[PDB] Put LLD's PDB writing code in a class NFC

[rnk]

Summary

We've accumulated about five or so data structures that are widely
referenced:

• PDBBuilder
• Type table
• Id table
• PDB string table
• Type server handler

I'm about to rewrite type server handling, and I need a new class in LLD
where I can put its state. By creating a new PDBLinker class, I hope to
put it there next.

[rnk]

• fix lifetime issues
• add commit method

[ruiu]

LGTM

lld/COFF/PDB.cpp

537–538

You can remove llvm::.

lld/COFF/PDB.cpp

 using namespace lld::coff;
 using namespace llvm;
 using namespace llvm::codeview;
 
 using llvm::object::coff_section;
 
 static ExitOnError ExitOnErr;
 
+namespace {
+class PDBLinker {
+public:
+  PDBLinker(SymbolTable *Symtab)
+      : Alloc(), Symtab(Symtab), Builder(Alloc), TypeTable(Alloc),
+        IDTable(Alloc) {}
+
+  /// Emit the basic PDB structure: initial streams, headers, etc.
+  void initialize(const llvm::codeview::DebugInfo *DI);
+
+  /// Link CodeView from each object file in the symbol table into the PDB.
+  void addObjectsToPDB();
+
+  /// Link CodeView from a single object file into the PDB.
+  void addObjectFile(ObjectFile *File);
+
+  /// Merge the type information from the .debug$T section in the given object
+  /// file. Produce a mapping from object file type indices to type or
+  /// item indices in the final PDB.
+  void mergeDebugT(ObjectFile *File, SmallVectorImpl<TypeIndex> &TypeIndexMap);
+
+  /// Add the section map and section contributions to the PDB.
+  void addSections(ArrayRef<uint8_t> SectionTable);
+
+private:
+  BumpPtrAllocator Alloc;
+
+  SymbolTable *Symtab;
+
+  pdb::PDBFileBuilder Builder;
+
+  /// Type records that will go into the PDB TPI stream.
+  TypeTableBuilder TypeTable;
+
+  /// Item records that will go into the PDB IPI stream.
+  TypeTableBuilder IDTable;
+
+  /// PDBs use a single global string table for filenames in the file checksum
+  /// table.
+  DebugStringTableSubsection PDBStrTab;
+
+  // Follow type servers.  If the same type server is encountered more than once
+  // for this instance of `PDBTypeServerHandler` (for example if many object
+  // files reference the same TypeServer), the types from the TypeServer will
+  // only be visited once.
+  pdb::PDBTypeServerHandler TSHandler;
+};
+}
+
 // Returns a list of all SectionChunks.
 static void addSectionContribs(SymbolTable *Symtab, pdb::DbiStreamBuilder &DbiBuilder) {
   for (Chunk *C : Symtab->getChunks())
     if (auto *SC = dyn_cast<SectionChunk>(C))
       DbiBuilder.addSectionContrib(SC->File->ModuleDBI, SC->Header);
 }
 
 static SectionChunk *findByName(std::vector<SectionChunk *> &Sections,
static void addTypeInfo(pdb::TpiStreamBuilder &TpiBuilder,
 
   // Flatten the in memory type table.
   TypeTable.ForEachRecord([&](TypeIndex TI, ArrayRef<uint8_t> Rec) {
     // FIXME: Hash types.
     TpiBuilder.addTypeRecord(Rec, None);
   });
 }
 
-static void mergeDebugT(ObjectFile *File,
-                        TypeTableBuilder &IDTable,
-                        TypeTableBuilder &TypeTable,
-                        SmallVectorImpl<TypeIndex> &TypeIndexMap,
-                        pdb::PDBTypeServerHandler &Handler) {
+void PDBLinker::mergeDebugT(ObjectFile *File,
+                            SmallVectorImpl<TypeIndex> &TypeIndexMap) {
   ArrayRef<uint8_t> Data = getDebugSection(File, ".debug$T");
   if (Data.empty())
     return;
 
