Fix compilation with clang

src/cached-powers.cc

 // Copyright 2011 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 115 matching lines @@
   {V8_2PART_UINT64_C(0xac2820d9, 623bf429), 880, 284},
   {V8_2PART_UINT64_C(0x80444b5e, 7aa7cf85), 907, 292},
   {V8_2PART_UINT64_C(0xbf21e440, 03acdd2d), 933, 300},
   {V8_2PART_UINT64_C(0x8e679c2f, 5e44ff8f), 960, 308},
   {V8_2PART_UINT64_C(0xd433179d, 9c8cb841), 986, 316},
   {V8_2PART_UINT64_C(0x9e19db92, b4e31ba9), 1013, 324},
   {V8_2PART_UINT64_C(0xeb96bf6e, badf77d9), 1039, 332},
   {V8_2PART_UINT64_C(0xaf87023b, 9bf0ee6b), 1066, 340},
 };
 
+#ifdef DEBUG
 static const int kCachedPowersLength = ARRAY_SIZE(kCachedPowers);
+#endif
+
 static const int kCachedPowersOffset = 348;  // -1 * the first decimal_exponent.
 static const double kD_1_LOG2_10 = 0.30102999566398114;  //  1 / lg(10)
 // Difference between the decimal exponents in the table above.
 const int PowersOfTenCache::kDecimalExponentDistance = 8;
 const int PowersOfTenCache::kMinDecimalExponent = -348;
 const int PowersOfTenCache::kMaxDecimalExponent = 340;
 
 void PowersOfTenCache::GetCachedPowerForBinaryExponentRange(
     int min_exponent,
     int max_exponent,
@@ skipping 23 matching lines @@
   int index =
       (requested_exponent + kCachedPowersOffset) / kDecimalExponentDistance;
   CachedPower cached_power = kCachedPowers[index];
   *power = DiyFp(cached_power.significand, cached_power.binary_exponent);
   *found_exponent = cached_power.decimal_exponent;
   ASSERT(*found_exponent <= requested_exponent);
   ASSERT(requested_exponent < *found_exponent + kDecimalExponentDistance);
 }
 
 } }  // namespace v8::internal