mirror of
https://github.com/RPCS3/llvm.git
synced 2024-12-23 04:28:30 +00:00
b4840d7a4d
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 -------------------===//
|
|
//
|
|
// 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);
|
|
}
|