0: u8 = 32;
                             let expr3_0 = constructor_lshl_imm(ctx, expr0_0, expr1_0, expr2_0)?;
                             let expr4_0 = constructor_mov_to_fpr(ctx, expr3_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                     }
@@ -8737,7 +8761,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_fpu_load32(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8758,7 +8782,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             // Rule at src/isa/s390x/lower.isle line 1131.
                             let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr1_0 = constructor_mov_to_fpr(ctx, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8775,7 +8799,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr1_0 = constructor_fpu_load64(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -8792,7 +8816,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     // Rule at src/isa/s390x/lower.isle line 41.
                     let expr0_0: u64 = 0;
                     let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                    let expr2_0 = C::value_reg(ctx, expr1_0);
+                    let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                     return Some(expr2_0);
                 }
             }
@@ -8804,7 +8828,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let pattern6_0 = C::u64_from_imm64(ctx, pattern4_1);
                     // Rule at src/isa/s390x/lower.isle line 15.
                     let expr0_0 = constructor_imm(ctx, pattern2_0, pattern6_0)?;
-                    let expr1_0 = C::value_reg(ctx, expr0_0);
+                    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                     return Some(expr1_0);
                 }
             }
@@ -8817,7 +8841,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     // Rule at src/isa/s390x/lower.isle line 1152.
                     let expr0_0 =
                         constructor_stack_addr_impl(ctx, pattern2_0, pattern4_1, pattern4_2)?;
-                    let expr1_0 = C::value_reg(ctx, expr0_0);
+                    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                     return Some(expr1_0);
                 }
             }
@@ -8830,14 +8854,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         // Rule at src/isa/s390x/lower.isle line 23.
                         let expr0_0: u64 = 1;
                         let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     if pattern4_1 == false {
                         // Rule at src/isa/s390x/lower.isle line 21.
                         let expr0_0: u64 = 0;
                         let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                 }
@@ -8853,7 +8877,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fadd_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fsub => {
@@ -8862,7 +8886,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fsub_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fmul => {
@@ -8871,7 +8895,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fmul_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fdiv => {
@@ -8880,7 +8904,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fdiv_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fcopysign => {
@@ -8889,7 +8913,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fpu_copysign(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fmin => {
@@ -8898,7 +8922,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fmin_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::Fmax => {
@@ -8907,7 +8931,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern6_0);
                         let expr1_0 = C::put_in_reg(ctx, pattern6_1);
                         let expr2_0 = constructor_fmax_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     _ => {}
@@ -8923,7 +8947,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     // Rule at src/isa/s390x/lower.isle line 2004.
                     let expr0_0 = constructor_fcmp_val(ctx, pattern4_2, pattern6_0, pattern6_1)?;
                     let expr1_0 = constructor_lower_bool(ctx, pattern2_0, &expr0_0)?;
-                    let expr2_0 = C::value_reg(ctx, expr1_0);
+                    let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                     return Some(expr2_0);
                 }
             }
@@ -8939,7 +8963,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr1_0 =
                         constructor_icmp_val(ctx, expr0_0, pattern4_2, pattern6_0, pattern6_1)?;
                     let expr2_0 = constructor_lower_bool(ctx, pattern2_0, &expr1_0)?;
-                    let expr3_0 = C::value_reg(ctx, expr2_0);
+                    let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                     return Some(expr3_0);
                 }
             }
@@ -8958,7 +8982,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr3_0 = constructor_select_bool_reg(
                             ctx, pattern2_0, &expr0_0, expr1_0, expr2_0,
                         )?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     &Opcode::Fma => {
@@ -8970,7 +8994,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr2_0 = C::put_in_reg(ctx, pattern6_2);
                         let expr3_0 =
                             constructor_fma_reg(ctx, pattern2_0, expr0_0, expr1_0, expr2_0)?;
-                        let expr4_0 = C::value_reg(ctx, expr3_0);
+                        let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     _ => {}
@@ -9008,7 +9032,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr4_0 = constructor_select_bool_reg(
                                     ctx, pattern2_0, &expr1_0, expr2_0, expr3_0,
                                 )?;
-                                let expr5_0 = C::value_reg(ctx, expr4_0);
+                                let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                                 return Some(expr5_0);
                             }
                         }
@@ -9024,61 +9048,61 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         // Rule at src/isa/s390x/lower.isle line 976.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_sqrt_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Fneg => {
                         // Rule at src/isa/s390x/lower.isle line 983.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_fneg_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Fabs => {
                         // Rule at src/isa/s390x/lower.isle line 990.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_fabs_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Ceil => {
                         // Rule at src/isa/s390x/lower.isle line 997.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_ceil_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Floor => {
                         // Rule at src/isa/s390x/lower.isle line 1004.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_floor_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Trunc => {
                         // Rule at src/isa/s390x/lower.isle line 1011.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_trunc_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Nearest => {
                         // Rule at src/isa/s390x/lower.isle line 1018.
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 = constructor_nearest_reg(ctx, pattern2_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Bextend => {
                         // Rule at src/isa/s390x/lower.isle line 760.
                         let expr0_0 = constructor_cast_bool(ctx, pattern2_0, pattern4_1)?;
-                        let expr1_0 = C::value_reg(ctx, expr0_0);
+                        let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                         return Some(expr1_0);
                     }
                     &Opcode::Bmask => {
                         // Rule at src/isa/s390x/lower.isle line 762.
                         let expr0_0 = constructor_cast_bool(ctx, pattern2_0, pattern4_1)?;
-                        let expr1_0 = C::value_reg(ctx, expr0_0);
+                        let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                         return Some(expr1_0);
                     }
                     &Opcode::Fpromote => {
@@ -9087,7 +9111,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 =
                             constructor_fpromote_reg(ctx, pattern2_0, pattern6_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::Fdemote => {
@@ -9096,7 +9120,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr0_0 = C::put_in_reg(ctx, pattern4_1);
                         let expr1_0 =
                             constructor_fdemote_reg(ctx, pattern2_0, pattern6_0, expr0_0)?;
-                        let expr2_0 = C::value_reg(ctx, expr1_0);
+                        let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                         return Some(expr2_0);
                     }
                     &Opcode::FcvtFromUint => {
@@ -9106,7 +9130,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_put_in_reg_zext32(ctx, pattern4_1)?;
                         let expr2_0 =
                             constructor_fcvt_from_uint_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     &Opcode::FcvtFromSint => {
@@ -9116,7 +9140,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr1_0 = constructor_put_in_reg_sext32(ctx, pattern4_1)?;
                         let expr2_0 =
                             constructor_fcvt_from_sint_reg(ctx, pattern2_0, expr0_0, expr1_0)?;
-                        let expr3_0 = C::value_reg(ctx, expr2_0);
+                        let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                         return Some(expr3_0);
                     }
                     _ => {}
@@ -9141,7 +9165,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern8_1);
                                 let expr2_0 =
                                     constructor_and_not_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::BorNot => {
@@ -9152,7 +9176,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern8_1);
                                 let expr2_0 =
                                     constructor_or_not_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::BxorNot => {
@@ -9163,7 +9187,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern8_1);
                                 let expr2_0 =
                                     constructor_xor_not_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             _ => {}
@@ -9184,7 +9208,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0 =
                                 constructor_and_not_reg(ctx, pattern4_0, expr3_0, expr0_0)?;
                             let expr5_0 = constructor_or_reg(ctx, pattern4_0, expr4_0, expr2_0)?;
-                            let expr6_0 = C::value_reg(ctx, expr5_0);
+                            let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                     }
@@ -9198,14 +9222,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern6_1);
                                 let expr1_0 =
                                     constructor_or_not_reg(ctx, pattern4_0, expr0_0, expr0_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             &Opcode::Popcnt => {
                                 // Rule at src/isa/s390x/lower.isle line 889.
                                 let expr0_0 = constructor_put_in_reg_zext64(ctx, pattern6_1)?;
                                 let expr1_0 = constructor_popcnt_reg(ctx, expr0_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             _ => {}
@@ -9235,7 +9259,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0: Type = I32;
                         let expr8_0: u8 = 8;
                         let expr9_0 = constructor_lshr_imm(ctx, expr7_0, expr6_0, expr8_0)?;
-                        let expr10_0 = C::value_reg(ctx, expr9_0);
+                        let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                         return Some(expr10_0);
                     }
                 }
@@ -9264,7 +9288,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr12_0: Type = I32;
                         let expr13_0: u8 = 24;
                         let expr14_0 = constructor_lshr_imm(ctx, expr12_0, expr11_0, expr13_0)?;
-                        let expr15_0 = C::value_reg(ctx, expr14_0);
+                        let expr15_0 = constructor_output_reg(ctx, expr14_0)?;
                         return Some(expr15_0);
                     }
                 }
@@ -9298,7 +9322,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr17_0: Type = I64;
                         let expr18_0: u8 = 56;
                         let expr19_0 = constructor_lshr_imm(ctx, expr17_0, expr16_0, expr18_0)?;
-                        let expr20_0 = C::value_reg(ctx, expr19_0);
+                        let expr20_0 = constructor_output_reg(ctx, expr19_0)?;
                         return Some(expr20_0);
                     }
                 }
@@ -9320,7 +9344,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr2_0 =
                                     constructor_and_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
                                 let expr3_0 = constructor_not_reg(ctx, pattern4_0, expr2_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             &Opcode::BorNot => {
@@ -9332,7 +9356,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr2_0 =
                                     constructor_or_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
                                 let expr3_0 = constructor_not_reg(ctx, pattern4_0, expr2_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             &Opcode::BxorNot => {
@@ -9344,7 +9368,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr2_0 =
                                     constructor_xor_reg(ctx, pattern4_0, expr0_0, expr1_0)?;
                                 let expr3_0 = constructor_not_reg(ctx, pattern4_0, expr2_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             _ => {}
@@ -9365,7 +9389,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0 = constructor_and_reg(ctx, pattern4_0, expr3_0, expr0_0)?;
                             let expr5_0 = constructor_not_reg(ctx, pattern4_0, expr4_0)?;
                             let expr6_0 = constructor_or_reg(ctx, pattern4_0, expr5_0, expr2_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                     }
@@ -9377,7 +9401,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             // Rule at src/isa/s390x/lower.isle line 630.
                             let expr0_0 = C::put_in_reg(ctx, pattern6_1);
                             let expr1_0 = constructor_not_reg(ctx, pattern4_0, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -9401,7 +9425,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern6_2, pattern6_1, pattern6_3)?;
                             let expr1_0 = constructor_fpu_loadrev32(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -9422,7 +9446,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 =
                                 constructor_lower_address(ctx, pattern6_2, pattern6_1, pattern6_3)?;
                             let expr1_0 = constructor_fpu_loadrev64(ctx, &expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -9449,7 +9473,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr3_0: u8 = 32;
                             let expr4_0 = constructor_lshl_imm(ctx, expr2_0, expr1_0, expr3_0)?;
                             let expr5_0 = constructor_mov_to_fpr(ctx, expr4_0)?;
-                            let expr6_0 = C::value_reg(ctx, expr5_0);
+                            let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                     }
@@ -9471,7 +9495,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 constructor_lower_address(ctx, pattern6_2, pattern6_1, pattern6_3)?;
                             let expr1_0 = constructor_loadrev64(ctx, &expr0_0)?;
                             let expr2_0 = constructor_mov_to_fpr(ctx, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                     }
@@ -9492,7 +9516,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr2_0: u8 = 0;
                     let expr3_0 = C::uimm16shifted(ctx, expr1_0, expr2_0);
                     let expr4_0 = constructor_and_uimm16shifted(ctx, pattern3_0, expr0_0, expr3_0)?;
-                    let expr5_0 = C::value_reg(ctx, expr4_0);
+                    let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                     return Some(expr5_0);
                 }
             }
@@ -9511,7 +9535,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr2_0: u8 = 0;
                     let expr3_0 = C::uimm32shifted(ctx, expr1_0, expr2_0);
                     let expr4_0 = constructor_and_uimm32shifted(ctx, pattern3_0, expr0_0, expr3_0)?;
-                    let expr5_0 = C::value_reg(ctx, expr4_0);
+                    let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                     return Some(expr5_0);
                 }
             }
@@ -9531,7 +9555,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_add_simm16(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::i32_from_value(ctx, pattern7_0) {
@@ -9539,7 +9563,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_add_simm32(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_0) {
@@ -9558,7 +9582,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_reg_sext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -9583,7 +9607,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9596,7 +9620,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext32(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9624,7 +9648,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9650,7 +9674,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9662,7 +9686,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_add_simm16(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::i32_from_value(ctx, pattern7_1) {
@@ -9670,7 +9694,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_add_simm32(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_1) {
@@ -9689,7 +9713,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_reg_sext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -9714,7 +9738,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9727,7 +9751,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext32(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9755,7 +9779,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9781,7 +9805,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_add_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9792,7 +9816,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_add_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Isub => {
@@ -9802,7 +9826,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_add_simm16(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::i32_from_negated_value(ctx, pattern7_1) {
@@ -9810,7 +9834,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_add_simm32(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_1) {
@@ -9829,7 +9853,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_sub_reg_sext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -9854,7 +9878,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_sub_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9867,7 +9891,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_sub_mem_sext32(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9895,7 +9919,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_sub_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9921,7 +9945,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_sub_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -9932,7 +9956,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_sub_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imul => {
@@ -9942,7 +9966,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_mul_simm16(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::i32_from_value(ctx, pattern7_0) {
@@ -9950,7 +9974,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_mul_simm32(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_0) {
@@ -9969,7 +9993,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_mul_reg_sext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -9994,7 +10018,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10007,7 +10031,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext32(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10035,7 +10059,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10061,7 +10085,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10073,7 +10097,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_mul_simm16(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::i32_from_value(ctx, pattern7_1) {
@@ -10081,7 +10105,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_mul_simm32(ctx, pattern3_0, expr0_0, pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_1) {
@@ -10100,7 +10124,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_mul_reg_sext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -10125,7 +10149,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10138,7 +10162,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext32(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10166,7 +10190,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem_sext16(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10192,7 +10216,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_mul_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10203,7 +10227,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_mul_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Udiv => {
@@ -10225,7 +10249,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr9_0 = constructor_udivmod(ctx, expr7_0, &expr5_0, expr6_0)?;
                             let expr10_0 = constructor_regpair_lo(ctx, &expr9_0)?;
                             let expr11_0 = constructor_copy_reg(ctx, pattern3_0, expr10_0)?;
-                            let expr12_0 = C::value_reg(ctx, expr11_0);
+                            let expr12_0 = constructor_output_reg(ctx, expr11_0)?;
                             return Some(expr12_0);
                         }
                         &Opcode::Sdiv => {
@@ -10247,7 +10271,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = constructor_sdivmod(ctx, expr5_0, &expr3_0, expr4_0)?;
                             let expr9_0 = constructor_regpair_lo(ctx, &expr8_0)?;
                             let expr10_0 = constructor_copy_reg(ctx, pattern3_0, expr9_0)?;
-                            let expr11_0 = C::value_reg(ctx, expr10_0);
+                            let expr11_0 = constructor_output_reg(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         &Opcode::Urem => {
@@ -10268,7 +10292,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = constructor_udivmod(ctx, expr6_0, &expr4_0, expr5_0)?;
                             let expr9_0 = constructor_regpair_hi(ctx, &expr8_0)?;
                             let expr10_0 = constructor_copy_reg(ctx, pattern3_0, expr9_0)?;
-                            let expr11_0 = C::value_reg(ctx, expr10_0);
+                            let expr11_0 = constructor_output_reg(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         &Opcode::Srem => {
@@ -10290,7 +10314,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = constructor_sdivmod(ctx, expr5_0, &expr7_0, expr4_0)?;
                             let expr9_0 = constructor_regpair_hi(ctx, &expr8_0)?;
                             let expr10_0 = constructor_copy_reg(ctx, pattern3_0, expr9_0)?;
-                            let expr11_0 = C::value_reg(ctx, expr10_0);
+                            let expr11_0 = constructor_output_reg(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         &Opcode::IaddIfcout => {
@@ -10301,7 +10325,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_add_logical_zimm32(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = constructor_value_regs_ifcout(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_ifcout(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_0) {
@@ -10320,8 +10344,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_logical_reg_zext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 =
-                                                constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                            let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -10345,8 +10368,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_logical_mem_zext32(
                                                 ctx, pattern3_0, expr0_0, &expr1_0,
                                             )?;
-                                            let expr3_0 =
-                                                constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                            let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -10373,7 +10395,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
                                                 let expr3_0 =
-                                                    constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                                    constructor_output_ifcout(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10386,7 +10408,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_add_logical_zimm32(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = constructor_value_regs_ifcout(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_ifcout(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::def_inst(ctx, pattern7_1) {
@@ -10405,8 +10427,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_logical_reg_zext32(
                                                 ctx, pattern3_0, expr0_0, expr1_0,
                                             )?;
-                                            let expr3_0 =
-                                                constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                            let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -10430,8 +10451,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr2_0 = constructor_add_logical_mem_zext32(
                                                 ctx, pattern3_0, expr0_0, &expr1_0,
                                             )?;
-                                            let expr3_0 =
-                                                constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                            let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                             return Some(expr3_0);
                                         }
                                     }
@@ -10458,7 +10478,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
                                                 let expr3_0 =
-                                                    constructor_value_regs_ifcout(ctx, expr2_0)?;
+                                                    constructor_output_ifcout(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10470,7 +10490,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 =
                                 constructor_add_logical_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = constructor_value_regs_ifcout(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Band => {
@@ -10495,7 +10515,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_and_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10510,7 +10530,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_and_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) =
@@ -10521,7 +10541,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_and_uimm16shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             let pattern8_0 = C::value_type(ctx, pattern7_1);
@@ -10544,7 +10564,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_and_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10559,7 +10579,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_and_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) =
@@ -10570,14 +10590,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_and_uimm16shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 637.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_and_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bor => {
@@ -10602,7 +10622,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_or_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10615,7 +10635,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_or_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::uimm16shifted_from_value(ctx, pattern7_0) {
@@ -10624,7 +10644,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_or_uimm16shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             let pattern8_0 = C::value_type(ctx, pattern7_1);
@@ -10647,7 +10667,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_or_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10660,7 +10680,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_or_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::uimm16shifted_from_value(ctx, pattern7_1) {
@@ -10669,14 +10689,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_or_uimm16shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 660.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_or_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
@@ -10701,7 +10721,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_xor_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10714,7 +10734,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_xor_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             let pattern8_0 = C::value_type(ctx, pattern7_1);
@@ -10737,7 +10757,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                 let expr2_0 = constructor_xor_mem(
                                                     ctx, pattern3_0, expr0_0, &expr1_0,
                                                 )?;
-                                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                                 return Some(expr3_0);
                                             }
                                         }
@@ -10750,14 +10770,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_xor_uimm32shifted(
                                     ctx, pattern3_0, expr0_0, pattern8_0,
                                 )?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
+                                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 683.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_xor_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ishl => {
@@ -10768,7 +10788,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr2_0 =
                                     constructor_lshl_imm(ctx, pattern3_0, expr1_0, expr0_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 477.
@@ -10776,7 +10796,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = constructor_mask_amt_reg(ctx, pattern3_0, expr0_0)?;
                             let expr2_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr3_0 = constructor_lshl_reg(ctx, pattern3_0, expr2_0, expr1_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ushr => {
@@ -10787,7 +10807,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::mask_amt_imm(ctx, pattern3_0, pattern8_0);
                                 let expr2_0 = constructor_ty_ext32(ctx, pattern3_0)?;
                                 let expr3_0 = constructor_lshr_imm(ctx, expr2_0, expr0_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 491.
@@ -10796,7 +10816,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_mask_amt_reg(ctx, pattern3_0, expr1_0)?;
                             let expr3_0 = constructor_ty_ext32(ctx, pattern3_0)?;
                             let expr4_0 = constructor_lshr_reg(ctx, expr3_0, expr0_0, expr2_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Sshr => {
@@ -10807,7 +10827,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::mask_amt_imm(ctx, pattern3_0, pattern8_0);
                                 let expr2_0 = constructor_ty_ext32(ctx, pattern3_0)?;
                                 let expr3_0 = constructor_ashr_imm(ctx, expr2_0, expr0_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 508.
@@ -10816,7 +10836,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_mask_amt_reg(ctx, pattern3_0, expr1_0)?;
                             let expr3_0 = constructor_ty_ext32(ctx, pattern3_0)?;
                             let expr4_0 = constructor_ashr_reg(ctx, expr3_0, expr0_0, expr2_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         _ => {}
@@ -10843,7 +10863,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr1_0 = constructor_neg_reg_sext32(
                                                 ctx, pattern3_0, expr0_0,
                                             )?;
-                                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                             return Some(expr2_0);
                                         }
                                     }
@@ -10852,7 +10872,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             // Rule at src/isa/s390x/lower.isle line 189.
                             let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                             let expr1_0 = constructor_neg_reg(ctx, pattern3_0, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         &Opcode::Iabs => {
@@ -10871,7 +10891,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                             let expr1_0 = constructor_abs_reg_sext32(
                                                 ctx, pattern3_0, expr0_0,
                                             )?;
-                                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                                             return Some(expr2_0);
                                         }
                                     }
@@ -10881,7 +10901,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr0_0 = constructor_ty_ext32(ctx, pattern3_0)?;
                             let expr1_0 = constructor_put_in_reg_sext32(ctx, pattern5_1)?;
                             let expr2_0 = constructor_abs_reg(ctx, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Clz => {
@@ -10891,7 +10911,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr2_0 = constructor_clz_reg(ctx, expr1_0, expr0_0)?;
                             let expr3_0 = constructor_regpair_hi(ctx, &expr2_0)?;
                             let expr4_0 = constructor_clz_offset(ctx, pattern3_0, expr3_0)?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                         &Opcode::Cls => {
@@ -10906,7 +10926,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr7_0 = constructor_clz_reg(ctx, expr6_0, expr5_0)?;
                             let expr8_0 = constructor_regpair_hi(ctx, &expr7_0)?;
                             let expr9_0 = constructor_clz_offset(ctx, pattern3_0, expr8_0)?;
-                            let expr10_0 = C::value_reg(ctx, expr9_0);
+                            let expr10_0 = constructor_output_reg(ctx, expr9_0)?;
                             return Some(expr10_0);
                         }
                         &Opcode::Bint => {
@@ -10915,7 +10935,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0: u64 = 1;
                             let expr2_0 = constructor_imm(ctx, pattern3_0, expr1_0)?;
                             let expr3_0 = constructor_and_reg(ctx, pattern3_0, expr0_0, expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -10940,14 +10960,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr2_0 =
                                     constructor_rot_imm(ctx, pattern3_0, expr1_0, expr0_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 524.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = constructor_rot_reg(ctx, pattern3_0, expr0_0, expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Rotr => {
@@ -10958,7 +10978,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr2_0 =
                                     constructor_rot_imm(ctx, pattern3_0, expr1_0, expr0_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             // Rule at src/isa/s390x/lower.isle line 560.
@@ -10966,7 +10986,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 = constructor_neg_reg(ctx, pattern3_0, expr0_0)?;
                             let expr2_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr3_0 = constructor_rot_reg(ctx, pattern3_0, expr2_0, expr1_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
+                            let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -10994,7 +11014,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         ctx, pattern3_0, expr1_0, &expr3_0,
                                     )?;
                                     let expr5_0 = constructor_bswap_reg(ctx, pattern3_0, expr4_0)?;
-                                    let expr6_0 = C::value_reg(ctx, expr5_0);
+                                    let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                                     return Some(expr6_0);
                                 }
                                 &AtomicRmwOp::Or => {
@@ -11009,7 +11029,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         ctx, pattern3_0, expr1_0, &expr3_0,
                                     )?;
                                     let expr5_0 = constructor_bswap_reg(ctx, pattern3_0, expr4_0)?;
-                                    let expr6_0 = C::value_reg(ctx, expr5_0);
+                                    let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                                     return Some(expr6_0);
                                 }
                                 &AtomicRmwOp::Xor => {
@@ -11024,7 +11044,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         ctx, pattern3_0, expr1_0, &expr3_0,
                                     )?;
                                     let expr5_0 = constructor_bswap_reg(ctx, pattern3_0, expr4_0)?;
-                                    let expr6_0 = C::value_reg(ctx, expr5_0);
+                                    let expr6_0 = constructor_output_reg(ctx, expr5_0)?;
                                     return Some(expr6_0);
                                 }
                                 _ => {}
@@ -11042,7 +11062,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr3_0 = constructor_atomic_rmw_add(
                                         ctx, pattern3_0, expr0_0, &expr2_0,
                                     )?;
-                                    let expr4_0 = C::value_reg(ctx, expr3_0);
+                                    let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                     return Some(expr4_0);
                                 }
                                 &AtomicRmwOp::And => {
@@ -11055,7 +11075,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr3_0 = constructor_atomic_rmw_and(
                                         ctx, pattern3_0, expr0_0, &expr2_0,
                                     )?;
-                                    let expr4_0 = C::value_reg(ctx, expr3_0);
+                                    let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                     return Some(expr4_0);
                                 }
                                 &AtomicRmwOp::Or => {
@@ -11068,7 +11088,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr3_0 = constructor_atomic_rmw_or(
                                         ctx, pattern3_0, expr0_0, &expr2_0,
                                     )?;
-                                    let expr4_0 = C::value_reg(ctx, expr3_0);
+                                    let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                     return Some(expr4_0);
                                 }
                                 &AtomicRmwOp::Sub => {
@@ -11082,7 +11102,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr4_0 = constructor_atomic_rmw_add(
                                         ctx, pattern3_0, expr1_0, &expr3_0,
                                     )?;
-                                    let expr5_0 = C::value_reg(ctx, expr4_0);
+                                    let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                                     return Some(expr5_0);
                                 }
                                 &AtomicRmwOp::Xor => {
@@ -11095,7 +11115,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     let expr3_0 = constructor_atomic_rmw_xor(
                                         ctx, pattern3_0, expr0_0, &expr2_0,
                                     )?;
-                                    let expr4_0 = C::value_reg(ctx, expr3_0);
+                                    let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                     return Some(expr4_0);
                                 }
                                 _ => {}
@@ -11115,7 +11135,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr7_0 = constructor_casloop(
                             ctx, &expr2_0, pattern3_0, pattern5_2, expr1_0, expr6_0,
                         )?;
-                        let expr8_0 = C::value_reg(ctx, expr7_0);
+                        let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                         return Some(expr8_0);
                     }
                 }
@@ -11140,7 +11160,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 ctx, pattern3_0, expr1_0, expr3_0, &expr5_0,
                             )?;
                             let expr7_0 = constructor_bswap_reg(ctx, pattern3_0, expr6_0)?;
-                            let expr8_0 = C::value_reg(ctx, expr7_0);
+                            let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11153,7 +11173,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0 = constructor_atomic_cas_impl(
                                 ctx, pattern3_0, expr0_0, expr1_0, &expr3_0,
                             )?;
-                            let expr5_0 = C::value_reg(ctx, expr4_0);
+                            let expr5_0 = constructor_output_reg(ctx, expr4_0)?;
                             return Some(expr5_0);
                         }
                     }
@@ -11179,7 +11199,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = C::floatcc_as_cond(ctx, &expr7_0);
                             let expr9_0 = C::trap_code_integer_overflow(ctx);
                             let expr10_0 = constructor_trap_if(ctx, &expr6_0, &expr8_0, &expr9_0)?;
-                            let expr11_0 = C::value_reg(ctx, expr10_0);
+                            let expr11_0 = constructor_output_reg(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         &Opcode::FcvtToUintSat => {
@@ -11195,7 +11215,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 =
                                 constructor_cmov_imm(ctx, pattern3_0, &expr4_0, expr5_0, expr1_0)?;
                             let expr7_0 = constructor_with_flags_reg(ctx, &expr2_0, &expr6_0)?;
-                            let expr8_0 = C::value_reg(ctx, expr7_0);
+                            let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         &Opcode::FcvtToSint => {
@@ -11214,7 +11234,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = C::floatcc_as_cond(ctx, &expr7_0);
                             let expr9_0 = C::trap_code_integer_overflow(ctx);
                             let expr10_0 = constructor_trap_if(ctx, &expr6_0, &expr8_0, &expr9_0)?;
-                            let expr11_0 = C::value_reg(ctx, expr10_0);
+                            let expr11_0 = constructor_output_reg(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         &Opcode::FcvtToSintSat => {
@@ -11230,7 +11250,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 =
                                 constructor_cmov_imm(ctx, pattern3_0, &expr4_0, expr5_0, expr1_0)?;
                             let expr7_0 = constructor_with_flags_reg(ctx, &expr2_0, &expr6_0)?;
-                            let expr8_0 = C::value_reg(ctx, expr7_0);
+                            let expr8_0 = constructor_output_reg(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         _ => {}
@@ -11257,7 +11277,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I32;
                             let expr5_0 = C::ty_bits(ctx, pattern3_0);
                             let expr6_0 = constructor_lshr_imm(ctx, expr4_0, expr3_0, expr5_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         &Opcode::Smulhi => {
@@ -11270,7 +11290,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: Type = I32;
                             let expr5_0 = C::ty_bits(ctx, pattern3_0);
                             let expr6_0 = constructor_ashr_imm(ctx, expr4_0, expr3_0, expr5_0)?;
-                            let expr7_0 = C::value_reg(ctx, expr6_0);
+                            let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                             return Some(expr7_0);
                         }
                         &Opcode::Rotl => {
@@ -11289,7 +11309,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         constructor_lshr_imm(ctx, expr1_0, expr0_0, expr3_0)?;
                                     let expr6_0 =
                                         constructor_or_reg(ctx, pattern3_0, expr4_0, expr5_0)?;
-                                    let expr7_0 = C::value_reg(ctx, expr6_0);
+                                    let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                                     return Some(expr7_0);
                                 }
                             }
@@ -11303,7 +11323,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 = constructor_lshl_reg(ctx, expr1_0, expr0_0, expr4_0)?;
                             let expr7_0 = constructor_lshr_reg(ctx, expr1_0, expr0_0, expr5_0)?;
                             let expr8_0 = constructor_or_reg(ctx, pattern3_0, expr6_0, expr7_0)?;
-                            let expr9_0 = C::value_reg(ctx, expr8_0);
+                            let expr9_0 = constructor_output_reg(ctx, expr8_0)?;
                             return Some(expr9_0);
                         }
                         &Opcode::Rotr => {
@@ -11322,7 +11342,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         constructor_lshr_imm(ctx, expr1_0, expr0_0, expr2_0)?;
                                     let expr6_0 =
                                         constructor_or_reg(ctx, pattern3_0, expr4_0, expr5_0)?;
-                                    let expr7_0 = C::value_reg(ctx, expr6_0);
+                                    let expr7_0 = constructor_output_reg(ctx, expr6_0)?;
                                     return Some(expr7_0);
                                 }
                             }
@@ -11336,7 +11356,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 = constructor_lshl_reg(ctx, expr1_0, expr0_0, expr5_0)?;
                             let expr7_0 = constructor_lshr_reg(ctx, expr1_0, expr0_0, expr4_0)?;
                             let expr8_0 = constructor_or_reg(ctx, pattern3_0, expr6_0, expr7_0)?;
-                            let expr9_0 = C::value_reg(ctx, expr8_0);
+                            let expr9_0 = constructor_output_reg(ctx, expr8_0)?;
                             return Some(expr9_0);
                         }
                         _ => {}
@@ -11372,7 +11392,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr11_0 = constructor_casloop_subword(
                             ctx, &expr4_0, pattern3_0, pattern5_2, expr3_0, expr2_0, expr10_0,
                         )?;
-                        let expr12_0 = C::value_reg(ctx, expr11_0);
+                        let expr12_0 = constructor_output_reg(ctx, expr11_0)?;
                         return Some(expr12_0);
                     }
                 }
@@ -11407,7 +11427,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr12_0 = constructor_casloop_subword(
                             ctx, &expr5_0, pattern3_0, pattern5_2, expr4_0, expr3_0, expr11_0,
                         )?;
-                        let expr13_0 = C::value_reg(ctx, expr12_0);
+                        let expr13_0 = constructor_output_reg(ctx, expr12_0)?;
                         return Some(expr13_0);
                     }
                 }
@@ -11440,19 +11460,19 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr12_0 = constructor_regpair_hi(ctx, &expr9_0)?;
                             let expr13_0 =
                                 constructor_sub_reg(ctx, pattern3_0, expr11_0, expr12_0)?;
-                            let expr14_0 = C::value_reg(ctx, expr13_0);
+                            let expr14_0 = constructor_output_reg(ctx, expr13_0)?;
                             return Some(expr14_0);
                         }
                         &Opcode::Uextend => {
                             // Rule at src/isa/s390x/lower.isle line 603.
                             let expr0_0 = constructor_put_in_reg_zext32(ctx, pattern5_1)?;
-                            let expr1_0 = C::value_reg(ctx, expr0_0);
+                            let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                             return Some(expr1_0);
                         }
                         &Opcode::Sextend => {
                             // Rule at src/isa/s390x/lower.isle line 614.
                             let expr0_0 = constructor_put_in_reg_sext32(ctx, pattern5_1)?;
-                            let expr1_0 = C::value_reg(ctx, expr0_0);
+                            let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                             return Some(expr1_0);
                         }
                         _ => {}
@@ -11471,7 +11491,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr2_0 = constructor_zext32_mem(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Sload8 => {
@@ -11480,7 +11500,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr2_0 = constructor_sext32_mem(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Uload16 => {
@@ -11492,7 +11512,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev16(ctx, &expr0_0)?;
                                 let expr2_0: Type = I16;
                                 let expr3_0 = constructor_zext32_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11502,7 +11522,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_zext32_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11515,7 +11535,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev16(ctx, &expr0_0)?;
                                 let expr2_0: Type = I16;
                                 let expr3_0 = constructor_sext32_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11525,7 +11545,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_sext32_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11558,19 +11578,19 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr10_0 = constructor_imm(ctx, expr8_0, expr9_0)?;
                             let expr11_0 = constructor_regpair_hi(ctx, &expr6_0)?;
                             let expr12_0 = constructor_sub_reg(ctx, expr7_0, expr10_0, expr11_0)?;
-                            let expr13_0 = C::value_reg(ctx, expr12_0);
+                            let expr13_0 = constructor_output_reg(ctx, expr12_0)?;
                             return Some(expr13_0);
                         }
                         &Opcode::Uextend => {
                             // Rule at src/isa/s390x/lower.isle line 607.
                             let expr0_0 = constructor_put_in_reg_zext64(ctx, pattern5_1)?;
-                            let expr1_0 = C::value_reg(ctx, expr0_0);
+                            let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                             return Some(expr1_0);
                         }
                         &Opcode::Sextend => {
                             // Rule at src/isa/s390x/lower.isle line 618.
                             let expr0_0 = constructor_put_in_reg_sext64(ctx, pattern5_1)?;
-                            let expr1_0 = C::value_reg(ctx, expr0_0);
+                            let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                             return Some(expr1_0);
                         }
                         _ => {}
@@ -11589,7 +11609,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr2_0 = constructor_zext64_mem(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Sload8 => {
@@ -11598,7 +11618,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr1_0 =
                                 constructor_lower_address(ctx, pattern5_2, pattern5_1, pattern5_3)?;
                             let expr2_0 = constructor_sext64_mem(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = C::value_reg(ctx, expr2_0);
+                            let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Uload16 => {
@@ -11610,7 +11630,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev16(ctx, &expr0_0)?;
                                 let expr2_0: Type = I16;
                                 let expr3_0 = constructor_zext64_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11620,7 +11640,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_zext64_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11633,7 +11653,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev16(ctx, &expr0_0)?;
                                 let expr2_0: Type = I16;
                                 let expr3_0 = constructor_sext64_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11643,7 +11663,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_sext64_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11656,7 +11676,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev32(ctx, &expr0_0)?;
                                 let expr2_0: Type = I32;
                                 let expr3_0 = constructor_zext64_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11666,7 +11686,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_zext64_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11679,7 +11699,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 = constructor_loadrev32(ctx, &expr0_0)?;
                                 let expr2_0: Type = I32;
                                 let expr3_0 = constructor_sext64_reg(ctx, expr2_0, expr1_0)?;
-                                let expr4_0 = C::value_reg(ctx, expr3_0);
+                                let expr4_0 = constructor_output_reg(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(()) = C::bigendian(ctx, pattern5_2) {
@@ -11689,7 +11709,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     ctx, pattern5_2, pattern5_1, pattern5_3,
                                 )?;
                                 let expr2_0 = constructor_sext64_mem(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
+                                let expr3_0 = constructor_output_reg(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                         }
@@ -11708,7 +11728,7 @@ pub fn constructor_lower_branch<C: Context>(
     ctx: &mut C,
     arg0: Inst,
     arg1: &VecMachLabel,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     let pattern1_0 = C::inst_data(ctx, pattern0_0);
     match &pattern1_0 {
@@ -11731,12 +11751,12 @@ pub fn constructor_lower_branch<C: Context>(
                 let expr7_0: u8 = 0;
                 let expr8_0 = C::vec_element(ctx, pattern4_0, expr7_0);
                 let expr9_0 = constructor_oneway_cond_br_bool(ctx, &expr6_0, expr8_0)?;
-                let expr10_0 = constructor_value_regs_none(ctx, &expr9_0)?;
+                let expr10_0 = constructor_side_effect(ctx, &expr9_0)?;
                 let expr11_0: Type = I64;
                 let expr12_0: u8 = 2;
                 let expr13_0 = constructor_lshl_imm(ctx, expr11_0, expr0_0, expr12_0)?;
                 let expr14_0 = constructor_jt_sequence(ctx, expr13_0, pattern4_0)?;
-                let expr15_0 = constructor_value_regs_none(ctx, &expr14_0)?;
+                let expr15_0 = constructor_side_effect(ctx, &expr14_0)?;
                 return Some(expr15_0);
             }
         }
@@ -11757,7 +11777,7 @@ pub fn constructor_lower_branch<C: Context>(
                     let expr4_0: u8 = 1;
                     let expr5_0 = C::vec_element(ctx, pattern5_0, expr4_0);
                     let expr6_0 = constructor_cond_br_bool(ctx, &expr1_0, expr3_0, expr5_0)?;
-                    let expr7_0 = constructor_value_regs_none(ctx, &expr6_0)?;
+                    let expr7_0 = constructor_side_effect(ctx, &expr6_0)?;
                     return Some(expr7_0);
                 }
                 &Opcode::Brnz => {
@@ -11770,7 +11790,7 @@ pub fn constructor_lower_branch<C: Context>(
                     let expr3_0: u8 = 1;
                     let expr4_0 = C::vec_element(ctx, pattern5_0, expr3_0);
                     let expr5_0 = constructor_cond_br_bool(ctx, &expr0_0, expr2_0, expr4_0)?;
-                    let expr6_0 = constructor_value_regs_none(ctx, &expr5_0)?;
+                    let expr6_0 = constructor_side_effect(ctx, &expr5_0)?;
                     return Some(expr6_0);
                 }
                 _ => {}
@@ -11788,7 +11808,7 @@ pub fn constructor_lower_branch<C: Context>(
                 let expr0_0: u8 = 0;
                 let expr1_0 = C::vec_element(ctx, pattern5_0, expr0_0);
                 let expr2_0 = constructor_jump_impl(ctx, expr1_0)?;
-                let expr3_0 = constructor_value_regs_none(ctx, &expr2_0)?;
+                let expr3_0 = constructor_side_effect(ctx, &expr2_0)?;
                 return Some(expr3_0);
             }
         }
@@ -11821,7 +11841,7 @@ pub fn constructor_lower_branch<C: Context>(
                             let expr5_0 = C::vec_element(ctx, pattern10_0, expr4_0);
                             let expr6_0 =
                                 constructor_cond_br_bool(ctx, &expr1_0, expr3_0, expr5_0)?;
-                            let expr7_0 = constructor_value_regs_none(ctx, &expr6_0)?;
+                            let expr7_0 = constructor_side_effect(ctx, &expr6_0)?;
                             return Some(expr7_0);
                         }
                     }
@@ -11833,15 +11853,14 @@ pub fn constructor_lower_branch<C: Context>(
     return None;
 }
 
