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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/51877] New: [4.7 Regression] XEmacs miscompilation due to tail merging Date: Tue, 17 Jan 2012 08:20:00 -0000 [thread overview] Message-ID: <bug-51877-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51877 Bug #: 51877 Summary: [4.7 Regression] XEmacs miscompilation due to tail merging Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Keywords: wrong-code Severity: normal Priority: P3 Component: tree-optimization AssignedTo: jakub@gcc.gnu.org ReportedBy: jakub@gcc.gnu.org CC: vries@gcc.gnu.org extern void abort (void); struct A { int a; char b[32]; } a, b; __attribute__((noinline, noclone)) struct A bar (int x) { struct A r; static int n; r.a = ++n; __builtin_memset (r.b, 0, sizeof (r.b)); r.b[0] = x; return r; } __attribute__((noinline, noclone)) void baz (void) { asm volatile ("" : : : "memory"); } __attribute__((noinline, noclone)) void foo (struct A *x, int y) { if (y == 6) a = bar (7); else *x = bar (7); baz (); } int main () { a = bar (3); b = bar (4); if (a.a != 1 || a.b[0] != 3 || b.a != 2 || b.b[0] != 4) abort (); foo (&b, 0); if (a.a != 1 || a.b[0] != 3 || b.a != 3 || b.b[0] != 7) abort (); foo (&b, 6); if (a.a != 4 || a.b[0] != 7 || b.a != 3 || b.b[0] != 7) abort (); return 0; } is miscompiled at -O2 (distilled from XEmacs). Tail merging surprisingly decides to tail merge the two calls, eventhough they have different lhs.
next reply other threads:[~2012-01-17 7:24 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-01-17 8:20 jakub at gcc dot gnu.org [this message] 2012-01-17 8:34 ` [Bug tree-optimization/51877] " jakub at gcc dot gnu.org 2012-01-17 10:36 ` rguenth at gcc dot gnu.org 2012-01-17 10:49 ` jakub at gcc dot gnu.org 2012-01-17 11:22 ` jakub at gcc dot gnu.org
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