vendor/lld/lld-trunk-r233088

1 files changed, 969 insertions, 0 deletions

diff --git a/lib/ReaderWriter/MachO/MachOLinkingContext.cpp b/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
new file mode 100644
index 000000000000..92385cf3e820
--- /dev/null
+++ b/lib/ReaderWriter/MachO/MachOLinkingContext.cpp
@@ -0,0 +1,969 @@
+//===- lib/ReaderWriter/MachO/MachOLinkingContext.cpp ---------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "lld/ReaderWriter/MachOLinkingContext.h"
+#include "ArchHandler.h"
+#include "File.h"
+#include "MachONormalizedFile.h"
+#include "MachOPasses.h"
+#include "lld/Core/ArchiveLibraryFile.h"
+#include "lld/Core/PassManager.h"
+#include "lld/Core/Reader.h"
+#include "lld/Core/Writer.h"
+#include "lld/Driver/Driver.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Host.h"
+#include "llvm/Support/MachO.h"
+#include "llvm/Support/Path.h"
+#include <algorithm>
+
+#if defined(HAVE_CXXABI_H)
+#include <cxxabi.h>
+#endif
+
+using lld::mach_o::ArchHandler;
+using lld::mach_o::MachODylibFile;
+using namespace llvm::MachO;
+
+namespace lld {
+
+bool MachOLinkingContext::parsePackedVersion(StringRef str, uint32_t &result) {
+  result = 0;
+
+  if (str.empty())
+    return false;
+
+  SmallVector<StringRef, 3> parts;
+  llvm::SplitString(str, parts, ".");
+
+  unsigned long long num;
+  if (llvm::getAsUnsignedInteger(parts[0], 10, num))
+    return true;
+  if (num > 65535)
+    return true;
+  result = num << 16;
+
+  if (parts.size() > 1) {
+    if (llvm::getAsUnsignedInteger(parts[1], 10, num))
+      return true;
+    if (num > 255)
+      return true;
+    result |= (num << 8);
+  }
+
+  if (parts.size() > 2) {
+    if (llvm::getAsUnsignedInteger(parts[2], 10, num))
+      return true;
+    if (num > 255)
+      return true;
+    result |= num;
+  }
+
+  return false;
+}
+
+
+MachOLinkingContext::ArchInfo MachOLinkingContext::_s_archInfos[] = {
+  { "x86_64", arch_x86_64, true,  CPU_TYPE_X86_64,  CPU_SUBTYPE_X86_64_ALL },
+  { "i386",   arch_x86,    true,  CPU_TYPE_I386,    CPU_SUBTYPE_X86_ALL },
+  { "ppc",    arch_ppc,    false, CPU_TYPE_POWERPC, CPU_SUBTYPE_POWERPC_ALL },
+  { "armv6",  arch_armv6,  true,  CPU_TYPE_ARM,     CPU_SUBTYPE_ARM_V6 },
+  { "armv7",  arch_armv7,  true,  CPU_TYPE_ARM,     CPU_SUBTYPE_ARM_V7 },
+  { "armv7s", arch_armv7s, true,  CPU_TYPE_ARM,     CPU_SUBTYPE_ARM_V7S },
+  { "arm64",  arch_arm64,  true,  CPU_TYPE_ARM64,   CPU_SUBTYPE_ARM64_ALL },
+  { "",       arch_unknown,false, 0,                0 }
+};
+
+MachOLinkingContext::Arch
+MachOLinkingContext::archFromCpuType(uint32_t cputype, uint32_t cpusubtype) {
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if ((info->cputype == cputype) && (info->cpusubtype == cpusubtype))
+      return info->arch;
+  }
+  return arch_unknown;
+}
+
+MachOLinkingContext::Arch
+MachOLinkingContext::archFromName(StringRef archName) {
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->archName.equals(archName))
+      return info->arch;
+  }
+  return arch_unknown;
+}
+
+StringRef MachOLinkingContext::nameFromArch(Arch arch) {
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch)
+      return info->archName;
+  }
+  return "<unknown>";
+}
+
+uint32_t MachOLinkingContext::cpuTypeFromArch(Arch arch) {
+  assert(arch != arch_unknown);
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch)
+      return info->cputype;
+  }
+  llvm_unreachable("Unknown arch type");
+}
+
+uint32_t MachOLinkingContext::cpuSubtypeFromArch(Arch arch) {
+  assert(arch != arch_unknown);
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch)
