[CodeView] Handle Cross Module Imports and Exports.

While it's not entirely clear why a compiler or linker might
put this information into an object or PDB file, one has been
spotted in the wild which was causing llvm-pdbdump to crash.

This patch adds support for reading-writing these sections.
Since I don't know how to get one of the native tools to
generate this kind of debug info, the only test here is one
in which we feed YAML into the tool to produce a PDB and
then spit out YAML from the resulting PDB and make sure that
it matches.

llvm-svn: 304738

llvm/include/llvm/DebugInfo/CodeView/CodeView.h

@@ -575,6 +575,24 @@ struct FrameData {
   };
 };
 
+// Corresponds to LocalIdAndGlobalIdPair structure.
+// This structure information allows cross-referencing between PDBs.  For
+// example, when a PDB is being built during compilation it is not yet known
+// what other modules may end up in the PDB at link time.  So certain types of
+// IDs may clash between the various compile time PDBs.  For each affected
+// module, a subsection would be put into the PDB containing a mapping from its
+// local IDs to a single ID namespace for all items in the PDB file.
+struct CrossModuleExport {
+  support::ulittle32_t Local;
+  support::ulittle32_t Global;
+};
+
+struct CrossModuleImport {
+  support::ulittle32_t ModuleNameOffset;
+  support::ulittle32_t Count; // Number of elements
+  // support::ulittle32_t ids[Count]; // id from referenced module
+};
+
 enum class CodeViewContainer { ObjectFile, Pdb };
 
 inline uint32_t alignOf(CodeViewContainer Container) {

llvm/include/llvm/DebugInfo/CodeView/DebugCrossExSubsection.h

@@ -0,0 +1,64 @@
+//===- DebugCrossExSubsection.h ---------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_CODEVIEW_DEBUGCROSSEXSUBSECTION_H
+#define LLVM_DEBUGINFO_CODEVIEW_DEBUGCROSSEXSUBSECTION_H
+
+#include "llvm/DebugInfo/CodeView/DebugSubsection.h"
+#include "llvm/Support/BinaryStreamArray.h"
+#include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/Endian.h"
+
+#include <map>
+
+namespace llvm {
+namespace codeview {
+class DebugCrossModuleExportsSubsectionRef final : public DebugSubsectionRef {
+  typedef FixedStreamArray<CrossModuleExport> ReferenceArray;
+  typedef ReferenceArray::Iterator Iterator;
+
+public:
+  DebugCrossModuleExportsSubsectionRef()
+      : DebugSubsectionRef(DebugSubsectionKind::CrossScopeExports) {}
+
+  static bool classof(const DebugSubsectionRef *S) {
+    return S->kind() == DebugSubsectionKind::CrossScopeExports;
+  }
+
+  Error initialize(BinaryStreamReader Reader);
+  Error initialize(BinaryStreamRef Stream);
+
+  Iterator begin() const { return References.begin(); }
+  Iterator end() const { return References.end(); }
+
+private:
+  FixedStreamArray<CrossModuleExport> References;
+};
+
+class DebugCrossModuleExportsSubsection final : public DebugSubsection {
+public:
+  DebugCrossModuleExportsSubsection()
+      : DebugSubsection(DebugSubsectionKind::CrossScopeExports) {}
+
+  static bool classof(const DebugSubsection *S) {
+    return S->kind() == DebugSubsectionKind::CrossScopeExports;
+  }
+
+  void addMapping(uint32_t Local, uint32_t Global);
+
+  uint32_t calculateSerializedSize() const override;
+  Error commit(BinaryStreamWriter &Writer) const override;
+
+private:
+  std::map<uint32_t, uint32_t> Mappings;
+};
+}
+}
+
+#endif

llvm/include/llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h

@@ -0,0 +1,88 @@
+//===- DebugCrossExSubsection.h ---------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_CODEVIEW_DEBUGCROSSIMPSUBSECTION_H
+#define LLVM_DEBUGINFO_CODEVIEW_DEBUGCROSSIMPSUBSECTION_H
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/DebugInfo/CodeView/DebugSubsection.h"
+#include "llvm/Support/BinaryStreamArray.h"
+#include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/Endian.h"
+
+namespace llvm {
+namespace codeview {
+
+struct CrossModuleImportItem {
+  const CrossModuleImport *Header = nullptr;
+  llvm::FixedStreamArray<support::ulittle32_t> Imports;
+};
+}
+}
+
+namespace llvm {
+template <> struct VarStreamArrayExtractor<codeview::CrossModuleImportItem> {
+public:
+  typedef void ContextType;
+
+  static Error extract(BinaryStreamRef Stream, uint32_t &Len,
+                       codeview::CrossModuleImportItem &Item);
+};
+}
+
+namespace llvm {
+namespace codeview {
+class DebugStringTableSubsection;
+
+class DebugCrossModuleImportsSubsectionRef final : public DebugSubsectionRef {
+  typedef VarStreamArray<CrossModuleImportItem> ReferenceArray;
+  typedef ReferenceArray::Iterator Iterator;
+
+public:
+  DebugCrossModuleImportsSubsectionRef()
+      : DebugSubsectionRef(DebugSubsectionKind::CrossScopeImports) {}
+
+  static bool classof(const DebugSubsectionRef *S) {
+    return S->kind() == DebugSubsectionKind::CrossScopeImports;
+  }
+
+  Error initialize(BinaryStreamReader Reader);
+  Error initialize(BinaryStreamRef Stream);
+
+  Iterator begin() const { return References.begin(); }
+  Iterator end() const { return References.end(); }
+
+private:
+  ReferenceArray References;
+};
+
+class DebugCrossModuleImportsSubsection final : public DebugSubsection {
+public:
+  explicit DebugCrossModuleImportsSubsection(
+      DebugStringTableSubsection &Strings)
+      : DebugSubsection(DebugSubsectionKind::CrossScopeImports),
+        Strings(Strings) {}
+
+  static bool classof(const DebugSubsection *S) {
+    return S->kind() == DebugSubsectionKind::CrossScopeImports;
+  }
+
+  void addImport(StringRef Module, uint32_t ImportId);
+
+  uint32_t calculateSerializedSize() const override;
+  Error commit(BinaryStreamWriter &Writer) const override;
+
+private:
+  DebugStringTableSubsection &Strings;
+  StringMap<std::vector<support::ulittle32_t>> Mappings;
+};
+}
+}
+
+#endif

