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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/104610] memcmp () == 0 can be optimized better for
 avx512f
Date: Mon, 30 Oct 2023 03:10:17 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104610

--- Comment #23 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by hongtao Liu <liuhongt@gcc.gnu.org>:

https://gcc.gnu.org/g:8c40b72036c967fbb1d1150515cf70aec382f0a2

commit r14-5002-g8c40b72036c967fbb1d1150515cf70aec382f0a2
Author: liuhongt <hongtao.liu@intel.com>
Date:   Mon Oct 9 15:07:54 2023 +0800

    Improve memcmpeq for 512-bit vector with vpcmpeq + kortest.

    When 2 vectors are equal, kmask is allones and kortest will set CF,
    else CF will be cleared.

    So CF bit can be used to check for the result of the comparison.

    Before:
            vmovdqu (%rsi), %ymm0
            vpxorq  (%rdi), %ymm0, %ymm0
            vptest  %ymm0, %ymm0
            jne     .L2
            vmovdqu 32(%rsi), %ymm0
            vpxorq  32(%rdi), %ymm0, %ymm0
            vptest  %ymm0, %ymm0
            je      .L5
    .L2:
            movl    $1, %eax
            xorl    $1, %eax
            vzeroupper
            ret

    After:
            vmovdqu64       (%rsi), %zmm0
            xorl    %eax, %eax
            vpcmpeqd        (%rdi), %zmm0, %k0
            kortestw        %k0, %k0
            setc    %al
            vzeroupper
            ret

    gcc/ChangeLog:

            PR target/104610
            * config/i386/i386-expand.cc (ix86_expand_branch): Handle
            512-bit vector with vpcmpeq + kortest.
            * config/i386/i386.md (cbranchxi4): New expander.
            * config/i386/sse.md: (cbranch<mode>4): Extend to V16SImode
            and V8DImode.

    gcc/testsuite/ChangeLog:

            * gcc.target/i386/pr104610-2.c: New test.=