[async-await] Move remaining async-await code to TF

src/builtins/builtins-async-function.cc

 // Copyright 2017 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/builtins/builtins-promise.h"
+#include "src/builtins/builtins-async.h"
 #include "src/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 #include "src/code-stub-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 typedef compiler::Node Node;
 typedef CodeStubAssembler::ParameterMode ParameterMode;
 typedef compiler::CodeAssemblerState CodeAssemblerState;
 
-class AsyncFunctionBuiltinsAssembler : public PromiseBuiltinsAssembler {
+class AsyncFunctionBuiltinsAssembler : public AsyncBuiltinsAssembler {
  public:
   explicit AsyncFunctionBuiltinsAssembler(CodeAssemblerState* state)
-      : PromiseBuiltinsAssembler(state) {}
+      : AsyncBuiltinsAssembler(state) {}
+
+ protected:
+  void AsyncFunctionAwait(Node* const context, Node* const generator,
+                          Node* const awaited, Node* const outer_promise,
+                          const bool is_predicted_as_caught);
+
+  void AsyncFunctionAwaitResumeClosure(
+      Node* const context, Node* const sent_value,
+      JSGeneratorObject::ResumeMode resume_mode);
 };
 
+namespace {
+
+// Describe fields of Context associated with AsyncFunctionAwait resume
+// closures.
+// TODO(jgruber): Refactor to reuse code for upcoming async-generators.
+class AwaitContext {
+ public:
+  enum Fields { kGeneratorSlot = Context::MIN_CONTEXT_SLOTS, kLength };
+};
+
+}  // anonymous namespace
+
+void AsyncFunctionBuiltinsAssembler::AsyncFunctionAwaitResumeClosure(
+    Node* context, Node* sent_value,
+    JSGeneratorObject::ResumeMode resume_mode) {
+  DCHECK(resume_mode == JSGeneratorObject::kNext ||
+         resume_mode == JSGeneratorObject::kThrow);
+
+  Node* const generator =
+      LoadContextElement(context, AwaitContext::kGeneratorSlot);
+  CSA_SLOW_ASSERT(this, HasInstanceType(generator, JS_GENERATOR_OBJECT_TYPE));
+
+  // Inline version of GeneratorPrototypeNext / GeneratorPrototypeReturn with
+  // unnecessary runtime checks removed.
+  // TODO(jgruber): Refactor to reuse code from builtins-generator.cc.
+
+  // Ensure that the generator is neither closed nor running.
+  CSA_SLOW_ASSERT(
+      this,
+      SmiGreaterThan(
+          LoadObjectField(generator, JSGeneratorObject::kContinuationOffset),
+          SmiConstant(JSGeneratorObject::kGeneratorClosed)));
+
+  // Resume the {receiver} using our trampoline.
+  Callable callable = CodeFactory::ResumeGenerator(isolate());
+  CallStub(callable, context, sent_value, generator, SmiConstant(resume_mode));

[jgruber, 2017/01/19 16:12:00]

GeneratorPrototype{Next,Return} basically boils down to this call for the
async-await case.