llvm/include/llvm/DebugInfo/CodeView/DebugSubsectionVisitor.h

@@ -20,6 +20,8 @@ namespace codeview {
 class DebugChecksumsSubsectionRef;
 class DebugSubsectionRecord;
 class DebugInlineeLinesSubsectionRef;
+class DebugCrossModuleExportsSubsectionRef;
+class DebugCrossModuleImportsSubsectionRef;
 class DebugLinesSubsectionRef;
 class DebugUnknownSubsectionRef;
 
@@ -42,6 +44,16 @@ public:
     return Error::success();
   }
 
+  virtual Error
+  visitCrossModuleExports(DebugCrossModuleExportsSubsectionRef &CSE) {
+    return Error::success();
+  }
+
+  virtual Error
+  visitCrossModuleImports(DebugCrossModuleImportsSubsectionRef &CSE) {
+    return Error::success();
+  }
+
   virtual Error finished() { return Error::success(); }
 };
 

llvm/include/llvm/ObjectYAML/CodeViewYAMLDebugSections.h

@@ -33,6 +33,11 @@ namespace detail {
 struct YAMLSubsectionBase;
 }
 
+struct YAMLCrossModuleImport {
+  StringRef ModuleName;
+  std::vector<uint32_t> ImportIds;
+};
+
 struct SourceLineEntry {
   uint32_t Offset;
   uint32_t LineStart;

llvm/lib/DebugInfo/CodeView/CMakeLists.txt

@@ -3,11 +3,9 @@ add_llvm_library(LLVMDebugInfoCodeView
   CodeViewRecordIO.cpp
   CVSymbolVisitor.cpp
   CVTypeVisitor.cpp
-  EnumTables.cpp
-  Formatters.cpp
-  LazyRandomTypeCollection.cpp
-  Line.cpp
   DebugChecksumsSubsection.cpp
+  DebugCrossExSubsection.cpp
+  DebugCrossImpSubsection.cpp
   DebugFrameDataSubsection.cpp
   DebugInlineeLinesSubsection.cpp
   DebugLinesSubsection.cpp
@@ -16,6 +14,10 @@ add_llvm_library(LLVMDebugInfoCodeView
   DebugSubsectionRecord.cpp
   DebugSubsectionVisitor.cpp
   DebugSymbolsSubsection.cpp
+  EnumTables.cpp
+  Formatters.cpp
+  LazyRandomTypeCollection.cpp
+  Line.cpp
   RecordSerialization.cpp
   SymbolRecordMapping.cpp
   SymbolDumper.cpp

llvm/lib/DebugInfo/CodeView/DebugCrossExSubsection.cpp

@@ -0,0 +1,49 @@
+//===- DebugCrossExSubsection.cpp -------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/CodeView/DebugCrossExSubsection.h"
+
+#include "llvm/DebugInfo/CodeView/CodeViewError.h"
+
+using namespace llvm;
+using namespace llvm::codeview;
+
+Error DebugCrossModuleExportsSubsectionRef::initialize(
+    BinaryStreamReader Reader) {
+  if (Reader.bytesRemaining() % sizeof(CrossModuleExport) != 0)
+    return make_error<CodeViewError>(
+        cv_error_code::corrupt_record,
+        "Cross Scope Exports section is an invalid size!");
+
+  uint32_t Size = Reader.bytesRemaining() / sizeof(CrossModuleExport);
+  return Reader.readArray(References, Size);
+}
+
+Error DebugCrossModuleExportsSubsectionRef::initialize(BinaryStreamRef Stream) {
+  BinaryStreamReader Reader(Stream);
+  return initialize(Reader);
+}
+
+void DebugCrossModuleExportsSubsection::addMapping(uint32_t Local,
+                                                   uint32_t Global) {
+  Mappings[Local] = Global;
+}
+
+uint32_t DebugCrossModuleExportsSubsection::calculateSerializedSize() const {
+  return Mappings.size() * sizeof(CrossModuleExport);
+}
+
+Error DebugCrossModuleExportsSubsection::commit(
+    BinaryStreamWriter &Writer) const {
+  for (const auto &M : Mappings) {
+    if (auto EC = Writer.writeObject(M))
+      return EC;
+  }
+  return Error::success();
+}

