diff --git a/cranelift/codegen/src/isa/x64/lower.isle b/cranelift/codegen/src/isa/x64/lower.isle
index 9450982a00..9da45b854e 100644
--- a/cranelift/codegen/src/isa/x64/lower.isle
+++ b/cranelift/codegen/src/isa/x64/lower.isle
@@ -153,36 +153,56 @@
 
 ;;;; Rules for `iadd_ifcout` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+;; N.B.: the second output of `iadd_ifcout` is meant to be the
+;; `iflags` value containing the carry result. However, we plan to
+;; 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
+;; right thing, for now. For safety, we assert elsewhere that no one
+;; actually uses the register assigned to the SSA `iflags`-typed
+;; `Value`.
+
 ;; Add two registers.
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x y)))
-      (value_reg (add ty
-                      (put_in_reg x)
-                      (RegMemImm.Reg (put_in_reg y)))))
+      (let ((unused_iflags Reg (writable_reg_to_reg (temp_writable_reg $I64))))
+        (value_regs (add ty
+                         (put_in_reg x)
+                         (RegMemImm.Reg (put_in_reg y)))
+                    unused_iflags)))
 
 ;; Add a register and an immediate.
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x (simm32_from_value y))))
-      (value_reg (add ty (put_in_reg x) y)))
+      (let ((unused_iflags Reg (writable_reg_to_reg (temp_writable_reg $I64))))
+        (value_regs (add ty (put_in_reg x) y)
+                    unused_iflags)))
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout (simm32_from_value x) y)))
-      (value_reg (add ty (put_in_reg y) x)))
+      (let ((unused_iflags Reg (writable_reg_to_reg (temp_writable_reg $I64))))
+        (value_regs (add ty (put_in_reg y) x)
+                    unused_iflags)))
 
 ;; Add a register and memory.
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout x (sinkable_load y))))
-      (value_reg (add ty
-                      (put_in_reg x)
-                      (sink_load y))))
+      (let ((unused_iflags Reg (writable_reg_to_reg (temp_writable_reg $I64))))
+        (value_regs (add ty
+                         (put_in_reg x)
+                         (sink_load y))
+                    unused_iflags)))
 
 (rule (lower (has_type (fits_in_64 ty)
                        (iadd_ifcout (sinkable_load x) y)))
-      (value_reg (add ty
-                      (put_in_reg y)
-                      (sink_load x))))
+      (let ((unused_iflags Reg (writable_reg_to_reg (temp_writable_reg $I64))))
+        (value_regs (add ty
+                         (put_in_reg y)
+                         (sink_load x))
+                    unused_iflags)))
 
 ;; (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 85f349a988..8236a091d1 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 9c0563583e5500de00ec5e226edc0547ac3ea789c8d76f1da0401c80ec619320fdc9a6f17fd76bbcac74a5894f85385c1f51c900c2b83bc9906d03d0f29bf5cb
 src/prelude.isle 9bd1fcb6a3604a24cf2e05e6b7eb04dcb3b9dc8fa9a2f1c8f29c25b6e3bf7f679b3b1b72dff87501497b72bc30fc92fd755b898db7e03f380235fae931b6a74b
 src/isa/x64/inst.isle c93db8fe2819e952af629c4f4c31163545efcf5158f0747987eca30b5e42f2b6e75290bbccc72d7f44c2b43aab67fcbc339ef5a687918f796dd9317bad77a695
-src/isa/x64/lower.isle 333e1be62f602bb835a3cebc3299290a3d386438e9190d2db219263d974e097bfc3f1afdaac9401853806d21d548cad70bab2ffbc3b1cf5c3bebdd971a961f70
+src/isa/x64/lower.isle fe3dd6583a2415c7940b1ea414b14d4dd106f9cd46b605d52dcb0dfbe2d00bc4507925b3bb35e74ac3444138d256cd896b7c750957844d699397ffed21907d3a
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 3ee85cdcda..4cc73f99a4 100644
--- a/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs
+++ b/cranelift/codegen/src/isa/x64/lower/isle/generated_code.rs
@@ -1951,7 +1951,7 @@ 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 997.
+                // Rule at src/isa/x64/lower.isle line 1017.
                 let expr0_0 = C::put_in_reg(ctx, pattern4_0);
                 let expr1_0 = C::put_in_reg_mem(ctx, pattern4_1);
                 let expr2_0 =
@@ -2004,7 +2004,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 368.
+                            // Rule at src/isa/x64/lower.isle line 388.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2020,7 +2020,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 446.
+                            // Rule at src/isa/x64/lower.isle line 466.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2036,7 +2036,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 512.
+                            // Rule at src/isa/x64/lower.isle line 532.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2106,7 +2106,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &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 286.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2130,7 +2130,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Imul => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 696.
+                            // Rule at src/isa/x64/lower.isle line 716.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2166,7 +2166,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 358.
+                            // Rule at src/isa/x64/lower.isle line 378.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2189,7 +2189,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 443.
+                            // Rule at src/isa/x64/lower.isle line 463.
                             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)?;
@@ -2198,7 +2198,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 502.
+                            // Rule at src/isa/x64/lower.isle line 522.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0: usize = 0;
                             let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2221,7 +2221,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Rotl => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 629.
+                            // Rule at src/isa/x64/lower.isle line 649.
                             let expr0_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr1_0 = constructor_lo_reg(ctx, pattern7_1)?;
                             let expr2_0 = constructor_shl_i128(ctx, expr0_0, expr1_0)?;
@@ -2238,7 +2238,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Ishl => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 562.
+                            // Rule at src/isa/x64/lower.isle line 582.
                             let expr0_0 = constructor_lo_reg(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr2_0 = constructor_shl_i128(ctx, expr1_0, expr0_0)?;
@@ -2247,7 +2247,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Ushr => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 608.
+                            // Rule at src/isa/x64/lower.isle line 628.
                             let expr0_0 = constructor_lo_reg(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_regs(ctx, pattern7_0);
                             let expr2_0 = constructor_shr_i128(ctx, expr1_0, expr0_0)?;
@@ -2263,7 +2263,7 @@ 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 212.
+                        // Rule at src/isa/x64/lower.isle line 232.
                         let expr0_0 = C::put_in_regs(ctx, pattern5_1);
                         let expr1_0: usize = 0;
                         let expr2_0 = C::value_regs_get(ctx, expr0_0, expr1_0);
@@ -2293,7 +2293,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Iabs = &pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 951.
+                    // Rule at src/isa/x64/lower.isle line 971.
                     let expr0_0 = C::put_in_reg_mem(ctx, pattern5_1);
                     let expr1_0 = constructor_pabsb(ctx, &expr0_0)?;
                     let expr2_0 = C::value_reg(ctx, expr1_0);
@@ -2309,7 +2309,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Iabs = &pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 954.
+                    // Rule at src/isa/x64/lower.isle line 974.
                     let expr0_0 = C::put_in_reg_mem(ctx, pattern5_1);
                     let expr1_0 = constructor_pabsw(ctx, &expr0_0)?;
                     let expr2_0 = C::value_reg(ctx, expr1_0);
@@ -2325,7 +2325,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Iabs = &pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 957.
+                    // Rule at src/isa/x64/lower.isle line 977.
                     let expr0_0 = C::put_in_reg_mem(ctx, pattern5_1);
                     let expr1_0 = constructor_pabsd(ctx, &expr0_0)?;
                     let expr2_0 = C::value_reg(ctx, expr1_0);
@@ -2341,7 +2341,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
             } = &pattern4_0
             {
                 if let &Opcode::Iabs = &pattern5_0 {
-                    // Rule at src/isa/x64/lower.isle line 971.
+                    // Rule at src/isa/x64/lower.isle line 991.
                     let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                     let expr1_0: Type = I64X2;
                     let expr2_0: u64 = 0;
@@ -2366,7 +2366,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &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 363.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_andps(ctx, expr0_0, &expr1_0)?;
@@ -2376,7 +2376,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &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 439.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_orps(ctx, expr0_0, &expr1_0)?;
@@ -2386,7 +2386,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::BandNot => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 940.
