https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78683
--- Comment #1 from Segher Boessenkool <segher at gcc dot gnu.org> --- Author: segher Date: Fri Dec 9 19:31:06 2016 New Revision: 243499 URL: https://gcc.gnu.org/viewcvs?rev=243499&root=gcc&view=rev Log: rs6000: clz/ctz/ffs improvement (PR78683) On CPUs that implement popcnt[wd] but not cnttz[wd] we can do better for the ctz sequences than we do today. CL[TZ]_DEFINED_VALUE_AT_ZERO can return 2, since we always return the same fixed value (only dependent on TARGET_* options). PR target/78683 * config/rs6000/rs6000.h (CLZ_DEFINED_VALUE_AT_ZERO): Use GET_MODE_BITSIZE. Return 2. (CTZ_DEFINED_VALUE_AT_ZERO): Use GET_MODE_BITSIZE. Return 2. Handle TARGET_POPCNTD the same as TARGET_CTZ. * config/rs6000/rs6000.md (ctz<mode>2): Reimplement. (ffs<mode>2): Reimplement. Modified: trunk/gcc/ChangeLog trunk/gcc/config/rs6000/rs6000.h trunk/gcc/config/rs6000/rs6000.md
