From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12200 invoked by alias); 27 Jan 2012 14:28:47 -0000 Received: (qmail 12182 invoked by uid 22791); 27 Jan 2012 14:28:46 -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; Fri, 27 Jan 2012 14:28:33 +0000 From: "dje at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/51798] [4.7 regression] libstdc++ atomicity performance regression due to __sync_fetch_and_add Date: Fri, 27 Jan 2012 14:55:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: libstdc++ 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/msg03160.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51798 --- Comment #20 from David Edelsohn 2012-01-27 14:27:25 UTC --- Jonathan, Your explanation in comment #16 does not fully explain the design of libstdc++-v3. If the __sync_* intrinsics provide the complete abstraction for CAS, what is the purpose of the custom implementations of atomicity.h in libstdc++-v3/config/{cpu,os}/* ? One should not need those overrides if __sync_* provides sufficient abstraction. Jakub, The patch is incomplete because it should update src/libstdc++-v3/config/cpu/generic/atomicity_builtins/atomicity.h as well.