1 files changed, 17 insertions, 9 deletions

diff --git a/clang-tools-extra/clangd/ClangdUnit.cpp b/clang-tools-extra/clangd/ClangdUnit.cpp
index 6c184ff06b0..2ad6dc69cc8 100644
--- a/clang-tools-extra/clangd/ClangdUnit.cpp
+++ b/clang-tools-extra/clangd/ClangdUnit.cpp
@@ -246,9 +246,10 @@ const IncludeStructure &ParsedAST::getIncludeStructure() const {
 }
 
 PreambleData::PreambleData(PrecompiledPreamble Preamble,
-                           std::vector<Diag> Diags, IncludeStructure Includes)
+                           std::vector<Diag> Diags, IncludeStructure Includes,
+                           std::unique_ptr<PreambleFileStatusCache> StatCache)
     : Preamble(std::move(Preamble)), Diags(std::move(Diags)),
-      Includes(std::move(Includes)) {}
+      Includes(std::move(Includes)), StatCache(std::move(StatCache)) {}
 
 ParsedAST::ParsedAST(std::shared_ptr<const PreambleData> Preamble,
                      std::unique_ptr<CompilerInstance> Clang,
@@ -334,9 +335,12 @@ std::shared_ptr<const PreambleData> clangd::buildPreamble(
     // We proceed anyway, our lit-tests rely on results for non-existing working
     // dirs.
   }
+
+  auto StatCache = llvm::make_unique<PreambleFileStatusCache>();
   auto BuiltPreamble = PrecompiledPreamble::Build(
-      CI, ContentsBuffer.get(), Bounds, *PreambleDiagsEngine, Inputs.FS, PCHs,
-      StoreInMemory, SerializedDeclsCollector);
+      CI, ContentsBuffer.get(), Bounds, *PreambleDiagsEngine,
+      StatCache->getProducingFS(Inputs.FS), PCHs, StoreInMemory,
+      SerializedDeclsCollector);
 
   // When building the AST for the main file, we do want the function
   // bodies.
@@ -347,7 +351,7 @@ std::shared_ptr<const PreambleData> clangd::buildPreamble(
          FileName);
     return std::make_shared<PreambleData>(
         std::move(*BuiltPreamble), PreambleDiagnostics.take(),
-        SerializedDeclsCollector.takeIncludes());
+        SerializedDeclsCollector.takeIncludes(), std::move(StatCache));
   } else {
     elog("Could not build a preamble for file {0}", FileName);
     return nullptr;
@@ -361,15 +365,19 @@ llvm::Optional<ParsedAST> clangd::buildAST(
   trace::Span Tracer("BuildAST");
   SPAN_ATTACH(Tracer, "File", FileName);
 
-  if (Inputs.FS->setCurrentWorkingDirectory(Inputs.CompileCommand.Directory)) {
+  auto VFS = Inputs.FS;
+  if (Preamble && Preamble->StatCache)
+    VFS = Preamble->StatCache->getConsumingFS(std::move(VFS));
+  if (VFS->setCurrentWorkingDirectory(Inputs.CompileCommand.Directory)) {
     log("Couldn't set working directory when building the preamble.");
     // We proceed anyway, our lit-tests rely on results for non-existing working
     // dirs.
   }
 
-  return ParsedAST::build(
-      llvm::make_unique<CompilerInvocation>(*Invocation), Preamble,
-      llvm::MemoryBuffer::getMemBufferCopy(Inputs.Contents), PCHs, Inputs.FS);
+  return ParsedAST::build(llvm::make_unique<CompilerInvocation>(*Invocation),
+                          Preamble,
+                          llvm::MemoryBuffer::getMemBufferCopy(Inputs.Contents),
+                          PCHs, std::move(VFS));
 }
 
 SourceLocation clangd::getBeginningOfIdentifier(ParsedAST &Unit,