What information does GCC Profile Guided Optimization (PGO) collect and which optimizations use it?
-fprofile-generate enables -fprofile-arcs, -fprofile-values and -fvpt. -fprofile-use enables -fbranch-probabilities, -fvpt, -funroll-loops, -fpeel-loops and -ftracer Source: http://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Optimize-Options.html#Optimize-Options PS. Information about LTO also on that page.