Turn Array.isArray into a Turbofan stub

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 3119f942eef3b110213ef6fbc4fa69bb9ca827ae..5b3def4ff4d2737d5d6b57d224b8155362e5fb2e 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -351,6 +351,39 @@ BUILTIN(Illegal) {
 
 BUILTIN(EmptyFunction) { return isolate->heap()->undefined_value(); }
 
+void Builtins::Generate_ArrayIsArray(CodeStubAssembler* assembler) {
+  typedef compiler::Node Node;
+  typedef CodeStubAssembler::Label Label;
+
+  Node* object = assembler->Parameter(1);
+  Node* context = assembler->Parameter(4);
+
+  Label call_runtime(assembler), return_true(assembler),
+      return_false(assembler);
+
+  assembler->GotoIf(assembler->WordIsSmi(object), &return_false);
+  Node* instance_type = assembler->LoadInstanceType(object);
+
+  assembler->GotoIf(assembler->Word32Equal(
+                        instance_type, assembler->Int32Constant(JS_ARRAY_TYPE)),
+                    &return_true);
+
+  // TODO(verwaest): Handle proxies in-place.
+  assembler->Branch(assembler->Word32Equal(
+                        instance_type, assembler->Int32Constant(JS_PROXY_TYPE)),
+                    &call_runtime, &return_false);
+
+  assembler->Bind(&return_true);
+  assembler->Return(assembler->BooleanConstant(true));
+
+  assembler->Bind(&return_false);
+  assembler->Return(assembler->BooleanConstant(false));
+
+  assembler->Bind(&call_runtime);
+  assembler->Return(
+      assembler->CallRuntime(Runtime::kArrayIsArray, context, object));
+}
+
 void Builtins::Generate_ObjectHasOwnProperty(CodeStubAssembler* assembler) {
   typedef compiler::Node Node;
   typedef CodeStubAssembler::Label Label;
@@ -1609,16 +1642,6 @@ BUILTIN(ArrayConcat) {
 }
 
 
-// ES6 22.1.2.2 Array.isArray
-BUILTIN(ArrayIsArray) {
-  HandleScope scope(isolate);
-  DCHECK_EQ(2, args.length());
-  Handle<Object> object = args.at<Object>(1);
-  Maybe<bool> result = Object::IsArray(object);
-  MAYBE_RETURN(result, isolate->heap()->exception());
-  return *isolate->factory()->ToBoolean(result.FromJust());
-}
-
 namespace {
 
 MUST_USE_RESULT Maybe<bool> FastAssign(Handle<JSReceiver> to,