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* [Bug tree-optimization/30708] New: [4.1 Regression] Aliasing miscompilation @ 2007-02-05 13:21 jakub at gcc dot gnu dot org 2007-02-05 14:19 ` [Bug tree-optimization/30708] " rguenth at gcc dot gnu dot org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: jakub at gcc dot gnu dot org @ 2007-02-05 13:21 UTC (permalink / raw) To: gcc-bugs struct obj_symbol { struct obj_symbol *next; unsigned int size; }; struct common_entry { struct common_entry *next; struct obj_symbol *sym; }; extern void do_something(struct obj_symbol *sym); void obj_allocate_commons(struct obj_symbol *sym) { struct common_entry *common_head = ((void *)0); for (; sym ; sym = sym->next) { struct common_entry **p, *n; for (p = &common_head; *p ; p = &(*p)->next) if (sym->size <= (*p)->sym->size) break; n = __builtin_alloca (sizeof(*n)); n->next = *p; n->sym = sym; *p = n; } { struct common_entry *p; for (p = common_head; p ; p = p->next) do_something(p->sym); } } is miscompiled on gcc-4_1-branch at least on x84_64-linux, with -O2 and above (but not with -fno-strict-aliasing). The common_head = NULL initialization is removed as dead during 1st DCE pass, but from quick skimming the reason for that seems to be incorrect aliasing information. -- Summary: [4.1 Regression] Aliasing miscompilation Product: gcc Version: 4.1.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: jakub at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30708 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/30708] [4.1 Regression] Aliasing miscompilation 2007-02-05 13:21 [Bug tree-optimization/30708] New: [4.1 Regression] Aliasing miscompilation jakub at gcc dot gnu dot org @ 2007-02-05 14:19 ` rguenth at gcc dot gnu dot org 2007-02-21 15:17 ` rguenth at gcc dot gnu dot org 2008-07-04 15:57 ` jsm28 at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2007-02-05 14:19 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from rguenth at gcc dot gnu dot org 2007-02-05 14:19 ------- Confirmed. Maybe related to PR30088. The first alias dump at -O2 (-O -fstrict-aliasing is fine) has <bb 0>: # common_head_5 = V_MUST_DEF <common_head_4>; common_head = 0B; ... <L0>:; p_10 = &common_head; goto <bb 4> (<L3>); <L1>:; # VUSE <TMT.6_24>; D.1631_16 = sym_1->size; # VUSE <HEAP.5_22>; D.1632_17 = *p_2; ... # p_2 = PHI <p_10(1), p_21(3)>; <L3>:; # VUSE <HEAP.5_22>; D.1632_11 = *p_2; if (D.1632_11 != 0B) goto <L1>; else goto <L4>; so we have both HEAP.5 and common_head_5 used as tags for common_heap. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Keywords| |alias, wrong-code Last reconfirmed|0000-00-00 00:00:00 |2007-02-05 14:19:20 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30708 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/30708] [4.1 Regression] Aliasing miscompilation 2007-02-05 13:21 [Bug tree-optimization/30708] New: [4.1 Regression] Aliasing miscompilation jakub at gcc dot gnu dot org 2007-02-05 14:19 ` [Bug tree-optimization/30708] " rguenth at gcc dot gnu dot org @ 2007-02-21 15:17 ` rguenth at gcc dot gnu dot org 2008-07-04 15:57 ` jsm28 at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2007-02-21 15:17 UTC (permalink / raw) To: gcc-bugs -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |4.1.3 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30708 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/30708] [4.1 Regression] Aliasing miscompilation 2007-02-05 13:21 [Bug tree-optimization/30708] New: [4.1 Regression] Aliasing miscompilation jakub at gcc dot gnu dot org 2007-02-05 14:19 ` [Bug tree-optimization/30708] " rguenth at gcc dot gnu dot org 2007-02-21 15:17 ` rguenth at gcc dot gnu dot org @ 2008-07-04 15:57 ` jsm28 at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: jsm28 at gcc dot gnu dot org @ 2008-07-04 15:57 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from jsm28 at gcc dot gnu dot org 2008-07-04 15:57 ------- Closing 4.1 branch. -- jsm28 at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Known to fail|4.1.0 4.1.1 4.1.2 |4.1.0 4.1.1 4.1.2 4.1.3 Known to work|4.0.3 |4.0.3 4.2.0 Resolution| |FIXED Target Milestone|4.1.3 |4.2.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30708 ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-07-04 15:57 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2007-02-05 13:21 [Bug tree-optimization/30708] New: [4.1 Regression] Aliasing miscompilation jakub at gcc dot gnu dot org 2007-02-05 14:19 ` [Bug tree-optimization/30708] " rguenth at gcc dot gnu dot org 2007-02-21 15:17 ` rguenth at gcc dot gnu dot org 2008-07-04 15:57 ` jsm28 at gcc dot gnu dot org
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