[arm64] Fix a GCC build warning.

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/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 2835 matching lines @@
       FixedArray::OffsetOfElementAt(TypeFeedbackVector::kWithTypesIndex);
   const int generic_offset =
       FixedArray::OffsetOfElementAt(TypeFeedbackVector::kGenericCountIndex);
   Label extra_checks_or_miss, call;
   int argc = arg_count();
   ParameterCount actual(argc);
 
   Register function = x1;
   Register feedback_vector = x2;
   Register index = x3;
-  Register type = x4;
 
   // The checks. First, does x1 match the recorded monomorphic target?
   __ Add(x4, feedback_vector,
          Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(x4, FieldMemOperand(x4, FixedArray::kHeaderSize));
 
   // We don't know that we have a weak cell. We might have a private symbol
   // or an AllocationSite, but the memory is safe to examine.
   // AllocationSite::kTransitionInfoOffset - contains a Smi or pointer to
   // FixedArray.
@@ skipping 3010 matching lines @@
                            MemOperand(fp, 6 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64