Introduce faster swapping primitives.

src/runtime.h

 // Copyright 2006-2008 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 214 matching lines @@
   F(SetProperty, -1 /* 3 or 4 */, 1) \
   F(DefineOrRedefineDataProperty, 4, 1) \
   F(DefineOrRedefineAccessorProperty, 5, 1) \
   F(IgnoreAttributesAndSetProperty, -1 /* 3 or 4 */, 1) \
   \
   /* Arrays */ \
   F(RemoveArrayHoles, 2, 1) \
   F(GetArrayKeys, 2, 1) \
   F(MoveArrayContents, 2, 1) \
   F(EstimateNumberOfElements, 1, 1) \
+  F(SwapElements, 3, 1) \
   \
   /* Getters and Setters */ \
   F(DefineAccessor, -1 /* 4 or 5 */, 1) \
   F(LookupAccessor, 3, 1) \
   \
   /* Literals */ \
   F(MaterializeRegExpLiteral, 4, 1)\
   F(CreateArrayLiteralBoilerplate, 3, 1) \
   F(CloneLiteralBoilerplate, 1, 1) \
   F(CloneShallowLiteralBoilerplate, 1, 1) \
@@ skipping 198 matching lines @@
                                                 int position);
 
   // Helper functions used stubs.
   static void PerformGC(Object* result);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_RUNTIME_H_