+                            // Rule at src/isa/x64/lower.isle line 960.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_0);
                             let expr2_0 = constructor_andnps(ctx, expr0_0, &expr1_0)?;
@@ -2401,7 +2401,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     arg: pattern5_1,
                 } => {
                     if let &Opcode::Fabs = &pattern5_0 {
-                        // Rule at src/isa/x64/lower.isle line 979.
+                        // Rule at src/isa/x64/lower.isle line 999.
                         let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                         let expr1_0: Type = F32X4;
                         let expr2_0 = constructor_vector_all_ones(ctx, expr1_0)?;
@@ -2428,7 +2428,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 347.
+                            // Rule at src/isa/x64/lower.isle line 367.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_andpd(ctx, expr0_0, &expr1_0)?;
@@ -2438,7 +2438,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 423.
+                            // Rule at src/isa/x64/lower.isle line 443.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_orpd(ctx, expr0_0, &expr1_0)?;
@@ -2448,7 +2448,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::BandNot => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 943.
+                            // Rule at src/isa/x64/lower.isle line 963.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_0);
                             let expr2_0 = constructor_andnpd(ctx, expr0_0, &expr1_0)?;
@@ -2463,7 +2463,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                     arg: pattern5_1,
                 } => {
                     if let &Opcode::Fabs = &pattern5_0 {
-                        // Rule at src/isa/x64/lower.isle line 984.
+                        // Rule at src/isa/x64/lower.isle line 1004.
                         let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                         let expr1_0: Type = F64X2;
                         let expr2_0 = constructor_vector_all_ones(ctx, expr1_0)?;
@@ -2506,7 +2506,7 @@ 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 731.
+                                    // Rule at src/isa/x64/lower.isle line 751.
                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern11_0);
                                     let expr1_0 = C::put_in_reg(ctx, pattern11_1);
                                     let expr2_0 = constructor_vpmullq(ctx, &expr0_0, expr1_0)?;
@@ -2527,7 +2527,7 @@ 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 961.
+                            // Rule at src/isa/x64/lower.isle line 981.
                             let expr0_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr1_0 = constructor_vpabsq(ctx, &expr0_0)?;
                             let expr2_0 = C::value_reg(ctx, expr1_0);
@@ -2550,7 +2550,7 @@ 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 639.
+                                // Rule at src/isa/x64/lower.isle line 659.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_pavgb(ctx, expr0_0, &expr1_0)?;
@@ -2580,7 +2580,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::UsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 293.
+                                // Rule at src/isa/x64/lower.isle line 313.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubusb(ctx, expr0_0, &expr1_0)?;
@@ -2590,7 +2590,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &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 301.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubsb(ctx, expr0_0, &expr1_0)?;
@@ -2610,7 +2610,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 245.
+                                // Rule at src/isa/x64/lower.isle line 265.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubb(ctx, expr0_0, &expr1_0)?;
@@ -2634,7 +2634,7 @@ 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 643.
+                                // Rule at src/isa/x64/lower.isle line 663.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_pavgw(ctx, expr0_0, &expr1_0)?;
@@ -2664,7 +2664,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::UsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 298.
+                                // Rule at src/isa/x64/lower.isle line 318.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubusw(ctx, expr0_0, &expr1_0)?;
@@ -2674,7 +2674,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::SsubSat => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 286.
+                                // Rule at src/isa/x64/lower.isle line 306.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubsw(ctx, expr0_0, &expr1_0)?;
@@ -2694,7 +2694,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 250.
+                                // Rule at src/isa/x64/lower.isle line 270.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubw(ctx, expr0_0, &expr1_0)?;
@@ -2747,7 +2747,7 @@ 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 819.
+                                                                                    // Rule at src/isa/x64/lower.isle line 839.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0 = constructor_pmovsxbw(ctx, &expr0_0)?;
                                                                                     let expr2_0 = C::put_in_reg_mem(ctx, pattern20_1);
@@ -2805,7 +2805,7 @@ 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 779.
+                                                                                    // Rule at src/isa/x64/lower.isle line 799.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = RegMem::Reg {
                                                                                         reg: expr0_0,
@@ -2881,7 +2881,7 @@ 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 895.
