TheRock/compiler/amd-llvm/clang/tools/clang-linker-wrapper/ClangLinkerWrapper.cpp

//===-- clang-linker-wrapper/ClangLinkerWrapper.cpp -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This tool works as a wrapper over a linking job. This tool is used to create
// linked device images for offloading. It scans the linker's input for embedded
// device offloading data stored in sections `.llvm.offloading` and extracts it
// as a temporary file. The extracted device files will then be passed to a
// device linking job to create a final device image.
//
//===----------------------------------------------------------------------===//

#include "clang/Basic/TargetID.h"
#include "clang/Basic/Version.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/BinaryFormat/Magic.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/Frontend/Offloading/OffloadWrapper.h"
#include "llvm/Frontend/Offloading/Utility.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/Module.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/LTO/LTO.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Object/Binary.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Object/OffloadBinary.h"
#include "llvm/Option/ArgList.h"
#include "llvm/Option/OptTable.h"
#include "llvm/Option/Option.h"
#include "llvm/Plugins/PassPlugin.h"
#include "llvm/Remarks/HotnessThresholdParser.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Parallel.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/Support/WithColor.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/TargetParser/Host.h"
#include <optional>

using namespace llvm;
using namespace llvm::opt;
using namespace llvm::object;

// Various tools (e.g., llc and opt) duplicate this series of declarations for
// options related to passes and remarks.

static cl::opt<bool> RemarksWithHotness(
    "pass-remarks-with-hotness",
    cl::desc("With PGO, include profile count in optimization remarks"),
    cl::Hidden);

static cl::opt<std::optional<uint64_t>, false, remarks::HotnessThresholdParser>
    RemarksHotnessThreshold(
        "pass-remarks-hotness-threshold",
        cl::desc("Minimum profile count required for "
                 "an optimization remark to be output. "
                 "Use 'auto' to apply the threshold from profile summary."),
        cl::value_desc("N or 'auto'"), cl::init(0), cl::Hidden);

static cl::opt<std::string>
    RemarksFilename("pass-remarks-output",
                    cl::desc("Output filename for pass remarks"),
                    cl::value_desc("filename"));

static cl::opt<std::string>
    RemarksPasses("pass-remarks-filter",
                  cl::desc("Only record optimization remarks from passes whose "
                           "names match the given regular expression"),
                  cl::value_desc("regex"));

static cl::opt<std::string> RemarksFormat(
    "pass-remarks-format",
    cl::desc("The format used for serializing remarks (default: YAML)"),
    cl::value_desc("format"), cl::init("yaml"));

static cl::list<std::string>
    PassPlugins("load-pass-plugin",
                cl::desc("Load passes from plugin library"));

static cl::opt<std::string> PassPipeline(
    "passes",
    cl::desc(
        "A textual description of the pass pipeline. To have analysis passes "
        "available before a certain pass, add 'require<foo-analysis>'. "
        "'-passes' overrides the pass pipeline (but not all effects) from "
        "specifying '--opt-level=O?' (O2 is the default) to "
        "clang-linker-wrapper.  Be sure to include the corresponding "
        "'default<O?>' in '-passes'."));
static cl::alias PassPipeline2("p", cl::aliasopt(PassPipeline),
                               cl::desc("Alias for -passes"));

/// Path of the current binary.
static const char *LinkerExecutable;

/// Save intermediary results.
static bool SaveTemps = false;

/// Print arguments without executing.
static bool DryRun = false;

/// Print verbose output.
static bool Verbose = false;

/// Filename of the executable being created.
static StringRef ExecutableName;

/// Binary path for the CUDA installation.
static std::string CudaBinaryPath;

/// Mutex lock to protect writes to shared TempFiles in parallel.
static std::mutex TempFilesMutex;

/// Temporary files created by the linker wrapper.
static std::list<SmallString<128>> TempFiles;

/// Codegen flags for LTO backend.
static codegen::RegisterCodeGenFlags CodeGenFlags;

/// Whether or not to look through symlinks when resolving binaries.
static bool CanonicalPrefixes = true;

using OffloadingImage = OffloadBinary::OffloadingImage;

namespace llvm {
// Provide DenseMapInfo so that OffloadKind can be used in a DenseMap.
template <> struct DenseMapInfo<OffloadKind> {
  static inline OffloadKind getEmptyKey() { return OFK_LAST; }
  static unsigned getHashValue(const OffloadKind &Val) { return Val; }

  static bool isEqual(const OffloadKind &LHS, const OffloadKind &RHS) {
    return LHS == RHS;
  }
};
} // namespace llvm

namespace {
using std::error_code;

/// Must not overlap with llvm::opt::DriverFlag.
enum WrapperFlags {
  WrapperOnlyOption = (1 << 4), // Options only used by the linker wrapper.
  DeviceOnlyOption = (1 << 5),  // Options only used for device linking.
};

enum ID {
  OPT_INVALID = 0, // This is not an option ID.
#define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
#include "LinkerWrapperOpts.inc"
  LastOption
#undef OPTION
};

#define OPTTABLE_STR_TABLE_CODE
#include "LinkerWrapperOpts.inc"
#undef OPTTABLE_STR_TABLE_CODE

#define OPTTABLE_PREFIXES_TABLE_CODE
#include "LinkerWrapperOpts.inc"
#undef OPTTABLE_PREFIXES_TABLE_CODE

static constexpr OptTable::Info InfoTable[] = {
#define OPTION(...) LLVM_CONSTRUCT_OPT_INFO(__VA_ARGS__),
#include "LinkerWrapperOpts.inc"
#undef OPTION
};

class WrapperOptTable : public opt::GenericOptTable {
public:
  WrapperOptTable()
      : opt::GenericOptTable(OptionStrTable, OptionPrefixesTable, InfoTable) {}
};

const OptTable &getOptTable() {
  static const WrapperOptTable Table;
  return Table;
}

void printCommands(ArrayRef<StringRef> CmdArgs) {
  if (CmdArgs.empty())
    return;

  llvm::errs() << " \"" << CmdArgs.front() << "\" ";
  for (auto IC = std::next(CmdArgs.begin()), IE = CmdArgs.end(); IC != IE; ++IC)
    llvm::errs() << *IC << (std::next(IC) != IE ? " " : "\n");
}

[[noreturn]] void reportError(Error E) {
  outs().flush();
  logAllUnhandledErrors(std::move(E),
                        WithColor::error(errs(), LinkerExecutable));
  exit(EXIT_FAILURE);
}

std::string getExecutableDir(const char *Name) {
  if (!CanonicalPrefixes)
    return sys::path::parent_path(LinkerExecutable).str();
  void *Ptr = reinterpret_cast<void *>(&getExecutableDir);
  return sys::path::parent_path(sys::fs::getMainExecutable(Name, Ptr)).str();
}

/// Get a temporary filename suitable for output.
Expected<StringRef> createOutputFile(const Twine &Prefix, StringRef Extension) {
  std::scoped_lock<decltype(TempFilesMutex)> Lock(TempFilesMutex);
  SmallString<128> OutputFile;
  std::string PrefixStr = clang::sanitizeTargetIDInFileName(Prefix.str());

  if (SaveTemps) {
    (PrefixStr + "." + Extension).toNullTerminatedStringRef(OutputFile);
  } else {
    if (std::error_code EC = sys::fs::createTemporaryFile(
            sys::path::filename(PrefixStr), Extension, OutputFile))
      return createFileError(OutputFile, EC);
  }

