// make sure we evacuate the oldbucket corresponding
	// to the bucket we're about to use
	evacuate_faststr(t, h, bucket&h.oldbucketmask())

	// evacuate one more oldbucket to make progress on growing
	if h.growing() {
		evacuate_faststr(t, h, h.nevacuate)
	}
}

func evacuate_faststr(t *maptype, h *hmap, oldbucket uintptr) {
	b := (*bmap)(add(h.oldbuckets, oldbucket*uintptr(t.BucketSize)))