rust/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

#include <stdio.h>

#include <iomanip>
#include <vector>
#include <set>

#include "LLVMWrapper.h"

#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/AutoUpgrade.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Verifier.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Passes/PassBuilder.h"
#include "llvm/Passes/PassPlugin.h"
#include "llvm/Passes/StandardInstrumentations.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/FileSystem.h"
#if LLVM_VERSION_GE(17, 0)
#include "llvm/Support/VirtualFileSystem.h"
#endif
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/IPO/AlwaysInliner.h"
#include "llvm/Transforms/IPO/FunctionImport.h"
#include "llvm/Transforms/IPO/Internalize.h"
#include "llvm/Transforms/IPO/LowerTypeTests.h"
#include "llvm/Transforms/IPO/ThinLTOBitcodeWriter.h"
#include "llvm/Transforms/Utils/AddDiscriminators.h"
#include "llvm/Transforms/Utils/FunctionImportUtils.h"
#include "llvm/LTO/LTO.h"
#include "llvm/Bitcode/BitcodeWriter.h"

#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Instrumentation/AddressSanitizer.h"
#include "llvm/Support/TimeProfiler.h"
#include "llvm/Transforms/Instrumentation/GCOVProfiler.h"
#include "llvm/Transforms/Instrumentation/InstrProfiling.h"
#include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
#include "llvm/Transforms/Instrumentation/MemorySanitizer.h"
#include "llvm/Transforms/Instrumentation/HWAddressSanitizer.h"
#include "llvm/Transforms/Utils/CanonicalizeAliases.h"
#include "llvm/Transforms/Utils/NameAnonGlobals.h"
#include "llvm/Transforms/Utils.h"

using namespace llvm;

typedef struct LLVMOpaquePass *LLVMPassRef;
typedef struct LLVMOpaqueTargetMachine *LLVMTargetMachineRef;

DEFINE_STDCXX_CONVERSION_FUNCTIONS(Pass, LLVMPassRef)
DEFINE_STDCXX_CONVERSION_FUNCTIONS(TargetMachine, LLVMTargetMachineRef)

extern "C" void LLVMTimeTraceProfilerInitialize() {
  timeTraceProfilerInitialize(
      /* TimeTraceGranularity */ 0,
      /* ProcName */ "rustc");
}

extern "C" void LLVMTimeTraceProfilerFinishThread() {
  timeTraceProfilerFinishThread();
}

extern "C" void LLVMTimeTraceProfilerFinish(const char* FileName) {
  StringRef FN(FileName);
  std::error_code EC;
  raw_fd_ostream OS(FN, EC, sys::fs::CD_CreateAlways);

  timeTraceProfilerWrite(OS);
  timeTraceProfilerCleanup();
}

#ifdef LLVM_COMPONENT_X86
#define SUBTARGET_X86 SUBTARGET(X86)
#else
#define SUBTARGET_X86
#endif

#ifdef LLVM_COMPONENT_ARM
#define SUBTARGET_ARM SUBTARGET(ARM)
#else
#define SUBTARGET_ARM
#endif

#ifdef LLVM_COMPONENT_AARCH64
#define SUBTARGET_AARCH64 SUBTARGET(AArch64)
#else
#define SUBTARGET_AARCH64
#endif

#ifdef LLVM_COMPONENT_AVR
#define SUBTARGET_AVR SUBTARGET(AVR)
#else
#define SUBTARGET_AVR
#endif

#ifdef LLVM_COMPONENT_M68k
#define SUBTARGET_M68K SUBTARGET(M68k)
#else
#define SUBTARGET_M68K
#endif

#ifdef LLVM_COMPONENT_CSKY
#define SUBTARGET_CSKY SUBTARGET(CSKY)
#else
#define SUBTARGET_CSKY
#endif

#ifdef LLVM_COMPONENT_MIPS
#define SUBTARGET_MIPS SUBTARGET(Mips)
#else
#define SUBTARGET_MIPS
#endif

#ifdef LLVM_COMPONENT_POWERPC
#define SUBTARGET_PPC SUBTARGET(PPC)
#else
#define SUBTARGET_PPC
#endif

#ifdef LLVM_COMPONENT_SYSTEMZ
#define SUBTARGET_SYSTEMZ SUBTARGET(SystemZ)
#else
#define SUBTARGET_SYSTEMZ
#endif

#ifdef LLVM_COMPONENT_MSP430
#define SUBTARGET_MSP430 SUBTARGET(MSP430)
#else
#define SUBTARGET_MSP430
#endif

#ifdef LLVM_COMPONENT_RISCV
#define SUBTARGET_RISCV SUBTARGET(RISCV)
#else
#define SUBTARGET_RISCV
#endif

#ifdef LLVM_COMPONENT_SPARC
#define SUBTARGET_SPARC SUBTARGET(Sparc)
#else
#define SUBTARGET_SPARC
#endif

#ifdef LLVM_COMPONENT_HEXAGON
#define SUBTARGET_HEXAGON SUBTARGET(Hexagon)
#else
#define SUBTARGET_HEXAGON
#endif

#ifdef LLVM_COMPONENT_LOONGARCH
#define SUBTARGET_LOONGARCH SUBTARGET(LoongArch)
#else
#define SUBTARGET_LOONGARCH
#endif

#define GEN_SUBTARGETS                                                         \
  SUBTARGET_X86                                                                \
  SUBTARGET_ARM                                                                \
  SUBTARGET_AARCH64                                                            \
  SUBTARGET_AVR                                                                \
  SUBTARGET_M68K                                                               \
  SUBTARGET_CSKY                                                               \
  SUBTARGET_MIPS                                                               \
  SUBTARGET_PPC                                                                \
  SUBTARGET_SYSTEMZ                                                            \
  SUBTARGET_MSP430                                                             \
  SUBTARGET_SPARC                                                              \
  SUBTARGET_HEXAGON                                                            \
  SUBTARGET_RISCV                                                              \
  SUBTARGET_LOONGARCH                                                          \

#define SUBTARGET(x)                                                           \
  namespace llvm {                                                             \
  extern const SubtargetFeatureKV x##FeatureKV[];                              \
  extern const SubtargetFeatureKV x##SubTypeKV[];                              \
  }

GEN_SUBTARGETS
#undef SUBTARGET

extern "C" bool LLVMRustHasFeature(LLVMTargetMachineRef TM,
                                   const char *Feature) {
  TargetMachine *Target = unwrap(TM);
  const MCSubtargetInfo *MCInfo = Target->getMCSubtargetInfo();
  return MCInfo->checkFeatures(std::string("+") + Feature);
}

enum class LLVMRustCodeModel {
  Tiny,
  Small,
  Kernel,
  Medium,
  Large,
  None,
};

