Summary:
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
Reviewers: ahomescu, rinon, nicholas, jfb
Reviewed By: jfb
Subscribers: jfb, perl
Differential Revision: http://reviews.llvm.org/D3390
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211145
91177308-0d34-0410-b5e6-
96231b3b80d8
class FunctionType;
class GVMaterializer;
class LLVMContext;
+class RandomNumberGenerator;
class StructType;
template<typename T> struct DenseMapInfo;
template<typename KeyT, typename ValueT, typename KeyInfoT> class DenseMap;
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.
/// @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
/// @{
--- /dev/null
+//==- 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 <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
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LeakDetector.h"
#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/RandomNumberGenerator.h"
#include <algorithm>
#include <cstdarg>
#include <cstdlib>
//
Module::Module(StringRef MID, LLVMContext &C)
- : Context(C), Materializer(), ModuleID(MID), DL("") {
+ : Context(C), Materializer(), ModuleID(MID), RNG(nullptr), DL("") {
ValSymTab = new ValueSymbolTable();
NamedMDSymTab = new StringMap<NamedMDNode *>();
Context.addModule(this);
NamedMDList.clear();
delete ValSymTab;
delete static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab);
+ delete RNG;
}
/// getNamedValue - Return the first global value in the module with
return &DL;
}
+// We want reproducible builds, but ModuleID may be a full path so we just use
+// the filename to salt the RNG (although it is not guaranteed to be unique).
+RandomNumberGenerator &Module::getRNG() const {
+ if (RNG == nullptr) {
+ StringRef Salt = sys::path::filename(ModuleID);
+ RNG = new RandomNumberGenerator(Salt);
+ }
+ return *RNG;
+}
+
//===----------------------------------------------------------------------===//
// Methods to control the materialization of GlobalValues in the Module.
//
MD5.cpp
PluginLoader.cpp
PrettyStackTrace.cpp
+ RandomNumberGenerator.cpp
Regex.cpp
SmallPtrSet.cpp
SmallVector.cpp
--- /dev/null
+//===-- 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 random number generation (RNG).
+// The current implementation is NOT cryptographically secure as it uses
+// the C++11 <random> facilities.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "rng"
+#include "llvm/Support/RandomNumberGenerator.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+// 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)
+ errs() << "Warning! Using unseeded random number generator.\n"
+ );
+
+ // Combine seed and salt using std::seed_seq.
+ // Entropy: Seed-low, Seed-high, Salt...
+ size_t Size = Salt.size() + 2;
+ uint32_t Data[Size];
+ Data[0] = Seed;
+ Data[1] = Seed >> 32;
+ std::copy_n(Salt.begin(), Salt.size(), Data + 2);
+
+ std::seed_seq SeedSeq(Data, Data + Size);
+ Generator.seed(SeedSeq);
+}
+
+uint64_t RandomNumberGenerator::next(uint64_t Max) {
+ std::uniform_int_distribution<uint64_t> distribution(0, Max - 1);
+ return distribution(Generator);
+}