[Bug target/113609] New: EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[Bug target/113609] New: EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113609

            Bug ID: 113609
           Summary: EQ/NE comparison between avx512 kmask and -1 can be
                    optimized with kxortest with checking CF.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: liuhongt at gcc dot gnu.org
  Target Milestone: ---

It's from PR113576, there's code like 
 35        kmovb   %k0, %edx
 36        cmpb    $-1, %dl
 37        jne     .L21

The original codegen is buggy, but still exposed a optimization issue.
Compare 8/16/32/64-bit kmask to -1 and check equal or not can be optimized with
kortest by check CF.


KORTESTW ¶
TMP[15:0] := DEST[15:0] BITWISE OR SRC[15:0]
IF(TMP[15:0]=0)
    THEN ZF := 1
    ELSE ZF := 0
FI;
IF(TMP[15:0]=FFFFh)
    THEN CF := 1
    ELSE CF := 0
FI;
KORTESTB ¶
TMP[7:0] := DEST[7:0] BITWISE OR SRC[7:0]
IF(TMP[7:0]=0)
    THEN ZF := 1
    ELSE ZF := 0
FI;
IF(TMP[7:0]==FFh)
    THEN CF := 1
    ELSE CF := 0
FI;
KORTESTQ ¶
TMP[63:0] := DEST[63:0] BITWISE OR SRC[63:0]
IF(TMP[63:0]=0)
    THEN ZF := 1
    ELSE ZF := 0
FI;
IF(TMP[63:0]==FFFFFFFF_FFFFFFFFh)
    THEN CF := 1
    ELSE CF := 0
FI;
KORTESTD ¶
TMP[31:0] := DEST[31:0] BITWISE OR SRC[31:0]
IF(TMP[31:0]=0)
    THEN ZF := 1
    ELSE ZF := 0
FI;
IF(TMP[31:0]=FFFFFFFFh)
    THEN CF := 1
    ELSE CF := 0
FI;

[Bug target/113609] EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113609

--- Comment #1 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
Since they're different modes, CCZ for cmp, but CCS for kortest, it could be
diffcult to optimize it in RA stage by adding alternatives(like we did for
compared to 0). So the easy way could be adding peephole to hanlde that.

[Bug target/113609] EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113609

--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Hongtao Liu from comment #1)
> Since they're different modes, CCZ for cmp, but CCS for kortest, it could be
> diffcult to optimize it in RA stage by adding alternatives(like we did for
> compared to 0). So the easy way could be adding peephole to hanlde that.

You can use pre-reload split for this. Please see for example how *jcc_bt<mode>
and *bt<mode>_setcqi provide compound operation (constructed from CCZmode
compare) that is later split to CCCmode operation. You will have to provide jcc
and setcc patterns to fully handle mode change.

[Bug target/113609] EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113609

--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Hu <hulin@gcc.gnu.org>:

https://gcc.gnu.org/g:bf7745f887c765e06f2e75508f263debb60aeb2e

commit r15-974-gbf7745f887c765e06f2e75508f263debb60aeb2e
Author: Hu, Lin1 <lin1.hu@intel.com>
Date:   Thu May 9 09:29:07 2024 +0800

    i386: Optimize EQ/NE comparison between avx512 kmask and -1.

    Acheive EQ/NE comparison between avx512 kmask and -1 by using kxortest
    with checking CF.

    gcc/ChangeLog:

            PR target/113609
            * config/i386/sse.md
            (*kortest_cmp<mode>_setcc): New define_insn_and_split.
            (*kortest_cmp<mode>_jcc): Ditto.

    gcc/testsuite/ChangeLog:

            PR target/113609
            * gcc.target/i386/pr113609-1.c: New test.
            * gcc.target/i386/pr113609-2.c: Ditto.

[Bug target/113609] EQ/NE comparison between avx512 kmask and -1 can be optimized with kxortest with checking CF.

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113609

Hongtao Liu <liuhongt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
Fixed in GCC15