WIP [esnext] implement async iteration proposal

src/runtime/runtime-generator.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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/factory.h"
 #include "src/frames-inl.h"
 #include "src/objects-inl.h"
@@ skipping 51 matching lines @@
 }
 
 RUNTIME_FUNCTION(Runtime_GeneratorGetInputOrDebugPos) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
 
   return generator->input_or_debug_pos();
 }
 
+RUNTIME_FUNCTION(Runtime_GeneratorGetAwaitInput) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
+
+  return generator->await_input();
+}
+
+RUNTIME_FUNCTION(Runtime_GeneratorSaveInputForAwait) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
+
+  // Generator must be executing
+  DCHECK_EQ(generator->continuation(), JSGeneratorObject::kGeneratorExecuting);
+
+  generator->set_await_input(generator->input_or_debug_pos());
+
+  return isolate->heap()->undefined_value();
+}
+
 RUNTIME_FUNCTION(Runtime_GeneratorGetResumeMode) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
 
   return Smi::FromInt(generator->resume_mode());
 }
 
 RUNTIME_FUNCTION(Runtime_GeneratorGetContinuation) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
 
   return Smi::FromInt(generator->continuation());
 }
 
 RUNTIME_FUNCTION(Runtime_GeneratorGetSourcePosition) {
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   CONVERT_ARG_HANDLE_CHECKED(JSGeneratorObject, generator, 0);
 
   if (!generator->is_suspended()) return isolate->heap()->undefined_value();
   return Smi::FromInt(generator->source_position());
 }
 
 }  // namespace internal
 }  // namespace v8