llvm/lib/DebugInfo/CodeView/DebugCrossImpSubsection.cpp

@@ -0,0 +1,91 @@
+//===- DebugCrossImpSubsection.cpp ------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h"
+
+#include "llvm/DebugInfo/CodeView/CodeViewError.h"
+#include "llvm/DebugInfo/CodeView/DebugStringTableSubsection.h"
+
+using namespace llvm;
+using namespace llvm::codeview;
+
+namespace llvm {
+Error VarStreamArrayExtractor<CrossModuleImportItem>::extract(
+    BinaryStreamRef Stream, uint32_t &Len,
+    codeview::CrossModuleImportItem &Item) {
+  BinaryStreamReader Reader(Stream);
+  if (Reader.bytesRemaining() < sizeof(CrossModuleImport))
+    return make_error<CodeViewError>(
+        cv_error_code::insufficient_buffer,
+        "Not enough bytes for a Cross Module Import Header!");
+  if (auto EC = Reader.readObject(Item.Header))
+    return EC;
+  if (Reader.bytesRemaining() < Item.Header->Count * sizeof(uint32_t))
+    return make_error<CodeViewError>(
+        cv_error_code::insufficient_buffer,
+        "Not enough to read specified number of Cross Module References!");
+  if (auto EC = Reader.readArray(Item.Imports, Item.Header->Count))
+    return EC;
+  return Error::success();
+}
+}
+
+Error DebugCrossModuleImportsSubsectionRef::initialize(
+    BinaryStreamReader Reader) {
+  return Reader.readArray(References, Reader.bytesRemaining());
+}
+
+Error DebugCrossModuleImportsSubsectionRef::initialize(BinaryStreamRef Stream) {
+  BinaryStreamReader Reader(Stream);
+  return initialize(Reader);
+}
+
+void DebugCrossModuleImportsSubsection::addImport(StringRef Module,
+                                                  uint32_t ImportId) {
+  Strings.insert(Module);
+  std::vector<support::ulittle32_t> Targets = {support::ulittle32_t(ImportId)};
+  auto Result = Mappings.insert(std::make_pair(Module, Targets));
+  if (!Result.second)
+    Result.first->getValue().push_back(Targets[0]);
+}
+
+uint32_t DebugCrossModuleImportsSubsection::calculateSerializedSize() const {
+  uint32_t Size = 0;
+  for (const auto &Item : Mappings) {
+    Size += sizeof(CrossModuleImport);
+    Size += sizeof(support::ulittle32_t) * Item.second.size();
+  }
+  return Size;
+}
+
+Error DebugCrossModuleImportsSubsection::commit(
+    BinaryStreamWriter &Writer) const {
+  using T = decltype(&*Mappings.begin());
+  std::vector<T> Ids;
+  Ids.reserve(Mappings.size());
+
+  for (const auto &M : Mappings)
+    Ids.push_back(&M);
+
+  std::sort(Ids.begin(), Ids.end(), [this](const T &L1, const T &L2) {
+    return Strings.getStringId(L1->getKey()) <
+           Strings.getStringId(L2->getKey());
+  });
+
+  for (const auto &Item : Ids) {
+    CrossModuleImport Imp;
+    Imp.ModuleNameOffset = Strings.getStringId(Item->getKey());
+    Imp.Count = Item->getValue().size();
+    if (auto EC = Writer.writeObject(Imp))
+      return EC;
+    if (auto EC = Writer.writeArray(makeArrayRef(Item->getValue())))
+      return EC;
+  }
+  return Error::success();
+}

llvm/lib/DebugInfo/CodeView/DebugSubsectionRecord.cpp

@@ -38,6 +38,8 @@ Error DebugSubsectionRecord::initialize(BinaryStreamRef Stream,
   case DebugSubsectionKind::FileChecksums:
   case DebugSubsectionKind::Lines:
   case DebugSubsectionKind::InlineeLines:
+  case DebugSubsectionKind::CrossScopeExports:
+  case DebugSubsectionKind::CrossScopeImports:
     break;
   default:
     llvm_unreachable("Unexpected debug fragment kind!");

llvm/lib/DebugInfo/CodeView/DebugSubsectionVisitor.cpp

@@ -10,6 +10,8 @@
 #include "llvm/DebugInfo/CodeView/DebugSubsectionVisitor.h"
 
 #include "llvm/DebugInfo/CodeView/DebugChecksumsSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossExSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugSubsectionRecord.h"
@@ -44,6 +46,18 @@ Error llvm::codeview::visitDebugSubsection(const DebugSubsectionRecord &R,
       return EC;
     return V.visitInlineeLines(Fragment);
   }
+  case DebugSubsectionKind::CrossScopeExports: {
+    DebugCrossModuleExportsSubsectionRef Section;
+    if (auto EC = Section.initialize(Reader))
+      return EC;
+    return V.visitCrossModuleExports(Section);
+  }
+  case DebugSubsectionKind::CrossScopeImports: {
+    DebugCrossModuleImportsSubsectionRef Section;
+    if (auto EC = Section.initialize(Reader))
+      return EC;
+    return V.visitCrossModuleImports(Section);
+  }
   default: {
     DebugUnknownSubsectionRef Fragment(R.kind(), R.getRecordData());
     return V.visitUnknown(Fragment);

llvm/lib/DebugInfo/PDB/Native/ModuleDebugStream.cpp

@@ -90,14 +90,14 @@ Error ModuleDebugStreamRef::commit() { return Error::success(); }
 
