From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 70658 invoked by alias); 29 Mar 2017 19:11:20 -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 70638 invoked by uid 89); 29 Mar 2017 19:11:19 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:1094, H*M:3f62 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 29 Mar 2017 19:11:18 +0000 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 88F0D883A6; Wed, 29 Mar 2017 19:11:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 88F0D883A6 Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=law@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 88F0D883A6 Received: from localhost.localdomain (ovpn-116-218.phx2.redhat.com [10.3.116.218]) by smtp.corp.redhat.com (Postfix) with ESMTP id 59F3A5C545; Wed, 29 Mar 2017 19:11:18 +0000 (UTC) Subject: Re: [PATCH][RFC] Fix P1 PR77498 To: Richard Biener , gcc-patches@gcc.gnu.org References: From: Jeff Law Message-ID: Date: Wed, 29 Mar 2017 19:28:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2017-03/txt/msg01485.txt.bz2 On 03/29/2017 04:05 AM, Richard Biener wrote: > > After quite some pondering over this and other related bugs I propose > the following for GCC 7 which tames down PRE a bit (back to levels > of GCC 6). Technically it's the wrong place to fix this, we do > have measures in place during elimination but they are not in effect > at -O2. For GCC 8 I'd like to be more aggressive there but that > would require to enable predictive commoning at -O2 (with some > limits to its unrolling) to not lose optimization opportunities. > > The other option is to ignore this issue and postpone the solution > to GCC 8. > > Bootstrapped / tested on x86_64-unknown-linux-gnu. > > Any preference? > > Thanks, > Richard. > > 2017-03-29 Richard Biener > > PR tree-optimization/77498 > * tree-ssa-pre.c (phi_translate_1): Do not allow simplifications > to non-constants over backedges. > > * gfortran.dg/pr77498.f: New testcase. I've got a slight preference for this patch. If you had a good start on the real fix then I'd lean more towards postponing. jeff