-// Generated as internal constructor for term value_regs_ifcout.
-pub fn constructor_value_regs_ifcout<C: Context>(ctx: &mut C, arg0: Reg) -> Option<ValueRegs> {
+// Generated as internal constructor for term output_ifcout.
+pub fn constructor_output_ifcout<C: Context>(ctx: &mut C, arg0: Reg) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     // Rule at src/isa/s390x/lower.isle line 154.
-    let expr0_0: Type = I64;
-    let expr1_0 = C::temp_writable_reg(ctx, expr0_0);
-    let expr2_0 = C::writable_reg_to_reg(ctx, expr1_0);
-    let expr3_0 = C::value_regs(ctx, pattern0_0, expr2_0);
-    return Some(expr3_0);
+    let expr0_0 = C::value_reg(ctx, pattern0_0);
+    let expr1_0 = C::value_regs_invalid(ctx);
+    let expr2_0 = C::output_pair(ctx, expr0_0, expr1_0);
+    return Some(expr2_0);
 }
 
 // Generated as internal constructor for term zero_divisor_check_needed.
@@ -13109,12 +13128,12 @@ pub fn constructor_atomic_cas_body<C: Context>(
 pub fn constructor_atomic_store_impl<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     // Rule at src/isa/s390x/lower.isle line 1858.
-    let expr0_0 = constructor_value_regs_none(ctx, pattern0_0)?;
+    let expr0_0 = constructor_side_effect(ctx, pattern0_0)?;
     let expr1_0 = constructor_fence_impl(ctx)?;
-    let expr2_0 = constructor_value_regs_none(ctx, &expr1_0)?;
+    let expr2_0 = constructor_side_effect(ctx, &expr1_0)?;
     return Some(expr2_0);
 }
 
diff --git a/cranelift/codegen/src/isa/x64/inst.isle b/cranelift/codegen/src/isa/x64/inst.isle
index 51f9e454dc..ac85666147 100644
--- a/cranelift/codegen/src/isa/x64/inst.isle
+++ b/cranelift/codegen/src/isa/x64/inst.isle
@@ -1009,20 +1009,20 @@
 (rule (put_in_xmm_mem_imm val)
       (xmm_mem_imm_new (put_in_reg_mem_imm val)))
 
-;; Construct a `ValueRegs` out of a single GPR register.
-(decl value_gpr (Gpr) ValueRegs)
-(rule (value_gpr x)
-      (value_reg (gpr_to_reg x)))
+;; Construct an `InstOutput` out of a single GPR register.
+(decl output_gpr (Gpr) InstOutput)
+(rule (output_gpr x)
+      (output_reg (gpr_to_reg x)))
 
 ;; Construct a `ValueRegs` out of two GPR registers.
 (decl value_gprs (Gpr Gpr) ValueRegs)
 (rule (value_gprs x y)
       (value_regs (gpr_to_reg x) (gpr_to_reg y)))
 
-;; Construct a `ValueRegs` out of a single XMM register.
-(decl value_xmm (Xmm) ValueRegs)
-(rule (value_xmm x)
-      (value_reg (xmm_to_reg x)))
+;; Construct an `InstOutput` out of a single XMM register.
+(decl output_xmm (Xmm) InstOutput)
+(rule (output_xmm x)
+      (output_reg (xmm_to_reg x)))
 
 ;; Get the `n`th reg in a `ValueRegs` and construct a GPR from it.
 ;;
@@ -2223,7 +2223,7 @@
 
 ;;;; Automatic conversions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
-(convert Gpr ValueRegs value_gpr)
+(convert Gpr InstOutput output_gpr)
 (convert Value Gpr put_in_gpr)
 (convert Value GprMem put_in_gpr_mem)
 (convert Value GprMemImm put_in_gpr_mem_imm)
@@ -2242,7 +2242,7 @@
 (convert WritableGpr WritableReg writable_gpr_to_reg)
 (convert WritableGpr Reg writable_gpr_to_r_reg)
 
-(convert Xmm ValueRegs value_xmm)
+(convert Xmm InstOutput output_xmm)
 (convert Value Xmm put_in_xmm)
 (convert Value XmmMem put_in_xmm_mem)
 (convert Value XmmMemImm put_in_xmm_mem_imm)
diff --git a/cranelift/codegen/src/isa/x64/lower.isle b/cranelift/codegen/src/isa/x64/lower.isle
index c9384ba741..6efe439484 100644
--- a/cranelift/codegen/src/isa/x64/lower.isle
+++ b/cranelift/codegen/src/isa/x64/lower.isle
@@ -2,7 +2,7 @@
 
 ;; The main lowering constructor term: takes a clif `Inst` and returns the
 ;; register(s) within which the lowered instruction's result values live.
-(decl lower (Inst) ValueRegs)
+(decl lower (Inst) InstOutput)
 
 ;;;; Rules for `iconst` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -148,48 +148,39 @@
 ;; replace this with a bool carry flag, and all consumers of `iflags`
 ;; remain in the handwritten pattern-matching code and explicitly
 ;; match on the flags producer. So we can get away with just
-;; allocating a second temp so that the reg-renaming code does the
+;; using an invalid second output, and the reg-renaming code does the
 ;; right thing, for now. For safety, we assert elsewhere that no one
 ;; actually uses the register assigned to the SSA `iflags`-typed
 ;; `Value`.
 
-(decl unused_iflags () Gpr)
-(rule (unused_iflags)
-      (temp_writable_gpr))
+(decl output_ifcout (Reg) InstOutput)
+(rule (output_ifcout reg)
+      (output_pair reg (value_regs_invalid)))
 
 ;; Add two registers.
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x y)))
-      (value_gprs (add ty x y)
-                  (unused_iflags)))
+      (output_ifcout (add ty x y)))
 
 ;; Add a register and an immediate.
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x (simm32_from_value y))))
-      (value_gprs (add ty x y)
-                  (unused_iflags)))
+      (output_ifcout (add ty x y)))
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout (simm32_from_value x) y)))
-      (value_gprs (add ty y x)
-                  (unused_iflags)))
+      (output_ifcout (add ty y x)))
 
 ;; Add a register and memory.
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x (sinkable_load y))))
-      (value_gprs (add ty
-                       x
-                       (sink_load_to_gpr_mem_imm y))
-                  (unused_iflags)))
+      (output_ifcout (add ty x (sink_load_to_gpr_mem_imm y))))
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout (sinkable_load x) y)))
-      (value_gprs (add ty
-                       y
-                       (sink_load_to_gpr_mem_imm x))
-                  (unused_iflags)))
+      (output_ifcout (add ty y (sink_load_to_gpr_mem_imm x))))
 
 ;; (No `iadd_ifcout` for `i128`.)
 
diff --git a/cranelift/codegen/src/isa/x64/lower/isle/generated_code.manifest b/cranelift/codegen/src/isa/x64/lower/isle/generated_code.manifest
index 914dd1a3f8..4588040dd7 100644
--- a/cranelift/codegen/src/isa/x64/lower/isle/generated_code.manifest
+++ b/cranelift/codegen/src/isa/x64/lower/isle/generated_code.manifest
@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 8bf92e18323e7041
-src/isa/x64/inst.isle 1948445a25530d71
-src/isa/x64/lower.isle d1ee574941be387
+src/prelude.isle 957023853b23dacb
+src/isa/x64/inst.isle 5ee89205e6e9a46b
+src/isa/x64/lower.isle 348a808ea5de4cdb
diff --git a/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs b/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs
index 6f189d117e..6e4b21dc85 100644
--- a/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs
+++ b/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs
@@ -25,6 +25,12 @@ pub trait Context {
     fn value_reg(&mut self, arg0: Reg) -> ValueRegs;
     fn value_regs(&mut self, arg0: Reg, arg1: Reg) -> ValueRegs;
     fn value_regs_invalid(&mut self) -> ValueRegs;
+    fn output_none(&mut self) -> InstOutput;
+    fn output(&mut self, arg0: ValueRegs) -> InstOutput;
+    fn output_pair(&mut self, arg0: ValueRegs, arg1: ValueRegs) -> InstOutput;
+    fn output_builder_new(&mut self) -> InstOutputBuilder;
+    fn output_builder_push(&mut self, arg0: &InstOutputBuilder, arg1: ValueRegs) -> Unit;
+    fn output_builder_finish(&mut self, arg0: &InstOutputBuilder) -> InstOutput;
     fn temp_writable_reg(&mut self, arg0: Type) -> WritableReg;
     fn invalid_reg(&mut self) -> Reg;
     fn put_in_reg(&mut self, arg0: Value) -> Reg;
@@ -127,13 +133,13 @@ pub trait Context {
     fn sse_insertps_lane_imm(&mut self, arg0: u8) -> u8;
 }
 
-/// Internal type SideEffectNoResult: defined at src/prelude.isle line 308.
+/// Internal type SideEffectNoResult: defined at src/prelude.isle line 345.
 #[derive(Clone, Debug)]
 pub enum SideEffectNoResult {
     Inst { inst: MInst },
 }
 
-/// Internal type ProducesFlags: defined at src/prelude.isle line 330.
+/// Internal type ProducesFlags: defined at src/prelude.isle line 367.
 #[derive(Clone, Debug)]
 pub enum ProducesFlags {
     ProducesFlagsSideEffect { inst: MInst },
@@ -141,7 +147,7 @@ pub enum ProducesFlags {
     ProducesFlagsReturnsResultWithConsumer { inst: MInst, result: Reg },
 }
 
-/// Internal type ConsumesFlags: defined at src/prelude.isle line 341.
+/// Internal type ConsumesFlags: defined at src/prelude.isle line 378.
 #[derive(Clone, Debug)]
 pub enum ConsumesFlags {
     ConsumesFlagsReturnsResultWithProducer {
@@ -494,10 +500,28 @@ pub enum ExtendKind {
     Zero,
 }
 
+// Generated as internal constructor for term output_reg.
+pub fn constructor_output_reg<C: Context>(ctx: &mut C, arg0: Reg) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 86.
+    let expr0_0 = C::value_reg(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
+// Generated as internal constructor for term output_value.
+pub fn constructor_output_value<C: Context>(ctx: &mut C, arg0: Value) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
+    // Rule at src/prelude.isle line 90.
+    let expr0_0 = C::put_in_regs(ctx, pattern0_0);
+    let expr1_0 = C::output(ctx, expr0_0);
+    return Some(expr1_0);
+}
+
 // Generated as internal constructor for term temp_reg.
 pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 73.
+    // Rule at src/prelude.isle line 110.
     let expr0_0 = C::temp_writable_reg(ctx, pattern0_0);
     let expr1_0 = C::writable_reg_to_reg(ctx, expr0_0);
     return Some(expr1_0);
@@ -506,26 +530,26 @@ pub fn constructor_temp_reg<C: Context>(ctx: &mut C, arg0: Type) -> Option<Reg>
 // Generated as internal constructor for term lo_reg.
 pub fn constructor_lo_reg<C: Context>(ctx: &mut C, arg0: Value) -> Option<Reg> {
     let pattern0_0 = arg0;
-    // Rule at src/prelude.isle line 108.
+    // Rule at src/prelude.isle line 145.
     let expr0_0 = C::put_in_regs(ctx, pattern0_0);
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
     return Some(expr2_0);
 }
 