 Expected<codeview::DebugChecksumsSubsectionRef>
 ModuleDebugStreamRef::findChecksumsSubsection() const {
+  codeview::DebugChecksumsSubsectionRef Result;
   for (const auto &SS : subsections()) {
     if (SS.kind() != DebugSubsectionKind::FileChecksums)
       continue;
 
-    codeview::DebugChecksumsSubsectionRef Result;
     if (auto EC = Result.initialize(SS.getRecordData()))
       return std::move(EC);
     return Result;
   }
-  return make_error<RawError>(raw_error_code::no_entry);
+  return Result;
 }

llvm/lib/DebugInfo/PDB/Native/PublicsStream.cpp

@@ -105,10 +105,12 @@ Error PublicsStream::reload() {
                                            "Could not read a thunk map."));
 
   // Something called "section map" follows.
-  if (auto EC = Reader.readArray(SectionOffsets, Header->NumSections))
-    return joinErrors(std::move(EC),
-                      make_error<RawError>(raw_error_code::corrupt_file,
-                                           "Could not read a section map."));
+  if (Reader.bytesRemaining() > 0) {
+    if (auto EC = Reader.readArray(SectionOffsets, Header->NumSections))
+      return joinErrors(std::move(EC),
+                        make_error<RawError>(raw_error_code::corrupt_file,
+                                             "Could not read a section map."));
+  }
 
   if (Reader.bytesRemaining() > 0)
     return make_error<RawError>(raw_error_code::corrupt_file,

llvm/lib/ObjectYAML/CodeViewYAMLDebugSections.cpp

@@ -18,6 +18,8 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/DebugInfo/CodeView/CodeViewError.h"
 #include "llvm/DebugInfo/CodeView/DebugChecksumsSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossExSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugStringTableSubsection.h"
@@ -38,13 +40,19 @@ LLVM_YAML_IS_SEQUENCE_VECTOR(SourceLineBlock)
 LLVM_YAML_IS_SEQUENCE_VECTOR(SourceLineInfo)
 LLVM_YAML_IS_SEQUENCE_VECTOR(InlineeSite)
 LLVM_YAML_IS_SEQUENCE_VECTOR(InlineeInfo)
+LLVM_YAML_IS_SEQUENCE_VECTOR(CrossModuleExport)
+LLVM_YAML_IS_SEQUENCE_VECTOR(YAMLCrossModuleImport)
 LLVM_YAML_IS_SEQUENCE_VECTOR(StringRef)
+LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(uint32_t)
 
 LLVM_YAML_DECLARE_SCALAR_TRAITS(HexFormattedString, false)
 LLVM_YAML_DECLARE_ENUM_TRAITS(DebugSubsectionKind)
 LLVM_YAML_DECLARE_ENUM_TRAITS(FileChecksumKind)
 LLVM_YAML_DECLARE_BITSET_TRAITS(LineFlags)
 
+LLVM_YAML_DECLARE_MAPPING_TRAITS(CrossModuleExport)
+LLVM_YAML_DECLARE_MAPPING_TRAITS(YAMLCrossModuleImport)
+LLVM_YAML_DECLARE_MAPPING_TRAITS(CrossModuleImportItem)
 LLVM_YAML_DECLARE_MAPPING_TRAITS(SourceLineEntry)
 LLVM_YAML_DECLARE_MAPPING_TRAITS(SourceColumnEntry)
 LLVM_YAML_DECLARE_MAPPING_TRAITS(SourceFileChecksumEntry)
@@ -114,6 +122,35 @@ struct YAMLInlineeLinesSubsection : public YAMLSubsectionBase {
 
   InlineeInfo InlineeLines;
 };
+
+struct YAMLCrossModuleExportsSubsection : public YAMLSubsectionBase {
+  YAMLCrossModuleExportsSubsection()
+      : YAMLSubsectionBase(DebugSubsectionKind::CrossScopeExports) {}
+
+  void map(IO &IO) override;
+  std::unique_ptr<DebugSubsection>
+  toCodeViewSubsection(DebugStringTableSubsection *Strings,
+                       DebugChecksumsSubsection *Checksums) const override;
+  static Expected<std::shared_ptr<YAMLCrossModuleExportsSubsection>>
+  fromCodeViewSubsection(const DebugCrossModuleExportsSubsectionRef &Exports);
+
+  std::vector<CrossModuleExport> Exports;
+};
+
+struct YAMLCrossModuleImportsSubsection : public YAMLSubsectionBase {
+  YAMLCrossModuleImportsSubsection()
+      : YAMLSubsectionBase(DebugSubsectionKind::CrossScopeImports) {}
+
+  void map(IO &IO) override;
+  std::unique_ptr<DebugSubsection>
+  toCodeViewSubsection(DebugStringTableSubsection *Strings,
+                       DebugChecksumsSubsection *Checksums) const override;
+  static Expected<std::shared_ptr<YAMLCrossModuleImportsSubsection>>
+  fromCodeViewSubsection(const DebugStringTableSubsectionRef &Strings,
+                         const DebugCrossModuleImportsSubsectionRef &Imports);
+
+  std::vector<YAMLCrossModuleImport> Imports;
+};
 }
 
 void ScalarBitSetTraits<LineFlags>::bitset(IO &io, LineFlags &Flags) {
@@ -161,6 +198,17 @@ void MappingTraits<SourceLineBlock>::mapping(IO &IO, SourceLineBlock &Obj) {
   IO.mapRequired("Columns", Obj.Columns);
 }
 
