[Bug target/126589] [13/14/15/16/17 Regression] Complex-mul vectorisation not honoring signed zeros

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D126589

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tamar Christina <[email protected]=
>:

https://gcc.gnu.org/g:3565f0b780965a097fdeea07b94fcfe768998a65

commit r17-2946-g3565f0b780965a097fdeea07b94fcfe768998a65
Author: Tamar Christina <[email protected]>
Date:   Tue Aug 4 15:24:53 2026 +0100

    vect: try all 8 multiplication orderings for complex patterns [PR126589]

    PR126589 make COMPLEX_MUL require -fno-signed-zeros for AArch64, but wh=
en
using
    this we miss many of the complex matching.  This is because we get a
different
    order of the operands for multiplication.

    We normally try just flipping the two multiplies around but not their
operands.

    This patch changes it to try all 8 variants.  Note that they still have=
 to
pass
    compatible_complex_nodes_p and df analysis in linear_loads_p so we won't
accept
    invalid combinations.

    There are no tests for this but it prevents patch 2 from introducing
failures.

    gcc/ChangeLog:

            PR target/126589
            * tree-vect-slp-patterns.cc (vect_validate_multiplication):
Refactor.
            (vect_validate_multiplication_commutative): New.
            (complex_mul_pattern::matches, complex_fms_pattern::matches): U=
se
it.=