-// Generated as internal constructor for term value_regs_none.
-pub fn constructor_value_regs_none<C: Context>(
+// Generated as internal constructor for term side_effect.
+pub fn constructor_side_effect<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 313.
+        // Rule at src/prelude.isle line 350.
         let expr0_0 = C::emit(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -535,15 +559,15 @@ pub fn constructor_value_regs_none<C: Context>(
 pub fn constructor_safepoint<C: Context>(
     ctx: &mut C,
     arg0: &SideEffectNoResult,
-) -> Option<ValueRegs> {
+) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     if let &SideEffectNoResult::Inst {
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 319.
+        // Rule at src/prelude.isle line 356.
         let expr0_0 = C::emit_safepoint(ctx, pattern1_0);
-        let expr1_0 = C::value_regs_invalid(ctx);
+        let expr1_0 = C::output_none(ctx);
         return Some(expr1_0);
     }
     return None;
@@ -567,7 +591,7 @@ pub fn constructor_consumes_flags_concat<C: Context>(
             result: pattern3_1,
         } = pattern2_0
         {
-            // Rule at src/prelude.isle line 353.
+            // Rule at src/prelude.isle line 390.
             let expr0_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
             let expr1_0 = ConsumesFlags::ConsumesFlagsTwiceReturnsValueRegs {
                 inst1: pattern1_0.clone(),
@@ -597,7 +621,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst: ref pattern3_0,
                     result: pattern3_1,
                 } => {
-                    // Rule at src/prelude.isle line 378.
+                    // Rule at src/prelude.isle line 415.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_0);
                     let expr2_0 = C::value_reg(ctx, pattern3_1);
@@ -608,7 +632,7 @@ pub fn constructor_with_flags<C: Context>(
                     inst2: ref pattern3_1,
                     result: pattern3_2,
                 } => {
-                    // Rule at src/prelude.isle line 384.
+                    // Rule at src/prelude.isle line 421.
                     let expr0_0 = C::emit(ctx, pattern1_0);
                     let expr1_0 = C::emit(ctx, pattern3_1);
                     let expr2_0 = C::emit(ctx, pattern3_0);
@@ -627,7 +651,7 @@ pub fn constructor_with_flags<C: Context>(
                 result: pattern3_1,
             } = pattern2_0
             {
-                // Rule at src/prelude.isle line 372.
+                // Rule at src/prelude.isle line 409.
                 let expr0_0 = C::emit(ctx, pattern1_0);
                 let expr1_0 = C::emit(ctx, pattern3_0);
                 let expr2_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
@@ -647,7 +671,7 @@ pub fn constructor_with_flags_reg<C: Context>(
 ) -> Option<Reg> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/prelude.isle line 397.
+    // Rule at src/prelude.isle line 434.
     let expr0_0 = constructor_with_flags(ctx, pattern0_0, pattern1_0)?;
     let expr1_0: usize = 0;
     let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -746,12 +770,12 @@ pub fn constructor_put_in_xmm_mem_imm<C: Context>(ctx: &mut C, arg0: Value) -> O
     return Some(expr1_0);
 }
 
-// Generated as internal constructor for term value_gpr.
-pub fn constructor_value_gpr<C: Context>(ctx: &mut C, arg0: Gpr) -> Option<ValueRegs> {
+// Generated as internal constructor for term output_gpr.
+pub fn constructor_output_gpr<C: Context>(ctx: &mut C, arg0: Gpr) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     // Rule at src/isa/x64/inst.isle line 1014.
     let expr0_0 = C::gpr_to_reg(ctx, pattern0_0);
-    let expr1_0 = C::value_reg(ctx, expr0_0);
+    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
     return Some(expr1_0);
 }
 
@@ -766,12 +790,12 @@ pub fn constructor_value_gprs<C: Context>(ctx: &mut C, arg0: Gpr, arg1: Gpr) ->
     return Some(expr2_0);
 }
 
-// Generated as internal constructor for term value_xmm.
-pub fn constructor_value_xmm<C: Context>(ctx: &mut C, arg0: Xmm) -> Option<ValueRegs> {
+// Generated as internal constructor for term output_xmm.
+pub fn constructor_output_xmm<C: Context>(ctx: &mut C, arg0: Xmm) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     // Rule at src/isa/x64/inst.isle line 1024.
     let expr0_0 = C::xmm_to_reg(ctx, pattern0_0);
-    let expr1_0 = C::value_reg(ctx, expr0_0);
+    let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
     return Some(expr1_0);
 }
 
@@ -3442,7 +3466,7 @@ pub fn constructor_synthetic_amode_to_xmm_mem<C: Context>(
 }
 
