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From: "enkovich.gnu at gmail dot com" <gcc-bugzilla@gcc.gnu.org> 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 [thread overview] Message-ID: <bug-61734-4@http.gcc.gnu.org/bugzilla/> (raw) 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 <ebotcazou@138bc75d-0d04-0410-961f-82ee72b054a4> 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) <EQ_EXPR/NE_EXPR>: 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 <D.1722>; else goto <D.1723>; <D.1722>: D.1720 = (int) a; D.1721 = (int) b; D.1724 = D.1720 - D.1721; iftmp.0 = (long unsigned int) D.1724; goto <D.1725>; <D.1723>: D.1721 = (int) b; D.1720 = (int) a; D.1726 = D.1721 - D.1720; iftmp.0 = (long unsigned int) D.1726; <D.1725>: 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.1721>; 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.
next reply other threads:[~2014-07-07 13:31 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-07-07 13:31 enkovich.gnu at gmail dot com [this message] 2014-07-07 14:27 ` [Bug middle-end/61734] [4.10 Regression] " rguenth at gcc dot gnu.org 2014-07-07 15:27 ` ebotcazou at gcc dot gnu.org 2014-07-08 8:21 ` jakub at gcc dot gnu.org 2014-07-08 9:43 ` ebotcazou at gcc dot gnu.org 2014-07-08 10:18 ` jakub at gcc dot gnu.org 2014-07-08 11:46 ` glisse at gcc dot gnu.org 2014-07-22 16:41 ` ebotcazou at gcc dot gnu.org 2014-07-28 8:55 ` ebotcazou at gcc dot gnu.org 2014-07-28 8:57 ` ebotcazou at gcc dot gnu.org 2014-07-29 11:49 ` enkovich.gnu at gmail dot com 2014-07-29 15:17 ` ebotcazou at gcc dot gnu.org 2014-07-29 15:41 ` enkovich.gnu at gmail dot com 2014-07-29 16:23 ` ebotcazou at gcc dot gnu.org
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