Import LLVM 10.0.0 release including clang, lld and lldb.

ok hackroom
tested by plenty

1 files changed, 594 insertions, 0 deletions

diff --git a/gnu/llvm/clang/lib/Basic/FileManager.cpp b/gnu/llvm/clang/lib/Basic/FileManager.cpp
new file mode 100644
index 00000000000..079a4bbfc82
--- /dev/null
+++ b/gnu/llvm/clang/lib/Basic/FileManager.cpp
@@ -0,0 +1,594 @@
+//===--- FileManager.cpp - File System Probing and Caching ----------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the FileManager interface.
+//
+//===----------------------------------------------------------------------===//
+//
+// TODO: This should index all interesting directories with dirent calls.
+//  getdirentries ?
+//  opendir/readdir_r/closedir ?
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Basic/FileManager.h"
+#include "clang/Basic/FileSystemStatCache.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <climits>
+#include <cstdint>
+#include <cstdlib>
+#include <string>
+#include <utility>
+
+using namespace clang;
+
+#define DEBUG_TYPE "file-search"
+
+ALWAYS_ENABLED_STATISTIC(NumDirLookups, "Number of directory lookups.");
+ALWAYS_ENABLED_STATISTIC(NumFileLookups, "Number of file lookups.");
+ALWAYS_ENABLED_STATISTIC(NumDirCacheMisses,
+                         "Number of directory cache misses.");
+ALWAYS_ENABLED_STATISTIC(NumFileCacheMisses, "Number of file cache misses.");
+
+//===----------------------------------------------------------------------===//
+// Common logic.
+//===----------------------------------------------------------------------===//
+
+FileManager::FileManager(const FileSystemOptions &FSO,
+                         IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS)
+    : FS(std::move(FS)), FileSystemOpts(FSO), SeenDirEntries(64),
+      SeenFileEntries(64), NextFileUID(0) {
+  // If the caller doesn't provide a virtual file system, just grab the real
+  // file system.
+  if (!this->FS)
+    this->FS = llvm::vfs::getRealFileSystem();
+}
+
+FileManager::~FileManager() = default;
+
+void FileManager::setStatCache(std::unique_ptr<FileSystemStatCache> statCache) {
+  assert(statCache && "No stat cache provided?");
+  StatCache = std::move(statCache);
+}
+
+void FileManager::clearStatCache() { StatCache.reset(); }
+
+/// Retrieve the directory that the given file name resides in.
+/// Filename can point to either a real file or a virtual file.
+static llvm::ErrorOr<const DirectoryEntry *>
+getDirectoryFromFile(FileManager &FileMgr, StringRef Filename,
+                     bool CacheFailure) {
+  if (Filename.empty())
+    return std::errc::no_such_file_or_directory;
+
+  if (llvm::sys::path::is_separator(Filename[Filename.size() - 1]))
+    return std::errc::is_a_directory;
+
+  StringRef DirName = llvm::sys::path::parent_path(Filename);
+  // Use the current directory if file has no path component.
+  if (DirName.empty())
+    DirName = ".";
+
+  return FileMgr.getDirectory(DirName, CacheFailure);
+}
+
+/// Add all ancestors of the given path (pointing to either a file or
+/// a directory) as virtual directories.
+void FileManager::addAncestorsAsVirtualDirs(StringRef Path) {
+  StringRef DirName = llvm::sys::path::parent_path(Path);
+  if (DirName.empty())
+    DirName = ".";
+
+  auto &NamedDirEnt = *SeenDirEntries.insert(
+        {DirName, std::errc::no_such_file_or_directory}).first;
+
+  // When caching a virtual directory, we always cache its ancestors
+  // at the same time.  Therefore, if DirName is already in the cache,
+  // we don't need to recurse as its ancestors must also already be in
+  // the cache (or it's a known non-virtual directory).
+  if (NamedDirEnt.second)
+    return;
+
+  // Add the virtual directory to the cache.
+  auto UDE = std::make_unique<DirectoryEntry>();
+  UDE->Name = NamedDirEnt.first();
+  NamedDirEnt.second = *UDE.get();
+  VirtualDirectoryEntries.push_back(std::move(UDE));
+
+  // Recursively add the other ancestors.