 // Generated as internal constructor for term lower.
-pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueRegs> {
+pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<InstOutput> {
     let pattern0_0 = arg0;
     let pattern1_0 = C::inst_data(ctx, pattern0_0);
     match &pattern1_0 {
@@ -3455,7 +3479,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 // Rule at src/isa/x64/lower.isle line 46.
                 let expr0_0: Type = F32;
                 let expr1_0 = constructor_imm(ctx, expr0_0, pattern4_0)?;
-                let expr2_0 = C::value_reg(ctx, expr1_0);
+                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                 return Some(expr2_0);
             }
         }
@@ -3468,7 +3492,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 // Rule at src/isa/x64/lower.isle line 51.
                 let expr0_0: Type = F64;
                 let expr1_0 = constructor_imm(ctx, expr0_0, pattern4_0)?;
-                let expr2_0 = C::value_reg(ctx, expr1_0);
+                let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                 return Some(expr2_0);
             }
         }
@@ -3478,13 +3502,13 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
         } => {
             match pattern2_0 {
                 &Opcode::Trap => {
-                    // Rule at src/isa/x64/lower.isle line 1444.
+                    // Rule at src/isa/x64/lower.isle line 1435.
                     let expr0_0 = constructor_ud2(ctx, pattern2_1)?;
                     let expr1_0 = constructor_safepoint(ctx, &expr0_0)?;
                     return Some(expr1_0);
                 }
                 &Opcode::ResumableTrap => {
-                    // Rule at src/isa/x64/lower.isle line 1449.
+                    // Rule at src/isa/x64/lower.isle line 1440.
                     let expr0_0 = constructor_ud2(ctx, pattern2_1)?;
                     let expr1_0 = constructor_safepoint(ctx, &expr0_0)?;
                     return Some(expr1_0);
@@ -3501,12 +3525,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 let (pattern4_0, pattern4_1) = C::unpack_value_array_2(ctx, pattern2_1);
                 let pattern5_0 = C::value_type(ctx, pattern4_0);
                 let pattern6_0 = C::u8_from_uimm8(ctx, pattern2_2);
-                // Rule at src/isa/x64/lower.isle line 1311.
+                // Rule at src/isa/x64/lower.isle line 1302.
                 let expr0_0 = constructor_put_in_xmm(ctx, pattern4_0)?;
                 let expr1_0 = C::put_in_reg_mem(ctx, pattern4_1);
                 let expr2_0 =
                     constructor_vec_insert_lane(ctx, pattern5_0, expr0_0, &expr1_0, pattern6_0)?;
-                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                 return Some(expr3_0);
             }
         }
@@ -3531,7 +3555,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: u64 = 0;
                             let expr5_0 = constructor_imm(ctx, expr3_0, expr4_0)?;
                             let expr6_0 = C::value_regs(ctx, expr2_0, expr5_0);
-                            return Some(expr6_0);
+                            let expr7_0 = C::output(ctx, expr6_0);
+                            return Some(expr7_0);
                         }
                         if pattern5_1 == false {
                             // Rule at src/isa/x64/lower.isle line 34.
@@ -3542,7 +3567,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr4_0: u64 = 0;
                             let expr5_0 = constructor_imm(ctx, expr3_0, expr4_0)?;
                             let expr6_0 = C::value_regs(ctx, expr2_0, expr5_0);
-                            return Some(expr6_0);
+                            let expr7_0 = C::output(ctx, expr6_0);
+                            return Some(expr7_0);
                         }
                     }
                 }
@@ -3553,7 +3579,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 353.
+                            // Rule at src/isa/x64/lower.isle line 344.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3564,11 +3590,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr7_0 = C::gpr_to_gpr_mem_imm(ctx, expr5_0);
                             let expr8_0 = constructor_x64_and(ctx, expr6_0, expr2_0, &expr7_0)?;
                             let expr9_0 = constructor_value_gprs(ctx, expr8_0, expr4_0)?;
-                            return Some(expr9_0);
+                            let expr10_0 = C::output(ctx, expr9_0);
+                            return Some(expr10_0);
                         }
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 419.
+                            // Rule at src/isa/x64/lower.isle line 410.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3579,11 +3606,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr7_0 = C::gpr_to_gpr_mem_imm(ctx, expr5_0);
                             let expr8_0 = constructor_or(ctx, expr6_0, expr2_0, &expr7_0)?;
                             let expr9_0 = constructor_value_gprs(ctx, expr8_0, expr4_0)?;
-                            return Some(expr9_0);
+                            let expr10_0 = C::output(ctx, expr9_0);
+                            return Some(expr10_0);
                         }
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 477.
+                            // Rule at src/isa/x64/lower.isle line 468.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3594,7 +3622,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr7_0 = C::gpr_to_gpr_mem_imm(ctx, expr5_0);
                             let expr8_0 = constructor_xor(ctx, expr6_0, expr2_0, &expr7_0)?;
                             let expr9_0 = constructor_value_gprs(ctx, expr8_0, expr4_0)?;
-                            return Some(expr9_0);
+                            let expr10_0 = C::output(ctx, expr9_0);
+                            return Some(expr10_0);
                         }
                         _ => {}
                     }
@@ -3604,9 +3633,10 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     arg: pattern5_1,
                 } => {
                     if let &Opcode::Bnot = pattern5_0 {
-                        // Rule at src/isa/x64/lower.isle line 1278.
+                        // Rule at src/isa/x64/lower.isle line 1269.
                         let expr0_0 = constructor_i128_not(ctx, pattern5_1)?;
-                        return Some(expr0_0);
+                        let expr1_0 = C::output(ctx, expr0_0);
+                        return Some(expr1_0);
                     }
                 }
                 _ => {}
@@ -3628,7 +3658,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr3_0: u64 = 0;
                         let expr4_0 = constructor_imm(ctx, expr2_0, expr3_0)?;
                         let expr5_0 = C::value_regs(ctx, expr1_0, expr4_0);
-                        return Some(expr5_0);
+                        let expr6_0 = C::output(ctx, expr5_0);
+                        return Some(expr6_0);
                     }
                 }
                 &InstructionData::Binary {
@@ -3659,11 +3690,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr15_0 =
                                 constructor_adc_paired(ctx, expr13_0, expr4_0, &expr14_0)?;
                             let expr16_0 = constructor_with_flags(ctx, &expr12_0, &expr15_0)?;
-                            return Some(expr16_0);
+                            let expr17_0 = C::output(ctx, expr16_0);
+                            return Some(expr17_0);
                         }
                         &Opcode::Isub => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 266.
+                            // Rule at src/isa/x64/lower.isle line 257.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3684,11 +3716,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr15_0 =
                                 constructor_sbb_paired(ctx, expr13_0, expr4_0, &expr14_0)?;
                             let expr16_0 = constructor_with_flags(ctx, &expr12_0, &expr15_0)?;
-                            return Some(expr16_0);
+                            let expr17_0 = C::output(ctx, expr16_0);
+                            return Some(expr17_0);
                         }
                         &Opcode::Imul => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 966.
+                            // Rule at src/isa/x64/lower.isle line 957.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3719,11 +3752,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr27_0 = C::gpr_to_gpr_mem_imm(ctx, expr25_0);
                             let expr28_0 = constructor_add(ctx, expr26_0, expr18_0, &expr27_0)?;
                             let expr29_0 = constructor_value_gprs(ctx, expr23_0, expr28_0)?;
-                            return Some(expr29_0);
+                            let expr30_0 = C::output(ctx, expr29_0);
+                            return Some(expr30_0);
                         }
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 343.
+                            // Rule at src/isa/x64/lower.isle line 334.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3741,19 +3775,21 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr14_0 = C::gpr_to_gpr_mem_imm(ctx, expr9_0);
                             let expr15_0 = constructor_x64_and(ctx, expr13_0, expr4_0, &expr14_0)?;
                             let expr16_0 = constructor_value_gprs(ctx, expr12_0, expr15_0)?;
-                            return Some(expr16_0);
+                            let expr17_0 = C::output(ctx, expr16_0);
+                            return Some(expr17_0);
                         }
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 416.
+                            // Rule at src/isa/x64/lower.isle line 407.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0 = C::put_in_regs(ctx, pattern7_1);
                             let expr2_0 = constructor_or_i128(ctx, expr0_0, expr1_0)?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 467.
+                            // Rule at src/isa/x64/lower.isle line 458.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3771,11 +3807,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr14_0 = C::gpr_to_gpr_mem_imm(ctx, expr9_0);
                             let expr15_0 = constructor_xor(ctx, expr13_0, expr4_0, &expr14_0)?;
                             let expr16_0 = constructor_value_gprs(ctx, expr12_0, expr15_0)?;
-                            return Some(expr16_0);
+                            let expr17_0 = C::output(ctx, expr16_0);
+                            return Some(expr17_0);
                         }
                         &Opcode::Rotl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 839.
+                            // Rule at src/isa/x64/lower.isle line 830.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                             let expr2_0 = constructor_shl_i128(ctx, expr0_0, expr1_0)?;
@@ -3788,11 +3825,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr9_0 = constructor_sub(ctx, expr3_0, expr7_0, &expr8_0)?;
                             let expr10_0 = constructor_shr_i128(ctx, expr0_0, expr9_0)?;
                             let expr11_0 = constructor_or_i128(ctx, expr2_0, expr10_0)?;
-                            return Some(expr11_0);
+                            let expr12_0 = C::output(ctx, expr11_0);
+                            return Some(expr12_0);
                         }
                         &Opcode::Rotr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 879.
+                            // Rule at src/isa/x64/lower.isle line 870.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                             let expr2_0 = constructor_shr_i128(ctx, expr0_0, expr1_0)?;
@@ -3805,31 +3843,35 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr9_0 = constructor_sub(ctx, expr3_0, expr7_0, &expr8_0)?;
                             let expr10_0 = constructor_shl_i128(ctx, expr0_0, expr9_0)?;
                             let expr11_0 = constructor_or_i128(ctx, expr2_0, expr10_0)?;
-                            return Some(expr11_0);
+                            let expr12_0 = C::output(ctx, expr11_0);
+                            return Some(expr12_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 531.
+                            // Rule at src/isa/x64/lower.isle line 522.
                             let expr0_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr2_0 = constructor_shl_i128(ctx, expr1_0, expr0_0)?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 632.
+                            // Rule at src/isa/x64/lower.isle line 623.
                             let expr0_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr2_0 = constructor_shr_i128(ctx, expr1_0, expr0_0)?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 737.
+                            // Rule at src/isa/x64/lower.isle line 728.
                             let expr0_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr2_0 = constructor_sar_i128(ctx, expr1_0, expr0_0)?;
-                            return Some(expr2_0);
+                            let expr3_0 = C::output(ctx, expr2_0);
+                            return Some(expr3_0);
                         }
                         _ => {}
                     }
@@ -3839,9 +3881,10 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     arg: pattern5_1,
                 } => {
                     if let &Opcode::Bnot = pattern5_0 {
-                        // Rule at src/isa/x64/lower.isle line 1275.
+                        // Rule at src/isa/x64/lower.isle line 1266.
                         let expr0_0 = constructor_i128_not(ctx, pattern5_1)?;
-                        return Some(expr0_0);
+                        let expr1_0 = C::output(ctx, expr0_0);
+                        return Some(expr1_0);
                     }
                 }
                 &InstructionData::BinaryImm64 {
@@ -3851,7 +3894,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     if let &Opcode::IaddImm = pattern5_0 {
                         let pattern7_0 = C::u64_from_imm64(ctx, pattern5_2);
-                        // Rule at src/isa/x64/lower.isle line 219.
+                        // Rule at src/isa/x64/lower.isle line 210.
                         let expr0_0 = C::put_in_regs(ctx, pattern5_1);
                         let expr1_0: usize = 0;
                         let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -3870,7 +3913,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr14_0 = C::gpr_mem_imm_new(ctx, &expr13_0);
                         let expr15_0 = constructor_adc_paired(ctx, expr11_0, expr4_0, &expr14_0)?;
                         let expr16_0 = constructor_with_flags(ctx, &expr10_0, &expr15_0)?;
-                        return Some(expr16_0);
+                        let expr17_0 = C::output(ctx, expr16_0);
+                        return Some(expr17_0);
                     }
                 }
                 _ => {}
@@ -3886,43 +3930,43 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Imin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1411.
+                            // Rule at src/isa/x64/lower.isle line 1402.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminsb(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1433.
+                            // Rule at src/isa/x64/lower.isle line 1424.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminub(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1400.
+                            // Rule at src/isa/x64/lower.isle line 1391.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxsb(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1422.
+                            // Rule at src/isa/x64/lower.isle line 1413.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxub(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 543.
+                            // Rule at src/isa/x64/lower.isle line 534.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
@@ -3936,12 +3980,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr10_0 = RegMem::Reg { reg: expr8_0 };
                             let expr11_0 = C::reg_mem_to_xmm_mem(ctx, &expr10_0);
                             let expr12_0 = constructor_sse_and(ctx, expr9_0, expr3_0, &expr11_0)?;
-                            let expr13_0 = constructor_value_xmm(ctx, expr12_0)?;
+                            let expr13_0 = constructor_output_xmm(ctx, expr12_0)?;
                             return Some(expr13_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 642.
+                            // Rule at src/isa/x64/lower.isle line 633.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
@@ -3955,13 +3999,13 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr10_0 = RegMem::Reg { reg: expr8_0 };
                             let expr11_0 = C::reg_mem_to_xmm_mem(ctx, &expr10_0);
                             let expr12_0 = constructor_sse_and(ctx, expr9_0, expr3_0, &expr11_0)?;
-                            let expr13_0 = constructor_value_xmm(ctx, expr12_0)?;
+                            let expr13_0 = constructor_output_xmm(ctx, expr12_0)?;
                             return Some(expr13_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             let pattern8_0 = C::value_type(ctx, pattern7_1);
-                            // Rule at src/isa/x64/lower.isle line 758.
+                            // Rule at src/isa/x64/lower.isle line 749.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::xmm_to_xmm_mem(ctx, expr0_0);
                             let expr2_0 = constructor_punpcklbw(ctx, expr0_0, &expr1_0)?;
@@ -3974,7 +4018,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr8_0 = constructor_psraw(ctx, expr4_0, &expr6_0)?;
                             let expr9_0 = C::xmm_to_xmm_mem(ctx, expr8_0);
                             let expr10_0 = constructor_packsswb(ctx, expr7_0, &expr9_0)?;
-                            let expr11_0 = constructor_value_xmm(ctx, expr10_0)?;
+                            let expr11_0 = constructor_output_xmm(ctx, expr10_0)?;
                             return Some(expr11_0);
                         }
                         _ => {}
@@ -3986,21 +4030,21 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     match pattern5_0 {
                         &Opcode::Ineg => {
-                            // Rule at src/isa/x64/lower.isle line 898.
+                            // Rule at src/isa/x64/lower.isle line 889.
                             let expr0_0: Type = I8X16;
                             let expr1_0: u64 = 0;
                             let expr2_0 = constructor_imm(ctx, expr0_0, expr1_0)?;
                             let expr3_0 = C::xmm_new(ctx, expr2_0);
                             let expr4_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr5_0 = constructor_psubb(ctx, expr3_0, &expr4_0)?;
-                            let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                            let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         &Opcode::Iabs => {
-                            // Rule at src/isa/x64/lower.isle line 1219.
+                            // Rule at src/isa/x64/lower.isle line 1210.
                             let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr1_0 = constructor_pabsb(ctx, &expr0_0)?;
-                            let expr2_0 = constructor_value_xmm(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_xmm(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         _ => {}
@@ -4019,68 +4063,68 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Imin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1414.
+                            // Rule at src/isa/x64/lower.isle line 1405.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminsw(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1436.
+                            // Rule at src/isa/x64/lower.isle line 1427.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminuw(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1403.
+                            // Rule at src/isa/x64/lower.isle line 1394.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxsw(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1425.
+                            // Rule at src/isa/x64/lower.isle line 1416.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxuw(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 585.
+                            // Rule at src/isa/x64/lower.isle line 576.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psllw(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 687.
+                            // Rule at src/isa/x64/lower.isle line 678.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psrlw(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 785.
+                            // Rule at src/isa/x64/lower.isle line 776.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psraw(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -4092,21 +4136,21 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     match pattern5_0 {
                         &Opcode::Ineg => {
-                            // Rule at src/isa/x64/lower.isle line 901.
+                            // Rule at src/isa/x64/lower.isle line 892.
                             let expr0_0: Type = I16X8;
                             let expr1_0: u64 = 0;
                             let expr2_0 = constructor_imm(ctx, expr0_0, expr1_0)?;
                             let expr3_0 = C::xmm_new(ctx, expr2_0);
                             let expr4_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr5_0 = constructor_psubw(ctx, expr3_0, &expr4_0)?;
-                            let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                            let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         &Opcode::Iabs => {
-                            // Rule at src/isa/x64/lower.isle line 1222.
+                            // Rule at src/isa/x64/lower.isle line 1213.
                             let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr1_0 = constructor_pabsw(ctx, &expr0_0)?;
-                            let expr2_0 = constructor_value_xmm(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_xmm(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         _ => {}
@@ -4125,68 +4169,68 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Imin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1417.
+                            // Rule at src/isa/x64/lower.isle line 1408.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminsd(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1439.
+                            // Rule at src/isa/x64/lower.isle line 1430.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pminud(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1406.
+                            // Rule at src/isa/x64/lower.isle line 1397.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxsd(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Umax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1428.
+                            // Rule at src/isa/x64/lower.isle line 1419.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_pmaxud(ctx, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 588.
+                            // Rule at src/isa/x64/lower.isle line 579.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_pslld(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 690.
+                            // Rule at src/isa/x64/lower.isle line 681.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psrld(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 788.
+                            // Rule at src/isa/x64/lower.isle line 779.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psrad(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -4198,21 +4242,21 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     match pattern5_0 {
                         &Opcode::Ineg => {
-                            // Rule at src/isa/x64/lower.isle line 904.
+                            // Rule at src/isa/x64/lower.isle line 895.
                             let expr0_0: Type = I32X4;
                             let expr1_0: u64 = 0;
                             let expr2_0 = constructor_imm(ctx, expr0_0, expr1_0)?;
                             let expr3_0 = C::xmm_new(ctx, expr2_0);
                             let expr4_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr5_0 = constructor_psubd(ctx, expr3_0, &expr4_0)?;
-                            let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                            let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         &Opcode::Iabs => {
-                            // Rule at src/isa/x64/lower.isle line 1225.
+                            // Rule at src/isa/x64/lower.isle line 1216.
                             let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr1_0 = constructor_pabsd(ctx, &expr0_0)?;
-                            let expr2_0 = constructor_value_xmm(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_xmm(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         _ => {}
@@ -4231,27 +4275,27 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 591.
+                            // Rule at src/isa/x64/lower.isle line 582.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psllq(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 693.
+                            // Rule at src/isa/x64/lower.isle line 684.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = C::put_in_reg_mem_imm(ctx, pattern7_1);
                             let expr2_0 = constructor_mov_rmi_to_xmm(ctx, &expr1_0)?;
                             let expr3_0 = constructor_psrlq(ctx, expr0_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 799.
+                            // Rule at src/isa/x64/lower.isle line 790.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0: Type = I64;
                             let expr2_0: u8 = 0;
@@ -4269,7 +4313,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr14_0 = C::gpr_to_gpr_mem(ctx, expr12_0);
                             let expr15_0 =
                                 constructor_make_i64x2_from_lanes(ctx, &expr13_0, &expr14_0)?;
-                            let expr16_0 = constructor_value_xmm(ctx, expr15_0)?;
+                            let expr16_0 = constructor_output_xmm(ctx, expr15_0)?;
                             return Some(expr16_0);
                         }
                         _ => {}
@@ -4281,18 +4325,18 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     match pattern5_0 {
                         &Opcode::Ineg => {
-                            // Rule at src/isa/x64/lower.isle line 907.
+                            // Rule at src/isa/x64/lower.isle line 898.
                             let expr0_0: Type = I64X2;
                             let expr1_0: u64 = 0;
                             let expr2_0 = constructor_imm(ctx, expr0_0, expr1_0)?;
                             let expr3_0 = C::xmm_new(ctx, expr2_0);
                             let expr4_0 = constructor_put_in_xmm_mem(ctx, pattern5_1)?;
                             let expr5_0 = constructor_psubq(ctx, expr3_0, &expr4_0)?;
-                            let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                            let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                             return Some(expr6_0);
                         }
                         &Opcode::Iabs => {
-                            // Rule at src/isa/x64/lower.isle line 1239.
+                            // Rule at src/isa/x64/lower.isle line 1230.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern5_1)?;
                             let expr1_0: Type = I64X2;
                             let expr2_0: u64 = 0;
@@ -4302,7 +4346,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let expr6_0 = constructor_psubq(ctx, expr4_0, &expr5_0)?;
                             let expr7_0 = C::xmm_to_xmm_mem(ctx, expr0_0);
                             let expr8_0 = constructor_blendvpd(ctx, expr6_0, &expr7_0, expr6_0)?;
-                            let expr9_0 = constructor_value_xmm(ctx, expr8_0)?;
+                            let expr9_0 = constructor_output_xmm(ctx, expr8_0)?;
                             return Some(expr9_0);
                         }
                         _ => {}
@@ -4319,7 +4363,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Fabs = pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 1247.
+                    // Rule at src/isa/x64/lower.isle line 1238.
                     let expr0_0 = constructor_put_in_xmm(ctx, pattern5_1)?;
                     let expr1_0: Type = F32X4;
                     let expr2_0 = constructor_vector_all_ones(ctx, expr1_0)?;
@@ -4329,7 +4373,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr6_0 = constructor_psrld(ctx, expr2_0, &expr5_0)?;
                     let expr7_0 = C::xmm_to_xmm_mem(ctx, expr6_0);
                     let expr8_0 = constructor_andps(ctx, expr0_0, &expr7_0)?;
-                    let expr9_0 = constructor_value_xmm(ctx, expr8_0)?;
+                    let expr9_0 = constructor_output_xmm(ctx, expr8_0)?;
                     return Some(expr9_0);
                 }
             }
