[Bug target/126098] ICE in extract_insn, at recog.cc:2888 mavx512vnni, autovectorized

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126098

--- Comment #2 from GCC 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:5be7b70e769e6e992dbf631cd37e24bd9da9e05e

commit r17-2161-g5be7b70e769e6e992dbf631cd37e24bd9da9e05e
Author: liuhongt <hongtao.liu@intel.com>
Date:   Fri Jul 3 06:46:32 2026 -0700

    i386: Enable 512-bit byte dot-product only under AVX512BW [PR126098]

    The byte sdot_prod/udot_prod expanders used the VI1_AVX512VNNIBW
    iterator, which enabled V64QI under AVX512BW || AVX512VNNI.  But VNNI
    has no same-sign byte instruction (VPDPBUSD is mixed-sign, i.e. usdot),
    so the same-sign byte case always emulates via vec_unpacks/vec_unpacku,
    and for V64QI that widening is vpmov[sz]xbw, which needs AVX512BW.  With
    -mavx512vnni alone the optab was offered but couldn't be emulated:

      (set (reg:V32HI) (sign_extend:V32HI (reg:V32QI)))

    fails to match, ICEing in extract_insn during vregs.

    Use the VI1_AVX512 iterator instead (V64QI under AVX512BW), matching the
    sibling usdot_prod, and drop VI1_AVX512VNNIBW.  The word sdot_prod uses a
    separate iterator (VI2_AVX512VNNIBW) and is left unchanged: its V32HI VNNI
    path is vpdpwssd on the 16-bit inputs directly, so no widening is needed.

    gcc/ChangeLog:

            PR target/126098
            * config/i386/sse.md (VI1_AVX512VNNIBW): Remove.
            (sdot_prod<ssedvecmodelower><mode>): Use VI1_AVX512 instead of
            VI1_AVX512VNNIBW so V64QI is enabled only under AVX512BW.
            (udot_prod<ssedvecmodelower><mode>): Likewise.

    gcc/testsuite/ChangeLog:

            PR target/126098
            * gcc.target/i386/pr126098.c: New test.