STEPSIZE
if unlikely(op - ref < STEPSIZE) {
op += STEPSIZE - 4;
cpy = op + length - (STEPSIZE - 4);
while likely(ip < matchlimit - (STEPSIZE - 1)) {
ip += STEPSIZE;
ref += STEPSIZE;
while (ip < matchlimit - (STEPSIZE - 1)) {
ip += STEPSIZE;
ref += STEPSIZE;
if unlikely(op - ref < STEPSIZE) {
op += STEPSIZE - 4;
cpy = op + length - (STEPSIZE - 4);