[Bug tree-optimization/111019] [12 Regression] Optimizer incorrectly assumes variable is not changed while change happens through another pointer

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111019

--- Comment #14 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:b66fd93a60d429f97ca5fdfb9a88f291c605d002

commit r12-10010-gb66fd93a60d429f97ca5fdfb9a88f291c605d002
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Aug 17 15:21:33 2023 +0200

    tree-optimization/111019 - invariant motion and aliasing

    The following fixes a bad choice in representing things to the alias
    oracle by LIM which while correct in pieces is inconsistent with itself.
    When canonicalizing a ref to a bare deref instead of leaving the base
    object and the extracted offset the same and just substituting an
    alternate ref the following replaces the base and the offset as well,
    avoiding the confusion that otherwise will arise in
    aliasing_matching_component_refs_p.

            PR tree-optimization/111019
            * tree-ssa-loop-im.cc (gather_mem_refs_stmt): When canonicalizing
            also scrap base and offset in case the ref is indirect.

            * g++.dg/torture/pr111019.C: New testcase.

    (cherry picked from commit 745ec2135aabfbe2c0fb7780309837d17e8986d4)