[PATCH] Fix GraphTraits for "const CallGraphNode *" and "const CallGraph *"

[Speziale Ettore]

Hello,

GraphTraits specialization for "const CallGraphNode *" and "const CallGraph
*" seems to be broken. This example:

void foo(const CallGraph *G) {
  auto I = GraphTraits<const CallGraph *>::nodes_begin(G);
  auto K = I++;

  ...
}

void bar(const CallGraphNode *N) {
  auto I = GraphTraits<const CallGraphNode *>::nodes_begin(G);
  auto K = I++;

  ....
}

does not compile as the GraphTraits specialization does not use a
mapped_iterator, hence it is not possible to dereference a
CallGraphNode::CallRecord and get the corresponding const CallGraphNode *.

The attached patch fixes this problem using the same approach used for
non-const specialization.

Hope it could be useful,
Ettore Speziale
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diff --git a/include/llvm/Analysis/CallGraph.h b/include/llvm/Analysis/CallGraph.h
index 24fa99f..68a108b 100644
--- a/include/llvm/Analysis/CallGraph.h
+++ b/include/llvm/Analysis/CallGraph.h
@@ -417,13 +417,24 @@ template <> struct GraphTraits<CallGraphNode *> {
 
 template <> struct GraphTraits<const CallGraphNode *> {
   typedef const CallGraphNode NodeType;
-  typedef NodeType::const_iterator ChildIteratorType;
+
+  typedef CallGraphNode::CallRecord CGNPairTy;
+  typedef std::pointer_to_unary_function<CGNPairTy, const CallGraphNode *>
+  CGNDerefFun;
 
   static NodeType *getEntryNode(const CallGraphNode *CGN) { return CGN; }
+
+  typedef mapped_iterator<NodeType::const_iterator, CGNDerefFun>
+  ChildIteratorType;
+
   static inline ChildIteratorType child_begin(NodeType *N) {
-    return N->begin();
+    return map_iterator(N->begin(), CGNDerefFun(CGNDeref));
+  }
+  static inline ChildIteratorType child_end(NodeType *N) {
+    return map_iterator(N->end(), CGNDerefFun(CGNDeref));
   }
-  static inline ChildIteratorType child_end(NodeType *N) { return N->end(); }
+
+  static const CallGraphNode *CGNDeref(CGNPairTy P) { return P.second; }
 };
 
 template <>
@@ -450,12 +461,21 @@ template <>
 struct GraphTraits<const CallGraph *> : public GraphTraits<
                                             const CallGraphNode *> {
   static NodeType *getEntryNode(const CallGraph *CGN) {
-    return CGN->getExternalCallingNode();
+    return CGN->getExternalCallingNode(); // Start at the external node!
   }
+  typedef std::pair<const Function *, const CallGraphNode *> PairTy;
+  typedef std::pointer_to_unary_function<PairTy, const CallGraphNode &> DerefFun;
+
   // nodes_iterator/begin/end - Allow iteration over all nodes in the graph
-  typedef CallGraph::const_iterator nodes_iterator;
-  static nodes_iterator nodes_begin(const CallGraph *CG) { return CG->begin(); }
-  static nodes_iterator nodes_end(const CallGraph *CG) { return CG->end(); }
+  typedef mapped_iterator<CallGraph::const_iterator, DerefFun> nodes_iterator;
+  static nodes_iterator nodes_begin(const CallGraph *CG) {
+    return map_iterator(CG->begin(), DerefFun(CGdereference));
+  }
+  static nodes_iterator nodes_end(const CallGraph *CG) {
+    return map_iterator(CG->end(), DerefFun(CGdereference));
+  }
+
+  static const CallGraphNode &CGdereference(PairTy P) { return *P.second; }
 };
 
 } // End llvm namespace