@@ -4342,7 +4386,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Fabs = pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 1253.
+                    // Rule at src/isa/x64/lower.isle line 1244.
                     let expr0_0 = constructor_put_in_xmm(ctx, pattern5_1)?;
                     let expr1_0: Type = F64X2;
                     let expr2_0 = constructor_vector_all_ones(ctx, expr1_0)?;
@@ -4352,7 +4396,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     let expr6_0 = constructor_psrlq(ctx, expr2_0, &expr5_0)?;
                     let expr7_0 = C::xmm_to_xmm_mem(ctx, expr6_0);
                     let expr8_0 = constructor_andpd(ctx, expr0_0, &expr7_0)?;
-                    let expr9_0 = constructor_value_xmm(ctx, expr8_0)?;
+                    let expr9_0 = constructor_output_xmm(ctx, expr8_0)?;
                     return Some(expr9_0);
                 }
             }
@@ -4366,7 +4410,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     // Rule at src/isa/x64/lower.isle line 56.
                     let expr0_0: u64 = 0;
                     let expr1_0 = constructor_imm(ctx, pattern2_0, expr0_0)?;
-                    let expr2_0 = C::value_reg(ctx, expr1_0);
+                    let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                     return Some(expr2_0);
                 }
             }
@@ -4376,11 +4420,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } => {
                 if let &Opcode::BandNot = pattern4_0 {
                     let (pattern6_0, pattern6_1) = C::unpack_value_array_2(ctx, pattern4_1);
-                    // Rule at src/isa/x64/lower.isle line 1214.
+                    // Rule at src/isa/x64/lower.isle line 1205.
                     let expr0_0 = constructor_put_in_xmm(ctx, pattern6_1)?;
                     let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern6_0)?;
                     let expr2_0 = constructor_sse_and_not(ctx, pattern2_0, expr0_0, &expr1_0)?;
-                    let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                    let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                     return Some(expr3_0);
                 }
             }
@@ -4404,7 +4448,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                     C::unpack_value_array_2(ctx, pattern9_1);
                                 match pattern9_2 {
                                     &FloatCC::Equal => {
-                                        // Rule at src/isa/x64/lower.isle line 1533.
+                                        // Rule at src/isa/x64/lower.isle line 1524.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::NZ;
@@ -4415,10 +4459,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr4_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr3_0)?;
-                                        return Some(expr4_0);
+                                        let expr5_0 = C::output(ctx, expr4_0);
+                                        return Some(expr5_0);
                                     }
                                     &FloatCC::GreaterThan => {
-                                        // Rule at src/isa/x64/lower.isle line 1485.
+                                        // Rule at src/isa/x64/lower.isle line 1476.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::NBE;
@@ -4427,10 +4472,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::GreaterThanOrEqual => {
-                                        // Rule at src/isa/x64/lower.isle line 1488.
+                                        // Rule at src/isa/x64/lower.isle line 1479.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::NB;
@@ -4439,10 +4485,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::LessThan => {
-                                        // Rule at src/isa/x64/lower.isle line 1508.
+                                        // Rule at src/isa/x64/lower.isle line 1499.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::NBE;
@@ -4451,10 +4498,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::LessThanOrEqual => {
-                                        // Rule at src/isa/x64/lower.isle line 1511.
+                                        // Rule at src/isa/x64/lower.isle line 1502.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::NB;
@@ -4463,10 +4511,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::NotEqual => {
-                                        // Rule at src/isa/x64/lower.isle line 1536.
+                                        // Rule at src/isa/x64/lower.isle line 1527.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::NZ;
@@ -4477,10 +4526,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr4_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr3_0)?;
-                                        return Some(expr4_0);
+                                        let expr5_0 = C::output(ctx, expr4_0);
+                                        return Some(expr5_0);
                                     }
                                     &FloatCC::Ordered => {
-                                        // Rule at src/isa/x64/lower.isle line 1479.
+                                        // Rule at src/isa/x64/lower.isle line 1470.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::NP;
@@ -4489,10 +4539,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::Unordered => {
-                                        // Rule at src/isa/x64/lower.isle line 1482.
+                                        // Rule at src/isa/x64/lower.isle line 1473.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::P;
@@ -4501,10 +4552,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::UnorderedOrGreaterThan => {
-                                        // Rule at src/isa/x64/lower.isle line 1514.
+                                        // Rule at src/isa/x64/lower.isle line 1505.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::B;
@@ -4513,10 +4565,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::UnorderedOrGreaterThanOrEqual => {
-                                        // Rule at src/isa/x64/lower.isle line 1517.
+                                        // Rule at src/isa/x64/lower.isle line 1508.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_0, pattern11_1)?;
                                         let expr1_0 = CC::BE;
@@ -4525,10 +4578,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::UnorderedOrLessThan => {
-                                        // Rule at src/isa/x64/lower.isle line 1491.
+                                        // Rule at src/isa/x64/lower.isle line 1482.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::B;
@@ -4537,10 +4591,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     &FloatCC::UnorderedOrLessThanOrEqual => {
-                                        // Rule at src/isa/x64/lower.isle line 1494.
+                                        // Rule at src/isa/x64/lower.isle line 1485.
                                         let expr0_0 =
                                             constructor_fpcmp(ctx, pattern11_1, pattern11_0)?;
                                         let expr1_0 = CC::BE;
@@ -4549,7 +4604,8 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         )?;
                                         let expr3_0 =
                                             constructor_with_flags(ctx, &expr0_0, &expr2_0)?;
-                                        return Some(expr3_0);
+                                        let expr4_0 = C::output(ctx, expr3_0);
+                                        return Some(expr4_0);
                                     }
                                     _ => {}
                                 }
@@ -4574,11 +4630,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 if let &Opcode::Imul = pattern9_0 {
                                     let (pattern11_0, pattern11_1) =
                                         C::unpack_value_array_2(ctx, pattern9_1);
-                                    // Rule at src/isa/x64/lower.isle line 1001.
+                                    // Rule at src/isa/x64/lower.isle line 992.
                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern11_0)?;
                                     let expr1_0 = constructor_put_in_xmm(ctx, pattern11_1)?;
                                     let expr2_0 = constructor_vpmullq(ctx, &expr0_0, expr1_0)?;
-                                    let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                    let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
@@ -4595,10 +4651,10 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     } = &pattern6_0
                     {
                         if let &Opcode::Iabs = pattern7_0 {
-                            // Rule at src/isa/x64/lower.isle line 1229.
+                            // Rule at src/isa/x64/lower.isle line 1220.
                             let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr1_0 = constructor_vpabsq(ctx, &expr0_0)?;
-                            let expr2_0 = constructor_value_xmm(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_xmm(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -4618,11 +4674,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::AvgRound => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 912.
+                                // Rule at src/isa/x64/lower.isle line 903.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_pavgb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::UaddSat => {
@@ -4632,7 +4688,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddusb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::SaddSat => {
@@ -4642,27 +4698,27 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddsb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::UsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 291.
+                                // Rule at src/isa/x64/lower.isle line 282.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubusb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::SsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 281.
+                                // Rule at src/isa/x64/lower.isle line 272.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubsb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Iadd => {
@@ -4672,17 +4728,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 249.
+                                // Rule at src/isa/x64/lower.isle line 240.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubb(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             _ => {}
@@ -4702,11 +4758,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::AvgRound => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 916.
+                                // Rule at src/isa/x64/lower.isle line 907.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_pavgw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::UaddSat => {
@@ -4716,7 +4772,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddusw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::SaddSat => {
@@ -4726,27 +4782,27 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddsw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::UsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 295.
+                                // Rule at src/isa/x64/lower.isle line 286.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubusw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::SsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 285.
+                                // Rule at src/isa/x64/lower.isle line 276.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubsw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Iadd => {
@@ -4756,17 +4812,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 253.
+                                // Rule at src/isa/x64/lower.isle line 244.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Imul => {
@@ -4815,14 +4871,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 8 {
                                                                                 if pattern23_1 == 16
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1089.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1080.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_pmovsxbw(ctx, &expr0_0)?;
                                                                                     let expr2_0 = constructor_put_in_xmm_mem(ctx, pattern20_1)?;
                                                                                     let expr3_0 = constructor_pmovsxbw(ctx, &expr2_0)?;
                                                                                     let expr4_0 = C::xmm_to_xmm_mem(ctx, expr3_0);
                                                                                     let expr5_0 = constructor_pmullw(ctx, expr1_0, &expr4_0)?;
-                                                                                    let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                                                                                    let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                                                                                     return Some(
                                                                                         expr6_0,
                                                                                     );
@@ -4871,7 +4927,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 8 {
                                                                                 if pattern23_1 == 16
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1049.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1040.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = C::xmm_to_xmm_mem(ctx, expr0_0);
                                                                                     let expr2_0: u8 = 8;
@@ -4888,7 +4944,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr13_0 = constructor_pmovsxbw(ctx, &expr12_0)?;
                                                                                     let expr14_0 = C::xmm_to_xmm_mem(ctx, expr13_0);
                                                                                     let expr15_0 = constructor_pmullw(ctx, expr6_0, &expr14_0)?;
-                                                                                    let expr16_0 = constructor_value_xmm(ctx, expr15_0)?;
+                                                                                    let expr16_0 = constructor_output_xmm(ctx, expr15_0)?;
                                                                                     return Some(
                                                                                         expr16_0,
                                                                                     );
@@ -4937,14 +4993,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 8 {
                                                                                 if pattern23_1 == 16
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1165.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1156.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_pmovzxbw(ctx, &expr0_0)?;
                                                                                     let expr2_0 = constructor_put_in_xmm_mem(ctx, pattern20_1)?;
                                                                                     let expr3_0 = constructor_pmovzxbw(ctx, &expr2_0)?;
                                                                                     let expr4_0 = C::xmm_to_xmm_mem(ctx, expr3_0);
                                                                                     let expr5_0 = constructor_pmullw(ctx, expr1_0, &expr4_0)?;
-                                                                                    let expr6_0 = constructor_value_xmm(ctx, expr5_0)?;
+                                                                                    let expr6_0 = constructor_output_xmm(ctx, expr5_0)?;
                                                                                     return Some(
                                                                                         expr6_0,
                                                                                     );
@@ -4993,7 +5049,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 8 {
                                                                                 if pattern23_1 == 16
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1125.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1116.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = C::xmm_to_xmm_mem(ctx, expr0_0);
                                                                                     let expr2_0: u8 = 8;
@@ -5010,7 +5066,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr13_0 = constructor_pmovzxbw(ctx, &expr12_0)?;
                                                                                     let expr14_0 = C::xmm_to_xmm_mem(ctx, expr13_0);
                                                                                     let expr15_0 = constructor_pmullw(ctx, expr6_0, &expr14_0)?;
-                                                                                    let expr16_0 = constructor_value_xmm(ctx, expr15_0)?;
+                                                                                    let expr16_0 = constructor_output_xmm(ctx, expr15_0)?;
                                                                                     return Some(
                                                                                         expr16_0,
                                                                                     );
@@ -5028,11 +5084,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 993.
+                                // Rule at src/isa/x64/lower.isle line 984.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_pmullw(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             _ => {}
@@ -5056,17 +5112,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddd(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 257.
+                                // Rule at src/isa/x64/lower.isle line 248.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubd(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Imul => {
@@ -5115,7 +5171,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 16 {
                                                                                 if pattern23_1 == 8
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1099.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1090.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_put_in_xmm(ctx, pattern20_1)?;
                                                                                     let expr2_0 = C::xmm_to_xmm_mem(ctx, expr1_0);
@@ -5124,7 +5180,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr5_0 = constructor_pmulhw(ctx, expr0_0, &expr4_0)?;
                                                                                     let expr6_0 = C::xmm_to_xmm_mem(ctx, expr5_0);
                                                                                     let expr7_0 = constructor_punpcklwd(ctx, expr3_0, &expr6_0)?;
-                                                                                    let expr8_0 = constructor_value_xmm(ctx, expr7_0)?;
+                                                                                    let expr8_0 = constructor_output_xmm(ctx, expr7_0)?;
                                                                                     return Some(
                                                                                         expr8_0,
                                                                                     );
@@ -5173,7 +5229,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 16 {
                                                                                 if pattern23_1 == 8
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1063.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1054.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_put_in_xmm(ctx, pattern20_1)?;
                                                                                     let expr2_0 = C::xmm_to_xmm_mem(ctx, expr1_0);
@@ -5182,7 +5238,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr5_0 = constructor_pmulhw(ctx, expr0_0, &expr4_0)?;
                                                                                     let expr6_0 = C::xmm_to_xmm_mem(ctx, expr5_0);
                                                                                     let expr7_0 = constructor_punpckhwd(ctx, expr3_0, &expr6_0)?;
-                                                                                    let expr8_0 = constructor_value_xmm(ctx, expr7_0)?;
+                                                                                    let expr8_0 = constructor_output_xmm(ctx, expr7_0)?;
                                                                                     return Some(
                                                                                         expr8_0,
                                                                                     );
@@ -5231,7 +5287,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 16 {
                                                                                 if pattern23_1 == 8
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1175.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1166.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_put_in_xmm(ctx, pattern20_1)?;
                                                                                     let expr2_0 = C::xmm_to_xmm_mem(ctx, expr1_0);
@@ -5240,7 +5296,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr5_0 = constructor_pmulhuw(ctx, expr0_0, &expr4_0)?;
                                                                                     let expr6_0 = C::xmm_to_xmm_mem(ctx, expr5_0);
                                                                                     let expr7_0 = constructor_punpcklwd(ctx, expr3_0, &expr6_0)?;
-                                                                                    let expr8_0 = constructor_value_xmm(ctx, expr7_0)?;
+                                                                                    let expr8_0 = constructor_output_xmm(ctx, expr7_0)?;
                                                                                     return Some(
                                                                                         expr8_0,
                                                                                     );
@@ -5289,7 +5345,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 16 {
                                                                                 if pattern23_1 == 8
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1139.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1130.
                                                                                     let expr0_0 = constructor_put_in_xmm(ctx, pattern12_1)?;
                                                                                     let expr1_0 = constructor_put_in_xmm(ctx, pattern20_1)?;
                                                                                     let expr2_0 = C::xmm_to_xmm_mem(ctx, expr1_0);
@@ -5298,7 +5354,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr5_0 = constructor_pmulhuw(ctx, expr0_0, &expr4_0)?;
                                                                                     let expr6_0 = C::xmm_to_xmm_mem(ctx, expr5_0);
                                                                                     let expr7_0 = constructor_punpckhwd(ctx, expr3_0, &expr6_0)?;
-                                                                                    let expr8_0 = constructor_value_xmm(ctx, expr7_0)?;
+                                                                                    let expr8_0 = constructor_output_xmm(ctx, expr7_0)?;
                                                                                     return Some(
                                                                                         expr8_0,
                                                                                     );
@@ -5316,11 +5372,11 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 996.
+                                // Rule at src/isa/x64/lower.isle line 987.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_pmulld(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             _ => {}
@@ -5344,17 +5400,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_paddq(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 261.
+                                // Rule at src/isa/x64/lower.isle line 252.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern9_1)?;
                                 let expr2_0 = constructor_psubq(ctx, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             &Opcode::Imul => {
@@ -5403,7 +5459,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 32 {
                                                                                 if pattern23_1 == 4
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1111.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1102.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0: u8 = 80;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -5414,7 +5470,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr7_0 = constructor_pshufd(ctx, &expr4_0, expr5_0, &expr6_0)?;
                                                                                     let expr8_0 = C::xmm_to_xmm_mem(ctx, expr7_0);
                                                                                     let expr9_0 = constructor_pmuldq(ctx, expr3_0, &expr8_0)?;
-                                                                                    let expr10_0 = constructor_value_xmm(ctx, expr9_0)?;
+                                                                                    let expr10_0 = constructor_output_xmm(ctx, expr9_0)?;
                                                                                     return Some(
                                                                                         expr10_0,
                                                                                     );
@@ -5463,7 +5519,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 32 {
                                                                                 if pattern23_1 == 4
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1075.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1066.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0: u8 = 250;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -5474,7 +5530,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr7_0 = constructor_pshufd(ctx, &expr4_0, expr5_0, &expr6_0)?;
                                                                                     let expr8_0 = C::xmm_to_xmm_mem(ctx, expr7_0);
                                                                                     let expr9_0 = constructor_pmuldq(ctx, expr3_0, &expr8_0)?;
-                                                                                    let expr10_0 = constructor_value_xmm(ctx, expr9_0)?;
+                                                                                    let expr10_0 = constructor_output_xmm(ctx, expr9_0)?;
                                                                                     return Some(
                                                                                         expr10_0,
                                                                                     );
@@ -5523,7 +5579,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 32 {
                                                                                 if pattern23_1 == 4
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1187.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1178.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0: u8 = 80;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -5534,7 +5590,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr7_0 = constructor_pshufd(ctx, &expr4_0, expr5_0, &expr6_0)?;
                                                                                     let expr8_0 = C::xmm_to_xmm_mem(ctx, expr7_0);
                                                                                     let expr9_0 = constructor_pmuludq(ctx, expr3_0, &expr8_0)?;
-                                                                                    let expr10_0 = constructor_value_xmm(ctx, expr9_0)?;
+                                                                                    let expr10_0 = constructor_output_xmm(ctx, expr9_0)?;
                                                                                     return Some(
                                                                                         expr10_0,
                                                                                     );
@@ -5583,7 +5639,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                             if pattern23_0 == 32 {