  TempFiles.emplace_back(std::move(OutputFile));
  return TempFiles.back();
}

/// Execute the command \p ExecutablePath with the arguments \p Args.
Error executeCommands(StringRef ExecutablePath, ArrayRef<StringRef> Args) {
  if (Verbose || DryRun)
    printCommands(Args);

  if (DryRun)
    return Error::success();

  // If the command line fits within system limits, execute directly.
  if (sys::commandLineFitsWithinSystemLimits(ExecutablePath, Args)) {
    if (sys::ExecuteAndWait(ExecutablePath, Args))
      return createStringError(
          "'%s' failed", sys::path::filename(ExecutablePath).str().c_str());
    return Error::success();
  }

  // Write the arguments to a response file and pass that instead.
  auto TempFileOrErr = createOutputFile("response", "rsp");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();

  SmallString<256> Contents;
  raw_svector_ostream OS(Contents);
  for (StringRef Arg : llvm::drop_begin(Args)) {
    sys::printArg(OS, Arg, /*Quote=*/true);
    OS << " ";
  }

  if (std::error_code EC = sys::writeFileWithEncoding(*TempFileOrErr, Contents))
    return createStringError("failed to write response file: %s",
                             EC.message().c_str());

  std::string ResponseFile = ("@" + *TempFileOrErr).str();
  SmallVector<StringRef, 2> NewArgs = {Args.front(), ResponseFile};
  if (sys::ExecuteAndWait(ExecutablePath, NewArgs))
    return createStringError("'%s' failed",
                             sys::path::filename(ExecutablePath).str().c_str());
  return Error::success();
}

Expected<std::string> findProgram(StringRef Name, ArrayRef<StringRef> Paths) {

  ErrorOr<std::string> Path = sys::findProgramByName(Name, Paths);
  if (!Path)
    Path = sys::findProgramByName(Name);
  if (!Path && DryRun)
    return Name.str();
  if (!Path)
    return createStringError(Path.getError(),
                             "Unable to find '" + Name + "' in path");
  return *Path;
}

bool linkerSupportsLTO(const ArgList &Args) {
  llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
  return Triple.isNVPTX() || Triple.isAMDGPU() ||
         (!Triple.isGPU() &&
          Args.getLastArgValue(OPT_linker_path_EQ).ends_with("lld"));
}

/// Returns the hashed value for a constant string.
std::string getHash(StringRef Str) {
  llvm::MD5 Hasher;
  llvm::MD5::MD5Result Hash;
  Hasher.update(Str);
  Hasher.final(Hash);
  return llvm::utohexstr(Hash.low(), /*LowerCase=*/true);
}

/// Renames offloading entry sections in a relocatable link so they do not
/// conflict with a later link job.
Error relocateOffloadSection(const ArgList &Args, StringRef Output) {
  llvm::Triple Triple(
      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));
  if (Triple.isOSWindows())
    return createStringError(
        "Relocatable linking is not supported on COFF targets");

  Expected<std::string> ObjcopyPath =
      findProgram("llvm-objcopy", {getExecutableDir("llvm-objcopy")});
  if (!ObjcopyPath)
    return ObjcopyPath.takeError();

  // Use the linker output file to get a unique hash. This creates a unique
  // identifier to rename the sections to that is deterministic to the contents.
  auto BufferOrErr = DryRun ? MemoryBuffer::getMemBuffer("")
                            : MemoryBuffer::getFileOrSTDIN(Output);
  if (!BufferOrErr)
    return createStringError("Failed to open %s", Output.str().c_str());
  std::string Suffix = "_" + getHash((*BufferOrErr)->getBuffer());

  SmallVector<StringRef> ObjcopyArgs = {
      *ObjcopyPath,
      Output,
  };

  // Remove the old .llvm.offloading section to prevent further linking.
  ObjcopyArgs.emplace_back("--remove-section");
  ObjcopyArgs.emplace_back(".llvm.offloading");
  StringRef Prefix = "llvm";
  auto Section = (Prefix + "_offload_entries").str();
  // Rename the offloading entries to make them private to this link unit.
  ObjcopyArgs.emplace_back("--rename-section");
  ObjcopyArgs.emplace_back(
      Args.MakeArgString(Section + "=" + Section + Suffix));

  // Rename the __start_ / __stop_ symbols appropriately to iterate over the
  // newly renamed section containing the offloading entries.
  ObjcopyArgs.emplace_back("--redefine-sym");
  ObjcopyArgs.emplace_back(Args.MakeArgString("__start_" + Section + "=" +
                                              "__start_" + Section + Suffix));
  ObjcopyArgs.emplace_back("--redefine-sym");
  ObjcopyArgs.emplace_back(Args.MakeArgString("__stop_" + Section + "=" +
                                              "__stop_" + Section + Suffix));

  if (Error Err = executeCommands(*ObjcopyPath, ObjcopyArgs))
    return Err;

  return Error::success();
}

/// Runs the wrapped linker job with the newly created input.
Error runLinker(ArrayRef<StringRef> Files, const ArgList &Args) {
  llvm::TimeTraceScope TimeScope("Execute host linker");

  // Render the linker arguments and add the newly created image. We add it
  // after the output file to ensure it is linked with the correct libraries.
  StringRef LinkerPath = Args.getLastArgValue(OPT_linker_path_EQ);
  if (LinkerPath.empty())
    return createStringError("linker path missing, must pass 'linker-path'");
  ArgStringList NewLinkerArgs;
  for (const opt::Arg *Arg : Args) {
    // Do not forward arguments only intended for the linker wrapper.
    if (Arg->getOption().hasFlag(WrapperOnlyOption))
      continue;

    Arg->render(Args, NewLinkerArgs);
    if (Arg->getOption().matches(OPT_o) || Arg->getOption().matches(OPT_out))
      llvm::transform(Files, std::back_inserter(NewLinkerArgs),
                      [&](StringRef A) { return Args.MakeArgString(A); });
  }

  SmallVector<StringRef> LinkerArgs({LinkerPath});
  for (StringRef Arg : NewLinkerArgs)
    LinkerArgs.push_back(Arg);
  if (Error Err = executeCommands(LinkerPath, LinkerArgs))
    return Err;

  if (Args.hasArg(OPT_relocatable))
    return relocateOffloadSection(Args, ExecutableName);

  return Error::success();
}

void printVersion(raw_ostream &OS) {
  OS << clang::getClangToolFullVersion("clang-linker-wrapper") << '\n';
}

namespace nvptx {
Expected<StringRef>
fatbinary(ArrayRef<std::pair<StringRef, StringRef>> InputFiles,
          const ArgList &Args) {
  llvm::TimeTraceScope TimeScope("NVPTX fatbinary");
  // NVPTX uses the fatbinary program to bundle the linked images.
  Expected<std::string> FatBinaryPath =
      findProgram("fatbinary", {CudaBinaryPath + "/bin"});
  if (!FatBinaryPath)
    return FatBinaryPath.takeError();

  llvm::Triple Triple(
      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));

