Subzero: Randomize register assignment.

src/IceRNG.h

Index: src/IceRNG.h
diff --git a/src/IceRNG.h b/src/IceRNG.h
index 423aee00e233110a5aeb783ffcda8ba07661781a..b132915358da6185b2c8d20713aa1cc4e7094950 100644
--- a/src/IceRNG.h
+++ b/src/IceRNG.h
@@ -16,6 +16,7 @@
 
 #include <stdint.h>
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Compiler.h"
 
 namespace Ice {
 
@@ -25,9 +26,32 @@ public:
   uint64_t next(uint64_t Max);
 
 private:
+  RandomNumberGenerator(const RandomNumberGenerator &) LLVM_DELETED_FUNCTION;
+  RandomNumberGenerator &
+  operator=(const RandomNumberGenerator &) LLVM_DELETED_FUNCTION;
+
   uint64_t State;
 };
 
+// This class adds additional random number generator utilities. The
+// reason for the wrapper class is that we want to keep the
+// RandomNumberGenerator interface identical to LLVM's.
+class RandomNumberGeneratorWrapper {
+public:
+  uint64_t operator()(uint64_t Max) { return RNG.next(Max); }
+  uint64_t next(uint64_t Max) { return RNG.next(Max); }
+  bool getTrueWithProbability(float Probability);
+  RandomNumberGeneratorWrapper(RandomNumberGenerator &RNG) : RNG(RNG) {}
+
+private:
+  RandomNumberGeneratorWrapper(const RandomNumberGeneratorWrapper &)
+      LLVM_DELETED_FUNCTION;
+  RandomNumberGeneratorWrapper &
+  operator=(const RandomNumberGeneratorWrapper &) LLVM_DELETED_FUNCTION;
+
+  RandomNumberGenerator &RNG;
+};
+
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICERNG_H