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* [Bug tree-optimization/31375] New: missed loop-if transformation / branch reduction.
@ 2007-03-27 12:56 pluto at agmk dot net
2007-03-27 13:24 ` [Bug tree-optimization/31375] " rguenth at gcc dot gnu dot org
2007-03-27 18:01 ` pinskia at gcc dot gnu dot org
0 siblings, 2 replies; 3+ messages in thread
From: pluto at agmk dot net @ 2007-03-27 12:56 UTC (permalink / raw)
To: gcc-bugs
long condition( void );
long f1( void );
long f2( void );
void foo( void )
{
for ( ;; )
if ( condition() )
f1();
else
f2();
}
foo() could be transformed to bar():
void bar( void )
{
long (* f[ 2 ])() = { &f2, &f1 };
for ( ;; )
f[ condition() ]();
}
--
Summary: missed loop-if transformation / branch reduction.
Product: gcc
Version: 4.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: pluto at agmk dot net
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31375
^ permalink raw reply [flat|nested] 3+ messages in thread* [Bug tree-optimization/31375] missed loop-if transformation / branch reduction. 2007-03-27 12:56 [Bug tree-optimization/31375] New: missed loop-if transformation / branch reduction pluto at agmk dot net @ 2007-03-27 13:24 ` rguenth at gcc dot gnu dot org 2007-03-27 18:01 ` pinskia at gcc dot gnu dot org 1 sibling, 0 replies; 3+ messages in thread From: rguenth at gcc dot gnu dot org @ 2007-03-27 13:24 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from rguenth at gcc dot gnu dot org 2007-03-27 14:24 ------- Uh, an indirect call is much more expensive in general unless you can prove that the branch if (condition()) is completely random and so usually mispredicted. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31375 ^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/31375] missed loop-if transformation / branch reduction. 2007-03-27 12:56 [Bug tree-optimization/31375] New: missed loop-if transformation / branch reduction pluto at agmk dot net 2007-03-27 13:24 ` [Bug tree-optimization/31375] " rguenth at gcc dot gnu dot org @ 2007-03-27 18:01 ` pinskia at gcc dot gnu dot org 1 sibling, 0 replies; 3+ messages in thread From: pinskia at gcc dot gnu dot org @ 2007-03-27 18:01 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from pinskia at gcc dot gnu dot org 2007-03-27 19:01 ------- This is not even a size win for either x86-linux or powerpc{,64}-linux-gnu so closing as invalid. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31375 ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2007-03-27 18:01 UTC | newest] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2007-03-27 12:56 [Bug tree-optimization/31375] New: missed loop-if transformation / branch reduction pluto at agmk dot net 2007-03-27 13:24 ` [Bug tree-optimization/31375] " rguenth at gcc dot gnu dot org 2007-03-27 18:01 ` pinskia at gcc dot gnu dot org
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