public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/103066] __sync_val_compare_and_swap/__sync_bool_compare_and_swap aren't optimized
Date: Fri, 05 Nov 2021 12:33:22 +0000 [thread overview]
Message-ID: <bug-103066-4-DYffVUwz8d@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103066-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103066
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Jakub Jelinek from comment #3)
> If by fail you mean that it doesn't update the memory if the memory isn't
> equal to expected, sure, but do you mean it can fail spuriously, not update
> the memory even if the memory is equal to expected?
> Neither __sync_{bool,val}_compare_and_swap nor __atomic_compare_exchange_n
> with weak set to false can fail spuriously, __atomic_compare_exchange_n with
> weak set to true can.
If we generate
movl m(%rip), %eax
cmpl %edi, %eax
jne .L1
movl %edi, %eax
lock cmpxchgl %esi, m(%rip)
.L1:
ret
is it a valid implementation of atomic_compare_exchange_strong?
next prev parent reply other threads:[~2021-11-05 12:33 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-03 17:35 [Bug target/103066] New: " hjl.tools at gmail dot com
2021-11-05 5:57 ` [Bug target/103066] " wwwhhhyyy333 at gmail dot com
2021-11-05 11:57 ` hjl.tools at gmail dot com
2021-11-05 12:17 ` jakub at gcc dot gnu.org
2021-11-05 12:33 ` hjl.tools at gmail dot com [this message]
2021-11-05 12:44 ` jakub at gcc dot gnu.org
2021-11-05 12:55 ` jakub at gcc dot gnu.org
2021-11-05 13:07 ` hjl.tools at gmail dot com
2021-11-05 13:25 ` jakub at gcc dot gnu.org
2021-11-05 17:40 ` redi at gcc dot gnu.org
2021-11-06 16:31 ` thiago at kde dot 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-103066-4-DYffVUwz8d@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).