+      return info->cpusubtype;
+  }
+  llvm_unreachable("Unknown arch type");
+}
+
+bool MachOLinkingContext::isThinObjectFile(StringRef path, Arch &arch) {
+  return mach_o::normalized::isThinObjectFile(path, arch);
+}
+
+bool MachOLinkingContext::sliceFromFatFile(const MemoryBuffer &mb,
+                                           uint32_t &offset,
+                                           uint32_t &size) {
+  return mach_o::normalized::sliceFromFatFile(mb, _arch, offset, size);
+}
+
+MachOLinkingContext::MachOLinkingContext()
+    : _outputMachOType(MH_EXECUTE), _outputMachOTypeStatic(false),
+      _doNothing(false), _pie(false), _arch(arch_unknown), _os(OS::macOSX),
+      _osMinVersion(0), _pageZeroSize(0), _pageSize(4096), _baseAddress(0),
+      _compatibilityVersion(0), _currentVersion(0), _deadStrippableDylib(false),
+      _printAtoms(false), _testingFileUsage(false), _keepPrivateExterns(false),
+      _demangle(false), _archHandler(nullptr),
+      _exportMode(ExportMode::globals),
+      _debugInfoMode(DebugInfoMode::addDebugMap), _orderFileEntries(0) {}
+
+MachOLinkingContext::~MachOLinkingContext() {}
+
+void MachOLinkingContext::configure(HeaderFileType type, Arch arch, OS os,
+                                    uint32_t minOSVersion) {
+  _outputMachOType = type;
+  _arch = arch;
+  _os = os;
+  _osMinVersion = minOSVersion;
+
+  // If min OS not specified on command line, use reasonable defaults.
+  if (minOSVersion == 0) {
+    switch (_arch) {
+    case arch_x86_64:
+    case arch_x86:
+      parsePackedVersion("10.8", _osMinVersion);
+      _os = MachOLinkingContext::OS::macOSX;
+      break;
+    case arch_armv6:
+    case arch_armv7:
+    case arch_armv7s:
+    case arch_arm64:
+      parsePackedVersion("7.0", _osMinVersion);
+      _os = MachOLinkingContext::OS::iOS;
+      break;
+    default:
+      break;
+    }
+  }
+
+  switch (_outputMachOType) {
+  case llvm::MachO::MH_EXECUTE:
+    // If targeting newer OS, use _main
+    if (minOS("10.8", "6.0")) {
+      _entrySymbolName = "_main";
+    } else {
+      // If targeting older OS, use start (in crt1.o)
+      _entrySymbolName = "start";
+    }
+
+    // __PAGEZERO defaults to 4GB on 64-bit (except for PP64 which lld does not
+    // support) and 4KB on 32-bit.
+    if (is64Bit(_arch)) {
+      _pageZeroSize = 0x100000000;
+    } else {
+      _pageZeroSize = 0x1000;
+    }
+
+    // Make PIE by default when targetting newer OSs.
+    switch (os) {
+      case OS::macOSX:
+        if (minOSVersion >= 0x000A0700) // MacOSX 10.7
+          _pie = true;
+        break;
+      case OS::iOS:
+        if (minOSVersion >= 0x00040300) // iOS 4.3
+          _pie = true;
+       break;
+       case OS::iOS_simulator:
+        _pie = true;
+       break;
+       case OS::unknown:
+       break;
+    }
+    break;
+  case llvm::MachO::MH_DYLIB:
+    setGlobalsAreDeadStripRoots(true);
+    break;
+  case llvm::MachO::MH_BUNDLE:
+    break;
+  case llvm::MachO::MH_OBJECT:
+    _printRemainingUndefines = false;
+    _allowRemainingUndefines = true;
+  default:
+    break;
+  }
+
+  // Set default segment page sizes based on arch.
+  if (arch == arch_arm64)
+    _pageSize = 4*4096;
+}
+
+uint32_t MachOLinkingContext::getCPUType() const {
+  return cpuTypeFromArch(_arch);
+}
+
+uint32_t MachOLinkingContext::getCPUSubType() const {
+  return cpuSubtypeFromArch(_arch);
+}
+
+bool MachOLinkingContext::is64Bit(Arch arch) {
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch) {
+      return (info->cputype & CPU_ARCH_ABI64);
+    }
+  }
+  // unknown archs are not 64-bit.
