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.
 //