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From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/55180] New: Missed optimization abs(-x) -> abs(x) Date: Fri, 02 Nov 2012 14:56:00 -0000 [thread overview] Message-ID: <bug-55180-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55180 Bug #: 55180 Summary: Missed optimization abs(-x) -> abs(x) Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: glisse@gcc.gnu.org double f(double x){ double y=-x; return __builtin_fabs(y); } The negation doesn't disappear, even at -Ofast, I still see both "xor" and "and" in the asm. (I don't think this optimization requires any unsafe math option, but I am not completely sure about the trapping behavior) Note that if I write __builtin_fabs(-x), the negation is removed before it has a chance to appear in a dump.
next reply other threads:[~2012-11-02 14:56 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-11-02 14:56 glisse at gcc dot gnu.org [this message] 2012-11-02 15:43 ` [Bug tree-optimization/55180] " pinskia at gcc dot gnu.org 2012-11-02 16:12 ` glisse at gcc dot gnu.org 2014-12-01 4:28 ` pinskia at gcc dot gnu.org 2014-12-01 4:28 ` pinskia at gcc dot gnu.org
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