[Bug tree-optimization/94130] [8/9 Regression] Unintended result with optimization option when assigning two structures, memset and 0

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94130

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |marxin at gcc dot gnu.org

--- Comment #9 from Martin Liška <marxin at gcc dot gnu.org> ---
commit r10-7140-g349ab34dc64a10fe0b1eda66d13b62862878b73e
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 12 09:34:00 2020 +0100

    tree-dse: Fix mem* head trimming if call has lhs [PR94130]

    As the testcase shows, if DSE decides to head trim
{mem{set,cpy,move},strncpy}
    and the call has lhs, it is incorrect to leave the lhs as is, because it
    will then point to the adjusted address (base + head_trim) instead of the
    original base.
    The following patch fixes that by dropping the lhs of the call and
assigning
    lhs the original base in a following statement.

    2020-03-12  Jakub Jelinek  <jakub@redhat.com>

            PR tree-optimization/94130
            * tree-ssa-dse.c: Include gimplify.h.
            (increment_start_addr): If stmt has lhs, drop the lhs from call and
            set it after the call to the original value of the first argument.
            Formatting fixes.
            (decrement_count): Formatting fix.

            * gcc.c-torture/execute/pr94130.c: New test.