[turbofan] Add support for ARM64 Ubfx

src/base/utils/random-number-generator.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.
 
 #include "src/base/utils/random-number-generator.h"
 
 #include <stdio.h>
 #include <stdlib.h>
 
 #include <new>
@@ skipping 84 matching lines @@
   }
 }
 
 
 double RandomNumberGenerator::NextDouble() {
   return ((static_cast<int64_t>(Next(26)) << 27) + Next(27)) /
       static_cast<double>(static_cast<int64_t>(1) << 53);
 }
 
 
+int64_t RandomNumberGenerator::NextInt64() {
+  int64_t lo = static_cast<int64_t>(Next(32));
+  int64_t hi = static_cast<int64_t>(Next(32));
+  return (lo & 0xffffffff) | (hi << 32);
+}

[Benedikt Meurer, 2014/10/08 11:40:12]

This is undefined behaviour in C++. Should be:

uint64_t lo = bit_cast<unsigned>(Next(32));
uint64_t hi = bit_cast<unsigned>(Next(32));
return lo | (hi << 32);

[m.m.capewell, 2014/10/08 17:35:02]

Done.

+
+
 void RandomNumberGenerator::NextBytes(void* buffer, size_t buflen) {
   for (size_t n = 0; n < buflen; ++n) {
     static_cast<uint8_t*>(buffer)[n] = static_cast<uint8_t>(Next(8));
   }
 }
 
 
 int RandomNumberGenerator::Next(int bits) {
   DCHECK_LT(0, bits);
   DCHECK_GE(32, bits);
   // Do unsigned multiplication, which has the intended modulo semantics, while
   // signed multiplication would expose undefined behavior.
   uint64_t product = static_cast<uint64_t>(seed_) * kMultiplier;
   // Assigning a uint64_t to an int64_t is implementation defined, but this
   // should be OK. Use a static_cast to explicitly state that we know what we're
   // doing. (Famous last words...)
   int64_t seed = static_cast<int64_t>((product + kAddend) & kMask);
   seed_ = seed;
   return static_cast<int>(seed >> (48 - bits));
 }
 
 
 void RandomNumberGenerator::SetSeed(int64_t seed) {
   initial_seed_ = seed;
   seed_ = (seed ^ kMultiplier) & kMask;
 }
 
 } }  // namespace v8::base