From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 101553 invoked by alias); 22 Jun 2015 16:08:44 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 101542 invoked by uid 89); 22 Jun 2015 16:08:43 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.2 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 22 Jun 2015 16:08:42 +0000 Received: from svr-orw-fem-06.mgc.mentorg.com ([147.34.97.120]) by relay1.mentorg.com with esmtp id 1Z74H0-0003Iq-HX from Nathan_Sidwell@mentor.com ; Mon, 22 Jun 2015 09:08:38 -0700 Received: from [127.0.0.1] (147.34.91.1) by SVR-ORW-FEM-06.mgc.mentorg.com (147.34.97.120) with Microsoft SMTP Server id 14.3.224.2; Mon, 22 Jun 2015 09:08:38 -0700 Message-ID: <55883304.7060409@codesourcery.com> Date: Mon, 22 Jun 2015 16:13:00 -0000 From: Nathan Sidwell User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Bernd Schmidt , Jakub Jelinek , Julian Brown CC: Thomas Schwinge , Subject: Re: [gomp4] Preserve NVPTX "reconvergence" points References: <20150528150635.7bd5db23@octopus> <20150528142011.GN10247@tucnak.redhat.com> <87pp5kg3js.fsf@schwinge.name> <20150528150802.GO10247@tucnak.redhat.com> <5583E68A.9020608@codesourcery.com> <20150619122557.GO10247@tucnak.redhat.com> <20150622145549.481d4549@octopus> <20150622142456.GZ10247@tucnak.redhat.com> <5588273C.60109@codesourcery.com> In-Reply-To: <5588273C.60109@codesourcery.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2015-06/txt/msg01457.txt.bz2 On 06/22/15 11:18, Bernd Schmidt wrote: > You can have a hint that it is desirable, but not a hint that it is correct > (because passes in between may invalidate that). The OpenACC directives > guarantee to the compiler that the program can be transformed into a parallel > form. If we lose them early we must then rely on our analysis which may not be > strong enough to prove that the loop can be parallelized. If we make these > transformations early enough, while we still have the OpenACC directives, we can > guarantee that we do exactly what the programmer specified. How does this differ from openmp's needs to preserve parallelism on a parallel loop? Is it more than the reconvergence issue? nathan -- Nathan Sidwell