[llvm-dsymutil] Add support for __swift_ast MachO DWARF section

Summary:
Xcode's dsymutil emits a __swift_ast DWARF section, which is required for debugging,
and which contains a byte-for-byte dump of the swiftmodule file.
Add this feature to llvm-dsymutil.

Tested with `gobjdump --dwarf=info -s`, by verifying that the contents of
`__DWARF.__swift_ast` match between Xcode's dsymutil and llvm-dsymutil
(Xcode's dwarfdump and llvm-dwarfdump don't currently recognize the
__swift_ast section).

Reviewers: aprantl, friss

Subscribers: llvm-commits, JDevlieghere

Differential Revision: https://reviews.llvm.org/D38504

llvm-svn: 315004

llvm/include/llvm/MC/MCObjectFileInfo.h

@@ -123,6 +123,9 @@ protected:
   /// Section for newer gnu pubtypes.
   MCSection *DwarfGnuPubTypesSection;
 
+  // Section for Swift AST
+  MCSection *DwarfSwiftASTSection;
+
   MCSection *COFFDebugSymbolsSection;
   MCSection *COFFDebugTypesSection;
 
@@ -267,6 +270,7 @@ public:
   MCSection *getDwarfAddrSection() const { return DwarfAddrSection; }
   MCSection *getDwarfCUIndexSection() const { return DwarfCUIndexSection; }
   MCSection *getDwarfTUIndexSection() const { return DwarfTUIndexSection; }
+  MCSection *getDwarfSwiftASTSection() const { return DwarfSwiftASTSection; }
 
   MCSection *getCOFFDebugSymbolsSection() const {
     return COFFDebugSymbolsSection;

llvm/lib/MC/MCObjectFileInfo.cpp

@@ -214,6 +214,10 @@ void MCObjectFileInfo::initMachOMCObjectFileInfo(const Triple &T) {
       Ctx->getMachOSection("__DWARF", "__apple_types", MachO::S_ATTR_DEBUG,
                            SectionKind::getMetadata(), "types_begin");
 
+  DwarfSwiftASTSection =
+      Ctx->getMachOSection("__DWARF", "__swift_ast", MachO::S_ATTR_DEBUG,
+                           SectionKind::getMetadata());
+
   DwarfAbbrevSection =
       Ctx->getMachOSection("__DWARF", "__debug_abbrev", MachO::S_ATTR_DEBUG,
                            SectionKind::getMetadata(), "section_abbrev");

llvm/test/tools/dsymutil/Inputs/swift-ast.swiftmodule

@@ -0,0 +1 @@
+SWIFTMODULE DATA

llvm/test/tools/dsymutil/swift-ast.test

@@ -0,0 +1,14 @@
+RUN: llvm-dsymutil -oso-prepend-path %p %p/Inputs/swift-ast -o %T/swift-ast.dSYM -verbose | FileCheck %s --check-prefix=DSYMUTIL
+RUN: llvm-readobj -sections -section-data %T/swift-ast.dSYM/Contents/Resources/DWARF/swift-ast | FileCheck %s --check-prefix=READOBJ
+
+The tested object file has been created by the dummy Swift code:
+let x = 1
+
+Compiled with: swiftc /tmp/test.swift -Onone -target x86_64-apple-macosx10.9 -c
+Linked with: ld swift-ast.o -add_ast_path Inputs/swift-ast.swiftmodule -arch x86_64 -lSystem -macosx_version_min 10.9.0
+
+DSYMUTIL: filename:{{.*}}swift-ast.swiftmodule
+DSYMUTIL: DEBUG MAP OBJECT:{{.*}}swift-ast.swiftmodule
+
+READOBJ: Name:{{.*}}__swift_ast
+READOBJ: |SWIFTMODULE DATA|

llvm/tools/dsymutil/BinaryHolder.h

@@ -66,6 +66,12 @@ class BinaryHolder {
   MapArchiveAndGetMemberBuffers(StringRef Filename,
                                 sys::TimePoint<std::chrono::seconds> Timestamp);
 
