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From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/23669] New: fold does convert (-a)/10 into a/-10. Date: Thu, 01 Sep 2005 02:04:00 -0000 [thread overview] Message-ID: <20050901020344.23669.pinskia@gcc.gnu.org> (raw) Another idea from LLVM. The following two functions should be the same asm: int f(int a) { return (-a)/10; } int f1(int a) { return a/-10; } ---- We currently get on PPC: _f: lis r0,0x6666 neg r3,r3 ori r0,r0,26215 mulhw r0,r3,r0 srawi r3,r3,31 srawi r0,r0,2 subf r3,r3,r0 blr _f1: lis r0,0x6666 ori r0,r0,26215 mulhw r0,r3,r0 srawi r3,r3,31 srawi r0,r0,2 subf r3,r0,r3 blr As you can see f1 has one less instruction which should be better. -- Summary: fold does convert (-a)/10 into a/-10. Product: gcc Version: 4.1.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P2 Component: middle-end AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: pinskia at gcc dot gnu dot org CC: gcc-bugs at gcc dot gnu dot org OtherBugsDependingO 19987 nThis: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23669
next reply other threads:[~2005-09-01 2:04 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2005-09-01 2:04 pinskia at gcc dot gnu dot org [this message] 2005-09-01 2:38 ` [Bug middle-end/23669] " pinskia at gcc dot gnu dot org 2005-09-17 2:12 ` pinskia at gcc dot gnu dot org 2005-10-01 17:25 ` mrnobo1024 at yahoo dot com 2005-10-01 17:34 ` [Bug middle-end/23669] fold does convert (-a)/10 into a/-10 with -fno-wrapv pinskia at gcc dot gnu dot org
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