From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28992 invoked by alias); 10 Jan 2012 18:09:12 -0000 Received: (qmail 28977 invoked by uid 22791); 10 Jan 2012 18:09:10 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 10 Jan 2012 18:08:58 +0000 From: "dje at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/51766] [4.7 regression] sync_fetch_and_xxx atomicity Date: Tue, 10 Jan 2012 18:09:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: dje at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.7.0 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-01/txt/msg01079.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51766 --- Comment #8 from David Edelsohn 2012-01-10 18:08:23 UTC --- For the way that programmers use __sync_* builtins, release or acquire-release semantics are sufficient. As we see in libstdc++, release semantics are overly strict when incrementing the reference, as opposed to destroying an object. Again, there is no cost to Intel specifying sequential consistency as opposed to a slightly weaker memory model. Intel chose a memory model that matched and benefited their architecture. IBM should have the freedom to choose memory models that benefit its architectures.