+  addAncestorsAsVirtualDirs(DirName);
+}
+
+llvm::Expected<DirectoryEntryRef>
+FileManager::getDirectoryRef(StringRef DirName, bool CacheFailure) {
+  // stat doesn't like trailing separators except for root directory.
+  // At least, on Win32 MSVCRT, stat() cannot strip trailing '/'.
+  // (though it can strip '\\')
+  if (DirName.size() > 1 &&
+      DirName != llvm::sys::path::root_path(DirName) &&
+      llvm::sys::path::is_separator(DirName.back()))
+    DirName = DirName.substr(0, DirName.size()-1);
+#ifdef _WIN32
+  // Fixing a problem with "clang C:test.c" on Windows.
+  // Stat("C:") does not recognize "C:" as a valid directory
+  std::string DirNameStr;
+  if (DirName.size() > 1 && DirName.back() == ':' &&
+      DirName.equals_lower(llvm::sys::path::root_name(DirName))) {
+    DirNameStr = DirName.str() + '.';
+    DirName = DirNameStr;
+  }
+#endif
+
+  ++NumDirLookups;
+
+  // See if there was already an entry in the map.  Note that the map
+  // contains both virtual and real directories.
+  auto SeenDirInsertResult =
+      SeenDirEntries.insert({DirName, std::errc::no_such_file_or_directory});
+  if (!SeenDirInsertResult.second) {
+    if (SeenDirInsertResult.first->second)
+      return DirectoryEntryRef(&*SeenDirInsertResult.first);
+    return llvm::errorCodeToError(SeenDirInsertResult.first->second.getError());
+  }
+
+  // We've not seen this before. Fill it in.
+  ++NumDirCacheMisses;
+  auto &NamedDirEnt = *SeenDirInsertResult.first;
+  assert(!NamedDirEnt.second && "should be newly-created");
+
+  // Get the null-terminated directory name as stored as the key of the
+  // SeenDirEntries map.
+  StringRef InterndDirName = NamedDirEnt.first();
+
+  // Check to see if the directory exists.
+  llvm::vfs::Status Status;
+  auto statError = getStatValue(InterndDirName, Status, false,
+                                nullptr /*directory lookup*/);
+  if (statError) {
+    // There's no real directory at the given path.
+    if (CacheFailure)
+      NamedDirEnt.second = statError;
+    else
+      SeenDirEntries.erase(DirName);
+    return llvm::errorCodeToError(statError);
+  }
+
+  // It exists.  See if we have already opened a directory with the
+  // same inode (this occurs on Unix-like systems when one dir is
+  // symlinked to another, for example) or the same path (on
+  // Windows).
+  DirectoryEntry &UDE = UniqueRealDirs[Status.getUniqueID()];
+
+  NamedDirEnt.second = UDE;
+  if (UDE.getName().empty()) {
+    // We don't have this directory yet, add it.  We use the string
+    // key from the SeenDirEntries map as the string.
+    UDE.Name  = InterndDirName;
+  }
+
+  return DirectoryEntryRef(&NamedDirEnt);
+}
+
+llvm::ErrorOr<const DirectoryEntry *>
+FileManager::getDirectory(StringRef DirName, bool CacheFailure) {
+  auto Result = getDirectoryRef(DirName, CacheFailure);
+  if (Result)
+    return &Result->getDirEntry();
+  return llvm::errorToErrorCode(Result.takeError());
+}
+
+llvm::ErrorOr<const FileEntry *>
+FileManager::getFile(StringRef Filename, bool openFile, bool CacheFailure) {
+  auto Result = getFileRef(Filename, openFile, CacheFailure);
+  if (Result)
+    return &Result->getFileEntry();
+  return llvm::errorToErrorCode(Result.takeError());
+}
+
+llvm::Expected<FileEntryRef>
+FileManager::getFileRef(StringRef Filename, bool openFile, bool CacheFailure) {
+  ++NumFileLookups;
+
+  // See if there is already an entry in the map.
+  auto SeenFileInsertResult =
+      SeenFileEntries.insert({Filename, std::errc::no_such_file_or_directory});
+  if (!SeenFileInsertResult.second) {
+    if (!SeenFileInsertResult.first->second)
+      return llvm::errorCodeToError(
+          SeenFileInsertResult.first->second.getError());
+    // Construct and return and FileEntryRef, unless it's a redirect to another
+    // filename.
