docs: private boolean doReachedUseDataFlow()
      {
          itsLiveOnExitSet.clear();
          if (itsSuccessors != null) {
              for (int i = 0; i < itsSuccessors.length; i++) {
                  itsLiveOnExitSet.or(itsSuccessors[i].itsLiveOnEntrySet);
              }
          }
          return updateEntrySet(itsLiveOnEntrySet, itsLiveOnExitSet,
                                itsUseBeforeDefSet, itsNotDefSet);
      }