Introduce faster swapping primitives.

test/mjsunit/fuzz-natives.js

 // Copyright 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 142 matching lines @@
   "ResolvePossiblyDirectEval": true,
   "Log": true,
   "DeclareGlobals": true,
 
   "PromoteScheduledException": true,
   "DeleteHandleScopeExtensions": true,
 
   // That can only be invoked on Array.prototype.
   "FinishArrayPrototypeSetup": true,
 
+  "_SwapElements": true,
+
   // Performance critical function which cannot afford type checks.
   "_CallFunction": true,
 
   // Tries to allocate based on argument, and (correctly) throws
   // out-of-memory if the request is too large. In practice, the
   // size will be the number of captures of a RegExp.
   "RegExpConstructResult": true,
   "_RegExpConstructResult": true,
 
   // This function performs some checks compile time (it requires its first
@@ skipping 23 matching lines @@
     if (name in knownProblems || name in currentlyUncallable)
       continue;
     print(name);
     var argc = nativeInfo[1];
     testArgumentCount(name, argc);
     testArgumentTypes(name, argc);
   }
 }
 
 testNatives();