+  return false;
+}
+
+bool MachOLinkingContext::isHostEndian(Arch arch) {
+  assert(arch != arch_unknown);
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch) {
+      return (info->littleEndian == llvm::sys::IsLittleEndianHost);
+    }
+  }
+  llvm_unreachable("Unknown arch type");
+}
+
+bool MachOLinkingContext::isBigEndian(Arch arch) {
+  assert(arch != arch_unknown);
+  for (ArchInfo *info = _s_archInfos; !info->archName.empty(); ++info) {
+    if (info->arch == arch) {
+      return ! info->littleEndian;
+    }
+  }
+  llvm_unreachable("Unknown arch type");
+}
+
+
+
+bool MachOLinkingContext::is64Bit() const {
+  return is64Bit(_arch);
+}
+
+bool MachOLinkingContext::outputTypeHasEntry() const {
+  switch (_outputMachOType) {
+  case MH_EXECUTE:
+  case MH_DYLINKER:
+  case MH_PRELOAD:
+    return true;
+  default:
+    return false;
+  }
+}
+
+bool MachOLinkingContext::needsStubsPass() const {
+  switch (_outputMachOType) {
+  case MH_EXECUTE:
+    return !_outputMachOTypeStatic;
+  case MH_DYLIB:
+  case MH_BUNDLE:
+    return true;
+  default:
+    return false;
+  }
+}
+
+bool MachOLinkingContext::needsGOTPass() const {
+  // GOT pass not used in -r mode.
+  if (_outputMachOType == MH_OBJECT)
+    return false;
+  // Only some arches use GOT pass.
+  switch (_arch) {
+    case arch_x86_64:
+    case arch_arm64:
+      return true;
+    default:
+      return false;
+  }
+}
+
+bool MachOLinkingContext::needsCompactUnwindPass() const {
+  switch (_outputMachOType) {
+  case MH_EXECUTE:
+  case MH_DYLIB:
+  case MH_BUNDLE:
+    return archHandler().needsCompactUnwind();
+  default:
+    return false;
+  }
+}
+
+bool MachOLinkingContext::needsShimPass() const {
+  // Shim pass only used in final executables.
+  if (_outputMachOType == MH_OBJECT)
+    return false;
+  // Only 32-bit arm arches use Shim pass.
+  switch (_arch) {
+  case arch_armv6:
+  case arch_armv7:
+  case arch_armv7s:
+    return true;
+  default:
+    return false;
+  }
+}
+
+StringRef MachOLinkingContext::binderSymbolName() const {
+  return archHandler().stubInfo().binderSymbolName;
+}
+
+
+
+
+bool MachOLinkingContext::minOS(StringRef mac, StringRef iOS) const {
+  uint32_t parsedVersion;
+  switch (_os) {
+  case OS::macOSX:
+    if (parsePackedVersion(mac, parsedVersion))
+      return false;
+    return _osMinVersion >= parsedVersion;
+  case OS::iOS:
+  case OS::iOS_simulator:
+    if (parsePackedVersion(iOS, parsedVersion))
+      return false;
+    return _osMinVersion >= parsedVersion;
+  case OS::unknown:
+    break;
+  }
+  llvm_unreachable("target not configured for iOS or MacOSX");
+}
+
+bool MachOLinkingContext::addEntryPointLoadCommand() const {
+  if ((_outputMachOType == MH_EXECUTE) && !_outputMachOTypeStatic) {
+    return minOS("10.8", "6.0");
+  }
+  return false;
+}
+
+bool MachOLinkingContext::addUnixThreadLoadCommand() const {
+  switch (_outputMachOType) {
+  case MH_EXECUTE:
+    if (_outputMachOTypeStatic)
+      return true;
+    else
+      return !minOS("10.8", "6.0");
+    break;
+  case MH_DYLINKER:
+  case MH_PRELOAD:
+    return true;
+  default:
+    return false;
+  }
+}
+
+bool MachOLinkingContext::pathExists(StringRef path) const {
+  if (!_testingFileUsage)
+    return llvm::sys::fs::exists(path.str());
+
+  // Otherwise, we're in test mode: only files explicitly provided on the
+  // command-line exist.
