private void addInterfence(int newReg, int oldReg) {
    newRegInterference.ensureCapacity(newReg + 1);

    while (newReg >= newRegInterference.size()) {
      newRegInterference.add(new BitIntSet(newReg + 1));
    }

    oldRegInterference.mergeInterferenceSet(oldReg, newRegInterference.get(newReg));
  }
Adds a register's interference set to the interference list, growing it if necessary.

@param newReg register in new namespace
@param oldReg register in old namespace
android/android_framework/dex-maker/src/main/java/com/android/dx/ssa/InterferenceRegisterMapper.java