diff --git a/clang/include/clang/Basic/FileManager.h b/clang/include/clang/Basic/FileManager.h
index aff9758f8146..7f733fb9ffe1 100644
--- a/clang/include/clang/Basic/FileManager.h
+++ b/clang/include/clang/Basic/FileManager.h
@@ -22,6 +22,7 @@
 #include <string>
 // FIXME: Enhance libsystem to support inode and other fields in stat.
 #include <sys/types.h>
+#include <sys/stat.h>
 
 namespace clang {
 class FileManager;
@@ -68,6 +69,14 @@ public:
   }
 };
 
+// FIXME: This is a lightweight shim that is used by FileManager to cache
+//  'stat' system calls.  We will use it with PTH to identify if caching
+//  stat calls in PTH files is a performance win.
+class StatSysCallCache {
+public:
+  virtual ~StatSysCallCache() {}
+  virtual int stat(const char *path, struct stat *buf) = 0;
+};
  
 /// FileManager - Implements support for file system lookup, file system
 /// caching, and directory search management.  This also handles more advanced
@@ -97,8 +106,15 @@ class FileManager {
   // Statistics.
   unsigned NumDirLookups, NumFileLookups;
   unsigned NumDirCacheMisses, NumFileCacheMisses;
+  
+  // Caching.
+  StatSysCallCache *StatCache;
+  int stat_cached(const char* path, struct stat* buf) {
+    return StatCache ? StatCache->stat(path, buf) : stat(path, buf);
+  }
+  
 public:
-  FileManager();
+  FileManager(StatSysCallCache *statCache = 0);
   ~FileManager();
 
   /// getDirectory - Lookup, cache, and verify the specified directory.  This
diff --git a/clang/lib/Basic/FileManager.cpp b/clang/lib/Basic/FileManager.cpp
index 9ae1ad4c28de..666c984e2399 100644
--- a/clang/lib/Basic/FileManager.cpp
+++ b/clang/lib/Basic/FileManager.cpp
@@ -29,7 +29,7 @@ using namespace clang;
 #include <sys/stat.h>
 
 #if defined(_MSC_VER)
-#define S_ISDIR(s) (_S_IFDIR & s)
+#defisstne S_ISDIR(s) (_S_IFDIR & s)
 #endif
 
 /// NON_EXISTENT_DIR - A special value distinct from null that is used to
@@ -134,10 +134,11 @@ public:
 // Common logic.
 //===----------------------------------------------------------------------===//
 
-FileManager::FileManager() : UniqueDirs(*new UniqueDirContainer),
-                             UniqueFiles(*new UniqueFileContainer),
-                             DirEntries(64), FileEntries(64), NextFileUID(0)
-{
+FileManager::FileManager(StatSysCallCache* statCache)
+  : UniqueDirs(*new UniqueDirContainer),
+    UniqueFiles(*new UniqueFileContainer),
+    DirEntries(64), FileEntries(64), NextFileUID(0),
+    StatCache(statCache) {
   NumDirLookups = NumFileLookups = 0;
   NumDirCacheMisses = NumFileCacheMisses = 0;
 }
@@ -145,6 +146,7 @@ FileManager::FileManager() : UniqueDirs(*new UniqueDirContainer),
 FileManager::~FileManager() {
   delete &UniqueDirs;
   delete &UniqueFiles;
+  delete StatCache;
 }
 
 
@@ -173,7 +175,7 @@ const DirectoryEntry *FileManager::getDirectory(const char *NameStart,
   
   // Check to see if the directory exists.
   struct stat StatBuf;
-  if (stat(InterndDirName, &StatBuf) ||   // Error stat'ing.
+  if (stat_cached(InterndDirName, &StatBuf) ||   // Error stat'ing.
       !S_ISDIR(StatBuf.st_mode))          // Not a directory?
     return 0;
 
@@ -246,8 +248,8 @@ const FileEntry *FileManager::getFile(const char *NameStart,
   // Nope, there isn't.  Check to see if the file exists.
   struct stat StatBuf;
   //llvm::cerr << "STATING: " << Filename;
-  if (stat(InterndFileName, &StatBuf) ||   // Error stat'ing.
-      S_ISDIR(StatBuf.st_mode)) {           // A directory?
+  if (stat_cached(InterndFileName, &StatBuf) ||   // Error stat'ing.
+        S_ISDIR(StatBuf.st_mode)) {           // A directory?
     // If this file doesn't exist, we leave a null in FileEntries for this path.
     //llvm::cerr << ": Not existing\n";
     return 0;