Introduce a lookup cache class in the runtime system and use it for...

src/objects.h

Index: src/objects.h
===================================================================
--- src/objects.h	(revision 556)
+++ src/objects.h	(working copy)
@@ -58,6 +58,9 @@
 //           - HashTable
 //             - Dictionary
 //             - SymbolTable
+//             - CompilationCacheTable
+//             - MapCache
+//             - LookupCache
 //           - Context
 //           - GlobalContext
 //       - String
@@ -626,6 +629,7 @@
   inline bool IsSymbolTable();
   inline bool IsCompilationCacheTable();
   inline bool IsMapCache();
+  inline bool IsLookupCache();
   inline bool IsPrimitive();
   inline bool IsGlobalObject();
   inline bool IsJSGlobalObject();
@@ -1870,6 +1874,24 @@
 };
 
 
+// LookupCache.
+//
+// Maps a key consisting of a map and a name to an index within a
+// fast-case properties array.
+//
+// LookupCaches are used to avoid repeatedly searching instance
+// descriptors.
+class LookupCache: public HashTable<0, 2> {
+ public:
+  int Lookup(Map* map, String* name);
+  Object* Put(Map* map, String* name, int offset);
+  static inline LookupCache* cast(Object* obj);
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(LookupCache);
+};
+
+
 // Dictionary for keeping properties and elements in slow case.
 //
 // One element in the prefix is used for storing non-element