Re: [PATCH] i386: Disable ix86_expand_vecop_qihi2 when !TARGET_AVX512BW

[Hongtao Liu <crazylht@gmail.com>]

On Tue, May 21, 2024 at 2:16 PM Haochen Jiang <haochen.jiang@intel.com> wrote:
>
> Hi all,
>
> Since vpermq is really slow, we should avoid using it when it is
> the only instruction could be used for ix86_expand_vecop_qihi2.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu. Ok for trunk?
Please add a testcase for it.
>
> Thx,
> Haochen
>
> gcc/ChangeLog:
>
>         PR target/115069
>         * config/i386/i386-expand.cc (ix86_expand_vecop_qihi2):
>         Do not enable the optimization when AVX512BW is not enabled.
> ---
>  gcc/config/i386/i386-expand.cc | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc
> index a6132911e6a..f24c800bb4f 100644
> --- a/gcc/config/i386/i386-expand.cc
> +++ b/gcc/config/i386/i386-expand.cc
> @@ -24323,6 +24323,11 @@ ix86_expand_vecop_qihi2 (enum rtx_code code, rtx dest, rtx op1, rtx op2)
>    bool op2vec = GET_MODE_CLASS (GET_MODE (op2)) == MODE_VECTOR_INT;
>    bool uns_p = code != ASHIFTRT;
>
> +  /* vpermq is slow and we should not fall into the optimization when
> +     it is the only instruction to be selected.  */
> +  if (!TARGET_AVX512BW)
> +    return false;
> +
>    if ((qimode == V16QImode && !TARGET_AVX2)
>        || (qimode == V32QImode && (!TARGET_AVX512BW || !TARGET_EVEX512))
>        /* There are no V64HImode instructions.  */
> --
> 2.31.1
>


-- 
BR,
Hongtao