[MC] Use std::optional<MCRegisters> for values returned by MCRegisterInfo::getLLVMRegNum. NFC

I missed a few places when I changed the function return type in
f2b7149.

Author: topperc

llvm/tools/llvm-dwarfdump/llvm-dwarfdump.cpp

@@ -681,7 +681,7 @@ static bool dumpObjectFile(ObjectFile &Obj, DWARFContext &DICtx,
   auto GetRegName = [&MCRegInfo](uint64_t DwarfRegNum, bool IsEH) -> StringRef {
     if (!MCRegInfo)
       return {};
-    if (std::optional<unsigned> LLVMRegNum =
+    if (std::optional<MCRegister> LLVMRegNum =
             MCRegInfo->getLLVMRegNum(DwarfRegNum, IsEH))
       if (const char *RegName = MCRegInfo->getName(*LLVMRegNum))
         return StringRef(RegName);

llvm/tools/llvm-objdump/SourcePrinter.cpp

@@ -40,7 +40,7 @@ void LiveVariable::print(raw_ostream &OS, const MCRegisterInfo &MRI) const {
   DWARFExpression Expression(Data, Unit->getAddressByteSize());
 
   auto GetRegName = [&MRI, &OS](uint64_t DwarfRegNum, bool IsEH) -> StringRef {
-    if (std::optional<unsigned> LLVMRegNum =
+    if (std::optional<MCRegister> LLVMRegNum =
             MRI.getLLVMRegNum(DwarfRegNum, IsEH))
       if (const char *RegName = MRI.getName(*LLVMRegNum))
         return StringRef(RegName);

llvm/unittests/DebugInfo/DWARF/DWARFExpressionCompactPrinterTest.cpp

@@ -62,7 +62,7 @@ void DWARFExpressionCompactPrinterTest::TestExprPrinter(
   DWARFExpression Expr(DE, 8);
 
   auto GetRegName = [&](uint64_t DwarfRegNum, bool IsEH) -> StringRef {
-    if (std::optional<unsigned> LLVMRegNum =
+    if (std::optional<MCRegister> LLVMRegNum =
             this->MRI->getLLVMRegNum(DwarfRegNum, IsEH))
       if (const char *RegName = this->MRI->getName(*LLVMRegNum))
         return llvm::StringRef(RegName);