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author | JF Bastien <jfb@google.com> | 2014-06-25 15:21:42 +0000 |
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committer | JF Bastien <jfb@google.com> | 2014-06-25 15:21:42 +0000 |
commit | b4840d7a4d357b3f79071cccdeaadefe278b912a (patch) | |
tree | 8f88b049eebe2f703c17b70044f1ec35f5cc397e /lib/Support | |
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 'lib/Support')
-rw-r--r-- | lib/Support/CMakeLists.txt | 1 | ||||
-rw-r--r-- | lib/Support/RandomNumberGenerator.cpp | 61 |
2 files changed, 62 insertions, 0 deletions
diff --git a/lib/Support/CMakeLists.txt b/lib/Support/CMakeLists.txt index 354e2003b5..033eae041c 100644 --- a/lib/Support/CMakeLists.txt +++ b/lib/Support/CMakeLists.txt @@ -41,6 +41,7 @@ add_llvm_library(LLVMSupport MD5.cpp PluginLoader.cpp PrettyStackTrace.cpp + RandomNumberGenerator.cpp Regex.cpp ScaledNumber.cpp SmallPtrSet.cpp diff --git a/lib/Support/RandomNumberGenerator.cpp b/lib/Support/RandomNumberGenerator.cpp new file mode 100644 index 0000000000..c50e7cb8fb --- /dev/null +++ b/lib/Support/RandomNumberGenerator.cpp @@ -0,0 +1,61 @@ +//===-- 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... + std::vector<uint32_t> Data; + Data.reserve(2 + Salt.size()/4 + 1); + Data.push_back(Seed); + Data.push_back(Seed >> 32); + + uint32_t Pack = 0; + for (size_t I = 0; I < Salt.size(); ++I) { + Pack <<= 8; + Pack += Salt[I]; + + if (I%4 == 3) + Data.push_back(Pack); + } + Data.push_back(Pack); + + std::seed_seq SeedSeq(Data.begin(), Data.end()); + Generator.seed(SeedSeq); +} + +uint64_t RandomNumberGenerator::next(uint64_t Max) { + std::uniform_int_distribution<uint64_t> distribution(0, Max - 1); + return distribution(Generator); +} |