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Subject: [Bug tree-optimization/105860] [10/11/12/13 Regression]
 Miscompilation causing clobbered union contents since
 r10-918-gc56c86024f8fba0c
Date: Mon, 04 Jul 2022 15:08:34 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105860

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Jambor <jamborm@gcc.gnu.org>:

https://gcc.gnu.org/g:b110e5283e368b5377e04766e4ff82cd52634208

commit r13-1460-gb110e5283e368b5377e04766e4ff82cd52634208
Author: Martin Jambor <mjambor@suse.cz>
Date:   Fri Jul 1 20:57:18 2022 +0200

    tree-sra: Fix union handling in build_reconstructed_reference

    As the testcase in PR 105860 shows, the code that tries to re-use the
    handled_component chains in SRA can be horribly confused by unions,
    where it thinks it has found a compatible structure under which it can
    chain the references, but in fact it found the type it was looking
    for elsewhere in a union and generated a write to a completely wrong
    part of an aggregate.

    I don't remember whether the plan was to support unions at all in
    build_reconstructed_reference but it can work, to an extent, if we
    make sure that we start the search only outside the outermost union,
    which is what the patch does (and the extra testcase verifies).

    gcc/ChangeLog:

    2022-07-01  Martin Jambor  <mjambor@suse.cz>

            PR tree-optimization/105860
            * tree-sra.cc (build_reconstructed_reference): Start expr
            traversal only just below the outermost union.

    gcc/testsuite/ChangeLog:

    2022-07-01  Martin Jambor  <mjambor@suse.cz>

            PR tree-optimization/105860
            * gcc.dg/tree-ssa/alias-access-path-13.c: New test.
            * gcc.dg/tree-ssa/pr105860.c: Likewise.=