[Bug target/110438] New: generating all-ones zmm needs dep-breaking pxor before ternlog

[Bug target/110438] New: generating all-ones zmm needs dep-breaking pxor before ternlog

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

            Bug ID: 110438
           Summary: generating all-ones zmm needs dep-breaking pxor before
                    ternlog
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amonakov at gcc dot gnu.org
  Target Milestone: ---
            Target: x86_64-*-*

VPTERNLOG is never a dependency-breaking instruction on existing x86
implementations, so generating a vector of all-ones via bare ternlog can stall
waiting on destination register. GCC should emit a dependency-breaking PXOR,
otherwise it will be a false-dependency-on-popcnt-lzcnt debacle all over again.

#include <immintrin.h>

__m512i g(void)
{
    return (__m512i){ 0 } - 1;
}

g:
        # waits until previous computation
        # of zmm0 has completed
        vpternlogd      zmm0, zmm0, zmm0, 0xFF
        ret

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

--- Comment #1 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
We might want to omit PXOR when optimizing for size.

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

Hongtao.liu <crazylht at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |crazylht at gmail dot com

--- Comment #2 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Alexander Monakov from comment #1)
> We might want to omit PXOR when optimizing for size.

indeed.

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[amonakov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

--- Comment #3 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
Patch available:
https://inbox.sourceware.org/gcc-patches/8f73371d732237ed54ede44b7bd88624@ispras.ru/T/#u

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

--- Comment #4 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:13c556d6ae84be3ee2bc245a56eafa58221de86a

commit r14-2447-g13c556d6ae84be3ee2bc245a56eafa58221de86a
Author: liuhongt <hongtao.liu@intel.com>
Date:   Thu Jun 29 14:25:28 2023 +0800

    Break false dependence for vpternlog by inserting vpxor or setting
constraint of input operand to '0'

    False dependency happens when destination is only updated by
    pternlog. There is no false dependency when destination is also used
    in source. So either a pxor should be inserted, or input operand
    should be set with constraint '0'.

    gcc/ChangeLog:

            PR target/110438
            PR target/110202
            * config/i386/predicates.md
            (int_float_vector_all_ones_operand): New predicate.
            * config/i386/sse.md (*vmov<mode>_constm1_pternlog_false_dep): New
            define_insn.
            (*<avx512>_cvtmask2<ssemodesuffix><mode>_pternlog_false_dep):
            Ditto.
            (*<avx512>_cvtmask2<ssemodesuffix><mode>_pternlog_false_dep):
            Ditto.
            (*<avx512>_cvtmask2<ssemodesuffix><mode>): Adjust to
            define_insn_and_split to avoid false dependence.
            (*<avx512>_cvtmask2<ssemodesuffix><mode>): Ditto.
            (<mask_codefor>one_cmpl<mode>2<mask_name>): Adjust constraint
            of operands 1 to '0' to avoid false dependence.
            (*andnot<mode>3): Ditto.
            (iornot<mode>3): Ditto.
            (*<nlogic><mode>3): Ditto.

    gcc/testsuite/ChangeLog:

            * gcc.target/i386/pr110438.c: New test.
            * gcc.target/i386/pr100711-6.c: Adjust testcase.

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> ---
Should be fixed in GCC14.

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

--- Comment #6 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:c3f1768b21e9d994c4f090405e863feb06a54002

commit r14-2596-gc3f1768b21e9d994c4f090405e863feb06a54002
Author: liuhongt <hongtao.liu@intel.com>
Date:   Mon Jul 17 12:50:17 2023 +0800

    Remove # from <mask_codefor>one_cmpl<mode>2<mask_name> assemble output.

    optimize_insn_for_speed () in assemble output is not aligned with
    splitter condition, and it cause an ICE when building SPEC2017
    blender_r.

    libpng/pngread.c: In function âpng_read_imageâ:
    libpng/pngread.c:786:1: internal compiler error: in final_scan_insn_1, at
final.cc:2813
      786 | }
          | ^
    0x73ac3d final_scan_insn_1
            ../../gcc/final.cc:2813
    0xb3420b final_scan_insn(rtx_insn*, _IO_FILE*, int, int, int*)
            ../../gcc/final.cc:2887
    0xb344c4 final_1
            ../../gcc/final.cc:1979
    0xb34f64 rest_of_handle_final
            ../../gcc/final.cc:4240
    0xb34f64 execute
            ../../gcc/final.cc:4318

    gcc/ChangeLog:

            PR target/110438
            * config/i386/sse.md (<mask_codefor>one_cmpl<mode>2<mask_name>):
            Remove # from assemble output.

[Bug target/110438] generating all-ones zmm needs dep-breaking pxor before ternlog

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110438

liuhongt at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |liuhongt at gcc dot gnu.org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #7 from liuhongt at gcc dot gnu.org ---
.