+    SeenFileEntryOrRedirect Value = *SeenFileInsertResult.first->second;
+    FileEntry *FE;
+    if (LLVM_LIKELY(FE = Value.dyn_cast<FileEntry *>()))
+      return FileEntryRef(SeenFileInsertResult.first->first(), *FE);
+    return getFileRef(*Value.get<const StringRef *>(), openFile, CacheFailure);
+  }
+
+  // We've not seen this before. Fill it in.
+  ++NumFileCacheMisses;
+  auto *NamedFileEnt = &*SeenFileInsertResult.first;
+  assert(!NamedFileEnt->second && "should be newly-created");
+
+  // Get the null-terminated file name as stored as the key of the
+  // SeenFileEntries map.
+  StringRef InterndFileName = NamedFileEnt->first();
+
+  // Look up the directory for the file.  When looking up something like
+  // sys/foo.h we'll discover all of the search directories that have a 'sys'
+  // subdirectory.  This will let us avoid having to waste time on known-to-fail
+  // searches when we go to find sys/bar.h, because all the search directories
+  // without a 'sys' subdir will get a cached failure result.
+  auto DirInfoOrErr = getDirectoryFromFile(*this, Filename, CacheFailure);
+  if (!DirInfoOrErr) { // Directory doesn't exist, file can't exist.
+    if (CacheFailure)
+      NamedFileEnt->second = DirInfoOrErr.getError();
+    else
+      SeenFileEntries.erase(Filename);
+
+    return llvm::errorCodeToError(DirInfoOrErr.getError());
+  }
+  const DirectoryEntry *DirInfo = *DirInfoOrErr;
+
+  // FIXME: Use the directory info to prune this, before doing the stat syscall.
+  // FIXME: This will reduce the # syscalls.
+
+  // Check to see if the file exists.
+  std::unique_ptr<llvm::vfs::File> F;
+  llvm::vfs::Status Status;
+  auto statError = getStatValue(InterndFileName, Status, true,
+                                openFile ? &F : nullptr);
+  if (statError) {
+    // There's no real file at the given path.
+    if (CacheFailure)
+      NamedFileEnt->second = statError;
+    else
+      SeenFileEntries.erase(Filename);
+
+    return llvm::errorCodeToError(statError);
+  }
+
+  assert((openFile || !F) && "undesired open file");
+
+  // It exists.  See if we have already opened a file with the same inode.
+  // This occurs when one dir is symlinked to another, for example.
+  FileEntry &UFE = UniqueRealFiles[Status.getUniqueID()];
+
+  NamedFileEnt->second = &UFE;
+
+  // If the name returned by getStatValue is different than Filename, re-intern
+  // the name.
+  if (Status.getName() != Filename) {
+    auto &NewNamedFileEnt =
+        *SeenFileEntries.insert({Status.getName(), &UFE}).first;
+    assert((*NewNamedFileEnt.second).get<FileEntry *>() == &UFE &&
+           "filename from getStatValue() refers to wrong file");
+    InterndFileName = NewNamedFileEnt.first().data();
+    // In addition to re-interning the name, construct a redirecting seen file
+    // entry, that will point to the name the filesystem actually wants to use.
+    StringRef *Redirect = new (CanonicalNameStorage) StringRef(InterndFileName);
+    auto SeenFileInsertResultIt = SeenFileEntries.find(Filename);
+    assert(SeenFileInsertResultIt != SeenFileEntries.end() &&
+           "unexpected SeenFileEntries cache miss");
+    SeenFileInsertResultIt->second = Redirect;
+    NamedFileEnt = &*SeenFileInsertResultIt;
+  }
+
+  if (UFE.isValid()) { // Already have an entry with this inode, return it.
+
+    // FIXME: this hack ensures that if we look up a file by a virtual path in
+    // the VFS that the getDir() will have the virtual path, even if we found
+    // the file by a 'real' path first. This is required in order to find a
+    // module's structure when its headers/module map are mapped in the VFS.
+    // We should remove this as soon as we can properly support a file having
+    // multiple names.
