Improve keyed loads on strings by using a new stub

src/ic.cc

 // 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 856 matching lines @@
 
     return object->GetProperty(*object, &lookup, *name, &attr);
   }
 
   // Do not use ICs for objects that require access checks (including
   // the global object).
   bool use_ic = FLAG_use_ic && !object->IsAccessCheckNeeded();
 
   if (use_ic) {
     Code* stub = generic_stub();
-    if (object->IsJSObject()) {
+    if (object->IsString() && key->IsNumber()) {
+      stub = string_stub();
+    } else if (object->IsJSObject()) {
       Handle<JSObject> receiver = Handle<JSObject>::cast(object);
       if (receiver->HasExternalArrayElements()) {
         stub = external_array_stub(receiver->GetElementsKind());
       }
     }
     set_target(stub);
     // For JSObjects that are not value wrappers and that do not have
     // indexed interceptors, we initialize the inlined fast case (if
     // present) by patching the inlined map check.
     if (object->IsJSObject() &&
@@ skipping 527 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal