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Subject: [Bug rtl-optimization/106187] armhf: Miscompilation at O2 level (O0
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Date: Wed, 03 Aug 2022 09:07:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106187

--- Comment #49 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Earnshaw <rearnsha@gcc.gnu.or=
g>:

https://gcc.gnu.org/g:64ce76d940501cb04d14a0d36752b4f93473531c

commit r13-1948-g64ce76d940501cb04d14a0d36752b4f93473531c
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Wed Aug 3 10:01:51 2022 +0100

    cselib: add function to check if SET is redundant [PR106187]

    A SET operation that writes memory may have the same value as an
    earlier store but if the alias sets of the new and earlier store do
    not conflict then the set is not truly redundant.  This can happen,
    for example, if objects of different types share a stack slot.

    To fix this we define a new function in cselib that first checks for
    equality and if that is successful then finds the earlier store in the
    value history and checks the alias sets.

    The routine is used in two places elsewhere in the compiler:
    cfgcleanup and postreload.

    gcc/ChangeLog:

            PR rtl-optimization/106187
            * alias.h (mems_same_for_tbaa_p): Declare.
            * alias.cc (mems_same_for_tbaa_p): New function.
            * dse.cc (record_store): Use it instead of open-coding
            alias check.
            * cselib.h (cselib_redundant_set_p): Declare.
            * cselib.cc: Include alias.h
            (cselib_redundant_set_p): New function.
            * cfgcleanup.cc: (mark_effect): Use cselib_redundant_set_p inst=
ead
            of rtx_equal_for_cselib_p.
            * postreload.cc (reload_cse_simplify): Use cselib_redundant_set=
_p.
            (reload_cse_noop_set_p): Delete.=