Make HasWinCFI a plain bool instead of Optional<bool>

[ssijaric]

Summary

Reid suggested making HasWinCFI a plain bool defaulting to false in D50288.

It's needed in order to add HasWinCFI to MIRPrinter (D51201 adds HasWinCFI to MIRParser only). Otherwise, we'll get an assertion

HasWinCFI.hasValue() && "HasWinCFI not set yet!"'

Also, a few ARM64 Windows test cases will fail with the same assert if the ARM64 MCLayer part (D50166) goes in before the frame lowering part that sets HasWinCFI (D50288 as of now).

[rnk]

lgtm

llvm/trunk/include/llvm/CodeGen/MachineFunction.h

class MachineFunction {
   /// This is used to limit optimizations which cannot reason
   /// about the control flow of such functions.
   bool ExposesReturnsTwice = false;
 
   /// True if the function includes any inline assembly.
   bool HasInlineAsm = false;
 
   /// True if any WinCFI instruction have been emitted in this function.
-  Optional<bool> HasWinCFI;
+  bool HasWinCFI = false;
 
   /// Current high-level properties of the IR of the function (e.g. is in SSA
   /// form or whether registers have been allocated)
   MachineFunctionProperties Properties;
 
   // Allocation management for pseudo source values.
   std::unique_ptr<PseudoSourceValueManager> PSVManager;
 
public:
   }
 
   /// Set a flag that indicates that the function contains inline assembly.
   void setHasInlineAsm(bool B) {
     HasInlineAsm = B;
   }
 
   bool hasWinCFI() const {
-    assert(HasWinCFI.hasValue() && "HasWinCFI not set yet!");
-    return *HasWinCFI;
+    return HasWinCFI;
   }
   void setHasWinCFI(bool v) { HasWinCFI = v; }
 
   /// Get the function properties
   const MachineFunctionProperties &getProperties() const { return Properties; }
   MachineFunctionProperties &getProperties() { return Properties; }
 
   /// getInfo - Keep track of various per-function pieces of information for