Forward declare FileEntry and DirectoryEntry in Module.h

FileManager.h is an expensive header (~350ms for me in isolation), so
try to do without it.

Notably, we need to avoid checking the alignment of FileEntry, which
happens for DenseMap<FileEntry*> and PointerUnion<FileEntry*>. I
adjusted the code to avoid PointerUnion, and moved the DenseMap
insertion to the .cpp file.

Globally, this only saved about ~17 includes of the related headers
because SourceManager.h still includes FileManager.h, and it is more
popular than Module.h.

1 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/Basic/Module.cpp b/clang/lib/Basic/Module.cpp
index 92835c9..7fb6dee 100644
--- a/clang/lib/Basic/Module.cpp
+++ b/clang/lib/Basic/Module.cpp
@@ -44,7 +44,7 @@ Module::Module(StringRef Name, SourceLocation DefinitionLoc, Module *Parent,
       InferSubmodules(false), InferExplicitSubmodules(false),
       InferExportWildcard(false), ConfigMacrosExhaustive(false),
       NoUndeclaredIncludes(false), ModuleMapIsPrivate(false),
-      NameVisibility(Hidden) {
+      HasUmbrellaDir(false), NameVisibility(Hidden) {
   if (Parent) {
     if (!Parent->isAvailable())
       IsAvailable = false;
@@ -239,7 +239,12 @@ Module::DirectoryName Module::getUmbrellaDir() const {
   if (Header U = getUmbrellaHeader())
     return {"", U.Entry->getDir()};
 
-  return {UmbrellaAsWritten, Umbrella.dyn_cast<const DirectoryEntry *>()};
+  return {UmbrellaAsWritten, static_cast<const DirectoryEntry *>(Umbrella)};
+}
+
+void Module::addTopHeader(const FileEntry *File) {
+  assert(File);
+  TopHeaders.insert(File);
 }
 
 ArrayRef<const FileEntry *> Module::getTopHeaders(FileManager &FileMgr) {