[builtins] Don't adapt arguments for Object.create.

Object.create is most often called with a single parameter, the
prototype, and the properties are usually omitted. So optimizing
for the common case, we remove the argument adaption.

R=jgruber@chromium.org
BUG=v8:5989

Review-Url: https://codereview.chromium.org/2953913002
Cr-Commit-Position: refs/heads/master@{#46153}

src/bootstrapper.cc

@@ -1271,7 +1271,7 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
 
     Handle<JSFunction> object_create =
         SimpleInstallFunction(object_function, factory->create_string(),
-                              Builtins::kObjectCreate, 2, true);
+                              Builtins::kObjectCreate, 2, false);
     native_context()->set_object_create(*object_create);
 
     Handle<JSFunction> object_define_properties = SimpleInstallFunction(

src/builtins/builtins-definitions.h

@@ -703,7 +703,7 @@ namespace internal {
   /* Object */                                                                 \
   CPP(ObjectAssign)                                                            \
   /* ES #sec-object.create */                                                  \
-  TFJ(ObjectCreate, 2, kPrototype, kProperties)                                \
+  TFJ(ObjectCreate, SharedFunctionInfo::kDontAdaptArgumentsSentinel)           \
   CPP(ObjectDefineGetter)                                                      \
   CPP(ObjectDefineProperties)                                                  \
   CPP(ObjectDefineProperty)                                                    \

src/builtins/builtins-object-gen.cc

@@ -410,9 +410,16 @@ TF_BUILTIN(ObjectPrototypeValueOf, CodeStubAssembler) {
 
 // ES #sec-object.create
 TF_BUILTIN(ObjectCreate, ObjectBuiltinsAssembler) {
-  Node* prototype = Parameter(Descriptor::kPrototype);
-  Node* properties = Parameter(Descriptor::kProperties);
-  Node* context = Parameter(Descriptor::kContext);
+  int const kPrototypeArg = 0;
+  int const kPropertiesArg = 1;
+
+  Node* argc =
+      ChangeInt32ToIntPtr(Parameter(BuiltinDescriptor::kArgumentsCount));
+  CodeStubArguments args(this, argc);
+
+  Node* prototype = args.GetOptionalArgumentValue(kPrototypeArg);
+  Node* properties = args.GetOptionalArgumentValue(kPropertiesArg);
+  Node* context = Parameter(BuiltinDescriptor::kContext);
 
   Label call_runtime(this, Label::kDeferred), prototype_valid(this),
       no_properties(this);
@@ -483,13 +490,15 @@ TF_BUILTIN(ObjectCreate, ObjectBuiltinsAssembler) {
     BIND(&instantiate_map);
     {
       Node* instance = AllocateJSObjectFromMap(map.value(), properties.value());
-      Return(instance);
+      args.PopAndReturn(instance);
     }
   }
 
   BIND(&call_runtime);
   {
-    Return(CallRuntime(Runtime::kObjectCreate, context, prototype, properties));
+    Node* result =
+        CallRuntime(Runtime::kObjectCreate, context, prototype, properties);
+    args.PopAndReturn(result);
   }
 }