From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 120756 invoked by alias); 31 Jul 2015 10:17:44 -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 120747 invoked by uid 89); 31 Jul 2015 10:17:44 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-io0-f182.google.com Received: from mail-io0-f182.google.com (HELO mail-io0-f182.google.com) (209.85.223.182) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Fri, 31 Jul 2015 10:17:43 +0000 Received: by iodd187 with SMTP id d187so80646304iod.2 for ; Fri, 31 Jul 2015 03:17:41 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.107.10.96 with SMTP id u93mr3656023ioi.172.1438337861557; Fri, 31 Jul 2015 03:17:41 -0700 (PDT) Received: by 10.107.32.140 with HTTP; Fri, 31 Jul 2015 03:17:41 -0700 (PDT) In-Reply-To: <55B8FE61.7060008@yahoo.com> References: <55A961C1.1070206@yahoo.com> <55B7C27B.9000406@yahoo.com> <55B8FE61.7060008@yahoo.com> Date: Fri, 31 Jul 2015 10:24:00 -0000 Message-ID: Subject: Re: Another benefit of the new if converter: better performance for half hammocks when running the generated code on a modern high-speed CPU with write-back caching, relative to the code produced by the old if converter given the same source code From: Richard Biener To: Abe Cc: Alan Lawrence , "gcc-patches@gcc.gnu.org" , Sebastian Pop Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2015-07/txt/msg02643.txt.bz2 On Wed, Jul 29, 2015 at 6:25 PM, Abe wrote: >> Well. We don't generally introduce regressions with changes. > > > Understood. Regressions are bad, of course. TTBOMK the > regressions in question are temporary. Once they are gone, > I think we can then look at whether or not we still > need to keep the old if converter in trunk. Ideally, > it eventually becomes redundant and unneeded. > > >> (well, the patch still needs review - > >> I hope to get to that this week). > > After I`ve done the SPEC-based analysis, my next planned steps > on this work are to disable the code that [in my WIP] currently > causes conversion to be enabled by default when autovectorization > is enabled, then to re-integrate the old converter and implement > the switches that will give GCC users access to the modes I described > in a recent email from me. You might prefer to delay your code review > until I have that all done and a new version of the patch submitted. I'm not sure we want two if-converters. What we do want is avoid using a scratch-pad if it is safe to do (for loads and stores) and if the user tells us he is fine with store data races (for stores). Does the "new" if-converter get rid of the analysis code that determined "safe"? If so you should re-instantiate that. Richard. > Regards, > > Abe