+  std::string key = path.str();
+  std::replace(key.begin(), key.end(), '\\', '/');
+  return _existingPaths.find(key) != _existingPaths.end();
+}
+
+bool MachOLinkingContext::fileExists(StringRef path) const {
+  bool found = pathExists(path);
+  // Log search misses.
+  if (!found)
+    addInputFileNotFound(path);
+
+  // When testing, file is never opened, so logging is done here.
+  if (_testingFileUsage && found)
+    addInputFileDependency(path);
+
+  return found;
+}
+
+void MachOLinkingContext::setSysLibRoots(const StringRefVector &paths) {
+  _syslibRoots = paths;
+}
+
+void MachOLinkingContext::addRpath(StringRef rpath) {
+  _rpaths.push_back(rpath);
+}
+
+void MachOLinkingContext::addModifiedSearchDir(StringRef libPath,
+                                               bool isSystemPath) {
+  bool addedModifiedPath = false;
+
+  // -syslibroot only applies to absolute paths.
+  if (libPath.startswith("/")) {
+    for (auto syslibRoot : _syslibRoots) {
+      SmallString<256> path(syslibRoot);
+      llvm::sys::path::append(path, libPath);
+      if (pathExists(path)) {
+        _searchDirs.push_back(path.str().copy(_allocator));
+        addedModifiedPath = true;
+      }
+    }
+  }
+
+  if (addedModifiedPath)
+    return;
+
+  // Finally, if only one -syslibroot is given, system paths which aren't in it
+  // get suppressed.
+  if (_syslibRoots.size() != 1 || !isSystemPath) {
+    if (pathExists(libPath)) {
+      _searchDirs.push_back(libPath);
+    }
+  }
+}
+
+void MachOLinkingContext::addFrameworkSearchDir(StringRef fwPath,
+                                                bool isSystemPath) {
+  bool pathAdded = false;
+
+  // -syslibroot only used with to absolute framework search paths.
+  if (fwPath.startswith("/")) {
+    for (auto syslibRoot : _syslibRoots) {
+      SmallString<256> path(syslibRoot);
+      llvm::sys::path::append(path, fwPath);
+      if (pathExists(path)) {
+        _frameworkDirs.push_back(path.str().copy(_allocator));
+        pathAdded = true;
+      }
+    }
+  }
+  // If fwPath found in any -syslibroot, then done.
+  if (pathAdded)
+    return;
+
+  // If only one -syslibroot, system paths not in that SDK are suppressed.
+  if (isSystemPath && (_syslibRoots.size() == 1))
+    return;
+
+  // Only use raw fwPath if that directory exists.
+  if (pathExists(fwPath))
+    _frameworkDirs.push_back(fwPath);
+}
+
+
+ErrorOr<StringRef>
+MachOLinkingContext::searchDirForLibrary(StringRef path,
+                                         StringRef libName) const {
+  SmallString<256> fullPath;
+  if (libName.endswith(".o")) {
+    // A request ending in .o is special: just search for the file directly.
+    fullPath.assign(path);
+    llvm::sys::path::append(fullPath, libName);
+    if (fileExists(fullPath))
+      return fullPath.str().copy(_allocator);
+    return make_error_code(llvm::errc::no_such_file_or_directory);
+  }
+
+  // Search for dynamic library
+  fullPath.assign(path);
+  llvm::sys::path::append(fullPath, Twine("lib") + libName + ".dylib");
+  if (fileExists(fullPath))
+    return fullPath.str().copy(_allocator);
+
+  // If not, try for a static library
+  fullPath.assign(path);
+  llvm::sys::path::append(fullPath, Twine("lib") + libName + ".a");
+  if (fileExists(fullPath))
+    return fullPath.str().copy(_allocator);
+
+  return make_error_code(llvm::errc::no_such_file_or_directory);
+}
+
+
+
+ErrorOr<StringRef> MachOLinkingContext::searchLibrary(StringRef libName) const {
+  SmallString<256> path;
+  for (StringRef dir : searchDirs()) {
+    ErrorOr<StringRef> ec = searchDirForLibrary(dir, libName);
+    if (ec)
+      return ec;
+  }
+
+  return make_error_code(llvm::errc::no_such_file_or_directory);
+}
+
+
+ErrorOr<StringRef> MachOLinkingContext::findPathForFramework(StringRef fwName) const{
+  SmallString<256> fullPath;
+  for (StringRef dir : frameworkDirs()) {
+    fullPath.assign(dir);
+    llvm::sys::path::append(fullPath, Twine(fwName) + ".framework", fwName);
+    if (fileExists(fullPath))
+      return fullPath.str().copy(_allocator);
+  }
+
+  return make_error_code(llvm::errc::no_such_file_or_directory);
+}
+
+bool MachOLinkingContext::validateImpl(raw_ostream &diagnostics) {
+  // TODO: if -arch not specified, look at arch of first .o file.
