[Bug rtl-optimization/21527] BYTEmark bitmap test: Regression with Profiled Optimization

[steven at gcc dot gnu dot org]

------- 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
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             Status|ASSIGNED                    |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21527