diff --git a/lldb/include/lldb/Target/PathMappingList.h b/lldb/include/lldb/Target/PathMappingList.h
--- a/lldb/include/lldb/Target/PathMappingList.h
+++ b/lldb/include/lldb/Target/PathMappingList.h
@@ -32,8 +32,7 @@
 
   const PathMappingList &operator=(const PathMappingList &rhs);
 
-  void Append(ConstString path, ConstString replacement,
-              bool notify);
+  void Append(llvm::StringRef path, llvm::StringRef replacement, bool notify);
 
   void Append(const PathMappingList &rhs, bool notify);
 
@@ -49,17 +48,16 @@
   bool GetPathsAtIndex(uint32_t idx, ConstString &path,
                        ConstString &new_path) const;
 
-  void Insert(ConstString path, ConstString replacement,
+  void Insert(llvm::StringRef path, llvm::StringRef replacement,
               uint32_t insert_idx, bool notify);
 
   bool Remove(size_t index, bool notify);
 
   bool Remove(ConstString path, bool notify);
 
-  bool Replace(ConstString path, ConstString replacement,
-               bool notify);
+  bool Replace(llvm::StringRef path, llvm::StringRef replacement, bool notify);
 
-  bool Replace(ConstString path, ConstString replacement,
+  bool Replace(llvm::StringRef path, llvm::StringRef replacement,
                uint32_t index, bool notify);
   bool RemapPath(ConstString path, ConstString &new_path) const;
 
@@ -104,7 +102,7 @@
   ///     The newly remapped filespec that is guaranteed to exist.
   llvm::Optional<FileSpec> FindFile(const FileSpec &orig_spec) const;
 
-  uint32_t FindIndexForPath(ConstString path) const;
+  uint32_t FindIndexForPath(llvm::StringRef path) const;
 
   uint32_t GetModificationID() const { return m_mod_id; }
 
diff --git a/lldb/source/API/SBTarget.cpp b/lldb/source/API/SBTarget.cpp
--- a/lldb/source/API/SBTarget.cpp
+++ b/lldb/source/API/SBTarget.cpp
@@ -214,8 +214,8 @@
   if (!target_sp)
     return LLDB_RECORD_RESULT(data);
   std::string json_str =
-      llvm::formatv("{0:2}", 
-          DebuggerStats::ReportStatistics(target_sp->GetDebugger(), 
+      llvm::formatv("{0:2}",
+          DebuggerStats::ReportStatistics(target_sp->GetDebugger(),
                                           target_sp.get())).str();
   data.m_impl_up->SetObjectSP(StructuredData::ParseJSON(json_str));
   return LLDB_RECORD_RESULT(data);
@@ -1586,13 +1586,13 @@
   if (!target_sp)
     return error.SetErrorString("invalid target");
 
-  const ConstString csFrom(from), csTo(to);
-  if (!csFrom)
+  llvm::StringRef srFrom(from), srTo(to);
+  if (srFrom.empty())
     return error.SetErrorString("<from> path can't be empty");
-  if (!csTo)
+  if (srTo.empty())
     return error.SetErrorString("<to> path can't be empty");
 
-  target_sp->GetImageSearchPathList().Append(csFrom, csTo, true);
+  target_sp->GetImageSearchPathList().Append(srFrom, srTo, true);
 }
 
 lldb::SBModule SBTarget::AddModule(const char *path, const char *triple,
diff --git a/lldb/source/Commands/CommandObjectTarget.cpp b/lldb/source/Commands/CommandObjectTarget.cpp
--- a/lldb/source/Commands/CommandObjectTarget.cpp
+++ b/lldb/source/Commands/CommandObjectTarget.cpp
@@ -1047,8 +1047,7 @@
           }
           bool last_pair = ((argc - i) == 2);
           target->GetImageSearchPathList().Append(
-              ConstString(from), ConstString(to),
-              last_pair); // Notify if this is the last pair
+              from, to, last_pair); // Notify if this is the last pair
           result.SetStatus(eReturnStatusSuccessFinishNoResult);
         } else {
           if (from[0])
@@ -1175,8 +1174,8 @@
 
         if (from[0] && to[0]) {
           bool last_pair = ((argc - i) == 2);
-          target->GetImageSearchPathList().Insert(
-              ConstString(from), ConstString(to), insert_idx, last_pair);
+          target->GetImageSearchPathList().Insert(from, to, insert_idx,
+                                                  last_pair);
           result.SetStatus(eReturnStatusSuccessFinishNoResult);
         } else {
           if (from[0])
diff --git a/lldb/source/Core/Module.cpp b/lldb/source/Core/Module.cpp
--- a/lldb/source/Core/Module.cpp
+++ b/lldb/source/Core/Module.cpp
@@ -1614,15 +1614,14 @@
 
