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

src/IceOperand.cpp

Index: src/IceOperand.cpp
diff --git a/src/IceOperand.cpp b/src/IceOperand.cpp
index ada16068337ebe8c78bef412e2827c1ce89ae5a6..73b0958e8699494e31c15f22a616225df7a7db11 100644
--- a/src/IceOperand.cpp
+++ b/src/IceOperand.cpp
@@ -86,7 +86,6 @@ bool operator==(const RelocatableTuple &A, const RelocatableTuple &B) {
   return true;
 }
 
-const RegNumT RegNumT::NoRegister(RegNumT::NoRegisterValue);
 RegNumT::BaseType RegNumT::Limit = 0;
 
 bool operator<(const RegWeight &A, const RegWeight &B) {
@@ -201,7 +200,7 @@ const Variable *Variable::asType(Type Ty, RegNumT NewRegNum) const {
   Variable *V = new (getCurrentCfgAllocator()->Allocate<Variable>())
       Variable(kVariable, Ty, Number);
   V->NameIndex = NameIndex;
-  V->RegNum = NewRegNum == RegNumT::NoRegister ? RegNum : NewRegNum;
+  V->RegNum = NewRegNum.hasValue() ? NewRegNum : RegNum;
   V->StackOffset = StackOffset;
   return V;
 }