[BOLT][NFC] Make DataflowAnalysis::AnnotationIndex std::optional

[Amir]

e8d6c537ac7c1caea865860fd32c1ba2623c4ddc

bolt/include/bolt/Passes/DataflowAnalysis.h

 class DataflowAnalysis {
   /// CRTP convenience methods
   Derived &derived() { return *static_cast<Derived *>(this); }
 
   const Derived &const_derived() const {
     return *static_cast<const Derived *>(this);
   }
 
-  mutable Optional<unsigned> AnnotationIndex;
+  mutable std::optional<unsigned> AnnotationIndex;
 
 protected:
   const BinaryContext &BC;
   /// Reference to the function being analysed
   BinaryFunction &Func;
 
   /// The id of the annotation allocator to be used
   MCPlusBuilder::AllocatorIdTy AllocatorId = 0;

bolt/lib/Passes/ShrinkWrapping.cpp

 // in removing/adding insn.
 class PredictiveStackPointerTracking
     : public StackPointerTrackingBase<PredictiveStackPointerTracking> {
   friend class DataflowAnalysis<PredictiveStackPointerTracking,
                                 std::pair<int, int>>;
   decltype(ShrinkWrapping::Todo) &TodoMap;
   DataflowInfoManager &Info;
 
-  Optional<unsigned> AnnotationIndex;
+  std::optional<unsigned> AnnotationIndex;
 
 protected:
   void compNextAux(const MCInst &Point,
                    const std::vector<ShrinkWrapping::WorklistItem> &TodoItems,
                    std::pair<int, int> &Res) {
     for (const ShrinkWrapping::WorklistItem &Item : TodoItems) {
       if (Item.Action == ShrinkWrapping::WorklistItem::Erase &&
           BC.MIB->isPush(Point)) {

bolt/lib/Passes/ValidateInternalCalls.cpp

 }
 
 // A special StackPointerTracking that considers internal calls
 class StackPointerTrackingForInternalCalls
     : public StackPointerTrackingBase<StackPointerTrackingForInternalCalls> {
   friend class DataflowAnalysis<StackPointerTrackingForInternalCalls,
                                 std::pair<int, int>>;
 
-  Optional<unsigned> AnnotationIndex;
+  std::optional<unsigned> AnnotationIndex;
 
 protected:
   // We change the starting state to only consider the first block as an
   // entry point, otherwise the analysis won't converge (there will be two valid
   // stack offsets, one for an external call and another for an internal call).
   std::pair<int, int> getStartingStateAtBB(const BinaryBasicBlock &BB) {
     if (&BB == &*Func.begin())
       return std::make_pair(-8, getEmpty());