------- Additional Comments From steven at gcc dot gnu dot org 2005-07-15
11:52 -------
Average (of three runs) user times:
(1) is -march=i686 -O3 -fomit-frame-pointer
(2) is -march=i686 -O3 -funroll-loops -fomit-frame-pointer
(3) is -march=i686 -O3 -funroll-loops -fomit-frame-pointer -fprofile-use
(1) user 0m6.949s
(2) user 0m8.565s
(3) user 0m8.671s
Note that -fprofile-generate and -fprofile-use automatically enable loop
unrolling as well. So it looks like this is a non-bug, you're just being
bitten by loop unrolling, which seems to be the cause of the slowdowns in
this case.
I did the same timings on an AMD64 box, and there the times for the three
different binaries were roughly the same.
Could you try to see if your timings are poor without profiling but with
loop unrolling enabled?
--
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21527