  // Create a new file to write the linked device image to.
  auto TempFileOrErr = createOutputFile(ExecutableName, "fatbin");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();

  SmallVector<StringRef, 16> CmdArgs;
  CmdArgs.push_back(*FatBinaryPath);
  CmdArgs.push_back(Triple.isArch64Bit() ? "-64" : "-32");
  CmdArgs.push_back("--create");
  CmdArgs.push_back(*TempFileOrErr);
  for (const auto &[File, Arch] : InputFiles)
    CmdArgs.push_back(Args.MakeArgString(
        "--image3=kind=elf,sm=" + Arch.drop_front(3) + ",file=" + File));

  if (Error Err = executeCommands(*FatBinaryPath, CmdArgs))
    return std::move(Err);

  return *TempFileOrErr;
}
} // namespace nvptx

namespace amdgcn {

// Constructs a triple string for clang offload bundler.
// NOTE: copied from HIPUtility.cpp.
static std::string normalizeForBundler(const llvm::Triple &T,
                                       bool HasTargetID) {
  return HasTargetID ? (T.getArchName() + "-" + T.getVendorName() + "-" +
                        T.getOSName() + "-" + T.getEnvironmentName())
                           .str()
                     : T.normalize(llvm::Triple::CanonicalForm::FOUR_IDENT);
}

Expected<StringRef>
fatbinary(ArrayRef<std::tuple<StringRef, StringRef, StringRef>> InputFiles,
          const ArgList &Args) {
  llvm::TimeTraceScope TimeScope("AMDGPU Fatbinary");

  // AMDGPU uses the clang-offload-bundler to bundle the linked images.
  Expected<std::string> OffloadBundlerPath = findProgram(
      "clang-offload-bundler", {getExecutableDir("clang-offload-bundler")});
  if (!OffloadBundlerPath)
    return OffloadBundlerPath.takeError();

  // Create a new file to write the linked device image to.
  auto TempFileOrErr = createOutputFile(ExecutableName, "hipfb");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();

  BumpPtrAllocator Alloc;
  StringSaver Saver(Alloc);

  SmallVector<StringRef, 16> CmdArgs;
  CmdArgs.push_back(*OffloadBundlerPath);
  CmdArgs.push_back("-type=o");
  CmdArgs.push_back("-bundle-align=4096");

  if (Args.hasArg(OPT_compress))
    CmdArgs.push_back("-compress");
  if (auto *Arg = Args.getLastArg(OPT_compression_level_eq))
    CmdArgs.push_back(
        Args.MakeArgString(Twine("-compression-level=") + Arg->getValue()));

  llvm::Triple HostTriple(
      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));
  SmallVector<StringRef> Targets = {
      Saver.save("-targets=host-" + HostTriple.normalize())};
  for (const auto &[File, TripleRef, Arch] : InputFiles) {
    std::string NormalizedTriple =
        normalizeForBundler(Triple(TripleRef), !Arch.empty());
    Targets.push_back(Saver.save("hip-" + NormalizedTriple + "-" + Arch));
  }
  CmdArgs.push_back(Saver.save(llvm::join(Targets, ",")));

#ifdef _WIN32
  CmdArgs.push_back("-input=NUL");
#else
  CmdArgs.push_back("-input=/dev/null");
#endif
  for (const auto &[File, Triple, Arch] : InputFiles)
    CmdArgs.push_back(Saver.save("-input=" + File));

  CmdArgs.push_back(Saver.save("-output=" + *TempFileOrErr));

  if (Error Err = executeCommands(*OffloadBundlerPath, CmdArgs))
    return std::move(Err);

  return *TempFileOrErr;
}
} // namespace amdgcn

namespace generic {
Expected<StringRef> clang(ArrayRef<StringRef> InputFiles, const ArgList &Args,
                          uint16_t ActiveOffloadKindMask) {
  llvm::TimeTraceScope TimeScope("Clang");
  // Use `clang` to invoke the appropriate device tools.
  Expected<std::string> ClangPath =
      findProgram("clang", {getExecutableDir("clang")});
  if (!ClangPath)
    return ClangPath.takeError();

  const llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
  StringRef Arch = Args.getLastArgValue(OPT_arch_EQ);
  // Create a new file to write the linked device image to. Assume that the
  // input filename already has the device and architecture.
  std::string OutputFileBase =
      "." + Triple.getArchName().str() + "." + Arch.str();
  auto TempFileOrErr = createOutputFile(ExecutableName + OutputFileBase, "img");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();

  SmallVector<StringRef, 16> CmdArgs{
      *ClangPath,
      "--no-default-config",
      "-o",
      *TempFileOrErr,
      // Without -dumpdir, Clang will place auxiliary output files in the
      // temporary directory of TempFileOrErr, where they will not easily be
      // found by the user and might eventually be automatically removed.  Tell
      // Clang to instead place them alongside the final executable.
      "-dumpdir",
      Args.MakeArgString(ExecutableName + OutputFileBase + ".img."),
      Args.MakeArgString("--target=" + Triple.getTriple()),
  };

  if (!Arch.empty())
    Triple.isAMDGPU() ? CmdArgs.push_back(Args.MakeArgString("-mcpu=" + Arch))
                      : CmdArgs.push_back(Args.MakeArgString("-march=" + Arch));

  // AMDGPU defaults to the LTO pipeline. Non-RDC HIP uses the conventional
  // non-LTO pipeline so device codegen still runs here, in parallel, instead
  // of being deferred to the LTO link.
  // FIXME: This is a stop-gap for non-RDC. Longer term, RDC and non-RDC should
  // share a unified interface so runtime libraries can be provided to non-RDC
  // compilations without relying on -mlink-builtin-bitcode.
  bool NonLTOAMDGPU = Triple.isAMDGPU() && Args.hasArg(OPT_no_lto);
  if (Triple.isAMDGPU() && !NonLTOAMDGPU)
    CmdArgs.push_back("-flto");

  // Forward all of the `--offload-opt` and `-mllvm` options to the device.
  for (auto &Arg : Args.filtered(OPT_offload_opt_eq_minus, OPT_mllvm))
    CmdArgs.append(
        {"-Xlinker",
         Args.MakeArgString("--plugin-opt=" + StringRef(Arg->getValue()))});

  if (!Triple.isNVPTX() && !Triple.isSPIRV())
    CmdArgs.push_back("-Wl,--no-undefined");

  // The device inputs are bitcode stored in files with an object extension.
  // Force the IR input language so Clang runs the compile and backend phases
  // instead of treating them as linker inputs, which would defer codegen to
  // the LTO link and defeat the non-LTO pipeline.
  if (NonLTOAMDGPU)
    CmdArgs.append({"-x", "ir"});
  for (StringRef InputFile : InputFiles)
    CmdArgs.push_back(InputFile);

