http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
Summary: Certain expressions take an extremely long time for no
apparent reason
Product: gcc
Version: 4.4.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
John Peyton changed:
What|Removed |Added
Keywords||missed-optimization
--- Comment #1 from Joh
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
--- Comment #2 from John Peyton 2011-05-24 19:16:20
UTC ---
Created attachment 24350
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24350
This is a minimal example of an expression that takes longer to evaluate than
it should. Run the slight
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
--- Comment #3 from John Peyton 2011-05-24 19:16:51
UTC ---
Created attachment 24351
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24351
Finally, this is a preprocessed version of the minimal case.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
John Peyton changed:
What|Removed |Added
Severity|normal |minor
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
--- Comment #5 from John Peyton 2011-05-24 21:26:49
UTC ---
> Maybe you are getting subnormals which causes a huge performance decrease.
It looks like that might indeed be the case. It didn't seem to happen with ICC
though. Is it possible that o
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49148
--- Comment #7 from John Peyton 2011-05-25 14:40:56
UTC ---
> Try -ffast-math (the default for ICC) which disables subnormals.
Thanks, this helped it run much faster!
I noticed it still takes longer to divide by 3.0 than by 4.0. More
specifical
