message: Garbage in upper 32 bits shouldn't propagate to I64ExtendI32U's result.
diff: @@ -4043,6 +4043,7 @@ impl FunctionCodeGenerator<CodegenError> for X64FunctionCode {
  false,
  )[0];
  self.value_stack.push(ret);
  +
  Self::emit_relaxed_binop(
  a,
  &mut self.machine,
  @@ -4051,6 +4052,16 @@ impl FunctionCodeGenerator<CodegenError> for X64FunctionCode {
  loc,
  ret,
  );
  + if let Location::Memory(base, off) = ret {
  + Self::emit_relaxed_binop(
  + a,
  + &mut self.machine,
  + Assembler::emit_mov,
  + Size::S32,
  + Location::Imm32(0),
  + Location::Memory(base, off + 4),
  + );
  + }
  }
  Operator::I64ExtendI32S => {
  let loc =
  