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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109791] -Wstringop-overflow warning with -O3 and _GLIBCXX_USE_CXX11_ABI=0
Date: Thu, 11 May 2023 09:39:47 +0000 [thread overview]
Message-ID: <bug-109791-4-5RXW1UYhSs@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109791-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109791
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
DOMs scoped tables do not help. The crux is really the PHI:
__i_14 = PHI <&MEM <char[3]> [(void *)&str + 1B](10), &MEM <char[3]>
> [(void *)&str + 2B](9)>
there's no single value that exposes &str + offset.
For
_4 = (unsigned long) &MEM <char[3]> [(void *)&str + 2B];
we might want to go and express it as
_4' = (unsigned long) &str;
_4 = _4' + 2;
but the issue with the PHI node remains unless we sink the &str part
(but there's many uses of __i_14). I guess it's still the "easiest"
way to get rangers help. Aka make
# __i_14' = PHI <1(10), 2(9)>
__i_14 = &str + __i_14'; // would be a POINTER_PLUS_EXPR
it's probably still not a complete fix but maybe a good start. Of course
it increases the number of stmts - &MEM[&str + 1B] was an 'invariant'
(of course the PHI result isn't). There's not a good place for this
transform - we never "fold" PHIs (and this would be an un-folding).
next prev parent reply other threads:[~2023-05-11 9:39 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-09 16:48 [Bug c++/109791] New: " szhong at perforce dot com
2023-05-09 17:28 ` [Bug tree-optimization/109791] " pinskia at gcc dot gnu.org
2023-05-10 7:26 ` rguenth at gcc dot gnu.org
2023-05-11 8:05 ` aldyh at gcc dot gnu.org
2023-05-11 8:19 ` aldyh at gcc dot gnu.org
2023-05-11 9:39 ` rguenth at gcc dot gnu.org [this message]
2023-05-11 9:47 ` aldyh at gcc dot gnu.org
2023-05-11 11:36 ` rguenther at suse dot de
2023-05-11 11:40 ` rguenth at gcc dot gnu.org
2023-05-11 12:22 ` rguenth at gcc dot gnu.org
2023-05-11 12:34 ` rguenth at gcc dot gnu.org
2023-05-11 12:35 ` rguenth at gcc dot gnu.org
2023-05-11 12:36 ` rguenth at gcc dot gnu.org
2023-05-12 11:48 ` cvs-commit at gcc dot gnu.org
2023-05-25 12:14 ` rguenth at gcc dot gnu.org
2023-05-25 12:15 ` rguenth at gcc dot gnu.org
2023-05-25 12:16 ` rguenth at gcc dot gnu.org
2023-05-25 15:35 ` pinskia at gcc dot gnu.org
2023-06-07 22:28 ` pinskia at gcc dot gnu.org
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