[clang][deps] Print tracing VFS data

clang/include/clang/Tooling/DependencyScanning/DependencyScanningService.h

@@ -76,7 +76,7 @@ class DependencyScanningService {
   DependencyScanningService(
       ScanningMode Mode, ScanningOutputFormat Format,
       ScanningOptimizations OptimizeArgs = ScanningOptimizations::Default,
-      bool EagerLoadModules = false);
+      bool EagerLoadModules = false, bool TraceVFS = false);
 
   ScanningMode getMode() const { return Mode; }
 
@@ -86,6 +86,8 @@ class DependencyScanningService {
 
   bool shouldEagerLoadModules() const { return EagerLoadModules; }
 
+  bool shouldTraceVFS() const { return TraceVFS; }
+
   DependencyScanningFilesystemSharedCache &getSharedCache() {
     return SharedCache;
   }
@@ -97,6 +99,8 @@ class DependencyScanningService {
   const ScanningOptimizations OptimizeArgs;
   /// Whether to set up command-lines to load PCM files eagerly.
   const bool EagerLoadModules;
+  /// Whether to trace VFS accesses.
+  const bool TraceVFS;
   /// The global file system cache.
   DependencyScanningFilesystemSharedCache SharedCache;
 };

clang/include/clang/Tooling/DependencyScanning/DependencyScanningTool.h

@@ -144,6 +144,8 @@ class DependencyScanningTool {
       StringRef CWD, const llvm::DenseSet<ModuleID> &AlreadySeen,
       LookupModuleOutputCallback LookupModuleOutput);
 
+  llvm::vfs::FileSystem &getWorkerVFS() const { return Worker.getVFS(); }
+
 private:
   DependencyScanningWorker Worker;
 };

clang/include/clang/Tooling/DependencyScanning/DependencyScanningWorker.h

@@ -104,6 +104,8 @@ class DependencyScanningWorker {
 
   bool shouldEagerLoadModules() const { return EagerLoadModules; }
 
+  llvm::vfs::FileSystem &getVFS() const { return *BaseFS; }
+
 private:
   std::shared_ptr<PCHContainerOperations> PCHContainerOps;
   /// The file system to be used during the scan.

clang/lib/Basic/FileManager.cpp

@@ -692,5 +692,16 @@ void FileManager::PrintStats() const {
   llvm::errs() << NumFileLookups << " file lookups, "
                << NumFileCacheMisses << " file cache misses.\n";
 
+  getVirtualFileSystem().visit([](llvm::vfs::FileSystem &VFS) {
+    if (auto *T = dyn_cast_or_null<llvm::vfs::TracingFileSystem>(&VFS))
+      llvm::errs() << "\n*** Virtual File System Stats:\n"
+                   << T->NumStatusCalls << " status() calls\n"
+                   << T->NumOpenFileForReadCalls << " openFileForRead() calls\n"
+                   << T->NumDirBeginCalls << " dir_begin() calls\n"
+                   << T->NumGetRealPathCalls << " getRealPath() calls\n"
+                   << T->NumExistsCalls << " exists() calls\n"
+                   << T->NumIsLocalCalls << " isLocal() calls\n";
+  });
+
   //llvm::errs() << PagesMapped << BytesOfPagesMapped << FSLookups;
 }

clang/lib/Frontend/CompilerInstance.cpp

@@ -381,6 +381,9 @@ FileManager *CompilerInstance::createFileManager(
                   : createVFSFromCompilerInvocation(getInvocation(),
                                                     getDiagnostics());
   assert(VFS && "FileManager has no VFS?");
+  if (getFrontendOpts().ShowStats)
+    VFS =
+        llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(VFS));
   FileMgr = new FileManager(getFileSystemOpts(), std::move(VFS));
   return FileMgr.get();
 }

clang/lib/Tooling/DependencyScanning/DependencyScanningService.cpp

@@ -15,9 +15,9 @@ using namespace dependencies;
 
 DependencyScanningService::DependencyScanningService(
     ScanningMode Mode, ScanningOutputFormat Format,
-    ScanningOptimizations OptimizeArgs, bool EagerLoadModules)
+    ScanningOptimizations OptimizeArgs, bool EagerLoadModules, bool TraceVFS)
     : Mode(Mode), Format(Format), OptimizeArgs(OptimizeArgs),
-      EagerLoadModules(EagerLoadModules) {
+      EagerLoadModules(EagerLoadModules), TraceVFS(TraceVFS) {
   // Initialize targets for object file support.
   llvm::InitializeAllTargets();
   llvm::InitializeAllTargetMCs();

clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp

@@ -501,6 +501,9 @@ DependencyScanningWorker::DependencyScanningWorker(
   // The scanner itself writes only raw ast files.
   PCHContainerOps->registerWriter(std::make_unique<RawPCHContainerWriter>());
 
