Create type IDs based on reference counts.

lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h

Index: lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h
diff --git a/lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h b/lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h
index 9e9954883a61406ab6a946e552bf6ab93aed6a56..8b30ee3ce2b3671d8ff91a5d7a640abca3d1f214 100644
--- a/lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h
+++ b/lib/Bitcode/NaCl/Writer/NaClValueEnumerator.h
@@ -42,8 +42,17 @@ public:
   // For each value, we remember its Value* and occurrence frequency.
   typedef std::vector<std::pair<const Value*, unsigned> > ValueList;
 private:
+  // Defines unique ID's for each type.
   typedef DenseMap<Type*, unsigned> TypeMapType;
   TypeMapType TypeMap;
+  // Defines the number of references to each type. If defined,
+  // we are in the first pass of collecting types, and reference counts
+  // should be added to the map. If undefined, we are in the second pass
+  // that actually assigns type IDs, based on frequency counts found in
+  // the first pass.
+  typedef TypeMapType TypeCountMapType;
+  TypeCountMapType* TypeCountMap;
+
   TypeList Types;
 
   typedef DenseMap<const Value*, unsigned> ValueMapType;
@@ -152,6 +161,7 @@ public:
   void purgeFunction();
 
 private:
+  void OptimizeTypes(const Module *M);
   void OptimizeConstants(unsigned CstStart, unsigned CstEnd);
 
   void EnumerateMDNodeOperands(const MDNode *N);