Stop serializing always-zero uint32_t

Author: jansvoboda11

clang/include/clang/Serialization/ASTBitCodes.h

@@ -44,7 +44,7 @@ namespace serialization {
 /// Version 4 of AST files also requires that the version control branch and
 /// revision match exactly, since there is no backward compatibility of
 /// AST files at this time.
-const unsigned VERSION_MAJOR = 32;
+const unsigned VERSION_MAJOR = 33;
 
 /// AST file minor version number supported by this version of
 /// Clang.

clang/lib/Serialization/ASTReader.cpp

@@ -2122,9 +2122,6 @@ HeaderFileInfoTrait::ReadData(internal_key_ref key, const unsigned char *d,
   HFI.DirInfo = (Flags >> 1) & 0x07;
   HFI.LazyControllingMacro = Reader.getGlobalIdentifierID(
       M, endian::readNext<IdentifierID, llvm::endianness::little>(d));
-  auto Zero = endian::readNext<uint32_t, llvm::endianness::little>(d);
-  assert(Zero == 0);
-  (void)Zero;
 
   assert((End - d) % 4 == 0 &&
          "Wrong data length in HeaderFileInfo deserialization");

clang/lib/Serialization/ASTWriter.cpp

@@ -2001,7 +2001,7 @@ namespace {
     std::pair<unsigned, unsigned>
     EmitKeyDataLength(raw_ostream& Out, key_type_ref key, data_type_ref Data) {
       unsigned KeyLen = key.Filename.size() + 1 + 8 + 8;
-      unsigned DataLen = 1 + sizeof(IdentifierID) + 4;
+      unsigned DataLen = 1 + sizeof(IdentifierID);
       for (auto ModInfo : Data.KnownHeaders)
         if (Writer.getLocalOrImportedSubmoduleID(ModInfo.getModule()))
           DataLen += 4;
@@ -2041,8 +2041,6 @@ namespace {
         LE.write<IdentifierID>(
             Writer.getIdentifierRef(Data.HFI.LazyControllingMacro.getPtr()));
 
-      LE.write<uint32_t>(0);
-
       auto EmitModule = [&](Module *M, ModuleMap::ModuleHeaderRole Role) {
         if (uint32_t ModID = Writer.getLocalOrImportedSubmoduleID(M)) {
           uint32_t Value = (ModID << 3) | (unsigned)Role;