+                                                                                    // Rule at src/isa/x64/lower.isle line 915.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0 = constructor_pmovzxbw(ctx, &expr0_0)?;
                                                                                     let expr2_0 = C::put_in_reg_mem(ctx, pattern20_1);
@@ -2939,7 +2939,7 @@ 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 855.
+                                                                                    // Rule at src/isa/x64/lower.isle line 875.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = RegMem::Reg {
                                                                                         reg: expr0_0,
@@ -2984,7 +2984,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 723.
+                                // Rule at src/isa/x64/lower.isle line 743.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_pmullw(ctx, expr0_0, &expr1_0)?;
@@ -3018,7 +3018,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 255.
+                                // Rule at src/isa/x64/lower.isle line 275.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubd(ctx, expr0_0, &expr1_0)?;
@@ -3071,7 +3071,7 @@ 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 829.
+                                                                                    // Rule at src/isa/x64/lower.isle line 849.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = C::put_in_reg(ctx, pattern20_1);
                                                                                     let expr2_0 = RegMem::Reg {
@@ -3135,7 +3135,7 @@ 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 793.
+                                                                                    // Rule at src/isa/x64/lower.isle line 813.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = C::put_in_reg(ctx, pattern20_1);
                                                                                     let expr2_0 = RegMem::Reg {
@@ -3199,7 +3199,7 @@ 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 905.
+                                                                                    // Rule at src/isa/x64/lower.isle line 925.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = C::put_in_reg(ctx, pattern20_1);
                                                                                     let expr2_0 = RegMem::Reg {
@@ -3263,7 +3263,7 @@ 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 869.
+                                                                                    // Rule at src/isa/x64/lower.isle line 889.
                                                                                     let expr0_0 = C::put_in_reg(ctx, pattern12_1);
                                                                                     let expr1_0 = C::put_in_reg(ctx, pattern20_1);
                                                                                     let expr2_0 = RegMem::Reg {
@@ -3296,7 +3296,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 726.
+                                // Rule at src/isa/x64/lower.isle line 746.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_pmulld(ctx, expr0_0, &expr1_0)?;
@@ -3330,7 +3330,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             &Opcode::Isub => {
                                 let (pattern9_0, pattern9_1) =
                                     C::unpack_value_array_2(ctx, &pattern7_1);
-                                // Rule at src/isa/x64/lower.isle line 260.
+                                // Rule at src/isa/x64/lower.isle line 280.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg_mem(ctx, pattern9_1);
                                 let expr2_0 = constructor_psubq(ctx, expr0_0, &expr1_0)?;
@@ -3383,7 +3383,7 @@ 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 841.
+                                                                                    // Rule at src/isa/x64/lower.isle line 861.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0: u8 = 80;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -3445,7 +3445,7 @@ 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 805.
+                                                                                    // Rule at src/isa/x64/lower.isle line 825.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0: u8 = 250;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -3507,7 +3507,7 @@ 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 917.
+                                                                                    // Rule at src/isa/x64/lower.isle line 937.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0: u8 = 80;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -3569,7 +3569,7 @@ 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 881.
+                                                                                    // Rule at src/isa/x64/lower.isle line 901.
                                                                                     let expr0_0 = C::put_in_reg_mem(ctx, pattern12_1);
                                                                                     let expr1_0: u8 = 250;
                                                                                     let expr2_0 = OperandSize::Size32;
@@ -3600,7 +3600,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                         }
                                     }
                                 }
-                                // Rule at src/isa/x64/lower.isle line 757.
+                                // Rule at src/isa/x64/lower.isle line 777.
                                 let expr0_0 = C::put_in_reg(ctx, pattern9_0);
                                 let expr1_0 = C::put_in_reg(ctx, pattern9_1);
                                 let expr2_0: u32 = 32;
@@ -3640,7 +3640,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Band => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 351.
+                            // Rule at src/isa/x64/lower.isle line 371.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_pand(ctx, expr0_0, &expr1_0)?;
@@ -3650,7 +3650,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 427.
+                            // Rule at src/isa/x64/lower.isle line 447.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_por(ctx, expr0_0, &expr1_0)?;
@@ -3660,7 +3660,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::Bxor => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 497.
