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

src/IceOperand.cpp

Index: src/IceOperand.cpp
diff --git a/src/IceOperand.cpp b/src/IceOperand.cpp
index ff1de640e9a69c47d70085bd216a3a64443c9e55..2e85276b642c76b6d4e12c29014777ed612342ca 100644
--- a/src/IceOperand.cpp
+++ b/src/IceOperand.cpp
@@ -190,7 +190,7 @@ IceString Variable::getName(const Cfg *Func) const {
   return "__" + std::to_string(getIndex());
 }
 
-const Variable *Variable::asType(Type Ty, int32_t NewRegNum) const {
+const Variable *Variable::asType(Type Ty, RegNumT NewRegNum) const {
   // Note: This returns a Variable, even if the "this" object is a subclass of
   // Variable.
   if (!BuildDefs::dump() || getType() == Ty)
@@ -198,7 +198,7 @@ const Variable *Variable::asType(Type Ty, int32_t NewRegNum) const {
   Variable *V = new (getCurrentCfgAllocator()->Allocate<Variable>())
       Variable(kVariable, Ty, Number);
   V->NameIndex = NameIndex;
-  V->RegNum = NewRegNum == NoRegister ? RegNum : NewRegNum;
+  V->RegNum = NewRegNum == RegNumT::NoRegister ? RegNum : NewRegNum;
   V->StackOffset = StackOffset;
   return V;
 }
@@ -511,8 +511,8 @@ void Variable::dump(const Cfg *Func, Ostream &Str) const {
   } else if (Func->getTarget()->hasComputedFrame()) {
     if (Func->isVerbose(IceV_RegOrigins))
       Str << ":";
-    int32_t BaseRegisterNumber = getBaseRegNum();
-    if (BaseRegisterNumber == NoRegister)
+    RegNumT BaseRegisterNumber = getBaseRegNum();
+    if (BaseRegisterNumber == RegNumT::NoRegister)
       BaseRegisterNumber = Func->getTarget()->getFrameOrStackReg();
     Str << "["
         << Func->getTarget()->getRegName(BaseRegisterNumber, IceType_i32);