Improve keyed loads on strings by using a new stub

src/ic.h

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 262 matching lines @@
  public:
   KeyedLoadIC() : IC(NO_EXTRA_FRAME) { ASSERT(target()->is_keyed_load_stub()); }
 
   Object* Load(State state, Handle<Object> object, Handle<Object> key);
 
   // Code generator routines.
   static void GenerateMiss(MacroAssembler* masm);
   static void GenerateInitialize(MacroAssembler* masm);
   static void GeneratePreMonomorphic(MacroAssembler* masm);
   static void GenerateGeneric(MacroAssembler* masm);
+  static void GenerateString(MacroAssembler* masm);
 
   // Generators for external array types. See objects.h.
   // These are similar to the generic IC; they optimize the case of
   // operating upon external array types but fall back to the runtime
   // for all other types.
   static void GenerateExternalArray(MacroAssembler* masm,
                                     ExternalArrayType array_type);
 
   // Clear the use of the inlined version.
   static void ClearInlinedVersion(Address address);
@@ skipping 13 matching lines @@
   }
   static Code* megamorphic_stub() {
     return Builtins::builtin(Builtins::KeyedLoadIC_Generic);
   }
   static Code* generic_stub() {
     return Builtins::builtin(Builtins::KeyedLoadIC_Generic);
   }
   static Code* pre_monomorphic_stub() {
     return Builtins::builtin(Builtins::KeyedLoadIC_PreMonomorphic);
   }
+  static Code* string_stub() {
+    return Builtins::builtin(Builtins::KeyedLoadIC_String);
+  }
   static Code* external_array_stub(JSObject::ElementsKind elements_kind);
 
   static void Clear(Address address, Code* target);
 
   // Support for patching the map that is checked in an inlined
   // version of keyed load.
   static bool PatchInlinedLoad(Address address, Object* map);
 
   friend class IC;
 };
@@ skipping 97 matching lines @@
   // The map is the new map that the inlined code should check against.
   static bool PatchInlinedStore(Address address, Object* map);
 
   friend class IC;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IC_H_