3 files changed, 22 insertions, 6 deletions
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index a51f144ae06..322fc863be9 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -8147,8 +8147,7 @@ ASTReader::getSourceDescriptor(unsigned ID) {
   return None;
 }
 
-ExternalASTSource::ExtKind
-ASTReader::hasExternalDefinitions(const FunctionDecl *FD) {
+ExternalASTSource::ExtKind ASTReader::hasExternalDefinitions(const Decl *FD) {
   auto I = BodySource.find(FD);
   if (I == BodySource.end())
     return EK_ReplyHazy;
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 9b9b41a104f..db7d55ec0b8 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -119,7 +119,8 @@ namespace clang {
     }
 
     void ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update);
-    void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data);
+    void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data,
+                               const CXXRecordDecl *D);
     void MergeDefinitionData(CXXRecordDecl *D,
                              struct CXXRecordDecl::DefinitionData &&NewDD);
     void ReadObjCDefinitionData(struct ObjCInterfaceDecl::DefinitionData &Data);
@@ -1490,7 +1491,7 @@ void ASTDeclReader::VisitUnresolvedUsingTypenameDecl(
 }
 
 void ASTDeclReader::ReadCXXDefinitionData(
-                                   struct CXXRecordDecl::DefinitionData &Data) {
+    struct CXXRecordDecl::DefinitionData &Data, const CXXRecordDecl *D) {
   // Note: the caller has deserialized the IsLambda bit already.
   Data.UserDeclaredConstructor = Record.readInt();
   Data.UserDeclaredSpecialMembers = Record.readInt();
@@ -1536,6 +1537,12 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.HasDeclaredCopyAssignmentWithConstParam = Record.readInt();
   Data.ODRHash = Record.readInt();
 
+  if (Record.readInt()) {
+    Reader.BodySource[D] = Loc.F->Kind == ModuleKind::MK_MainFile
+                               ? ExternalASTSource::EK_Never
+                               : ExternalASTSource::EK_Always;
+  }
+
   Data.NumBases = Record.readInt();
   if (Data.NumBases)
     Data.Bases = ReadGlobalOffset();
@@ -1707,7 +1714,7 @@ void ASTDeclReader::ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update) {
   else
     DD = new (C) struct CXXRecordDecl::DefinitionData(D);
 
-  ReadCXXDefinitionData(*DD);
+  ReadCXXDefinitionData(*DD, D);
 
   // We might already have a definition for this record. This can happen either
   // because we're reading an update record, or because we've already done some
@@ -2553,7 +2560,11 @@ static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
            Var->isThisDeclarationADefinition() == VarDecl::Definition;
   if (FunctionDecl *Func = dyn_cast<FunctionDecl>(D))
     return Func->doesThisDeclarationHaveABody() || HasBody;
-  
+
+  if (auto *ES = D->getASTContext().getExternalSource())
+    if (ES->hasExternalDefinitions(D) == ExternalASTSource::EK_Never)
+      return true;
+
   return false;
 }
 
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 23859c241d5..ec59250e192 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5770,6 +5770,12 @@ void ASTRecordWriter::AddCXXDefinitionData(const CXXRecordDecl *D) {
   Record->push_back(Data.HasDeclaredCopyConstructorWithConstParam);
   Record->push_back(Data.HasDeclaredCopyAssignmentWithConstParam);
   Record->push_back(Data.ODRHash);
+  bool ModularCodegen = Writer->Context->getLangOpts().ModularCodegen &&
+                        Writer->WritingModule && !D->isDependentType();
+  Record->push_back(ModularCodegen);
+  if (ModularCodegen)
+    Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(D));
+
   // IsLambda bit is already saved.
 
   Record->push_back(Data.NumBases);