WIP [esnext] implement async iteration proposal

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"
 
 namespace v8 {
 namespace internal {
@@ skipping 8156 matching lines @@
                        Heap::kEmptyFixedArrayRootIndex);
   StoreObjectFieldNoWriteBarrier(iterator,
                                  JSArrayIterator::kIteratedObjectOffset, array);
   StoreObjectFieldNoWriteBarrier(iterator, JSArrayIterator::kNextIndexOffset,
                                  SmiConstant(Smi::FromInt(0)));
   StoreObjectFieldNoWriteBarrier(
       iterator, JSArrayIterator::kIteratedObjectMapOffset, array_map);
   return iterator;
 }
 
+Node* CodeStubAssembler::AllocateJSIteratorResult(Node* context, Node* value,
+                                                  Node* done) {
+  Node* const iter_result = Allocate(JSIteratorResult::kSize);
+  Node* const map = LoadContextElement(LoadNativeContext(context),
+                                       Context::ITERATOR_RESULT_MAP_INDEX);
+  StoreMapNoWriteBarrier(iter_result, map);
+  StoreObjectFieldRoot(iter_result, JSIteratorResult::kPropertiesOffset,
+                       Heap::kEmptyFixedArrayRootIndex);
+  StoreObjectFieldRoot(iter_result, JSIteratorResult::kElementsOffset,
+                       Heap::kEmptyFixedArrayRootIndex);
+  StoreObjectFieldNoWriteBarrier(iter_result, JSIteratorResult::kValueOffset,
+                                 value);
+  StoreObjectFieldNoWriteBarrier(iter_result, JSIteratorResult::kDoneOffset,
+                                 done);
+  return iter_result;
+}
+
 Node* CodeStubAssembler::IsDetachedBuffer(Node* buffer) {
   CSA_ASSERT(this, HasInstanceType(buffer, JS_ARRAY_BUFFER_TYPE));
 
   Node* buffer_bit_field = LoadObjectField(
       buffer, JSArrayBuffer::kBitFieldOffset, MachineType::Uint32());
   return IsSetWord32<JSArrayBuffer::WasNeutered>(buffer_bit_field);
 }
 
 CodeStubArguments::CodeStubArguments(CodeStubAssembler* assembler, Node* argc)
     : assembler_(assembler),
@@ skipping 148 matching lines @@
   StoreObjectFieldNoWriteBarrier(result,
                                  PromiseReactionJobInfo::kDebugNameOffset,
                                  SmiConstant(kDebugNotActive));
   StoreObjectFieldNoWriteBarrier(result, PromiseReactionJobInfo::kContextOffset,
                                  context);
   return result;
 }
 
 }  // namespace internal
 }  // namespace v8