diff options
author | JF Bastien <jfb@google.com> | 2014-06-25 15:21:42 +0000 |
---|---|---|
committer | JF Bastien <jfb@google.com> | 2014-06-25 15:21:42 +0000 |
commit | b4840d7a4d357b3f79071cccdeaadefe278b912a (patch) | |
tree | 8f88b049eebe2f703c17b70044f1ec35f5cc397e /include | |
parent | b209f33bc7e73f8125f6b911a4c8b21a1cccc125 (diff) | |
download | llvm-b4840d7a4d357b3f79071cccdeaadefe278b912a.tar.gz llvm-b4840d7a4d357b3f79071cccdeaadefe278b912a.tar.bz2 llvm-b4840d7a4d357b3f79071cccdeaadefe278b912a.tar.xz |
Random Number Generator (llvm)
Provides an abstraction for a random number generator (RNG) that produces a stream of pseudo-random numbers.
The current implementation uses C++11 facilities and is therefore not cryptographically secure.
The RNG is salted with the text of the current command line invocation.
In addition, a user may specify a seed (reproducible builds).
In clang, the seed can be set via
-frandom-seed=X
In the back end, the seed can be set via
-rng-seed=X
This is the llvm part of the patch.
clang part: D3391
URL: http://reviews.llvm.org/D3390
Author: yln
I'm landing this for the second time, it broke Windows bots the first time around.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211705 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'include')
-rw-r--r-- | include/llvm/IR/Module.h | 8 | ||||
-rw-r--r-- | include/llvm/Support/RandomNumberGenerator.h | 54 |
2 files changed, 62 insertions, 0 deletions
diff --git a/include/llvm/IR/Module.h b/include/llvm/IR/Module.h index 7230df9f79..77e5d21e29 100644 --- a/include/llvm/IR/Module.h +++ b/include/llvm/IR/Module.h @@ -29,6 +29,7 @@ namespace llvm { class FunctionType; class GVMaterializer; class LLVMContext; +class RandomNumberGenerator; class StructType; template<typename T> struct DenseMapInfo; template<typename KeyT, typename ValueT, typename KeyInfoT> class DenseMap; @@ -201,6 +202,8 @@ private: std::string ModuleID; ///< Human readable identifier for the module std::string TargetTriple; ///< Platform target triple Module compiled on void *NamedMDSymTab; ///< NamedMDNode names. + // Allow lazy initialization in const method. + mutable RandomNumberGenerator *RNG; ///< The random number generator for this module. // We need to keep the string because the C API expects us to own the string // representation. @@ -249,6 +252,11 @@ public: /// @returns a string containing the module-scope inline assembly blocks. const std::string &getModuleInlineAsm() const { return GlobalScopeAsm; } + /// Get the RandomNumberGenerator for this module. The RNG can be + /// seeded via -rng-seed=<uint64> and is salted with the ModuleID. + /// The returned RNG should not be shared across threads. + RandomNumberGenerator &getRNG() const; + /// @} /// @name Module Level Mutators /// @{ 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 |