@Override
          public int compare(Integer o1, Integer o2) {
            return ssaMeth.getUseListForRegister(o2).size()
                - ssaMeth.getUseListForRegister(o1).size();
          }
<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