+                            // Rule at src/isa/x64/lower.isle line 517.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_1);
                             let expr2_0 = constructor_sse_xor(ctx, pattern2_0, expr0_0, &expr1_0)?;
@@ -3670,7 +3670,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                         &Opcode::BandNot => {
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
-                            // Rule at src/isa/x64/lower.isle line 946.
+                            // Rule at src/isa/x64/lower.isle line 966.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr1_0 = C::put_in_reg_mem(ctx, pattern7_0);
                             let expr2_0 = constructor_pandn(ctx, expr0_0, &expr1_0)?;
@@ -3685,7 +3685,7 @@ 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 992.
+                        // Rule at src/isa/x64/lower.isle line 1012.
                         let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                         let expr1_0 = constructor_vector_all_ones(ctx, pattern2_0)?;
                         let expr2_0 = RegMem::Reg { reg: expr1_0 };
@@ -3785,7 +3785,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             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 232.
+                                // Rule at src/isa/x64/lower.isle line 252.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_sub(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3793,14 +3793,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 237.
+                                // Rule at src/isa/x64/lower.isle line 257.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_sub(ctx, pattern3_0, expr0_0, &expr1_0)?;
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 225.
+                            // Rule at src/isa/x64/lower.isle line 245.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -3812,7 +3812,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             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 663.
+                                // Rule at src/isa/x64/lower.isle line 683.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_mul(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3820,7 +3820,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 675.
+                                // Rule at src/isa/x64/lower.isle line 695.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_mul(ctx, pattern3_0, expr0_0, &expr1_0)?;
@@ -3828,7 +3828,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 659.
+                                // Rule at src/isa/x64/lower.isle line 679.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_mul(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3836,14 +3836,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 669.
+                                // Rule at src/isa/x64/lower.isle line 689.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_mul(ctx, pattern3_0, expr0_0, &expr1_0)?;
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 652.
+                            // Rule at src/isa/x64/lower.isle line 672.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -3855,50 +3855,65 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             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 169.
-                                let expr0_0 = C::put_in_reg(ctx, pattern7_1);
-                                let expr1_0 =
-                                    constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
-                                return Some(expr2_0);
+                                // Rule at src/isa/x64/lower.isle line 183.
+                                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::put_in_reg(ctx, pattern7_1);
+                                let expr4_0 =
+                                    constructor_add(ctx, pattern3_0, expr3_0, &pattern8_0)?;
+                                let expr5_0 = C::value_regs(ctx, expr4_0, expr2_0);
+                                return Some(expr5_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 181.
-                                let expr0_0 = C::put_in_reg(ctx, pattern7_1);
-                                let expr1_0 = C::sink_load(ctx, &pattern8_0);
-                                let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
-                                return Some(expr3_0);
+                                // Rule at src/isa/x64/lower.isle line 199.
+                                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::put_in_reg(ctx, pattern7_1);
+                                let expr4_0 = C::sink_load(ctx, &pattern8_0);
+                                let expr5_0 = constructor_add(ctx, pattern3_0, expr3_0, &expr4_0)?;
+                                let expr6_0 = C::value_regs(ctx, expr5_0, expr2_0);
+                                return Some(expr6_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 165.
-                                let expr0_0 = C::put_in_reg(ctx, pattern7_0);
-                                let expr1_0 =
-                                    constructor_add(ctx, pattern3_0, expr0_0, &pattern8_0)?;
-                                let expr2_0 = C::value_reg(ctx, expr1_0);
-                                return Some(expr2_0);
+                                // Rule at src/isa/x64/lower.isle line 177.
+                                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::put_in_reg(ctx, pattern7_0);
+                                let expr4_0 =
+                                    constructor_add(ctx, pattern3_0, expr3_0, &pattern8_0)?;
+                                let expr5_0 = C::value_regs(ctx, expr4_0, expr2_0);
+                                return Some(expr5_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 175.
-                                let expr0_0 = C::put_in_reg(ctx, pattern7_0);
-                                let expr1_0 = C::sink_load(ctx, &pattern8_0);
-                                let expr2_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr1_0)?;
-                                let expr3_0 = C::value_reg(ctx, expr2_0);
-                                return Some(expr3_0);
+                                // Rule at src/isa/x64/lower.isle line 191.
