The following testcase reduced from Kopete is miscompiled at -O2 struct Bar { bool is() const; int status() const; };
void foobar(void); void foobar2(void); void Foo(const Bar& x, const Bar& y) { const bool wasOffline = !x.is(); const bool isOffline = !y.is(); if (wasOffline || y.status() == 10) foobar(); if (wasOffline != isOffline) foobar2(); } .t23.mergephi: <bb 0>: D.1589_3 = is (x_2); wasOffline_4 = !D.1589_3; D.1590_6 = is (y_5); isOffline_7 = !D.1590_6; if (wasOffline_4) goto <L1>; else goto <L0>; <L0>:; D.1596_10 = status (y_5); if (D.1596_10 == 10) goto <L1>; else goto <L5>; <L1>:; foobar (); <L5>:; if (wasOffline_4 != isOffline_7) goto <L6>; else goto <L7>; <L6>:; foobar2 (); <L7>:; return; .t24.forwprop: <bb 0>: D.1589_3 = is (x_2); D.1590_6 = is (y_5); isOffline_7 = !D.1590_6; if (D.1589_3 == 0) goto <L1>; else goto <L0>; <L0>:; D.1596_10 = status (y_5); if (D.1596_10 == 10) goto <L1>; else goto <L5>; <L1>:; foobar (); <L5>:; if (D.1589_3 != 0) goto <L6>; else goto <L7>; <L6>:; foobar2 (); <L7>:; return; note that the comparison preceding foobar2() is hosed now, we even don't use isOffline or D.1590 anymore. -- Summary: [4.0 Regression] Wrong code from forwprop Product: gcc Version: 4.0.2 Status: UNCONFIRMED Keywords: wrong-code Severity: critical Priority: P2 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: rguenth at gcc dot gnu dot org CC: gcc-bugs at gcc dot gnu dot org,matz at suse dot de http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23326