On Fri, Apr 27, 2012 at 3:30 PM, Paolo Bonzini <bonz...@gnu.org> wrote: > tzcnt is encoded as "rep;bsf" and unlike lzcnt is a drop-in replacement > if we don't care about the flags (it has the same semantics for non-zero > values). > > Since bsf is usually slower, just emit tzcnt unconditionally. However, > write it as rep;bsf unless -mbmi is in use, to cater for old assemblers.
Please emit "rep;bsf" when optimize_insn_for_speed_p () is true. > Bootstrapped on a non-BMI x86_64-linux host, regtest in progress. > Ok for mainline? OK with the optimize_insn_for_speed_p conditional. Thanks, Uros.
