protected IntSet getPossibleTargetNumbers(CallSiteReference site) {
      Object t = targets.get(site.getProgramCounter());

      if (t == null) {
        return null;
      } else if (t instanceof CGNode) {
        return SparseIntSet.singleton(getCallGraph().getNumber((CGNode) t));
      } else {
        return (IntSet) t;
      }
    }
 public SparseIntSet getSources(int i) {
   return SparseIntSet.singleton(i);
 }
 public SparseIntSet getTargets(int i) {
   return SparseIntSet.singleton(i);
 }