                                                                                 if pattern23_1 == 4
                                                                                 {
-                                                                                    // Rule at src/isa/x64/lower.isle line 1151.
+                                                                                    // Rule at src/isa/x64/lower.isle line 1142.
                                                                                     let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern12_1)?;
                                                                                     let expr1_0: u8 = 250;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -5594,7 +5650,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                                                                     let expr7_0 = constructor_pshufd(ctx, &expr4_0, expr5_0, &expr6_0)?;
                                                                                     let expr8_0 = C::xmm_to_xmm_mem(ctx, expr7_0);
                                                                                     let expr9_0 = constructor_pmuludq(ctx, expr3_0, &expr8_0)?;
-                                                                                    let expr10_0 = constructor_value_xmm(ctx, expr9_0)?;
+                                                                                    let expr10_0 = constructor_output_xmm(ctx, expr9_0)?;
                                                                                     return Some(
                                                                                         expr10_0,
                                                                                     );
@@ -5612,7 +5668,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 1027.
+                                // Rule at src/isa/x64/lower.isle line 1018.
                                 let expr0_0 = constructor_put_in_xmm(ctx, pattern9_0)?;
                                 let expr1_0 = constructor_put_in_xmm(ctx, pattern9_1)?;
                                 let expr2_0: u32 = 32;
@@ -5637,7 +5693,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr21_0 = constructor_pmuludq(ctx, expr0_0, &expr20_0)?;
                                 let expr22_0 = C::xmm_to_xmm_mem(ctx, expr19_0);
                                 let expr23_0 = constructor_paddq(ctx, expr21_0, &expr22_0)?;
-                                let expr24_0 = constructor_value_xmm(ctx, expr23_0)?;
+                                let expr24_0 = constructor_output_xmm(ctx, expr23_0)?;
                                 return Some(expr24_0);
                             }
                             _ => {}
@@ -5654,29 +5710,29 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 337.
+                            // Rule at src/isa/x64/lower.isle line 328.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_sse_and(ctx, pattern2_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 401.
+                            // Rule at src/isa/x64/lower.isle line 392.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_sse_or(ctx, pattern2_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 462.
+                            // Rule at src/isa/x64/lower.isle line 453.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_sse_xor(ctx, pattern2_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_xmm(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_xmm(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         _ => {}
@@ -5690,7 +5746,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bitselect => {
                             let (pattern7_0, pattern7_1, pattern7_2) =
                                 C::unpack_value_array_3(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1288.
+                            // Rule at src/isa/x64/lower.isle line 1279.
                             let expr0_0 = constructor_put_in_xmm(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm(ctx, pattern7_1)?;
                             let expr2_0 = C::xmm_to_xmm_mem(ctx, expr0_0);
@@ -5700,20 +5756,20 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 constructor_sse_and_not(ctx, pattern2_0, expr0_0, &expr4_0)?;
                             let expr6_0 = C::xmm_to_xmm_mem(ctx, expr3_0);
                             let expr7_0 = constructor_sse_or(ctx, pattern2_0, expr5_0, &expr6_0)?;
-                            let expr8_0 = constructor_value_xmm(ctx, expr7_0)?;
+                            let expr8_0 = constructor_output_xmm(ctx, expr7_0)?;
                             return Some(expr8_0);
                         }
                         &Opcode::Vselect => {
                             let (pattern7_0, pattern7_1, pattern7_2) =
                                 C::unpack_value_array_3(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1302.
+                            // Rule at src/isa/x64/lower.isle line 1293.
                             let expr0_0 = constructor_put_in_xmm_mem(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_xmm_mem(ctx, pattern7_1)?;
                             let expr2_0 = constructor_put_in_xmm(ctx, pattern7_2)?;
                             let expr3_0 = constructor_sse_blend(
                                 ctx, pattern2_0, &expr0_0, &expr1_0, expr2_0,
                             )?;
-                            let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -5724,12 +5780,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     arg: pattern5_1,
                 } => {
                     if let &Opcode::Bnot = pattern5_0 {
-                        // Rule at src/isa/x64/lower.isle line 1283.
+                        // Rule at src/isa/x64/lower.isle line 1274.
                         let expr0_0 = constructor_put_in_xmm(ctx, pattern5_1)?;
                         let expr1_0 = constructor_vector_all_ones(ctx, pattern2_0)?;
                         let expr2_0 = C::xmm_to_xmm_mem(ctx, expr1_0);
                         let expr3_0 = constructor_sse_xor(ctx, pattern2_0, expr0_0, &expr2_0)?;
-                        let expr4_0 = constructor_value_xmm(ctx, expr3_0)?;
+                        let expr4_0 = constructor_output_xmm(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                 }
@@ -5747,7 +5803,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let pattern7_0 = C::u64_from_imm64(ctx, pattern5_1);
                         // Rule at src/isa/x64/lower.isle line 10.
                         let expr0_0 = constructor_imm(ctx, pattern3_0, pattern7_0)?;
-                        let expr1_0 = C::value_reg(ctx, expr0_0);
+                        let expr1_0 = constructor_output_reg(ctx, expr0_0)?;
                         return Some(expr1_0);
                     }
                 }
@@ -5760,14 +5816,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             // Rule at src/isa/x64/lower.isle line 28.
                             let expr0_0: u64 = 1;
                             let expr1_0 = constructor_imm(ctx, pattern3_0, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         if pattern5_1 == false {
                             // Rule at src/isa/x64/lower.isle line 24.
                             let expr0_0: u64 = 0;
                             let expr1_0 = constructor_imm(ctx, pattern3_0, expr0_0)?;
-                            let expr2_0 = C::value_reg(ctx, expr1_0);
+                            let expr2_0 = constructor_output_reg(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                     }
@@ -5779,39 +5835,43 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     match pattern5_0 {
                         &Opcode::Imin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1392.
+                            // Rule at src/isa/x64/lower.isle line 1383.
                             let expr0_0 = CC::L;
                             let expr1_0 = constructor_cmp_and_choose(
                                 ctx, pattern3_0, &expr0_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr1_0);
+                            let expr2_0 = C::output(ctx, expr1_0);
+                            return Some(expr2_0);
                         }
                         &Opcode::Umin => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1386.
+                            // Rule at src/isa/x64/lower.isle line 1377.
                             let expr0_0 = CC::B;
                             let expr1_0 = constructor_cmp_and_choose(
                                 ctx, pattern3_0, &expr0_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr1_0);
+                            let expr2_0 = C::output(ctx, expr1_0);
+                            return Some(expr2_0);
                         }
                         &Opcode::Imax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1395.
+                            // Rule at src/isa/x64/lower.isle line 1386.
                             let expr0_0 = CC::NL;
                             let expr1_0 = constructor_cmp_and_choose(
                                 ctx, pattern3_0, &expr0_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr1_0);
+                            let expr2_0 = C::output(ctx, expr1_0);
+                            return Some(expr2_0);
                         }
                         &Opcode::Umax => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 1389.
+                            // Rule at src/isa/x64/lower.isle line 1380.
                             let expr0_0 = CC::NB;
                             let expr1_0 = constructor_cmp_and_choose(
                                 ctx, pattern3_0, &expr0_0, pattern7_0, pattern7_1,
                             )?;
-                            return Some(expr1_0);
+                            let expr2_0 = C::output(ctx, expr1_0);
+                            return Some(expr2_0);
                         }
                         &Opcode::Iadd => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
@@ -5820,7 +5880,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
@@ -5829,7 +5889,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
@@ -5837,7 +5897,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
@@ -5846,293 +5906,293 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             // Rule at src/isa/x64/lower.isle line 64.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Isub => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 237.
+                                // Rule at src/isa/x64/lower.isle line 228.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sub(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 242.
+                                // Rule at src/isa/x64/lower.isle line 233.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_sub(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 232.
+                            // Rule at src/isa/x64/lower.isle line 223.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_sub(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Imul => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 934.
+                                // Rule at src/isa/x64/lower.isle line 925.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_mul(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 946.
+                                // Rule at src/isa/x64/lower.isle line 937.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_mul(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 930.
+                                // Rule at src/isa/x64/lower.isle line 921.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_mul(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 940.
+                                // Rule at src/isa/x64/lower.isle line 931.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_mul(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 925.
+                            // Rule at src/isa/x64/lower.isle line 916.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_mul(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::IaddIfcout => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 173.
+                                // Rule at src/isa/x64/lower.isle line 171.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_unused_iflags(ctx)?;
-                                let expr3_0 = constructor_value_gprs(ctx, expr1_0, expr2_0)?;
+                                let expr2_0 = C::gpr_to_reg(ctx, expr1_0);
+                                let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 187.
+                                // Rule at src/isa/x64/lower.isle line 181.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_unused_iflags(ctx)?;
-                                let expr4_0 = constructor_value_gprs(ctx, expr2_0, expr3_0)?;
+                                let expr3_0 = C::gpr_to_reg(ctx, expr2_0);
+                                let expr4_0 = constructor_output_ifcout(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 168.
+                                // Rule at src/isa/x64/lower.isle line 167.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_unused_iflags(ctx)?;
-                                let expr3_0 = constructor_value_gprs(ctx, expr1_0, expr2_0)?;
+                                let expr2_0 = C::gpr_to_reg(ctx, expr1_0);
+                                let expr3_0 = constructor_output_ifcout(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 180.
+                                // Rule at src/isa/x64/lower.isle line 177.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_unused_iflags(ctx)?;
-                                let expr4_0 = constructor_value_gprs(ctx, expr2_0, expr3_0)?;
+                                let expr3_0 = C::gpr_to_reg(ctx, expr2_0);
+                                let expr4_0 = constructor_output_ifcout(ctx, expr3_0)?;
                                 return Some(expr4_0);
                             }
                             // Rule at src/isa/x64/lower.isle line 161.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_unused_iflags(ctx)?;
-                            let expr4_0 = constructor_value_gprs(ctx, expr2_0, expr3_0)?;
+                            let expr3_0 = C::gpr_to_reg(ctx, expr2_0);
+                            let expr4_0 = constructor_output_ifcout(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 326.
+                                // Rule at src/isa/x64/lower.isle line 317.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_x64_and(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 314.
+                                // Rule at src/isa/x64/lower.isle line 305.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 =
                                     constructor_x64_and(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 322.
+                                // Rule at src/isa/x64/lower.isle line 313.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_x64_and(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 309.
+                                // Rule at src/isa/x64/lower.isle line 300.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 =
                                     constructor_x64_and(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 304.
+                            // Rule at src/isa/x64/lower.isle line 295.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_x64_and(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 390.
+                                // Rule at src/isa/x64/lower.isle line 381.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_or(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 379.
+                                // Rule at src/isa/x64/lower.isle line 370.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_or(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 386.
+                                // Rule at src/isa/x64/lower.isle line 377.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_or(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 374.
+                                // Rule at src/isa/x64/lower.isle line 365.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_or(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 369.
+                            // Rule at src/isa/x64/lower.isle line 360.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_or(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 456.
+                                // Rule at src/isa/x64/lower.isle line 447.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_xor(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 445.
+                                // Rule at src/isa/x64/lower.isle line 436.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_1)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_xor(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 452.
+                                // Rule at src/isa/x64/lower.isle line 443.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_xor(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                                let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 440.
+                                // Rule at src/isa/x64/lower.isle line 431.
                                 let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                 let expr1_0 =
                                     constructor_sink_load_to_gpr_mem_imm(ctx, &pattern8_0)?;
                                 let expr2_0 = constructor_xor(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 435.
+                            // Rule at src/isa/x64/lower.isle line 426.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = constructor_put_in_gpr_mem_imm(ctx, pattern7_1)?;
                             let expr2_0 = constructor_xor(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 492.
+                            // Rule at src/isa/x64/lower.isle line 483.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                             let expr1_0 = C::put_masked_in_imm8_gpr(ctx, pattern7_1, pattern3_0);
                             let expr2_0 = constructor_shl(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                            let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                            let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                             return Some(expr3_0);
                         }
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 598.
+                            // Rule at src/isa/x64/lower.isle line 589.
                             let expr0_0 = ExtendKind::Zero;
                             let expr1_0 =
                                 constructor_extend_to_gpr(ctx, pattern7_0, pattern3_0, &expr0_0)?;
                             let expr2_0 = C::put_masked_in_imm8_gpr(ctx, pattern7_1, pattern3_0);
                             let expr3_0 = constructor_shr(ctx, pattern3_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_gpr(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_gpr(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         &Opcode::Sshr => {
                             let (pattern7_0, pattern7_1) = C::unpack_value_array_2(ctx, pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 700.
+                            // Rule at src/isa/x64/lower.isle line 691.
                             let expr0_0 = ExtendKind::Sign;
                             let expr1_0 =
                                 constructor_extend_to_gpr(ctx, pattern7_0, pattern3_0, &expr0_0)?;
                             let expr2_0 = C::put_masked_in_imm8_gpr(ctx, pattern7_1, pattern3_0);
                             let expr3_0 = constructor_sar(ctx, pattern3_0, expr1_0, &expr2_0)?;
-                            let expr4_0 = constructor_value_gpr(ctx, expr3_0)?;
+                            let expr4_0 = constructor_output_gpr(ctx, expr3_0)?;
                             return Some(expr4_0);
                         }
                         _ => {}
@@ -6144,17 +6204,17 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     match pattern5_0 {
                         &Opcode::Ineg => {
-                            // Rule at src/isa/x64/lower.isle line 893.
+                            // Rule at src/isa/x64/lower.isle line 884.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern5_1)?;
                             let expr1_0 = constructor_neg(ctx, pattern3_0, expr0_0)?;
-                            let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         &Opcode::Bnot => {
-                            // Rule at src/isa/x64/lower.isle line 1262.
+                            // Rule at src/isa/x64/lower.isle line 1253.
                             let expr0_0 = constructor_put_in_gpr(ctx, pattern5_1)?;
                             let expr1_0 = constructor_not(ctx, pattern3_0, expr0_0)?;
-                            let expr2_0 = constructor_value_gpr(ctx, expr1_0)?;
+                            let expr2_0 = constructor_output_gpr(ctx, expr1_0)?;
                             return Some(expr2_0);
                         }
                         _ => {}
@@ -6167,12 +6227,12 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                 } => {
                     if let &Opcode::IaddImm = pattern5_0 {
                         let pattern7_0 = C::u64_from_imm64(ctx, pattern5_2);
-                        // Rule at src/isa/x64/lower.isle line 205.
+                        // Rule at src/isa/x64/lower.isle line 196.
                         let expr0_0 = constructor_put_in_gpr(ctx, pattern5_1)?;
                         let expr1_0 = constructor_imm(ctx, pattern3_0, pattern7_0)?;
                         let expr2_0 = constructor_reg_to_gpr_mem_imm(ctx, expr1_0)?;
                         let expr3_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr2_0)?;
-                        let expr4_0 = constructor_value_gpr(ctx, expr3_0)?;
+                        let expr4_0 = constructor_output_gpr(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                 }
@@ -6198,23 +6258,23 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             {
                                 if let &Opcode::Iconst = pattern10_0 {
                                     let pattern12_0 = C::u64_from_imm64(ctx, pattern10_1);
-                                    // Rule at src/isa/x64/lower.isle line 832.
+                                    // Rule at src/isa/x64/lower.isle line 823.
                                     let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                     let expr1_0 =
                                         C::const_to_type_masked_imm8(ctx, pattern12_0, pattern3_0);
                                     let expr2_0 =
                                         constructor_x64_rotl(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                    let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                    let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
                         }
-                        // Rule at src/isa/x64/lower.isle line 826.
+                        // Rule at src/isa/x64/lower.isle line 817.
                         let expr0_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                         let expr1_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                         let expr2_0 = C::gpr_to_imm8_gpr(ctx, expr0_0);
                         let expr3_0 = constructor_x64_rotl(ctx, pattern3_0, expr1_0, &expr2_0)?;
-                        let expr4_0 = constructor_value_gpr(ctx, expr3_0)?;
+                        let expr4_0 = constructor_output_gpr(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     &Opcode::Rotr => {
@@ -6228,23 +6288,23 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             {
                                 if let &Opcode::Iconst = pattern10_0 {
                                     let pattern12_0 = C::u64_from_imm64(ctx, pattern10_1);
-                                    // Rule at src/isa/x64/lower.isle line 872.
+                                    // Rule at src/isa/x64/lower.isle line 863.
                                     let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                     let expr1_0 =
                                         C::const_to_type_masked_imm8(ctx, pattern12_0, pattern3_0);
                                     let expr2_0 =
                                         constructor_x64_rotr(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                    let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                    let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
                         }
-                        // Rule at src/isa/x64/lower.isle line 866.
+                        // Rule at src/isa/x64/lower.isle line 857.
                         let expr0_0 = constructor_lo_gpr(ctx, pattern7_1)?;
                         let expr1_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                         let expr2_0 = C::gpr_to_imm8_gpr(ctx, expr0_0);
                         let expr3_0 = constructor_x64_rotr(ctx, pattern3_0, expr1_0, &expr2_0)?;
-                        let expr4_0 = constructor_value_gpr(ctx, expr3_0)?;
+                        let expr4_0 = constructor_output_gpr(ctx, expr3_0)?;
                         return Some(expr4_0);
                     }
                     _ => {}
@@ -6270,18 +6330,18 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             {
                                 if let &Opcode::Iconst = pattern10_0 {
                                     let pattern12_0 = C::u64_from_imm64(ctx, pattern10_1);
-                                    // Rule at src/isa/x64/lower.isle line 818.
+                                    // Rule at src/isa/x64/lower.isle line 809.
                                     let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                     let expr1_0 =
                                         C::const_to_type_masked_imm8(ctx, pattern12_0, pattern3_0);
                                     let expr2_0 =
                                         constructor_x64_rotl(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                    let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                    let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
                         }
-                        // Rule at src/isa/x64/lower.isle line 814.
+                        // Rule at src/isa/x64/lower.isle line 805.
                         let expr0_0: Type = I32;
                         let expr1_0 = ExtendKind::Zero;
                         let expr2_0 =
@@ -6289,7 +6349,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr3_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                         let expr4_0 = C::gpr_to_imm8_gpr(ctx, expr2_0);
                         let expr5_0 = constructor_x64_rotl(ctx, pattern3_0, expr3_0, &expr4_0)?;
-                        let expr6_0 = constructor_value_gpr(ctx, expr5_0)?;
+                        let expr6_0 = constructor_output_gpr(ctx, expr5_0)?;
                         return Some(expr6_0);
                     }
                     &Opcode::Rotr => {
@@ -6303,18 +6363,18 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             {
                                 if let &Opcode::Iconst = pattern10_0 {
                                     let pattern12_0 = C::u64_from_imm64(ctx, pattern10_1);
-                                    // Rule at src/isa/x64/lower.isle line 858.
+                                    // Rule at src/isa/x64/lower.isle line 849.
                                     let expr0_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                                     let expr1_0 =
                                         C::const_to_type_masked_imm8(ctx, pattern12_0, pattern3_0);
                                     let expr2_0 =
                                         constructor_x64_rotr(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                    let expr3_0 = constructor_value_gpr(ctx, expr2_0)?;
+                                    let expr3_0 = constructor_output_gpr(ctx, expr2_0)?;
                                     return Some(expr3_0);
                                 }
                             }
                         }
-                        // Rule at src/isa/x64/lower.isle line 854.
+                        // Rule at src/isa/x64/lower.isle line 845.
                         let expr0_0: Type = I32;
                         let expr1_0 = ExtendKind::Zero;
                         let expr2_0 =
@@ -6322,7 +6382,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         let expr3_0 = constructor_put_in_gpr(ctx, pattern7_0)?;
                         let expr4_0 = C::gpr_to_imm8_gpr(ctx, expr2_0);
                         let expr5_0 = constructor_x64_rotr(ctx, pattern3_0, expr3_0, &expr4_0)?;
-                        let expr6_0 = constructor_value_gpr(ctx, expr5_0)?;
+                        let expr6_0 = constructor_output_gpr(ctx, expr5_0)?;
                         return Some(expr6_0);
                     }
                     _ => {}
@@ -6333,12 +6393,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
     return None;
 }
 
