From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <gcc-patches-return-456761-listarch-gcc-patches=gcc.gnu.org@gcc.gnu.org> Received: (qmail 36341 invoked by alias); 24 Jun 2017 18:51:27 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: <gcc-patches.gcc.gnu.org> List-Archive: <http://gcc.gnu.org/ml/gcc-patches/> List-Post: <mailto:gcc-patches@gcc.gnu.org> List-Help: <mailto:gcc-patches-help@gcc.gnu.org> Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 36331 invoked by uid 89); 24 Jun 2017 18:51:26 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.7 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,SPF_PASS autolearn=no version=3.3.2 spammy=site X-HELO: mail-yb0-f170.google.com Received: from mail-yb0-f170.google.com (HELO mail-yb0-f170.google.com) (209.85.213.170) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sat, 24 Jun 2017 18:51:25 +0000 Received: by mail-yb0-f170.google.com with SMTP id b81so1677842yba.2 for <gcc-patches@gcc.gnu.org>; Sat, 24 Jun 2017 11:51:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=9f3kOR3v5/bcD8Wzkmu0AWD/1jW6j4PP1NLKqneOIWU=; b=i5nWl57gqIOXGFa7CIZzh0456jhBMQqQN60hoE9h/lG+bHRS8O2oKfkYdUiOedg6UQ eWoiKncqUXDAJB8GekQUpEQ8IuDnMdrPz5fzUrVwfykRNF4S/5oQIGXpw5xTXT7kDdmR 8PUHcGMGbzs8BamUAgbBRPCM9GMWucr5QpNJTDFAqY0MIQERDTw0iVPj3GA9jfIhszBq AgrCh0zKjdFc41MDs1rS2eBnsg7l1AUH3308xawfUetRT/8oGzIOqF0WLuIIhkoRLdSN VCsId32SDnAqM0lsFXrnAGIAPXy7HhK0yzsyZ0FY1NUqntE1aEDX/+V+ablp4jLHM9CJ cFJw== X-Gm-Message-State: AKS2vOz6EXcFSA5hVtyK7BuvmKUpsSFP3iPjRPEyo2pDRG/Mr8jk9/uc z88XOo4C6jcB/ScmrwjFbAmguQ+HJw== X-Received: by 10.37.176.68 with SMTP id e4mr9889500ybj.26.1498330283021; Sat, 24 Jun 2017 11:51:23 -0700 (PDT) MIME-Version: 1.0 Received: by 10.129.47.200 with HTTP; Sat, 24 Jun 2017 11:51:22 -0700 (PDT) In-Reply-To: <alpine.DEB.2.20.1706240811460.2551@stedding.saclay.inria.fr> References: <CA+=Sn1mWYuz8h5zBcNqwT2LG9N4B3DueNdoZHmyb4DRREFhwQQ@mail.gmail.com> <alpine.DEB.2.20.1706240811460.2551@stedding.saclay.inria.fr> From: Andrew Pinski <pinskia@gmail.com> Date: Sat, 24 Jun 2017 18:51:00 -0000 Message-ID: <CA+=Sn1=RRnWQuyxFh5_Vd2HzS9CCLuvYPkofLefuBUiTiH4wfA@mail.gmail.com> Subject: Re: [PATCH] fold a * (a > 0 ? 1 : -1) to abs(a) and related optimizations To: GCC Patches <gcc-patches@gcc.gnu.org> Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2017-06/txt/msg01856.txt.bz2 On Fri, Jun 23, 2017 at 11:50 PM, Marc Glisse <marc.glisse@inria.fr> wrote: > On Fri, 23 Jun 2017, Andrew Pinski wrote: > >> Hi, >> I saw this on llvm's review site (https://reviews.llvm.org/D34579) >> and I thought why not add it to GCC. I expanded more than what was >> done on the LLVM patch. >> >> I added the following optimizations: >> Transform X * (X > 0 ? 1 : -1) into ABS(X). >> Transform X * (X >= 0 ? 1 : -1) into ABS(X). >> Transform X * (X > 0.0 ? 1.0 : -1.0) into ABS(X). >> Transform X * (X >= 0.0 ? 1.0 : -1.0) into ABS(X). >> Transform X * (X > 0 ? -1 : 1) into -ABS(X). >> Transform X * (X >= 0 ? -1 : 1) into -ABS(X). >> Transform X * (X > 0.0 ? -1.0 : 1.0) into -ABS(X). >> Transform X * (X >= 0.0 ? -1.0 : 1.0) into -ABS(X). >> Transform X * (X < 0 ? 1 : -1) into -ABS(X). >> Transform X * (X <= 0 ? 1 : -1) into -ABS(X). >> Transform X * (X < 0.0 ? 1.0 : -1.0) into -ABS(X). >> Transform X * (X <= 0.0 ? 1.0 : -1.0) into -ABS(X). >> Transform X * (X < 0 ? -1 : 1) into ABS(X). >> Transform X * (X <= 0 ? -1 : 1) into ABS(X). >> Transform X * (X < 0.0 ? -1.0 : 1.0) into ABS(X). >> Transform X * (X <= 0.0 ? -1.0 : 1.0) into ABS(X). >> >> The floating points ones only happen when not honoring SNANS and not >> honoring signed zeros. > > > Some random comments (not a review): > > * if X is NaN, we may get a qNaN with the wrong sign bit. We probably don't > care much though... Ok, I changed it to when not honoring NANs. > > * I am surprised (X<0.?-1.:1.) and copysign(1., X) remain different for the > whole optimization pipeline with -ffast-math. X*copysign(1., X) is another > candidate to become fabs(X). This might be a better idea because of ... > > * Whenever you get -ABS(X) for integers, what about the case where X is > INT_MIN? This. Yes this is an issue; I guess I need to rethink the integer patterns. > > * I guess we can't get there with an unsigned type because X>0 would have > become X!=0 . No, unsigned is not an issue. > > * I wonder if we could use something like > > (for cmp (gt ge lt le) > outp (convert convert negate negate) > outn (negate negate convert convert) > [...] > (outp (abs @0)) > > to reduce duplication or if that would be less readable. I did thought of that but I added the lt/le parts latter on. > > * Some of the cases are handled by PRE turning > > # iftmp.0_1 = PHI <1.0e+0(5), -1.0e+0(3)> > _3 = iftmp.0_1 * a_2(D); > > into > > _5 = -a_2(D); > [...] > # iftmp.0_1 = PHI <1.0e+0(2), -1.0e+0(3)> > # prephitmp_6 = PHI <a_2(D)(2), _5(3)> > > which phiopt3 can handle (quite late). > > * With cond, this currently (?) only affects generic, so I am not sure it > will hit very often... But it will be there if someone later writes a > match.pd->phiopt generator ;-) I have a start of this patch but I have not finished it yet. Both phiopt and ifcombine should be moved over to gimple match and simplify. I will submit a new patch which implements some of the above by the end of the day; I might split up the patch into two (one for the integer case and one for the floating point case). Thanks, Andrew > > -- > Marc Glisse