[esnext] prototype runtime implementation for async functions

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index d054916db0a700e330ea3aac6abf859d0ec4226a..1c1b79d6b757a56197b4f5c73d1b7987721173e2 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -2326,9 +2326,12 @@ void Builtins::Generate_MathTrunc(compiler::CodeStubAssembler* assembler) {
 
 namespace {
 
+enum class ResumeType { Generator, Async };
+
 void Generate_GeneratorPrototypeResume(
     compiler::CodeStubAssembler* assembler,
-    JSGeneratorObject::ResumeMode resume_mode, char const* const method_name) {
+    JSGeneratorObject::ResumeMode resume_mode, char const* const method_name,
+    ResumeType type) {
   typedef compiler::CodeStubAssembler::Label Label;
   typedef compiler::Node Node;
 
@@ -2339,22 +2342,27 @@ void Generate_GeneratorPrototypeResume(
 
   // Check if the {receiver} is actually a JSGeneratorObject.
   Label if_receiverisincompatible(assembler, Label::kDeferred);
-  assembler->GotoIf(assembler->WordIsSmi(receiver), &if_receiverisincompatible);
-  Node* receiver_instance_type = assembler->LoadInstanceType(receiver);
-  assembler->GotoUnless(assembler->Word32Equal(
-                            receiver_instance_type,
-                            assembler->Int32Constant(JS_GENERATOR_OBJECT_TYPE)),
-                        &if_receiverisincompatible);
+  if (type == ResumeType::Generator || FLAG_debug_code) {
+    assembler->GotoIf(assembler->WordIsSmi(receiver),
+                      &if_receiverisincompatible);
+    Node* receiver_instance_type = assembler->LoadInstanceType(receiver);
+    assembler->GotoUnless(assembler->Word32Equal(receiver_instance_type,
+                                                 assembler->Int32Constant(
+                                                     JS_GENERATOR_OBJECT_TYPE)),
+                          &if_receiverisincompatible);
+  }
 
   // Check if the {receiver} is running or already closed.
-  Node* receiver_continuation = assembler->LoadObjectField(
-      receiver, JSGeneratorObject::kContinuationOffset);
   Label if_receiverisclosed(assembler, Label::kDeferred),
       if_receiverisrunning(assembler, Label::kDeferred);
-  assembler->GotoIf(assembler->SmiEqual(receiver_continuation, zero),
-                    &if_receiverisclosed);
-  assembler->GotoIf(assembler->SmiLessThan(receiver_continuation, zero),
-                    &if_receiverisrunning);
+  if (type == ResumeType::Generator || FLAG_debug_code) {
+    Node* receiver_continuation = assembler->LoadObjectField(
+        receiver, JSGeneratorObject::kContinuationOffset);
+    assembler->GotoIf(assembler->SmiEqual(receiver_continuation, zero),
+                      &if_receiverisclosed);
+    assembler->GotoIf(assembler->SmiLessThan(receiver_continuation, zero),
+                      &if_receiverisrunning);
+  }
 
   // Resume the {receiver} using our trampoline.
   Node* result = assembler->CallStub(
@@ -2363,7 +2371,7 @@ void Generate_GeneratorPrototypeResume(
   assembler->Return(result);
 
   assembler->Bind(&if_receiverisincompatible);
-  {
+  if (type == ResumeType::Generator || FLAG_debug_code) {
     // The {receiver} is not a valid JSGeneratorObject.
     Node* result = assembler->CallRuntime(
         Runtime::kThrowIncompatibleMethodReceiver, context,
@@ -2373,8 +2381,8 @@ void Generate_GeneratorPrototypeResume(
     assembler->Return(result);  // Never reached.
   }
 
-  assembler->Bind(&if_receiverisclosed);
-  {
+  if (type == ResumeType::Generator || FLAG_debug_code) {
+    assembler->Bind(&if_receiverisclosed);
     // The {receiver} is closed already.
     Node* result = nullptr;
     switch (resume_mode) {
@@ -2395,8 +2403,8 @@ void Generate_GeneratorPrototypeResume(
     assembler->Return(result);
   }
 
-  assembler->Bind(&if_receiverisrunning);
-  {
+  if (type == ResumeType::Generator || FLAG_debug_code) {
+    assembler->Bind(&if_receiverisrunning);
     Node* result =
         assembler->CallRuntime(Runtime::kThrowGeneratorRunning, context);
     assembler->Return(result);  // Never reached.
@@ -2409,21 +2417,36 @@ void Generate_GeneratorPrototypeResume(
 void Builtins::Generate_GeneratorPrototypeNext(
     compiler::CodeStubAssembler* assembler) {
   Generate_GeneratorPrototypeResume(assembler, JSGeneratorObject::kNext,
-                                    "[Generator].prototype.next");
+                                    "[Generator].prototype.next",
+                                    ResumeType::Generator);
 }
 
 // ES6 section 25.3.1.3 Generator.prototype.return ( value )
 void Builtins::Generate_GeneratorPrototypeReturn(
     compiler::CodeStubAssembler* assembler) {
   Generate_GeneratorPrototypeResume(assembler, JSGeneratorObject::kReturn,
-                                    "[Generator].prototype.return");
+                                    "[Generator].prototype.return",
+                                    ResumeType::Generator);
 }
 
 // ES6 section 25.3.1.4 Generator.prototype.throw ( exception )
 void Builtins::Generate_GeneratorPrototypeThrow(
     compiler::CodeStubAssembler* assembler) {
   Generate_GeneratorPrototypeResume(assembler, JSGeneratorObject::kThrow,
-                                    "[Generator].prototype.throw");
+                                    "[Generator].prototype.throw",
+                                    ResumeType::Generator);
+}
+
+void Builtins::Generate_AsyncFunctionNext(
+    compiler::CodeStubAssembler* assembler) {
+  Generate_GeneratorPrototypeResume(assembler, JSGeneratorObject::kNext,
+                                    "[AsyncFunction].next", ResumeType::Async);
+}
+
+void Builtins::Generate_AsyncFunctionThrow(
+    compiler::CodeStubAssembler* assembler) {
+  Generate_GeneratorPrototypeResume(assembler, JSGeneratorObject::kThrow,
+                                    "[AsyncFunction].throw", ResumeType::Async);
 }
 
 // -----------------------------------------------------------------------------