+    if (DirInfo != UFE.Dir && Status.IsVFSMapped)
+      UFE.Dir = DirInfo;
+
+    // Always update the name to use the last name by which a file was accessed.
+    // FIXME: Neither this nor always using the first name is correct; we want
+    // to switch towards a design where we return a FileName object that
+    // encapsulates both the name by which the file was accessed and the
+    // corresponding FileEntry.
+    // FIXME: The Name should be removed from FileEntry once all clients
+    // adopt FileEntryRef.
+    UFE.Name = InterndFileName;
+
+    return FileEntryRef(InterndFileName, UFE);
+  }
+
+  // Otherwise, we don't have this file yet, add it.
+  UFE.Name    = InterndFileName;
+  UFE.Size    = Status.getSize();
+  UFE.ModTime = llvm::sys::toTimeT(Status.getLastModificationTime());
+  UFE.Dir     = DirInfo;
+  UFE.UID     = NextFileUID++;
+  UFE.UniqueID = Status.getUniqueID();
+  UFE.IsNamedPipe = Status.getType() == llvm::sys::fs::file_type::fifo_file;
+  UFE.File = std::move(F);
+  UFE.IsValid = true;
+
+  if (UFE.File) {
+    if (auto PathName = UFE.File->getName())
+      fillRealPathName(&UFE, *PathName);
+  } else if (!openFile) {
+    // We should still fill the path even if we aren't opening the file.
+    fillRealPathName(&UFE, InterndFileName);
+  }
+  return FileEntryRef(InterndFileName, UFE);
+}
+
+const FileEntry *
+FileManager::getVirtualFile(StringRef Filename, off_t Size,
+                            time_t ModificationTime) {
+  ++NumFileLookups;
+
+  // See if there is already an entry in the map for an existing file.
+  auto &NamedFileEnt = *SeenFileEntries.insert(
+      {Filename, std::errc::no_such_file_or_directory}).first;
+  if (NamedFileEnt.second) {
+    SeenFileEntryOrRedirect Value = *NamedFileEnt.second;
+    FileEntry *FE;
+    if (LLVM_LIKELY(FE = Value.dyn_cast<FileEntry *>()))
+      return FE;
+    return getVirtualFile(*Value.get<const StringRef *>(), Size,
+                          ModificationTime);
+  }
+
+  // We've not seen this before, or the file is cached as non-existent.
+  ++NumFileCacheMisses;
+  addAncestorsAsVirtualDirs(Filename);
+  FileEntry *UFE = nullptr;
+
+  // Now that all ancestors of Filename are in the cache, the
+  // following call is guaranteed to find the DirectoryEntry from the
+  // cache.
+  auto DirInfo = getDirectoryFromFile(*this, Filename, /*CacheFailure=*/true);
+  assert(DirInfo &&
+         "The directory of a virtual file should already be in the cache.");
+
+  // Check to see if the file exists. If so, drop the virtual file
+  llvm::vfs::Status Status;
+  const char *InterndFileName = NamedFileEnt.first().data();
+  if (!getStatValue(InterndFileName, Status, true, nullptr)) {
+    UFE = &UniqueRealFiles[Status.getUniqueID()];
+    Status = llvm::vfs::Status(
+      Status.getName(), Status.getUniqueID(),
+      llvm::sys::toTimePoint(ModificationTime),
+      Status.getUser(), Status.getGroup(), Size,
+      Status.getType(), Status.getPermissions());
+
+    NamedFileEnt.second = UFE;
+
+    // If we had already opened this file, close it now so we don't
+    // leak the descriptor. We're not going to use the file
+    // descriptor anyway, since this is a virtual file.
+    if (UFE->File)
+      UFE->closeFile();
+
+    // If we already have an entry with this inode, return it.
+    if (UFE->isValid())
+      return UFE;
+
+    UFE->UniqueID = Status.getUniqueID();
+    UFE->IsNamedPipe = Status.getType() == llvm::sys::fs::file_type::fifo_file;
+    fillRealPathName(UFE, Status.getName());
+  } else {
+    VirtualFileEntries.push_back(std::make_unique<FileEntry>());
+    UFE = VirtualFileEntries.back().get();
+    NamedFileEnt.second = UFE;
+  }
+
+  UFE->Name    = InterndFileName;
+  UFE->Size    = Size;
+  UFE->ModTime = ModificationTime;
+  UFE->Dir     = *DirInfo;
+  UFE->UID     = NextFileUID++;
+  UFE->IsValid = true;
+  UFE->File.reset();
+  return UFE;
+}
+
+llvm::Optional<FileEntryRef> FileManager::getBypassFile(FileEntryRef VF) {
+  // Stat of the file and return nullptr if it doesn't exist.
