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

src/IceTargetLoweringX8632Traits.h

Index: src/IceTargetLoweringX8632Traits.h
diff --git a/src/IceTargetLoweringX8632Traits.h b/src/IceTargetLoweringX8632Traits.h
index 8b5412dda45e6d0d7640de933ad7bd96839adb2b..d55b1a8dcca5f7e035bb56ec5ae6497eda9acd76 100644
--- a/src/IceTargetLoweringX8632Traits.h
+++ b/src/IceTargetLoweringX8632Traits.h
@@ -375,7 +375,7 @@ private:
 public:
   // Return a register in RegNum's alias set that is suitable for Ty.
   static RegNumT getGprForType(Type Ty, RegNumT RegNum) {
-    assert(RegNum != RegNumT::NoRegister);
+    assert(RegNum.hasValue());
 
     if (!isScalarIntegerType(Ty)) {
       return RegNum;