   // Look for type server PDBs next to the input file. If this file has a parent
   // archive, look next to the archive path.
   StringRef LocalPath =
       !File->ParentName.empty() ? File->ParentName : File->getName();
-  Handler.addSearchPath(sys::path::parent_path(LocalPath));
+  TSHandler.addSearchPath(sys::path::parent_path(LocalPath));
 
   BinaryByteStream Stream(Data, support::little);
   CVTypeArray Types;
   BinaryStreamReader Reader(Stream);
   if (auto EC = Reader.readArray(Types, Reader.getLength()))
     fatal(EC, "Reader::readArray failed");
   if (auto Err = mergeTypeAndIdRecords(IDTable, TypeTable, TypeIndexMap,
-                                       &Handler, Types))
+                                       &TSHandler, Types))
     fatal(Err, "codeview::mergeTypeStreams failed");
 }
 
 static bool remapTypeIndex(TypeIndex &TI, ArrayRef<TypeIndex> TypeIndexMap) {
   if (TI.isSimple())
     return true;
   if (TI.toArrayIndex() >= TypeIndexMap.size())
     return false;
static ArrayRef<uint8_t> relocateDebugChunk(BumpPtrAllocator &Alloc,
   uint8_t *Buffer = Alloc.Allocate<uint8_t>(DebugChunk->getSize());
   assert(DebugChunk->OutputSectionOff == 0 &&
          "debug sections should not be in output sections");
   DebugChunk->writeTo(Buffer);
   return consumeDebugMagic(makeArrayRef(Buffer, DebugChunk->getSize()),
                            ".debug$S");
 }
 
-// Add all object files to the PDB. Merge .debug$T sections into IpiData and
-// TpiData.
-static void addObjectsToPDB(BumpPtrAllocator &Alloc, SymbolTable *Symtab,
-                            pdb::PDBFileBuilder &Builder,
-                            TypeTableBuilder &TypeTable,
-                            TypeTableBuilder &IDTable) {
-  // Follow type servers.  If the same type server is encountered more than
-  // once for this instance of `PDBTypeServerHandler` (for example if many
-  // object files reference the same TypeServer), the types from the
-  // TypeServer will only be visited once.
-  pdb::PDBTypeServerHandler Handler;
-
-  // PDBs use a single global string table for filenames in the file checksum
-  // table.
-  auto PDBStrTab = std::make_shared<DebugStringTableSubsection>();
-
-  // Visit all .debug$T sections to add them to Builder.
-  for (ObjectFile *File : Symtab->ObjectFiles) {
-    // Add a module descriptor for every object file. We need to put an absolute
-    // path to the object into the PDB. If this is a plain object, we make its
-    // path absolute. If it's an object in an archive, we make the archive path
-    // absolute.
-    bool InArchive = !File->ParentName.empty();
-    SmallString<128> Path = InArchive ? File->ParentName : File->getName();
-    sys::fs::make_absolute(Path);
-    sys::path::native(Path, llvm::sys::path::Style::windows);
-    StringRef Name = InArchive ? File->getName() : StringRef(Path);
+void PDBLinker::addObjectFile(ObjectFile *File) {
 
-    File->ModuleDBI = &ExitOnErr(Builder.getDbiBuilder().addModuleInfo(Name));
-    File->ModuleDBI->setObjFileName(Path);
 
-    // Before we can process symbol substreams from .debug$S, we need to process
-    // type information, file checksums, and the string table.  Add type info to
-    // the PDB first, so that we can get the map from object file type and item
-    // indices to PDB type and item indices.
-    SmallVector<TypeIndex, 128> TypeIndexMap;
-    mergeDebugT(File, IDTable, TypeTable, TypeIndexMap, Handler);
+  mergeDebugT(File, TypeIndexMap);
 
-    // Now do all line info.
-    for (SectionChunk *DebugChunk : File->getDebugChunks()) {
-      if (!DebugChunk->isLive() || DebugChunk->getSectionName() != ".debug$S")
-        continue;
+  // Now do all live .debug$S sections.
 