+  llvm::vfs::Status Status;
+  if (getStatValue(VF.getName(), Status, /*isFile=*/true, /*F=*/nullptr))
+    return None;
+
+  // Fill it in from the stat.
+  BypassFileEntries.push_back(std::make_unique<FileEntry>());
+  const FileEntry &VFE = VF.getFileEntry();
+  FileEntry &BFE = *BypassFileEntries.back();
+  BFE.Name = VFE.getName();
+  BFE.Size = Status.getSize();
+  BFE.Dir = VFE.Dir;
+  BFE.ModTime = llvm::sys::toTimeT(Status.getLastModificationTime());
+  BFE.UID = NextFileUID++;
+  BFE.IsValid = true;
+  return FileEntryRef(VF.getName(), BFE);
+}
+
+bool FileManager::FixupRelativePath(SmallVectorImpl<char> &path) const {
+  StringRef pathRef(path.data(), path.size());
+
+  if (FileSystemOpts.WorkingDir.empty()
+      || llvm::sys::path::is_absolute(pathRef))
+    return false;
+
+  SmallString<128> NewPath(FileSystemOpts.WorkingDir);
+  llvm::sys::path::append(NewPath, pathRef);
+  path = NewPath;
+  return true;
+}
+
+bool FileManager::makeAbsolutePath(SmallVectorImpl<char> &Path) const {
+  bool Changed = FixupRelativePath(Path);
+
+  if (!llvm::sys::path::is_absolute(StringRef(Path.data(), Path.size()))) {
+    FS->makeAbsolute(Path);
+    Changed = true;
+  }
+
+  return Changed;
+}
+
+void FileManager::fillRealPathName(FileEntry *UFE, llvm::StringRef FileName) {
+  llvm::SmallString<128> AbsPath(FileName);
+  // This is not the same as `VFS::getRealPath()`, which resolves symlinks
+  // but can be very expensive on real file systems.
+  // FIXME: the semantic of RealPathName is unclear, and the name might be
+  // misleading. We need to clean up the interface here.
+  makeAbsolutePath(AbsPath);
+  llvm::sys::path::remove_dots(AbsPath, /*remove_dot_dot=*/true);
+  UFE->RealPathName = AbsPath.str();
+}
+
+llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+FileManager::getBufferForFile(const FileEntry *Entry, bool isVolatile) {
+  uint64_t FileSize = Entry->getSize();
+  // If there's a high enough chance that the file have changed since we
+  // got its size, force a stat before opening it.
+  if (isVolatile)
+    FileSize = -1;
+
+  StringRef Filename = Entry->getName();
+  // If the file is already open, use the open file descriptor.
+  if (Entry->File) {
+    auto Result =
+        Entry->File->getBuffer(Filename, FileSize,
+                               /*RequiresNullTerminator=*/true, isVolatile);
+    Entry->closeFile();
+    return Result;
+  }
+
+  // Otherwise, open the file.
+  return getBufferForFileImpl(Filename, FileSize, isVolatile);
+}
+
+llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+FileManager::getBufferForFileImpl(StringRef Filename, int64_t FileSize,
+                                  bool isVolatile) {
+  if (FileSystemOpts.WorkingDir.empty())
+    return FS->getBufferForFile(Filename, FileSize,
+                                /*RequiresNullTerminator=*/true, isVolatile);
+
+  SmallString<128> FilePath(Filename);
+  FixupRelativePath(FilePath);
+  return FS->getBufferForFile(FilePath, FileSize,
+                              /*RequiresNullTerminator=*/true, isVolatile);
+}
+
+/// getStatValue - Get the 'stat' information for the specified path,
+/// using the cache to accelerate it if possible.  This returns true
+/// if the path points to a virtual file or does not exist, or returns
+/// false if it's an existent real file.  If FileDescriptor is NULL,
+/// do directory look-up instead of file look-up.