#if LLVM_VERSION_LT(16, 0)
static Optional<CodeModel::Model>
#else
static std::optional<CodeModel::Model>
#endif
fromRust(LLVMRustCodeModel Model) {
  switch (Model) {
  case LLVMRustCodeModel::Tiny:
    return CodeModel::Tiny;
  case LLVMRustCodeModel::Small:
    return CodeModel::Small;
  case LLVMRustCodeModel::Kernel:
    return CodeModel::Kernel;
  case LLVMRustCodeModel::Medium:
    return CodeModel::Medium;
  case LLVMRustCodeModel::Large:
    return CodeModel::Large;
  case LLVMRustCodeModel::None:
#if LLVM_VERSION_LT(16, 0)
    return None;
#else
    return std::nullopt;
#endif
  default:
    report_fatal_error("Bad CodeModel.");
  }
}

enum class LLVMRustCodeGenOptLevel {
  None,
  Less,
  Default,
  Aggressive,
};

static CodeGenOpt::Level fromRust(LLVMRustCodeGenOptLevel Level) {
  switch (Level) {
  case LLVMRustCodeGenOptLevel::None:
    return CodeGenOpt::None;
  case LLVMRustCodeGenOptLevel::Less:
    return CodeGenOpt::Less;
  case LLVMRustCodeGenOptLevel::Default:
    return CodeGenOpt::Default;
  case LLVMRustCodeGenOptLevel::Aggressive:
    return CodeGenOpt::Aggressive;
  default:
    report_fatal_error("Bad CodeGenOptLevel.");
  }
}

enum class LLVMRustPassBuilderOptLevel {
  O0,
  O1,
  O2,
  O3,
  Os,
  Oz,
};

static OptimizationLevel fromRust(LLVMRustPassBuilderOptLevel Level) {
  switch (Level) {
  case LLVMRustPassBuilderOptLevel::O0:
    return OptimizationLevel::O0;
  case LLVMRustPassBuilderOptLevel::O1:
    return OptimizationLevel::O1;
  case LLVMRustPassBuilderOptLevel::O2:
    return OptimizationLevel::O2;
  case LLVMRustPassBuilderOptLevel::O3:
    return OptimizationLevel::O3;
  case LLVMRustPassBuilderOptLevel::Os:
    return OptimizationLevel::Os;
  case LLVMRustPassBuilderOptLevel::Oz:
    return OptimizationLevel::Oz;
  default:
    report_fatal_error("Bad PassBuilderOptLevel.");
  }
}

enum class LLVMRustRelocModel {
  Static,
  PIC,
  DynamicNoPic,
  ROPI,
  RWPI,
  ROPIRWPI,
};

static Reloc::Model fromRust(LLVMRustRelocModel RustReloc) {
  switch (RustReloc) {
  case LLVMRustRelocModel::Static:
    return Reloc::Static;
  case LLVMRustRelocModel::PIC:
    return Reloc::PIC_;
  case LLVMRustRelocModel::DynamicNoPic:
    return Reloc::DynamicNoPIC;
  case LLVMRustRelocModel::ROPI:
    return Reloc::ROPI;
  case LLVMRustRelocModel::RWPI:
    return Reloc::RWPI;
  case LLVMRustRelocModel::ROPIRWPI:
    return Reloc::ROPI_RWPI;
  }
  report_fatal_error("Bad RelocModel.");
}

/// getLongestEntryLength - Return the length of the longest entry in the table.
template<typename KV>
static size_t getLongestEntryLength(ArrayRef<KV> Table) {
  size_t MaxLen = 0;
  for (auto &I : Table)
    MaxLen = std::max(MaxLen, std::strlen(I.Key));
  return MaxLen;
}

using PrintBackendInfo = void(void*, const char* Data, size_t Len);

extern "C" void LLVMRustPrintTargetCPUs(LLVMTargetMachineRef TM,
                                        const char* TargetCPU,
                                        PrintBackendInfo Print,
                                        void* Out) {
  const TargetMachine *Target = unwrap(TM);
  const MCSubtargetInfo *MCInfo = Target->getMCSubtargetInfo();
  const Triple::ArchType HostArch = Triple(sys::getDefaultTargetTriple()).getArch();
  const Triple::ArchType TargetArch = Target->getTargetTriple().getArch();

  std::ostringstream Buf;

#if LLVM_VERSION_GE(17, 0)
  const ArrayRef<SubtargetSubTypeKV> CPUTable = MCInfo->getAllProcessorDescriptions();
#else
  Buf << "Full target CPU help is not supported by this LLVM version.\n\n";
  SubtargetSubTypeKV TargetCPUKV = { TargetCPU, {{}}, {{}} };
  const ArrayRef<SubtargetSubTypeKV> CPUTable = TargetCPUKV;
#endif
  unsigned MaxCPULen = getLongestEntryLength(CPUTable);

  Buf << "Available CPUs for this target:\n";
  // Don't print the "native" entry when the user specifies --target with a
  // different arch since that could be wrong or misleading.
  if (HostArch == TargetArch) {
    MaxCPULen = std::max(MaxCPULen, (unsigned) std::strlen("native"));
    const StringRef HostCPU = sys::getHostCPUName();
    Buf << "    " << std::left << std::setw(MaxCPULen) << "native"
        << " - Select the CPU of the current host "
           "(currently " << HostCPU.str() << ").\n";
  }
  for (auto &CPU : CPUTable) {
    // Compare cpu against current target to label the default
    if (strcmp(CPU.Key, TargetCPU) == 0) {
      Buf << "    " << std::left << std::setw(MaxCPULen) << CPU.Key
          << " - This is the default target CPU for the current build target "
             "(currently " << Target->getTargetTriple().str() << ").";
    }
    else {
      Buf << "    " << CPU.Key;
    }
    Buf << "\n";
  }

  const auto &BufString = Buf.str();
  Print(Out, BufString.data(), BufString.size());
}

extern "C" size_t LLVMRustGetTargetFeaturesCount(LLVMTargetMachineRef TM) {
#ifdef LLVM_RUSTLLVM
  const TargetMachine *Target = unwrap(TM);
  const MCSubtargetInfo *MCInfo = Target->getMCSubtargetInfo();
  const ArrayRef<SubtargetFeatureKV> FeatTable = MCInfo->getFeatureTable();
  return FeatTable.size();
#else
  return 0;
#endif
}

extern "C" void LLVMRustGetTargetFeature(LLVMTargetMachineRef TM, size_t Index,
                                         const char** Feature, const char** Desc) {
#ifdef LLVM_RUSTLLVM
  const TargetMachine *Target = unwrap(TM);
  const MCSubtargetInfo *MCInfo = Target->getMCSubtargetInfo();
  const ArrayRef<SubtargetFeatureKV> FeatTable = MCInfo->getFeatureTable();
  const SubtargetFeatureKV Feat = FeatTable[Index];
  *Feature = Feat.Key;
  *Desc = Feat.Desc;
#endif
}

extern "C" const char* LLVMRustGetHostCPUName(size_t *len) {
  StringRef Name = sys::getHostCPUName();
  *len = Name.size();
  return Name.data();
}

extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine(
    const char *TripleStr, const char *CPU, const char *Feature,
    const char *ABIStr, LLVMRustCodeModel RustCM, LLVMRustRelocModel RustReloc,
    LLVMRustCodeGenOptLevel RustOptLevel, bool UseSoftFloat,
    bool FunctionSections,
    bool DataSections,
    bool UniqueSectionNames,
    bool TrapUnreachable,
    bool Singlethread,
    bool AsmComments,
    bool EmitStackSizeSection,
    bool RelaxELFRelocations,
    bool UseInitArray,
    const char *SplitDwarfFile,
    bool ForceEmulatedTls) {

  auto OptLevel = fromRust(RustOptLevel);
  auto RM = fromRust(RustReloc);
  auto CM = fromRust(RustCM);

  std::string Error;
  Triple Trip(Triple::normalize(TripleStr));
  const llvm::Target *TheTarget =
      TargetRegistry::lookupTarget(Trip.getTriple(), Error);
  if (TheTarget == nullptr) {
    LLVMRustSetLastError(Error.c_str());
    return nullptr;
  }

  TargetOptions Options;

  Options.FloatABIType = FloatABI::Default;
  if (UseSoftFloat) {
    Options.FloatABIType = FloatABI::Soft;
  }
  Options.DataSections = DataSections;
  Options.FunctionSections = FunctionSections;
  Options.UniqueSectionNames = UniqueSectionNames;
  Options.MCOptions.AsmVerbose = AsmComments;
  Options.MCOptions.PreserveAsmComments = AsmComments;
  Options.MCOptions.ABIName = ABIStr;
  if (SplitDwarfFile) {
      Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
  }
  Options.RelaxELFRelocations = RelaxELFRelocations;
  Options.UseInitArray = UseInitArray;

#if LLVM_VERSION_LT(17, 0)
  if (ForceEmulatedTls) {
    Options.ExplicitEmulatedTLS = true;
    Options.EmulatedTLS = true;
  }
#else
  Options.EmulatedTLS = ForceEmulatedTls || Trip.hasDefaultEmulatedTLS();
#endif

  if (TrapUnreachable) {
    // Tell LLVM to codegen `unreachable` into an explicit trap instruction.
    // This limits the extent of possible undefined behavior in some cases, as
    // it prevents control flow from "falling through" into whatever code
    // happens to be laid out next in memory.
    Options.TrapUnreachable = true;
  }

  if (Singlethread) {
    Options.ThreadModel = ThreadModel::Single;
  }

  Options.EmitStackSizeSection = EmitStackSizeSection;

  TargetMachine *TM = TheTarget->createTargetMachine(
      Trip.getTriple(), CPU, Feature, Options, RM, CM, OptLevel);
  return wrap(TM);
}

extern "C" void LLVMRustDisposeTargetMachine(LLVMTargetMachineRef TM) {
  delete unwrap(TM);
}

// Unfortunately, the LLVM C API doesn't provide a way to create the
// TargetLibraryInfo pass, so we use this method to do so.
extern "C" void LLVMRustAddLibraryInfo(LLVMPassManagerRef PMR, LLVMModuleRef M,
                                       bool DisableSimplifyLibCalls) {
  Triple TargetTriple(unwrap(M)->getTargetTriple());
  TargetLibraryInfoImpl TLII(TargetTriple);
  if (DisableSimplifyLibCalls)
    TLII.disableAllFunctions();
  unwrap(PMR)->add(new TargetLibraryInfoWrapperPass(TLII));
}

extern "C" void LLVMRustSetLLVMOptions(int Argc, char **Argv) {
  // Initializing the command-line options more than once is not allowed. So,
  // check if they've already been initialized. (This could happen if we're
  // being called from rustpkg, for example). If the arguments change, then
  // that's just kinda unfortunate.
  static bool Initialized = false;
  if (Initialized)
    return;
  Initialized = true;
  cl::ParseCommandLineOptions(Argc, Argv);
}

enum class LLVMRustFileType {
  AssemblyFile,
  ObjectFile,
};

static CodeGenFileType fromRust(LLVMRustFileType Type) {
  switch (Type) {
  case LLVMRustFileType::AssemblyFile:
    return CGFT_AssemblyFile;
  case LLVMRustFileType::ObjectFile:
    return CGFT_ObjectFile;
  default:
    report_fatal_error("Bad FileType.");
  }
}

extern "C" LLVMRustResult
LLVMRustWriteOutputFile(LLVMTargetMachineRef Target, LLVMPassManagerRef PMR,
                        LLVMModuleRef M, const char *Path, const char *DwoPath,
                        LLVMRustFileType RustFileType) {
  llvm::legacy::PassManager *PM = unwrap<llvm::legacy::PassManager>(PMR);
  auto FileType = fromRust(RustFileType);

  std::string ErrorInfo;
  std::error_code EC;
  raw_fd_ostream OS(Path, EC, sys::fs::OF_None);
  if (EC)
    ErrorInfo = EC.message();
  if (ErrorInfo != "") {
    LLVMRustSetLastError(ErrorInfo.c_str());
    return LLVMRustResult::Failure;
  }

  buffer_ostream BOS(OS);
  if (DwoPath) {
    raw_fd_ostream DOS(DwoPath, EC, sys::fs::OF_None);
    EC.clear();
    if (EC)
        ErrorInfo = EC.message();
    if (ErrorInfo != "") {
      LLVMRustSetLastError(ErrorInfo.c_str());
      return LLVMRustResult::Failure;
    }
    buffer_ostream DBOS(DOS);
    unwrap(Target)->addPassesToEmitFile(*PM, BOS, &DBOS, FileType, false);
    PM->run(*unwrap(M));
  } else {
    unwrap(Target)->addPassesToEmitFile(*PM, BOS, nullptr, FileType, false);
    PM->run(*unwrap(M));
  }

  // Apparently `addPassesToEmitFile` adds a pointer to our on-the-stack output
  // stream (OS), so the only real safe place to delete this is here? Don't we
  // wish this was written in Rust?
  LLVMDisposePassManager(PMR);
  return LLVMRustResult::Success;
}

extern "C" typedef void (*LLVMRustSelfProfileBeforePassCallback)(void*, // LlvmSelfProfiler
                                                      const char*,      // pass name
                                                      const char*);     // IR name
extern "C" typedef void (*LLVMRustSelfProfileAfterPassCallback)(void*); // LlvmSelfProfiler

std::string LLVMRustwrappedIrGetName(const llvm::Any &WrappedIr) {
  if (const auto *Cast = any_cast<const Module *>(&WrappedIr))
    return (*Cast)->getName().str();
  if (const auto *Cast = any_cast<const Function *>(&WrappedIr))
    return (*Cast)->getName().str();
  if (const auto *Cast = any_cast<const Loop *>(&WrappedIr))
    return (*Cast)->getName().str();
  if (const auto *Cast = any_cast<const LazyCallGraph::SCC *>(&WrappedIr))
    return (*Cast)->getName();
  return "<UNKNOWN>";
}


void LLVMSelfProfileInitializeCallbacks(
    PassInstrumentationCallbacks& PIC, void* LlvmSelfProfiler,
    LLVMRustSelfProfileBeforePassCallback BeforePassCallback,
    LLVMRustSelfProfileAfterPassCallback AfterPassCallback) {
  PIC.registerBeforeNonSkippedPassCallback([LlvmSelfProfiler, BeforePassCallback](
                                           StringRef Pass, llvm::Any Ir) {
    std::string PassName = Pass.str();
    std::string IrName = LLVMRustwrappedIrGetName(Ir);
    BeforePassCallback(LlvmSelfProfiler, PassName.c_str(), IrName.c_str());
  });

  PIC.registerAfterPassCallback(
      [LlvmSelfProfiler, AfterPassCallback](StringRef Pass, llvm::Any IR,
                                            const PreservedAnalyses &Preserved) {
        AfterPassCallback(LlvmSelfProfiler);
      });

  PIC.registerAfterPassInvalidatedCallback(
      [LlvmSelfProfiler, AfterPassCallback](StringRef Pass, const PreservedAnalyses &Preserved) {
        AfterPassCallback(LlvmSelfProfiler);
      });

  PIC.registerBeforeAnalysisCallback([LlvmSelfProfiler, BeforePassCallback](
                                         StringRef Pass, llvm::Any Ir) {
    std::string PassName = Pass.str();
    std::string IrName = LLVMRustwrappedIrGetName(Ir);
    BeforePassCallback(LlvmSelfProfiler, PassName.c_str(), IrName.c_str());
  });