+void MappingTraits<CrossModuleExport>::mapping(IO &IO, CrossModuleExport &Obj) {
+  IO.mapRequired("LocalId", Obj.Local);
+  IO.mapRequired("GlobalId", Obj.Global);
+}
+
+void MappingTraits<YAMLCrossModuleImport>::mapping(IO &IO,
+                                                   YAMLCrossModuleImport &Obj) {
+  IO.mapRequired("Module", Obj.ModuleName);
+  IO.mapRequired("Imports", Obj.ImportIds);
+}
+
 void MappingTraits<SourceFileChecksumEntry>::mapping(
     IO &IO, SourceFileChecksumEntry &Obj) {
   IO.mapRequired("FileName", Obj.FileName);
@@ -196,6 +244,16 @@ void YAMLInlineeLinesSubsection::map(IO &IO) {
   IO.mapRequired("Sites", InlineeLines.Sites);
 }
 
+void YAMLCrossModuleExportsSubsection::map(IO &IO) {
+  IO.mapTag("!CrossModuleExports", true);
+  IO.mapOptional("Exports", Exports);
+}
+
+void YAMLCrossModuleImportsSubsection::map(IO &IO) {
+  IO.mapTag("!CrossModuleImports", true);
+  IO.mapOptional("Imports", Imports);
+}
+
 void MappingTraits<YAMLDebugSubsection>::mapping(
     IO &IO, YAMLDebugSubsection &Subsection) {
   if (!IO.outputting()) {
@@ -206,6 +264,12 @@ void MappingTraits<YAMLDebugSubsection>::mapping(
       Subsection.Subsection = std::make_shared<YAMLLinesSubsection>();
     } else if (IO.mapTag("!InlineeLines")) {
       Subsection.Subsection = std::make_shared<YAMLInlineeLinesSubsection>();
+    } else if (IO.mapTag("!CrossModuleExports")) {
+      Subsection.Subsection =
+          std::make_shared<YAMLCrossModuleExportsSubsection>();
+    } else if (IO.mapTag("!CrossModuleImports")) {
+      Subsection.Subsection =
+          std::make_shared<YAMLCrossModuleImportsSubsection>();
     } else {
       llvm_unreachable("Unexpected subsection tag!");
     }
@@ -213,14 +277,15 @@ void MappingTraits<YAMLDebugSubsection>::mapping(
   Subsection.Subsection->map(IO);
 }
 
-static Expected<const YAMLChecksumsSubsection &>
+static std::shared_ptr<YAMLChecksumsSubsection>
 findChecksums(ArrayRef<YAMLDebugSubsection> Subsections) {
   for (const auto &SS : Subsections) {
     if (SS.Subsection->Kind == DebugSubsectionKind::FileChecksums) {
-      return static_cast<const YAMLChecksumsSubsection &>(*SS.Subsection);
+      return std::static_pointer_cast<YAMLChecksumsSubsection>(SS.Subsection);
     }
   }
-  return make_error<CodeViewError>(cv_error_code::no_records);
+
+  return nullptr;
 }
 
 std::unique_ptr<DebugSubsection> YAMLChecksumsSubsection::toCodeViewSubsection(
@@ -285,6 +350,28 @@ YAMLInlineeLinesSubsection::toCodeViewSubsection(
   return llvm::cast<DebugSubsection>(std::move(Result));
 }
 
+std::unique_ptr<DebugSubsection>
+YAMLCrossModuleExportsSubsection::toCodeViewSubsection(
+    DebugStringTableSubsection *Strings,
+    DebugChecksumsSubsection *Checksums) const {
+  auto Result = llvm::make_unique<DebugCrossModuleExportsSubsection>();
+  for (const auto &M : Exports)
+    Result->addMapping(M.Local, M.Global);
+  return llvm::cast<DebugSubsection>(std::move(Result));
+}
+
+std::unique_ptr<DebugSubsection>
+YAMLCrossModuleImportsSubsection::toCodeViewSubsection(
+    DebugStringTableSubsection *Strings,
+    DebugChecksumsSubsection *Checksums) const {
+  auto Result = llvm::make_unique<DebugCrossModuleImportsSubsection>(*Strings);
+  for (const auto &M : Imports) {
+    for (const auto Id : M.ImportIds)
+      Result->addImport(M.ModuleName, Id);
+  }
+  return llvm::cast<DebugSubsection>(std::move(Result));
+}
+
 static Expected<SourceFileChecksumEntry>
 convertOneChecksum(const DebugStringTableSubsectionRef &Strings,
                    const FileChecksumEntry &CS) {
@@ -391,6 +478,31 @@ YAMLInlineeLinesSubsection::fromCodeViewSubsection(
   return Result;
 }
 