+
+  if (_currentVersion && _outputMachOType != MH_DYLIB) {
+    diagnostics << "error: -current_version can only be used with dylibs\n";
+    return false;
+  }
+
+  if (_compatibilityVersion && _outputMachOType != MH_DYLIB) {
+    diagnostics
+        << "error: -compatibility_version can only be used with dylibs\n";
+    return false;
+  }
+
+  if (_deadStrippableDylib && _outputMachOType != MH_DYLIB) {
+    diagnostics
+        << "error: -mark_dead_strippable_dylib can only be used with dylibs.\n";
+    return false;
+  }
+
+  if (!_bundleLoader.empty() && outputMachOType() != MH_BUNDLE) {
+    diagnostics
+        << "error: -bundle_loader can only be used with Mach-O bundles\n";
+    return false;
+  }
+
+  // If -exported_symbols_list used, all exported symbols must be defined.
+  if (_exportMode == ExportMode::whiteList) {
+    for (const auto &symbol : _exportedSymbols)
+      addInitialUndefinedSymbol(symbol.getKey());
+  }
+
+  // If -dead_strip, set up initial live symbols.
+  if (deadStrip()) {
+    // Entry point is live.
+    if (outputTypeHasEntry())
+      addDeadStripRoot(entrySymbolName());
+    // Lazy binding helper is live.
+    if (needsStubsPass())
+      addDeadStripRoot(binderSymbolName());
+    // If using -exported_symbols_list, make all exported symbols live.
+    if (_exportMode == ExportMode::whiteList) {
+      setGlobalsAreDeadStripRoots(false);
+      for (const auto &symbol : _exportedSymbols)
+        addDeadStripRoot(symbol.getKey());
+    }
+  }
+
+  addOutputFileDependency(outputPath());
+
+  return true;
+}
+
+void MachOLinkingContext::addPasses(PassManager &pm) {
+  mach_o::addLayoutPass(pm, *this);
+  if (needsStubsPass())
+    mach_o::addStubsPass(pm, *this);
+  if (needsCompactUnwindPass())
+    mach_o::addCompactUnwindPass(pm, *this);
+  if (needsGOTPass())
+    mach_o::addGOTPass(pm, *this);
+  if (needsShimPass())
+    mach_o::addShimPass(pm, *this); // Shim pass must run after stubs pass.
+}
+
+Writer &MachOLinkingContext::writer() const {
+  if (!_writer)
+    _writer = createWriterMachO(*this);
+  return *_writer;
+}
+
+ErrorOr<std::unique_ptr<MemoryBuffer>>
+MachOLinkingContext::getMemoryBuffer(StringRef path) {
+  addInputFileDependency(path);
+
+  ErrorOr<std::unique_ptr<MemoryBuffer>> mbOrErr =
+    MemoryBuffer::getFileOrSTDIN(path);
+  if (std::error_code ec = mbOrErr.getError())
+    return ec;
+  std::unique_ptr<MemoryBuffer> mb = std::move(mbOrErr.get());
+
+  // If buffer contains a fat file, find required arch in fat buffer
+  // and switch buffer to point to just that required slice.
+  uint32_t offset;
+  uint32_t size;
+  if (sliceFromFatFile(*mb, offset, size))
+    return MemoryBuffer::getFileSlice(path, size, offset);
+  return std::move(mb);
+}
+
+MachODylibFile* MachOLinkingContext::loadIndirectDylib(StringRef path) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> mbOrErr = getMemoryBuffer(path);
+  if (mbOrErr.getError())
+    return nullptr;
+
+  std::vector<std::unique_ptr<File>> files;
+  if (registry().loadFile(std::move(mbOrErr.get()), files))
+    return nullptr;
+  assert(files.size() == 1 && "expected one file in dylib");
+  files[0]->parse();
+  MachODylibFile* result = reinterpret_cast<MachODylibFile*>(files[0].get());
+  // Node object now owned by _indirectDylibs vector.
