3 files changed, 18 insertions, 2 deletions
diff --git a/clang/lib/Serialization/ASTCommon.h b/clang/lib/Serialization/ASTCommon.h
index fa3ef58a1c0..ef81e690324 100644
--- a/clang/lib/Serialization/ASTCommon.h
+++ b/clang/lib/Serialization/ASTCommon.h
@@ -26,7 +26,8 @@ enum DeclUpdateKind {
   UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION,
   UPD_CXX_ADDED_ANONYMOUS_NAMESPACE,
   UPD_CXX_INSTANTIATED_STATIC_DATA_MEMBER,
-  UPD_CXX_DEDUCED_RETURN_TYPE
+  UPD_CXX_DEDUCED_RETURN_TYPE,
+  UPD_DECL_MARKED_USED
 };
 
 TypeIdx TypeIdxFromBuiltin(const BuiltinType *BT);
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 67ca94bbf8e..b16966530e8 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -377,7 +377,7 @@ void ASTDeclReader::VisitDecl(Decl *D) {
     D->setAttrsImpl(Attrs, Reader.getContext());
   }
   D->setImplicit(Record[Idx++]);
-  D->setUsed(Record[Idx++]);
+  D->setIsUsed(Record[Idx++]);
   D->setReferenced(Record[Idx++]);
   D->setTopLevelDeclInObjCContainer(Record[Idx++]);
   D->setAccess((AccessSpecifier)Record[Idx++]);
@@ -2838,6 +2838,11 @@ void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
           FD, Reader.readType(ModuleFile, Record, Idx));
       break;
     }
+
+    case UPD_DECL_MARKED_USED: {
+      D->markUsed(Reader.getContext());
+      break;
+    }
     }
   }
 }
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index f8e8b5d7ada..28a5a423fdf 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4314,6 +4314,7 @@ void ASTWriter::ResolveDeclUpdatesBlocks() {
         break;
 
       case UPD_CXX_INSTANTIATED_STATIC_DATA_MEMBER:
+      case UPD_DECL_MARKED_USED:
         ++Idx;
         break;
 
@@ -5370,3 +5371,12 @@ void ASTWriter::AddedObjCPropertyInClassExtension(const ObjCPropertyDecl *Prop,
 
   RewriteDecl(D);
 }
+
+void ASTWriter::DeclarationMarkedUsed(const Decl *D) {
+  assert(!WritingAST && "Already writing the AST!");
+  if (!D->isFromASTFile())
+    return;
+
+  UpdateRecord &Record = DeclUpdates[D];
+  Record.push_back(UPD_DECL_MARKED_USED);
+}