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From: "kazu at cs dot umass dot edu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/15757] New: Convert "If (a >= b) X else if (b <= a) Y" into "if (a >= b) X". Date: Tue, 01 Jun 2004 08:17:00 -0000 [thread overview] Message-ID: <20040601081718.15757.kazu@cs.umass.edu> (raw) void bar1 (void); void bar2 (void); void foo (unsigned int a, unsigned int b) { if (a >= b) bar1 (); else if (b <= a) bar2 (); } The last tree-ssa form looks like so: foo (a, b) { <bb 0>: if (a_1 >= b_2) goto <L0>; else goto <L1>; <L0>:; bar1 () [tail call]; goto <bb 4> (<L3>); <L1>:; if (b_2 <= a_1) goto <L2>; else goto <L3>; <L2>:; bar2 () [tail call]; <L3>:; return; } Note that the second "if" should go away completely as the two "if"s are identical except the order of the variables appearing in the condition. This actually occurs in alias.i.t50.tailc like so: if (T.1029_168 >= T.1030_170) goto <L6>; else goto <L2>; <L2>:; if (T.1030_170 <= T.1029_168) goto <L3>; else goto <L4>; If I have the identical conditions twice, including the order of the variables, then the second "if" goes away as expected. -- Summary: Convert "If (a >= b) X else if (b <= a) Y" into "if (a >= b) X". Product: gcc Version: 3.5.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P2 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: kazu at cs dot umass dot edu CC: gcc-bugs at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15757
next reply other threads:[~2004-06-01 8:17 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-06-01 8:17 kazu at cs dot umass dot edu [this message] 2004-06-01 11:20 ` [Bug tree-optimization/15757] " pinskia at gcc dot gnu dot org 2004-06-05 20:22 ` law at redhat dot com 2004-06-14 20:43 ` law at gcc dot gnu dot org 2004-06-16 5:08 ` law at gcc dot gnu dot org 2004-07-10 0:45 ` pinskia at gcc dot gnu dot org
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