Use separate random number generator for each randomization pass

src/IceTargetLowering.h

Index: src/IceTargetLowering.h
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 2d03a7699eb0c19d26786548ee401a7dc28a3544..542dc32559c8cf94b0eb1f4d404697767b5631d6 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -153,7 +153,7 @@ public:
   /// Tries to do address mode optimization on a single instruction.
   void doAddressOpt();
   /// Randomly insert NOPs.
-  void doNopInsertion();
+  void doNopInsertion(RandomNumberGenerator &RNG);
   /// Lowers a single non-Phi instruction.
   void lower();
   /// Inserts and lowers a single high-level instruction at a specific insertion
@@ -279,7 +279,8 @@ protected:
 
   virtual void doAddressOptLoad() {}
   virtual void doAddressOptStore() {}
-  virtual void randomlyInsertNop(float Probability) = 0;
+  virtual void randomlyInsertNop(float Probability,
+                                 RandomNumberGenerator &RNG) = 0;
   /// This gives the target an opportunity to post-process the lowered
   /// expansion before returning.
   virtual void postLower() {}