From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 9415 invoked by alias); 3 Aug 2010 16:25:00 -0000 Received: (qmail 9405 invoked by uid 22791); 3 Aug 2010 16:24:59 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE X-Spam-Check-By: sourceware.org Received: from mail-iw0-f175.google.com (HELO mail-iw0-f175.google.com) (209.85.214.175) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 03 Aug 2010 16:24:48 +0000 Received: by iwn34 with SMTP id 34so5295388iwn.20 for ; Tue, 03 Aug 2010 09:24:47 -0700 (PDT) MIME-Version: 1.0 Received: by 10.231.144.201 with SMTP id a9mr8990679ibv.67.1280852686990; Tue, 03 Aug 2010 09:24:46 -0700 (PDT) Received: by 10.231.206.9 with HTTP; Tue, 3 Aug 2010 09:24:46 -0700 (PDT) In-Reply-To: <4C583FB5.50801@codesourcery.com> References: <4C572CA0.3040802@codesourcery.com> <4C57C416.70504@gnu.org> <4C582BD8.3080306@codesourcery.com> <4C582F2A.1080303@redhat.com> <4C583179.8020500@codesourcery.com> <4C5832CB.7040203@redhat.com> <4C583597.3000305@gnu.org> <4C583D76.2080609@codesourcery.com> <4C583FB5.50801@codesourcery.com> Date: Tue, 03 Aug 2010 16:25:00 -0000 Message-ID: Subject: Re: Combiner fixes From: Richard Guenther To: Bernd Schmidt Cc: Paolo Bonzini , Jeff Law , GCC Patches , Richard Earnshaw Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes 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 X-SW-Source: 2010-08/txt/msg00212.txt.bz2 On Tue, Aug 3, 2010 at 6:11 PM, Bernd Schmidt wro= te: > On 08/03/2010 06:06 PM, Richard Guenther wrote: >> On Tue, Aug 3, 2010 at 6:01 PM, Bernd Schmidt = wrote: >>> On 08/03/2010 05:44 PM, Richard Guenther wrote: >>>> It's not safe on RTL, please do not add FP reassociation there. >>>> (config/i386/i386.c:ix86_expand_{round,trunc,...} would start >>>> to break). >>> >>> Not a problem (I guess a !FLOAT_MODE_P || flag_associative_math test is >>> needed), but I guess I don't understand how things would break - I see >>> no multiply operations in these i386 functions. =A0Can you elaborate? >> >> It was just a general comment to re-associations of FP on RTL, >> but more important is that we not start doing constant folding, >> re-associating should be fine as long as they are valid without >> any fancy math flags. > > Constant folding should be dealt with in simplify_unary_operation (NEG, > ...) as Paolo said. > > So, what is your opinion about this specific transformation? =A0Should it > be enabled with flag_associative_math only? The specific transformation is always valid as it doesn't change the outcome of the operation. It can be done unconditionally. Richard. > > Bernd >