+  void changeBackingMemoryBuffer(std::unique_ptr<MemoryBuffer> &&MemBuf);
+  ErrorOr<const object::ObjectFile &> getObjfileForArch(const Triple &T);
+
+public:
+  BinaryHolder(bool Verbose) : Verbose(Verbose) {}
+
   /// Return the MemoryBufferRef that holds the memory mapping for the
   /// given \p Filename. This function will try to parse archive
   /// member specifications of the form /path/to/archive.a(member.o).
@@ -79,12 +85,6 @@ class BinaryHolder {
   GetMemoryBuffersForFile(StringRef Filename,
                           sys::TimePoint<std::chrono::seconds> Timestamp);
 
-  void changeBackingMemoryBuffer(std::unique_ptr<MemoryBuffer> &&MemBuf);
-  ErrorOr<const object::ObjectFile &> getObjfileForArch(const Triple &T);
-
-public:
-  BinaryHolder(bool Verbose) : Verbose(Verbose) {}
-
   /// Get the ObjectFiles designated by the \p Filename. This
   /// might be an archive member specification of the form
   /// /path/to/archive.a(member.o).

llvm/tools/dsymutil/DebugMap.cpp

@@ -21,8 +21,9 @@ namespace dsymutil {
 using namespace llvm::object;
 
 DebugMapObject::DebugMapObject(StringRef ObjectFilename,
-                               sys::TimePoint<std::chrono::seconds> Timestamp)
-    : Filename(ObjectFilename), Timestamp(Timestamp) {}
+                               sys::TimePoint<std::chrono::seconds> Timestamp,
+                               uint8_t Type)
+    : Filename(ObjectFilename), Timestamp(Timestamp), Type(Type) {}
 
 bool DebugMapObject::addSymbol(StringRef Name, Optional<uint64_t> ObjectAddress,
                                uint64_t LinkedAddress, uint32_t Size) {
@@ -64,8 +65,9 @@ void DebugMapObject::dump() const { print(errs()); }
 
 DebugMapObject &
 DebugMap::addDebugMapObject(StringRef ObjectFilePath,
-                            sys::TimePoint<std::chrono::seconds> Timestamp) {
-  Objects.emplace_back(new DebugMapObject(ObjectFilePath, Timestamp));
+                            sys::TimePoint<std::chrono::seconds> Timestamp,
+                            uint8_t Type) {
+  Objects.emplace_back(new DebugMapObject(ObjectFilePath, Timestamp, Type));
   return *Objects.back();
 }
 
@@ -241,7 +243,7 @@ MappingTraits<dsymutil::DebugMapObject>::YamlDMO::denormalize(IO &IO) {
     }
   }
 
-  dsymutil::DebugMapObject Res(Path, sys::toTimePoint(Timestamp));
+  dsymutil::DebugMapObject Res(Path, sys::toTimePoint(Timestamp), MachO::N_OSO);
   for (auto &Entry : Entries) {
     auto &Mapping = Entry.second;
     Optional<uint64_t> ObjAddress;

llvm/tools/dsymutil/DebugMap.h

@@ -94,7 +94,8 @@ public:
   /// debug map.
   DebugMapObject &
   addDebugMapObject(StringRef ObjectFilePath,
-                    sys::TimePoint<std::chrono::seconds> Timestamp);
+                    sys::TimePoint<std::chrono::seconds> Timestamp,
+                    uint8_t Type);
 
   const Triple &getTriple() const { return BinaryTriple; }
 
@@ -154,6 +155,8 @@ public:
     return Timestamp;
   }
 
+  uint8_t getType() const { return Type; }
+
   iterator_range<StringMap<SymbolMapping>::const_iterator> symbols() const {
     return make_range(Symbols.begin(), Symbols.end());
   }
@@ -166,12 +169,13 @@ private:
   friend class DebugMap;
   /// DebugMapObjects can only be constructed by the owning DebugMap.
   DebugMapObject(StringRef ObjectFilename,
-                 sys::TimePoint<std::chrono::seconds> Timestamp);
+                 sys::TimePoint<std::chrono::seconds> Timestamp, uint8_t Type);
 
   std::string Filename;
   sys::TimePoint<std::chrono::seconds> Timestamp;
   StringMap<SymbolMapping> Symbols;
   DenseMap<uint64_t, DebugMapEntry *> AddressToMapping;
+  uint8_t Type;
 
