[clang-scan-deps] reuse the file manager across invocations of

the dependency scanner on a single worker thread

This behavior can be controlled using the new `-reuse-filemanager` clang-scan-deps
option. By default the file manager is reused.

The added test/ClangScanDeps/symlink.cpp is able to pass with
the reused filemanager after the related FileEntryRef changes
landed earlier. The test test/ClangScanDeps/subframework_header_dir_symlink.m
still fails when the file manager is reused (I run the FileCheck with not to
make it PASS). I will address this in a follow-up patch that improves
the DirectoryEntry name modelling in the FileManager.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@370420 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 12 insertions, 5 deletions

diff --git a/lib/Tooling/DependencyScanning/DependencyScanningService.cpp b/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
index 48aa68218c..6ddce0dcee 100644
--- a/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
+++ b/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
@@ -12,5 +12,6 @@ using namespace clang;
 using namespace tooling;
 using namespace dependencies;
 
-DependencyScanningService::DependencyScanningService(ScanningMode Mode)
-    : Mode(Mode) {}
+DependencyScanningService::DependencyScanningService(ScanningMode Mode,
+                                                     bool ReuseFileManager)
+    : Mode(Mode), ReuseFileManager(ReuseFileManager) {}
diff --git a/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
index c80a55645e..2d49e0d794 100644
--- a/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -148,6 +148,8 @@ DependencyScanningWorker::DependencyScanningWorker(
   if (Service.getMode() == ScanningMode::MinimizedSourcePreprocessing)
     DepFS = new DependencyScanningWorkerFilesystem(Service.getSharedCache(),
                                                    RealFS);
+  if (Service.canReuseFileManager())
+    Files = new FileManager(FileSystemOptions(), RealFS);
 }
 
 llvm::Expected<std::string>
@@ -164,7 +166,7 @@ DependencyScanningWorker::getDependencyFile(const std::string &Input,
   /// Create the tool that uses the underlying file system to ensure that any
   /// file system requests that are made by the driver do not go through the
   /// dependency scanning filesystem.
-  tooling::ClangTool Tool(CDB, Input, PCHContainerOps, RealFS);
+  tooling::ClangTool Tool(CDB, Input, PCHContainerOps, RealFS, Files);
   Tool.clearArgumentsAdjusters();
   Tool.setRestoreWorkingDir(false);
   Tool.setPrintErrorMessage(false);
diff --git a/lib/Tooling/Tooling.cpp b/lib/Tooling/Tooling.cpp
index 8c0d13d243..472a3ab57c 100644
--- a/lib/Tooling/Tooling.cpp
+++ b/lib/Tooling/Tooling.cpp
@@ -378,16 +378,20 @@ bool FrontendActionFactory::runInvocation(
 ClangTool::ClangTool(const CompilationDatabase &Compilations,
                      ArrayRef<std::string> SourcePaths,
                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
-                     IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS)
+                     IntrusiveRefCntPtr<llvm::vfs::FileSystem> BaseFS,
+                     IntrusiveRefCntPtr<FileManager> Files)
     : Compilations(Compilations), SourcePaths(SourcePaths),
       PCHContainerOps(std::move(PCHContainerOps)),
       OverlayFileSystem(new llvm::vfs::OverlayFileSystem(std::move(BaseFS))),
       InMemoryFileSystem(new llvm::vfs::InMemoryFileSystem),
-      Files(new FileManager(FileSystemOptions(), OverlayFileSystem)) {
+      Files(Files ? Files
+                  : new FileManager(FileSystemOptions(), OverlayFileSystem)) {
   OverlayFileSystem->pushOverlay(InMemoryFileSystem);
   appendArgumentsAdjuster(getClangStripOutputAdjuster());
   appendArgumentsAdjuster(getClangSyntaxOnlyAdjuster());
   appendArgumentsAdjuster(getClangStripDependencyFileAdjuster());
+  if (Files)
+    Files->setVirtualFileSystem(OverlayFileSystem);
 }
 
 ClangTool::~ClangTool() = default;