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

src/x64/codegen-x64.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 576 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 383 matching lines @@
   const char* GetName() { return "NumberToStringStub"; }
 
 #ifdef DEBUG
   void Print() {
     PrintF("NumberToStringStub\n");
   }
 #endif
 };
 
 
+class RecordWriteStub : public CodeStub {
+ public:
+  RecordWriteStub(Register object, Register addr, Register scratch)
+      : object_(object), addr_(addr), scratch_(scratch) { }
+
+  void Generate(MacroAssembler* masm);
+
+ private:
+  Register object_;
+  Register addr_;
+  Register scratch_;
+
+#ifdef DEBUG
+  void Print() {
+    PrintF("RecordWriteStub (object reg %d), (addr reg %d), (scratch reg %d)\n",
+           object_.code(), addr_.code(), scratch_.code());
+  }
+#endif
+
+  // Minor key encoding in 12 bits of three registers (object, address and
+  // scratch) OOOOAAAASSSS.
+  class ScratchBits : public BitField<uint32_t, 0, 4> {};
+  class AddressBits : public BitField<uint32_t, 4, 4> {};
+  class ObjectBits : public BitField<uint32_t, 8, 4> {};
+
+  Major MajorKey() { return RecordWrite; }
+
+  int MinorKey() {
+    // Encode the registers.
+    return ObjectBits::encode(object_.code()) |
+           AddressBits::encode(addr_.code()) |
+           ScratchBits::encode(scratch_.code());
+  }
+};
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_X64_CODEGEN_X64_H_