Remove some of the cache validity checks for for-in enumeration. We...

src/handles.cc

 // Copyright 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 530 matching lines @@
       result = enum_fun(info);
     }
   }
   return result;
 }
 
 
 Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSObject> object,
                                           KeyCollectionType type) {
   Handle<FixedArray> content = Factory::empty_fixed_array();
+  Handle<JSObject> arguments_boilerplate =
+      Handle<JSObject>(
+          Top::context()->global_context()->arguments_boilerplate());
+  Handle<JSFunction> arguments_function =
+      Handle<JSFunction>(
+          JSFunction::cast(arguments_boilerplate->map()->constructor()));
 
   // Only collect keys if access is permitted.
   for (Handle<Object> p = object;
        *p != Heap::null_value();
        p = Handle<Object>(p->GetPrototype())) {
     Handle<JSObject> current(JSObject::cast(*p));
 
     // Check access rights if required.
     if (current->IsAccessCheckNeeded() &&
       !Top::MayNamedAccess(*current, Heap::undefined_value(),
                            v8::ACCESS_KEYS)) {
       Top::ReportFailedAccessCheck(*current, v8::ACCESS_KEYS);
       break;
     }
 
     // Compute the element keys.
     Handle<FixedArray> element_keys =
         Factory::NewFixedArray(current->NumberOfEnumElements());
     current->GetEnumElementKeys(*element_keys);
     content = UnionOfKeys(content, element_keys);
 
     // Add the element keys from the interceptor.
     if (current->HasIndexedInterceptor()) {
       v8::Handle<v8::Array> result =
           GetKeysForIndexedInterceptor(object, current);
       if (!result.IsEmpty())
         content = AddKeysFromJSArray(content, v8::Utils::OpenHandle(*result));
     }
 
-    // Compute the property keys.
-    content = UnionOfKeys(content, GetEnumPropertyKeys(current));
+    // We can cache the computed property keys if access checks are
+    // not needed and no interceptors are involved.
+    //
+    // We do not use the cache if the object has elements and
+    // therefore it does not make sense to cache the property names
+    // for arguments objects.  Arguments objects will always have
+    // elements.
+    bool cache_enum_keys =
+        ((current->map()->constructor() != *arguments_function) &&
+         !current->IsAccessCheckNeeded() &&
+         !current->HasNamedInterceptor() &&
+         !current->HasIndexedInterceptor());
+    // Compute the property keys and cache them if possible.
+    content =
+        UnionOfKeys(content, GetEnumPropertyKeys(current, cache_enum_keys));
 
     // Add the property keys from the interceptor.
     if (current->HasNamedInterceptor()) {
       v8::Handle<v8::Array> result =
           GetKeysForNamedInterceptor(object, current);
       if (!result.IsEmpty())
         content = AddKeysFromJSArray(content, v8::Utils::OpenHandle(*result));
     }
 
     // If we only want local properties we bail out after the first
     // iteration.
     if (type == LOCAL_ONLY)
       break;
   }
   return content;
 }
 
 
 Handle<JSArray> GetKeysFor(Handle<JSObject> object) {
   Counters::for_in.Increment();
   Handle<FixedArray> elements = GetKeysInFixedArrayFor(object,
                                                        INCLUDE_PROTOS);
   return Factory::NewJSArrayWithElements(elements);
 }
 
 
-Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object) {
+Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object,
+                                       bool cache_result) {
   int index = 0;
   if (object->HasFastProperties()) {
     if (object->map()->instance_descriptors()->HasEnumCache()) {
       Counters::enum_cache_hits.Increment();
       DescriptorArray* desc = object->map()->instance_descriptors();
       return Handle<FixedArray>(FixedArray::cast(desc->GetEnumCache()));
     }
     Counters::enum_cache_misses.Increment();
     int num_enum = object->NumberOfEnumProperties();
     Handle<FixedArray> storage = Factory::NewFixedArray(num_enum);
     Handle<FixedArray> sort_array = Factory::NewFixedArray(num_enum);
     Handle<DescriptorArray> descs =
         Handle<DescriptorArray>(object->map()->instance_descriptors());
     for (int i = 0; i < descs->number_of_descriptors(); i++) {
       if (descs->IsProperty(i) && !descs->IsDontEnum(i)) {
         (*storage)->set(index, descs->GetKey(i));
         PropertyDetails details(descs->GetDetails(i));
         (*sort_array)->set(index, Smi::FromInt(details.index()));
         index++;
       }
     }
     (*storage)->SortPairs(*sort_array, sort_array->length());
-    Handle<FixedArray> bridge_storage =
-        Factory::NewFixedArray(DescriptorArray::kEnumCacheBridgeLength);
-    DescriptorArray* desc = object->map()->instance_descriptors();
-    desc->SetEnumCache(*bridge_storage, *storage);
+    if (cache_result) {
+      Handle<FixedArray> bridge_storage =
+          Factory::NewFixedArray(DescriptorArray::kEnumCacheBridgeLength);
+      DescriptorArray* desc = object->map()->instance_descriptors();
+      desc->SetEnumCache(*bridge_storage, *storage);
+    }
     ASSERT(storage->length() == index);
     return storage;
   } else {
     int num_enum = object->NumberOfEnumProperties();
     Handle<FixedArray> storage = Factory::NewFixedArray(num_enum);
     Handle<FixedArray> sort_array = Factory::NewFixedArray(num_enum);
     object->property_dictionary()->CopyEnumKeysTo(*storage, *sort_array);
     return storage;
   }
 }
@@ skipping 135 matching lines @@
   Handle<Map> new_map = Factory::CopyMapDropTransitions(old_map);
   obj->set_map(*new_map);
   new_map->set_needs_loading(true);
   // Store the lazy loading info in the constructor field.  We'll
   // reestablish the constructor from the fixed array after loading.
   new_map->set_constructor(*arr);
   ASSERT(!obj->IsLoaded());
 }
 
 } }  // namespace v8::internal