Index: clang-tools-extra/trunk/clangd/index/SymbolYAML.h
===================================================================
--- clang-tools-extra/trunk/clangd/index/SymbolYAML.h
+++ clang-tools-extra/trunk/clangd/index/SymbolYAML.h
@@ -41,6 +41,12 @@
 // The YAML result is safe to concatenate if you have multiple symbol slabs.
 void SymbolsToYAML(const SymbolSlab &Symbols, llvm::raw_ostream &OS);
 
+// Build an in-memory static index for global symbols from a symbol file.
+// The size of global symbols should be relatively small, so that all symbols
+// can be managed in memory.
+std::unique_ptr<SymbolIndex> loadIndex(llvm::StringRef SymbolFile,
+                                       bool UseDex = true);
+
 } // namespace clangd
 } // namespace clang
 
Index: clang-tools-extra/trunk/clangd/index/SymbolYAML.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/index/SymbolYAML.cpp
+++ clang-tools-extra/trunk/clangd/index/SymbolYAML.cpp
@@ -9,6 +9,7 @@
 
 #include "SymbolYAML.h"
 #include "Index.h"
+#include "dex/DexIndex.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Errc.h"
@@ -25,18 +26,18 @@
 using clang::clangd::SymbolID;
 using clang::clangd::SymbolLocation;
 using clang::index::SymbolInfo;
-using clang::index::SymbolLanguage;
 using clang::index::SymbolKind;
+using clang::index::SymbolLanguage;
 
 // Helper to (de)serialize the SymbolID. We serialize it as a hex string.
 struct NormalizedSymbolID {
   NormalizedSymbolID(IO &) {}
-  NormalizedSymbolID(IO &, const SymbolID& ID) {
+  NormalizedSymbolID(IO &, const SymbolID &ID) {
     llvm::raw_string_ostream OS(HexString);
     OS << ID;
   }
 
-  SymbolID denormalize(IO&) {
+  SymbolID denormalize(IO &) {
     SymbolID ID;
     HexString >> ID;
     return ID;
@@ -167,7 +168,7 @@
   return S;
 }
 
-void SymbolsToYAML(const SymbolSlab& Symbols, llvm::raw_ostream &OS) {
+void SymbolsToYAML(const SymbolSlab &Symbols, llvm::raw_ostream &OS) {
   llvm::yaml::Output Yout(OS);
   for (Symbol S : Symbols) // copy: Yout<< requires mutability.
     Yout << S;
@@ -181,5 +182,18 @@
   return OS.str();
 }
 
+std::unique_ptr<SymbolIndex> loadIndex(llvm::StringRef SymbolFile,
+                                       bool UseDex) {
+  auto Buffer = llvm::MemoryBuffer::getFile(SymbolFile);
+  if (!Buffer) {
+    llvm::errs() << "Can't open " << SymbolFile << "\n";
+    return nullptr;
+  }
+  auto Slab = symbolsFromYAML(Buffer.get()->getBuffer());
+
+  return UseDex ? dex::DexIndex::build(std::move(Slab))
+                : MemIndex::build(std::move(Slab), RefSlab());
+}
+
 } // namespace clangd
 } // namespace clang
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
@@ -39,24 +39,6 @@
 
 enum class PCHStorageFlag { Disk, Memory };
 
-// Build an in-memory static index for global symbols from a YAML-format file.
-// The size of global symbols should be relatively small, so that all symbols
-// can be managed in memory.
-std::unique_ptr<SymbolIndex> buildStaticIndex(llvm::StringRef YamlSymbolFile) {
-  auto Buffer = llvm::MemoryBuffer::getFile(YamlSymbolFile);
-  if (!Buffer) {
-    llvm::errs() << "Can't open " << YamlSymbolFile << "\n";
-    return nullptr;
-  }
-  auto Slab = symbolsFromYAML(Buffer.get()->getBuffer());
-  SymbolSlab::Builder SymsBuilder;
-  for (auto Sym : Slab)
-    SymsBuilder.insert(Sym);
-
-  return UseDex ? dex::DexIndex::build(std::move(SymsBuilder).build())
-                : MemIndex::build(std::move(SymsBuilder).build(), RefSlab());
-}
-
 } // namespace
 
 static llvm::cl::opt<Path> CompileCommandsDir(
@@ -298,7 +280,7 @@
   Opts.BuildDynamicSymbolIndex = EnableIndex;
   std::unique_ptr<SymbolIndex> StaticIdx;
   if (EnableIndex && !YamlSymbolFile.empty()) {
-    StaticIdx = buildStaticIndex(YamlSymbolFile);
+    StaticIdx = loadIndex(YamlSymbolFile, UseDex);
     Opts.StaticIndex = StaticIdx.get();
   }
   Opts.AsyncThreadsCount = WorkerThreadsCount;