Subzero: Use a proper RegNumT type instead of int32_t/SizeT.

src/IceRegAlloc.h

 //===- subzero/src/IceRegAlloc.h - Linear-scan reg. allocation --*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 40 matching lines @@
   using DefUseErrorList = llvm::SmallVector<SizeT, 10>;
 
   class IterationState {
     IterationState(const IterationState &) = delete;
     IterationState operator=(const IterationState &) = delete;
 
   public:
     IterationState() = default;
     Variable *Cur = nullptr;
     Variable *Prefer = nullptr;
-    int32_t PreferReg = Variable::NoRegister;
+    RegNumT PreferReg = RegNumT::NoRegister;
     bool AllowOverlap = false;
     llvm::SmallBitVector RegMask;
     llvm::SmallBitVector RegMaskUnfiltered;
     llvm::SmallBitVector Free;
     llvm::SmallBitVector FreeUnfiltered;
     llvm::SmallBitVector PrecoloredUnhandledMask; // Note: only used for dumping
     llvm::SmallVector<RegWeight, REGS_SIZE> Weights;
   };
 
   bool livenessValidateIntervals(const DefUseErrorList &DefsWithoutUses,
@@ skipping 59 matching lines @@
   bool FindPreference = false;
   bool FindOverlap = false;
 
   const bool Verbose;
   const bool UseReserve;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEREGALLOC_H