Optimize the message queue for many active ports with few messages.

runtime/vm/dart_entry.cc

Index: runtime/vm/dart_entry.cc
diff --git a/runtime/vm/dart_entry.cc b/runtime/vm/dart_entry.cc
index a82ba9d596c95ffc072cb9dc2ec133c6efa0b7d1..efe422b705e917cdc7124fd630899c7b1ed74d95 100644
--- a/runtime/vm/dart_entry.cc
+++ b/runtime/vm/dart_entry.cc
@@ -371,7 +371,39 @@ RawObject* DartLibraryCalls::Equals(const Instance& left,
 }
 
 
-RawObject* DartLibraryCalls::HandleMessage(Dart_Port dest_port_id,
+RawObject* DartLibraryCalls::LookupReceivePort(Dart_Port port_id) {
+  Isolate* isolate = Isolate::Current();
+  Function& function =
+      Function::Handle(isolate,
+                       isolate->object_store()->lookup_receive_port_function());
+  const int kNumArguments = 1;
+  if (function.IsNull()) {
+    Library& isolate_lib = Library::Handle(Library::IsolateLibrary());
+    ASSERT(!isolate_lib.IsNull());
+    const String& public_class_name =
+        String::Handle(Symbols::New("_ReceivePortImpl"));
+    const String& class_name =
+        String::Handle(isolate_lib.PrivateName(public_class_name));
+    const String& function_name =
+        String::Handle(Symbols::New("_lookupReceivePort"));
+    const Array& kNoArgumentNames = Array::Handle();
+    function = Resolver::ResolveStatic(isolate_lib,
+                                       class_name,
+                                       function_name,
+                                       kNumArguments,
+                                       kNoArgumentNames,
+                                       Resolver::kIsQualified);
+    isolate->object_store()->set_lookup_receive_port_function(function);
+  }
+  const Array& args = Array::Handle(Array::New(kNumArguments));
+  args.SetAt(0, Integer::Handle(Integer::New(port_id)));
+  const Object& result =
+      Object::Handle(DartEntry::InvokeStatic(function, args));
+  return result.raw();
+}
+
+
+RawObject* DartLibraryCalls::HandleMessage(const Object& receive_port,
                                            Dart_Port reply_port_id,
                                            const Instance& message) {
   Isolate* isolate = Isolate::Current();
@@ -398,7 +430,7 @@ RawObject* DartLibraryCalls::HandleMessage(Dart_Port dest_port_id,
     isolate->object_store()->set_handle_message_function(function);
   }
   const Array& args = Array::Handle(isolate, Array::New(kNumArguments));
-  args.SetAt(0, Integer::Handle(isolate, Integer::New(dest_port_id)));
+  args.SetAt(0, receive_port);
   args.SetAt(1, Integer::Handle(isolate, Integer::New(reply_port_id)));
   args.SetAt(2, message);
   const Object& result =