Serialization: Simplify PackType serialization

Author: slavapestov

lib/Serialization/DeclTypeRecordNodes.def

@@ -115,7 +115,6 @@ TYPE(NAME_ALIAS)
 
 TYPE(PACK_EXPANSION)
 TYPE(PACK)
-TRAILING_INFO(PACK_TYPE_ELT)
 TYPE(SIL_PACK)
 
 TYPE(ERROR)

lib/Serialization/Deserialization.cpp

@@ -6876,31 +6876,18 @@ Expected<Type> DESERIALIZE_TYPE(PACK_EXPANSION_TYPE)(
 
 Expected<Type> DESERIALIZE_TYPE(PACK_TYPE)(
     ModuleFile &MF, SmallVectorImpl<uint64_t> &scratch, StringRef blobData) {
-  // The pack record itself is empty. Read all trailing elements.
-  SmallVector<Type, 8> elements;
-  while (true) {
-    llvm::BitstreamEntry entry =
-        MF.fatalIfUnexpected(MF.DeclTypeCursor.advance(AF_DontPopBlockAtEnd));
-    if (entry.Kind != llvm::BitstreamEntry::Record)
-      break;
-
-    scratch.clear();
-    unsigned recordID = MF.fatalIfUnexpected(
-        MF.DeclTypeCursor.readRecord(entry.ID, scratch, &blobData));
-    if (recordID != decls_block::PACK_TYPE_ELT)
-      break;
-
-    TypeID typeID;
-    decls_block::PackTypeEltLayout::readRecord(scratch, typeID);
-
-    auto elementTy = MF.getTypeChecked(typeID);
-    if (!elementTy)
-      return elementTy.takeError();
+  ArrayRef<uint64_t> elementTypeIDs;
+  decls_block::PackTypeLayout::readRecord(scratch, elementTypeIDs);
 
-    elements.push_back(elementTy.get());
+  SmallVector<Type, 8> elementTypes;
+  for (auto elementTypeID : elementTypeIDs) {
+    auto elementType = MF.getTypeChecked(elementTypeID);
+    if (!elementType)
+      return elementType.takeError();
+    elementTypes.push_back(elementType.get());
   }
 
-  return PackType::get(MF.getContext(), elements);
+  return PackType::get(MF.getContext(), elementTypes);
 }
 
 Expected<Type> DESERIALIZE_TYPE(SIL_PACK_TYPE)(

lib/Serialization/ModuleFormat.h

@@ -58,7 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 758; // drop_deinit instruction
+const uint16_t SWIFTMODULE_VERSION_MINOR = 759; // change PackType
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -1327,14 +1327,10 @@ namespace decls_block {
   );
 
   TYPE_LAYOUT(PackTypeLayout,
-    PACK_TYPE
+    PACK_TYPE,
+    BCArray<TypeIDField>  // component types
   );
 
-  using PackTypeEltLayout = BCRecordLayout<
-    PACK_TYPE_ELT,
-    TypeIDField         // type
-  >;
-
   TYPE_LAYOUT(SILPackTypeLayout,
     SIL_PACK_TYPE,
     BCFixed<1>,         // is address

lib/Serialization/Serialization.cpp

@@ -5004,14 +5004,14 @@ class Serializer::TypeSerializer : public TypeVisitor<TypeSerializer> {
   void visitPackType(const PackType *packTy) {
     using namespace decls_block;
     unsigned abbrCode = S.DeclTypeAbbrCodes[PackTypeLayout::Code];
-    PackTypeLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode);
 
-    abbrCode = S.DeclTypeAbbrCodes[PackTypeEltLayout::Code];
-    for (auto elt : packTy->getElementTypes()) {
-      PackTypeEltLayout::emitRecord(
-          S.Out, S.ScratchRecord, abbrCode,
-          S.addTypeRef(elt));
+    SmallVector<TypeID, 8> variableData;
+    for (auto elementType : packTy->getElementTypes()) {
+      variableData.push_back(S.addTypeRef(elementType));
     }
+
+    PackTypeLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
+                               variableData);
   }
 
   void visitSILPackType(const SILPackType *packTy) {
@@ -5568,7 +5568,6 @@ void Serializer::writeAllDeclsAndTypes() {
   registerDeclTypeAbbr<DynamicSelfTypeLayout>();
   registerDeclTypeAbbr<PackExpansionTypeLayout>();
   registerDeclTypeAbbr<PackTypeLayout>();
-  registerDeclTypeAbbr<PackTypeEltLayout>();
 
   registerDeclTypeAbbr<ErrorFlagLayout>();
   registerDeclTypeAbbr<ErrorTypeLayout>();