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* [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful
@ 2009-09-26 18:02 arjan at linux dot intel dot com
2009-09-26 18:02 ` [Bug c/41477] " arjan at linux dot intel dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: arjan at linux dot intel dot com @ 2009-09-26 18:02 UTC (permalink / raw)
To: gcc-bugs
(see attached testcases; testcase.c shows the problem, testcase2.c shows that
reorging the code works around it)
it appears that gcc does not realize that after
if (variable < 1 || variable > 10)
return -1;
the "variable" is in the range [1..10], likely because the execution of the
second check is optional due to the ||.
in a typical __builtin_object_size() scenario, like
if (__builtin_object_size(foo) < variable)
some_error();
where foo is 10 bytes in size, this means the check does not get optimized out.
--
Summary: gcc does not optimize a case that it should to make
__builtin_object_size() more useful
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: arjan at linux dot intel dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477
^ permalink raw reply [flat|nested] 5+ messages in thread* [Bug c/41477] gcc does not optimize a case that it should to make __builtin_object_size() more useful 2009-09-26 18:02 [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful arjan at linux dot intel dot com @ 2009-09-26 18:02 ` arjan at linux dot intel dot com 2009-09-26 18:02 ` arjan at linux dot intel dot com ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: arjan at linux dot intel dot com @ 2009-09-26 18:02 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from arjan at linux dot intel dot com 2009-09-26 18:02 ------- Created an attachment (id=18658) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18658&action=view) testcase showing the missed optimization -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/41477] gcc does not optimize a case that it should to make __builtin_object_size() more useful 2009-09-26 18:02 [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful arjan at linux dot intel dot com 2009-09-26 18:02 ` [Bug c/41477] " arjan at linux dot intel dot com @ 2009-09-26 18:02 ` arjan at linux dot intel dot com 2009-09-26 18:20 ` [Bug tree-optimization/41477] " pinskia at gcc dot gnu dot org 2009-09-26 18:22 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: arjan at linux dot intel dot com @ 2009-09-26 18:02 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from arjan at linux dot intel dot com 2009-09-26 18:02 ------- Created an attachment (id=18659) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18659&action=view) testcase that shows a slight reorder of the code works around the issue -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/41477] gcc does not optimize a case that it should to make __builtin_object_size() more useful 2009-09-26 18:02 [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful arjan at linux dot intel dot com 2009-09-26 18:02 ` [Bug c/41477] " arjan at linux dot intel dot com 2009-09-26 18:02 ` arjan at linux dot intel dot com @ 2009-09-26 18:20 ` pinskia at gcc dot gnu dot org 2009-09-26 18:22 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2009-09-26 18:20 UTC (permalink / raw) To: gcc-bugs ------- Comment #3 from pinskia at gcc dot gnu dot org 2009-09-26 18:20 ------- This has been fixed since 4.4.0. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/41477] gcc does not optimize a case that it should to make __builtin_object_size() more useful 2009-09-26 18:02 [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful arjan at linux dot intel dot com ` (2 preceding siblings ...) 2009-09-26 18:20 ` [Bug tree-optimization/41477] " pinskia at gcc dot gnu dot org @ 2009-09-26 18:22 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2009-09-26 18:22 UTC (permalink / raw) To: gcc-bugs ------- Comment #4 from pinskia at gcc dot gnu dot org 2009-09-26 18:22 ------- *** This bug has been marked as a duplicate of 30317 *** -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |DUPLICATE http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41477 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2009-09-26 18:22 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2009-09-26 18:02 [Bug c/41477] New: gcc does not optimize a case that it should to make __builtin_object_size() more useful arjan at linux dot intel dot com 2009-09-26 18:02 ` [Bug c/41477] " arjan at linux dot intel dot com 2009-09-26 18:02 ` arjan at linux dot intel dot com 2009-09-26 18:20 ` [Bug tree-optimization/41477] " pinskia at gcc dot gnu dot org 2009-09-26 18:22 ` pinskia at gcc dot gnu dot org
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