diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
index e501dde465cc52..a935851d5b6061 100644
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -128,7 +128,7 @@ class CompilerInstance : public ModuleLoader {
 
   /// The set of top-level modules that has already been built on the
   /// fly as part of this overall compilation action.
-  std::map<std::string, std::string> BuiltModules;
+  std::map<std::string, std::string, std::less<>> BuiltModules;
 
   /// Should we delete the BuiltModules when we're done?
   bool DeleteBuiltModules = true;
diff --git a/clang/include/clang/Lex/HeaderSearchOptions.h b/clang/include/clang/Lex/HeaderSearchOptions.h
index 30a9d7564fd335..3af49e17539561 100644
--- a/clang/include/clang/Lex/HeaderSearchOptions.h
+++ b/clang/include/clang/Lex/HeaderSearchOptions.h
@@ -115,7 +115,7 @@ class HeaderSearchOptions {
   std::string ModuleUserBuildPath;
 
   /// The mapping of module names to prebuilt module files.
-  std::map<std::string, std::string> PrebuiltModuleFiles;
+  std::map<std::string, std::string, std::less<>> PrebuiltModuleFiles;
 
   /// The directories used to load prebuilt module files.
   std::vector<std::string> PrebuiltModulePaths;
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 0db8df0fada8f8..fe787918b41bcf 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1634,15 +1634,15 @@ enum ModuleSource {
 
 /// Select a source for loading the named module and compute the filename to
 /// load it from.
-static ModuleSource
-selectModuleSource(Module *M, StringRef ModuleName, std::string &ModuleFilename,
-                   const std::map<std::string, std::string> &BuiltModules,
-                   HeaderSearch &HS) {
+static ModuleSource selectModuleSource(
+    Module *M, StringRef ModuleName, std::string &ModuleFilename,
+    const std::map<std::string, std::string, std::less<>> &BuiltModules,
+    HeaderSearch &HS) {
   assert(ModuleFilename.empty() && "Already has a module source?");
 
   // Check to see if the module has been built as part of this compilation
   // via a module build pragma.
-  auto BuiltModuleIt = BuiltModules.find(std::string(ModuleName));
+  auto BuiltModuleIt = BuiltModules.find(ModuleName);
   if (BuiltModuleIt != BuiltModules.end()) {
     ModuleFilename = BuiltModuleIt->second;
     return MS_ModuleBuildPragma;
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 73c02d7f6e6df4..65d109ebf034e1 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -145,7 +145,7 @@ std::string HeaderSearch::getCachedModuleFileName(Module *Module) {
 std::string HeaderSearch::getPrebuiltModuleFileName(StringRef ModuleName,
                                                     bool FileMapOnly) {
   // First check the module name to pcm file map.
-  auto i(HSOpts->PrebuiltModuleFiles.find(std::string(ModuleName)));
+  auto i(HSOpts->PrebuiltModuleFiles.find(ModuleName));
   if (i != HSOpts->PrebuiltModuleFiles.end())
     return i->second;
 
diff --git a/llvm/include/llvm/DebugInfo/Symbolize/Symbolize.h b/llvm/include/llvm/DebugInfo/Symbolize/Symbolize.h
index 8bfa5432b81123..632540c79b0dfd 100644
--- a/llvm/include/llvm/DebugInfo/Symbolize/Symbolize.h
+++ b/llvm/include/llvm/DebugInfo/Symbolize/Symbolize.h
@@ -114,7 +114,8 @@ class LLVMSymbolizer {
   Expected<ObjectFile *> getOrCreateObject(const std::string &Path,
                                           const std::string &ArchName);
 
-  std::map<std::string, std::unique_ptr<SymbolizableModule>> Modules;
+  std::map<std::string, std::unique_ptr<SymbolizableModule>, std::less<>>
+      Modules;
 
   /// Contains cached results of getOrCreateObjectPair().
   std::map<std::pair<std::string, std::string>, ObjectPair>
diff --git a/llvm/include/llvm/IR/ModuleSummaryIndex.h b/llvm/include/llvm/IR/ModuleSummaryIndex.h
index 1296de75325b0b..dab0ad9fe055c4 100644
--- a/llvm/include/llvm/IR/ModuleSummaryIndex.h
+++ b/llvm/include/llvm/IR/ModuleSummaryIndex.h
@@ -959,7 +959,8 @@ class ModuleSummaryIndex {
   /// with that type identifier's metadata. Produced by per module summary
   /// analysis and consumed by thin link. For more information, see description
   /// above where TypeIdCompatibleVtableInfo is defined.
-  std::map<std::string, TypeIdCompatibleVtableInfo> TypeIdCompatibleVtableMap;
+  std::map<std::string, TypeIdCompatibleVtableInfo, std::less<>>
+      TypeIdCompatibleVtableMap;
 
   /// Mapping from original ID to GUID. If original ID can map to multiple
   /// GUIDs, it will be mapped to 0.
@@ -1361,8 +1362,7 @@ class ModuleSummaryIndex {
             TypeId));
   }
 
-  const std::map<std::string, TypeIdCompatibleVtableInfo> &
-  typeIdCompatibleVtableMap() const {
+  const auto &typeIdCompatibleVtableMap() const {
     return TypeIdCompatibleVtableMap;
   }
 
@@ -1378,7 +1378,7 @@ class ModuleSummaryIndex {
   /// entry if present in the summary map. This may be used when importing.
   Optional<TypeIdCompatibleVtableInfo>
   getTypeIdCompatibleVtableSummary(StringRef TypeId) const {
-    auto I = TypeIdCompatibleVtableMap.find(std::string(TypeId));
+    auto I = TypeIdCompatibleVtableMap.find(TypeId);
     if (I == TypeIdCompatibleVtableMap.end())
       return None;
     return I->second;
diff --git a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
index d0948fd9ab8ca8..84cf4d40318ff5 100644
--- a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
+++ b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
@@ -62,7 +62,7 @@ Expected<DILineInfo>
 LLVMSymbolizer::symbolizeCode(const ObjectFile &Obj,
                               object::SectionedAddress ModuleOffset) {
   StringRef ModuleName = Obj.getFileName();
-  auto I = Modules.find(std::string(ModuleName));
+  auto I = Modules.find(ModuleName);
   if (I != Modules.end())
     return symbolizeCodeCommon(I->second.get(), ModuleOffset);