-      ArrayRef<uint8_t> RelocatedDebugContents =
-          relocateDebugChunk(Alloc, DebugChunk);
-      if (RelocatedDebugContents.empty())
-        continue;
 
-      DebugSubsectionArray Subsections;
-      BinaryStreamReader Reader(RelocatedDebugContents, support::little);
-      ExitOnErr(Reader.readArray(Subsections, RelocatedDebugContents.size()));
 
-      DebugStringTableSubsectionRef CVStrTab;
-      DebugChecksumsSubsectionRef Checksums;
-      for (const DebugSubsectionRecord &SS : Subsections) {
-        switch (SS.kind()) {
-        case DebugSubsectionKind::StringTable:
-          ExitOnErr(CVStrTab.initialize(SS.getRecordData()));
-          break;
-        case DebugSubsectionKind::FileChecksums:
-          ExitOnErr(Checksums.initialize(SS.getRecordData()));
-          break;
-        case DebugSubsectionKind::Lines:
-          // We can add the relocated line table directly to the PDB without
-          // modification because the file checksum offsets will stay the same.
-          File->ModuleDBI->addDebugSubsection(SS);
-          break;
-        case DebugSubsectionKind::Symbols:
-          mergeSymbolRecords(Alloc, File, TypeIndexMap, SS.getRecordData());
-          break;
-        default:
-          // FIXME: Process the rest of the subsections.
-          break;
-        }
-      }
 
-      if (Checksums.valid()) {
-        // Make a new file checksum table that refers to offsets in the PDB-wide
-        // string table. Generally the string table subsection appears after the
-        // checksum table, so we have to do this after looping over all the
-        // subsections.
-        if (!CVStrTab.valid())
-          fatal(".debug$S sections must have both a string table subsection "
-                "and a checksum subsection table or neither");
-        auto NewChecksums =
-            make_unique<DebugChecksumsSubsection>(*PDBStrTab);
-        for (FileChecksumEntry &FC : Checksums) {
-          StringRef FileName = ExitOnErr(CVStrTab.getString(FC.FileNameOffset));
-          ExitOnErr(Builder.getDbiBuilder().addModuleSourceFile(
-              *File->ModuleDBI, FileName));
-          NewChecksums->addChecksum(FileName, FC.Kind, FC.Checksum);
-        }
-        File->ModuleDBI->addDebugSubsection(std::move(NewChecksums));
-      }
-    }
-  }
+      auto NewChecksums = make_unique<DebugChecksumsSubsection>(PDBStrTab);
+        ExitOnErr(Builder.getDbiBuilder().addModuleSourceFile(*File->ModuleDBI,
+                                                              FileName));
 
-  Builder.getStringTableBuilder().setStrings(*PDBStrTab);
+// Add all object files to the PDB. Merge .debug$T sections into IpiData and
+// TpiData.
+void PDBLinker::addObjectsToPDB() {
+  for (ObjectFile *File : Symtab->ObjectFiles)
+    addObjectFile(File);
+
+  Builder.getStringTableBuilder().setStrings(PDBStrTab);
 
   // Construct TPI stream contents.
   addTypeInfo(Builder.getTpiBuilder(), TypeTable);
 
   // Construct IPI stream contents.
   addTypeInfo(Builder.getIpiBuilder(), IDTable);
+
+  // Add public and symbol records stream.
+
+  // For now we don't actually write any thing useful to the publics stream, but
+  // the act of "getting" it also creates it lazily so that we write an empty
+  // stream.
+  (void)Builder.getPublicsBuilder();
 }
 
 static void addLinkerModuleSymbols(StringRef Path,
                                    pdb::DbiModuleDescriptorBuilder &Mod,
                                    BumpPtrAllocator &Allocator) {
   codeview::SymbolSerializer Serializer(Allocator, CodeViewContainer::Pdb);
   codeview::ObjNameSym ONS(SymbolRecordKind::ObjNameSym);
   codeview::Compile3Sym CS(SymbolRecordKind::Compile3Sym);
Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       CS, Allocator, CodeViewContainer::Pdb));
   Mod.addSymbol(codeview::SymbolSerializer::writeOneSymbol(
       EBS, Allocator, CodeViewContainer::Pdb));
 }
 
