[Bug target/126784] Sub-optimal code sequence for __builtin_convertvector

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126784

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by H.J. Lu <hjl@gcc.gnu.org>:

https://gcc.gnu.org/g:a6173e867de7f9e7a6f060e5a208a4290d19ba51

commit r17-3355-ga6173e867de7f9e7a6f060e5a208a4290d19ba51
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Aug 18 17:57:08 2026 +0800

    match.pd: Change the MIN/MAX narrowing to MIN/MAX + convert

    "(type) minmax ((wide_type) a, (wide_type) b) to minmax (a, b)" is limited
    to the single use of the result. It doesn't support:

    typedef int v2si __attribute__((vector_size (8)));
    typedef long long v2di __attribute__((vector_size (16)));

    v2si
    func (v2si a, v2si b, v2di *p)
    {
      v2di x = __builtin_convertvector (a, v2di);
      v2di y = __builtin_convertvector (b, v2di);
      v2di z = x < y ? x : y;
      *p = z;
      return __builtin_convertvector (z, v2si);
    }

    Change it to

    minmax ((wide_type) a, (wide_type) b) -> (wide_type) minmax (a, b)

    instead.  Now we generate

            pminsd  %xmm1, %xmm0
            pmovsxdq        %xmm0, %xmm1
            movaps  %xmm1, (%rdi)

    instead of

            pmovsxdq        %xmm0, %xmm2
            pmovsxdq        %xmm1, %xmm1
            movdqa  %xmm2, %xmm0
            movdqa  %xmm2, %xmm3
            pcmpgtq %xmm1, %xmm0
            pblendvb        %xmm0, %xmm1, %xmm3
            movdqa  %xmm3, %xmm0
            movaps  %xmm3, (%rdi)
            shufps  $232, %xmm3, %xmm0

    gcc/

            PR middle-end/126784
            * match.pd ((type) minmax ((wide_type) a, (wide_type) b)): Changed
            to ...
            (minmax ((wide_type) a, (wide_type) b)): This.

    gcc/testsuite/

            PR middle-end/126784
            * g++.target/i386/pr126784-1.C: New test.
            * g++.target/i386/pr126784-2.C: Likewise.
            * gcc.target/i386/pr126784-1.c: Likewise.
            * gcc.target/i386/pr126784-2.c: Likewise.
            * gcc.target/i386/pr126784-3.c: Likewise.
            * gcc.target/i386/pr126784-4.c: Likewise.
            * gcc.target/i386/pr126784-5.c: Likewise.
            * gcc.target/i386/pr126784-6.c: Likewise.

    Signed-off-by: H.J. Lu <hjl.tools@gmail.com>