diff --git a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
--- a/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
+++ b/clang-tools-extra/clang-apply-replacements/lib/Tooling/ApplyReplacements.cpp
@@ -37,9 +37,11 @@
 namespace clang {
 namespace replace {
 
-std::error_code collectReplacementsFromDirectory(
-    const llvm::StringRef Directory, TUReplacements &TUs,
-    TUReplacementFiles &TUFiles, clang::DiagnosticsEngine &Diagnostics) {
+template <typename T>
+std::error_code
+collectReplacementsFromDirectoryImpl(const llvm::StringRef Directory, T &TUs,
+                                     TUReplacementFiles &TUFiles,
+                                     clang::DiagnosticsEngine &Diagnostics) {
   using namespace llvm::sys::fs;
   using namespace llvm::sys::path;
 
@@ -67,7 +69,7 @@
     }
 
     yaml::Input YIn(Out.get()->getBuffer(), nullptr, &eatDiagnostics);
-    tooling::TranslationUnitReplacements TU;
+    typename T::value_type TU;
     YIn >> TU;
     if (YIn.error()) {
       // File doesn't appear to be a header change description. Ignore it.
@@ -82,47 +84,17 @@
 }
 
 std::error_code collectReplacementsFromDirectory(
-    const llvm::StringRef Directory, TUDiagnostics &TUs,
+    const llvm::StringRef Directory, TUReplacements &TUs,
     TUReplacementFiles &TUFiles, clang::DiagnosticsEngine &Diagnostics) {
-  using namespace llvm::sys::fs;
-  using namespace llvm::sys::path;
-
-  std::error_code ErrorCode;
-
-  for (recursive_directory_iterator I(Directory, ErrorCode), E;
-       I != E && !ErrorCode; I.increment(ErrorCode)) {
-    if (filename(I->path())[0] == '.') {
-      // Indicate not to descend into directories beginning with '.'
-      I.no_push();
-      continue;
-    }
-
-    if (extension(I->path()) != ".yaml")
-      continue;
-
-    TUFiles.push_back(I->path());
-
-    ErrorOr<std::unique_ptr<MemoryBuffer>> Out =
-        MemoryBuffer::getFile(I->path());
-    if (std::error_code BufferError = Out.getError()) {
-      errs() << "Error reading " << I->path() << ": " << BufferError.message()
-             << "\n";
-      continue;
-    }
-
-    yaml::Input YIn(Out.get()->getBuffer(), nullptr, &eatDiagnostics);
-    tooling::TranslationUnitDiagnostics TU;
-    YIn >> TU;
-    if (YIn.error()) {
-      // File doesn't appear to be a header change description. Ignore it.
-      continue;
-    }
-
-    // Only keep files that properly parse.
-    TUs.push_back(TU);
-  }
+  return collectReplacementsFromDirectoryImpl(Directory, TUs, TUFiles,
+                                              Diagnostics);
+}
 
-  return ErrorCode;
+std::error_code collectReplacementsFromDirectory(
+    const llvm::StringRef Directory, TUDiagnostics &TUs,
+    TUReplacementFiles &TUFiles, clang::DiagnosticsEngine &Diagnostics) {
+  return collectReplacementsFromDirectoryImpl(Directory, TUs, TUFiles,
+                                              Diagnostics);
 }
 
 /// Extract replacements from collected TranslationUnitReplacements and
@@ -163,11 +135,9 @@
     if (auto Entry = SM.getFileManager().getFile(R.getFilePath())) {
       if (SourceTU) {
         auto &Replaces = DiagReplacements[*Entry];
-        auto It = Replaces.find(R);
-        if (It == Replaces.end())
-          Replaces.emplace(R, SourceTU);
-        else if (It->second != SourceTU)
-          // This replacement is a duplicate of one suggested by another TU.
+        auto InsertPos = Replaces.try_emplace(R, SourceTU);
+        // This replacement is a duplicate of one suggested by another TU.
+        if (!InsertPos.second && InsertPos.first->second != SourceTU)
           return;
       }
       GroupedReplacements[*Entry].push_back(R);
diff --git a/llvm/include/llvm/ADT/Twine.h b/llvm/include/llvm/ADT/Twine.h
--- a/llvm/include/llvm/ADT/Twine.h
+++ b/llvm/include/llvm/ADT/Twine.h
@@ -291,9 +291,9 @@
     /// Construct from an std::string_view by converting it to a pointer and
     /// length.  This handles string_views on a pure API basis, and avoids
     /// storing one (or a pointer to one) inside a Twine, which avoids problems
-    /// when mixing code compiled under various C++ standards.
-    /*implicit*/ Twine(const std::string_view &Str)
-        : LHSKind(PtrAndLengthKind) {
+    /// when mixing code compiled under various C++ standards. Pass string_view
+    /// by value is preferred.
+    /*implicit*/ Twine(std::string_view Str) : LHSKind(PtrAndLengthKind) {
       LHS.ptrAndLength.ptr = Str.data();
       LHS.ptrAndLength.length = Str.length();
       assert(isValid() && "Invalid twine!");