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author | JF Bastien <jfb@google.com> | 2014-06-18 06:23:25 +0000 |
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committer | JF Bastien <jfb@google.com> | 2014-06-18 06:23:25 +0000 |
commit | 1d04a2324c4e86320b5452f5262782c569cd3315 (patch) | |
tree | b420a99cb06a321a7832af249a3a7d58493651bd /lib/Support/RandomNumberGenerator.cpp | |
parent | 74287ec34c1443e462aba573c6e8f7d7f9defa35 (diff) | |
download | llvm-1d04a2324c4e86320b5452f5262782c569cd3315.tar.gz llvm-1d04a2324c4e86320b5452f5262782c569cd3315.tar.bz2 llvm-1d04a2324c4e86320b5452f5262782c569cd3315.tar.xz |
Random Number Generator (llvm)
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
Diffstat (limited to 'lib/Support/RandomNumberGenerator.cpp')
-rw-r--r-- | lib/Support/RandomNumberGenerator.cpp | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/lib/Support/RandomNumberGenerator.cpp b/lib/Support/RandomNumberGenerator.cpp new file mode 100644 index 0000000000..5513982e7b --- /dev/null +++ b/lib/Support/RandomNumberGenerator.cpp @@ -0,0 +1,52 @@ +//===-- 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); +} |