Made simple instance-of checks fast for unoptimized code.

runtime/lib/object.cc

Index: runtime/lib/object.cc
diff --git a/runtime/lib/object.cc b/runtime/lib/object.cc
index 723bf69eced37e87d2b9851d8aad625324c9ac28..e1b7a71c8eb53bfc7acd3a25760dcfbd6a5940a6 100644
--- a/runtime/lib/object.cc
+++ b/runtime/lib/object.cc
@@ -166,6 +166,37 @@ DEFINE_NATIVE_ENTRY(Object_instanceOf, 4) {
   return Bool::Get(negate.value() ? !is_instance_of : is_instance_of).raw();
 }
 
+DEFINE_NATIVE_ENTRY(Object_simpleInstanceOf, 2) {
+  // This native is only called when the right hand side passes
+  // simpleInstanceOfType and it is a non-negative test.

[regis, 2016/07/14 01:41:45]

It would be interesting to do it for the negative case as well and see if it
helps dart2js.
I suppose a 'negate' extra argument would not work, but you would need a
separate call (e.g. Object_simpleNotInstanceOf).

[bakster, 2016/07/14 17:59:41]

Yes, that is an easy change.
However, in the benchmarks I measured, it is hardly used.

+  const Instance& instance =
+      Instance::CheckedHandle(zone, arguments->NativeArgAt(0));
+  const AbstractType& type =
+      AbstractType::CheckedHandle(zone, arguments->NativeArgAt(1));
+  const TypeArguments& instantiator_type_arguments =
+      TypeArguments::Handle(TypeArguments::null());
+  ASSERT(type.IsFinalized());
+  ASSERT(!type.IsMalformed());
+  ASSERT(!type.IsMalbounded());
+  Error& bound_error = Error::Handle(zone, Error::null());
+  const bool is_instance_of = instance.IsInstanceOf(type,
+                                                    instantiator_type_arguments,
+                                                    &bound_error);
+  if (!is_instance_of && !bound_error.IsNull()) {
+    // Throw a dynamic type error only if the instanceof test fails.
+    DartFrameIterator iterator;
+    StackFrame* caller_frame = iterator.NextFrame();
+    ASSERT(caller_frame != NULL);
+    const TokenPosition location = caller_frame->GetTokenPos();
+    String& bound_error_message = String::Handle(
+        zone, String::New(bound_error.ToErrorCString()));
+    Exceptions::CreateAndThrowTypeError(
+        location, AbstractType::Handle(zone), AbstractType::Handle(zone),
+        Symbols::Empty(), bound_error_message);
+    UNREACHABLE();
+  }
+  return Bool::Get(is_instance_of).raw();
+}
 
 DEFINE_NATIVE_ENTRY(Object_instanceOfNum, 2) {
   const Instance& instance =