  PIC.registerAfterAnalysisCallback(
      [LlvmSelfProfiler, AfterPassCallback](StringRef Pass, llvm::Any Ir) {
        AfterPassCallback(LlvmSelfProfiler);
      });
}

enum class LLVMRustOptStage {
  PreLinkNoLTO,
  PreLinkThinLTO,
  PreLinkFatLTO,
  ThinLTO,
  FatLTO,
};

struct LLVMRustSanitizerOptions {
  bool SanitizeAddress;
  bool SanitizeAddressRecover;
  bool SanitizeCFI;
  bool SanitizeKCFI;
  bool SanitizeMemory;
  bool SanitizeMemoryRecover;
  int  SanitizeMemoryTrackOrigins;
  bool SanitizeThread;
  bool SanitizeHWAddress;
  bool SanitizeHWAddressRecover;
  bool SanitizeKernelAddress;
  bool SanitizeKernelAddressRecover;
};

extern "C" LLVMRustResult
LLVMRustOptimize(
    LLVMModuleRef ModuleRef,
    LLVMTargetMachineRef TMRef,
    LLVMRustPassBuilderOptLevel OptLevelRust,
    LLVMRustOptStage OptStage,
    bool IsLinkerPluginLTO,
    bool NoPrepopulatePasses, bool VerifyIR, bool UseThinLTOBuffers,
    bool MergeFunctions, bool UnrollLoops, bool SLPVectorize, bool LoopVectorize,
    bool DisableSimplifyLibCalls, bool EmitLifetimeMarkers,
    LLVMRustSanitizerOptions *SanitizerOptions,
    const char *PGOGenPath, const char *PGOUsePath,
    bool InstrumentCoverage, const char *InstrProfileOutput,
    bool InstrumentGCOV,
    const char *PGOSampleUsePath, bool DebugInfoForProfiling,
    void* LlvmSelfProfiler,
    LLVMRustSelfProfileBeforePassCallback BeforePassCallback,
    LLVMRustSelfProfileAfterPassCallback AfterPassCallback,
    const char *ExtraPasses, size_t ExtraPassesLen,
    const char *LLVMPlugins, size_t LLVMPluginsLen) {
  Module *TheModule = unwrap(ModuleRef);
  TargetMachine *TM = unwrap(TMRef);
  OptimizationLevel OptLevel = fromRust(OptLevelRust);


  PipelineTuningOptions PTO;
  PTO.LoopUnrolling = UnrollLoops;
  PTO.LoopInterleaving = UnrollLoops;
  PTO.LoopVectorization = LoopVectorize;
  PTO.SLPVectorization = SLPVectorize;
  PTO.MergeFunctions = MergeFunctions;

  // FIXME: We may want to expose this as an option.
  bool DebugPassManager = false;

  PassInstrumentationCallbacks PIC;
#if LLVM_VERSION_LT(16, 0)
  StandardInstrumentations SI(DebugPassManager);
#else
  StandardInstrumentations SI(TheModule->getContext(), DebugPassManager);
#endif
  SI.registerCallbacks(PIC);

  if (LlvmSelfProfiler){
    LLVMSelfProfileInitializeCallbacks(PIC,LlvmSelfProfiler,BeforePassCallback,AfterPassCallback);
  }

#if LLVM_VERSION_LT(16, 0)
  Optional<PGOOptions> PGOOpt;
#else
  std::optional<PGOOptions> PGOOpt;
#endif
#if LLVM_VERSION_GE(17, 0)
  auto FS = vfs::getRealFileSystem();
#endif
  if (PGOGenPath) {
    assert(!PGOUsePath && !PGOSampleUsePath);
    PGOOpt = PGOOptions(PGOGenPath, "", "",
#if LLVM_VERSION_GE(17, 0)
                        "",
                        FS,
#endif
                        PGOOptions::IRInstr, PGOOptions::NoCSAction,
                        DebugInfoForProfiling);
  } else if (PGOUsePath) {
    assert(!PGOSampleUsePath);
    PGOOpt = PGOOptions(PGOUsePath, "", "",
#if LLVM_VERSION_GE(17, 0)
                        "",
                        FS,
#endif
                        PGOOptions::IRUse, PGOOptions::NoCSAction,
                        DebugInfoForProfiling);
  } else if (PGOSampleUsePath) {
    PGOOpt = PGOOptions(PGOSampleUsePath, "", "",
#if LLVM_VERSION_GE(17, 0)
                        "",
                        FS,
#endif
                        PGOOptions::SampleUse, PGOOptions::NoCSAction,
                        DebugInfoForProfiling);
  } else if (DebugInfoForProfiling) {
    PGOOpt = PGOOptions("", "", "",
#if LLVM_VERSION_GE(17, 0)
                        "",
                        FS,
#endif
                        PGOOptions::NoAction, PGOOptions::NoCSAction,
                        DebugInfoForProfiling);
  }

  PassBuilder PB(TM, PTO, PGOOpt, &PIC);
  LoopAnalysisManager LAM;
  FunctionAnalysisManager FAM;
  CGSCCAnalysisManager CGAM;
  ModuleAnalysisManager MAM;

  FAM.registerPass([&] { return PB.buildDefaultAAPipeline(); });

  Triple TargetTriple(TheModule->getTargetTriple());
  std::unique_ptr<TargetLibraryInfoImpl> TLII(new TargetLibraryInfoImpl(TargetTriple));
  if (DisableSimplifyLibCalls)
    TLII->disableAllFunctions();
  FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });

  PB.registerModuleAnalyses(MAM);
  PB.registerCGSCCAnalyses(CGAM);
  PB.registerFunctionAnalyses(FAM);
  PB.registerLoopAnalyses(LAM);
  PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);

  // We manually collect pipeline callbacks so we can apply them at O0, where the
  // PassBuilder does not create a pipeline.
  std::vector<std::function<void(ModulePassManager &, OptimizationLevel)>>
      PipelineStartEPCallbacks;
  std::vector<std::function<void(ModulePassManager &, OptimizationLevel)>>
      OptimizerLastEPCallbacks;

  if (!IsLinkerPluginLTO
      && SanitizerOptions && SanitizerOptions->SanitizeCFI
      && !NoPrepopulatePasses) {
    PipelineStartEPCallbacks.push_back(
      [](ModulePassManager &MPM, OptimizationLevel Level) {
        MPM.addPass(LowerTypeTestsPass(/*ExportSummary=*/nullptr,
                                       /*ImportSummary=*/nullptr,
                                       /*DropTypeTests=*/false));
      }
    );
  }

  if (VerifyIR) {
    PipelineStartEPCallbacks.push_back(
      [VerifyIR](ModulePassManager &MPM, OptimizationLevel Level) {
        MPM.addPass(VerifierPass());
      }
    );
  }

  if (InstrumentGCOV) {
    PipelineStartEPCallbacks.push_back(
      [](ModulePassManager &MPM, OptimizationLevel Level) {
        MPM.addPass(GCOVProfilerPass(GCOVOptions::getDefault()));
      }
    );
  }

  if (InstrumentCoverage) {
    PipelineStartEPCallbacks.push_back(
      [InstrProfileOutput](ModulePassManager &MPM, OptimizationLevel Level) {
        InstrProfOptions Options;
        if (InstrProfileOutput) {
          Options.InstrProfileOutput = InstrProfileOutput;
        }
        // cargo run tests in multhreading mode by default
        // so use atomics for coverage counters
        Options.Atomic = true;
        MPM.addPass(InstrProfiling(Options, false));
      }
    );
  }

