diff --git a/src/indexer.cc b/src/indexer.cc
index d77be6f7..34e28744 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -1089,7 +1089,7 @@ public:
     if (IndexFile *db = param.ConsumeFile(*FE)) {
       std::string file_name = FileName(*File);
       if (file_name.size())
-        db->includes.push_back({spell.start.line, std::move(file_name)});
+        db->includes.push_back({spell.start.line, Intern(file_name)});
     }
   }
   void MacroDefined(const Token &Tok, const MacroDirective *MD) override {
@@ -1343,7 +1343,8 @@ Index(CompletionManager *completion, WorkingFiles *wfiles, VFS *vfs,
     // dependency set.
     for (auto &[_, path] : param.SeenUniqueID)
       if (path != entry->path && path != entry->import_file)
-        entry->dependencies[path] = param.file2mtime[path];
+        entry->dependencies[llvm::CachedHashStringRef(Intern(path))] =
+            param.file2mtime[path];
   }
 
   return result;
diff --git a/src/indexer.h b/src/indexer.h
index 2bbce4e0..f919327f 100644
--- a/src/indexer.h
+++ b/src/indexer.h
@@ -15,7 +15,8 @@
 #include "utils.h"
 
 #include <clang/Basic/Specifiers.h>
-#include <llvm/ADT/StringMap.h>
+#include <llvm/ADT/CachedHashString.h>
+#include <llvm/ADT/DenseMap.h>
 
 #include <algorithm>
 #include <optional>
@@ -220,7 +221,7 @@ struct IndexInclude {
   // information - a line is good enough for clicking.
   int line = 0;
   // Absolute path to the index.
-  std::string resolved_path;
+  const char *resolved_path;
 };
 
 struct IndexFile {
@@ -254,7 +255,7 @@ struct IndexFile {
   std::vector<Range> skipped_ranges;
 
   std::vector<IndexInclude> includes;
-  llvm::StringMap<int64_t> dependencies;
+  llvm::DenseMap<llvm::CachedHashStringRef, int64_t> dependencies;
   std::unordered_map<Usr, IndexFunc> usr2func;
   std::unordered_map<Usr, IndexType> usr2type;
   std::unordered_map<Usr, IndexVar> usr2var;
diff --git a/src/pipeline.cc b/src/pipeline.cc
index 8d65886d..45c0f6bd 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -325,7 +325,7 @@ bool Indexer_Parse(CompletionManager *completion, WorkingFiles *wfiles,
       if (entry.id >= 0) {
         std::lock_guard<std::mutex> lock(project->mutex_);
         for (auto &dep : curr->dependencies)
-          project->path_to_entry_index[dep.first()] = entry.id;
+          project->path_to_entry_index[dep.first.val().str()] = entry.id;
       }
     }
   }
diff --git a/src/query.cc b/src/query.cc
index 374c0d15..2db20d11 100644
--- a/src/query.cc
+++ b/src/query.cc
@@ -50,7 +50,7 @@ QueryFile::DefUpdate BuildFileDefUpdate(const IndexFile &indexed) {
   def.skipped_ranges = std::move(indexed.skipped_ranges);
   def.dependencies.reserve(indexed.dependencies.size());
   for (auto &dep : indexed.dependencies)
-    def.dependencies.push_back(dep.first());
+    def.dependencies.push_back(dep.first.val().data()); // llvm 8 -> data()
   def.language = indexed.language;
   return {std::move(def), std::move(indexed.file_contents)};
 }
diff --git a/src/query.h b/src/query.h
index 7241e177..6f844656 100644
--- a/src/query.h
+++ b/src/query.h
@@ -35,7 +35,7 @@ struct QueryFile {
     // Parts of the file which are disabled.
     std::vector<Range> skipped_ranges;
     // Used by |$ccls/reload|.
-    std::vector<std::string> dependencies;
+    std::vector<const char *> dependencies;
   };
 
   using DefUpdate = std::pair<Def, std::string>;
diff --git a/src/serializer.cc b/src/serializer.cc
index c6da2ae0..7061015f 100644
--- a/src/serializer.cc
+++ b/src/serializer.cc
@@ -15,6 +15,7 @@
 #include <mutex>
 #include <stdexcept>
 
+using namespace ccls;
 using namespace llvm;
 
 bool gTestOutputMode = false;
@@ -115,7 +116,7 @@ void Reflect(Writer &visitor, std::string_view &data) {
 
 void Reflect(Reader &vis, const char *&v) {
   const char *str = vis.GetString();
-  v = ccls::Intern(str);
+  v = Intern(str);
 }
 void Reflect(Writer &vis, const char *&v) { vis.String(v); }
 
@@ -148,33 +149,33 @@ void Reflect(Writer &visitor, std::unordered_map<Usr, V> &map) {
 }
 
 // Used by IndexFile::dependencies.
-void Reflect(Reader &vis, StringMap<int64_t> &v) {
+void Reflect(Reader &vis, DenseMap<CachedHashStringRef, int64_t> &v) {
   std::string name;
   if (vis.Format() == SerializeFormat::Json) {
     auto &vis1 = static_cast<JsonReader&>(vis);
     for (auto it = vis1.m().MemberBegin(); it != vis1.m().MemberEnd(); ++it)
-      v[it->name.GetString()] = it->value.GetInt64();
+      v[CachedHashStringRef(Intern(it->name.GetString()))] =
+          it->value.GetInt64();
   } else {
     vis.IterArray([&](Reader &entry) {
       Reflect(entry, name);
-      Reflect(entry, v[name]);
+      Reflect(entry, v[CachedHashStringRef(Intern(name))]);
     });
   }
 }
-void Reflect(Writer &vis, StringMap<int64_t> &v) {
+void Reflect(Writer &vis, DenseMap<CachedHashStringRef, int64_t> &v) {
   if (vis.Format() == SerializeFormat::Json) {
     auto &vis1 = static_cast<JsonWriter&>(vis);
     vis.StartObject();
     for (auto &it : v) {
-      std::string key = it.first();
-      vis1.m().Key(key.c_str());
+      vis1.m().Key(it.first.val().data()); // llvm 8 -> data()
       vis1.m().Int64(it.second);
     }
     vis.EndObject();
   } else {
     vis.StartArray(v.size());
     for (auto &it : v) {
-      std::string key = it.first();
+      std::string key = it.first.val().str();
       Reflect(vis, key);
       Reflect(vis, it.second);
     }
@@ -455,13 +456,16 @@ Deserialize(SerializeFormat format, const std::string &path,
       DoPathMapping(arg);
     for (auto &[_, path] : file->lid2path)
       DoPathMapping(path);
-    for (auto &include : file->includes)
-      DoPathMapping(include.resolved_path);
-    StringMap<int64_t> dependencies;
+    for (auto &include : file->includes) {
+      std::string p(include.resolved_path);
+      DoPathMapping(p);
+      include.resolved_path = Intern(p);
+    }
+    decltype(file->dependencies) dependencies;
     for (auto &it : file->dependencies) {
-      std::string path = it.first().str();
+      std::string path = it.first.val().str();
       DoPathMapping(path);
-      dependencies[path] = it.second;
+      dependencies[CachedHashStringRef(Intern(path))] = it.second;
     }
     file->dependencies = std::move(dependencies);
   }