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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
62 lines
1.8 KiB
C++
62 lines
1.8 KiB
C++
//===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===//
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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 implements random number generation (RNG).
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// The current implementation is NOT cryptographically secure as it uses
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// the C++11 <random> facilities.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "rng"
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#include "llvm/Support/RandomNumberGenerator.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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// Tracking BUG: 19665
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// http://llvm.org/bugs/show_bug.cgi?id=19665
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//
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// Do not change to cl::opt<uint64_t> since this silently breaks argument parsing.
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static cl::opt<unsigned long long>
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Seed("rng-seed", cl::value_desc("seed"),
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cl::desc("Seed for the random number generator"), cl::init(0));
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RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {
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DEBUG(
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if (Seed == 0)
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errs() << "Warning! Using unseeded random number generator.\n"
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);
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// Combine seed and salt using std::seed_seq.
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// Entropy: Seed-low, Seed-high, Salt...
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std::vector<uint32_t> Data;
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Data.reserve(2 + Salt.size()/4 + 1);
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Data.push_back(Seed);
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Data.push_back(Seed >> 32);
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uint32_t Pack = 0;
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for (size_t I = 0; I < Salt.size(); ++I) {
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Pack <<= 8;
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Pack += Salt[I];
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if (I%4 == 3)
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Data.push_back(Pack);
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}
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Data.push_back(Pack);
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std::seed_seq SeedSeq(Data.begin(), Data.end());
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Generator.seed(SeedSeq);
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}
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uint64_t RandomNumberGenerator::next(uint64_t Max) {
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std::uniform_int_distribution<uint64_t> distribution(0, Max - 1);
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return distribution(Generator);
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}
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