http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59968
--- Comment #17 from H.J. Lu <hjl.tools at gmail dot com> --- Created attachment 31974 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31974&action=edit A micro-benchmark for BTS with register BTS with register operand is about 7-20% faster on Silvermont an Haswell.