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List:       gcc-bugs
Subject:    [Bug middle-end/94994] [10/11 Regression] possible miscompilation of word-at-a-time copy via packed 
From:       "cvs-commit at gcc dot gnu.org via Gcc-bugs" <gcc-bugs () gcc ! gnu ! org>
Date:       2020-12-31 16:51:55
Message-ID: bug-94994-4-BSxGjKVg5M () http ! gcc ! gnu ! org/bugzilla/
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94994

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Sandiford <rsandifo@gcc.gnu.org>:

https://gcc.gnu.org/g:9fa5b473b5b8e289b6542adfd5cfaddfb3036048

commit r11-6380-g9fa5b473b5b8e289b6542adfd5cfaddfb3036048
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Dec 31 16:51:33 2020 +0000

    vect: Fix bogus alignment assumption in alias checks [PR94994]

    This PR is about a case in which the vectoriser was feeding
    incorrect alignment information to tree-data-ref.c, leading
    to incorrect runtime alias checks.  The alignment was taken
    from the TREE_TYPE of the DR_REF, which in this case was a
    COMPONENT_REF with a normally-aligned type.  However, the
    underlying MEM_REF was only byte-aligned.

    This patch uses dr_alignment to calculate the (byte) alignment
    instead, just like we do when creating vector MEM_REFs.

    gcc/
            PR tree-optimization/94994
            * tree-vect-data-refs.c (vect_vfa_align): Use dr_alignment.

    gcc/testsuite/
            PR tree-optimization/94994
            * gcc.dg/vect/pr94994.c: New test.=
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