Added descriptor lookup cache to eliminate some search overhead....

src/objects.cc

 // Copyright 2006-2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1547 matching lines @@
         return FixedArray::cast(element)->get(kSetterIndex);
       }
     }
   }
   return Heap::undefined_value();
 }
 
 
 void JSObject::LookupInDescriptor(String* name, LookupResult* result) {
   DescriptorArray* descriptors = map()->instance_descriptors();
-  int number = descriptors->Search(name);
+  int number = DescriptorLookupCache::Lookup(descriptors, name);
+  if (number == DescriptorLookupCache::kAbsent) {
+    number = descriptors->Search(name);
+    DescriptorLookupCache::Update(descriptors, name, number);
+  }
   if (number != DescriptorArray::kNotFound) {
     result->DescriptorResult(this, descriptors->GetDetails(number), number);
   } else {
     result->NotFound();
   }
 }
 
 
 void JSObject::LocalLookupRealNamedProperty(String* name,
                                             LookupResult* result) {
@@ skipping 5901 matching lines @@
   // No break point.
   if (break_point_objects()->IsUndefined()) return 0;
   // Single beak point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 } }  // namespace v8::internal