  if (SanitizerOptions) {
    if (SanitizerOptions->SanitizeMemory) {
      MemorySanitizerOptions Options(
          SanitizerOptions->SanitizeMemoryTrackOrigins,
          SanitizerOptions->SanitizeMemoryRecover,
          /*CompileKernel=*/false,
          /*EagerChecks=*/true);
      OptimizerLastEPCallbacks.push_back(
        [Options](ModulePassManager &MPM, OptimizationLevel Level) {
#if LLVM_VERSION_LT(16, 0)
          MPM.addPass(ModuleMemorySanitizerPass(Options));
          MPM.addPass(createModuleToFunctionPassAdaptor(MemorySanitizerPass(Options)));
#else
          MPM.addPass(MemorySanitizerPass(Options));
#endif
        }
      );
    }

    if (SanitizerOptions->SanitizeThread) {
      OptimizerLastEPCallbacks.push_back(
        [](ModulePassManager &MPM, OptimizationLevel Level) {
          MPM.addPass(ModuleThreadSanitizerPass());
          MPM.addPass(createModuleToFunctionPassAdaptor(ThreadSanitizerPass()));
        }
      );
    }

    if (SanitizerOptions->SanitizeAddress || SanitizerOptions->SanitizeKernelAddress) {
      OptimizerLastEPCallbacks.push_back(
        [SanitizerOptions](ModulePassManager &MPM, OptimizationLevel Level) {
          auto CompileKernel = SanitizerOptions->SanitizeKernelAddress;
          AddressSanitizerOptions opts = AddressSanitizerOptions{
            CompileKernel,
            SanitizerOptions->SanitizeAddressRecover
              || SanitizerOptions->SanitizeKernelAddressRecover,
            /*UseAfterScope=*/true,
            AsanDetectStackUseAfterReturnMode::Runtime,
          };
#if LLVM_VERSION_LT(16, 0)
          MPM.addPass(ModuleAddressSanitizerPass(opts));
#else
          MPM.addPass(AddressSanitizerPass(opts));
#endif
        }
      );
    }
    if (SanitizerOptions->SanitizeHWAddress) {
      OptimizerLastEPCallbacks.push_back(
        [SanitizerOptions](ModulePassManager &MPM, OptimizationLevel Level) {
          HWAddressSanitizerOptions opts(
              /*CompileKernel=*/false, SanitizerOptions->SanitizeHWAddressRecover,
              /*DisableOptimization=*/false);
          MPM.addPass(HWAddressSanitizerPass(opts));
        }
      );
    }
  }

  if (LLVMPluginsLen) {
    auto PluginsStr = StringRef(LLVMPlugins, LLVMPluginsLen);
    SmallVector<StringRef> Plugins;
    PluginsStr.split(Plugins, ',', -1, false);
    for (auto PluginPath: Plugins) {
      auto Plugin = PassPlugin::Load(PluginPath.str());
      if (!Plugin) {
        LLVMRustSetLastError(("Failed to load pass plugin" + PluginPath.str()).c_str());
        return LLVMRustResult::Failure;
      }
      Plugin->registerPassBuilderCallbacks(PB);
    }
  }

  ModulePassManager MPM;
  bool NeedThinLTOBufferPasses = UseThinLTOBuffers;
  if (!NoPrepopulatePasses) {
    // The pre-link pipelines don't support O0 and require using buildO0DefaultPipeline() instead.
    // At the same time, the LTO pipelines do support O0 and using them is required.
    bool IsLTO = OptStage == LLVMRustOptStage::ThinLTO || OptStage == LLVMRustOptStage::FatLTO;
    if (OptLevel == OptimizationLevel::O0 && !IsLTO) {
      for (const auto &C : PipelineStartEPCallbacks)
        PB.registerPipelineStartEPCallback(C);
      for (const auto &C : OptimizerLastEPCallbacks)
        PB.registerOptimizerLastEPCallback(C);

      // Pass false as we manually schedule ThinLTOBufferPasses below.
      MPM = PB.buildO0DefaultPipeline(OptLevel, /* PreLinkLTO */ false);
    } else {
      for (const auto &C : PipelineStartEPCallbacks)
        PB.registerPipelineStartEPCallback(C);
      if (OptStage != LLVMRustOptStage::PreLinkThinLTO) {
        for (const auto &C : OptimizerLastEPCallbacks)
          PB.registerOptimizerLastEPCallback(C);
      }

      switch (OptStage) {
      case LLVMRustOptStage::PreLinkNoLTO:
        MPM = PB.buildPerModuleDefaultPipeline(OptLevel, DebugPassManager);
        break;
      case LLVMRustOptStage::PreLinkThinLTO:
        MPM = PB.buildThinLTOPreLinkDefaultPipeline(OptLevel);
        // The ThinLTOPreLink pipeline already includes ThinLTOBuffer passes. However, callback
        // passes may still run afterwards. This means we need to run the buffer passes again.
        // FIXME: In LLVM 13, the ThinLTOPreLink pipeline also runs OptimizerLastEPCallbacks
        // before the RequiredLTOPreLinkPasses, in which case we can remove these hacks.
        if (OptimizerLastEPCallbacks.empty())
          NeedThinLTOBufferPasses = false;
        for (const auto &C : OptimizerLastEPCallbacks)
          C(MPM, OptLevel);
        break;
      case LLVMRustOptStage::PreLinkFatLTO:
        MPM = PB.buildLTOPreLinkDefaultPipeline(OptLevel);
        NeedThinLTOBufferPasses = false;
        break;
      case LLVMRustOptStage::ThinLTO:
        // FIXME: Does it make sense to pass the ModuleSummaryIndex?
        // It only seems to be needed for C++ specific optimizations.
        MPM = PB.buildThinLTODefaultPipeline(OptLevel, nullptr);
        break;
      case LLVMRustOptStage::FatLTO:
        MPM = PB.buildLTODefaultPipeline(OptLevel, nullptr);
        break;
      }
    }
  } else {
    // We're not building any of the default pipelines but we still want to
    // add the verifier, instrumentation, etc passes if they were requested
    for (const auto &C : PipelineStartEPCallbacks)
      C(MPM, OptLevel);
    for (const auto &C : OptimizerLastEPCallbacks)
      C(MPM, OptLevel);
  }

  if (ExtraPassesLen) {
    if (auto Err = PB.parsePassPipeline(MPM, StringRef(ExtraPasses, ExtraPassesLen))) {
      std::string ErrMsg = toString(std::move(Err));
      LLVMRustSetLastError(ErrMsg.c_str());
      return LLVMRustResult::Failure;
    }
  }

  if (NeedThinLTOBufferPasses) {
    MPM.addPass(CanonicalizeAliasesPass());
    MPM.addPass(NameAnonGlobalPass());
  }

  // Upgrade all calls to old intrinsics first.
  for (Module::iterator I = TheModule->begin(), E = TheModule->end(); I != E;)
    UpgradeCallsToIntrinsic(&*I++); // must be post-increment, as we remove

  MPM.run(*TheModule, MAM);
  return LLVMRustResult::Success;
}

// Callback to demangle function name
// Parameters:
// * name to be demangled
// * name len
// * output buffer
// * output buffer len
// Returns len of demangled string, or 0 if demangle failed.
typedef size_t (*DemangleFn)(const char*, size_t, char*, size_t);


namespace {

class RustAssemblyAnnotationWriter : public AssemblyAnnotationWriter {
  DemangleFn Demangle;
  std::vector<char> Buf;

public:
  RustAssemblyAnnotationWriter(DemangleFn Demangle) : Demangle(Demangle) {}