-// Generated as internal constructor for term unused_iflags.
-pub fn constructor_unused_iflags<C: Context>(ctx: &mut C) -> Option<Gpr> {
+// Generated as internal constructor for term output_ifcout.
+pub fn constructor_output_ifcout<C: Context>(ctx: &mut C, arg0: Reg) -> Option<InstOutput> {
+    let pattern0_0 = arg0;
     // Rule at src/isa/x64/lower.isle line 157.
-    let expr0_0 = C::temp_writable_gpr(ctx);
-    let expr1_0 = C::writable_gpr_to_gpr(ctx, expr0_0);
-    return Some(expr1_0);
+    let expr0_0 = C::value_reg(ctx, pattern0_0);
+    let expr1_0 = C::value_regs_invalid(ctx);
+    let expr2_0 = C::output_pair(ctx, expr0_0, expr1_0);
+    return Some(expr2_0);
 }
 
 // Generated as internal constructor for term sse_and.
@@ -6352,21 +6414,21 @@ pub fn constructor_sse_and<C: Context>(
     if pattern0_0 == F32X4 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 333.
+        // Rule at src/isa/x64/lower.isle line 324.
         let expr0_0 = constructor_andps(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if pattern0_0 == F64X2 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 334.
+        // Rule at src/isa/x64/lower.isle line 325.
         let expr0_0 = constructor_andpd(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if let Some((pattern1_0, pattern1_1)) = C::multi_lane(ctx, pattern0_0) {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 335.
+        // Rule at src/isa/x64/lower.isle line 326.
         let expr0_0 = constructor_pand(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
@@ -6384,21 +6446,21 @@ pub fn constructor_sse_or<C: Context>(
     if pattern0_0 == F32X4 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 397.
+        // Rule at src/isa/x64/lower.isle line 388.
         let expr0_0 = constructor_orps(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if pattern0_0 == F64X2 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 398.
+        // Rule at src/isa/x64/lower.isle line 389.
         let expr0_0 = constructor_orpd(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if let Some((pattern1_0, pattern1_1)) = C::multi_lane(ctx, pattern0_0) {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 399.
+        // Rule at src/isa/x64/lower.isle line 390.
         let expr0_0 = constructor_por(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
@@ -6413,7 +6475,7 @@ pub fn constructor_or_i128<C: Context>(
 ) -> Option<ValueRegs> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/isa/x64/lower.isle line 408.
+    // Rule at src/isa/x64/lower.isle line 399.
     let expr0_0: usize = 0;
     let expr1_0 = constructor_value_regs_get_gpr(ctx, pattern0_0, expr0_0)?;
     let expr2_0: usize = 1;
@@ -6440,7 +6502,7 @@ pub fn constructor_shl_i128<C: Context>(
 ) -> Option<ValueRegs> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/isa/x64/lower.isle line 498.
+    // Rule at src/isa/x64/lower.isle line 489.
     let expr0_0: usize = 0;
     let expr1_0 = constructor_value_regs_get_gpr(ctx, pattern0_0, expr0_0)?;
     let expr2_0: usize = 1;
@@ -6505,12 +6567,12 @@ pub fn constructor_ishl_i8x16_mask<C: Context>(
     let pattern0_0 = arg0;
     match pattern0_0 {
         &RegMemImm::Imm { simm32: pattern1_0 } => {
-            // Rule at src/isa/x64/lower.isle line 561.
+            // Rule at src/isa/x64/lower.isle line 552.
             let expr0_0 = C::ishl_i8x16_mask_for_const(ctx, pattern1_0);
             return Some(expr0_0);
         }
         &RegMemImm::Reg { reg: pattern1_0 } => {
-            // Rule at src/isa/x64/lower.isle line 570.
+            // Rule at src/isa/x64/lower.isle line 561.
             let expr0_0 = C::ishl_i8x16_mask_table(ctx);
             let expr1_0 = constructor_lea(ctx, &expr0_0)?;
             let expr2_0: Type = I64;
@@ -6527,7 +6589,7 @@ pub fn constructor_ishl_i8x16_mask<C: Context>(
         &RegMemImm::Mem {
             addr: ref pattern1_0,
         } => {
-            // Rule at src/isa/x64/lower.isle line 580.
+            // Rule at src/isa/x64/lower.isle line 571.
             let expr0_0: Type = I64;
             let expr1_0 = ExtKind::None;
             let expr2_0 = constructor_x64_load(ctx, expr0_0, pattern1_0, &expr1_0)?;
@@ -6548,7 +6610,7 @@ pub fn constructor_shr_i128<C: Context>(
 ) -> Option<ValueRegs> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/isa/x64/lower.isle line 605.
+    // Rule at src/isa/x64/lower.isle line 596.
     let expr0_0: usize = 0;
     let expr1_0 = constructor_value_regs_get_gpr(ctx, pattern0_0, expr0_0)?;
     let expr2_0: usize = 1;
@@ -6616,12 +6678,12 @@ pub fn constructor_ushr_i8x16_mask<C: Context>(
     let pattern0_0 = arg0;
     match pattern0_0 {
         &RegMemImm::Imm { simm32: pattern1_0 } => {
-            // Rule at src/isa/x64/lower.isle line 662.
+            // Rule at src/isa/x64/lower.isle line 653.
             let expr0_0 = C::ushr_i8x16_mask_for_const(ctx, pattern1_0);
             return Some(expr0_0);
         }
         &RegMemImm::Reg { reg: pattern1_0 } => {
-            // Rule at src/isa/x64/lower.isle line 671.
+            // Rule at src/isa/x64/lower.isle line 662.
             let expr0_0 = C::ushr_i8x16_mask_table(ctx);
             let expr1_0 = constructor_lea(ctx, &expr0_0)?;
             let expr2_0: Type = I64;
@@ -6638,7 +6700,7 @@ pub fn constructor_ushr_i8x16_mask<C: Context>(
         &RegMemImm::Mem {
             addr: ref pattern1_0,
         } => {
-            // Rule at src/isa/x64/lower.isle line 682.
+            // Rule at src/isa/x64/lower.isle line 673.
             let expr0_0: Type = I64;
             let expr1_0 = ExtKind::None;
             let expr2_0 = constructor_x64_load(ctx, expr0_0, pattern1_0, &expr1_0)?;
@@ -6659,7 +6721,7 @@ pub fn constructor_sar_i128<C: Context>(
 ) -> Option<ValueRegs> {
     let pattern0_0 = arg0;
     let pattern1_0 = arg1;
-    // Rule at src/isa/x64/lower.isle line 707.
+    // Rule at src/isa/x64/lower.isle line 698.
     let expr0_0: usize = 0;
     let expr1_0 = constructor_value_regs_get_gpr(ctx, pattern0_0, expr0_0)?;
     let expr2_0: usize = 1;
@@ -6729,7 +6791,7 @@ pub fn constructor_sshr_i8x16_bigger_shift<C: Context>(
     let pattern1_0 = arg1;
     match pattern1_0 {
         &RegMemImm::Imm { simm32: pattern2_0 } => {
-            // Rule at src/isa/x64/lower.isle line 771.
+            // Rule at src/isa/x64/lower.isle line 762.
             let expr0_0: u32 = 8;
             let expr1_0 = C::u32_add(ctx, pattern2_0, expr0_0);
             let expr2_0 = RegMemImm::Imm { simm32: expr1_0 };
@@ -6737,7 +6799,7 @@ pub fn constructor_sshr_i8x16_bigger_shift<C: Context>(
             return Some(expr3_0);
         }
         &RegMemImm::Reg { reg: pattern2_0 } => {
-            // Rule at src/isa/x64/lower.isle line 773.
+            // Rule at src/isa/x64/lower.isle line 764.
             let expr0_0 = C::gpr_new(ctx, pattern2_0);
             let expr1_0: u32 = 8;
             let expr2_0 = RegMemImm::Imm { simm32: expr1_0 };
@@ -6751,7 +6813,7 @@ pub fn constructor_sshr_i8x16_bigger_shift<C: Context>(
         &RegMemImm::Mem {
             addr: ref pattern2_0,
         } => {
-            // Rule at src/isa/x64/lower.isle line 777.
+            // Rule at src/isa/x64/lower.isle line 768.
             let expr0_0: u64 = 8;
             let expr1_0 = constructor_imm(ctx, pattern0_0, expr0_0)?;
             let expr2_0 = C::gpr_new(ctx, expr1_0);
@@ -6778,21 +6840,21 @@ pub fn constructor_sse_and_not<C: Context>(
     if pattern0_0 == F32X4 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 1203.
+        // Rule at src/isa/x64/lower.isle line 1194.
         let expr0_0 = constructor_andnps(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if pattern0_0 == F64X2 {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 1204.
+        // Rule at src/isa/x64/lower.isle line 1195.
         let expr0_0 = constructor_andnpd(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
     if let Some((pattern1_0, pattern1_1)) = C::multi_lane(ctx, pattern0_0) {
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
-        // Rule at src/isa/x64/lower.isle line 1205.
+        // Rule at src/isa/x64/lower.isle line 1196.
         let expr0_0 = constructor_pandn(ctx, pattern2_0, pattern3_0)?;
         return Some(expr0_0);
     }
@@ -6802,7 +6864,7 @@ pub fn constructor_sse_and_not<C: Context>(
 // Generated as internal constructor for term i128_not.
 pub fn constructor_i128_not<C: Context>(ctx: &mut C, arg0: Value) -> Option<ValueRegs> {
     let pattern0_0 = arg0;
-    // Rule at src/isa/x64/lower.isle line 1268.
+    // Rule at src/isa/x64/lower.isle line 1259.
     let expr0_0 = C::put_in_regs(ctx, pattern0_0);
     let expr1_0: usize = 0;
     let expr2_0 = constructor_value_regs_get_gpr(ctx, expr0_0, expr1_0)?;
@@ -6829,7 +6891,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1322.
+        // Rule at src/isa/x64/lower.isle line 1313.
         let expr0_0 = C::reg_mem_to_gpr_mem(ctx, pattern3_0);
         let expr1_0 = constructor_pinsrb(ctx, pattern2_0, &expr0_0, pattern4_0)?;
         return Some(expr1_0);
@@ -6838,7 +6900,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1326.
+        // Rule at src/isa/x64/lower.isle line 1317.
         let expr0_0 = C::reg_mem_to_gpr_mem(ctx, pattern3_0);
         let expr1_0 = constructor_pinsrw(ctx, pattern2_0, &expr0_0, pattern4_0)?;
         return Some(expr1_0);
@@ -6847,7 +6909,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1330.
+        // Rule at src/isa/x64/lower.isle line 1321.
         let expr0_0 = C::reg_mem_to_gpr_mem(ctx, pattern3_0);
         let expr1_0 = OperandSize::Size32;
         let expr2_0 = constructor_pinsrd(ctx, pattern2_0, &expr0_0, pattern4_0, &expr1_0)?;
@@ -6857,7 +6919,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1334.
+        // Rule at src/isa/x64/lower.isle line 1325.
         let expr0_0 = C::reg_mem_to_gpr_mem(ctx, pattern3_0);
         let expr1_0 = OperandSize::Size64;
         let expr2_0 = constructor_pinsrd(ctx, pattern2_0, &expr0_0, pattern4_0, &expr1_0)?;
@@ -6867,7 +6929,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1338.
+        // Rule at src/isa/x64/lower.isle line 1329.
         let expr0_0 = C::reg_mem_to_xmm_mem(ctx, pattern3_0);
         let expr1_0 = C::sse_insertps_lane_imm(ctx, pattern4_0);
         let expr2_0 = constructor_insertps(ctx, pattern2_0, &expr0_0, expr1_0)?;
@@ -6879,7 +6941,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         if let &RegMem::Reg { reg: pattern4_0 } = pattern3_0 {
             let pattern5_0 = arg3;
             if pattern5_0 == 0 {
-                // Rule at src/isa/x64/lower.isle line 1360.
+                // Rule at src/isa/x64/lower.isle line 1351.
                 let expr0_0 = constructor_reg_to_xmm_mem(ctx, pattern4_0)?;
                 let expr1_0 = constructor_movsd(ctx, pattern2_0, &expr0_0)?;
                 return Some(expr1_0);
@@ -6887,7 +6949,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         }
         let pattern4_0 = arg3;
         if pattern4_0 == 0 {
-            // Rule at src/isa/x64/lower.isle line 1362.
+            // Rule at src/isa/x64/lower.isle line 1353.
             let expr0_0 = SseOpcode::Movsd;
             let expr1_0 = C::reg_mem_to_xmm_mem(ctx, pattern3_0);
             let expr2_0 = constructor_xmm_unary_rm_r(ctx, &expr0_0, &expr1_0)?;
@@ -6896,7 +6958,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
             return Some(expr4_0);
         }
         if pattern4_0 == 1 {
-            // Rule at src/isa/x64/lower.isle line 1371.
+            // Rule at src/isa/x64/lower.isle line 1362.
             let expr0_0 = C::reg_mem_to_xmm_mem(ctx, pattern3_0);
             let expr1_0 = constructor_movlhps(ctx, pattern2_0, &expr0_0)?;
             return Some(expr1_0);
@@ -6918,7 +6980,7 @@ pub fn constructor_cmp_and_choose<C: Context>(
         let pattern2_0 = arg1;
         let pattern3_0 = arg2;
         let pattern4_0 = arg3;
-        // Rule at src/isa/x64/lower.isle line 1379.
+        // Rule at src/isa/x64/lower.isle line 1370.
         let expr0_0 = constructor_put_in_gpr(ctx, pattern3_0)?;
         let expr1_0 = constructor_put_in_gpr(ctx, pattern4_0)?;
         let expr2_0 = C::raw_operand_size_of_type(ctx, pattern1_0);
diff --git a/cranelift/codegen/src/machinst/isle.rs b/cranelift/codegen/src/machinst/isle.rs
index b8b8825635..70c995c7b2 100644
--- a/cranelift/codegen/src/machinst/isle.rs
+++ b/cranelift/codegen/src/machinst/isle.rs
@@ -1,9 +1,10 @@
-use crate::ir::{Inst, Value};
+use crate::ir::{types, Inst, Value};
 use crate::machinst::{get_output_reg, InsnOutput, LowerCtx, MachInst, RegRenamer};
 use alloc::boxed::Box;
 use alloc::vec::Vec;
 use regalloc::{Reg, Writable};
 use smallvec::SmallVec;
+use std::cell::Cell;
 
