ARM64: Faster immediate check and fix corner cases

src/arm64/utils-arm64.h

 // 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.
 
 #ifndef V8_ARM64_UTILS_ARM64_H_
 #define V8_ARM64_UTILS_ARM64_H_
 
 #include <cmath>
 #include "src/v8.h"
 
@@ skipping 39 matching lines @@
   memcpy(&value, &bits, 8);
   return value;
 }
 
 
 // Bit counting.
 int CountLeadingZeros(uint64_t value, int width);
 int CountLeadingSignBits(int64_t value, int width);
 int CountTrailingZeros(uint64_t value, int width);
 int CountSetBits(uint64_t value, int width);
+uint64_t LargestPowerOf2Divisor(uint64_t value);
 int MaskToBit(uint64_t mask);
 
 
 // NaN tests.
 inline bool IsSignallingNaN(double num) {
   uint64_t raw = double_to_rawbits(num);
   if (std::isnan(num) && ((raw & kDQuietNanMask) == 0)) {
     return true;
   }
   return false;
@@ skipping 34 matching lines @@
 }
 
 
 inline float FusedMultiplyAdd(float op1, float op2, float a) {
   return fmaf(op1, op2, a);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM64_UTILS_ARM64_H_