  // If this is CPU offloading we copy the input libraries.
  if (!Triple.isGPU()) {
    CmdArgs.push_back("-Wl,-Bsymbolic");
    CmdArgs.push_back("-shared");
    ArgStringList LinkerArgs;
    for (const opt::Arg *Arg :
         Args.filtered(OPT_INPUT, OPT_library, OPT_library_path, OPT_rpath,
                       OPT_whole_archive, OPT_no_whole_archive)) {
      // Sometimes needed libraries are passed by name, such as when using
      // sanitizers. We need to check the file magic for any libraries.
      if (Arg->getOption().matches(OPT_INPUT)) {
        if (!sys::fs::exists(Arg->getValue()) ||
            sys::fs::is_directory(Arg->getValue()))
          continue;

        file_magic Magic;
        if (auto EC = identify_magic(Arg->getValue(), Magic))
          return createStringError("Failed to open %s", Arg->getValue());
        if (Magic != file_magic::archive &&
            Magic != file_magic::elf_shared_object)
          continue;
      }
      if (Arg->getOption().matches(OPT_whole_archive))
        LinkerArgs.push_back(Args.MakeArgString("-Wl,--whole-archive"));
      else if (Arg->getOption().matches(OPT_no_whole_archive))
        LinkerArgs.push_back(Args.MakeArgString("-Wl,--no-whole-archive"));
      else
        Arg->render(Args, LinkerArgs);
    }
    llvm::append_range(CmdArgs, LinkerArgs);
  }

  // Pass on -mllvm options to the linker invocation.
  for (const opt::Arg *Arg : Args.filtered(OPT_mllvm))
    CmdArgs.append({"-Xlinker", Args.MakeArgString(
                                    "-mllvm=" + StringRef(Arg->getValue()))});

  if (SaveTemps && linkerSupportsLTO(Args))
    CmdArgs.push_back("-Wl,--save-temps");

  if (Args.hasArg(OPT_embed_bitcode))
    CmdArgs.push_back("-Wl,--lto-emit-llvm");

  // For linking device code with the SYCL offload kind, special handling is
  // required. Passing --sycl-link to clang results in a call to
  // clang-sycl-linker. Additional linker flags required by clang-sycl-linker
  // will be communicated via the -Xlinker option.
  if (ActiveOffloadKindMask & OFK_SYCL) {
    CmdArgs.push_back("--sycl-link");
    CmdArgs.append(
        {"-Xlinker", Args.MakeArgString("-triple=" + Triple.getTriple())});
    CmdArgs.append({"-Xlinker", Args.MakeArgString("-arch=" + Arch)});
  }

  for (StringRef Arg : Args.getAllArgValues(OPT_linker_arg_EQ))
    CmdArgs.append({"-Xlinker", Args.MakeArgString(Arg)});
  for (StringRef Arg : Args.getAllArgValues(OPT_compiler_arg_EQ))
    CmdArgs.push_back(Args.MakeArgString(Arg));

  if (Error Err = executeCommands(*ClangPath, CmdArgs))
    return std::move(Err);

  return *TempFileOrErr;
}
} // namespace generic

Expected<StringRef> linkDevice(ArrayRef<StringRef> InputFiles,
                               const ArgList &Args,
                               uint16_t ActiveOffloadKindMask) {
  const llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
  switch (Triple.getArch()) {
  case Triple::nvptx:
  case Triple::nvptx64:
  case Triple::amdgcn:
  case Triple::x86:
  case Triple::x86_64:
  case Triple::aarch64:
  case Triple::aarch64_be:
  case Triple::ppc64:
  case Triple::ppc64le:
  case Triple::spirv64:
  case Triple::systemz:
  case Triple::loongarch64:
    return generic::clang(InputFiles, Args, ActiveOffloadKindMask);
  default:
    return createStringError(Triple.getArchName() +
                             " linking is not supported");
  }
}

Error containerizeRawImage(std::unique_ptr<MemoryBuffer> &Img, OffloadKind Kind,
                           const ArgList &Args) {
  llvm::Triple Triple(Args.getLastArgValue(OPT_triple_EQ));
  if (Kind == OFK_OpenMP && Triple.isSPIRV() &&
      Triple.getVendor() == llvm::Triple::Intel)
    return offloading::intel::containerizeOpenMPSPIRVImage(Img, Triple);
  return Error::success();
}

Expected<StringRef> writeOffloadFile(const OffloadFile &File) {
  const OffloadBinary &Binary = *File.getBinary();

  StringRef Prefix =
      sys::path::stem(Binary.getMemoryBufferRef().getBufferIdentifier());
  SmallString<128> Filename;
  (Prefix + "-" + Binary.getTriple() + "-" + Binary.getArch())
      .toVector(Filename);
  auto TempFileOrErr = createOutputFile(Filename, "o");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();

  Expected<std::unique_ptr<FileOutputBuffer>> OutputOrErr =
      FileOutputBuffer::create(*TempFileOrErr, Binary.getImage().size());
  if (!OutputOrErr)
    return OutputOrErr.takeError();
  std::unique_ptr<FileOutputBuffer> Output = std::move(*OutputOrErr);
  llvm::copy(Binary.getImage(), Output->getBufferStart());
  if (Error E = Output->commit())
    return std::move(E);

  return *TempFileOrErr;
}

// Compile the module to an object file using the appropriate target machine for
// the host triple.
Expected<StringRef> compileModule(Module &M, OffloadKind Kind) {
  llvm::TimeTraceScope TimeScope("Compile module");
  std::string Msg;
  const Target *T = TargetRegistry::lookupTarget(M.getTargetTriple(), Msg);
  if (!T)
    return createStringError(Msg);

  auto Options =
      codegen::InitTargetOptionsFromCodeGenFlags(M.getTargetTriple());
  StringRef CPU = "";
  StringRef Features = "";
  std::unique_ptr<TargetMachine> TM(
      T->createTargetMachine(M.getTargetTriple(), CPU, Features, Options,
                             Reloc::PIC_, M.getCodeModel()));

  if (M.getDataLayout().isDefault())
    M.setDataLayout(TM->createDataLayout());

  int FD = -1;
  auto TempFileOrErr = createOutputFile(
      ExecutableName + "." + getOffloadKindName(Kind) + ".image.wrapper", "o");
  if (!TempFileOrErr)
    return TempFileOrErr.takeError();
  if (std::error_code EC = sys::fs::openFileForWrite(*TempFileOrErr, FD))
    return errorCodeToError(EC);

  auto OS = std::make_unique<llvm::raw_fd_ostream>(FD, true);

  legacy::PassManager CodeGenPasses;
  TargetLibraryInfoImpl TLII(M.getTargetTriple());
  CodeGenPasses.add(new TargetLibraryInfoWrapperPass(TLII));
  if (TM->addPassesToEmitFile(CodeGenPasses, *OS, nullptr,
                              CodeGenFileType::ObjectFile))
    return createStringError("Failed to execute host backend");
  CodeGenPasses.run(M);

  return *TempFileOrErr;
}

/// Creates the object file containing the device image and runtime
/// registration code from the device images stored in \p Images.
Expected<StringRef>
wrapDeviceImages(ArrayRef<std::unique_ptr<MemoryBuffer>> Buffers,
                 const ArgList &Args, OffloadKind Kind) {
  llvm::TimeTraceScope TimeScope("Wrap bundled images");

  SmallVector<ArrayRef<char>, 4> BuffersToWrap;
  for (const auto &Buffer : Buffers)
    BuffersToWrap.emplace_back(
        ArrayRef<char>(Buffer->getBufferStart(), Buffer->getBufferSize()));

