[promises] Remove one runtime call to create_resolving_functions

src/promise-utils.cc

+// Copyright 2016 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/promise-utils.h"
+
+#include "src/factory.h"
+#include "src/isolate.h"
+#include "src/objects-inl.h"
+
+namespace v8 {
+namespace internal {
+
+enum PromiseResolvingFunctionContextSlot {
+  kAlreadyVisitedSlot = Context::MIN_CONTEXT_SLOTS,
+  kPromiseSlot,
+  kDebugEventSlot,
+  kPromiseContextLength,
+};
+
+Handle<JSObject> PromiseUtils::GetPromise(Isolate* isolate,

[adamk, 2016/11/10 18:10:54]

You could make these just return raw pointers, leave the Isolate argument out,
and let your callers deal with creating the handle. Thoughts?

[gsathya, 2016/11/11 02:34:37]

Done.

+                                          Handle<Context> context) {
+  return handle(JSObject::cast(context->get(PromiseUtils::kPromiseSlot)),

[adamk, 2016/11/10 18:10:54]

Hmm, looks like these need updating to refer to the slot enum in this file?

[gsathya, 2016/11/11 02:34:37]

Done.

+                isolate);
+}
+
+Handle<Object> PromiseUtils::GetDebugEvent(Isolate* isolate,
+                                           Handle<Context> context) {
+  return handle(context->get(PromiseUtils::kDebugEventSlot), isolate);
+}
+
+Handle<Smi> PromiseUtils::GetAlreadyVisited(Isolate* isolate,
+                                            Handle<Context> context) {
+  return handle(Smi::cast(context->get(PromiseUtils::kAlreadyVisitedSlot)),
+                isolate);
+}
+
+void PromiseUtils::SetAlreadyVisitedToTrue(Handle<Context> context) {
+  context->set(PromiseUtils::kAlreadyVisitedSlot, Smi::FromInt(1));
+}
+
+void PromiseUtils::CreateResolvingFunctions(Isolate* isolate,
+                                            Handle<JSObject> promise,
+                                            Handle<Object> debug_event,

[adamk, 2016/11/10 18:10:54]

Can you add the same DCHECK here for debug_event being true or false?

In a followup you could save a slot in the context by storing the AlreadyVisited
bit in the same slot as the IsDebugEvent bit.

[gsathya, 2016/11/11 02:34:36]

It seems redundant to have the same DCHECK in both places. I've left it here at
it.
Not sure I follow. What about the case when IsDebugEvent is true and
AlreadyVisited is false? 

+                                            Handle<JSFunction>* resolve,
+                                            Handle<JSFunction>* reject) {
+  Handle<Context> context =
+      isolate->factory()->NewPromiseResolvingFunctionContext(
+          kPromiseContextLength);
+  context->set_native_context(*isolate->native_context());
+  context->set(kAlreadyVisitedSlot, Smi::kZero);
+  context->set(kPromiseSlot, *promise);
+  context->set(kDebugEventSlot, *debug_event);
+
+  Handle<SharedFunctionInfo> resolve_shared_fun(
+      isolate->native_context()->promise_resolve_shared_fun(), isolate);
+  Handle<JSFunction> resolve_fun =
+      isolate->factory()->NewFunctionFromSharedFunctionInfo(
+          isolate->sloppy_function_without_prototype_map(), resolve_shared_fun,
+          isolate->native_context(), TENURED);
+
+  Handle<SharedFunctionInfo> reject_shared_fun(
+      isolate->native_context()->promise_reject_shared_fun(), isolate);
+  Handle<JSFunction> reject_fun =
+      isolate->factory()->NewFunctionFromSharedFunctionInfo(
+          isolate->sloppy_function_without_prototype_map(), reject_shared_fun,
+          isolate->native_context(), TENURED);
+
+  resolve_fun->set_context(*context);
+  reject_fun->set_context(*context);
+
+  *resolve = resolve_fun;
+  *reject = reject_fun;
+}
+
+}  // namespace internal
+}  // namespace v8