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Subject: [Bug tree-optimization/103266] [12 regression] llvm-13
 miscompilation: __builtin_assume_aligned causes over-aggressive dce
Date: Thu, 18 Nov 2021 17:42:06 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103266

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jan Hubicka <hubicka@gcc.gnu.org>:

https://gcc.gnu.org/g:c331a75d49b6043399f5ccce72a02ccf3b0ddc56

commit r12-5379-gc331a75d49b6043399f5ccce72a02ccf3b0ddc56
Author: Jan Hubicka <jh@suse.cz>
Date:   Thu Nov 18 18:41:43 2021 +0100

    Fix modref wrt __builtin_assume_aligned

    __builtin_assume_aligned has bit contraictionary fnspec description "1c=
X "
    which means that parameter 1 is returned but also unused.  PTA code tak=
es
    precedence to parameter being returned, while modref takes the info that
    parameter is unused.  This patch tweaks modref to follow PTA semantics =
(as
    suggested by Richard in the PR log)

    gcc/ChangeLog:

    2021-11-18  Jan Hubicka  <hubicka@ucw.cz>

            PR ipa/103266
            * ipa-modref.c (modref_eaf_analysis::merge_call_lhs_flags): Unu=
sed
            parameter may still be returned.
            (modref_eaf_analysis::analyze_ssa_name): Call merge_call_lhs_fl=
ags
            even for unused function args.

    gcc/testsuite/ChangeLog:

    2021-11-18  Jan Hubicka  <hubicka@ucw.cz>

            PR ipa/103266
            * g++.dg/torture/pr103266.C: New test.=