[Bug tree-optimization/56309] -O3 optimizer generates conditional moves instead of compare and branch resulting in almost 2x slower code

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56309



Steven Bosscher <steven at gcc dot gnu.org> changed:



           What    |Removed                     |Added

----------------------------------------------------------------------------

           Keywords|                            |missed-optimization

          Component|target                      |tree-optimization



--- Comment #13 from Steven Bosscher <steven at gcc dot gnu.org> 2013-02-14 
17:26:08 UTC ---

$ g++ --version

g++ (GCC) 4.7.2 ...

$ g++ -O3 -std=c++11 by-val-O3.ii ; ./a.out

Took 14.31 seconds total.

$ g++ -O3 -std=c++11 by-val-O3.ii -fvect-cost-model ; ./a.out

Took 14.31 seconds total.

$ g++ -O3 -std=c++11 by-val-O3.ii -fno-tree-vectorize ; ./a.out

Took 10.25 seconds total.