 void Module::RegisterXcodeSDK(llvm::StringRef sdk_name, llvm::StringRef sysroot) {
   XcodeSDK sdk(sdk_name.str());
-  ConstString sdk_path(HostInfo::GetXcodeSDKPath(sdk));
-  if (!sdk_path)
+  llvm::StringRef sdk_path(HostInfo::GetXcodeSDKPath(sdk));
+  if (sdk_path.empty())
     return;
   // If the SDK changed for a previously registered source path, update it.
   // This could happend with -fdebug-prefix-map, otherwise it's unlikely.
-  ConstString sysroot_cs(sysroot);
-  if (!m_source_mappings.Replace(sysroot_cs, sdk_path, true))
+  if (!m_source_mappings.Replace(sysroot, sdk_path, true))
     // In the general case, however, append it to the list.
-    m_source_mappings.Append(sysroot_cs, sdk_path, false);
+    m_source_mappings.Append(sysroot, sdk_path, false);
 }
 
 bool Module::MergeArchitecture(const ArchSpec &arch_spec) {
diff --git a/lldb/source/Core/ModuleList.cpp b/lldb/source/Core/ModuleList.cpp
--- a/lldb/source/Core/ModuleList.cpp
+++ b/lldb/source/Core/ModuleList.cpp
@@ -122,8 +122,7 @@
     FileSpec resolved;
     Status status = FileSystem::Instance().Readlink(symlink, resolved);
     if (status.Success())
-      m_symlink_paths.Append(ConstString(symlink.GetPath()),
-                             ConstString(resolved.GetPath()), notify);
+      m_symlink_paths.Append(symlink.GetPath(), resolved.GetPath(), notify);
   }
 }
 
diff --git a/lldb/source/Interpreter/OptionValuePathMappings.cpp b/lldb/source/Interpreter/OptionValuePathMappings.cpp
--- a/lldb/source/Interpreter/OptionValuePathMappings.cpp
+++ b/lldb/source/Interpreter/OptionValuePathMappings.cpp
@@ -62,10 +62,10 @@
           const char *orginal_path = args.GetArgumentAtIndex(i);
           const char *replace_path = args.GetArgumentAtIndex(i + 1);
           if (VerifyPathExists(replace_path)) {
-            ConstString a(orginal_path);
-            ConstString b(replace_path);
-            if (!m_path_mappings.Replace(a, b, idx, m_notify_changes))
-              m_path_mappings.Append(a, b, m_notify_changes);
+            if (!m_path_mappings.Replace(orginal_path, replace_path, idx,
+                                         m_notify_changes))
+              m_path_mappings.Append(orginal_path, replace_path,
+                                     m_notify_changes);
             changed = true;
           } else {
             std::string previousError =
@@ -102,9 +102,7 @@
         const char *orginal_path = args.GetArgumentAtIndex(i);
         const char *replace_path = args.GetArgumentAtIndex(i + 1);
         if (VerifyPathExists(replace_path)) {
-          ConstString a(orginal_path);
-          ConstString b(replace_path);
-          m_path_mappings.Append(a, b, m_notify_changes);
+          m_path_mappings.Append(orginal_path, replace_path, m_notify_changes);
           m_value_was_set = true;
           changed = true;
         } else {
@@ -139,9 +137,8 @@
           const char *orginal_path = args.GetArgumentAtIndex(i);
           const char *replace_path = args.GetArgumentAtIndex(i + 1);
           if (VerifyPathExists(replace_path)) {
-            ConstString a(orginal_path);
-            ConstString b(replace_path);
-            m_path_mappings.Insert(a, b, idx, m_notify_changes);
+            m_path_mappings.Insert(orginal_path, replace_path, idx,
+                                   m_notify_changes);
             changed = true;
             idx++;
           } else {
diff --git a/lldb/source/Target/PathMappingList.cpp b/lldb/source/Target/PathMappingList.cpp
--- a/lldb/source/Target/PathMappingList.cpp
+++ b/lldb/source/Target/PathMappingList.cpp
@@ -30,11 +30,11 @@
   // with the raw path pair, which doesn't work anymore because the paths have
   // been normalized when the debug info was loaded. So we need to store
   // nomalized path pairs to ensure things match up.
-  ConstString NormalizePath(ConstString path) {
-    // If we use "path" to construct a FileSpec, it will normalize the path for
-    // us. We then grab the string and turn it back into a ConstString.
-    return ConstString(FileSpec(path.GetStringRef()).GetPath());
-  }
+std::string NormalizePath(llvm::StringRef path) {
+  // If we use "path" to construct a FileSpec, it will normalize the path for
+  // us. We then grab the string and turn it back into a ConstString.
+  return FileSpec(path).GetPath();
+}
 }
 // PathMappingList constructor
 PathMappingList::PathMappingList() : m_pairs() {}
@@ -59,8 +59,8 @@
 
 PathMappingList::~PathMappingList() = default;
 
-void PathMappingList::Append(ConstString path,
-                             ConstString replacement, bool notify) {
+void PathMappingList::Append(llvm::StringRef path, llvm::StringRef replacement,
+                             bool notify) {
   ++m_mod_id;
   m_pairs.emplace_back(pair(NormalizePath(path), NormalizePath(replacement)));
   if (notify && m_callback)
@@ -78,9 +78,8 @@
   }
 }
 
