Port inlined version of swap primitive for sorting from ia32 to x64....

src/ia32/codegen-ia32.h

 // Copyright 2010 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 618 matching lines @@
   void GenerateRegExpExec(ZoneList<Expression*>* args);
 
   void GenerateRegExpConstructResult(ZoneList<Expression*>* args);
 
   // Support for fast native caches.
   void GenerateGetFromCache(ZoneList<Expression*>* args);
 
   // Fast support for number to string.
   void GenerateNumberToString(ZoneList<Expression*>* args);
 
-  // Fast swapping of elements.
+  // Fast swapping of elements. Takes three expressions, the object and two
+  // indices. This should only be used if the indices are known to be
+  // non-negative and within bounds of the elements array at the call site.
   void GenerateSwapElements(ZoneList<Expression*>* args);
 
   // Fast call for custom callbacks.
   void GenerateCallFunction(ZoneList<Expression*>* args);
 
   // Fast call to math functions.
   void GenerateMathPow(ZoneList<Expression*>* args);
   void GenerateMathSin(ZoneList<Expression*>* args);
   void GenerateMathCos(ZoneList<Expression*>* args);
   void GenerateMathSqrt(ZoneList<Expression*>* args);
@@ skipping 443 matching lines @@
     return ObjectBits::encode(object_.code()) |
            AddressBits::encode(addr_.code()) |
            ScratchBits::encode(scratch_.code());
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_CODEGEN_IA32_H_