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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/108552] Linux i386 kernel 5.14 memory
 corruption for pre_compound_page() when gcov is enabled
Date: Fri, 27 Jan 2023 14:14:55 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108552

--- Comment #23 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
We could mark the __gcov* artificial vars with some flag (unless they are
already) and try to avoid using IVs loaded from those in IVOPTs, but as can=
 be
seen above, the chosen IV really isn't that memory but an SSA_NAME that is
initialized with something loaded from that and in other cases it could be =
even
not that simple (say multiple copies of the same loop in sequence with a lo=
ad
from __gcov* only at the beginning and then the loops just using a PRE IV
temporary for all the stores).  I bet the RA does it from similar reasons, =
var
isn't volatile, updated many times without any atomic barriers in between, =
so
if some other thread modifies it in between, it would be a data race.=