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

src/x64/code-stubs-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 86 matching lines @@
 
   // Get the function from the stack.
   __ movq(rcx, Operand(rsp, 1 * kPointerSize));
 
   // Setup the object header.
   __ LoadRoot(kScratchRegister, Heap::kContextMapRootIndex);
   __ movq(FieldOperand(rax, HeapObject::kMapOffset), kScratchRegister);
   __ Move(FieldOperand(rax, FixedArray::kLengthOffset), Smi::FromInt(length));
 
   // Setup the fixed slots.
-  __ xor_(rbx, rbx);  // Set to NULL.
+  __ Set(rbx, 0);  // Set to NULL.
   __ movq(Operand(rax, Context::SlotOffset(Context::CLOSURE_INDEX)), rcx);
   __ movq(Operand(rax, Context::SlotOffset(Context::FCONTEXT_INDEX)), rax);
   __ movq(Operand(rax, Context::SlotOffset(Context::PREVIOUS_INDEX)), rbx);
   __ movq(Operand(rax, Context::SlotOffset(Context::EXTENSION_INDEX)), rbx);
 
   // Copy the global object from the surrounding context.
   __ movq(rbx, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
   __ movq(Operand(rax, Context::SlotOffset(Context::GLOBAL_INDEX)), rbx);
 
   // Initialize the rest of the slots to undefined.
@@ skipping 125 matching lines @@
   __ xorpd(xmm0, xmm0);
   __ ucomisd(xmm0, FieldOperand(rax, HeapNumber::kValueOffset));
   __ j(zero, &false_result);
   // Fall through to |true_result|.
 
   // Return 1/0 for true/false in rax.
   __ bind(&true_result);
   __ movq(rax, Immediate(1));
   __ ret(1 * kPointerSize);
   __ bind(&false_result);
-  __ xor_(rax, rax);
+  __ Set(rax, 0);
   __ ret(1 * kPointerSize);
 }
 
 
 const char* GenericBinaryOpStub::GetName() {
   if (name_ != NULL) return name_;
   const int kMaxNameLength = 100;
   name_ = Bootstrapper::AllocateAutoDeletedArray(kMaxNameLength);
   if (name_ == NULL) return "OOM";
   const char* op_name = Token::Name(op_);
@@ skipping 2301 matching lines @@
   __ movq(kScratchRegister, handler_address);
   __ movq(rsp, Operand(kScratchRegister, 0));
   // get next in chain
   __ pop(rcx);
   __ movq(Operand(kScratchRegister, 0), rcx);
   __ pop(rbp);  // pop frame pointer
   __ pop(rdx);  // remove state
 
   // Before returning we restore the context from the frame pointer if not NULL.
   // The frame pointer is NULL in the exception handler of a JS entry frame.
-  __ xor_(rsi, rsi);  // tentatively set context pointer to NULL
+  __ Set(rsi, 0);  // Tentatively set context pointer to NULL
   NearLabel skip;
   __ cmpq(rbp, Immediate(0));
   __ j(equal, &skip);
   __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
   __ bind(&skip);
   __ ret(0);
 }
 
 
 void CEntryStub::GenerateCore(MacroAssembler* masm,
@@ skipping 163 matching lines @@
     __ movq(rax, Immediate(false));
     __ store_rax(external_caught);
 
     // Set pending exception and rax to out of memory exception.
     ExternalReference pending_exception(Top::k_pending_exception_address);
     __ movq(rax, Failure::OutOfMemoryException(), RelocInfo::NONE);
     __ store_rax(pending_exception);
   }
 
   // Clear the context pointer.
-  __ xor_(rsi, rsi);
+  __ Set(rsi, 0);
 
   // Restore registers from handler.
   STATIC_ASSERT(StackHandlerConstants::kNextOffset + kPointerSize ==
             StackHandlerConstants::kFPOffset);
   __ pop(rbp);  // FP
   STATIC_ASSERT(StackHandlerConstants::kFPOffset + kPointerSize ==
             StackHandlerConstants::kStateOffset);
   __ pop(rdx);  // State
 
   STATIC_ASSERT(StackHandlerConstants::kStateOffset + kPointerSize ==
@@ skipping 1331 matching lines @@
 
 void ICCompareStub::GenerateMiss(MacroAssembler* masm) {
   UNIMPLEMENTED();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64