http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60496
--- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> --- For 4.9 you can add -mtune-ctrl=^use_ffreep to your compile flags: "-m32 -O2 -march=i386 -mtune=athlon -mtune-ctrl=^use_ffreep" -mdump-tune-features flag will print all fine-tuning options.