Since we're stuck with realpath for the header <-> module mapping,

factor the realpath calls into FileManager::getCanonicalName() so we
can cache the results of this epically slow operation. 5% speedup on
my modules test, and realpath drops out of the profile.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173542 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/include/clang/Basic/FileManager.h b/include/clang/Basic/FileManager.h
index 5914e1608f..6d9e53b7eb 100644
--- a/include/clang/Basic/FileManager.h
+++ b/include/clang/Basic/FileManager.h
@@ -17,6 +17,7 @@
 
 #include "clang/Basic/FileSystemOptions.h"
 #include "clang/Basic/LLVM.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/SmallVector.h"
@@ -152,6 +153,12 @@ class FileManager : public RefCountedBase<FileManager> {
   /// \see SeenDirEntries
   llvm::StringMap<FileEntry*, llvm::BumpPtrAllocator> SeenFileEntries;
 
+  /// \brief The canonical names of directories.
+  llvm::DenseMap<const DirectoryEntry *, llvm::StringRef> CanonicalDirNames;
+
+  /// \brief Storage for canonical names that we have computed.
+  llvm::BumpPtrAllocator CanonicalNameStorage;
+
   /// \brief Each FileEntry we create is assigned a unique ID #.
   ///
   unsigned NextFileUID;
@@ -257,6 +264,13 @@ public:
   static void modifyFileEntry(FileEntry *File, off_t Size,
                               time_t ModificationTime);
 
+  /// \brief Retrieve the canonical name for a given directory.
+  ///
+  /// This is a very expensive operation, despite its results being cached,
+  /// and should only be used when the physical layout of the file system is
+  /// required, which is (almost) never.
+  StringRef getCanonicalName(const DirectoryEntry *Dir);
+
   void PrintStats() const;
 };