From 9c8a9af5afb5459fb7949d4468c5a2abe02baf2c Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Wed, 3 Oct 2007 21:24:38 +0000
Subject: [PATCH] Add a GraphTraits partial specialization to make the inverse
 of an inverse be the same as the underlying graph.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42592 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/ADT/GraphTraits.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/llvm/ADT/GraphTraits.h b/include/llvm/ADT/GraphTraits.h
index 99a69b8cc87..853615e2514 100644
--- a/include/llvm/ADT/GraphTraits.h
+++ b/include/llvm/ADT/GraphTraits.h
@@ -78,6 +78,26 @@ struct Inverse {
   inline Inverse(GraphType &G) : Graph(G) {}
 };
 
+// Provide a partial specialization of GraphTraits so that the inverse of an inverse
+// falls back to the original graph.
+template<class T>
+struct GraphTraits<Inverse<Inverse<T> > > {
+  typedef typename GraphTraits<T>::NodeType NodeType;
+  typedef typename GraphTraits<T>::ChildIteratorType ChildIteratorType;
+  
+  static NodeType *getEntryNode(Inverse<Inverse<T> > *G) {
+    return GraphTraits<T>::getEntryNode(G.Graph.Graph);
+  }
+  
+  static ChildIteratorType child_begin(NodeType* N) {
+    return GraphTraits<T>::child_begin(N);
+  }
+  
+  static ChildIteratorType child_end(NodeType* N) {
+    return GraphTraits<T>::child_end(N);
+  }
+};
+
 } // End llvm namespace
 
 #endif