[promises] Move PromiseReactionJob to c++

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 20ff7ff899e317ae3f62f84099117d0165e16677..05b128e17aa3211fc079aec5f66c87f1b93b6c2f 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -24,6 +24,7 @@
 #include "src/crankshaft/hydrogen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
+#include "src/elements.h"
 #include "src/external-reference-table.h"
 #include "src/frames-inl.h"
 #include "src/ic/access-compiler-data.h"
@@ -3008,6 +3009,50 @@ void Isolate::ReportPromiseReject(Handle<JSObject> promise,
       v8::Utils::StackTraceToLocal(stack_trace)));
 }
 
+void Isolate::PromiseReactionJob(Handle<PromiseHandleInfo> promise_handle_info,
+                                 MaybeHandle<Object>* result,
+                                 MaybeHandle<Object>* maybe_exception) {
+  if (debug()->is_active()) {

[adamk, 2016/10/11 23:14:30]

I think you could create a helper class that'd encapsulate this work. You could
put it on the stack, passing |this|, before_debug_event, and after_debug_event,
and it would take care of firing the before_debug_event at construction and the
after_debug_event on destruction.

[gsathya, 2016/10/12 02:00:43]

Done. But it's the same LoC 

+    Handle<Object> before_debug_event(promise_handle_info->before_debug_event(),
+                                      this);
+    if (before_debug_event->IsJSObject()) {
+      debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(before_debug_event));
+    }
+  }
+
+  Handle<Object> value(promise_handle_info->value(), this);
+  Handle<Object> tasks(promise_handle_info->tasks(), this);
+
+  if (tasks->IsJSArray()) {

[adamk, 2016/10/11 23:14:30]

Can you add a comment here about the two possible states tasks might be in?

[gsathya, 2016/10/12 02:00:43]

Done.

+    Handle<JSArray> array = Handle<JSArray>::cast(tasks);
+    DCHECK(array->length()->IsSmi());
+    Handle<FixedArrayBase> elements(array->elements(), this);

[adamk, 2016/10/11 23:14:30]

This is now unused.

[gsathya, 2016/10/12 02:00:44]

Done.

+    int length = Smi::cast(array->length())->value();
+    ElementsAccessor* accessor = array->GetElementsAccessor();
+    for (int i = 0; i < length; i += 2) {

[adamk, 2016/10/11 23:14:30]

Please add a DCHECK that length is even (otherwise this loop is unsafe)

[gsathya, 2016/10/12 02:00:44]

Done.

+      Handle<Object> argv[] = {value, accessor->Get(array, i),

[adamk, 2016/10/11 23:14:30]

Please add the DCHECK for Has(i) and Has(i+1).

[gsathya, 2016/10/12 02:00:44]

Done.

+                               accessor->Get(array, i + 1)};
+      *result = Execution::TryCall(this, promise_handle(),

[adamk, 2016/10/11 23:14:30]

I'd hoist this out of the loop, you could store it in a handle the same place
where you create |value| and |tasks|.

[gsathya, 2016/10/12 02:00:43]

Done.

+                                   factory()->undefined_value(),

[adamk, 2016/10/11 23:14:30]

Same as the above, I'd hoist this out.

[gsathya, 2016/10/12 02:00:43]

Done.

+                                   arraysize(argv), argv, maybe_exception);

[adamk, 2016/10/11 23:14:30]

I'm not sure the same logic about result and maybe_exception holds as it did
before. This is only going to remember the last call.

[gsathya, 2016/10/12 02:00:43]

Done.

+    }
+  } else {
+    Handle<Object> deferred(promise_handle_info->deferred(), this);
+    Handle<Object> argv[] = {value, tasks, deferred};
+    *result =
+        Execution::TryCall(this, promise_handle(), factory()->undefined_value(),
+                           arraysize(argv), argv, maybe_exception);
+  }
+
+  if (debug()->is_active()) {
+    Handle<Object> after_debug_event(promise_handle_info->after_debug_event(),
+                                     this);
+    if (after_debug_event->IsJSObject()) {
+      debug()->OnAsyncTaskEvent(Handle<JSObject>::cast(after_debug_event));
+    }
+  }
+}
+
 void Isolate::PromiseResolveThenableJob(Handle<PromiseContainer> container,
                                         MaybeHandle<Object>* result,
                                         MaybeHandle<Object>* maybe_exception) {
@@ -3044,8 +3089,9 @@ void Isolate::PromiseResolveThenableJob(Handle<PromiseContainer> container,
 }
 
 void Isolate::EnqueueMicrotask(Handle<Object> microtask) {
+  // TODO(gsathya): remove IsJSFunction?

[adamk, 2016/10/11 23:14:30]

You'd have to change the V8 API before you could do that, so I don't think this
TODO belongs here.

[gsathya, 2016/10/12 02:00:43]

Done.

   DCHECK(microtask->IsJSFunction() || microtask->IsCallHandlerInfo() ||
-         microtask->IsPromiseContainer());
+         microtask->IsPromiseContainer() || microtask->IsPromiseHandleInfo());
   Handle<FixedArray> queue(heap()->microtask_queue(), this);
   int num_tasks = pending_microtask_count();
   DCHECK(num_tasks <= queue->length());
@@ -3097,11 +3143,17 @@ void Isolate::RunMicrotasksInternal() {
         callback(data);
       } else {
         SaveContext save(this);
-        Context* context = microtask->IsJSFunction()
-                               ? Handle<JSFunction>::cast(microtask)->context()
-                               : Handle<PromiseContainer>::cast(microtask)
-                                     ->resolve()
-                                     ->context();
+        Context* context;
+        if (microtask->IsJSFunction()) {
+          context = Handle<JSFunction>::cast(microtask)->context();
+        } else if (microtask->IsPromiseContainer()) {
+          context =
+              Handle<PromiseContainer>::cast(microtask)->resolve()->context();
+        } else {
+          context =
+              Handle<PromiseHandleInfo>::cast(microtask)->reaction_context();
+        }
+
         set_context(context->native_context());
         handle_scope_implementer_->EnterMicrotaskContext(
             Handle<Context>(context, this));
@@ -3116,8 +3168,13 @@ void Isolate::RunMicrotasksInternal() {
                                       factory()->undefined_value(), 0, NULL,
                                       &maybe_exception);
         } else {
-          PromiseResolveThenableJob(Handle<PromiseContainer>::cast(microtask),
-                                    &result, &maybe_exception);
+          if (microtask->IsPromiseContainer()) {

[adamk, 2016/10/11 23:14:30]

This should be merged with the else above

[gsathya, 2016/10/12 02:00:43]

Done.

+            PromiseResolveThenableJob(Handle<PromiseContainer>::cast(microtask),
+                                      &result, &maybe_exception);
+          } else {
+            PromiseReactionJob(Handle<PromiseHandleInfo>::cast(microtask),
+                               &result, &maybe_exception);
+          }
         }
 
         handle_scope_implementer_->LeaveMicrotaskContext();