[builtins] Speedup Object.keys by adding a fast path for objects without elements, interceptors, ...

src/builtins.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/builtins.h"
 
 #include "src/api.h"
 #include "src/api-natives.h"
 #include "src/arguments.h"
 #include "src/base/once.h"
@@ skipping 1748 matching lines @@
 }
 
 
 // ES6 section 19.1.2.14 Object.keys ( O )
 BUILTIN(ObjectKeys) {
   HandleScope scope(isolate);
   Handle<Object> object = args.atOrUndefined(isolate, 1);
   Handle<JSReceiver> receiver;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, receiver,
                                      Object::ToObject(isolate, object));
+
   Handle<FixedArray> keys;
-  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
-      isolate, keys, JSReceiver::GetKeys(receiver, OWN_ONLY, ENUMERABLE_STRINGS,
-                                         CONVERT_TO_STRING));
-  return *isolate->factory()->NewJSArrayWithElements(keys);
+  int enum_length = receiver->map()->EnumLength();
+  if (enum_length != kInvalidEnumCacheSentinel) {
+    DCHECK(receiver->IsJSObject());
+    Handle<JSObject> js_object = Handle<JSObject>::cast(receiver);
+    DCHECK(!js_object->HasNamedInterceptor());
+    DCHECK(!js_object->IsAccessCheckNeeded());
+    DCHECK(!js_object->map()->has_hidden_prototype());
+    DCHECK(js_object->HasFastProperties());
+    if (js_object->elements() == isolate->heap()->empty_fixed_array()) {
+      keys = isolate->factory()->NewFixedArray(enum_length);
+      if (enum_length != 0) {
+        Handle<FixedArray> cache(
+            js_object->map()->instance_descriptors()->GetEnumCache());
+        keys = isolate->factory()->NewFixedArray(enum_length);
+        for (int i = 0; i < enum_length; i++) {
+          keys->set(i, cache->get(i));
+        }
+      }
+    }
+  }
+
+  if (keys.is_null()) {
+    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+        isolate, keys,
+        JSReceiver::GetKeys(receiver, OWN_ONLY, ENUMERABLE_STRINGS,
+                            CONVERT_TO_STRING));
+  }
+  return *isolate->factory()->NewJSArrayWithElements(keys, FAST_ELEMENTS);
 }
 
-
 BUILTIN(ObjectValues) {
   HandleScope scope(isolate);
   Handle<Object> object = args.atOrUndefined(isolate, 1);
   Handle<JSReceiver> receiver;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, receiver,
                                      Object::ToObject(isolate, object));
   Handle<FixedArray> values;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, values, JSReceiver::GetOwnValues(receiver, ENUMERABLE_STRINGS));
   return *isolate->factory()->NewJSArrayWithElements(values);
@@ skipping 2449 matching lines @@
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 }  // namespace internal
 }  // namespace v8