  // Return empty string if demangle failed
  // or if name does not need to be demangled
  StringRef CallDemangle(StringRef name) {
    if (!Demangle) {
      return StringRef();
    }

    if (Buf.size() < name.size() * 2) {
      // Semangled name usually shorter than mangled,
      // but allocate twice as much memory just in case
      Buf.resize(name.size() * 2);
    }

    auto R = Demangle(name.data(), name.size(), Buf.data(), Buf.size());
    if (!R) {
      // Demangle failed.
      return StringRef();
    }

    auto Demangled = StringRef(Buf.data(), R);
    if (Demangled == name) {
      // Do not print anything if demangled name is equal to mangled.
      return StringRef();
    }

    return Demangled;
  }

  void emitFunctionAnnot(const Function *F,
                         formatted_raw_ostream &OS) override {
    StringRef Demangled = CallDemangle(F->getName());
    if (Demangled.empty()) {
        return;
    }

    OS << "; " << Demangled << "\n";
  }

  void emitInstructionAnnot(const Instruction *I,
                            formatted_raw_ostream &OS) override {
    const char *Name;
    const Value *Value;
    if (const CallInst *CI = dyn_cast<CallInst>(I)) {
      Name = "call";
      Value = CI->getCalledOperand();
    } else if (const InvokeInst* II = dyn_cast<InvokeInst>(I)) {
      Name = "invoke";
      Value = II->getCalledOperand();
    } else {
      // Could demangle more operations, e. g.
      // `store %place, @function`.
      return;
    }

    if (!Value->hasName()) {
      return;
    }

    StringRef Demangled = CallDemangle(Value->getName());
    if (Demangled.empty()) {
      return;
    }

    OS << "; " << Name << " " << Demangled << "\n";
  }
};

} // namespace

extern "C" LLVMRustResult
LLVMRustPrintModule(LLVMModuleRef M, const char *Path, DemangleFn Demangle) {
  std::string ErrorInfo;
  std::error_code EC;
  raw_fd_ostream OS(Path, EC, sys::fs::OF_None);
  if (EC)
    ErrorInfo = EC.message();
  if (ErrorInfo != "") {
    LLVMRustSetLastError(ErrorInfo.c_str());
    return LLVMRustResult::Failure;
  }

  RustAssemblyAnnotationWriter AAW(Demangle);
  formatted_raw_ostream FOS(OS);
  unwrap(M)->print(FOS, &AAW);

  return LLVMRustResult::Success;
}

extern "C" void LLVMRustPrintPasses() {
  PassBuilder PB;
  PB.printPassNames(outs());
}

extern "C" void LLVMRustRunRestrictionPass(LLVMModuleRef M, char **Symbols,
                                           size_t Len) {
  auto PreserveFunctions = [=](const GlobalValue &GV) {
    for (size_t I = 0; I < Len; I++) {
      if (GV.getName() == Symbols[I]) {
        return true;
      }
    }
    return false;
  };

  internalizeModule(*unwrap(M), PreserveFunctions);
}

extern "C" void
LLVMRustSetDataLayoutFromTargetMachine(LLVMModuleRef Module,
                                       LLVMTargetMachineRef TMR) {
  TargetMachine *Target = unwrap(TMR);
  unwrap(Module)->setDataLayout(Target->createDataLayout());
}

extern "C" void LLVMRustSetModulePICLevel(LLVMModuleRef M) {
  unwrap(M)->setPICLevel(PICLevel::Level::BigPIC);
}

extern "C" void LLVMRustSetModulePIELevel(LLVMModuleRef M) {
  unwrap(M)->setPIELevel(PIELevel::Level::Large);
}

extern "C" void LLVMRustSetModuleCodeModel(LLVMModuleRef M,
                                           LLVMRustCodeModel Model) {
  auto CM = fromRust(Model);
  if (!CM)
    return;
  unwrap(M)->setCodeModel(*CM);
}

// Here you'll find an implementation of ThinLTO as used by the Rust compiler
// right now. This ThinLTO support is only enabled on "recent ish" versions of
// LLVM, and otherwise it's just blanket rejected from other compilers.
//
// Most of this implementation is straight copied from LLVM. At the time of
// this writing it wasn't *quite* suitable to reuse more code from upstream
// for our purposes, but we should strive to upstream this support once it's
// ready to go! I figure we may want a bit of testing locally first before
// sending this upstream to LLVM. I hear though they're quite eager to receive
// feedback like this!
//
// If you're reading this code and wondering "what in the world" or you're
// working "good lord by LLVM upgrade is *still* failing due to these bindings"
// then fear not! (ok maybe fear a little). All code here is mostly based
// on `lib/LTO/ThinLTOCodeGenerator.cpp` in LLVM.
//
// You'll find that the general layout here roughly corresponds to the `run`
// method in that file as well as `ProcessThinLTOModule`. Functions are
// specifically commented below as well, but if you're updating this code
// or otherwise trying to understand it, the LLVM source will be useful in
// interpreting the mysteries within.
//
// Otherwise I'll apologize in advance, it probably requires a relatively
// significant investment on your part to "truly understand" what's going on
// here. Not saying I do myself, but it took me awhile staring at LLVM's source
// and various online resources about ThinLTO to make heads or tails of all
// this.

// This is a shared data structure which *must* be threadsafe to share
// read-only amongst threads. This also corresponds basically to the arguments
// of the `ProcessThinLTOModule` function in the LLVM source.
struct LLVMRustThinLTOData {
  // The combined index that is the global analysis over all modules we're
  // performing ThinLTO for. This is mostly managed by LLVM.
  ModuleSummaryIndex Index;

  // All modules we may look at, stored as in-memory serialized versions. This
  // is later used when inlining to ensure we can extract any module to inline
  // from.
  StringMap<MemoryBufferRef> ModuleMap;

  // A set that we manage of everything we *don't* want internalized. Note that
  // this includes all transitive references right now as well, but it may not
  // always!
  DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;

  // Not 100% sure what these are, but they impact what's internalized and
  // what's inlined across modules, I believe.
#if LLVM_VERSION_GE(18, 0)
  DenseMap<StringRef, FunctionImporter::ImportMapTy> ImportLists;
  DenseMap<StringRef, FunctionImporter::ExportSetTy> ExportLists;
  DenseMap<StringRef, GVSummaryMapTy> ModuleToDefinedGVSummaries;
#else
  StringMap<FunctionImporter::ImportMapTy> ImportLists;
  StringMap<FunctionImporter::ExportSetTy> ExportLists;
  StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries;
#endif
  StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;

  LLVMRustThinLTOData() : Index(/* HaveGVs = */ false) {}
};

// Just an argument to the `LLVMRustCreateThinLTOData` function below.
struct LLVMRustThinLTOModule {
  const char *identifier;
  const char *data;
  size_t len;
};

// This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp`, not sure what it
// does.
static const GlobalValueSummary *
getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) {
  auto StrongDefForLinker = llvm::find_if(
      GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
        auto Linkage = Summary->linkage();
        return !GlobalValue::isAvailableExternallyLinkage(Linkage) &&
               !GlobalValue::isWeakForLinker(Linkage);
      });
  if (StrongDefForLinker != GVSummaryList.end())
    return StrongDefForLinker->get();

  auto FirstDefForLinker = llvm::find_if(
      GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
        auto Linkage = Summary->linkage();
        return !GlobalValue::isAvailableExternallyLinkage(Linkage);
      });
  if (FirstDefForLinker == GVSummaryList.end())
    return nullptr;
  return FirstDefForLinker->get();
}

