Use separate random number generator for each randomization pass

src/IceTargetLoweringMIPS32.h

 //===- subzero/src/IceTargetLoweringMIPS32.h - MIPS32 lowering ---*- C++-*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 98 matching lines @@
   void lowerLoad(const InstLoad *Inst) override;
   void lowerPhi(const InstPhi *Inst) override;
   void lowerRet(const InstRet *Inst) override;
   void lowerSelect(const InstSelect *Inst) override;
   void lowerStore(const InstStore *Inst) override;
   void lowerSwitch(const InstSwitch *Inst) override;
   void lowerUnreachable(const InstUnreachable *Inst) override;
   void prelowerPhis() override;
   void doAddressOptLoad() override;
   void doAddressOptStore() override;
-  void randomlyInsertNop(float Probability) override;
-  void makeRandomRegisterPermutation(
-      llvm::SmallVectorImpl<int32_t> &Permutation,
-      const llvm::SmallBitVector &ExcludeRegisters) const override;
+  void randomlyInsertNop(float Probability,
+                         RandomNumberGenerator &RNG) override;
+  void
+  makeRandomRegisterPermutation(llvm::SmallVectorImpl<int32_t> &Permutation,
+                                const llvm::SmallBitVector &ExcludeRegisters,
+                                uint64_t Salt) const override;
 
   static Type stackSlotType();
 
   bool UsesFramePointer = false;
   bool NeedsStackAlignment = false;
   llvm::SmallBitVector TypeToRegisterSet[IceType_NUM];
   llvm::SmallBitVector ScratchRegs;
   llvm::SmallBitVector RegsUsed;
   VarList PhysicalRegisters[IceType_NUM];
 
@@ skipping 37 matching lines @@
 protected:
   explicit TargetHeaderMIPS32(GlobalContext *Ctx);
 
 private:
   ~TargetHeaderMIPS32() = default;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGMIPS32_H