+  if (Service.shouldTraceVFS())
+    FS = llvm::makeIntrusiveRefCnt<llvm::vfs::TracingFileSystem>(std::move(FS));
+
   switch (Service.getMode()) {
   case ScanningMode::DependencyDirectivesScan:
     DepFS =

clang/test/ClangScanDeps/verbose.test

@@ -0,0 +1,28 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb.json.in > %t/cdb.json
+
+// RUN: clang-scan-deps -compilation-database %t/cdb.json -v -o %t/result.json 2>&1 | FileCheck %s
+// CHECK:      *** Virtual File System Stats:
+// CHECK-NEXT: {{[[:digit:]]+}} status() calls
+// CHECK-NEXT: {{[[:digit:]]+}} openFileForRead() calls
+// CHECK-NEXT: {{[[:digit:]]+}} dir_begin() calls
+// CHECK-NEXT: {{[[:digit:]]+}} getRealPath() calls
+// CHECK-NEXT: {{[[:digit:]]+}} exists() calls
+// CHECK-NEXT: {{[[:digit:]]+}} isLocal() calls
+
+//--- tu.c
+
+//--- cdb.json.in
+[
+  {
+    "file": "DIR/tu.c"
+    "directory": "DIR",
+    "command": "clang -c DIR/tu.c -o DIR/tu.o"
+  },
+  {
+    "file": "DIR/tu.c"
+    "directory": "DIR",
+    "command": "clang -c DIR/tu.c -o DIR/tu.o"
+  }
+]

clang/test/Misc/print-stats-vfs.test

@@ -0,0 +1,17 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+// RUN: %clang_cc1 -fsyntax-only %t/tu.c -I %t/dir1 -I %t/dir2 -print-stats 2>&1 | FileCheck %s
+
+//--- tu.c
+#include "header.h"
+//--- dir1/other.h
+//--- dir2/header.h
+
+// CHECK:      *** Virtual File System Stats:
+// CHECK-NEXT: {{[[:digit:]]+}} status() calls
+// CHECK-NEXT: {{[[:digit:]]+}} openFileForRead() calls
+// CHECK-NEXT: {{[[:digit:]]+}} dir_begin() calls
+// CHECK-NEXT: {{[[:digit:]]+}} getRealPath() calls
+// CHECK-NEXT: {{[[:digit:]]+}} exists() calls
+// CHECK-NEXT: {{[[:digit:]]+}} isLocal() calls

clang/tools/clang-scan-deps/ClangScanDeps.cpp

@@ -915,6 +915,13 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
   if (Format == ScanningOutputFormat::Full)
     FD.emplace(ModuleName.empty() ? Inputs.size() : 0);
 
+  std::atomic<size_t> NumStatusCalls = 0;
+  std::atomic<size_t> NumOpenFileForReadCalls = 0;
+  std::atomic<size_t> NumDirBeginCalls = 0;
+  std::atomic<size_t> NumGetRealPathCalls = 0;
+  std::atomic<size_t> NumExistsCalls = 0;
+  std::atomic<size_t> NumIsLocalCalls = 0;
+
   auto ScanningTask = [&](DependencyScanningService &Service) {
     DependencyScanningTool WorkerTool(Service);
 
@@ -999,10 +1006,21 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
           HadErrors = true;
       }
     }
+
+    WorkerTool.getWorkerVFS().visit([&](llvm::vfs::FileSystem &VFS) {
+      if (auto *T = dyn_cast_or_null<llvm::vfs::TracingFileSystem>(&VFS)) {
+        NumStatusCalls += T->NumStatusCalls;
+        NumOpenFileForReadCalls += T->NumOpenFileForReadCalls;
+        NumDirBeginCalls += T->NumDirBeginCalls;
+        NumGetRealPathCalls += T->NumGetRealPathCalls;
+        NumExistsCalls += T->NumExistsCalls;
+        NumIsLocalCalls += T->NumIsLocalCalls;
+      }
+    });
   };
 
   DependencyScanningService Service(ScanMode, Format, OptimizeArgs,
-                                    EagerLoadModules);
+                                    EagerLoadModules, /*TraceVFS=*/Verbose);
 
   llvm::Timer T;
   T.startTimer();
@@ -1025,6 +1043,16 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
   }
 
   T.stopTimer();
+
+  if (Verbose)
+    llvm::errs() << "\n*** Virtual File System Stats:\n"
+                 << NumStatusCalls << " status() calls\n"
+                 << NumOpenFileForReadCalls << " openFileForRead() calls\n"
+                 << NumDirBeginCalls << " dir_begin() calls\n"
+                 << NumGetRealPathCalls << " getRealPath() calls\n"
+                 << NumExistsCalls << " exists() calls\n"
+                 << NumIsLocalCalls << " isLocal() calls\n";
+
   if (PrintTiming)
     llvm::errs() << llvm::format(
         "clang-scan-deps timing: %0.2fs wall, %0.2fs process\n",