  LLVMContext Context;
  Module M("offload.wrapper.module", Context);
  M.setTargetTriple(Triple(
      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple())));

  switch (Kind) {
  case OFK_OpenMP:
    if (Error Err = offloading::wrapOpenMPBinaries(
            M, BuffersToWrap, offloading::getOffloadEntryArray(M),
            /*Suffix=*/"", /*Relocatable=*/Args.hasArg(OPT_relocatable)))
      return std::move(Err);
    break;
  case OFK_Cuda:
    if (Error Err = offloading::wrapCudaBinary(
            M, BuffersToWrap.front(), offloading::getOffloadEntryArray(M),
            /*Suffix=*/"", /*EmitSurfacesAndTextures=*/false))
      return std::move(Err);
    break;
  case OFK_HIP:
    if (Error Err = offloading::wrapHIPBinary(
            M, BuffersToWrap.front(), offloading::getOffloadEntryArray(M)))
      return std::move(Err);
    break;
  case OFK_SYCL: {
    // TODO: fill these options once the Driver supports them.
    offloading::SYCLJITOptions Options;
    if (Error Err =
            offloading::wrapSYCLBinaries(M, BuffersToWrap.front(), Options))
      return std::move(Err);
    break;
  }
  default:
    return createStringError(getOffloadKindName(Kind) +
                             " wrapping is not supported");
  }

  if (Args.hasArg(OPT_print_wrapped_module))
    errs() << M;
  if (Args.hasArg(OPT_save_temps)) {
    int FD = -1;
    auto TempFileOrErr = createOutputFile(
        ExecutableName + "." + getOffloadKindName(Kind) + ".image.wrapper",
        "bc");
    if (!TempFileOrErr)
      return TempFileOrErr.takeError();
    if (std::error_code EC = sys::fs::openFileForWrite(*TempFileOrErr, FD))
      return errorCodeToError(EC);
    llvm::raw_fd_ostream OS(FD, true);
    WriteBitcodeToFile(M, OS);
  }

  auto FileOrErr = compileModule(M, Kind);
  if (!FileOrErr)
    return FileOrErr.takeError();
  return *FileOrErr;
}

Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleOpenMP(ArrayRef<OffloadingImage> Images) {
  SmallVector<std::unique_ptr<MemoryBuffer>> Buffers;
  for (const OffloadingImage &Image : Images)
    Buffers.emplace_back(
        MemoryBuffer::getMemBufferCopy(OffloadBinary::write(Image)));

  return std::move(Buffers);
}

Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleSYCL(ArrayRef<OffloadingImage> Images) {
  SmallVector<std::unique_ptr<MemoryBuffer>> Buffers;
  for (const OffloadingImage &Image : Images) {
    // clang-sycl-linker packs outputs into one binary blob. Therefore, it is
    // passed to Offload Wrapper as is.
    StringRef S(Image.Image->getBufferStart(), Image.Image->getBufferSize());
    Buffers.emplace_back(MemoryBuffer::getMemBufferCopy(S));
  }

  return std::move(Buffers);
}

Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleCuda(ArrayRef<OffloadingImage> Images, const ArgList &Args) {
  SmallVector<std::pair<StringRef, StringRef>, 4> InputFiles;
  for (const OffloadingImage &Image : Images)
    InputFiles.emplace_back(std::make_pair(Image.Image->getBufferIdentifier(),
                                           Image.StringData.lookup("arch")));

  auto FileOrErr = nvptx::fatbinary(InputFiles, Args);
  if (!FileOrErr)
    return FileOrErr.takeError();

  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> ImageOrError =
      llvm::MemoryBuffer::getFileOrSTDIN(*FileOrErr);

  SmallVector<std::unique_ptr<MemoryBuffer>> Buffers;
  if (std::error_code EC = ImageOrError.getError())
    return createFileError(*FileOrErr, EC);
  Buffers.emplace_back(std::move(*ImageOrError));

  return std::move(Buffers);
}

Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleHIP(ArrayRef<OffloadingImage> Images, const ArgList &Args) {
  SmallVector<std::tuple<StringRef, StringRef, StringRef>, 4> InputFiles;
  for (const OffloadingImage &Image : Images)
    InputFiles.emplace_back(std::make_tuple(Image.Image->getBufferIdentifier(),
                                            Image.StringData.lookup("triple"),
                                            Image.StringData.lookup("arch")));

  auto FileOrErr = amdgcn::fatbinary(InputFiles, Args);
  if (!FileOrErr)
    return FileOrErr.takeError();

  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> ImageOrError =
      llvm::MemoryBuffer::getFileOrSTDIN(*FileOrErr);

  SmallVector<std::unique_ptr<MemoryBuffer>> Buffers;
  if (std::error_code EC = ImageOrError.getError())
    return createFileError(*FileOrErr, EC);
  Buffers.emplace_back(std::move(*ImageOrError));

  return std::move(Buffers);
}

/// Transforms the input \p Images into the binary format the runtime expects
/// for the given \p Kind.
Expected<SmallVector<std::unique_ptr<MemoryBuffer>>>
bundleLinkedOutput(ArrayRef<OffloadingImage> Images, const ArgList &Args,
                   OffloadKind Kind) {
  llvm::TimeTraceScope TimeScope("Bundle linked output");
  switch (Kind) {
  case OFK_OpenMP:
    return bundleOpenMP(Images);
  case OFK_SYCL:
    return bundleSYCL(Images);
  case OFK_Cuda:
    return bundleCuda(Images, Args);
  case OFK_HIP:
    return bundleHIP(Images, Args);
  default:
    return createStringError(getOffloadKindName(Kind) +
                             " bundling is not supported");
  }
}

/// Returns a new ArgList containing arguments used for the device linking
/// phase.
DerivedArgList getLinkerArgs(ArrayRef<OffloadFile> Input,
                             const InputArgList &Args) {
  DerivedArgList DAL(Args);
  for (Arg *A : Args)
    DAL.append(A);

  // Set the subarchitecture and target triple for this compilation.
  const OptTable &Tbl = getOptTable();
  StringRef Arch = Args.MakeArgString(Input.front().getBinary()->getArch());
  DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_arch_EQ),
                   Arch == "generic" ? "" : Arch);
  DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_triple_EQ),
                   Args.MakeArgString(Input.front().getBinary()->getTriple()));

  // If every input file is bitcode we have whole program visibility as we
  // do only support static linking with bitcode.
  auto ContainsBitcode = [](const OffloadFile &F) {
    return identify_magic(F.getBinary()->getImage()) == file_magic::bitcode;
  };
  if (llvm::all_of(Input, ContainsBitcode))
    DAL.AddFlagArg(nullptr, Tbl.getOption(OPT_whole_program));

  // Forward '-Xoffload-linker' options to the appropriate backend.
  for (StringRef Arg : Args.getAllArgValues(OPT_device_linker_args_EQ)) {
    auto [Triple, Value] = Arg.split('=');
    llvm::Triple TT(Triple);
    // If this isn't a recognized triple then it's an `arg=value` option.
    if (TT.getArch() == Triple::ArchType::UnknownArch)
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_linker_arg_EQ),
                       Args.MakeArgString(Arg));
    else if (Value.empty())
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_linker_arg_EQ),
                       Args.MakeArgString(Triple));
    else if (Triple == DAL.getLastArgValue(OPT_triple_EQ))
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_linker_arg_EQ),
                       Args.MakeArgString(Value));
  }

