Allow inline caching for getting the length of string wrapper objects.

src/ic.cc

 // Copyright 2006-2008 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 435 matching lines @@
 
 
 Object* LoadIC::Load(State state, Handle<Object> object, Handle<String> name) {
   // If the object is undefined or null it's illegal to try to get any
   // of its properties; throw a TypeError in that case.
   if (object->IsUndefined() || object->IsNull()) {
     return TypeError("non_object_property_load", object, name);
   }
 
   if (FLAG_use_ic) {
-    // Use specialized code for getting the length of strings.
-    if (object->IsString() && name->Equals(Heap::length_symbol())) {
+    // Use specialized code for getting the length of strings and
+    // string wrapper objects.  The length property of string wrapper
+    // objects is read-only and therefore always returns the length of
+    // the underlying string value.  See ECMA-262 15.5.5.1.
+    if ((object->IsString() || object->IsStringWrapper()) &&
+        name->Equals(Heap::length_symbol())) {
+      HandleScope scope;
+      // Get the string if we have a string wrapper object.
+      if (object->IsJSValue()) {
+        object = Handle<Object>(Handle<JSValue>::cast(object)->value());
+      }
 #ifdef DEBUG
       if (FLAG_trace_ic) PrintF("[LoadIC : +#length /string]\n");
 #endif
       Code* target = NULL;
       target = Builtins::builtin(Builtins::LoadIC_StringLength);
       set_target(target);
       StubCache::Set(*name, HeapObject::cast(*object)->map(), target);
       return Smi::FromInt(String::cast(*object)->length());
     }
 
@@ skipping 709 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal