[PCH] Fix a regression when PCH is used with -fmodules

Following up on r291465 after a regression in r276159. When we use
-fmodule-name=X while building a PCH, modular headers in X will be
textually included and the compiler knows that we are not building
module X, so don't serialize such headers in the PCH as being part of a
module, because at this point they are not.

This was causing subtle bugs and malformed AST crashes, for instance,
when using the PCH in subsequent compiler invocation with -fmodules, the
HFI for a modular header would map to the PCH, which would force a
module load of and unexistent module ID.

rdar://problem/30171164

llvm-svn: 294361

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 69136015f48..5dee86c1419 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2544,7 +2544,8 @@ unsigned ASTWriter::getLocalOrImportedSubmoduleID(Module *Mod) {
 
   auto *Top = Mod->getTopLevelModule();
   if (Top != WritingModule &&
-      !Top->fullModuleNameIs(StringRef(getLangOpts().CurrentModule)))
+      (getLangOpts().CompilingPCH ||
+       !Top->fullModuleNameIs(StringRef(getLangOpts().CurrentModule))))
     return 0;
 
   return SubmoduleIDs[Mod] = NextSubmoduleID++;