| //===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements deterministic random number generation (RNG). |
| // The current implementation is NOT cryptographically secure as it uses |
| // the C++11 <random> facilities. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Support/RandomNumberGenerator.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "rng" |
| |
| // Tracking BUG: 19665 |
| // http://llvm.org/bugs/show_bug.cgi?id=19665 |
| // |
| // Do not change to cl::opt<uint64_t> since this silently breaks argument parsing. |
| static cl::opt<unsigned long long> |
| Seed("rng-seed", cl::value_desc("seed"), |
| cl::desc("Seed for the random number generator"), cl::init(0)); |
| |
| RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) { |
| DEBUG( |
| if (Seed == 0) |
| dbgs() << "Warning! Using unseeded random number generator.\n" |
| ); |
| |
| // Combine seed and salts using std::seed_seq. |
| // Data: Seed-low, Seed-high, Salt |
| // Note: std::seed_seq can only store 32-bit values, even though we |
| // are using a 64-bit RNG. This isn't a problem since the Mersenne |
| // twister constructor copies these correctly into its initial state. |
| std::vector<uint32_t> Data; |
| Data.reserve(2 + Salt.size()); |
| Data.push_back(Seed); |
| Data.push_back(Seed >> 32); |
| |
| std::copy(Salt.begin(), Salt.end(), Data.end()); |
| |
| std::seed_seq SeedSeq(Data.begin(), Data.end()); |
| Generator.seed(SeedSeq); |
| } |
| |
| uint_fast64_t RandomNumberGenerator::operator()() { |
| return Generator(); |
| } |