Use the macro assembler Set instead of explicit xor for clearing registers.

src/x64/macro-assembler-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
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@@ skipping 1158 matching lines @@
 
     movq(dst, kScratchRegister);
     xor_(dst, src2);
     j(positive, &zero_correct_result);  // Result was positive zero.
 
     bind(&failure);  // Reused failure exit, restores src1.
     movq(src1, kScratchRegister);
     jmp(on_not_smi_result);
 
     bind(&zero_correct_result);
-    xor_(dst, dst);
+    Set(dst, 0);
 
     bind(&correct_result);
   } else {
     SmiToInteger64(dst, src1);
     imul(dst, src2);
     j(overflow, on_not_smi_result);
     // Check for negative zero result.  If product is zero, and one
     // argument is negative, go to slow case.
     NearLabel correct_result;
     testq(dst, dst);
@@ skipping 556 matching lines @@
       Jump(adaptor, RelocInfo::CODE_TARGET);
     }
     bind(&invoke);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_