+                                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::put_in_reg(ctx, pattern7_0);
+                                let expr4_0 = C::sink_load(ctx, &pattern8_0);
+                                let expr5_0 = constructor_add(ctx, pattern3_0, expr3_0, &expr4_0)?;
+                                let expr6_0 = C::value_regs(ctx, expr5_0, expr2_0);
+                                return Some(expr6_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 157.
-                            let expr0_0 = C::put_in_reg(ctx, pattern7_0);
-                            let expr1_0 = C::put_in_reg(ctx, pattern7_1);
-                            let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
-                            let expr3_0 = constructor_add(ctx, pattern3_0, expr0_0, &expr2_0)?;
-                            let expr4_0 = C::value_reg(ctx, expr3_0);
-                            return Some(expr4_0);
+                            // Rule at src/isa/x64/lower.isle line 167.
+                            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::put_in_reg(ctx, pattern7_0);
+                            let expr4_0 = C::put_in_reg(ctx, pattern7_1);
+                            let expr5_0 = RegMemImm::Reg { reg: expr4_0 };
+                            let expr6_0 = constructor_add(ctx, pattern3_0, expr3_0, &expr5_0)?;
+                            let expr7_0 = C::value_regs(ctx, expr6_0, expr2_0);
+                            return Some(expr7_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 335.
+                                // Rule at src/isa/x64/lower.isle line 355.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_m_and(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3906,7 +3921,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 321.
+                                // Rule at src/isa/x64/lower.isle line 341.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 =
@@ -3915,7 +3930,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 329.
+                                // Rule at src/isa/x64/lower.isle line 349.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_m_and(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3923,7 +3938,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 315.
+                                // Rule at src/isa/x64/lower.isle line 335.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 =
@@ -3931,7 +3946,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 308.
+                            // Rule at src/isa/x64/lower.isle line 328.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -3943,7 +3958,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             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 411.
+                                // Rule at src/isa/x64/lower.isle line 431.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_or(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3951,7 +3966,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 397.
+                                // Rule at src/isa/x64/lower.isle line 417.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_or(ctx, pattern3_0, expr0_0, &expr1_0)?;
@@ -3959,7 +3974,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 405.
+                                // Rule at src/isa/x64/lower.isle line 425.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_or(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3967,14 +3982,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 391.
+                                // Rule at src/isa/x64/lower.isle line 411.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_or(ctx, pattern3_0, expr0_0, &expr1_0)?;
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 384.
+                            // Rule at src/isa/x64/lower.isle line 404.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -3986,7 +4001,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             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 489.
+                                // Rule at src/isa/x64/lower.isle line 509.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 =
                                     constructor_xor(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -3994,7 +4009,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_0) {
-                                // Rule at src/isa/x64/lower.isle line 475.
+                                // Rule at src/isa/x64/lower.isle line 495.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_1);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_xor(ctx, pattern3_0, expr0_0, &expr1_0)?;
@@ -4002,7 +4017,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr3_0);
                             }
                             if let Some(pattern8_0) = C::simm32_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 483.
+                                // Rule at src/isa/x64/lower.isle line 503.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_xor(ctx, pattern3_0, expr0_0, &pattern8_0)?;
@@ -4010,14 +4025,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 return Some(expr2_0);
                             }
                             if let Some(pattern8_0) = C::sinkable_load(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 469.
+                                // Rule at src/isa/x64/lower.isle line 489.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 = C::sink_load(ctx, &pattern8_0);
                                 let expr2_0 = constructor_xor(ctx, pattern3_0, expr0_0, &expr1_0)?;
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 462.
+                            // Rule at src/isa/x64/lower.isle line 482.
                             let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr1_0 = C::put_in_reg(ctx, pattern7_1);
                             let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -4029,14 +4044,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
                             if let Some(pattern8_0) = C::imm8_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 624.
+                                // Rule at src/isa/x64/lower.isle line 644.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_m_rotl(ctx, pattern3_0, expr0_0, &pattern8_0)?;
                                 let expr2_0 = C::value_reg(ctx, expr1_0);
                                 return Some(expr2_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 618.
