private void countUsed() {
        isChanged = true;
        boolean firstTime = true;
        while (isChanged) {
            //System.out.println("AGAIN!!!");
            if (firstTime)
                firstTime = false;
            else
                isChanged = false;
            for (BaseBlock b : cfg.dfs())
                markBB.put(b, false);

            //countLatest(); -at  the beginning of every rec fo fo every statement
            recCountUsed(last, null);
        }
    }