FileManager: Shrink FileEntryRef to the size of a pointer

Shrink `FileEntryRef` to the size of a pointer, by having it directly
reference the `StringMapEntry` the same way that `DirectoryEntryRef`
does. This makes `FileEntryRef::FileEntryRef` private as a side effect
(`FileManager` is a friend!).

There are two helper types added within `FileEntryRef`:

- `FileEntryRef::MapValue` is the type stored in
  `FileManager::SeenFileEntries`. It's a replacement for
  `SeenFileEntryOrRedirect`, where the second pointer type has been
  changed from `StringRef*` to `MapEntry*` (see next bullet).
- `FileEntryRef::MapEntry` is the instantiation of `StringMapEntry<>`
  where `MapValue` is stored. This is what `FileEntryRef` has a pointer
  to, in order to grab the name in addition to the value.

Differential Revision: https://reviews.llvm.org/D89488

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
index 88f95d1..dde4471 100644
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -702,7 +702,7 @@ const FileEntry *
 SourceManager::bypassFileContentsOverride(const FileEntry &File) {
   assert(isFileOverridden(&File));
   llvm::Optional<FileEntryRef> BypassFile =
-      FileMgr.getBypassFile(FileEntryRef(File.getName(), File));
+      FileMgr.getBypassFile(File.getLastRef());
 
   // If the file can't be found in the FS, give up.
   if (!BypassFile)