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.
llvm-svn: 211705
diff --git a/llvm/lib/IR/Module.cpp b/llvm/lib/IR/Module.cpp
index eea14df..9889f00 100644
--- a/llvm/lib/IR/Module.cpp
+++ b/llvm/lib/IR/Module.cpp
@@ -24,6 +24,8 @@
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LeakDetector.h"
#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/RandomNumberGenerator.h"
#include <algorithm>
#include <cstdarg>
#include <cstdlib>
@@ -44,7 +46,7 @@
//
Module::Module(StringRef MID, LLVMContext &C)
- : Context(C), Materializer(), ModuleID(MID), DL("") {
+ : Context(C), Materializer(), ModuleID(MID), RNG(nullptr), DL("") {
ValSymTab = new ValueSymbolTable();
NamedMDSymTab = new StringMap<NamedMDNode *>();
Context.addModule(this);
@@ -59,6 +61,7 @@
NamedMDList.clear();
delete ValSymTab;
delete static_cast<StringMap<NamedMDNode *> *>(NamedMDSymTab);
+ delete RNG;
}
/// getNamedValue - Return the first global value in the module with
@@ -355,6 +358,16 @@
return &DL;
}
+// We want reproducible builds, but ModuleID may be a full path so we just use
+// the filename to salt the RNG (although it is not guaranteed to be unique).
+RandomNumberGenerator &Module::getRNG() const {
+ if (RNG == nullptr) {
+ StringRef Salt = sys::path::filename(ModuleID);
+ RNG = new RandomNumberGenerator(Salt);
+ }
+ return *RNG;
+}
+
//===----------------------------------------------------------------------===//
// Methods to control the materialization of GlobalValues in the Module.
//