-void PathMappingList::Insert(ConstString path,
-                             ConstString replacement, uint32_t index,
-                             bool notify) {
+void PathMappingList::Insert(llvm::StringRef path, llvm::StringRef replacement,
+                             uint32_t index, bool notify) {
   ++m_mod_id;
   iterator insert_iter;
   if (index >= m_pairs.size())
@@ -93,9 +92,8 @@
     m_callback(*this, m_callback_baton);
 }
 
-bool PathMappingList::Replace(ConstString path,
-                              ConstString replacement, uint32_t index,
-                              bool notify) {
+bool PathMappingList::Replace(llvm::StringRef path, llvm::StringRef replacement,
+                              uint32_t index, bool notify) {
   if (index >= m_pairs.size())
     return false;
   ++m_mod_id;
@@ -221,20 +219,19 @@
   // We must normalize the orig_spec again using the host's path style,
   // otherwise there will be mismatch between the host and remote platform
   // if they use different path styles.
-  if (auto remapped = RemapPath(
-          NormalizePath(ConstString(orig_spec.GetCString())).GetStringRef(),
-          /*only_if_exists=*/true))
+  if (auto remapped = RemapPath(NormalizePath(orig_spec.GetPath()),
+                                /*only_if_exists=*/true))
     return remapped;
 
   return {};
 }
 
-bool PathMappingList::Replace(ConstString path,
-                              ConstString new_path, bool notify) {
+bool PathMappingList::Replace(llvm::StringRef path, llvm::StringRef new_path,
+                              bool notify) {
   uint32_t idx = FindIndexForPath(path);
   if (idx < m_pairs.size()) {
     ++m_mod_id;
-    m_pairs[idx].second = new_path;
+    m_pairs[idx].second = ConstString(new_path);
     if (notify && m_callback)
       m_callback(*this, m_callback_baton);
     return true;
@@ -290,8 +287,8 @@
   return false;
 }
 
-uint32_t PathMappingList::FindIndexForPath(ConstString orig_path) const {
-  const ConstString path = NormalizePath(orig_path);
+uint32_t PathMappingList::FindIndexForPath(llvm::StringRef orig_path) const {
+  const ConstString path = ConstString(NormalizePath(orig_path));
   const_iterator pos;
   const_iterator begin = m_pairs.begin();
   const_iterator end = m_pairs.end();
diff --git a/lldb/unittests/Target/FindFileTest.cpp b/lldb/unittests/Target/FindFileTest.cpp
--- a/lldb/unittests/Target/FindFileTest.cpp
+++ b/lldb/unittests/Target/FindFileTest.cpp
@@ -75,8 +75,8 @@
   llvm::FileRemover file_remover(FileName);
   PathMappingList map;
 
-  map.Append(ConstString("/old"), ConstString(DirName.str()), false);
-  map.Append(ConstString(R"(C:\foo)"), ConstString(DirName.str()), false);
+  map.Append("/old", DirName.str(), false);
+  map.Append(R"(C:\foo)", DirName.str(), false);
 
   Matches matches[] = {
       {"/old", llvm::sys::path::Style::posix, DirName.c_str()},
diff --git a/lldb/unittests/Target/PathMappingListTest.cpp b/lldb/unittests/Target/PathMappingListTest.cpp
--- a/lldb/unittests/Target/PathMappingListTest.cpp
+++ b/lldb/unittests/Target/PathMappingListTest.cpp
@@ -66,16 +66,16 @@
 #endif
   };
   PathMappingList map;
-  map.Append(ConstString("."), ConstString("/tmp"), false);
+  map.Append(".", "/tmp", false);
   TestPathMappings(map, matches, fails);
   PathMappingList map2;
-  map2.Append(ConstString(""), ConstString("/tmp"), false);
+  map2.Append("", "/tmp", false);
   TestPathMappings(map, matches, fails);
 }
 
 TEST(PathMappingListTest, AbsoluteTests) {
   PathMappingList map;
-  map.Append(ConstString("/old"), ConstString("/new"), false);
+  map.Append("/old", "/new", false);
   Matches matches[] = {
     {"/old", "/new"},
     {"/old/", "/new"},
@@ -97,7 +97,7 @@
 
 TEST(PathMappingListTest, RemapRoot) {
   PathMappingList map;
-  map.Append(ConstString("/"), ConstString("/new"), false);
+  map.Append("/", "/new", false);
   Matches matches[] = {
     {"/old", "/new/old"},
     {"/old/", "/new/old"},
@@ -118,7 +118,7 @@
 #ifndef _WIN32
 TEST(PathMappingListTest, CrossPlatformTests) {
   PathMappingList map;
-  map.Append(ConstString(R"(C:\old)"), ConstString("/new"), false);
+  map.Append(R"(C:\old)", "/new", false);
   Matches matches[] = {
     {R"(C:\old)", llvm::sys::path::Style::windows, "/new"},
     {R"(C:\old\)", llvm::sys::path::Style::windows, "/new"},