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Diffstat (limited to 'include/llvm/Support/RandomNumberGenerator.h')
-rw-r--r-- | include/llvm/Support/RandomNumberGenerator.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/include/llvm/Support/RandomNumberGenerator.h b/include/llvm/Support/RandomNumberGenerator.h new file mode 100644 index 0000000000..1ec2c7eca9 --- /dev/null +++ b/include/llvm/Support/RandomNumberGenerator.h @@ -0,0 +1,54 @@ +//==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file defines an abstraction for random number generation (RNG). +// Note that the current implementation is not cryptographically secure +// as it uses the C++11 <random> facilities. +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ +#define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ + +#include "llvm/ADT/StringRef.h" +#include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows. +#include <random> + +namespace llvm { + +/// A random number generator. +/// Instances of this class should not be shared across threads. +class RandomNumberGenerator { +public: + /// Seeds and salts the underlying RNG engine. The salt of type StringRef + /// is passed into the constructor. The seed can be set on the command + /// line via -rng-seed=<uint64>. + /// The reason for the salt is to ensure different random streams even if + /// the same seed is used for multiple invocations of the compiler. + /// A good salt value should add additional entropy and be constant across + /// different machines (i.e., no paths) to allow for reproducible builds. + /// An instance of this class can be retrieved from the current Module. + /// \see Module::getRNG + RandomNumberGenerator(StringRef Salt); + + /// Returns a random number in the range [0, Max). + uint64_t next(uint64_t Max); + +private: + // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000 + // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine + std::mt19937_64 Generator; + + // Noncopyable. + RandomNumberGenerator(const RandomNumberGenerator &other) = delete; + RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete; +}; +} + +#endif |