Subzero: Prototype to make use of RegNumT::No Register more concise

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 202 matching lines @@
   /// without creating any new instructions or operands.
   enum OperandLegalization {
     Legal_None = 0,
     Legal_Reg = 1 << 0, // physical register, not stack location
     Legal_Imm = 1 << 1,
     Legal_Mem = 1 << 2,
     Legal_Default = ~Legal_None
   };
   typedef uint32_t LegalMask;
   Operand *legalize(Operand *From, LegalMask Allowed = Legal_Default,
-                    RegNumT RegNum = RegNumT::NoRegister);
+                    RegNumT RegNum = RegNumT());
 
-  Variable *legalizeToVar(Operand *From, RegNumT RegNum = RegNumT::NoRegister);
+  Variable *legalizeToVar(Operand *From, RegNumT RegNum = RegNumT());
 
-  Variable *legalizeToReg(Operand *From, RegNumT RegNum = RegNumT::NoRegister);
+  Variable *legalizeToReg(Operand *From, RegNumT RegNum = RegNumT());
 
-  Variable *makeReg(Type Ty, RegNumT RegNum = RegNumT::NoRegister);
+  Variable *makeReg(Type Ty, RegNumT RegNum = RegNumT());
   static Type stackSlotType();
-  Variable *copyToReg(Operand *Src, RegNumT RegNum = RegNumT::NoRegister);
+  Variable *copyToReg(Operand *Src, RegNumT RegNum = RegNumT());
 
   void addProlog(CfgNode *Node) override;
   void addEpilog(CfgNode *Node) override;
 
   // Ensure that a 64-bit Variable has been split into 2 32-bit
   // Variables, creating them if necessary.  This is needed for all
   // I64 operations.
   void split64(Variable *Var);
   Operand *loOperand(Operand *Operand);
   Operand *hiOperand(Operand *Operand);
 
-  Operand *legalizeUndef(Operand *From, RegNumT RegNum = RegNumT::NoRegister);
+  Operand *legalizeUndef(Operand *From, RegNumT RegNum = RegNumT());
 
 protected:
   explicit TargetMIPS32(Cfg *Func);
 
   void postLower() override;
 
   void lowerAlloca(const InstAlloca *Instr) override;
   void lowerArithmetic(const InstArithmetic *Instr) override;
   void lowerInt64Arithmetic(const InstArithmetic *Instr, Variable *Dest,
                             Operand *Src0, Operand *Src1);
@@ skipping 79 matching lines @@
   explicit TargetHeaderMIPS32(GlobalContext *Ctx);
 
 private:
   ~TargetHeaderMIPS32() = default;
 };
 
 } // end of namespace MIPS32
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGMIPS32_H