diff --git a/lib/ToolDrivers/llvm-lib/LibDriver.cpp b/lib/ToolDrivers/llvm-lib/LibDriver.cpp
index 912a09316d6..a7268d048e3 100644
--- a/lib/ToolDrivers/llvm-lib/LibDriver.cpp
+++ b/lib/ToolDrivers/llvm-lib/LibDriver.cpp
@@ -40,31 +40,31 @@ enum {
 #include "Options.inc"
 #undef PREFIX
 
-static const llvm::opt::OptTable::Info InfoTable[] = {
+static const opt::OptTable::Info InfoTable[] = {
 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12)      \
-  {X1, X2, X10,         X11,         OPT_##ID, llvm::opt::Option::KIND##Class, \
+  {X1, X2, X10,         X11,         OPT_##ID, opt::Option::KIND##Class,       \
    X9, X8, OPT_##GROUP, OPT_##ALIAS, X7,       X12},
 #include "Options.inc"
 #undef OPTION
 };
 
-class LibOptTable : public llvm::opt::OptTable {
+class LibOptTable : public opt::OptTable {
 public:
   LibOptTable() : OptTable(InfoTable, true) {}
 };
 
 }
 
-static std::string getOutputPath(llvm::opt::InputArgList *Args,
-                                 const llvm::NewArchiveMember &FirstMember) {
+static std::string getOutputPath(opt::InputArgList *Args,
+                                 const NewArchiveMember &FirstMember) {
   if (auto *Arg = Args->getLastArg(OPT_out))
     return Arg->getValue();
   SmallString<128> Val = StringRef(FirstMember.Buf->getBufferIdentifier());
-  llvm::sys::path::replace_extension(Val, ".lib");
+  sys::path::replace_extension(Val, ".lib");
   return Val.str();
 }
 
-static std::vector<StringRef> getSearchPaths(llvm::opt::InputArgList *Args,
+static std::vector<StringRef> getSearchPaths(opt::InputArgList *Args,
                                              StringSaver &Saver) {
   std::vector<StringRef> Ret;
   // Add current directory as first item of the search path.
@@ -87,28 +87,29 @@ static std::vector<StringRef> getSearchPaths(llvm::opt::InputArgList *Args,
   return Ret;
 }
 
-static Optional<std::string> findInputFile(StringRef File,
-                                           ArrayRef<StringRef> Paths) {
-  for (auto Dir : Paths) {
+static std::string findInputFile(StringRef File, ArrayRef<StringRef> Paths) {
+  for (StringRef Dir : Paths) {
     SmallString<128> Path = Dir;
     sys::path::append(Path, File);
     if (sys::fs::exists(Path))
       return Path.str().str();
   }
-  return Optional<std::string>();
+  return "";
 }
 
-int llvm::libDriverMain(llvm::ArrayRef<const char*> ArgsArr) {
-  SmallVector<const char *, 20> NewArgs(ArgsArr.begin(), ArgsArr.end());
+int llvm::libDriverMain(ArrayRef<const char *> ArgsArr) {
   BumpPtrAllocator Alloc;
   StringSaver Saver(Alloc);
+
+  // Parse command line arguments.
+  SmallVector<const char *, 20> NewArgs(ArgsArr.begin(), ArgsArr.end());
   cl::ExpandResponseFiles(Saver, cl::TokenizeWindowsCommandLine, NewArgs);
   ArgsArr = NewArgs;
 
   LibOptTable Table;
   unsigned MissingIndex;
   unsigned MissingCount;
-  llvm::opt::InputArgList Args =
+  opt::InputArgList Args =
       Table.ParseArgs(ArgsArr.slice(1), MissingIndex, MissingCount);
   if (MissingCount) {
     llvm::errs() << "missing arg value for \""
@@ -120,32 +121,33 @@ int llvm::libDriverMain(llvm::ArrayRef<const char*> ArgsArr) {
   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
     llvm::errs() << "ignoring unknown argument: " << Arg->getSpelling() << "\n";
 
-  if (!Args.hasArgNoClaim(OPT_INPUT)) {
-    // No input files.  To match lib.exe, silently do nothing.
+  // If no input files, silently do nothing to match lib.exe.
+  if (!Args.hasArgNoClaim(OPT_INPUT))
     return 0;
-  }
 
   std::vector<StringRef> SearchPaths = getSearchPaths(&Args, Saver);
 
-  std::vector<llvm::NewArchiveMember> Members;
+  // Create a NewArchiveMember for each input file.
+  std::vector<NewArchiveMember> Members;
   for (auto *Arg : Args.filtered(OPT_INPUT)) {
-    Optional<std::string> Path = findInputFile(Arg->getValue(), SearchPaths);
-    if (!Path.hasValue()) {
+    std::string Path = findInputFile(Arg->getValue(), SearchPaths);
+    if (Path.empty()) {
       llvm::errs() << Arg->getValue() << ": no such file or directory\n";
       return 1;
     }
+
     Expected<NewArchiveMember> MOrErr =
-        NewArchiveMember::getFile(Saver.save(*Path), /*Deterministic=*/true);
+        NewArchiveMember::getFile(Saver.save(Path), /*Deterministic=*/true);
     if (!MOrErr) {
-      handleAllErrors(MOrErr.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
+      handleAllErrors(MOrErr.takeError(), [&](const ErrorInfoBase &EIB) {
         llvm::errs() << Arg->getValue() << ": " << EIB.message() << "\n";
       });
       return 1;
     }
-    llvm::file_magic Magic = llvm::identify_magic(MOrErr->Buf->getBuffer());
-    if (Magic != llvm::file_magic::coff_object &&
-        Magic != llvm::file_magic::bitcode &&
-        Magic != llvm::file_magic::windows_resource) {
+
+    file_magic Magic = identify_magic(MOrErr->Buf->getBuffer());
+    if (Magic != file_magic::coff_object && Magic != file_magic::bitcode &&
+        Magic != file_magic::windows_resource) {
       llvm::errs() << Arg->getValue()
                    << ": not a COFF object, bitcode or resource file\n";
       return 1;
@@ -153,11 +155,12 @@ int llvm::libDriverMain(llvm::ArrayRef<const char*> ArgsArr) {
     Members.emplace_back(std::move(*MOrErr));
   }
 
+  // Create an archive file.
   std::string OutputPath = getOutputPath(&Args, Members[0]);
   std::error_code EC =
-      llvm::writeArchive(OutputPath, Members,
-                         /*WriteSymtab=*/true, object::Archive::K_GNU,
-                         /*Deterministic*/ true, Args.hasArg(OPT_llvmlibthin));
+      writeArchive(OutputPath, Members,
+                   /*WriteSymtab=*/true, object::Archive::K_GNU,
+                   /*Deterministic*/ true, Args.hasArg(OPT_llvmlibthin));
 
   if (EC) {
     llvm::errs() << OutputPath << ": " << EC.message() << "\n";