http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46900
Tobias Burnus <burnus at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |4.6.0 Summary|50% slowdown when linking |[4.6 Regression] 50% |with LTO in a single step |slowdown when linking with | |LTO in a single step --- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> 2010-12-12 10:39:17 UTC --- The linkage seems to be a regression. If I compile with GCC 4.5, I get for the direct dgemm call the same performance if I link in a single step: $ gfortran-4.5 -fexternal-blas -flto -O3 -ffast-math -march=native \ test.f90 dgemm.f lsame.f xerbla.f $ ./a.out Time, MATMUL: 1.4160880 53.480084765505403 dgemm: 1.0840679 56.452265589399069 (I don't understand why the MATMUL part differs that much - it should call the same BLAS function [via the same GCC 4.6 libgfortran.so wrapper] and LTO should not affect it.)