WIP [esnext] implement async iteration proposal

src/interpreter/interpreter.cc

 // Copyright 2015 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/interpreter/interpreter.h"
 
 #include <fstream>
 #include <memory>
 
 #include "src/ast/prettyprinter.h"
@@ skipping 3224 matching lines @@
   __ Dispatch();
 
   __ Bind(&if_stepping);
   {
     Node* context = __ GetContext();
     __ CallRuntime(Runtime::kDebugRecordGenerator, context, generator);
     __ Goto(&ok);
   }
 }
 
+// AwaitGenerator <generator>
+//
+// Like SuspendGenerator, exports the register file and stores it into the
+// generator, along with current context, the continuation state. The current
+// bytecode offset is stored in the [await_input] field to prevent clobbering
+// the sent value.
+void Interpreter::DoAwaitGenerator(InterpreterAssembler* assembler) {
+  Node* generator_reg = __ BytecodeOperandReg(0);
+  Node* generator = __ LoadRegister(generator_reg);
+
+  Label if_stepping(assembler, Label::kDeferred), ok(assembler);
+  Node* step_action_address = __ ExternalConstant(
+      ExternalReference::debug_last_step_action_address(isolate_));
+  Node* step_action = __ Load(MachineType::Int8(), step_action_address);
+  STATIC_ASSERT(StepIn > StepNext);
+  STATIC_ASSERT(StepFrame > StepNext);
+  STATIC_ASSERT(LastStepAction == StepFrame);
+  Node* step_next = __ Int32Constant(StepNext);
+  __ Branch(__ Int32LessThanOrEqual(step_next, step_action), &if_stepping, &ok);
+  __ Bind(&ok);
+
+  Node* array =
+      __ LoadObjectField(generator, JSGeneratorObject::kRegisterFileOffset);
+  Node* context = __ GetContext();
+  Node* state = __ GetAccumulator();
+
+  __ ExportRegisterFile(array);
+  __ StoreObjectField(generator, JSGeneratorObject::kContextOffset, context);
+  __ StoreObjectField(generator, JSGeneratorObject::kContinuationOffset, state);
+
+  Node* offset = __ SmiTag(__ BytecodeOffset());
+  __ StoreObjectField(generator, JSAsyncGeneratorObject::kAwaitInputOffset,
+                      offset);
+
+  __ Dispatch();
+
+  __ Bind(&if_stepping);
+  {
+    Node* context = __ GetContext();
+    __ CallRuntime(Runtime::kDebugRecordGenerator, context, generator);
+    __ Goto(&ok);
+  }
+}
+
 // ResumeGenerator <generator>
 //
 // Imports the register file stored in the generator. Also loads the
 // generator's state and stores it in the accumulator, before overwriting it
 // with kGeneratorExecuting.
 void Interpreter::DoResumeGenerator(InterpreterAssembler* assembler) {
   Node* generator_reg = __ BytecodeOperandReg(0);
   Node* generator = __ LoadRegister(generator_reg);
 
   __ ImportRegisterFile(
       __ LoadObjectField(generator, JSGeneratorObject::kRegisterFileOffset));
 
   Node* old_state =
       __ LoadObjectField(generator, JSGeneratorObject::kContinuationOffset);
   Node* new_state = __ Int32Constant(JSGeneratorObject::kGeneratorExecuting);
   __ StoreObjectField(generator, JSGeneratorObject::kContinuationOffset,
       __ SmiTag(new_state));
   __ SetAccumulator(old_state);
 
   __ Dispatch();
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8