[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.

llvm-svn: 370420

1 files changed, 3 insertions, 2 deletions

diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
index 48aa68218c3..6ddce0dcee8 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp
+++ b/clang/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) {}