+
+  // The resulting Promise is a throwaway, so it doesn't matter what it
+  // resolves to. What is important is that we don't end up keeping the
+  // whole chain of intermediate Promises alive by returning the return value
+  // of ResumeGenerator, as that would create a memory leak.
+}
+
+TF_BUILTIN(AsyncFunctionAwaitRejectClosure, AsyncFunctionBuiltinsAssembler) {
+  CSA_ASSERT_JS_ARGC_EQ(this, 1);
+  Node* const sentError = Parameter(1);
+  Node* const context = Parameter(4);
+
+  AsyncFunctionAwaitResumeClosure(context, sentError,
+                                  JSGeneratorObject::kThrow);
+  Return(UndefinedConstant());
+}
+
+TF_BUILTIN(AsyncFunctionAwaitResolveClosure, AsyncFunctionBuiltinsAssembler) {
+  CSA_ASSERT_JS_ARGC_EQ(this, 1);
+  Node* const sentValue = Parameter(1);
+  Node* const context = Parameter(4);
+
+  AsyncFunctionAwaitResumeClosure(context, sentValue, JSGeneratorObject::kNext);
+  Return(UndefinedConstant());
+}
+
+// ES#abstract-ops-async-function-await
+// AsyncFunctionAwait ( value )
+// Shared logic for the core of await. The parser desugars
+//   await awaited
+// into
+//   yield AsyncFunctionAwait{Caught,Uncaught}(.generator, awaited, .promise)
+// The 'awaited' parameter is the value; the generator stands in
+// for the asyncContext, and .promise is the larger promise under
+// construction by the enclosing async function.
+void AsyncFunctionBuiltinsAssembler::AsyncFunctionAwait(
+    Node* const context, Node* const generator, Node* const awaited,
+    Node* const outer_promise, const bool is_predicted_as_caught) {
+  CSA_SLOW_ASSERT(this, HasInstanceType(generator, JS_GENERATOR_OBJECT_TYPE));
+  CSA_SLOW_ASSERT(this, HasInstanceType(outer_promise, JS_PROMISE_TYPE));
+
+  NodeGenerator1 create_closure_context = [&](Node* native_context) -> Node* {
+    Node* const context =
+        CreatePromiseContext(native_context, AwaitContext::kLength);
+    StoreContextElementNoWriteBarrier(context, AwaitContext::kGeneratorSlot,
+                                      generator);
+    return context;
+  };
+
+  // TODO(jgruber): AsyncBuiltinsAssembler::Await currently does not reuse
+  // the awaited promise if it is already a promise. Reuse is non-spec compliant
+  // but part of our old behavior gives us a couple of percent
+  // performance boost.
+  // TODO(jgruber): Use a faster specialized version of

[jgruber, 2017/01/19 16:12:00]

I think caitp has already done some work on this. Holding off until her changes
land.

+  // InternalPerformPromiseThen.
+
+  Node* const result = Await(
+      context, generator, awaited, outer_promise, create_closure_context,
+      Context::ASYNC_FUNCTION_AWAIT_RESOLVE_SHARED_FUN,
+      Context::ASYNC_FUNCTION_AWAIT_REJECT_SHARED_FUN, is_predicted_as_caught);
+
+  Return(result);
+}
+
+// Called by the parser from the desugaring of 'await' when catch
+// prediction indicates that there is a locally surrounding catch block.
+TF_BUILTIN(AsyncFunctionAwaitCaught, AsyncFunctionBuiltinsAssembler) {
+  CSA_ASSERT_JS_ARGC_EQ(this, 3);
+  Node* const generator = Parameter(1);
+  Node* const awaited = Parameter(2);
+  Node* const outer_promise = Parameter(3);
+  Node* const context = Parameter(6);
+
+  static const bool kIsPredictedAsCaught = true;
+
+  AsyncFunctionAwait(context, generator, awaited, outer_promise,
+                     kIsPredictedAsCaught);
+}
+
+// Called by the parser from the desugaring of 'await' when catch
+// prediction indicates no locally surrounding catch block.
+TF_BUILTIN(AsyncFunctionAwaitUncaught, AsyncFunctionBuiltinsAssembler) {
+  CSA_ASSERT_JS_ARGC_EQ(this, 3);
+  Node* const generator = Parameter(1);
+  Node* const awaited = Parameter(2);
+  Node* const outer_promise = Parameter(3);
+  Node* const context = Parameter(6);
+
+  static const bool kIsPredictedAsCaught = false;
+
+  AsyncFunctionAwait(context, generator, awaited, outer_promise,
+                     kIsPredictedAsCaught);
+}
+
 TF_BUILTIN(AsyncFunctionPromiseCreate, AsyncFunctionBuiltinsAssembler) {
   CSA_ASSERT_JS_ARGC_EQ(this, 0);
   Node* const context = Parameter(3);
 
   Node* const promise = AllocateAndInitJSPromise(context);
 
   Label if_is_debug_active(this, Label::kDeferred);
   GotoIf(IsDebugActive(), &if_is_debug_active);
 
   // Early exit if debug is not active.
@@ skipping 26 matching lines @@
   {
     // Pop the Promise under construction in an async function on
     // from catch prediction stack.
     CallRuntime(Runtime::kDebugPopPromise, context);
     Return(promise);
   }
 }
 
 }  // namespace internal
 }  // namespace v8