+  _indirectDylibs.push_back(std::move(files[0]));
+  return result;
+}
+
+
+MachODylibFile* MachOLinkingContext::findIndirectDylib(StringRef path) {
+  // See if already loaded.
+  auto pos = _pathToDylibMap.find(path);
+  if (pos != _pathToDylibMap.end())
+    return pos->second;
+
+  // Search -L paths if of the form "libXXX.dylib"
+  std::pair<StringRef, StringRef> split = path.rsplit('/');
+  StringRef leafName = split.second;
+  if (leafName.startswith("lib") && leafName.endswith(".dylib")) {
+    // FIXME: Need to enhance searchLibrary() to only look for .dylib
+    auto libPath = searchLibrary(leafName);
+    if (!libPath.getError()) {
+      return loadIndirectDylib(libPath.get());
+    }
+  }
+
+  // Try full path with sysroot.
+  for (StringRef sysPath : _syslibRoots) {
+    SmallString<256> fullPath;
+    fullPath.assign(sysPath);
+    llvm::sys::path::append(fullPath, path);
+    if (pathExists(fullPath))
+      return loadIndirectDylib(fullPath);
+  }
+
+  // Try full path.
+  if (pathExists(path)) {
+    return loadIndirectDylib(path);
+  }
+
+  return nullptr;
+}
+
+uint32_t MachOLinkingContext::dylibCurrentVersion(StringRef installName) const {
+  auto pos = _pathToDylibMap.find(installName);
+  if (pos != _pathToDylibMap.end())
+    return pos->second->currentVersion();
+  else
+    return 0x1000; // 1.0
+}
+
+uint32_t MachOLinkingContext::dylibCompatVersion(StringRef installName) const {
+  auto pos = _pathToDylibMap.find(installName);
+  if (pos != _pathToDylibMap.end())
+    return pos->second->compatVersion();
+  else
+    return 0x1000; // 1.0
+}
+
+bool MachOLinkingContext::createImplicitFiles(
+                            std::vector<std::unique_ptr<File> > &result) {
+  // Add indirect dylibs by asking each linked dylib to add its indirects.
+  // Iterate until no more dylibs get loaded.
+  size_t dylibCount = 0;
+  while (dylibCount != _allDylibs.size()) {
+    dylibCount = _allDylibs.size();
+    for (MachODylibFile *dylib : _allDylibs) {
+      dylib->loadReExportedDylibs([this] (StringRef path) -> MachODylibFile* {
+                                  return findIndirectDylib(path); });
+    }
+  }
+
+  // Let writer add output type specific extras.
+  return writer().createImplicitFiles(result);
+}
+
+
+void MachOLinkingContext::registerDylib(MachODylibFile *dylib,
+                                        bool upward) const {
+  _allDylibs.insert(dylib);
+  _pathToDylibMap[dylib->installName()] = dylib;
+  // If path is different than install name, register path too.
+  if (!dylib->path().equals(dylib->installName()))
+    _pathToDylibMap[dylib->path()] = dylib;
+  if (upward)
+    _upwardDylibs.insert(dylib);
+}
+
+
+bool MachOLinkingContext::isUpwardDylib(StringRef installName) const {
+  for (MachODylibFile *dylib : _upwardDylibs) {
+    if (dylib->installName().equals(installName))
+      return true;
+  }
+  return false;
+}
+
+ArchHandler &MachOLinkingContext::archHandler() const {
+  if (!_archHandler)
+    _archHandler = ArchHandler::create(_arch);
+  return *_archHandler;
+}
+
+
+void MachOLinkingContext::addSectionAlignment(StringRef seg, StringRef sect,
+                                                               uint8_t align2) {
+  SectionAlign entry;
+  entry.segmentName = seg;
+  entry.sectionName = sect;
+  entry.align2 = align2;
+  _sectAligns.push_back(entry);
+}
+
+bool MachOLinkingContext::sectionAligned(StringRef seg, StringRef sect,
+                                                        uint8_t &align2) const {
+  for (const SectionAlign &entry : _sectAligns) {
+    if (seg.equals(entry.segmentName) && sect.equals(entry.sectionName)) {
+      align2 = entry.align2;
+      return true;
+    }
+  }
+  return false;
+}
+
+
+void MachOLinkingContext::addExportSymbol(StringRef sym) {
+  // Support old crufty export lists with bogus entries.
