On Wed, Jul 12, 2023 at 5:20 AM YunQiang Su <yunqiang...@cipunited.com> wrote:
>
> PR #104914
>
> When work with
> int val;
> ((unsigned char*)&val)[0] = *buf;
> The RTX mode is obtained from REG instead of SUBREG,
> which make D<INS> is used instead of <INS>.
> Thus something wrong happens on sign-extend default architectures,
> like MIPS64.
>
> gcc/ChangeLog:
> PR: 104914.
> * expmed.cc(store_bit_field_1): Get mode from original
> str_rtx instead of op0.
> ---
> gcc/expmed.cc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/expmed.cc b/gcc/expmed.cc
> index fbd4ce2d42f..37f90912122 100644
> --- a/gcc/expmed.cc
> +++ b/gcc/expmed.cc
> @@ -849,7 +849,7 @@ store_bit_field_1 (rtx str_rtx, poly_uint64 bitsize,
> poly_uint64 bitnum,
> if we aren't. This must come after the entire register case above,
> since that case is valid for any mode. The following cases are only
> valid for integral modes. */
> - opt_scalar_int_mode op0_mode = int_mode_for_mode (GET_MODE (op0));
> + opt_scalar_int_mode op0_mode = int_mode_for_mode (GET_MODE (str_rtx));
I don't think this is correct - op0_mode is used to store into op0, and we are
just requiring that it is an integer mode and equal to the original
mode. I suppose
your patch makes us go to the fallback code instead, but it's surely
for the wrong
reason. I also wonder why we don't just check GET_MODE_CLASS
(GET_MODE (op0)) == MODE_CLASS_INT ...
> scalar_int_mode imode;
> if (!op0_mode.exists (&imode) || imode != GET_MODE (op0))
> {
> --
> 2.30.2
>
