From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 11500 invoked by alias); 7 Jul 2014 13:31:48 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 11386 invoked by uid 48); 7 Jul 2014 13:31:40 -0000 From: "enkovich.gnu at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/61734] New: Regression in ABS_EXPR recognition Date: Mon, 07 Jul 2014 13:31:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Version: 4.10.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: enkovich.gnu at gmail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2014-07/txt/msg00369.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61734 Bug ID: 61734 Summary: Regression in ABS_EXPR recognition Product: gcc Version: 4.10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: enkovich.gnu at gmail dot com Recently a performance regression occurred in tests heavily using ABS computation (observed on x86 and ARM targets). It is caused by missing ABS_EXPR recognition which results in sub-optimal code. Problem appeared after this commit: commit 32ce9a5c4208411361402f60e672c4830da0bc8f Author: ebotcazou Date: Tue May 27 19:54:46 2014 +0000 * fold-const.c (fold_comparison): Clean up and extend X +- C1 CMP C2 to X CMP C2 -+ C1 transformation to EQ_EXPR/NE_EXPR. Add X - Y CMP 0 to X CMP Y transformation. (fold_binary_loc) : Remove same transformations. git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@210979 138bc75d-0d04-0410-961f-82ee72b054a4 Here is a simple test (tested on linux-x86_64): >cat test.i unsigned long test (unsigned char a, unsigned char b, unsigned long sum) { sum += ((a - b) > 0 ? (a - b) : -(a - b)); return sum; } >gcc-exp-build/bin/gcc test.i -m32 -O2 -fdump-tree-gimple -c >cat test.i.004t.gimple test (unsigned char a, unsigned char b, long unsigned int sum) { long unsigned int iftmp.0; int D.1720; int D.1721; int D.1724; int D.1726; long unsigned int D.1727; D.1720 = (int) a; D.1721 = (int) b; if (D.1720 > D.1721) goto ; else goto ; : D.1720 = (int) a; D.1721 = (int) b; D.1724 = D.1720 - D.1721; iftmp.0 = (long unsigned int) D.1724; goto ; : D.1721 = (int) b; D.1720 = (int) a; D.1726 = D.1721 - D.1720; iftmp.0 = (long unsigned int) D.1726; : sum = iftmp.0 + sum; D.1727 = sum; return D.1727; } With older compiler I have: >gcc-ref-build/bin/gcc test.i -m32 -O2 -fdump-tree-gimple -c >cat test.i.004t.gimple test (unsigned char a, unsigned char b, long unsigned int sum) { int D.1719; int D.1720; int D.1721; int D.1722; long unsigned int D.1723; long unsigned int D.1724; D.1719 = (int) a; D.1720 = (int) b; D.1721 = D.1719 - D.1720; D.1722 = ABS_EXPR ; D.1723 = (long unsigned int) D.1722; sum = D.1723 + sum; D.1724 = sum; return D.1724; } BTW both compilers generate ABS_EXPR when -O0 is used instead of -O2. Both compilers fail to generate ABS_EXPR when -m64 is used instead of -m32.