+  if (sym.endswith(".eh") || sym.startswith(".objc_category_name_")) {
+    llvm::errs() << "warning: ignoring " << sym << " in export list\n";
+    return;
+  }
+  // Only i386 MacOSX uses old ABI, so don't change those.
+  if ((_os != OS::macOSX) || (_arch != arch_x86)) {
+    // ObjC has two differnent ABIs.  Be nice and allow one export list work for
+    // both ABIs by renaming symbols.
+    if (sym.startswith(".objc_class_name_")) {
+      std::string abi2className("_OBJC_CLASS_$_");
+      abi2className += sym.substr(17);
+      _exportedSymbols.insert(copy(abi2className));
+      std::string abi2metaclassName("_OBJC_METACLASS_$_");
+      abi2metaclassName += sym.substr(17);
+      _exportedSymbols.insert(copy(abi2metaclassName));
+      return;
+    }
+  }
+
+  // FIXME: Support wildcards.
+  _exportedSymbols.insert(sym);
+}
+
+bool MachOLinkingContext::exportSymbolNamed(StringRef sym) const {
+  switch (_exportMode) {
+  case ExportMode::globals:
+    llvm_unreachable("exportSymbolNamed() should not be called in this mode");
+    break;
+  case ExportMode::whiteList:
+    return _exportedSymbols.count(sym);
+  case ExportMode::blackList:
+    return !_exportedSymbols.count(sym);
+  }
+  llvm_unreachable("_exportMode unknown enum value");
+}
+
+std::string MachOLinkingContext::demangle(StringRef symbolName) const {
+  // Only try to demangle symbols if -demangle on command line
+  if (!demangleSymbols())
+    return symbolName;
+
+  // Only try to demangle symbols that look like C++ symbols
+  if (!symbolName.startswith("__Z"))
+    return symbolName;
+
+#if defined(HAVE_CXXABI_H)
+  SmallString<256> symBuff;
+  StringRef nullTermSym = Twine(symbolName).toNullTerminatedStringRef(symBuff);
+  // Mach-O has extra leading underscore that needs to be removed.
+  const char *cstr = nullTermSym.data() + 1;
+  int status;
+  char *demangled = abi::__cxa_demangle(cstr, nullptr, nullptr, &status);
+  if (demangled != NULL) {
+    std::string result(demangled);
+    // __cxa_demangle() always uses a malloc'ed buffer to return the result.
+    free(demangled);
+    return result;
+  }
+#endif
+
+  return symbolName;
+}
+
+std::error_code MachOLinkingContext::createDependencyFile(StringRef path) {
+  std::error_code ec;
+  _dependencyInfo = std::unique_ptr<llvm::raw_fd_ostream>(new
+                         llvm::raw_fd_ostream(path, ec, llvm::sys::fs::F_None));
+  if (ec) {
+    _dependencyInfo.reset();
+    return ec;
+  }
+
+  char linkerVersionOpcode = 0x00;
+  *_dependencyInfo << linkerVersionOpcode;
+  *_dependencyInfo << "lld";     // FIXME
+  *_dependencyInfo << '\0';
+
+  return std::error_code();
+}
+
+void MachOLinkingContext::addInputFileDependency(StringRef path) const {
+  if (!_dependencyInfo)
+    return;
+
+  char inputFileOpcode = 0x10;
+  *_dependencyInfo << inputFileOpcode;
+  *_dependencyInfo << path;
+  *_dependencyInfo << '\0';
+}
+
+void MachOLinkingContext::addInputFileNotFound(StringRef path) const {
+  if (!_dependencyInfo)
+    return;
+
+  char inputFileOpcode = 0x11;
+  *_dependencyInfo << inputFileOpcode;
+  *_dependencyInfo << path;
+  *_dependencyInfo << '\0';
+}
+
+void MachOLinkingContext::addOutputFileDependency(StringRef path) const {
+  if (!_dependencyInfo)
+    return;
+
+  char outputFileOpcode = 0x40;
+  *_dependencyInfo << outputFileOpcode;
+  *_dependencyInfo << path;
+  *_dependencyInfo << '\0';
+}
+
+void MachOLinkingContext::appendOrderedSymbol(StringRef symbol,
+                                              StringRef filename) {
+  // To support sorting static functions which may have the same name in
+  // multiple .o files, _orderFiles maps the symbol name to a vector
+  // of OrderFileNode each of which can specify a file prefix.