+                            // Rule at src/isa/x64/lower.isle line 638.
                             let expr0_0 = constructor_lo_reg(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = Imm8Reg::Reg { reg: expr0_0 };
@@ -4048,14 +4063,14 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
                             if let Some(pattern8_0) = C::imm8_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 533.
+                                // Rule at src/isa/x64/lower.isle line 553.
                                 let expr0_0 = C::put_in_reg(ctx, pattern7_0);
                                 let expr1_0 =
                                     constructor_shl(ctx, pattern3_0, expr0_0, &pattern8_0)?;
                                 let expr2_0 = C::value_reg(ctx, expr1_0);
                                 return Some(expr2_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 527.
+                            // Rule at src/isa/x64/lower.isle line 547.
                             let expr0_0 = constructor_lo_reg(ctx, pattern7_1)?;
                             let expr1_0 = C::put_in_reg(ctx, pattern7_0);
                             let expr2_0 = Imm8Reg::Reg { reg: expr0_0 };
@@ -4067,7 +4082,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                             let (pattern7_0, pattern7_1) =
                                 C::unpack_value_array_2(ctx, &pattern5_1);
                             if let Some(pattern8_0) = C::imm8_from_value(ctx, pattern7_1) {
-                                // Rule at src/isa/x64/lower.isle line 579.
+                                // Rule at src/isa/x64/lower.isle line 599.
                                 let expr0_0 = ExtendKind::Zero;
                                 let expr1_0 = constructor_extend_to_reg(
                                     ctx, pattern7_0, pattern3_0, &expr0_0,
@@ -4077,7 +4092,7 @@ pub fn constructor_lower<C: Context>(ctx: &mut C, arg0: Inst) -> Option<ValueReg
                                 let expr3_0 = C::value_reg(ctx, expr2_0);
                                 return Some(expr3_0);
                             }
-                            // Rule at src/isa/x64/lower.isle line 572.
+                            // Rule at src/isa/x64/lower.isle line 592.
                             let expr0_0 = ExtendKind::Zero;
                             let expr1_0 =
                                 constructor_extend_to_reg(ctx, pattern7_0, pattern3_0, &expr0_0)?;
@@ -4097,7 +4112,7 @@ 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 198.
+                        // Rule at src/isa/x64/lower.isle line 218.
                         let expr0_0 = C::put_in_reg(ctx, pattern5_1);
                         let expr1_0 = constructor_imm(ctx, pattern3_0, pattern7_0)?;
                         let expr2_0 = RegMemImm::Reg { reg: expr1_0 };
@@ -4121,7 +4136,7 @@ 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 435.
+    // Rule at src/isa/x64/lower.isle line 455.
     let expr0_0: usize = 0;
     let expr1_0 = C::value_regs_get(ctx, pattern0_0, expr0_0);
     let expr2_0: usize = 1;
@@ -4148,7 +4163,7 @@ 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 539.
+    // Rule at src/isa/x64/lower.isle line 559.
     let expr0_0: usize = 0;
     let expr1_0 = C::value_regs_get(ctx, pattern0_0, expr0_0);
     let expr2_0: usize = 1;
@@ -4207,7 +4222,7 @@ 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 586.
+    // Rule at src/isa/x64/lower.isle line 606.
     let expr0_0: usize = 0;
     let expr1_0 = C::value_regs_get(ctx, pattern0_0, expr0_0);
     let expr2_0: usize = 1;
@@ -4274,7 +4289,7 @@ 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 1008.
+        // Rule at src/isa/x64/lower.isle line 1028.
         let expr0_0 = constructor_pinsrb(ctx, pattern2_0, pattern3_0, pattern4_0)?;
         return Some(expr0_0);
     }
@@ -4282,7 +4297,7 @@ 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 1011.
+        // Rule at src/isa/x64/lower.isle line 1031.
         let expr0_0 = constructor_pinsrw(ctx, pattern2_0, pattern3_0, pattern4_0)?;
         return Some(expr0_0);
     }
@@ -4290,7 +4305,7 @@ 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 1014.
