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* [Bug tree-optimization/41186] New: VN doesn't look through non-aliasing by offset memcpy @ 2009-08-29 12:43 rguenth at gcc dot gnu dot org 2009-08-29 13:49 ` [Bug tree-optimization/41186] " rguenth at gcc dot gnu dot org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2009-08-29 12:43 UTC (permalink / raw) To: gcc-bugs The C++ FE now creates memcpy for class copies to avoid copying objects in tail-padding. struct Foo { Foo() {}; int i; short f; }; struct Bar : public Foo { Bar() {}; short b; }; extern "C" void abort(void); int main() { Bar b1, b2; b2.i = 0; b1.f = 0; b1.b = 1; b2.f = 1; b2.b = 2; static_cast<Foo&>(b1) = static_cast<Foo&>(b2); if (b1.i != 0 || b1.b != 1) abort (); if (b1.f != 1) abort (); return 0; } The alias-oracle does consider the memcpy to clobber b1.b and the look-through doesn't find b1.f or b1.i either. Note that with combining the tests like if (b1.i != 0 || b1.b != 1 || b1.f != 1) abort (); fold creates a BIT_FIELD_REF covering both b and f which confuses us even more. But I have considered this a bad habit of fold earlier. -- Summary: VN doesn't look through non-aliasing by offset memcpy Product: gcc Version: 4.5.0 Status: UNCONFIRMED Keywords: missed-optimization, alias Severity: enhancement Priority: P3 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: rguenth at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41186 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/41186] VN doesn't look through non-aliasing by offset memcpy 2009-08-29 12:43 [Bug tree-optimization/41186] New: VN doesn't look through non-aliasing by offset memcpy rguenth at gcc dot gnu dot org @ 2009-08-29 13:49 ` rguenth at gcc dot gnu dot org 2009-08-30 11:52 ` rguenth at gcc dot gnu dot org 2009-09-26 15:28 ` rguenth at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2009-08-29 13:49 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from rguenth at gcc dot gnu dot org 2009-08-29 13:49 ------- Mine. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot |dot org |org Status|UNCONFIRMED |ASSIGNED Ever Confirmed|0 |1 Last reconfirmed|0000-00-00 00:00:00 |2009-08-29 13:49:04 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41186 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/41186] VN doesn't look through non-aliasing by offset memcpy 2009-08-29 12:43 [Bug tree-optimization/41186] New: VN doesn't look through non-aliasing by offset memcpy rguenth at gcc dot gnu dot org 2009-08-29 13:49 ` [Bug tree-optimization/41186] " rguenth at gcc dot gnu dot org @ 2009-08-30 11:52 ` rguenth at gcc dot gnu dot org 2009-09-26 15:28 ` rguenth at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2009-08-30 11:52 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from rguenth at gcc dot gnu dot org 2009-08-30 11:52 ------- Subject: Bug 41186 Author: rguenth Date: Sun Aug 30 11:52:13 2009 New Revision: 151226 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=151226 Log: 2009-08-30 Richard Guenther <rguenther@suse.de> PR tree-optimization/41186 * tree-ssa-alias.c (ptr_deref_may_alias_ref_p): Remove. (ao_ref_init_from_ptr_and_size): New function. (ref_maybe_used_by_call_p_1): Be more precise tracking used ranges for builtin functions. (ref_maybe_used_by_call_p): Adjust. (call_may_clobber_ref_p_1): Be more precise tracking clobbered ranges for builtin functions. * tree-ssa-alias.h (ao_ref_init_from_ptr_and_size): Declare. * g++.dg/torture/pr41186.C: New testcase. * g++.dg/tree-ssa/pr41186.C: Likewise. Added: trunk/gcc/testsuite/g++.dg/torture/pr41186.C trunk/gcc/testsuite/g++.dg/tree-ssa/pr41186.C Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-ssa-alias.c trunk/gcc/tree-ssa-alias.h -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41186 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/41186] VN doesn't look through non-aliasing by offset memcpy 2009-08-29 12:43 [Bug tree-optimization/41186] New: VN doesn't look through non-aliasing by offset memcpy rguenth at gcc dot gnu dot org 2009-08-29 13:49 ` [Bug tree-optimization/41186] " rguenth at gcc dot gnu dot org 2009-08-30 11:52 ` rguenth at gcc dot gnu dot org @ 2009-09-26 15:28 ` rguenth at gcc dot gnu dot org 2 siblings, 0 replies; 4+ messages in thread From: rguenth at gcc dot gnu dot org @ 2009-09-26 15:28 UTC (permalink / raw) To: gcc-bugs ------- Comment #3 from rguenth at gcc dot gnu dot org 2009-09-26 15:27 ------- Fixed. Related is PR13954 where VN does not look through (partial) struct copies using memcpy. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|ASSIGNED |RESOLVED Resolution| |FIXED Target Milestone|--- |4.5.0 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41186 ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2009-09-26 15:28 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2009-08-29 12:43 [Bug tree-optimization/41186] New: VN doesn't look through non-aliasing by offset memcpy rguenth at gcc dot gnu dot org 2009-08-29 13:49 ` [Bug tree-optimization/41186] " rguenth at gcc dot gnu dot org 2009-08-30 11:52 ` rguenth at gcc dot gnu dot org 2009-09-26 15:28 ` rguenth at gcc dot gnu dot org
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