message: Use bitcast to transmute where possible
diff: @@ -631,12 +631,29 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
  ret.write_cvalue(fx, CValue::by_val(res, base.layout()));
  };
  - transmute, <src_ty, dst_ty> (c from) {
  - assert_eq!(from.layout().ty, src_ty);
  + transmute, (c from) {
  + assert_eq!(from.layout().size, ret.layout().size);
  + if from.layout().ty.kind == ret.layout().ty.kind {
  + ret.write_cvalue(fx, from);
  + } else if let (Some(src_ty), Some(dst_ty)) = (fx.clif_type(from.layout().ty), fx.clif_type(ret.layout().ty)) {
  + let from = from.load_scalar(fx);
  + let val = match (src_ty, dst_ty) {
  + (_, _) if src_ty == dst_ty => from,
  + (types::I32, types::F32) | (types::F32, types::I32)
  + | (types::I64, types::F64) | (types::F64, types::I64) => {
  + fx.bcx.ins().bitcast(dst_ty, from)
  + }
  + (_, _) if src_ty.is_vector() && dst_ty.is_vector() => {
  + fx.bcx.ins().raw_bitcast(dst_ty, from)
  + }
  + _ => unreachable!("{:?} -> {:?}", src_ty, dst_ty),
  + };
  + ret.write_cvalue(fx, CValue::by_val(val, ret.layout()));
  + } else {
  let (addr, meta) = from.force_stack(fx);
  assert!(meta.is_none());
  - let dst_layout = fx.layout_of(dst_ty);
  - ret.write_cvalue(fx, CValue::by_ref(addr, dst_layout))
  + ret.write_cvalue(fx, CValue::by_ref(addr, ret.layout()));
  + }
  };
  write_bytes, (c dst, v val, v count) {
  let pointee_ty = dst.layout().ty.builtin_deref(true).unwrap().ty;
  