public RegisterSpecSet mutableCopy() {
    int len = specs.length;
    RegisterSpecSet copy = new RegisterSpecSet(len);

    for (int i = 0; i < len; i++) {
      RegisterSpec spec = specs[i];
      if (spec != null) {
        copy.put(spec);
      }
    }

    copy.size = size;

    return copy;
  }
Makes and return a mutable copy of this instance.

@return {@code non-null;} the mutable copy
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/code/RegisterSpecSet.java