Index: clang-tools-extra/trunk/clangd/index/MemIndex.h
===================================================================
--- clang-tools-extra/trunk/clangd/index/MemIndex.h
+++ clang-tools-extra/trunk/clangd/index/MemIndex.h
@@ -47,6 +47,11 @@
   mutable std::mutex Mutex;
 };
 
+// Returns pointers to the symbols in given slab and bundles slab lifetime with
+// returned symbol pointers so that the pointers are never invalid.
+std::shared_ptr<std::vector<const Symbol *>>
+getSymbolsFromSlab(SymbolSlab Slab);
+
 } // namespace clangd
 } // namespace clang
 
Index: clang-tools-extra/trunk/clangd/index/MemIndex.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/index/MemIndex.cpp
+++ clang-tools-extra/trunk/clangd/index/MemIndex.cpp
@@ -28,6 +28,12 @@
   }
 }
 
+std::unique_ptr<SymbolIndex> MemIndex::build(SymbolSlab Slab) {
+  auto Idx = llvm::make_unique<MemIndex>();
+  Idx->build(getSymbolsFromSlab(std::move(Slab)));
+  return std::move(Idx);
+}
+
 bool MemIndex::fuzzyFind(
     const FuzzyFindRequest &Req,
     llvm::function_ref<void(const Symbol &)> Callback) const {
@@ -72,7 +78,14 @@
   }
 }
 
-std::unique_ptr<SymbolIndex> MemIndex::build(SymbolSlab Slab) {
+void MemIndex::findOccurrences(
+    const OccurrencesRequest &Req,
+    llvm::function_ref<void(const SymbolOccurrence &)> Callback) const {
+  log("findOccurrences is not implemented.");
+}
+
+std::shared_ptr<std::vector<const Symbol *>>
+getSymbolsFromSlab(SymbolSlab Slab) {
   struct Snapshot {
     SymbolSlab Slab;
     std::vector<const Symbol *> Pointers;
@@ -81,17 +94,8 @@
   Snap->Slab = std::move(Slab);
   for (auto &Sym : Snap->Slab)
     Snap->Pointers.push_back(&Sym);
-  auto S = std::shared_ptr<std::vector<const Symbol *>>(std::move(Snap),
-                                                        &Snap->Pointers);
-  auto MemIdx = llvm::make_unique<MemIndex>();
-  MemIdx->build(std::move(S));
-  return std::move(MemIdx);
-}
-
-void MemIndex::findOccurrences(
-    const OccurrencesRequest &Req,
-    llvm::function_ref<void(const SymbolOccurrence &)> Callback) const {
-  log("findOccurrences is not implemented.");
+  return std::shared_ptr<std::vector<const Symbol *>>(std::move(Snap),
+                                                      &Snap->Pointers);
 }
 
 } // namespace clangd
Index: clang-tools-extra/trunk/clangd/index/dex/DexIndex.h
===================================================================
--- clang-tools-extra/trunk/clangd/index/dex/DexIndex.h
+++ clang-tools-extra/trunk/clangd/index/dex/DexIndex.h
@@ -43,6 +43,9 @@
   /// accessible as long as `Symbols` is kept alive.
   void build(std::shared_ptr<std::vector<const Symbol *>> Symbols);
 
+  /// \brief Build index from a symbol slab.
+  static std::unique_ptr<SymbolIndex> build(SymbolSlab Slab);
+
   bool
   fuzzyFind(const FuzzyFindRequest &Req,
             llvm::function_ref<void(const Symbol &)> Callback) const override;
Index: clang-tools-extra/trunk/clangd/index/dex/DexIndex.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/index/dex/DexIndex.cpp
+++ clang-tools-extra/trunk/clangd/index/dex/DexIndex.cpp
@@ -69,6 +69,12 @@
   }
 }
 
+std::unique_ptr<SymbolIndex> DexIndex::build(SymbolSlab Slab) {
+  auto Idx = llvm::make_unique<MemIndex>();
+  Idx->build(getSymbolsFromSlab(std::move(Slab)));
+  return std::move(Idx);
+}
+
 /// Constructs iterators over tokens extracted from the query and exhausts it
 /// while applying Callback to each symbol in the order of decreasing quality
 /// of the matched symbols.
Index: clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp
+++ clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp
@@ -12,6 +12,7 @@
 #include "Path.h"
 #include "Trace.h"
 #include "index/SymbolYAML.h"
+#include "index/dex/DexIndex.h"
 #include "clang/Basic/Version.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"
@@ -29,6 +30,7 @@
 using namespace clang::clangd;
 
 namespace {
+
 enum class PCHStorageFlag { Disk, Memory };
 
 // Build an in-memory static index for global symbols from a YAML-format file.
@@ -45,8 +47,10 @@
   for (auto Sym : Slab)
     SymsBuilder.insert(Sym);
 
-  return MemIndex::build(std::move(SymsBuilder).build());
+  return UseDex ? DexIndex::build(std::move(SymsBuilder).build())
+                : MemIndex::build(std::move(SymsBuilder).build());
 }
+
 } // namespace
 
 static llvm::cl::opt<Path> CompileCommandsDir(
@@ -185,6 +189,11 @@
                                 "'compile_commands.json' files")),
     llvm::cl::init(FilesystemCompileArgs), llvm::cl::Hidden);
 
+static llvm::cl::opt<bool>
+    UseDex("use-dex-index",
+           llvm::cl::desc("Use experimental Dex static index."),
+           llvm::cl::init(false), llvm::cl::Hidden);
+
 int main(int argc, char *argv[]) {
   llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);
   llvm::cl::SetVersionPrinter([](llvm::raw_ostream &OS) {