Faster moving FixedArray elements around.

src/runtime.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 1212 matching lines @@
   Counters::regexp_entry_runtime.Increment();
   Handle<Object> result = RegExpImpl::Exec(regexp,
                                            subject,
                                            index,
                                            last_match_info);
   if (result.is_null()) return Failure::Exception();
   return *result;
 }
 
 
+static Object* Runtime_FinishArrayPrototypeSetup(Arguments args) {
+  HandleScope scope;
+  ASSERT(args.length() == 1);
+  CONVERT_ARG_CHECKED(JSArray, prototype, 0);
+  // This is necessary to enable fast checks for absence of elements
+  // on Array.prototype and below.
+  prototype->set_elements(Heap::empty_fixed_array());
+  return Smi::FromInt(0);
+}
+
+
 static Object* Runtime_MaterializeRegExpLiteral(Arguments args) {
   HandleScope scope;
   ASSERT(args.length() == 4);
   CONVERT_ARG_CHECKED(FixedArray, literals, 0);
   int index = Smi::cast(args[1])->value();
   Handle<String> pattern = args.at<String>(2);
   Handle<String> flags = args.at<String>(3);
 
   // Get the RegExp function from the context in the literals array.
   // This is the RegExp function from the context in which the
@@ skipping 7104 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal