[Bug rtl-optimization/126184] [16/17 Regression] wrong code with ifcvt since r16-3760

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126184

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-16 branch has been updated by Kyrylo Tkachov
<ktkachov@gcc.gnu.org>:

https://gcc.gnu.org/g:9226f469f9e19783ac2d7fbb7498d73f75e079ac

commit r16-9422-g9226f469f9e19783ac2d7fbb7498d73f75e079ac
Author: Kyrylo Tkachov <ktkachov@nvidia.com>
Date:   Wed Jul 22 16:45:16 2026 +0200

    ifcvt: Reject hard-register destinations in multiple sets [PR126184]

    noce_convert_multiple_sets keys its dependency information by destination
    register number.  Hard registers can have overlapping definitions in
    different modes.  An exact RTL replacement cannot represent the value from
a
    partial or mode-changing definition.

    Reject hard-register destinations in the block eligibility check.  Assert
    the resulting pseudo-only invariant when dependency information is
    initialized.

    Add an RTL execution test with mixed-mode hard-register definitions.  It
    verifies that the block remains unconverted.

    Bootstrapped and regtested on aarch64-none-linux-gnu and
    x86_64-pc-linux-gnu.

    gcc/ChangeLog:

            PR rtl-optimization/126184
            * ifcvt.cc (init_noce_multiple_sets_info): Assert that destinations
            are pseudos.
            (bb_ok_for_noce_convert_multiple_sets): Reject hard-register
            destinations.

    gcc/testsuite/ChangeLog:

            PR rtl-optimization/126184
            * gcc.target/aarch64/pr126184-2.c: New test.

    Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
    (cherry picked from commit 7b4d5b42a78859b30c9b48fa0a426effbbd71ff7)