+Expected<std::shared_ptr<YAMLCrossModuleExportsSubsection>>
+YAMLCrossModuleExportsSubsection::fromCodeViewSubsection(
+    const DebugCrossModuleExportsSubsectionRef &Exports) {
+  auto Result = std::make_shared<YAMLCrossModuleExportsSubsection>();
+  Result->Exports.assign(Exports.begin(), Exports.end());
+  return Result;
+}
+
+Expected<std::shared_ptr<YAMLCrossModuleImportsSubsection>>
+YAMLCrossModuleImportsSubsection::fromCodeViewSubsection(
+    const DebugStringTableSubsectionRef &Strings,
+    const DebugCrossModuleImportsSubsectionRef &Imports) {
+  auto Result = std::make_shared<YAMLCrossModuleImportsSubsection>();
+  for (const auto &CMI : Imports) {
+    YAMLCrossModuleImport YCMI;
+    auto ExpectedStr = Strings.getString(CMI.Header->ModuleNameOffset);
+    if (!ExpectedStr)
+      return ExpectedStr.takeError();
+    YCMI.ModuleName = *ExpectedStr;
+    YCMI.ImportIds.assign(CMI.Imports.begin(), CMI.Imports.end());
+    Result->Imports.push_back(YCMI);
+  }
+  return Result;
+}
+
 Expected<std::vector<std::unique_ptr<DebugSubsection>>>
 llvm::CodeViewYAML::convertSubsectionList(
     ArrayRef<YAMLDebugSubsection> Subsections,
@@ -400,11 +512,11 @@ llvm::CodeViewYAML::convertSubsectionList(
     return std::move(Result);
 
   auto Checksums = findChecksums(Subsections);
-  if (!Checksums)
-    return Checksums.takeError();
-  auto ChecksumsBase = Checksums->toCodeViewSubsection(&Strings, nullptr);
-  DebugChecksumsSubsection &CS =
-      llvm::cast<DebugChecksumsSubsection>(*ChecksumsBase);
+  std::unique_ptr<DebugSubsection> ChecksumsBase;
+  if (Checksums)
+    ChecksumsBase = Checksums->toCodeViewSubsection(&Strings, nullptr);
+  DebugChecksumsSubsection *CS =
+      static_cast<DebugChecksumsSubsection *>(ChecksumsBase.get());
   for (const auto &SS : Subsections) {
     // We've already converted the checksums subsection, don't do it
     // twice.
@@ -412,7 +524,8 @@ llvm::CodeViewYAML::convertSubsectionList(
     if (SS.Subsection->Kind == DebugSubsectionKind::FileChecksums)
       CVS = std::move(ChecksumsBase);
     else
-      CVS = SS.Subsection->toCodeViewSubsection(&Strings, &CS);
+      CVS = SS.Subsection->toCodeViewSubsection(&Strings, CS);
+    assert(CVS != nullptr);
     Result.push_back(std::move(CVS));
   }
   return std::move(Result);
@@ -429,6 +542,10 @@ struct SubsectionConversionVisitor : public DebugSubsectionVisitor {
   Error visitLines(DebugLinesSubsectionRef &Lines) override;
   Error visitFileChecksums(DebugChecksumsSubsectionRef &Checksums) override;
   Error visitInlineeLines(DebugInlineeLinesSubsectionRef &Inlinees) override;
+  Error visitCrossModuleExports(
+      DebugCrossModuleExportsSubsectionRef &Checksums) override;
+  Error visitCrossModuleImports(
+      DebugCrossModuleImportsSubsectionRef &Inlinees) override;
 
   YAMLDebugSubsection Subsection;
 
@@ -470,6 +587,26 @@ Error SubsectionConversionVisitor::visitInlineeLines(
   Subsection.Subsection = *Result;
   return Error::success();
 }
+
+Error SubsectionConversionVisitor::visitCrossModuleExports(
+    DebugCrossModuleExportsSubsectionRef &Exports) {
+  auto Result =
+      YAMLCrossModuleExportsSubsection::fromCodeViewSubsection(Exports);
+  if (!Result)
+    return Result.takeError();
+  Subsection.Subsection = *Result;
+  return Error::success();
+}
+
+Error SubsectionConversionVisitor::visitCrossModuleImports(
+    DebugCrossModuleImportsSubsectionRef &Imports) {
+  auto Result = YAMLCrossModuleImportsSubsection::fromCodeViewSubsection(
+      Strings, Imports);
+  if (!Result)
+    return Result.takeError();
+  Subsection.Subsection = *Result;
+  return Error::success();
+}
 }
 
 Expected<YAMLDebugSubsection> YAMLDebugSubsection::fromCodeViewSubection(

llvm/lib/ObjectYAML/CodeViewYAMLSymbols.cpp

@@ -47,6 +47,18 @@ LLVM_YAML_DECLARE_ENUM_TRAITS(RegisterId)
 LLVM_YAML_DECLARE_ENUM_TRAITS(TrampolineType)
 LLVM_YAML_DECLARE_ENUM_TRAITS(ThunkOrdinal)
 
