Add fast paths for Smi values in the dart embedding api.

vm/dart_api_impl.h

Index: vm/dart_api_impl.h
===================================================================
--- vm/dart_api_impl.h	(revision 6440)
+++ vm/dart_api_impl.h	(working copy)
@@ -111,6 +111,19 @@
   // Gets the handle used to designate successful return.
   static Dart_Handle Success(Isolate* isolate);
 
+  // Returns true if the handle holds a Smi.
+  static bool IsSmi(Dart_Handle handle) {

[cshapiro, 2012/04/11 23:29:09]

Why not call the existing predicate after casing the value to a RawObject?

[turnidge, 2012/04/16 20:07:24]

Done.

+    uword value = *(reinterpret_cast<uword*>(handle));
+    return (value & kSmiTagMask) == kSmiTag;
+  }
+
+  // Returns the value of a Smi.
+  static intptr_t SmiValue(Dart_Handle handle) {
+    intptr_t value = *(reinterpret_cast<intptr_t*>(handle));

[cshapiro, 2012/04/11 23:29:09]

This may be another opportunity to reuse existing infrastructure.

[turnidge, 2012/04/16 20:07:24]

Done.  Had to add friend permission though...

+    ASSERT((value & kSmiTagMask) == kSmiTag);
+    return (value >> kSmiTagShift);
+  }
+
   // Generates a handle used to designate an error return.
   static Dart_Handle NewError(const char* format, ...);