docs: public static int previousSetBit(long v, int start) {
      if(start < 0) {
        return -1;
      }
      start = start < Long.SIZE ? start : Long.SIZE - 1;
      long cur = v & (LONG_ALL_BITS >>> -(start + 1));
      return cur == 0 ? -1 : cur == LONG_ALL_BITS ? 0 : 63 - Long.numberOfLeadingZeros(cur);
    }