Switch to std::optional<unsigned> type for the register slot number instead of using -1

Author: hekota

clang/include/clang/Basic/Attr.td

@@ -4723,25 +4723,25 @@ def HLSLResourceBinding: InheritableAttr {
 
   private:
       RegisterType RegType;
-      int SlotNumber; // -1 if the register slot was not specified
+      std::optional<unsigned> SlotNumber;
       unsigned SpaceNumber;
 
   public:
-      void setBinding(RegisterType RT, int SlotNum, unsigned SpaceNum) {
+      void setBinding(RegisterType RT, std::optional<unsigned> SlotNum, unsigned SpaceNum) {
         RegType = RT;
         SlotNumber = SlotNum;
         SpaceNumber = SpaceNum;
       }
       bool isImplicit() const {
-        return SlotNumber < 0;
+        return !SlotNumber.has_value();
       }
       RegisterType getRegisterType() const {
         assert(!isImplicit() && "binding does not have register slot");
         return RegType;
       }
       unsigned getSlotNumber() const {
         assert(!isImplicit() && "binding does not have register slot");
-        return (unsigned)SlotNumber;
+        return SlotNumber.value();
       }
       unsigned getSpaceNumber() const {
         return SpaceNumber;

clang/lib/Sema/SemaHLSL.cpp

@@ -1569,7 +1569,7 @@ void SemaHLSL::handleResourceBindingAttr(Decl *TheDecl, const ParsedAttr &AL) {
   }
 
   RegisterType RegType = RegisterType::SRV;
-  int SlotNum = -1;
+  std::optional<unsigned> SlotNum;
   unsigned SpaceNum = 0;
 
   // Validate slot
@@ -1583,10 +1583,12 @@ void SemaHLSL::handleResourceBindingAttr(Decl *TheDecl, const ParsedAttr &AL) {
       return;
     }
     StringRef SlotNumStr = Slot.substr(1);
-    if (SlotNumStr.getAsInteger(10, SlotNum)) {
+    unsigned N;
+    if (SlotNumStr.getAsInteger(10, N)) {
       Diag(SlotLoc, diag::err_hlsl_unsupported_register_number);
       return;
     }
+    SlotNum = N;
   }
 
   // Validate space
@@ -1601,7 +1603,7 @@ void SemaHLSL::handleResourceBindingAttr(Decl *TheDecl, const ParsedAttr &AL) {
   }
 
   // If we have slot, diagnose it is the right register type for the decl
-  if (SlotNum >= 0)
+  if (SlotNum.has_value())
     if (!DiagnoseHLSLRegisterAttribute(SemaRef, SlotLoc, TheDecl, RegType,
                                        !SpaceLoc.isInvalid()))
       return;