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6feedc56f7
Summary: With MSVC 2013 and GCC < 4.8 gone, we can use the "constexpr" keyword. Reviewers: bkramer, mehdi_amini Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D25901 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284947 91177308-0d34-0410-b5e6-96231b3b80d8
81 lines
2.6 KiB
C++
81 lines
2.6 KiB
C++
//==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines an abstraction for deterministic random number
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// generation (RNG). Note that the current implementation is not
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// cryptographically secure as it uses the C++11 <random> facilities.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_
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#define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows.
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#include <random>
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#include <system_error>
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namespace llvm {
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class StringRef;
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/// A random number generator.
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///
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/// Instances of this class should not be shared across threads. The
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/// seed should be set by passing the -rng-seed=<uint64> option. Use
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/// Module::createRNG to create a new RNG instance for use with that
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/// module.
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class RandomNumberGenerator {
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// 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000
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// http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine
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// This RNG is deterministically portable across C++11
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// implementations.
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using generator_type = std::mt19937_64;
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public:
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using result_type = generator_type::result_type;
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/// Returns a random number in the range [0, Max).
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result_type operator()();
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// We can only make min/max constexpr if generator_type::min/max are
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// constexpr. The MSVC 2013 STL does not make these constexpr, so we have to
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// avoid declaring them as constexpr even if the compiler, like clang-cl,
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// supports it.
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#if defined(_MSC_VER) && _MSC_VER < 1900
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#define STL_CONSTEXPR
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#else
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#define STL_CONSTEXPR constexpr
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#endif
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static STL_CONSTEXPR result_type min() { return generator_type::min(); }
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static STL_CONSTEXPR result_type max() { return generator_type::max(); }
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private:
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/// Seeds and salts the underlying RNG engine.
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///
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/// This constructor should not be used directly. Instead use
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/// Module::createRNG to create a new RNG salted with the Module ID.
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RandomNumberGenerator(StringRef Salt);
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generator_type Generator;
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// Noncopyable.
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RandomNumberGenerator(const RandomNumberGenerator &other) = delete;
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RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete;
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friend class Module;
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};
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// Get random vector of specified size
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std::error_code getRandomBytes(void *Buffer, size_t Size);
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}
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#endif
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