[ARM64] removed unused variable.

src/arm64/code-stubs-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/code-stubs.h"
 #include "src/api-arguments.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 672 matching lines @@
   __ Ret(return_address);
 }
 
 void MathPowStub::Generate(MacroAssembler* masm) {
   // Stack on entry:
   // jssp[0]: Exponent (as a tagged value).
   // jssp[1]: Base (as a tagged value).
   //
   // The (tagged) result will be returned in x0, as a heap number.
 
-  Register result_tagged = x0;
   Register exponent_tagged = MathPowTaggedDescriptor::exponent();
   DCHECK(exponent_tagged.is(x11));
   Register exponent_integer = MathPowIntegerDescriptor::exponent();
   DCHECK(exponent_integer.is(x12));
   Register saved_lr = x19;
   FPRegister result_double = d0;
   FPRegister base_double = d0;
   FPRegister exponent_double = d1;
   FPRegister base_double_copy = d2;
   FPRegister scratch1_double = d6;
@@ skipping 4893 matching lines @@
                            kStackUnwindSpace, NULL, spill_offset,
                            return_value_operand, NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64