  // Forward '-Xoffload-compiler' options to the appropriate backend.
  for (StringRef Arg : Args.getAllArgValues(OPT_device_compiler_args_EQ)) {
    auto [Triple, Value] = Arg.split('=');
    llvm::Triple TT(Triple);
    // If this isn't a recognized triple then it's an `arg=value` option.
    if (TT.getArch() == Triple::ArchType::UnknownArch)
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_compiler_arg_EQ),
                       Args.MakeArgString(Arg));
    else if (Value.empty())
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_compiler_arg_EQ),
                       Args.MakeArgString(Triple));
    else if (Triple == DAL.getLastArgValue(OPT_triple_EQ))
      DAL.AddJoinedArg(nullptr, Tbl.getOption(OPT_compiler_arg_EQ),
                       Args.MakeArgString(Value));
  }

  return DAL;
}

Error handleOverrideImages(
    const InputArgList &Args,
    MapVector<OffloadKind, SmallVector<OffloadingImage, 0>> &Images) {
  for (StringRef Arg : Args.getAllArgValues(OPT_override_image)) {
    OffloadKind Kind = getOffloadKind(Arg.split("=").first);
    StringRef Filename = Arg.split("=").second;

    ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
        MemoryBuffer::getFileOrSTDIN(Filename);
    if (std::error_code EC = BufferOrErr.getError())
      return createFileError(Filename, EC);

    Expected<std::unique_ptr<ObjectFile>> ElfOrErr =
        ObjectFile::createELFObjectFile(**BufferOrErr,
                                        /*InitContent=*/false);
    if (!ElfOrErr)
      return ElfOrErr.takeError();
    ObjectFile &Elf = **ElfOrErr;

    OffloadingImage TheImage{};
    TheImage.TheImageKind = IMG_Object;
    TheImage.TheOffloadKind = Kind;
    TheImage.StringData["triple"] =
        Args.MakeArgString(Elf.makeTriple().getTriple());
    if (std::optional<StringRef> CPU = Elf.tryGetCPUName())
      TheImage.StringData["arch"] = Args.MakeArgString(*CPU);
    TheImage.Image = std::move(*BufferOrErr);

    Images[Kind].emplace_back(std::move(TheImage));
  }
  return Error::success();
}

/// Transforms all the extracted offloading input files into an image that can
/// be registered by the runtime. If NeedsWrapping is false, writes bundled
/// output directly without wrapping or host linking.
Expected<SmallVector<StringRef>>
linkAndWrapDeviceFiles(ArrayRef<SmallVector<OffloadFile>> LinkerInputFiles,
                       InputArgList &Args, char **Argv, int Argc,
                       bool NeedsWrapping) {
  llvm::TimeTraceScope TimeScope("Handle all device input");

  std::mutex ImageMtx;
  MapVector<OffloadKind, SmallVector<OffloadingImage, 0>> Images;

  // Initialize the images with any overriding inputs.
  if (Args.hasArg(OPT_override_image))
    if (Error Err = handleOverrideImages(Args, Images))
      return std::move(Err);

  bool ExcludeNVPTX = Args.hasArg(OPT_no_nvptx_whole_archive);
  bool ExcludeAMDGPU = Args.hasArg(OPT_no_amdgpu_whole_archive);

  auto Err = parallelForEachError(LinkerInputFiles, [&](auto &Input) -> Error {
    llvm::TimeTraceScope TimeScope("Link device input");

    // Each thread needs its own copy of the base arguments to maintain
    // per-device argument storage of synthetic strings.
    const OptTable &Tbl = getOptTable();
    BumpPtrAllocator Alloc;
    StringSaver Saver(Alloc);
    auto BaseArgs =
        Tbl.parseArgs(Argc, Argv, OPT_INVALID, Saver, [](StringRef Err) {
          reportError(createStringError(Err));
        });
    auto LinkerArgs = getLinkerArgs(Input, BaseArgs);

    const llvm::Triple Triple(LinkerArgs.getLastArgValue(OPT_triple_EQ));
    if (Triple.isNVPTX() && ExcludeNVPTX)
      return Error::success();

    if (Triple.isAMDGPU() && ExcludeAMDGPU)
      return Error::success();

    uint16_t ActiveOffloadKindMask = 0u;
    for (const auto &File : Input)
      ActiveOffloadKindMask |= File.getBinary()->getOffloadKind();

    // Linking images of SYCL offload kind with images of other kind is not
    // supported.
    // TODO: Remove the above limitation.
    if ((ActiveOffloadKindMask & OFK_SYCL) &&
        ((ActiveOffloadKindMask ^ OFK_SYCL) != 0))
      return createStringError("Linking images of SYCL offload kind with "
                               "images of any other kind is not supported");

    // Write any remaining device inputs to an output file.
    SmallVector<StringRef> InputFiles;
    for (const OffloadFile &File : Input) {
      auto FileNameOrErr = writeOffloadFile(File);
      if (!FileNameOrErr)
        return FileNameOrErr.takeError();
      InputFiles.emplace_back(*FileNameOrErr);
    }

    // Link the remaining device files using the device linker.
    auto OutputOrErr =
        linkDevice(InputFiles, LinkerArgs, ActiveOffloadKindMask);
    if (!OutputOrErr)
      return OutputOrErr.takeError();

    // Store the offloading image for each linked output file.
    for (OffloadKind Kind = OFK_OpenMP; Kind != OFK_LAST;
         Kind = static_cast<OffloadKind>((uint16_t)(Kind) << 1)) {
      if ((ActiveOffloadKindMask & Kind) == 0)
        continue;
      llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> FileOrErr =
          llvm::MemoryBuffer::getFileOrSTDIN(*OutputOrErr);
      if (std::error_code EC = FileOrErr.getError()) {
        if (DryRun)
          FileOrErr = MemoryBuffer::getMemBuffer("");
        else
          return createFileError(*OutputOrErr, EC);
      }

      // Manually containerize offloading images not in ELF format.
      if (Error E = containerizeRawImage(*FileOrErr, Kind, LinkerArgs))
        return E;

      std::scoped_lock<decltype(ImageMtx)> Guard(ImageMtx);
      OffloadingImage TheImage{};
      TheImage.TheImageKind =
          Args.hasArg(OPT_embed_bitcode) ? IMG_Bitcode : IMG_Object;
      TheImage.TheOffloadKind = Kind;
      TheImage.StringData["triple"] =
          Args.MakeArgString(LinkerArgs.getLastArgValue(OPT_triple_EQ));
      TheImage.StringData["arch"] =
          Args.MakeArgString(LinkerArgs.getLastArgValue(OPT_arch_EQ));
      TheImage.Image = std::move(*FileOrErr);

      Images[Kind].emplace_back(std::move(TheImage));
    }
    return Error::success();
  });
  if (Err)
    return std::move(Err);

  // This option is specific to this link phase and the preceding link tools
  // do not understand this option so we remove it now that we're done with it.
  if (ExcludeNVPTX)
    Args.eraseArg(OPT_no_nvptx_whole_archive);
  if (ExcludeAMDGPU)
    Args.eraseArg(OPT_no_amdgpu_whole_archive);