+std::error_code
+FileManager::getStatValue(StringRef Path, llvm::vfs::Status &Status,
+                          bool isFile, std::unique_ptr<llvm::vfs::File> *F) {
+  // FIXME: FileSystemOpts shouldn't be passed in here, all paths should be
+  // absolute!
+  if (FileSystemOpts.WorkingDir.empty())
+    return FileSystemStatCache::get(Path, Status, isFile, F,
+                                    StatCache.get(), *FS);
+
+  SmallString<128> FilePath(Path);
+  FixupRelativePath(FilePath);
+
+  return FileSystemStatCache::get(FilePath.c_str(), Status, isFile, F,
+                                  StatCache.get(), *FS);
+}
+
+std::error_code 
+FileManager::getNoncachedStatValue(StringRef Path,
+                                   llvm::vfs::Status &Result) {
+  SmallString<128> FilePath(Path);
+  FixupRelativePath(FilePath);
+
+  llvm::ErrorOr<llvm::vfs::Status> S = FS->status(FilePath.c_str());
+  if (!S)
+    return S.getError();
+  Result = *S;
+  return std::error_code();
+}
+
+void FileManager::GetUniqueIDMapping(
+                   SmallVectorImpl<const FileEntry *> &UIDToFiles) const {
+  UIDToFiles.clear();
+  UIDToFiles.resize(NextFileUID);
+
+  // Map file entries
+  for (llvm::StringMap<llvm::ErrorOr<SeenFileEntryOrRedirect>,
+                       llvm::BumpPtrAllocator>::const_iterator
+           FE = SeenFileEntries.begin(),
+           FEEnd = SeenFileEntries.end();
+       FE != FEEnd; ++FE)
+    if (llvm::ErrorOr<SeenFileEntryOrRedirect> Entry = FE->getValue()) {
+      if (const auto *FE = (*Entry).dyn_cast<FileEntry *>())
+        UIDToFiles[FE->getUID()] = FE;
+    }
+
+  // Map virtual file entries
+  for (const auto &VFE : VirtualFileEntries)
+    UIDToFiles[VFE->getUID()] = VFE.get();
+}
+
+StringRef FileManager::getCanonicalName(const DirectoryEntry *Dir) {
+  llvm::DenseMap<const void *, llvm::StringRef>::iterator Known
+    = CanonicalNames.find(Dir);
+  if (Known != CanonicalNames.end())
+    return Known->second;
+
+  StringRef CanonicalName(Dir->getName());
+
+  SmallString<4096> CanonicalNameBuf;
+  if (!FS->getRealPath(Dir->getName(), CanonicalNameBuf))
+    CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
+
+  CanonicalNames.insert({Dir, CanonicalName});
+  return CanonicalName;
+}
+
+StringRef FileManager::getCanonicalName(const FileEntry *File) {
+  llvm::DenseMap<const void *, llvm::StringRef>::iterator Known
+    = CanonicalNames.find(File);
+  if (Known != CanonicalNames.end())
+    return Known->second;
+
+  StringRef CanonicalName(File->getName());
+
+  SmallString<4096> CanonicalNameBuf;
+  if (!FS->getRealPath(File->getName(), CanonicalNameBuf))
+    CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
+
+  CanonicalNames.insert({File, CanonicalName});
+  return CanonicalName;
+}
+
+void FileManager::PrintStats() const {
+  llvm::errs() << "\n*** File Manager Stats:\n";
+  llvm::errs() << UniqueRealFiles.size() << " real files found, "
+               << UniqueRealDirs.size() << " real dirs found.\n";
+  llvm::errs() << VirtualFileEntries.size() << " virtual files found, "
+               << VirtualDirectoryEntries.size() << " virtual dirs found.\n";
+  llvm::errs() << NumDirLookups << " dir lookups, "
+               << NumDirCacheMisses << " dir cache misses.\n";
+  llvm::errs() << NumFileLookups << " file lookups, "
+               << NumFileCacheMisses << " file cache misses.\n";
+
+  //llvm::errs() << PagesMapped << BytesOfPagesMapped << FSLookups;
+}