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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/111422] Wrong code at -O3 on x86_64-linux-gnu
Date: Wed, 15 May 2024 16:13:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111422

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:ab25eef36400e8c1d28e3ed059c5f95a38b45f17

commit r15-517-gab25eef36400e8c1d28e3ed059c5f95a38b45f17
Author: Richard Biener <rguenther@suse.de>
Date:   Wed May 15 13:06:30 2024 +0200

    middle-end/111422 - wrong stack var coalescing, handle PHIs

    The gcc.c-torture/execute/pr111422.c testcase after installing the
    sink pass improvement reveals that we also need to handle

     _65 =3D &g + _58;              _44 =3D &g + _43;
     # _59 =3D PHI <_65, _44>
     *_59 =3D 8;
     g =3D {v} {CLOBBER(eos)};
     ...
     n[0] =3D &f;
     *_59 =3D 8;
     g =3D {v} {CLOBBER(eos)};

    where we fail to see the conflict between n and g after the first
    clobber of g.  Before the sinking improvement there was a conflict
    recorded on a path where _65/_44 are unused, so the real conflict
    was missed but the fake one avoided the miscompile.

    The following handles PHI defs in add_scope_conflicts_2 which
    fixes the issue.

            PR middle-end/111422
            * cfgexpand.cc (add_scope_conflicts_2): Handle PHIs
            by recursing to their arguments.=