Port inline swapping of elements for the sort function in array.js...

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 1015 matching lines @@
   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.
+  // Minor key encoding in 12 bits. 4 bits for each of the 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_