Re: [PATCH 2/2] validate_subreg before call gen_lowpart to avoid ICE.

[Richard Biener <richard.guenther@gmail.com>]

On Fri, Sep 10, 2021 at 2:58 PM liuhongt <hongtao.liu@intel.com> wrote:
>
> gcc/ChangeLog:
>
>         * expmed.c (extract_bit_field_using_extv): validate_subreg
>         before call gen_lowpart.
> ---
>  gcc/expmed.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/expmed.c b/gcc/expmed.c
> index 3143f38e057..10d62d857a8 100644
> --- a/gcc/expmed.c
> +++ b/gcc/expmed.c
> @@ -1571,12 +1571,16 @@ extract_bit_field_using_extv (const extraction_insn *extv, rtx op0,
>
>    if (GET_MODE (target) != ext_mode)
>      {
> +      machine_mode tmode = GET_MODE (target);
>        /* Don't use LHS paradoxical subreg if explicit truncation is needed
>          between the mode of the extraction (word_mode) and the target
>          mode.  Instead, create a temporary and use convert_move to set
>          the target.  */
>        if (REG_P (target)
> -         && TRULY_NOOP_TRUNCATION_MODES_P (GET_MODE (target), ext_mode))
> +         && TRULY_NOOP_TRUNCATION_MODES_P (tmode, ext_mode)
> +         && validate_subreg (ext_mode, tmode,
> +                             target,
> +                             subreg_lowpart_offset (ext_mode, tmode)))
>         {
>           target = gen_lowpart (ext_mode, target);

That would be equivalent to use gen_lowpart_if_possible?

>           if (partial_subreg_p (GET_MODE (spec_target), ext_mode))
> --
> 2.27.0
>