public int[] getRegistersByFrequency() {
    int regCount = ssaMeth.getRegCount();
    Integer[] ret = new Integer[regCount];

    for (int i = 0; i < regCount; i++) {
      ret[i] = i;
    }

    Arrays.sort(
        ret,
        new Comparator<Integer>() {
          @Override
          public int compare(Integer o1, Integer o2) {
            return ssaMeth.getUseListForRegister(o2).size()
                - ssaMeth.getUseListForRegister(o1).size();
          }
        });

    int[] result = new int[regCount];

    for (int i = 0; i < regCount; i++) {
      result[i] = ret[i];
    }

    return result;
  }
<b>Note:</b> This method is not presently used.

@return a list of registers ordered by most-frequently-used to least-frequently-used. Each
    register is listed once and only once.
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/back/SsaToRop.java