DirectXShaderCompiler/lib/Support/RandomNumberGenerator.cpp at main · microsoft/DirectXShaderCompiler · GitHub

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//===-- 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 deterministic random number generation (RNG).

// The current implementation is NOT cryptographically secure as it uses

// the C++11 <random> facilities.

//===----------------------------------------------------------------------===//

#include "llvm/Support/RandomNumberGenerator.h"

#include "llvm/Support/CommandLine.h"

#include "llvm/Support/Debug.h"

#include "llvm/Support/raw_ostream.h"

using namespace llvm;

#define DEBUG_TYPE "rng"

// 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.

#if 0 // HLSL Change Starts - option pending

static cl::opt<unsigned long long>

Seed("rng-seed", cl::value_desc("seed"),

cl::desc("Seed for the random number generator"), cl::init(0));

#else

static const unsigned long long Seed = 0; // will go boom in the constructor, can't be set yet

#endif // HLSL Change Ends

RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {

DEBUG(

if (Seed == 0)

dbgs() << "Warning! Using unseeded random number generator.\n"

);

// Combine seed and salts using std::seed_seq.

// Data: Seed-low, Seed-high, Salt

// Note: std::seed_seq can only store 32-bit values, even though we

// are using a 64-bit RNG. This isn't a problem since the Mersenne

// twister constructor copies these correctly into its initial state.

std::vector<uint32_t> Data;

Data.reserve(2 + Salt.size());

Data.push_back(Seed);

Data.push_back(Seed >> 32);

std::copy(Salt.begin(), Salt.end(), Data.end());

std::seed_seq SeedSeq(Data.begin(), Data.end());

Generator.seed(SeedSeq);

}

uint_fast64_t RandomNumberGenerator::operator()() {

return Generator();

}

DirectXShaderCompiler/lib/Support/RandomNumberGenerator.cpp at main · microsoft/DirectXShaderCompiler · GitHub

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