public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "drepper.fsp+rhbz at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/98737] Atomic operation on x86 no optimized to use flags Date: Tue, 26 Jan 2021 20:10:50 +0000 [thread overview] Message-ID: <bug-98737-4-Mvxn7r6gz1@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-98737-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98737 --- Comment #8 from Ulrich Drepper <drepper.fsp+rhbz at gmail dot com> --- (In reply to Jakub Jelinek from comment #7) > The sub fix won't be the same as would add, perhaps xor/or/and can be > handled by the same peephole2, but even for that I'm not sure. Just a proposal, but I can see myself using code like this. > Though e.g. > trying __atomic_or_fetch (&a, b, ...) == 0 doesn't seem to be something > people would use. I can see this being valid. If b is a variable of some time (e.g., representing a flag), a could be the set of all flag set and the result of the or operation being non-zero could mean some work based on the flags needs to be done. The alternative is is if ((b != 0 && __atomic_or_fetch(&a, b, ...)) || a != 0) ... Unconditionally performing the or is likely faster than the additional tests and jumps.
next prev parent reply other threads:[~2021-01-26 20:10 UTC|newest] Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-18 19:59 [Bug target/98737] New: " drepper.fsp+rhbz at gmail dot com 2021-01-19 7:55 ` [Bug target/98737] " rguenth at gcc dot gnu.org 2021-01-19 8:37 ` ubizjak at gmail dot com 2021-01-19 9:53 ` redi at gcc dot gnu.org 2021-01-19 10:01 ` jakub at gcc dot gnu.org 2021-01-26 15:09 ` jakub at gcc dot gnu.org 2021-01-26 16:45 ` drepper.fsp+rhbz at gmail dot com 2021-01-26 17:11 ` jakub at gcc dot gnu.org 2021-01-26 20:10 ` drepper.fsp+rhbz at gmail dot com [this message] 2021-12-14 10:20 ` jakub at gcc dot gnu.org 2022-01-03 13:17 ` cvs-commit at gcc dot gnu.org 2022-01-12 15:50 ` jakub at gcc dot gnu.org 2022-01-14 11:07 ` cvs-commit 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-98737-4-Mvxn7r6gz1@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: linkBe 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).