http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56843
--- Comment #3 from Bill Schmidt <wschmidt at gcc dot gnu.org> 2013-04-05 15:03:26 UTC --- Looks like we can improve performance for three cases on P6 and later machines: - 32-bit reciprocal square root: remove two instructions - 32-bit reciprocal: remove three instructions - 64-bit reciprocal: remove one instruction The last is due to a subtle bug in the existing implementation.