[es6] Perform the IsConstructor test in GetSuperConstructor.

src/code-stub-assembler.cc

 // Copyright 2016 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/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 #include "src/ic/handler-configuration.h"
 #include "src/ic/stub-cache.h"
@@ skipping 7798 matching lines @@
     result_var.Bind(HeapConstant(isolate()->factory()->type##_string())); \
     Goto(&return_result);                                                 \
   }
   SIMD128_TYPES(SIMD128_BIND_RETURN)
 #undef SIMD128_BIND_RETURN
 
   Bind(&return_result);
   return result_var.value();
 }
 
+compiler::Node* CodeStubAssembler::GetSuperConstructor(
+    compiler::Node* active_function, compiler::Node* context) {
+  Node* map = LoadMap(active_function);

[caitp, 2016/11/21 13:52:53]

I would add a CSA_ASSERT() to ensure that this is a HeapObject

[Benedikt Meurer, 2016/11/23 04:51:00]

Yes, please.

[Henrique Ferreiro, 2016/12/01 12:22:22]

Similar code checks for a Smi and a HeapNumber, is the latter neccessary? I
would assume a heap number also has a map.

+  Node* prototype = LoadMapPrototype(map);
+  Node* bit_field = LoadMapBitField(map);
+
+  Label not_constructor(this);

[caitp, 2016/11/21 13:52:53]

You want this label to be deferred.

[Henrique Ferreiro, 2016/12/01 12:22:22]

Would you mind explaining what is that for?

+  GotoUnless(
+      Word32Equal(Word32And(bit_field, Int32Constant(1 << Map::kIsConstructor)),
+                  Int32Constant(1 << Map::kIsConstructor)),
+      &not_constructor);
+  return prototype;
+
+  Bind(&not_constructor);
+  {
+    CallRuntime(Runtime::kThrowConstructedNonConstructable, active_function);
+    return UndefinedConstant();  // Never reached.
+  }
+}
+
 compiler::Node* CodeStubAssembler::InstanceOf(compiler::Node* object,
                                               compiler::Node* callable,
                                               compiler::Node* context) {
   Label return_runtime(this, Label::kDeferred), end(this);
   Variable result(this, MachineRepresentation::kTagged);
 
   // Check if no one installed @@hasInstance somewhere.
   GotoUnless(
       WordEqual(LoadObjectField(LoadRoot(Heap::kHasInstanceProtectorRootIndex),
                                 PropertyCell::kValueOffset),
@@ skipping 239 matching lines @@
   Node* buffer_bit_field = LoadObjectField(
       buffer, JSArrayBuffer::kBitFieldOffset, MachineType::Uint32());
   Node* was_neutered_mask = Int32Constant(JSArrayBuffer::WasNeutered::kMask);
 
   return Word32NotEqual(Word32And(buffer_bit_field, was_neutered_mask),
                         Int32Constant(0));
 }
 
 }  // namespace internal
 }  // namespace v8