  // Create a binary image of each offloading image and either embed it into a
  // new object file, or if all inputs were direct offload binaries, emit the
  // fat binary directly (e.g. .hipfb / .fatbin).
  SmallVector<StringRef> WrappedOutput;
  for (auto &[Kind, Input] : Images) {
    // We sort the entries before bundling so they appear in a deterministic
    // order in the final binary.
    llvm::sort(Input, [](OffloadingImage &A, OffloadingImage &B) {
      StringRef TripleA = A.StringData.lookup("triple");
      StringRef TripleB = B.StringData.lookup("triple");
      StringRef ArchA = A.StringData.lookup("arch");
      StringRef ArchB = B.StringData.lookup("arch");
      if (TripleA != TripleB)
        return TripleA > TripleB;
      if (ArchA != ArchB)
        return ArchA > ArchB;
      return A.TheOffloadKind < B.TheOffloadKind;
    });
    auto BundledImagesOrErr = bundleLinkedOutput(Input, Args, Kind);
    if (!BundledImagesOrErr)
      return BundledImagesOrErr.takeError();

    if (!NeedsWrapping) {
      if (BundledImagesOrErr->size() != 1)
        return createStringError(
            "Expected a single bundled image for direct fat binary output");

      Expected<std::unique_ptr<FileOutputBuffer>> FOBOrErr =
          FileOutputBuffer::create(
              ExecutableName, BundledImagesOrErr->front()->getBufferSize());
      if (!FOBOrErr)
        return FOBOrErr.takeError();
      std::unique_ptr<FileOutputBuffer> FOB = std::move(*FOBOrErr);
      llvm::copy(BundledImagesOrErr->front()->getBuffer(),
                 FOB->getBufferStart());
      if (Error E = FOB->commit())
        return std::move(E);

      continue;
    }

    auto OutputOrErr = wrapDeviceImages(*BundledImagesOrErr, Args, Kind);
    if (!OutputOrErr)
      return OutputOrErr.takeError();
    WrappedOutput.push_back(*OutputOrErr);
  }

  return WrappedOutput;
}

std::optional<std::string> findFile(StringRef Dir, StringRef Root,
                                    const Twine &Name) {
  SmallString<128> Path;
  if (Dir.starts_with("="))
    sys::path::append(Path, Root, Dir.substr(1), Name);
  else
    sys::path::append(Path, Dir, Name);

  if (sys::fs::exists(Path))
    return static_cast<std::string>(Path);
  return std::nullopt;
}

std::optional<std::string>
findFromSearchPaths(StringRef Name, StringRef Root,
                    ArrayRef<StringRef> SearchPaths) {
  for (StringRef Dir : SearchPaths)
    if (std::optional<std::string> File = findFile(Dir, Root, Name))
      return File;
  return std::nullopt;
}

std::optional<std::string>
searchLibraryBaseName(StringRef Name, StringRef Root,
                      ArrayRef<StringRef> SearchPaths) {
  for (StringRef Dir : SearchPaths) {
    if (std::optional<std::string> File =
            findFile(Dir, Root, "lib" + Name + ".so"))
      return File;
    if (std::optional<std::string> File =
            findFile(Dir, Root, "lib" + Name + ".a"))
      return File;
  }
  return std::nullopt;
}

/// Search for static libraries in the linker's library path given input like
/// `-lfoo` or `-l:libfoo.a`.
std::optional<std::string> searchLibrary(StringRef Input, StringRef Root,
                                         ArrayRef<StringRef> SearchPaths) {
  if (Input.starts_with(":"))
    return findFromSearchPaths(Input.drop_front(), Root, SearchPaths);
  if (Input.ends_with(".lib"))
    return findFromSearchPaths(Input, Root, SearchPaths);
  return searchLibraryBaseName(Input, Root, SearchPaths);
}

/// Search the input files and libraries for embedded device offloading code
/// and add it to the list of files to be linked. Files coming from static
/// libraries are only added to the input if they are used by an existing
/// input file. Returns a list of input files intended for a single linking job.
Expected<SmallVector<SmallVector<OffloadFile>>>
getDeviceInput(const ArgList &Args) {
  llvm::TimeTraceScope TimeScope("ExtractDeviceCode");

  // Skip all the input if the user is overriding the output.
  if (Args.hasArg(OPT_override_image))
    return SmallVector<SmallVector<OffloadFile>>();

  StringRef Root = Args.getLastArgValue(OPT_sysroot_EQ);
  SmallVector<StringRef> LibraryPaths;
  for (const opt::Arg *Arg : Args.filtered(OPT_library_path, OPT_libpath))
    LibraryPaths.push_back(Arg->getValue());

  BumpPtrAllocator Alloc;
  StringSaver Saver(Alloc);

  // Try to extract device code from the linker input files.
  bool WholeArchive = Args.hasArg(OPT_wholearchive_flag);
  SmallVector<OffloadFile> ObjectFilesToExtract;
  SmallVector<OffloadFile> ArchiveFilesToExtract;
  for (const opt::Arg *Arg : Args.filtered(
           OPT_INPUT, OPT_library, OPT_whole_archive, OPT_no_whole_archive)) {
    if (Arg->getOption().matches(OPT_whole_archive) ||
        Arg->getOption().matches(OPT_no_whole_archive)) {
      WholeArchive = Arg->getOption().matches(OPT_whole_archive);
      continue;
    }

    std::optional<std::string> Filename =
        Arg->getOption().matches(OPT_library)
            ? searchLibrary(Arg->getValue(), Root, LibraryPaths)
            : std::string(Arg->getValue());

    if (!Filename && Arg->getOption().matches(OPT_library))
      return createStringError("unable to find library -l%s", Arg->getValue());

    if (!Filename || !sys::fs::exists(*Filename) ||
        sys::fs::is_directory(*Filename))
      continue;

    ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
        MemoryBuffer::getFileOrSTDIN(*Filename);
    if (std::error_code EC = BufferOrErr.getError())
      return createFileError(*Filename, EC);

    MemoryBufferRef Buffer = **BufferOrErr;
    if (identify_magic(Buffer.getBuffer()) == file_magic::elf_shared_object)
      continue;

    SmallVector<OffloadFile> Binaries;
    if (Error Err = extractOffloadBinaries(Buffer, Binaries))
      return std::move(Err);

    for (auto &Binary : Binaries) {
      if (identify_magic(Buffer.getBuffer()) == file_magic::archive &&
          !WholeArchive)
        ArchiveFilesToExtract.emplace_back(std::move(Binary));
      else
        ObjectFilesToExtract.emplace_back(std::move(Binary));
    }
  }

  // Link all standard input files and update the list of symbols.
  MapVector<OffloadFile::TargetID, SmallVector<OffloadFile, 0>> InputFiles;
  for (OffloadFile &Binary : ObjectFilesToExtract) {
    if (!Binary.getBinary())
      continue;