// The main entry point for creating the global ThinLTO analysis. The structure
// here is basically the same as before threads are spawned in the `run`
// function of `lib/LTO/ThinLTOCodeGenerator.cpp`.
extern "C" LLVMRustThinLTOData*
LLVMRustCreateThinLTOData(LLVMRustThinLTOModule *modules,
                          int num_modules,
                          const char **preserved_symbols,
                          int num_symbols) {
  auto Ret = std::make_unique<LLVMRustThinLTOData>();

  // Load each module's summary and merge it into one combined index
  for (int i = 0; i < num_modules; i++) {
    auto module = &modules[i];
    StringRef buffer(module->data, module->len);
    MemoryBufferRef mem_buffer(buffer, module->identifier);

    Ret->ModuleMap[module->identifier] = mem_buffer;

    if (Error Err = readModuleSummaryIndex(mem_buffer, Ret->Index, i)) {
      LLVMRustSetLastError(toString(std::move(Err)).c_str());
      return nullptr;
    }
  }

  // Collect for each module the list of function it defines (GUID -> Summary)
  Ret->Index.collectDefinedGVSummariesPerModule(Ret->ModuleToDefinedGVSummaries);

  // Convert the preserved symbols set from string to GUID, this is then needed
  // for internalization.
  for (int i = 0; i < num_symbols; i++) {
    auto GUID = GlobalValue::getGUID(preserved_symbols[i]);
    Ret->GUIDPreservedSymbols.insert(GUID);
  }

  // Collect the import/export lists for all modules from the call-graph in the
  // combined index
  //
  // This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp`
  auto deadIsPrevailing = [&](GlobalValue::GUID G) {
    return PrevailingType::Unknown;
  };
  // We don't have a complete picture in our use of ThinLTO, just our immediate
  // crate, so we need `ImportEnabled = false` to limit internalization.
  // Otherwise, we sometimes lose `static` values -- see #60184.
  computeDeadSymbolsWithConstProp(Ret->Index, Ret->GUIDPreservedSymbols,
                                  deadIsPrevailing, /* ImportEnabled = */ false);
  // Resolve LinkOnce/Weak symbols, this has to be computed early be cause it
  // impacts the caching.
  //
  // This is copied from `lib/LTO/ThinLTOCodeGenerator.cpp` with some of this
  // being lifted from `lib/LTO/LTO.cpp` as well
  DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
  for (auto &I : Ret->Index) {
    if (I.second.SummaryList.size() > 1)
      PrevailingCopy[I.first] = getFirstDefinitionForLinker(I.second.SummaryList);
  }
  auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
    const auto &Prevailing = PrevailingCopy.find(GUID);
    if (Prevailing == PrevailingCopy.end())
      return true;
    return Prevailing->second == S;
  };
  ComputeCrossModuleImport(
    Ret->Index,
    Ret->ModuleToDefinedGVSummaries,
#if LLVM_VERSION_GE(17, 0)
    isPrevailing,
#endif
    Ret->ImportLists,
    Ret->ExportLists
  );

  auto recordNewLinkage = [&](StringRef ModuleIdentifier,
                              GlobalValue::GUID GUID,
                              GlobalValue::LinkageTypes NewLinkage) {
    Ret->ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
  };

  // Uses FromPrevailing visibility scheme which works for many binary
  // formats. We probably could and should use ELF visibility scheme for many of
  // our targets, however.
  lto::Config conf;
  thinLTOResolvePrevailingInIndex(conf, Ret->Index, isPrevailing, recordNewLinkage,
                                  Ret->GUIDPreservedSymbols);

  // Here we calculate an `ExportedGUIDs` set for use in the `isExported`
  // callback below. This callback below will dictate the linkage for all
  // summaries in the index, and we basically just only want to ensure that dead
  // symbols are internalized. Otherwise everything that's already external
  // linkage will stay as external, and internal will stay as internal.
  std::set<GlobalValue::GUID> ExportedGUIDs;
  for (auto &List : Ret->Index) {
    for (auto &GVS: List.second.SummaryList) {
      if (GlobalValue::isLocalLinkage(GVS->linkage()))
        continue;
      auto GUID = GVS->getOriginalName();
      if (GVS->flags().Live)
        ExportedGUIDs.insert(GUID);
    }
  }
  auto isExported = [&](StringRef ModuleIdentifier, ValueInfo VI) {
    const auto &ExportList = Ret->ExportLists.find(ModuleIdentifier);
    return (ExportList != Ret->ExportLists.end() &&
      ExportList->second.count(VI)) ||
      ExportedGUIDs.count(VI.getGUID());
  };
  thinLTOInternalizeAndPromoteInIndex(Ret->Index, isExported, isPrevailing);

  return Ret.release();
}

extern "C" void
LLVMRustFreeThinLTOData(LLVMRustThinLTOData *Data) {
  delete Data;
}

// Below are the various passes that happen *per module* when doing ThinLTO.
//
// In other words, these are the functions that are all run concurrently
// with one another, one per module. The passes here correspond to the analysis
// passes in `lib/LTO/ThinLTOCodeGenerator.cpp`, currently found in the
// `ProcessThinLTOModule` function. Here they're split up into separate steps
// so rustc can save off the intermediate bytecode between each step.

static bool
clearDSOLocalOnDeclarations(Module &Mod, TargetMachine &TM) {
  // When linking an ELF shared object, dso_local should be dropped. We
  // conservatively do this for -fpic.
  bool ClearDSOLocalOnDeclarations =
      TM.getTargetTriple().isOSBinFormatELF() &&
      TM.getRelocationModel() != Reloc::Static &&
      Mod.getPIELevel() == PIELevel::Default;
  return ClearDSOLocalOnDeclarations;
}

extern "C" bool
LLVMRustPrepareThinLTORename(const LLVMRustThinLTOData *Data, LLVMModuleRef M,
                             LLVMTargetMachineRef TM) {
  Module &Mod = *unwrap(M);
  TargetMachine &Target = *unwrap(TM);

  bool ClearDSOLocal = clearDSOLocalOnDeclarations(Mod, Target);
  bool error = renameModuleForThinLTO(Mod, Data->Index, ClearDSOLocal);

  if (error) {
    LLVMRustSetLastError("renameModuleForThinLTO failed");
    return false;
  }
  return true;
}

extern "C" bool
LLVMRustPrepareThinLTOResolveWeak(const LLVMRustThinLTOData *Data, LLVMModuleRef M) {
  Module &Mod = *unwrap(M);
  const auto &DefinedGlobals = Data->ModuleToDefinedGVSummaries.lookup(Mod.getModuleIdentifier());
  thinLTOFinalizeInModule(Mod, DefinedGlobals, /*PropagateAttrs=*/true);
  return true;
}

extern "C" bool
LLVMRustPrepareThinLTOInternalize(const LLVMRustThinLTOData *Data, LLVMModuleRef M) {
  Module &Mod = *unwrap(M);
  const auto &DefinedGlobals = Data->ModuleToDefinedGVSummaries.lookup(Mod.getModuleIdentifier());
  thinLTOInternalizeModule(Mod, DefinedGlobals);
  return true;
}

extern "C" bool
LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data, LLVMModuleRef M,
                             LLVMTargetMachineRef TM) {
  Module &Mod = *unwrap(M);
  TargetMachine &Target = *unwrap(TM);

  const auto &ImportList = Data->ImportLists.lookup(Mod.getModuleIdentifier());
  auto Loader = [&](StringRef Identifier) {
    const auto &Memory = Data->ModuleMap.lookup(Identifier);
    auto &Context = Mod.getContext();
    auto MOrErr = getLazyBitcodeModule(Memory, Context, true, true);

    if (!MOrErr)
      return MOrErr;

