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From: "amonakov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/110237] gcc.dg/torture/pr58955-2.c is miscompiled by RTL scheduling after reload
Date: Tue, 27 Jun 2023 09:50:11 +0000 [thread overview]
Message-ID: <bug-110237-4-WOVFqMV3Jw@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110237-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110237
--- Comment #21 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #19)
> But the size argument doesn't have anything to do with TBAA (and
> may_alias is about TBAA). I don't think we have any way to circumvent
> C object access rules. That is, for example, with -fno-strict-aliasing
> the following isn't going to work.
>
> int a;
> int b;
>
> int main()
> {
> a = 1;
> b = 2;
> if (&a + 1 == &b) // equality compare of unrelated pointers OK
> {
> long x = *(long *)&a; // access outside of 'a' not OK
> if (x != 0x0000000100000002)
> abort ();
> }
> }
>
> there's no command-line flag or attribute to form a pointer
> to an object composing 'a' and 'b' besides changing how the
> storage is declared.
But store-merging and SLP can introduce a wide long-sized access where on
source level you had two adjacent loads or even memcpy's, so we really seem to
have a problem here and might need to be able to annotate types or individual
accesses as "may-alias-with-oob-ok" in the IR: PR 110431.
next prev parent reply other threads:[~2023-06-27 9:50 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 13:50 [Bug rtl-optimization/110237] New: " rguenth at gcc dot gnu.org
2023-06-14 11:02 ` [Bug rtl-optimization/110237] " amonakov at gcc dot gnu.org
2023-06-14 12:09 ` rguenth at gcc dot gnu.org
2023-06-20 9:52 ` rguenth at gcc dot gnu.org
2023-06-20 11:35 ` crazylht at gmail dot com
2023-06-20 12:20 ` rguenther at suse dot de
2023-06-20 16:05 ` crazylht at gmail dot com
2023-06-21 5:48 ` crazylht at gmail dot com
2023-06-21 7:33 ` rguenth at gcc dot gnu.org
2023-06-25 4:06 ` crazylht at gmail dot com
2023-06-26 7:41 ` rguenther at suse dot de
2023-06-26 7:58 ` amonakov at gcc dot gnu.org
2023-06-26 8:07 ` rguenther at suse dot de
2023-06-26 8:22 ` amonakov at gcc dot gnu.org
2023-06-26 8:35 ` rguenther at suse dot de
2023-06-26 8:44 ` crazylht at gmail dot com
2023-06-26 8:54 ` amonakov at gcc dot gnu.org
2023-06-26 11:14 ` rguenther at suse dot de
2023-06-26 18:19 ` amonakov at gcc dot gnu.org
2023-06-27 6:53 ` rguenther at suse dot de
2023-06-27 7:30 ` cvs-commit at gcc dot gnu.org
2023-06-27 9:50 ` amonakov at gcc dot gnu.org [this message]
2023-06-27 10:03 ` rguenther at suse dot de
2023-06-29 1:27 ` cvs-commit at gcc dot gnu.org
2023-06-29 1:28 ` cvs-commit at gcc dot gnu.org
2023-06-29 1:29 ` cvs-commit at gcc dot gnu.org
2023-11-27 12:39 ` rdapp at gcc dot gnu.org
2023-11-29 12:26 ` cvs-commit at gcc dot gnu.org
2023-11-29 12:27 ` rguenth at gcc dot gnu.org
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