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

src/x64/regexp-macro-assembler-x64.cc

 // Copyright 2009 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 670 matching lines @@
     return true;
   // No custom implementation (yet): s(UC16), S(UC16).
   default:
     return false;
   }
 }
 
 
 void RegExpMacroAssemblerX64::Fail() {
   ASSERT(FAILURE == 0);  // Return value for failure is zero.
-  __ xor_(rax, rax);  // zero rax.
+  __ Set(rax, 0);
   __ jmp(&exit_label_);
 }
 
 
 Handle<Object> RegExpMacroAssemblerX64::GetCode(Handle<String> source) {
   // Finalize code - write the entry point code now we know how many
   // registers we need.
   // Entry code:
   __ bind(&entry_label_);
   // Start new stack frame.
@@ skipping 671 matching lines @@
   }
 }
 
 #undef __
 
 #endif  // V8_INTERPRETED_REGEXP
 
 }}  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64