From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 65598 invoked by alias); 6 Jul 2015 18:40:00 -0000 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 Received: (qmail 65558 invoked by uid 48); 6 Jul 2015 18:39:56 -0000 From: "amacleod at redhat dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/59767] __atomic_load_n with __ATOMIC_SEQ_CST should result in a memory barrier Date: Mon, 06 Jul 2015 18:40:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 4.8.2 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: amacleod at redhat dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2015-07/txt/msg00489.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59767 --- Comment #6 from Andrew Macleod --- The standard doesn't define what machines should generate what code. It defines terms for observing effects that need to be adhered to. Their machine model was created over a few years during the early stages of the memory model to help observe and test those effects. To the best of our knowledge we think the results from this model are an efficient and correct implementation within the standards definition. If you can provide a test case which demonstrates that this is not a correct implementation based on observable effects (ie the load is observed out of order somewhere), then we'd look at fixing it in GCC. If you want to discuss whether parts are or aren't compliant without a test case that fails, then you should contact the authors with your questions since they can give you a far better answer than I ever could.