WIP [esnext] implement async iteration proposal

src/x64/macro-assembler-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 3924 matching lines @@
     Check(not_equal, kOperandIsASmiAndNotABoundFunction);
     Push(object);
     CmpObjectType(object, JS_BOUND_FUNCTION_TYPE, object);
     Pop(object);
     Check(equal, kOperandIsNotABoundFunction);
   }
 }
 
 void MacroAssembler::AssertGeneratorObject(Register object) {
   if (emit_debug_code()) {
+    Label ok;
     testb(object, Immediate(kSmiTagMask));
     Check(not_equal, kOperandIsASmiAndNotAGeneratorObject);
+
     Push(object);
     CmpObjectType(object, JS_GENERATOR_OBJECT_TYPE, object);
     Pop(object);
+    j(equal, &ok, Label::kNear);
+
+    Push(object);
+    CmpObjectType(object, JS_ASYNC_GENERATOR_OBJECT_TYPE, object);
+    Pop(object);
     Check(equal, kOperandIsNotAGeneratorObject);
+
+    bind(&ok);
   }
 }
 
+void MacroAssembler::AssertAsyncGeneratorObject(Register object) {
+  if (emit_debug_code()) {
+    testb(object, Immediate(kSmiTagMask));
+    Check(not_equal, kOperandIsASmiAndNotAnAsyncGeneratorObject);
+    Push(object);
+    CmpObjectType(object, JS_ASYNC_GENERATOR_OBJECT_TYPE, object);
+    Pop(object);
+    Check(equal, kOperandIsNotAnAsyncGeneratorObject);
+  }
+}
+
 void MacroAssembler::AssertReceiver(Register object) {
   if (emit_debug_code()) {
     testb(object, Immediate(kSmiTagMask));
     Check(not_equal, kOperandIsASmiAndNotAReceiver);
     Push(object);
     STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
     CmpObjectType(object, FIRST_JS_RECEIVER_TYPE, object);
     Pop(object);
     Check(above_equal, kOperandIsNotAReceiver);
   }
@@ skipping 1335 matching lines @@
   movl(rax, dividend);
   shrl(rax, Immediate(31));
   addl(rdx, rax);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64