[Bug target/103861] [i386] vectorize v2qi vectors

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103861

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Uros Bizjak <uros@gcc.gnu.org>:

https://gcc.gnu.org/g:9ff206d3865df5cb8407490aa9481029beac087f

commit r12-6173-g9ff206d3865df5cb8407490aa9481029beac087f
Author: Uros Bizjak <ubizjak@gmail.com>
Date:   Sun Jan 2 21:12:10 2022 +0100

    i386: Introduce V2QImode vectorized arithmetic [PR103861]

    This patch adds basic V2QImode infrastructure and V2QImode arithmetic
    operations (plus, minus and neg).  The patched compiler can emit SSE
    vectorized QImode operations (e.g. PADDB) with partial QImode vector,
    and also synthesized double HI/LO QImode operations with integer registers.

    The testcase:

    typedef char __v2qi __attribute__ ((__vector_size__ (2)));
    __v2qi plus  (__v2qi a, __v2qi b) { return a + b; };

    compiles with -O2 to:

            movl    %edi, %edx
            movl    %esi, %eax
            addb    %sil, %dl
            addb    %ah, %dh
            movl    %edx, %eax
            ret

    which is much better than what the unpatched compiler produces:

            movl    %edi, %eax
            movl    %esi, %edx
            xorl    %ecx, %ecx
            movb    %dil, %cl
            movsbl  %dh, %edx
            movsbl  %ah, %eax
            addl    %edx, %eax
            addb    %sil, %cl
            movb    %al, %ch
            movl    %ecx, %eax
            ret

    The V2QImode vectorization does not require vector registers, so it can
    be enabled by default also for 32-bit targets without SSE.

    The patch also enables vectorized V2QImode sign/zero extends.

    2021-12-30  Uroš Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog:

            PR target/103861
            * config/i386/i386.h (VALID_SSE2_REG_MODE): Add V2QImode.
            (VALID_INT_MODE_P): Ditto.
            * config/i386/i386.c (ix86_secondary_reload): Handle
            V2QImode reloads from SSE register to memory.
            (vector_mode_supported_p): Always return true for V2QImode.
            * config/i386/i386.md (*subqi_ext<mode>_2): New insn pattern.
            (*negqi_ext<mode>_2): Ditto.
            * config/i386/mmx.md (movv2qi): New expander.
            (movmisalignv2qi): Ditto.
            (*movv2qi_internal): New insn pattern.
            (*pushv2qi2): Ditto.
            (negv2qi2 and splitters): Ditto.
            (<plusminus:insn>v2qi3 and splitters): Ditto.

    gcc/testsuite/ChangeLog:

            PR target/103861
            * gcc.dg/store_merging_18.c (dg-options): Add -fno-tree-vectorize.
            * gcc.dg/store_merging_29.c (dg-options): Ditto.
            * gcc.target/i386/pr103861.c: New test.
            * gcc.target/i386/pr92658-avx512vl.c (dg-final):
            Remove vpmovqb scan-assembler xfail.
            * gcc.target/i386/pr92658-sse4.c (dg-final):
            Remove pmovzxbq scan-assembler xfail.
            * gcc.target/i386/pr92658-sse4-2.c (dg-final):
            Remove pmovsxbq scan-assembler xfail.
            * gcc.target/i386/warn-vect-op-2.c (dg-warning): Adjust warnings.