code: private void makeNextVariableID(ClassNode type, boolean useReferenceDirectly) {
          currentVariableIndex = nextVariableIndex;
          if ((type== ClassHelper.long_TYPE || type== ClassHelper.double_TYPE) && !useReferenceDirectly) {
              nextVariableIndex++;
          }
          nextVariableIndex++;
      }
docs: Calculates the index of the next free register stores it
  and sets the current variable index to the old value