boolean inSameSubroutine(final Label block) {
        if ((status & VISITED) == 0 || (block.status & VISITED) == 0) {
            return false;
        }
        for (int i = 0; i < srcAndRefPositions.length; ++i) {
            if ((srcAndRefPositions[i] & block.srcAndRefPositions[i]) != 0) {
                return true;
            }
        }
        return false;
    }