+LLVM_YAML_STRONG_TYPEDEF(llvm::StringRef, TypeName)
+
+LLVM_YAML_DECLARE_SCALAR_TRAITS(TypeName, true)
+
+StringRef ScalarTraits<TypeName>::input(StringRef S, void *V, TypeName &T) {
+  return ScalarTraits<StringRef>::input(S, V, T.value);
+}
+void ScalarTraits<TypeName>::output(const TypeName &T, void *V,
+                                    llvm::raw_ostream &R) {
+  ScalarTraits<StringRef>::output(T.value, V, R);
+}
+
 void ScalarEnumerationTraits<SymbolKind>::enumeration(IO &io,
                                                       SymbolKind &Value) {
   auto SymbolNames = getSymbolTypeNames();
@@ -264,6 +276,7 @@ template <> void SymbolRecordImpl<InlineSiteSym>::map(IO &IO) {
 template <> void SymbolRecordImpl<LocalSym>::map(IO &IO) {
   IO.mapRequired("Type", Symbol.Type);
   IO.mapRequired("Flags", Symbol.Flags);
+
   IO.mapRequired("VarName", Symbol.Name);
 }
 

llvm/test/DebugInfo/PDB/Inputs/cross-module-import-export.yaml

@@ -0,0 +1,24 @@
+DbiStream:       
+  Modules:         
+    - Module:          'Foo.obj'
+      ObjFile:         'Foo.obj'
+      Subsections:     
+        - !CrossModuleExports
+          Exports:         
+            - LocalId:         4852
+              GlobalId:        9283
+            - LocalId:         2147487875
+              GlobalId:        9123
+    - Module:          'Bar.obj'
+      ObjFile:         'Bar.obj'
+      Subsections:     
+        - !CrossModuleExports
+          Exports:         
+            - LocalId:         4265
+              GlobalId:        6097
+            - LocalId:         4297
+              GlobalId:        4677
+        - !CrossModuleImports
+          Imports:         
+            - Module:          'Foo.obj'
+              Imports:         [ 4852, 2147487875 ]

llvm/test/DebugInfo/PDB/cross-module-import-export.test

@@ -0,0 +1,60 @@
+; RUN: llvm-pdbdump yaml2pdb -pdb=%t.pdb %p/Inputs/cross-module-import-export.yaml
+
+; RUN: llvm-pdbdump pdb2yaml -all -no-file-headers %t.pdb | FileCheck --check-prefix=YAML %s
+; RUN: llvm-pdbdump raw -all %t.pdb | FileCheck --check-prefix=RAW %s
+
+YAML:      Modules:
+YAML-NEXT:   - Module:          Foo.obj
+YAML-NEXT:     ObjFile:         Foo.obj
+YAML-NEXT:     Subsections:
+YAML-NEXT:       - !CrossModuleExports
+YAML-NEXT:         Exports:
+YAML-NEXT:           - LocalId:         4852
+YAML-NEXT:             GlobalId:        9283
+YAML-NEXT:           - LocalId:         2147487875
+YAML-NEXT:             GlobalId:        9123
+YAML:        - Module:          Bar.obj
+YAML-NEXT:     ObjFile:         Bar.obj
+YAML-NEXT:     Subsections:
+YAML-NEXT:       - !CrossModuleExports
+YAML-NEXT:         Exports:
+YAML-NEXT:           - LocalId:         4265
+YAML-NEXT:             GlobalId:        6097
+YAML-NEXT:           - LocalId:         4297
+YAML-NEXT:             GlobalId:        4677
+YAML-NEXT:       - !CrossModuleImports
+YAML-NEXT:         Imports:
+YAML-NEXT:           - Module:          Foo.obj
+YAML-NEXT:             Imports:         [ 4852, 2147487875 ]
+
+
+RAW:      DBI Stream {
+RAW:        Modules [
+RAW-NEXT:     {
+RAW-NEXT:       Name: Foo.obj
+RAW:            LineInfo [
+RAW-NEXT:         CrossModuleExports {
+RAW-NEXT:           Local: 0x12F4
+RAW-NEXT:           Global: 0x2443
+RAW-NEXT:           Local: 0x80001083
+RAW-NEXT:           Global: 0x23A3
+RAW-NEXT:         }
+RAW-NEXT:       ]
+RAW-NEXT:     }
+RAW-NEXT:     {
+RAW-NEXT:       Name: Bar.obj
+RAW:            LineInfo [
+RAW-NEXT:         CrossModuleExports {
+RAW-NEXT:           Local: 0x10A9
+RAW-NEXT:           Global: 0x17D1
+RAW-NEXT:           Local: 0x10C9
+RAW-NEXT:           Global: 0x1245
+RAW-NEXT:         }
+RAW-NEXT:         CrossModuleImports {
+RAW-NEXT:           Module: Foo.obj
+RAW-NEXT:           Imports: [0x12F4, 0x80001083]
+RAW-NEXT:         }
+RAW-NEXT:       ]
+RAW-NEXT:     }
+RAW-NEXT:   ]
+RAW-NEXT: }

llvm/tools/llvm-pdbdump/C13DebugFragmentVisitor.cpp

@@ -10,6 +10,8 @@
 #include "C13DebugFragmentVisitor.h"
 
