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From: "Joost.VandeVondele at pci dot uzh.ch" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/47657] missed vectorization
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47657

--- Comment #2 from Joost VandeVondele <Joost.VandeVondele at pci dot uzh.ch> 2011-02-09 11:25:42 UTC ---
Created attachment 23283
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23283
testcase including timing routine,  last number is flop rate.

the cray compiler is supposed to *not* interchange loops, as I'm using:

ftn -O3,ipa0,nointerchange,vector3  testcase.f90

to compile. This gives about 5.6Gflops.

Unrolling still seems to happen (there are 16 mults in the inner loop), and 

ftn -O3,ipa0,nointerchange,vector3,unroll0  testcase.f90 yields poor
performance (2.3Gflops).

Gfortran 4.5 yields 3.424Gflops :

gfortran -O3 -ffast-math -funroll-loops -march=native  testcase.f90