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

src/x64/builtins-x64.cc

 // 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 404 matching lines @@
   // while rdi holds the function pointer and rsi the context.
 #ifdef _WIN64
   // MSVC parameters in:
   // rcx : entry (ignored)
   // rdx : function
   // r8 : receiver
   // r9 : argc
   // [rsp+0x20] : argv
 
   // Clear the context before we push it when entering the JS frame.
-  __ xor_(rsi, rsi);
+  __ Set(rsi, 0);
   __ EnterInternalFrame();
 
   // Load the function context into rsi.
   __ movq(rsi, FieldOperand(rdx, JSFunction::kContextOffset));
 
   // Push the function and the receiver onto the stack.
   __ push(rdx);
   __ push(r8);
 
   // Load the number of arguments and setup pointer to the arguments.
   __ movq(rax, r9);
   // Load the previous frame pointer to access C argument on stack
   __ movq(kScratchRegister, Operand(rbp, 0));
   __ movq(rbx, Operand(kScratchRegister, EntryFrameConstants::kArgvOffset));
   // Load the function pointer into rdi.
   __ movq(rdi, rdx);
 #else  // _WIN64
   // GCC parameters in:
   // rdi : entry (ignored)
   // rsi : function
   // rdx : receiver
   // rcx : argc
   // r8  : argv
 
   __ movq(rdi, rsi);
   // rdi : function
 
   // Clear the context before we push it when entering the JS frame.
-  __ xor_(rsi, rsi);
+  __ Set(rsi, 0);
   // Enter an internal frame.
   __ EnterInternalFrame();
 
   // Push the function and receiver and setup the context.
   __ push(rdi);
   __ push(rdx);
   __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
 
   // Load the number of arguments and setup pointer to the arguments.
   __ movq(rax, rcx);
   __ movq(rbx, r8);
 #endif  // _WIN64
 
   // Current stack contents:
   // [rsp + 2 * kPointerSize ... ]: Internal frame
   // [rsp + kPointerSize]         : function
   // [rsp]                        : receiver
   // Current register contents:
   // rax : argc
   // rbx : argv
   // rsi : context
   // rdi : function
 
   // Copy arguments to the stack in a loop.
   // Register rbx points to array of pointers to handle locations.
   // Push the values of these handles.
   Label loop, entry;
-  __ xor_(rcx, rcx);  // Set loop variable to 0.
+  __ Set(rcx, 0);  // Set loop variable to 0.
   __ jmp(&entry);
   __ bind(&loop);
   __ movq(kScratchRegister, Operand(rbx, rcx, times_pointer_size, 0));
   __ push(Operand(kScratchRegister, 0));  // dereference handle
   __ addq(rcx, Immediate(1));
   __ bind(&entry);
   __ cmpq(rcx, rax);
   __ j(not_equal, &loop);
 
   // Invoke the code.
@@ skipping 168 matching lines @@
     __ jmp(&shift_arguments);
   }
 
 
   // 3b. Patch the first argument when calling a non-function.  The
   //     CALL_NON_FUNCTION builtin expects the non-function callee as
   //     receiver, so overwrite the first argument which will ultimately
   //     become the receiver.
   __ bind(&non_function);
   __ movq(Operand(rsp, rax, times_pointer_size, 0), rdi);
-  __ xor_(rdi, rdi);
+  __ Set(rdi, 0);
 
   // 4. Shift arguments and return address one slot down on the stack
   //    (overwriting the original receiver).  Adjust argument count to make
   //    the original first argument the new receiver.
   __ bind(&shift_arguments);
   { Label loop;
     __ movq(rcx, rax);
     __ bind(&loop);
     __ movq(rbx, Operand(rsp, rcx, times_pointer_size, 0));
     __ movq(Operand(rsp, rcx, times_pointer_size, 1 * kPointerSize), rbx);
     __ decq(rcx);
     __ j(not_sign, &loop);  // While non-negative (to copy return address).
     __ pop(rbx);  // Discard copy of return address.
     __ decq(rax);  // One fewer argument (first argument is new receiver).
   }
 
   // 5a. Call non-function via tail call to CALL_NON_FUNCTION builtin.
   { Label function;
     __ testq(rdi, rdi);
     __ j(not_zero, &function);
-    __ xor_(rbx, rbx);
+    __ Set(rbx, 0);
     __ GetBuiltinEntry(rdx, Builtins::CALL_NON_FUNCTION);
     __ Jump(Handle<Code>(builtin(ArgumentsAdaptorTrampoline)),
             RelocInfo::CODE_TARGET);
     __ bind(&function);
   }
 
   // 5b. Get the code to call from the function and check that the number of
   //     expected arguments matches what we're providing.  If so, jump
   //     (tail-call) to the code in register edx without checking arguments.
   __ movq(rdx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
@@ skipping 679 matching lines @@
 void Builtins::Generate_OnStackReplacement(MacroAssembler* masm) {
   __ int3();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64