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* [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size @ 2015-04-02 3:05 law at redhat dot com 2015-04-02 8:44 ` [Bug tree-optimization/65658] " rguenth at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: law at redhat dot com @ 2015-04-02 3:05 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65658 Bug ID: 65658 Summary: Jump threading too pessimistic when optimizing for size Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: law at redhat dot com Created attachment 35209 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35209&action=edit testcase, compile with -O2 -Wall note uninitialized warnings for SRA's variables and trivially threadable block in setup() The jump threader will cancel jump threads when optimizing for size and the block will need to be duplicated. But that heuristic fails for something a block like this: # _36 = PHI <1(2), 1(4), 0(7)> # problem$l3_101 = PHI <problem$l3_8(D)(2), problem$l3_8(D)(4), problem$l3_35(7)> # problem$l4_100 = PHI <problem$l4_124(D)(2), problem$l4_124(D)(4), problem$l4_34(7)> amt ={v} {CLOBBER}; if (_36 != 0) goto <bb 25>; else goto <bb 9>; All incoming edges are threadable and the block produces no code. It's really just a redirection block that's not recognized as such -- probably due to the clobber statement. The net result is we cancel the jump thread, get worse code and issue false positive warnings for uninitialized variables. All around a lose. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/65658] Jump threading too pessimistic when optimizing for size 2015-04-02 3:05 [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size law at redhat dot com @ 2015-04-02 8:44 ` rguenth at gcc dot gnu.org 2015-04-20 17:14 ` law at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu.org @ 2015-04-02 8:44 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65658 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |missed-optimization Status|UNCONFIRMED |NEW Last reconfirmed| |2015-04-02 Ever confirmed|0 |1 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- Confirmed. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/65658] Jump threading too pessimistic when optimizing for size 2015-04-02 3:05 [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size law at redhat dot com 2015-04-02 8:44 ` [Bug tree-optimization/65658] " rguenth at gcc dot gnu.org @ 2015-04-20 17:14 ` law at gcc dot gnu.org 2015-04-20 19:36 ` law at gcc dot gnu.org 2015-04-20 19:37 ` law at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: law at gcc dot gnu.org @ 2015-04-20 17:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65658 --- Comment #2 from Jeffrey A. Law <law at gcc dot gnu.org> --- Author: law Date: Mon Apr 20 17:13:52 2015 New Revision: 222242 URL: https://gcc.gnu.org/viewcvs?rev=222242&root=gcc&view=rev Log: PR tree-optimization/65658 * tree-ssa-threadupdate.c (redirection_block_p): Ignore clobber statements too. PR tree-optimization/65658 * gcc.dg/pr65658.c: New test. Added: trunk/gcc/testsuite/gcc.dg/pr65658.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-ssa-threadupdate.c ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/65658] Jump threading too pessimistic when optimizing for size 2015-04-02 3:05 [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size law at redhat dot com 2015-04-02 8:44 ` [Bug tree-optimization/65658] " rguenth at gcc dot gnu.org 2015-04-20 17:14 ` law at gcc dot gnu.org @ 2015-04-20 19:36 ` law at gcc dot gnu.org 2015-04-20 19:37 ` law at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: law at gcc dot gnu.org @ 2015-04-20 19:36 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65658 --- Comment #3 from Jeffrey A. Law <law at gcc dot gnu.org> --- Author: law Date: Mon Apr 20 19:35:50 2015 New Revision: 222247 URL: https://gcc.gnu.org/viewcvs?rev=222247&root=gcc&view=rev Log: PR tree-optimization/65658 * tree-ssa-threadupdate.c (redirection_block_p): Remove redundant test for GIMPLE_ASSIGN in last change. Modified: trunk/gcc/ChangeLog trunk/gcc/tree-ssa-threadupdate.c ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/65658] Jump threading too pessimistic when optimizing for size 2015-04-02 3:05 [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size law at redhat dot com ` (2 preceding siblings ...) 2015-04-20 19:36 ` law at gcc dot gnu.org @ 2015-04-20 19:37 ` law at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: law at redhat dot com @ 2015-04-20 19:37 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65658 Jeffrey A. Law <law at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #4 from Jeffrey A. Law <law at redhat dot com> --- Fixed with trunk commits. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2015-04-20 19:37 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2015-04-02 3:05 [Bug tree-optimization/65658] New: Jump threading too pessimistic when optimizing for size law at redhat dot com 2015-04-02 8:44 ` [Bug tree-optimization/65658] " rguenth at gcc dot gnu.org 2015-04-20 17:14 ` law at gcc dot gnu.org 2015-04-20 19:36 ` law at gcc dot gnu.org 2015-04-20 19:37 ` law at redhat dot com
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