[esnext] prototype runtime implementation for async functions

src/factory.cc

 // Copyright 2014 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/factory.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/conversions.h"
@@ skipping 1642 matching lines @@
     }
   }
 
   array->set_elements(*elms);
   array->set_length(Smi::FromInt(length));
 }
 
 
 Handle<JSGeneratorObject> Factory::NewJSGeneratorObject(
     Handle<JSFunction> function) {
-  DCHECK(function->shared()->is_generator());
+  DCHECK(function->shared()->is_generator() || function->shared()->is_async());
   JSFunction::EnsureHasInitialMap(function);
   Handle<Map> map(function->initial_map());
   DCHECK_EQ(JS_GENERATOR_OBJECT_TYPE, map->instance_type());
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateJSObjectFromMap(*map),
       JSGeneratorObject);
 }
 
 
@@ skipping 385 matching lines @@
   DCHECK(IsValidFunctionKind(kind));
   Handle<SharedFunctionInfo> shared = NewSharedFunctionInfo(
       name, code, IsConstructable(kind, scope_info->language_mode()));
   shared->set_scope_info(*scope_info);
   shared->set_kind(kind);
   shared->set_num_literals(number_of_literals);
   if (IsGeneratorFunction(kind)) {
     shared->set_instance_class_name(isolate()->heap()->Generator_string());
     shared->DisableOptimization(kGenerator);
   }
+  if (IsAsyncFunction(kind)) {
+    shared->DisableOptimization(kGenerator);

[caitp (gmail), 2016/04/26 22:01:30]

Seems to be okay to not do this. Yield disables optimization anyways, but
without an AwaitExpression, these seem to work fine

+  }
   return shared;
 }
 
 
 Handle<JSMessageObject> Factory::NewJSMessageObject(
     MessageTemplate::Template message, Handle<Object> argument,
     int start_position, int end_position, Handle<Object> script,
     Handle<Object> stack_frames) {
   Handle<Map> map = message_object_map();
   Handle<JSMessageObject> message_obj = New<JSMessageObject>(map, NEW_SPACE);
@@ skipping 292 matching lines @@
 }
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return value ? true_value() : false_value();
 }
 
 
 }  // namespace internal
 }  // namespace v8