[Bug target/38306] [4.4/4.5/4.6 Regression] 15% slowdown w.r.t. 4.3 of computational kernel on some architectures

[Joost.VandeVondele at pci dot uzh.ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38306

--- Comment #19 from Joost VandeVondele <Joost.VandeVondele at pci dot uzh.ch> 2011-02-20 16:17:33 UTC ---
(In reply to comment #18)
> Hello Joost, could you please check if this is still a problem in GCC 4.6?

I think it still is a minor problem, but (without   -fschedule-insns) somewhat
less pronounced (the old hardware is gone, this might make a difference):

4.3 branch

> gfortran -O3 -march=native -funroll-loops  -ffast-math   -fschedule-insns test.f90 ; ./a.out 
Time for evaluation [s]:                        3.478
> gfortran -O3 -march=native -funroll-loops  -ffast-math   test.f90 ; ./a.out 
Time for evaluation [s]:                        4.367

4.5 branch

> gfortran -O3 -march=native -funroll-loops  -ffast-math   -fschedule-insns test.f90 ; ./a.out 
Time for evaluation [s]:                        4.839
> gfortran -O3 -march=native -funroll-loops  -ffast-math  test.f90 ; ./a.out 
Time for evaluation [s]:                        4.524

4.6 branch
> gfortran -O3 -march=native -funroll-loops  -ffast-math   -fschedule-insns test.f90 ; ./a.out 
Time for evaluation [s]:                        4.997
> gfortran -O3 -march=native -funroll-loops  -ffast-math   test.f90 ; ./a.out 
Time for evaluation [s]:                        4.547

FYI: -march=amdfam10 -mcx16 -msahf -mpopcnt -mabm
model name      : AMD Opteron(tm) Processor 6176 SE