[es6] Perform the IsConstructor test in GetSuperConstructor.

src/code-stub-assembler.cc

Index: src/code-stub-assembler.cc
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index c93af865c3418a16a36f2b24ee5f8d55fb7114ae..c12a1e1a3252322e6dcdb84b7624055976894d23 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -2880,6 +2880,13 @@ Node* CodeStubAssembler::IsCallableMap(Node* map) {
       Int32Constant(0));
 }
 
+Node* CodeStubAssembler::IsConstructorMap(Node* map) {
+  CSA_ASSERT(this, IsMap(map));
+  return Word32NotEqual(
+      Word32And(LoadMapBitField(map), Int32Constant(1 << Map::kIsConstructor)),
+      Int32Constant(0));
+}
+
 Node* CodeStubAssembler::IsSpecialReceiverInstanceType(Node* instance_type) {
   STATIC_ASSERT(JS_GLOBAL_OBJECT_TYPE <= LAST_SPECIAL_RECEIVER_TYPE);
   return Int32LessThanOrEqual(instance_type,
@@ -2960,6 +2967,10 @@ Node* CodeStubAssembler::IsUnseededNumberDictionary(Node* object) {
                    LoadRoot(Heap::kUnseededNumberDictionaryMapRootIndex));
 }
 
+Node* CodeStubAssembler::IsJSFunction(Node* object) {
+  return HasInstanceType(object, JS_FUNCTION_TYPE);
+}
+
 Node* CodeStubAssembler::StringCharCodeAt(Node* string, Node* index) {
   CSA_ASSERT(this, IsString(string));
   // Translate the {index} into a Word.
@@ -7818,6 +7829,33 @@ Node* CodeStubAssembler::Typeof(Node* value, Node* context) {
   return result_var.value();
 }
 
+Node* CodeStubAssembler::GetSuperConstructor(Node* active_function,
+                                             Node* context) {
+  CSA_ASSERT(this, IsJSFunction(active_function));
+
+  Label is_not_constructor(this, Label::kDeferred), out(this);
+  Variable result(this, MachineRepresentation::kTagged);
+
+  Node* map = LoadMap(active_function);
+  Node* prototype = LoadMapPrototype(map);
+  Node* prototype_map = LoadMap(prototype);
+  GotoUnless(IsConstructorMap(prototype_map), &is_not_constructor);
+
+  result.Bind(prototype);
+  Goto(&out);
+
+  Bind(&is_not_constructor);
+  {
+    CallRuntime(Runtime::kThrowNotSuperConstructor, context, prototype,
+                active_function);
+    result.Bind(UndefinedConstant());  // Never reached.

[Benedikt Meurer, 2016/12/12 18:18:19]

Nit: you could just bind the result of the runtime call, that'd generate shorter
code, i.e. save the ldr rax, [roots+UndefinedOffset]. But it's not really
important.

+    Goto(&out);
+  }
+
+  Bind(&out);
+  return result.value();
+}
+
 Node* CodeStubAssembler::InstanceOf(Node* object, Node* callable,
                                     Node* context) {
   Label return_runtime(this, Label::kDeferred), end(this);