   /// For YAMLIO support.
   ///@{

llvm/tools/dsymutil/DwarfLinker.cpp

@@ -525,6 +525,9 @@ public:
   /// Emit the string table described by \p Pool.
   void emitStrings(const NonRelocatableStringpool &Pool);
 
+  /// Emit the swift_ast section stored in \p Buffers.
+  void emitSwiftAST(const std::vector<MemoryBufferRef> &Buffers);
+
   /// Emit debug_ranges for \p FuncRange by translating the
   /// original \p Entries.
   void emitRangesEntries(
@@ -708,6 +711,15 @@ void DwarfStreamer::emitStrings(const NonRelocatableStringpool &Pool) {
         StringRef(Entry->getKey().data(), Entry->getKey().size() + 1));
 }
 
+/// Emit the swift_ast section stored in \p Buffers.
+void DwarfStreamer::emitSwiftAST(const std::vector<MemoryBufferRef> &Buffers) {
+  MCSection *SwiftASTSection = MOFI->getDwarfSwiftASTSection();
+  SwiftASTSection->setAlignment(1 << 5);
+  MS->SwitchSection(SwiftASTSection);
+  for (auto Buf : Buffers)
+    MS->EmitBytes(Buf.getBuffer());
+}
+
 /// Emit the debug_range section contents for \p FuncRange by
 /// translating the original \p Entries. The debug_range section
 /// format is totally trivial, consisting just of pairs of address
@@ -3329,8 +3341,8 @@ void DwarfLinker::loadClangModule(StringRef Filename, StringRef ModulePath,
   else
     sys::path::append(Path, Filename);
   BinaryHolder ObjHolder(Options.Verbose);
-  auto &Obj =
-      ModuleMap.addDebugMapObject(Path, sys::TimePoint<std::chrono::seconds>());
+  auto &Obj = ModuleMap.addDebugMapObject(
+      Path, sys::TimePoint<std::chrono::seconds>(), MachO::N_OSO);
   auto ErrOrObj = loadObject(ObjHolder, Obj, ModuleMap);
   if (!ErrOrObj) {
     // Try and emit more helpful warnings by applying some heuristics.
@@ -3475,6 +3487,19 @@ bool DwarfLinker::link(const DebugMap &Map) {
 
     if (Options.Verbose)
       outs() << "DEBUG MAP OBJECT: " << Obj->getObjectFilename() << "\n";
+
+    // N_AST objects (swiftmodule files) should get dumped directly into the
+    // appropriate DWARF section.
+    if (Obj->getType() == MachO::N_AST) {
+      auto ErrOrMemBufferRefs = BinHolder.GetMemoryBuffersForFile(
+          Obj->getObjectFilename(), Obj->getTimestamp());
+      if (auto Err = ErrOrMemBufferRefs.getError())
+        continue;
+      if (!Options.NoOutput)
+        Streamer->emitSwiftAST(ErrOrMemBufferRefs.get());
+      continue;
+    }
+
     auto ErrOrObj = loadObject(BinHolder, *Obj, Map);
     if (!ErrOrObj)
       continue;

llvm/tools/dsymutil/MachODebugMapParser.cpp

@@ -135,7 +135,8 @@ void MachODebugMapParser::switchToNewDebugMapObject(
                    Err.message() + "\n");
   }
 
-  CurrentDebugMapObject = &Result->addDebugMapObject(Path, Timestamp);
+  CurrentDebugMapObject =
+      &Result->addDebugMapObject(Path, Timestamp, MachO::N_OSO);
   loadCurrentObjectFileSymbols(*ErrOrAchObj);
 }
 
@@ -349,6 +350,13 @@ void MachODebugMapParser::handleStabSymbolTableEntry(uint32_t StringIndex,
   if (Type == MachO::N_OSO)
     return switchToNewDebugMapObject(Name, sys::toTimePoint(Value));
 
+  if (Type == MachO::N_AST) {
+    SmallString<80> Path(PathPrefix);
+    sys::path::append(Path, Name);
+    Result->addDebugMapObject(Path, sys::toTimePoint(Value), Type);
+    return;
+  }
+
   // If the last N_OSO object file wasn't found,
   // CurrentDebugMapObject will be null. Do not update anything
   // until we find the next valid N_OSO entry.