 pub use super::MachLabel;
 pub use crate::ir::{ExternalName, FuncRef, GlobalValue, SigRef};
@@ -18,6 +19,8 @@ pub type WritableReg = Writable<Reg>;
 pub type VecReg = Vec<Reg>;
 pub type VecWritableReg = Vec<WritableReg>;
 pub type ValueRegs = crate::machinst::ValueRegs<Reg>;
+pub type InstOutput = SmallVec<[ValueRegs; 2]>;
+pub type InstOutputBuilder = Cell<InstOutput>;
 pub type VecMachLabel = Vec<MachLabel>;
 pub type BoxExternalName = Box<ExternalName>;
 
@@ -64,6 +67,38 @@ macro_rules! isle_prelude_methods {
             ValueRegs::invalid()
         }
 
+        #[inline]
+        fn output_none(&mut self) -> InstOutput {
+            smallvec::smallvec![]
+        }
+
+        #[inline]
+        fn output(&mut self, regs: ValueRegs) -> InstOutput {
+            smallvec::smallvec![regs]
+        }
+
+        #[inline]
+        fn output_pair(&mut self, r1: ValueRegs, r2: ValueRegs) -> InstOutput {
+            smallvec::smallvec![r1, r2]
+        }
+
+        #[inline]
+        fn output_builder_new(&mut self) -> InstOutputBuilder {
+            std::cell::Cell::new(InstOutput::new())
+        }
+
+        #[inline]
+        fn output_builder_push(&mut self, builder: &InstOutputBuilder, regs: ValueRegs) -> Unit {
+            let mut vec = builder.take();
+            vec.push(regs);
+            builder.set(vec);
+        }
+
+        #[inline]
+        fn output_builder_finish(&mut self, builder: &InstOutputBuilder) -> InstOutput {
+            builder.take()
+        }
+
         #[inline]
         fn temp_writable_reg(&mut self, ty: Type) -> WritableReg {
             let value_regs = self.lower_ctx.alloc_tmp(ty);
@@ -363,7 +398,7 @@ pub(crate) fn lower_common<C, F, I, IF, const N: usize>(
 where
     C: LowerCtx,
     [(C::I, bool); N]: smallvec::Array<Item = (C::I, bool)>,
-    IF: Fn(&mut IsleContext<'_, C, F, I, N>, Inst) -> Option<ValueRegs>,
+    IF: Fn(&mut IsleContext<'_, C, F, I, N>, Inst) -> Option<InstOutput>,
 {
     // TODO: reuse the ISLE context across lowerings so we can reuse its
     // internal heap allocations.
@@ -375,22 +410,17 @@ where
     };
 
     let temp_regs = isle_lower(&mut isle_ctx, inst).ok_or(())?;
-    let mut temp_regs = temp_regs.regs().iter();
 
     #[cfg(debug_assertions)]
     {
-        let all_dsts_len = outputs
-            .iter()
-            .map(|out| get_output_reg(isle_ctx.lower_ctx, *out).len())
-            .sum();
         debug_assert_eq!(
             temp_regs.len(),
-            all_dsts_len,
-            "the number of temporary registers and destination registers do \
+            outputs.len(),
+            "the number of temporary values and destination values do \
          not match ({} != {}); ensure the correct registers are being \
          returned.",
             temp_regs.len(),
-            all_dsts_len,
+            outputs.len(),
         );
     }
 
@@ -399,12 +429,22 @@ where
     // registers they were assigned when their value was used as an operand in
     // earlier lowerings.
     let mut renamer = RegRenamer::default();
-    for output in outputs {
-        let dsts = get_output_reg(isle_ctx.lower_ctx, *output);
-        let ty = isle_ctx.lower_ctx.output_ty(output.insn, output.output);
-        let (_, tys) = <C::I>::rc_for_type(ty).unwrap();
-        for ((temp, dst), ty) in temp_regs.by_ref().zip(dsts.regs()).zip(tys) {
-            renamer.add_rename(*temp, dst.to_reg(), *ty);
+    for i in 0..outputs.len() {
+        let regs = temp_regs[i];
+        let dsts = get_output_reg(isle_ctx.lower_ctx, outputs[i]);
+        let ty = isle_ctx
+            .lower_ctx
+            .output_ty(outputs[i].insn, outputs[i].output);
+        if ty == types::IFLAGS || ty == types::FFLAGS {
+            // Flags values do not occupy any registers.
+            assert!(regs.len() == 0);
+        } else {
+            let (_, tys) = <C::I>::rc_for_type(ty).unwrap();
+            assert!(regs.len() == tys.len());
+            assert!(regs.len() == dsts.len());
+            for ((dst, temp), ty) in dsts.regs().iter().zip(regs.regs().iter()).zip(tys) {
+                renamer.add_rename(*temp, dst.to_reg(), *ty);
+            }
         }
     }
     for (inst, _) in isle_ctx.emitted_insts.iter_mut() {
diff --git a/cranelift/codegen/src/prelude.isle b/cranelift/codegen/src/prelude.isle
index c58a7113ce..0aa6a7ab11 100644
--- a/cranelift/codegen/src/prelude.isle
+++ b/cranelift/codegen/src/prelude.isle
@@ -38,6 +38,11 @@
 (type ValueList (primitive ValueList))
 (type ValueRegs (primitive ValueRegs))
 
+;; Instruction lowering result: a vector of `ValueRegs`.
+(type InstOutput (primitive InstOutput))
+;; (Mutable) builder to incrementally construct an `InstOutput`.
+(type InstOutputBuilder extern (enum))
+
 (decl u32_add (u32 u32) u32)
 (extern constructor u32_add u32_add)
 
@@ -64,6 +69,38 @@
 (decl value_regs_invalid () ValueRegs)
 (extern constructor value_regs_invalid value_regs_invalid)
 
+;; Construct an empty `InstOutput`.
+(decl output_none () InstOutput)
+(extern constructor output_none output_none)
+
+;; Construct a single-element `InstOutput`.
+(decl output (ValueRegs) InstOutput)
+(extern constructor output output)
+
+;; Construct a two-element `InstOutput`.
+(decl output_pair (ValueRegs ValueRegs) InstOutput)
+(extern constructor output_pair output_pair)
+
+;; Construct a single-element `InstOutput` from a single register.
+(decl output_reg (Reg) InstOutput)
+(rule (output_reg reg) (output (value_reg reg)))
+
+;; Construct a single-element `InstOutput` from a value.
+(decl output_value (Value) InstOutput)
+(rule (output_value val) (output (put_in_regs val)))
+
+;; Initially empty `InstOutput` builder.
+(decl output_builder_new () InstOutputBuilder)
+(extern constructor output_builder_new output_builder_new)
+
+;; Append a `ValueRegs` to an `InstOutput` under construction.
+(decl output_builder_push (InstOutputBuilder ValueRegs) Unit)
+(extern constructor output_builder_push output_builder_push)
+
+;; Finish building an `InstOutput` incrementally.
+(decl output_builder_finish (InstOutputBuilder) InstOutput)
+(extern constructor output_builder_finish output_builder_finish)
+
 ;; Get a temporary register for writing.
 (decl temp_writable_reg (Type) WritableReg)
 (extern constructor temp_writable_reg temp_writable_reg)
@@ -307,18 +344,18 @@
 
 (type SideEffectNoResult (enum (Inst (inst MInst))))
 
-;; Create an empty `ValueRegs`, but do emit the given side-effectful
+;; Create an empty `InstOutput`, but do emit the given side-effectful
 ;; instruction.
-(decl value_regs_none (SideEffectNoResult) ValueRegs)
-(rule (value_regs_none (SideEffectNoResult.Inst inst))
+(decl side_effect (SideEffectNoResult) InstOutput)
+(rule (side_effect (SideEffectNoResult.Inst inst))
       (let ((_ Unit (emit inst)))
-        (value_regs_invalid)))
+        (output_none)))
 
 ;; Similarly, but emit the side-effectful instruction as a safepoint.
-(decl safepoint (SideEffectNoResult) ValueRegs)
+(decl safepoint (SideEffectNoResult) InstOutput)
 (rule (safepoint (SideEffectNoResult.Inst inst))
       (let ((_ Unit (emit_safepoint inst)))
-        (value_regs_invalid)))
+        (output_none)))
 
 ;;;; Helpers for Working with Flags ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
@@ -438,3 +475,6 @@
 (convert Value Reg put_in_reg)
 (convert Value ValueRegs put_in_regs)
 (convert WritableReg Reg writable_reg_to_reg)
+(convert ValueRegs InstOutput output)
+(convert Reg InstOutput output_reg)
+(convert Value InstOutput output_value)