wasmtime: Cranelift: can't legalize sload32

I’ve minimized a test case that currently fails on 32-bit platforms:

target i686

function u0:1516(i32) -> i32 system_v {
block0(v0: i32):
    v1 = load.i32 notrap aligned readonly v0
    ;v2 = load.i32 v1
    ;v3 = sextend.i64 v2
    v3 = sload32 v1
    v4, v5 = isplit v3
    return v4
}

I’ve tried writing a legalizer for it that would produce the commented instructions but it doesn’t do anything (same lack of result for expand, widen, narrow). What gives?

--- a/cranelift/codegen/meta/src/shared/legalize.rs
+++ b/cranelift/codegen/meta/src/shared/legalize.rs
@@ -107,6 +107,7 @@ pub(crate) fn define(insts: &InstructionGroup, imm: &Immediates) -> TransformGro
     let sdiv_imm = insts.by_name("sdiv_imm");
     let select = insts.by_name("select");
     let sextend = insts.by_name("sextend");
+    let sload32 = insts.by_name("sload32");
     let sshr = insts.by_name("sshr");
     let sshr_imm = insts.by_name("sshr_imm");
     let srem = insts.by_name("srem");
@@ -213,6 +214,14 @@ pub(crate) fn define(insts: &InstructionGroup, imm: &Immediates) -> TransformGro
     // embedded as part of arguments), so use a custom legalization for now.
     narrow.custom_legalize(iconst, "narrow_iconst");
 
+    narrow.legalize(
+        def!(a = sload32.I64(flags, ptr, offset)),
+        vec![
+            def!(b = load.I32(flags, ptr, offset)),
+            def!(a = sextend.I64(b)),
+        ]
+    );
+
     for &(ty, ty_half) in &[(I128, I64), (I64, I32)] {
         let inst = uextend.bind(ty).bind(ty_half);
         narrow.legalize(