Yeah, I can try to do benchmarking with such optset instead of O3. Thanks, Igor
On Thu, Oct 17, 2013 at 2:19 PM, Richard Biener <richard.guent...@gmail.com> wrote: > On Wed, Oct 16, 2013 at 12:22 PM, Kyrill Tkachov <kyrylo.tkac...@arm.com> > wrote: >> On 16/10/13 10:37, pins...@gmail.com wrote: >>>> >>>> On Oct 15, 2013, at 6:58 AM, Igor Zamyatin <izamya...@gmail.com> wrote: >>>> Hi All! >>>> >>>> Is there any particular reason that matmul* modules from libgfortran >>>> are compiled with -O2 -ftree-vectorize? >>>> >>>> I see some regressions on Atom processor after r202980 >>>> (http://gcc.gnu.org/ml/gcc-cvs/2013-09/msg00846.html) >>>> >>>> Why not just use O3 for those modules? >>> >>> -O3 and -O2 -ftree-vectorize won't give much performance difference. What >>> you are seeing is the cost model needs improvement; at least for atom. >> >> Hi all, >> I think http://gcc.gnu.org/ml/gcc-patches/2013-09/msg01908.html introduced >> the new "cheap" vectoriser cost model that favors compilation time over >> runtime performance and is set as default for -O2. -O3 uses the "dynamic" >> model which potentially gives better runtime performance in exchange for >> longer compile times (if I understand the new rules correctly). >> Therefore, I'd expect -O3 to give a better vector performance than -O2... > > But this suggests to compile with -O2 -ftree-vectorize > -fvect-cost-model=dynamic, not building with -O3. > > Richard. > >> Kyrill >> >>