 // Creates a PDB file.
 void coff::createPDB(SymbolTable *Symtab, ArrayRef<uint8_t> SectionTable,
                      const llvm::codeview::DebugInfo *DI) {
-  BumpPtrAllocator Alloc;
-  pdb::PDBFileBuilder Builder(Alloc);
+  PDBLinker PDB(Symtab);
+  PDB.initialize(DI);
+  PDB.addObjectsToPDB();
+  PDB.addSections(SectionTable);
+}
+
+void PDBLinker::initialize(const llvm::codeview::DebugInfo *DI) {
   ExitOnErr(Builder.initialize(4096)); // 4096 is blocksize
 
   // Create streams in MSF for predefined streams, namely
   // PDB, TPI, DBI and IPI.
   for (int I = 0; I < (int)pdb::kSpecialStreamCount; ++I)
     ExitOnErr(Builder.getMsfBuilder().addStream(0));
 
   // Add an Info stream.
   auto &InfoBuilder = Builder.getInfoBuilder();
   InfoBuilder.setAge(DI ? DI->PDB70.Age : 0);
 
-  llvm::SmallString<128> NativePath(Config->PDBPath.begin(),
-                                    Config->PDBPath.end());
-  llvm::sys::fs::make_absolute(NativePath);
-  llvm::sys::path::native(NativePath, llvm::sys::path::Style::windows);
-
   pdb::PDB_UniqueId uuid{};
   if (DI)
     memcpy(&uuid, &DI->PDB70.Signature, sizeof(uuid));
   InfoBuilder.setGuid(uuid);
   InfoBuilder.setSignature(time(nullptr));
   InfoBuilder.setVersion(pdb::PdbRaw_ImplVer::PdbImplVC70);
 
   // Add an empty DBI stream.
   pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
   DbiBuilder.setVersionHeader(pdb::PdbDbiV70);
   ExitOnErr(DbiBuilder.addDbgStream(pdb::DbgHeaderType::NewFPO, {}));
+}
 
-  // It's not entirely clear what this is, but the * Linker * module uses it.
-  uint32_t PdbFilePathNI = DbiBuilder.addECName(NativePath);
-
-  TypeTableBuilder TypeTable(BAlloc);
-  TypeTableBuilder IDTable(BAlloc);
-  addObjectsToPDB(Alloc, Symtab, Builder, TypeTable, IDTable);
-
-  // Add public and symbol records stream.
-
-  // For now we don't actually write any thing useful to the publics stream, but
-  // the act of "getting" it also creates it lazily so that we write an empty
-  // stream.
-  (void)Builder.getPublicsBuilder();
-
+void PDBLinker::addSections(ArrayRef<uint8_t> SectionTable) {
   // Add Section Contributions.
+  pdb::DbiStreamBuilder &DbiBuilder = Builder.getDbiBuilder();
   addSectionContribs(Symtab, DbiBuilder);
 
   // Add Section Map stream.
   ArrayRef<object::coff_section> Sections = {
       (const object::coff_section *)SectionTable.data(),
       SectionTable.size() / sizeof(object::coff_section)};
   std::vector<pdb::SecMapEntry> SectionMap =
       pdb::DbiStreamBuilder::createSectionMap(Sections);
   DbiBuilder.setSectionMap(SectionMap);
 
+  // It's not entirely clear what this is, but the * Linker * module uses it.
+  llvm::SmallString<128> NativePath(Config->PDBPath.begin(),
+                                    Config->PDBPath.end());
+  llvm::sys::fs::make_absolute(NativePath);
+  llvm::sys::path::native(NativePath, llvm::sys::path::Style::windows);
+  uint32_t PdbFilePathNI = DbiBuilder.addECName(NativePath);
   auto &LinkerModule = ExitOnErr(DbiBuilder.addModuleInfo("* Linker *"));
   LinkerModule.setPdbFilePathNI(PdbFilePathNI);
   addLinkerModuleSymbols(NativePath, LinkerModule, Alloc);
 
   // Add COFF section header stream.
   ExitOnErr(
       DbiBuilder.addDbgStream(pdb::DbgHeaderType::SectionHdr, SectionTable));
 
   // Write to a file.
   ExitOnErr(Builder.commit(Config->PDBPath));
 }