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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/46726] New: x*x has different cost than pow(x,2) with -ffast-math Date: Tue, 30 Nov 2010 15:38:00 -0000 [thread overview] Message-ID: <bug-46726-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46726 Summary: x*x has different cost than pow(x,2) with -ffast-math Product: gcc Version: 4.6.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: rguenth@gcc.gnu.org CC: hubicka@gcc.gnu.org double foo(double x, double y) { return x*x + y; } is inlined at -O2 but not at -O2 -ffast-math (which folds x*x to pow(x, 2)). MUL_EXPR has const 1 but __builtin_pow isn't is_inexpensive_builtin. We probably should special-case pow(, 2) and pow(, 0.5) and sqrt where target support is available.
next reply other threads:[~2010-11-30 15:18 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2010-11-30 15:38 rguenth at gcc dot gnu.org [this message] 2010-12-06 16:29 ` [Bug tree-optimization/46726] " rguenth at gcc dot gnu.org 2010-12-07 10:44 ` rguenth at gcc dot gnu.org 2010-12-07 10:45 ` rguenth at gcc dot gnu.org
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