    SmallVector<OffloadFile::TargetID> CompatibleTargets = {Binary};
    for (const auto &[ID, Input] : InputFiles)
      if (object::areTargetsCompatible(Binary, ID))
        CompatibleTargets.emplace_back(ID);

    for (const auto &[Index, ID] : llvm::enumerate(CompatibleTargets)) {
      // If another target needs this binary it must be copied instead.
      if (Index == CompatibleTargets.size() - 1)
        InputFiles[ID].emplace_back(std::move(Binary));
      else
        InputFiles[ID].emplace_back(Binary.copy());
    }
  }

  llvm::DenseSet<StringRef> ShouldExtract;
  for (auto &Arg : Args.getAllArgValues(OPT_should_extract))
    ShouldExtract.insert(Arg);

  // We only extract archive members from the fat binary if we find a used or
  // requested target. Unlike normal static archive handling, we just extract
  // every object file contained in the archive.
  for (OffloadFile &Binary : ArchiveFilesToExtract) {
    if (!Binary.getBinary())
      continue;

    SmallVector<OffloadFile::TargetID> CompatibleTargets = {Binary};
    for (const auto &[ID, Input] : InputFiles)
      if (object::areTargetsCompatible(Binary, ID))
        CompatibleTargets.emplace_back(ID);

    for (const auto &[Index, ID] : llvm::enumerate(CompatibleTargets)) {
      // Only extract if we have an object matching this target or it
      // was specifically requested.
      if (!InputFiles.count(ID) && !ShouldExtract.contains(ID.second))
        continue;

      // If another target needs this binary it must be copied instead.
      if (Index == CompatibleTargets.size() - 1)
        InputFiles[ID].emplace_back(std::move(Binary));
      else
        InputFiles[ID].emplace_back(Binary.copy());
    }
  }

  SmallVector<SmallVector<OffloadFile>> InputsForTarget;
  for (auto &[ID, Input] : InputFiles)
    InputsForTarget.emplace_back(std::move(Input));

  return std::move(InputsForTarget);
}

} // namespace

int main(int Argc, char **Argv) {
  InitLLVM X(Argc, Argv);
  InitializeAllTargetInfos();
  InitializeAllTargets();
  InitializeAllTargetMCs();
  InitializeAllAsmParsers();
  InitializeAllAsmPrinters();

  LinkerExecutable = Argv[0];
  sys::PrintStackTraceOnErrorSignal(Argv[0]);

  const OptTable &Tbl = getOptTable();
  BumpPtrAllocator Alloc;
  StringSaver Saver(Alloc);
  auto Args = Tbl.parseArgs(Argc, Argv, OPT_INVALID, Saver, [&](StringRef Err) {
    reportError(createStringError(Err));
  });

  if (Args.hasArg(OPT_help) || Args.hasArg(OPT_help_hidden)) {
    Tbl.printHelp(
        outs(),
        "clang-linker-wrapper [options] -- <options to pass to the linker>",
        "\nA wrapper utility over the host linker. It scans the input files\n"
        "for sections that require additional processing prior to linking.\n"
        "It will then transparently pass all arguments and input to the\n"
        "specified host linker to create the final binary.\n",
        Args.hasArg(OPT_help_hidden), Args.hasArg(OPT_help_hidden));
    return EXIT_SUCCESS;
  }
  if (Args.hasArg(OPT_version)) {
    printVersion(outs());
    return EXIT_SUCCESS;
  }

  // This forwards '-mllvm' arguments to LLVM if present.
  SmallVector<const char *> NewArgv = {Argv[0]};
  for (const opt::Arg *Arg : Args.filtered(OPT_mllvm))
    NewArgv.push_back(Arg->getValue());
  for (const opt::Arg *Arg : Args.filtered(OPT_offload_opt_eq_minus))
    NewArgv.push_back(Arg->getValue());
  SmallVector<PassPlugin, 1> PluginList;
  PassPlugins.setCallback([&](const std::string &PluginPath) {
    auto Plugin = PassPlugin::Load(PluginPath);
    if (!Plugin)
      reportFatalUsageError(Plugin.takeError());
    PluginList.emplace_back(Plugin.get());
  });
  cl::ParseCommandLineOptions(NewArgv.size(), &NewArgv[0]);

  Verbose = Args.hasArg(OPT_verbose);
  DryRun = Args.hasArg(OPT_dry_run);
  SaveTemps = Args.hasArg(OPT_save_temps);
  CudaBinaryPath = Args.getLastArgValue(OPT_cuda_path_EQ).str();
  CanonicalPrefixes = !Args.hasArg(OPT_no_canonical_prefixes);

  llvm::Triple Triple(
      Args.getLastArgValue(OPT_host_triple_EQ, sys::getDefaultTargetTriple()));
  if (Args.hasArg(OPT_o))
    ExecutableName = Args.getLastArgValue(OPT_o, "a.out");
  else if (Args.hasArg(OPT_out))
    ExecutableName = Args.getLastArgValue(OPT_out, "a.exe");
  else
    ExecutableName = Triple.isOSWindows() ? "a.exe" : "a.out";

  parallel::strategy = hardware_concurrency(1);
  if (auto *Arg = Args.getLastArg(OPT_wrapper_jobs)) {
    StringRef Val = Arg->getValue();
    if (Val.equals_insensitive("jobserver"))
      parallel::strategy = jobserver_concurrency();
    else {
      unsigned Threads = 0;
      if (!llvm::to_integer(Val, Threads) || Threads == 0)
        reportError(createStringError(
            "%s: expected a positive integer or 'jobserver', got '%s'",
            Arg->getSpelling().data(), Val.data()));
      else
        parallel::strategy = hardware_concurrency(Threads);
    }
  }

  if (Args.hasArg(OPT_wrapper_time_trace_eq)) {
    unsigned Granularity;
    if (Args.getLastArgValue(OPT_wrapper_time_trace_granularity, "500")
            .getAsInteger(10, Granularity))
      reportError(
          createStringError("invalid value for time trace granularity"));
    timeTraceProfilerInitialize(Granularity, Argv[0]);
  }

  {
    llvm::TimeTraceScope TimeScope("Execute linker wrapper");

    // Extract the device input files stored in the host fat binary.
    auto DeviceInputFiles = getDeviceInput(Args);
    if (!DeviceInputFiles)
      reportError(DeviceInputFiles.takeError());

    // Check if we should emit fat binary directly without wrapping or host
    // linking.
    bool EmitFatbinOnly = Args.hasArg(OPT_emit_fatbin_only);

    // Link and process the device images. The function may emit a direct fat
    // binary if --emit-fatbin-only is specified.
    auto FilesOrErr = linkAndWrapDeviceFiles(*DeviceInputFiles, Args, Argv,
                                             Argc, !EmitFatbinOnly);
    if (!FilesOrErr)
      reportError(FilesOrErr.takeError());

    // Run the host linking job with the rendered arguments.
    if (!EmitFatbinOnly) {
      if (Error Err = runLinker(*FilesOrErr, Args))
        reportError(std::move(Err));
    }
  }

  if (const opt::Arg *Arg = Args.getLastArg(OPT_wrapper_time_trace_eq)) {
    if (Error Err = timeTraceProfilerWrite(Arg->getValue(), ExecutableName))
      reportError(std::move(Err));
    timeTraceProfilerCleanup();
  }

  // Remove the temporary files created.
  if (!SaveTemps)
    for (const auto &TempFile : TempFiles)
      if (std::error_code EC = sys::fs::remove(TempFile))
        reportError(createFileError(TempFile, EC));

  return EXIT_SUCCESS;
}