diff --git a/cranelift/codegen/meta/src/shared/instructions.rs b/cranelift/codegen/meta/src/shared/instructions.rs
index 5057ea3251..79797fff4c 100644
--- a/cranelift/codegen/meta/src/shared/instructions.rs
+++ b/cranelift/codegen/meta/src/shared/instructions.rs
@@ -3273,20 +3273,14 @@ pub(crate) fn define(
 
     let Bool = &TypeVar::new(
         "Bool",
-        "A scalar or vector boolean type",
-        TypeSetBuilder::new()
-            .bools(Interval::All)
-            .simd_lanes(Interval::All)
-            .build(),
+        "A scalar boolean type",
+        TypeSetBuilder::new().bools(Interval::All).build(),
     );
 
     let BoolTo = &TypeVar::new(
         "BoolTo",
-        "A smaller boolean type with the same number of lanes",
-        TypeSetBuilder::new()
-            .bools(Interval::All)
-            .simd_lanes(Interval::All)
-            .build(),
+        "A smaller boolean type",
+        TypeSetBuilder::new().bools(Interval::All).build(),
     );
 
     let x = &Operand::new("x", Bool);
@@ -3296,11 +3290,7 @@ pub(crate) fn define(
         Inst::new(
             "breduce",
             r#"
-        Convert `x` to a smaller boolean type in the platform-defined way.
-
-        The result type must have the same number of vector lanes as the input,
-        and each lane must not have more bits that the input lanes. If the
-        input and output types are the same, this is a no-op.
+        Convert `x` to a smaller boolean type by discarding the most significant bits.
         "#,
             &formats.unary,
         )
@@ -3308,6 +3298,14 @@ pub(crate) fn define(
         .operands_out(vec![a]),
     );
 
+    let Bool = &TypeVar::new(
+        "Bool",
+        "A scalar or vector boolean type",
+        TypeSetBuilder::new()
+            .bools(Interval::All)
+            .simd_lanes(Interval::All)
+            .build(),
+    );
     let BoolTo = &TypeVar::new(
         "BoolTo",
         "A larger boolean type with the same number of lanes",
@@ -3385,20 +3383,14 @@ pub(crate) fn define(
 
     let Int = &TypeVar::new(
         "Int",
-        "A scalar or vector integer type",
-        TypeSetBuilder::new()
-            .ints(Interval::All)
-            .simd_lanes(Interval::All)
-            .build(),
+        "A scalar integer type",
+        TypeSetBuilder::new().ints(Interval::All).build(),
     );
 
     let IntTo = &TypeVar::new(
         "IntTo",
-        "A smaller integer type with the same number of lanes",
-        TypeSetBuilder::new()
-            .ints(Interval::All)
-            .simd_lanes(Interval::All)
-            .build(),
+        "A smaller integer type",
+        TypeSetBuilder::new().ints(Interval::All).build(),
     );
     let x = &Operand::new("x", Int);
     let a = &Operand::new("a", IntTo);
@@ -3407,15 +3399,10 @@ pub(crate) fn define(
         Inst::new(
             "ireduce",
             r#"
-        Convert `x` to a smaller integer type by dropping high bits.
+        Convert `x` to a smaller integer type by discarding
+        the most significant bits.
 
-        Each lane in `x` is converted to a smaller integer type by discarding
-        the most significant bits. This is the same as reducing modulo
-        `2^n`.
-
-        The result type must have the same number of vector lanes as the input,
-        and each lane must not have more bits that the input lanes. If the
-        input and output types are the same, this is a no-op.
+        This is the same as reducing modulo `2^n`.
         "#,
             &formats.unary,
         )
@@ -3855,6 +3842,14 @@ pub(crate) fn define(
         .operands_out(vec![a]),
     );
 
+    let Int = &TypeVar::new(
+        "Int",
+        "A scalar or vector integer type",
+        TypeSetBuilder::new()
+            .ints(Interval::All)
+            .simd_lanes(Interval::All)
+            .build(),
+    );
     let x = &Operand::new("x", Int);
     let a = &Operand::new("a", FloatTo);
 
diff --git a/cranelift/codegen/src/isa/aarch64/lower.isle b/cranelift/codegen/src/isa/aarch64/lower.isle
index 8c159e674f..4730f3262a 100644
--- a/cranelift/codegen/src/isa/aarch64/lower.isle
+++ b/cranelift/codegen/src/isa/aarch64/lower.isle
@@ -1193,6 +1193,20 @@
 (rule (lower (has_type (ty_vec128 ty) (vselect c x y)))
         (bsl ty c x y))
 
+;;;; Rules for `ireduce` / `breduce` ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; T -> I{64,32,16,8}: We can simply pass through the value: values
+;; are always stored with high bits undefined, so we can just leave
+;; them be.
+(rule (lower (has_type (ty_int_bool_ref_scalar_64 ty) (ireduce src)))
+    (value_regs_get src 0))
+
+;; Likewise for breduce.
+
+(rule (lower (has_type (ty_int_bool_ref_scalar_64 ty) (breduce src)))
+      (value_regs_get src 0))
+
+
 ;;;; Rules for `fcmp` 32 bit ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (rule (lower (has_type ty @ (multi_lane _ _) (fcmp (fcmp_zero_cond_not_eq cond) x (splat (f32const (zero_value_f32 y))))))
diff --git a/cranelift/codegen/src/isa/aarch64/lower_inst.rs b/cranelift/codegen/src/isa/aarch64/lower_inst.rs
index fd0c1006e6..85f1803086 100644
--- a/cranelift/codegen/src/isa/aarch64/lower_inst.rs
+++ b/cranelift/codegen/src/isa/aarch64/lower_inst.rs
@@ -423,14 +423,7 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
             ctx.emit(Inst::gen_move(rd, rn, ty));
         }
 
-        Opcode::Breduce | Opcode::Ireduce => {
-            // Smaller integers/booleans are stored with high-order bits
-            // undefined, so we can simply do a copy.
-            let rn = put_input_in_regs(ctx, inputs[0]).regs()[0];
-            let rd = get_output_reg(ctx, outputs[0]).only_reg().unwrap();
-            let ty = ctx.input_ty(insn, 0);
-            ctx.emit(Inst::gen_move(rd, rn, ty));
-        }
+        Opcode::Breduce | Opcode::Ireduce => implemented_in_isle(ctx),
 
         Opcode::Bextend | Opcode::Bmask => {
             // Bextend and Bmask both simply sign-extend. This works for: