Index: include/clang/Basic/FileManager.h
===================================================================
--- include/clang/Basic/FileManager.h
+++ include/clang/Basic/FileManager.h
@@ -173,6 +173,10 @@
   /// or a directory) as virtual directories.
   void addAncestorsAsVirtualDirs(StringRef Path);
 
+  /// Fills the RealPathName entry in UFE by converting the given filename to an
+  /// absolute path, returns true if FileName was modified.
+  bool fillRealPathName(FileEntry *UFE, llvm::StringRef FileName);
+
 public:
   FileManager(const FileSystemOptions &FileSystemOpts,
               IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS = nullptr);
Index: lib/Basic/FileManager.cpp
===================================================================
--- lib/Basic/FileManager.cpp
+++ lib/Basic/FileManager.cpp
@@ -293,16 +293,8 @@
   // If we opened the file for the first time, record the resulting info.
   // Do this even if the cache entry was valid, maybe we didn't previously open.
   if (F && !UFE.File) {
-    if (auto PathName = F->getName()) {
-      llvm::SmallString<128> AbsPath(*PathName);
-      // 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();
-    }
+    if (auto PathName = F->getName())
+      fillRealPathName(&UFE, *PathName);
     UFE.File = std::move(F);
     assert(!UFE.DeferredOpen && "we just opened it!");
   }
@@ -395,6 +387,7 @@
     UFE->UniqueID = Data.UniqueID;
     UFE->IsNamedPipe = Data.IsNamedPipe;
     UFE->InPCH = Data.InPCH;
+    fillRealPathName(UFE, Data.Name);
   }
 
   if (!UFE) {
@@ -438,6 +431,18 @@
   return Changed;
 }
 
+bool 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.
+  bool Changed = makeAbsolutePath(AbsPath);
+  llvm::sys::path::remove_dots(AbsPath, /*remove_dot_dot=*/true);
+  UFE->RealPathName = AbsPath.str();
+  return Changed;
+}
+
 llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
 FileManager::getBufferForFile(const FileEntry *Entry, bool isVolatile,
                               bool ShouldCloseOpenFile) {