    // The rest of this closure is a workaround for
    // https://bugs.llvm.org/show_bug.cgi?id=38184 where during ThinLTO imports
    // we accidentally import wasm custom sections into different modules,
    // duplicating them by in the final output artifact.
    //
    // The issue is worked around here by manually removing the
    // `wasm.custom_sections` named metadata node from any imported module. This
    // we know isn't used by any optimization pass so there's no need for it to
    // be imported.
    //
    // Note that the metadata is currently lazily loaded, so we materialize it
    // here before looking up if there's metadata inside. The `FunctionImporter`
    // will immediately materialize metadata anyway after an import, so this
    // shouldn't be a perf hit.
    if (Error Err = (*MOrErr)->materializeMetadata()) {
      Expected<std::unique_ptr<Module>> Ret(std::move(Err));
      return Ret;
    }

    auto *WasmCustomSections = (*MOrErr)->getNamedMetadata("wasm.custom_sections");
    if (WasmCustomSections)
      WasmCustomSections->eraseFromParent();

    // `llvm.ident` named metadata also gets duplicated.
    auto *llvmIdent = (*MOrErr)->getNamedMetadata("llvm.ident");
    if (llvmIdent)
      llvmIdent->eraseFromParent();

    return MOrErr;
  };
  bool ClearDSOLocal = clearDSOLocalOnDeclarations(Mod, Target);
  FunctionImporter Importer(Data->Index, Loader, ClearDSOLocal);
  Expected<bool> Result = Importer.importFunctions(Mod, ImportList);
  if (!Result) {
    LLVMRustSetLastError(toString(Result.takeError()).c_str());
    return false;
  }
  return true;
}

// This struct and various functions are sort of a hack right now, but the
// problem is that we've got in-memory LLVM modules after we generate and
// optimize all codegen-units for one compilation in rustc. To be compatible
// with the LTO support above we need to serialize the modules plus their
// ThinLTO summary into memory.
//
// This structure is basically an owned version of a serialize module, with
// a ThinLTO summary attached.
struct LLVMRustThinLTOBuffer {
  std::string data;
};

extern "C" LLVMRustThinLTOBuffer*
LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin) {
  auto Ret = std::make_unique<LLVMRustThinLTOBuffer>();
  {
    raw_string_ostream OS(Ret->data);
    {
      if (is_thin) {
        PassBuilder PB;
        LoopAnalysisManager LAM;
        FunctionAnalysisManager FAM;
        CGSCCAnalysisManager CGAM;
        ModuleAnalysisManager MAM;
        PB.registerModuleAnalyses(MAM);
        PB.registerCGSCCAnalyses(CGAM);
        PB.registerFunctionAnalyses(FAM);
        PB.registerLoopAnalyses(LAM);
        PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
        ModulePassManager MPM;
        MPM.addPass(ThinLTOBitcodeWriterPass(OS, nullptr));
        MPM.run(*unwrap(M), MAM);
      } else {
        WriteBitcodeToFile(*unwrap(M), OS);
      }
    }
  }
  return Ret.release();
}

extern "C" void
LLVMRustThinLTOBufferFree(LLVMRustThinLTOBuffer *Buffer) {
  delete Buffer;
}

extern "C" const void*
LLVMRustThinLTOBufferPtr(const LLVMRustThinLTOBuffer *Buffer) {
  return Buffer->data.data();
}

extern "C" size_t
LLVMRustThinLTOBufferLen(const LLVMRustThinLTOBuffer *Buffer) {
  return Buffer->data.length();
}

// This is what we used to parse upstream bitcode for actual ThinLTO
// processing. We'll call this once per module optimized through ThinLTO, and
// it'll be called concurrently on many threads.
extern "C" LLVMModuleRef
LLVMRustParseBitcodeForLTO(LLVMContextRef Context,
                           const char *data,
                           size_t len,
                           const char *identifier) {
  StringRef Data(data, len);
  MemoryBufferRef Buffer(Data, identifier);
  unwrap(Context)->enableDebugTypeODRUniquing();
  Expected<std::unique_ptr<Module>> SrcOrError =
      parseBitcodeFile(Buffer, *unwrap(Context));
  if (!SrcOrError) {
    LLVMRustSetLastError(toString(SrcOrError.takeError()).c_str());
    return nullptr;
  }
  return wrap(std::move(*SrcOrError).release());
}

// Find the bitcode section in the object file data and return it as a slice.
// Fail if the bitcode section is present but empty.
//
// On success, the return value is the pointer to the start of the slice and
// `out_len` is filled with the (non-zero) length. On failure, the return value
// is `nullptr` and `out_len` is set to zero.
extern "C" const char*
LLVMRustGetBitcodeSliceFromObjectData(const char *data,
                                      size_t len,
                                      size_t *out_len) {
  *out_len = 0;

  StringRef Data(data, len);
  MemoryBufferRef Buffer(Data, ""); // The id is unused.

  Expected<MemoryBufferRef> BitcodeOrError =
    object::IRObjectFile::findBitcodeInMemBuffer(Buffer);
  if (!BitcodeOrError) {
    LLVMRustSetLastError(toString(BitcodeOrError.takeError()).c_str());
    return nullptr;
  }

  *out_len = BitcodeOrError->getBufferSize();
  return BitcodeOrError->getBufferStart();
}

// Computes the LTO cache key for the provided 'ModId' in the given 'Data',
// storing the result in 'KeyOut'.
// Currently, this cache key is a SHA-1 hash of anything that could affect
// the result of optimizing this module (e.g. module imports, exports, liveness
// of access globals, etc).
// The precise details are determined by LLVM in `computeLTOCacheKey`, which is
// used during the normal linker-plugin incremental thin-LTO process.
extern "C" void
LLVMRustComputeLTOCacheKey(RustStringRef KeyOut, const char *ModId, LLVMRustThinLTOData *Data) {
  SmallString<40> Key;
  llvm::lto::Config conf;
  const auto &ImportList = Data->ImportLists.lookup(ModId);
  const auto &ExportList = Data->ExportLists.lookup(ModId);
  const auto &ResolvedODR = Data->ResolvedODR.lookup(ModId);
  const auto &DefinedGlobals = Data->ModuleToDefinedGVSummaries.lookup(ModId);
  std::set<GlobalValue::GUID> CfiFunctionDefs;
  std::set<GlobalValue::GUID> CfiFunctionDecls;

  // Based on the 'InProcessThinBackend' constructor in LLVM
  for (auto &Name : Data->Index.cfiFunctionDefs())
    CfiFunctionDefs.insert(
        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
  for (auto &Name : Data->Index.cfiFunctionDecls())
    CfiFunctionDecls.insert(
        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));

  llvm::computeLTOCacheKey(Key, conf, Data->Index, ModId,
      ImportList, ExportList, ResolvedODR, DefinedGlobals, CfiFunctionDefs, CfiFunctionDecls
  );

  LLVMRustStringWriteImpl(KeyOut, Key.c_str(), Key.size());
}