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authorJF Bastien <jfb@google.com>2014-06-25 15:21:42 +0000
committerJF Bastien <jfb@google.com>2014-06-25 15:21:42 +0000
commitb4840d7a4d357b3f79071cccdeaadefe278b912a (patch)
tree8f88b049eebe2f703c17b70044f1ec35f5cc397e /lib/Support
parentb209f33bc7e73f8125f6b911a4c8b21a1cccc125 (diff)
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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.txt1
-rw-r--r--lib/Support/RandomNumberGenerator.cpp61
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);
+}