diff --git a/llvm/lib/CodeGen/RegAlloc/InterferenceGraph.h b/llvm/lib/CodeGen/RegAlloc/InterferenceGraph.h
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+++ b/llvm/lib/CodeGen/RegAlloc/InterferenceGraph.h
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+/* Title:   InterferenceGraph.h
+   Author:  Ruchira Sasanka
+   Date:    July 20, 01
+   Purpose: Interference Graph used for register coloring.
+
+   Notes: 
+   Adj Info is  stored in the lower trangular matrix (i.e., row > col ) 
+
+   This class must be used in the following way:
+
+   * Construct class
+   * call addLRToIG as many times to add ALL LRs to this IG
+   * call createGraph to create the actual matrix
+   * Then setInterference, getInterference, mergeIGNodesOfLRs can be 
+     called as desired to modify the graph.
+   * Once the modifications to the graph are over, call 
+     setCurDegreeOfIGNodes() before pushing IGNodes on to stack for coloring.
+*/
+
+
+#ifndef  INTERFERENCE_GRAPH_H
+#define  INTERFERENCE_GRAPH_H
+
+
+#include "llvm/CodeGen/IGNode.h"
+
+typedef vector <IGNode *> IGNodeListType;
+
+
+class InterferenceGraph
+{
+  char **IG;                            // a poiner to the interference graph
+  unsigned int Size;                    // size of a side of the IG
+  RegClass *const RegCl;                // RegCl contains this IG
+  IGNodeListType IGNodeList;            // a list of all IGNodes in a reg class
+                            
+  // for asserting this IG node is infact in the IGNodeList of this class
+  inline void assertIGNode(const IGNode *const Node) const {     
+    assert( IGNodeList[ Node->getIndex() ] == Node );
+  }
+
+
+
+ public:
+
+  // the matrix is not yet created by the constructor. Call createGraph() 
+  // to create it after adding all IGNodes to the IGNodeList
+
+  InterferenceGraph(RegClass *const RC);
+  void createGraph();
+
+  void addLRToIG(LiveRange *const LR);
+
+  void setInterference(const LiveRange *const LR1,
+			      const LiveRange *const LR2 );
+
+  unsigned getInterference(const LiveRange *const LR1,
+				  const LiveRange *const LR2 ) const ;
+
+  void mergeIGNodesOfLRs(const LiveRange *const LR1, LiveRange *const LR2);
+
+  inline IGNodeListType &getIGNodeList() { return IGNodeList; } 
+
+  void setCurDegreeOfIGNodes();
+
+  void printIG() const;
+  void printIGNodeList() const;
+
+  ~InterferenceGraph();
+  
+
+};
+
+
+#endif
+