 #include "llvm/DebugInfo/CodeView/DebugChecksumsSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossExSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugLinesSubsection.h"
 #include "llvm/DebugInfo/PDB/Native/PDBFile.h"
@@ -48,18 +50,34 @@ Error C13DebugFragmentVisitor::visitInlineeLines(
   return Error::success();
 }
 
+Error C13DebugFragmentVisitor::visitCrossModuleExports(
+    codeview::DebugCrossModuleExportsSubsectionRef &Exports) {
+  this->CrossExports.push_back(Exports);
+  return Error::success();
+}
+
+Error C13DebugFragmentVisitor::visitCrossModuleImports(
+    codeview::DebugCrossModuleImportsSubsectionRef &Imports) {
+  this->CrossImports.push_back(Imports);
+  return Error::success();
+}
+
 Error C13DebugFragmentVisitor::finished() {
-  if (!Checksums.hasValue()) {
-    assert(Lines.empty());
-    return Error::success();
+  if (Checksums.hasValue()) {
+    if (auto EC = handleFileChecksums())
+      return EC;
+
+    if (auto EC = handleLines())
+      return EC;
+
+    if (auto EC = handleInlineeLines())
+      return EC;
   }
-  if (auto EC = handleFileChecksums())
+
+  if (auto EC = handleCrossModuleExports())
     return EC;
 
-  if (auto EC = handleLines())
-    return EC;
-
-  if (auto EC = handleInlineeLines())
+  if (auto EC = handleCrossModuleImports())
     return EC;
 
   return Error::success();

llvm/tools/llvm-pdbdump/C13DebugFragmentVisitor.h

@@ -38,12 +38,20 @@ public:
   Error
   visitInlineeLines(codeview::DebugInlineeLinesSubsectionRef &Lines) final;
 
+  Error visitCrossModuleExports(
+      codeview::DebugCrossModuleExportsSubsectionRef &Lines) final;
+
+  Error visitCrossModuleImports(
+      codeview::DebugCrossModuleImportsSubsectionRef &Imports) final;
+
   Error finished() final;
 
 protected:
   virtual Error handleFileChecksums() { return Error::success(); }
   virtual Error handleLines() { return Error::success(); }
   virtual Error handleInlineeLines() { return Error::success(); }
+  virtual Error handleCrossModuleExports() { return Error::success(); }
+  virtual Error handleCrossModuleImports() { return Error::success(); }
 
   Expected<StringRef> getNameFromStringTable(uint32_t Offset);
   Expected<StringRef> getNameFromChecksumsBuffer(uint32_t Offset);
@@ -51,6 +59,8 @@ protected:
   Optional<codeview::DebugChecksumsSubsectionRef> Checksums;
   std::vector<codeview::DebugInlineeLinesSubsectionRef> InlineeLines;
   std::vector<codeview::DebugLinesSubsectionRef> Lines;
+  std::vector<codeview::DebugCrossModuleExportsSubsectionRef> CrossExports;
+  std::vector<codeview::DebugCrossModuleImportsSubsectionRef> CrossImports;
 
   PDBFile &F;
 };

llvm/tools/llvm-pdbdump/LLVMOutputStyle.cpp

@@ -16,6 +16,8 @@
 
 #include "llvm/DebugInfo/CodeView/CVTypeVisitor.h"
 #include "llvm/DebugInfo/CodeView/DebugChecksumsSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossExSubsection.h"
+#include "llvm/DebugInfo/CodeView/DebugCrossImpSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugSubsectionVisitor.h"
@@ -174,6 +176,32 @@ public:
     return Error::success();
   }
 
+  Error handleCrossModuleExports() override {
+    for (const auto &M : CrossExports) {
+      DictScope D(P, "CrossModuleExports");
+      for (const auto &E : M) {
+        P.printHex("Local", E.Local);
+        P.printHex("Global", E.Global);
+      }
+    }
+    return Error::success();
+  }
+
+  Error handleCrossModuleImports() override {
+    for (const auto &M : CrossImports) {
+      DictScope D(P, "CrossModuleImports");
+      for (const auto &ImportGroup : M) {
+        auto Name =
+            getNameFromStringTable(ImportGroup.Header->ModuleNameOffset);
+        if (!Name)
+          return Name.takeError();
+        P.printString("Module", *Name);
+        P.printHexList("Imports", ImportGroup.Imports);
+      }
+    }
+    return Error::success();
+  }
+
 private:
   Error dumpTypeRecord(StringRef Label, TypeIndex Index) {
     CompactTypeDumpVisitor CTDV(IPI, Index, &P);

llvm/tools/llvm-pdbdump/YAMLOutputStyle.cpp

@@ -17,7 +17,6 @@
 #include "llvm/DebugInfo/CodeView/DebugInlineeLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugLinesSubsection.h"
 #include "llvm/DebugInfo/CodeView/DebugSubsection.h"
-#include "llvm/DebugInfo/CodeView/DebugSubsectionVisitor.h"
 #include "llvm/DebugInfo/CodeView/DebugUnknownSubsection.h"
 #include "llvm/DebugInfo/CodeView/Line.h"
 #include "llvm/DebugInfo/MSF/MappedBlockStream.h"