Speed up the Dart_IsBlah functions by checking the class index. This

vm/dart_api_impl.h

Index: vm/dart_api_impl.h
===================================================================
--- vm/dart_api_impl.h	(revision 7467)
+++ vm/dart_api_impl.h	(working copy)
@@ -123,6 +123,14 @@
     return Smi::ValueFromRaw(value);
   }
 
+  static intptr_t ClassIndex(Dart_Handle handle) {

[Ivan Posva, 2012/05/09 23:28:16]

There is an inconsistency naming this. In RawObject you call the value a
ClassTag, here it is a ClassIndex. My initial reaction was to use ClassIndex,
but on further reflection I do like distinguishing the difference of accessing
the tag of an Object (here) from getting the index of a Class.

[turnidge, 2012/05/10 17:49:38]

I thought about this some more and decided to go with ClassIndex across the
board.  It just seems simpler.

+    RawObject* raw = *(reinterpret_cast<RawObject**>(handle));
+    if (!raw->IsHeapObject()) {
+      return kSmi;
+    }
+    return raw->GetClassTag();
+  }
+
   // Generates a handle used to designate an error return.
   static Dart_Handle NewError(const char* format, ...);