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| 1 //===- subzero/src/IceRNG.cpp - PRNG implementation -----------------------===// |
| 2 // |
| 3 // The Subzero Code Generator |
| 4 // |
| 5 // This file is distributed under the University of Illinois Open Source |
| 6 // License. See LICENSE.TXT for details. |
| 7 // |
| 8 //===----------------------------------------------------------------------===// |
| 9 // |
| 10 // This file implements the random number generator. |
| 11 // |
| 12 //===----------------------------------------------------------------------===// |
| 13 |
| 14 #include <time.h> |
| 15 |
| 16 #include "llvm/Support/CommandLine.h" |
| 17 |
| 18 #include "IceRNG.h" |
| 19 |
| 20 namespace Ice { |
| 21 |
| 22 namespace { |
| 23 namespace cl = llvm::cl; |
| 24 |
| 25 cl::opt<unsigned long long> |
| 26 RandomSeed("rng-seed", cl::desc("Seed the random number generator"), |
| 27 cl::init(time(0))); |
| 28 |
| 29 } // end of anonymous namespace |
| 30 |
| 31 // TODO(wala,stichnot): Switch to RNG implementation from LLVM or C++11. |
| 32 // |
| 33 // TODO(wala,stichnot): Make it possible to replay the RNG sequence in a |
| 34 // subsequent run, for reproducing a bug. Print the seed in a comment |
| 35 // in the asm output. Embed the seed in the binary via metadata that an |
| 36 // attacker can't introspect. |
| 37 RandomNumberGenerator::RandomNumberGenerator(llvm::StringRef) |
| 38 : State(RandomSeed) {} |
| 39 |
| 40 uint64_t RandomNumberGenerator::next(uint64_t Max) { |
| 41 // Lewis, Goodman, and Miller (1969) |
| 42 State = (16807 * State) % 2147483647; |
| 43 return State % Max; |
| 44 } |
| 45 |
| 46 } // end of namespace Ice |
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