+  OrderFileNode info;
+  if (!filename.empty())
+    info.fileFilter = copy(filename);
+  info.order = _orderFileEntries++;
+  _orderFiles[symbol].push_back(info);
+}
+
+bool
+MachOLinkingContext::findOrderOrdinal(const std::vector<OrderFileNode> &nodes,
+                                      const DefinedAtom *atom,
+                                      unsigned &ordinal) {
+  const File *objFile = &atom->file();
+  assert(objFile);
+  StringRef objName = objFile->path();
+  std::pair<StringRef, StringRef> dirAndLeaf = objName.rsplit('/');
+  if (!dirAndLeaf.second.empty())
+    objName = dirAndLeaf.second;
+  for (const OrderFileNode &info : nodes) {
+    if (info.fileFilter.empty()) {
+      // Have unprefixed symbol name in order file that matches this atom.
+      ordinal = info.order;
+      return true;
+    }
+    if (info.fileFilter.equals(objName)) {
+      // Have prefixed symbol name in order file that matches atom's path.
+      ordinal = info.order;
+      return true;
+    }
+  }
+  return false;
+}
+
+bool MachOLinkingContext::customAtomOrderer(const DefinedAtom *left,
+                                            const DefinedAtom *right,
+                                            bool &leftBeforeRight) const {
+  // No custom sorting if no order file entries.
+  if (!_orderFileEntries)
+    return false;
+
+  // Order files can only order named atoms.
+  StringRef leftName = left->name();
+  StringRef rightName = right->name();
+  if (leftName.empty() || rightName.empty())
+    return false;
+
+  // If neither is in order file list, no custom sorter.
+  auto leftPos = _orderFiles.find(leftName);
+  auto rightPos = _orderFiles.find(rightName);
+  bool leftIsOrdered = (leftPos != _orderFiles.end());
+  bool rightIsOrdered = (rightPos != _orderFiles.end());
+  if (!leftIsOrdered && !rightIsOrdered)
+    return false;
+
+  // There could be multiple symbols with same name but different file prefixes.
+  unsigned leftOrder;
+  unsigned rightOrder;
+  bool foundLeft =
+      leftIsOrdered && findOrderOrdinal(leftPos->getValue(), left, leftOrder);
+  bool foundRight = rightIsOrdered &&
+                    findOrderOrdinal(rightPos->getValue(), right, rightOrder);
+  if (!foundLeft && !foundRight)
+    return false;
+
+  // If only one is in order file list, ordered one goes first.
+  if (foundLeft != foundRight)
+    leftBeforeRight = foundLeft;
+  else
+    leftBeforeRight = (leftOrder < rightOrder);
+
+  return true;
+}
+
+static bool isLibrary(const std::unique_ptr<Node> &elem) {
+  if (FileNode *node = dyn_cast<FileNode>(const_cast<Node *>(elem.get()))) {
+    File *file = node->getFile();
+    return isa<SharedLibraryFile>(file) || isa<ArchiveLibraryFile>(file);
+  }
+  return false;
+}
+
+// The darwin linker processes input files in two phases.  The first phase
+// links in all object (.o) files in command line order. The second phase
+// links in libraries in command line order.
+// In this function we reorder the input files so that all the object files
+// comes before any library file. We also make a group for the library files
+// so that the Resolver will reiterate over the libraries as long as we find
+// new undefines from libraries.
+void MachOLinkingContext::finalizeInputFiles() {
+  std::vector<std::unique_ptr<Node>> &elements = getNodes();
+  std::stable_sort(elements.begin(), elements.end(),
+                   [](const std::unique_ptr<Node> &a,
+                      const std::unique_ptr<Node> &b) {
+                     return !isLibrary(a) && isLibrary(b);
+                   });
+  size_t numLibs = std::count_if(elements.begin(), elements.end(), isLibrary);
+  elements.push_back(llvm::make_unique<GroupEnd>(numLibs));
+}
+
+} // end namespace lld