public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110754] assume create spurious load for volatile variable
Date: Thu, 20 Jul 2023 22:45:10 +0000 [thread overview]
Message-ID: <bug-110754-4-xpgOhUtEPk@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110754-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110754
--- Comment #4 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> (In reply to Xi Ruoyao from comment #1)
> > Is this a bug? The standard defines accessing volatile objects as
> > side-effects so it's not allowed to merge volatile loads, AFAIU.
>
> Yes because assume attribute is defined not to have any side effects.
>
> Confirmed.
>
> gimplifier produces:
>
> [[assume (D.2786)]]
> {
> {
> int n.0;
>
> n.0 = n;
> D.2786 = n.0 == 1;
> }
> }
>
> And then lowering produces:
> _2 = n;
> .ASSUME (_Z3bari._assume.0, _2);
>
> But really it should have passed the address of n rather than the value
> since n is volatile here .
Alright, I mistakenly believed [[assume(x)]]; is same as if (!x)
unreachable();.
next prev parent reply other threads:[~2023-07-20 22:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-20 19:16 [Bug c++/110754] New: " muecker at gwdg dot de
2023-07-20 22:34 ` [Bug c++/110754] " xry111 at gcc dot gnu.org
2023-07-20 22:42 ` [Bug middle-end/110754] " pinskia at gcc dot gnu.org
2023-07-20 22:44 ` pinskia at gcc dot gnu.org
2023-07-20 22:45 ` xry111 at gcc dot gnu.org [this message]
2023-07-21 6:44 ` rguenth at gcc dot gnu.org
2023-07-21 8:33 ` muecker at gwdg dot de
2024-02-09 9:15 ` jakub at gcc dot gnu.org
2024-02-09 15:00 ` jakub at gcc dot gnu.org
2024-02-10 10:28 ` cvs-commit at gcc dot gnu.org
2024-03-02 0:38 ` cvs-commit at gcc dot gnu.org
2024-03-04 12:09 ` jakub at gcc dot gnu.org
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bug-110754-4-xpgOhUtEPk@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).