+        // Rule at src/isa/x64/lower.isle line 1034.
         let expr0_0 = OperandSize::Size32;
         let expr1_0 = constructor_pinsrd(ctx, pattern2_0, pattern3_0, pattern4_0, &expr0_0)?;
         return Some(expr1_0);
@@ -4299,7 +4314,7 @@ 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 1017.
+        // Rule at src/isa/x64/lower.isle line 1037.
         let expr0_0 = OperandSize::Size64;
         let expr1_0 = constructor_pinsrd(ctx, pattern2_0, pattern3_0, pattern4_0, &expr0_0)?;
         return Some(expr1_0);
@@ -4308,7 +4323,7 @@ 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 1020.
+        // Rule at src/isa/x64/lower.isle line 1040.
         let expr0_0 = C::sse_insertps_lane_imm(ctx, pattern4_0);
         let expr1_0 = constructor_insertps(ctx, pattern2_0, pattern3_0, expr0_0)?;
         return Some(expr1_0);
@@ -4319,7 +4334,7 @@ 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 1041.
+                // Rule at src/isa/x64/lower.isle line 1061.
                 let expr0_0 = RegMem::Reg { reg: pattern4_0 };
                 let expr1_0 = constructor_movsd(ctx, pattern2_0, &expr0_0)?;
                 return Some(expr1_0);
@@ -4327,7 +4342,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
         }
         let pattern4_0 = arg3;
         if pattern4_0 == 0 {
-            // Rule at src/isa/x64/lower.isle line 1042.
+            // Rule at src/isa/x64/lower.isle line 1062.
             let expr0_0 = SseOpcode::Movsd;
             let expr1_0 = constructor_xmm_unary_rm_r(ctx, &expr0_0, pattern3_0)?;
             let expr2_0 = RegMem::Reg { reg: expr1_0 };
@@ -4335,7 +4350,7 @@ pub fn constructor_vec_insert_lane<C: Context>(
             return Some(expr3_0);
         }
         if pattern4_0 == 1 {
-            // Rule at src/isa/x64/lower.isle line 1050.
+            // Rule at src/isa/x64/lower.isle line 1070.
             let expr0_0 = constructor_movlhps(ctx, pattern2_0, pattern3_0)?;
             return Some(expr0_0);
         }
diff --git a/cranelift/codegen/src/machinst/lower.rs b/cranelift/codegen/src/machinst/lower.rs
index fbc1efbc49..919a7db9fa 100644
--- a/cranelift/codegen/src/machinst/lower.rs
+++ b/cranelift/codegen/src/machinst/lower.rs
@@ -11,6 +11,7 @@ use crate::fx::{FxHashMap, FxHashSet};
 use crate::inst_predicates::{has_lowering_side_effect, is_constant_64bit};
 use crate::ir::instructions::BranchInfo;
 use crate::ir::{
+    types::{FFLAGS, IFLAGS},
     ArgumentPurpose, Block, Constant, ConstantData, DataFlowGraph, ExternalName, Function,
     GlobalValueData, Inst, InstructionData, MemFlags, Opcode, Signature, SourceLoc, Type, Value,
     ValueDef, ValueLabelAssignments, ValueLabelStart,
@@ -1211,6 +1212,12 @@ impl<'func, I: VCodeInst> LowerCtx for Lower<'func, I> {
         let val = self.f.dfg.resolve_aliases(val);
         log::trace!("put_value_in_regs: val {}", val);
 
+        // Assert that the value is not `iflags`/`fflags`-typed; these
+        // cannot be reified into normal registers. TODO(#3249)
+        // eventually remove the `iflags` type altogether!
+        let ty = self.f.dfg.value_type(val);
+        assert!(ty != IFLAGS && ty != FFLAGS);
+
         // If the value is a constant, then (re)materialize it at each use. This
         // lowers register pressure.
         if let Some(c) = self
@@ -1220,8 +1227,6 @@ impl<'func, I: VCodeInst> LowerCtx for Lower<'func, I> {
             .inst()
             .and_then(|inst| self.get_constant(inst))
         {
-            let ty = self.f.dfg.value_type(val);
-
             let regs = self.alloc_tmp(ty);
             log::trace!(" -> regs {:?}", regs);
             assert!(regs.is_valid());