diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -483,6 +483,12 @@
     PSK_Pop_Set   = PSK_Pop | PSK_Set,  // #pragma (pop[, id], value)
   };
 
+  struct PragmaPackInfo {
+    PragmaMsStackAction Action;
+    StringRef SlotLabel;
+    Token Alignment;
+  };
+
   // #pragma pack and align.
   class AlignPackInfo {
   public:
diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
--- a/clang/include/clang/Serialization/ASTReader.h
+++ b/clang/include/clang/Serialization/ASTReader.h
@@ -2236,7 +2236,7 @@
                               unsigned &Idx, LocSeq *Seq = nullptr);
 
   // Read a string
-  static std::string ReadString(const RecordData &Record, unsigned &Idx);
+  static std::string ReadString(const RecordDataImpl &Record, unsigned &Idx);
 
   // Skip a string
   static void SkipString(const RecordData &Record, unsigned &Idx) {
diff --git a/clang/lib/Parse/ParsePragma.cpp b/clang/lib/Parse/ParsePragma.cpp
--- a/clang/lib/Parse/ParsePragma.cpp
+++ b/clang/lib/Parse/ParsePragma.cpp
@@ -665,18 +665,10 @@
   Actions.ActOnPragmaVisibility(VisType, VisLoc);
 }
 
-namespace {
-struct PragmaPackInfo {
-  Sema::PragmaMsStackAction Action;
-  StringRef SlotLabel;
-  Token Alignment;
-};
-} // end anonymous namespace
-
 void Parser::HandlePragmaPack() {
   assert(Tok.is(tok::annot_pragma_pack));
-  PragmaPackInfo *Info =
-    static_cast<PragmaPackInfo *>(Tok.getAnnotationValue());
+  Sema::PragmaPackInfo *Info =
+    static_cast<Sema::PragmaPackInfo *>(Tok.getAnnotationValue());
   SourceLocation PragmaLoc = Tok.getLocation();
   ExprResult Alignment;
   if (Info->Alignment.is(tok::numeric_constant)) {
@@ -2110,8 +2102,8 @@
     return;
   }
 
-  PragmaPackInfo *Info =
-      PP.getPreprocessorAllocator().Allocate<PragmaPackInfo>(1);
+  Sema::PragmaPackInfo *Info =
+      PP.getPreprocessorAllocator().Allocate<Sema::PragmaPackInfo>(1);
   Info->Action = Action;
   Info->SlotLabel = SlotLabel;
   Info->Alignment = Alignment;
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1687,6 +1687,15 @@
       Tok.setAnnotationValue(static_cast<void *>(Info));
       break;
     }
+    case tok::annot_pragma_pack: {
+      auto *Info = new (PP.getPreprocessorAllocator()) Sema::PragmaPackInfo;
+      Info->Action = static_cast<Sema::PragmaMsStackAction>(Record[Idx++]);
+      PragmaAlignPackStrings.push_back(ReadString(Record, Idx));
+      Info->SlotLabel = PragmaAlignPackStrings.back();
+      Info->Alignment = ReadToken(F, Record, Idx);
+      Tok.setAnnotationValue(static_cast<void *>(Info));
+      break;
+    }
     // Some annotation tokens do not use the PtrData field.
     case tok::annot_pragma_openmp:
     case tok::annot_pragma_openmp_end:
@@ -9089,7 +9098,7 @@
 }
 
 // Read a string
-std::string ASTReader::ReadString(const RecordData &Record, unsigned &Idx) {
+std::string ASTReader::ReadString(const RecordDataImpl &Record, unsigned &Idx) {
   unsigned Len = Record[Idx++];
   std::string Result(Record.data() + Idx, Record.data() + Idx + Len);
   Idx += Len;
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4412,6 +4412,14 @@
         AddToken(T, Record);
       break;
     }
+    case tok::annot_pragma_pack: {
+      auto *Info =
+          static_cast<Sema::PragmaPackInfo *>(Tok.getAnnotationValue());
+      Record.push_back(static_cast<unsigned>(Info->Action));
+      AddString(Info->SlotLabel, Record);
+      AddToken(Info->Alignment, Record);
+      break;
+    }
     // Some annotation tokens do not use the PtrData field.
     case tok::annot_pragma_openmp:
     case tok::annot_pragma_openmp_end: