Imported Upstream version 5.18.0.225

Former-commit-id: 10196d987d5fc5564b9d3b33b1fdf13190f4d0b5

external/llvm/lib/LTO/CMakeLists.txt

@@ -0,0 +1,16 @@
+add_llvm_library(LLVMLTO
+  Caching.cpp
+  LTO.cpp
+  LTOBackend.cpp
+  LTOModule.cpp
+  LTOCodeGenerator.cpp
+  UpdateCompilerUsed.cpp
+  ThinLTOCodeGenerator.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/LTO
+
+  DEPENDS
+  intrinsics_gen
+  llvm_vcsrevision_h
+)

external/llvm/lib/LTO/Caching.cpp

@@ -0,0 +1,127 @@
+//===-Caching.cpp - LLVM Link Time Optimizer Cache Handling ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Caching for ThinLTO.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/Caching.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/Process.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+using namespace llvm::lto;
+
+Expected<NativeObjectCache> lto::localCache(StringRef CacheDirectoryPath,
+                                            AddBufferFn AddBuffer) {
+  if (std::error_code EC = sys::fs::create_directories(CacheDirectoryPath))
+    return errorCodeToError(EC);
+
+  return [=](unsigned Task, StringRef Key) -> AddStreamFn {
+    // This choice of file name allows the cache to be pruned (see pruneCache()
+    // in include/llvm/Support/CachePruning.h).
+    SmallString<64> EntryPath;
+    sys::path::append(EntryPath, CacheDirectoryPath, "llvmcache-" + Key);
+    // First, see if we have a cache hit.
+    ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
+        MemoryBuffer::getFile(EntryPath);
+    if (MBOrErr) {
+      AddBuffer(Task, std::move(*MBOrErr), EntryPath);
+      return AddStreamFn();
+    }
+
+    if (MBOrErr.getError() != errc::no_such_file_or_directory)
+      report_fatal_error(Twine("Failed to open cache file ") + EntryPath +
+                         ": " + MBOrErr.getError().message() + "\n");
+
+    // This native object stream is responsible for commiting the resulting
+    // file to the cache and calling AddBuffer to add it to the link.
+    struct CacheStream : NativeObjectStream {
+      AddBufferFn AddBuffer;
+      sys::fs::TempFile TempFile;
+      std::string EntryPath;
+      unsigned Task;
+
+      CacheStream(std::unique_ptr<raw_pwrite_stream> OS, AddBufferFn AddBuffer,
+                  sys::fs::TempFile TempFile, std::string EntryPath,
+                  unsigned Task)
+          : NativeObjectStream(std::move(OS)), AddBuffer(std::move(AddBuffer)),
+            TempFile(std::move(TempFile)), EntryPath(std::move(EntryPath)),
+            Task(Task) {}
+
+      ~CacheStream() {
+        // Make sure the stream is closed before committing it.
+        OS.reset();
+
+        // Open the file first to avoid racing with a cache pruner.
+        ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr =
+            MemoryBuffer::getOpenFile(TempFile.FD, TempFile.TmpName,
+                                      /*FileSize*/ -1,
+                                      /*RequiresNullTerminator*/ false);
+        if (!MBOrErr)
+          report_fatal_error(Twine("Failed to open new cache file ") +
+                             TempFile.TmpName + ": " +
+                             MBOrErr.getError().message() + "\n");
+
+        // On POSIX systems, this will atomically replace the destination if
+        // it already exists. We try to emulate this on Windows, but this may
+        // fail with a permission denied error (for example, if the destination
+        // is currently opened by another process that does not give us the
+        // sharing permissions we need). Since the existing file should be
+        // semantically equivalent to the one we are trying to write, we give
+        // AddBuffer a copy of the bytes we wrote in that case. We do this
+        // instead of just using the existing file, because the pruner might
+        // delete the file before we get a chance to use it.
+        Error E = TempFile.keep(EntryPath);
+        E = handleErrors(std::move(E), [&](const ECError &E) -> Error {
+          std::error_code EC = E.convertToErrorCode();
+          if (EC != errc::permission_denied)
+            return errorCodeToError(EC);
+
+          auto MBCopy = MemoryBuffer::getMemBufferCopy((*MBOrErr)->getBuffer(),
+                                                       EntryPath);
+          MBOrErr = std::move(MBCopy);
+
+          // FIXME: should we consume the discard error?
+          consumeError(TempFile.discard());
+
+          return Error::success();
+        });
+
+        if (E)
+          report_fatal_error(Twine("Failed to rename temporary file ") +
+                             TempFile.TmpName + " to " + EntryPath + ": " +
+                             toString(std::move(E)) + "\n");
+
+        AddBuffer(Task, std::move(*MBOrErr), EntryPath);
+      }
+    };
+
+    return [=](size_t Task) -> std::unique_ptr<NativeObjectStream> {
+      // Write to a temporary to avoid race condition
+      SmallString<64> TempFilenameModel;
+      sys::path::append(TempFilenameModel, CacheDirectoryPath, "Thin-%%%%%%.tmp.o");
+      Expected<sys::fs::TempFile> Temp = sys::fs::TempFile::create(
+          TempFilenameModel, sys::fs::owner_read | sys::fs::owner_write);
+      if (!Temp) {
+        errs() << "Error: " << toString(Temp.takeError()) << "\n";
+        report_fatal_error("ThinLTO: Can't get a temporary file");
+      }
+
+      // This CacheStream will move the temporary file into the cache when done.
+      return llvm::make_unique<CacheStream>(
+          llvm::make_unique<raw_fd_ostream>(Temp->FD, /* ShouldClose */ false),
+          AddBuffer, std::move(*Temp), EntryPath.str(), Task);
+    };
+  };
+}

external/llvm/lib/LTO/LLVMBuild.txt

@@ -0,0 +1,38 @@
+;===- ./lib/LTO/LLVMBuild.txt ----------------------------------*- Conf -*--===;
+;
+;                     The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+;   http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = LTO
+parent = Libraries
+required_libraries =
+ Analysis
+ BitReader
+ BitWriter
+ CodeGen
+ Core
+ IPO
+ InstCombine
+ Linker
+ MC
+ ObjCARC
+ Object
+ Passes
+ Scalar
+ Support
+ Target
+ TransformUtils

external/llvm/lib/LTO/LTOBackend.cpp

@@ -0,0 +1,452 @@
+//===-LTOBackend.cpp - LLVM Link Time Optimizer Backend -------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the "backend" phase of LTO, i.e. it performs
+// optimization and code generation on a loaded module. It is generally used
+// internally by the LTO class but can also be used independently, for example
+// to implement a standalone ThinLTO backend.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/LTOBackend.h"
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/CGSCCPassManager.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Bitcode/BitcodeReader.h"
+#include "llvm/Bitcode/BitcodeWriter.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/LTO/LTO.h"
+#include "llvm/MC/SubtargetFeature.h"
+#include "llvm/Object/ModuleSymbolTable.h"
+#include "llvm/Passes/PassBuilder.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Transforms/IPO/PassManagerBuilder.h"
+#include "llvm/Transforms/Scalar/LoopPassManager.h"
+#include "llvm/Transforms/Utils/FunctionImportUtils.h"
+#include "llvm/Transforms/Utils/SplitModule.h"
+
+using namespace llvm;
+using namespace lto;
+
+LLVM_ATTRIBUTE_NORETURN static void reportOpenError(StringRef Path, Twine Msg) {
+  errs() << "failed to open " << Path << ": " << Msg << '\n';
+  errs().flush();
+  exit(1);
+}
+
+Error Config::addSaveTemps(std::string OutputFileName,
+                           bool UseInputModulePath) {
+  ShouldDiscardValueNames = false;
+
+  std::error_code EC;
+  ResolutionFile = llvm::make_unique<raw_fd_ostream>(
+      OutputFileName + "resolution.txt", EC, sys::fs::OpenFlags::F_Text);
+  if (EC)
+    return errorCodeToError(EC);
+
+  auto setHook = [&](std::string PathSuffix, ModuleHookFn &Hook) {
+    // Keep track of the hook provided by the linker, which also needs to run.
+    ModuleHookFn LinkerHook = Hook;
+    Hook = [=](unsigned Task, const Module &M) {
+      // If the linker's hook returned false, we need to pass that result
+      // through.
+      if (LinkerHook && !LinkerHook(Task, M))
+        return false;
+
+      std::string PathPrefix;
+      // If this is the combined module (not a ThinLTO backend compile) or the
+      // user hasn't requested using the input module's path, emit to a file
+      // named from the provided OutputFileName with the Task ID appended.
+      if (M.getModuleIdentifier() == "ld-temp.o" || !UseInputModulePath) {
+        PathPrefix = OutputFileName + utostr(Task);
+      } else
+        PathPrefix = M.getModuleIdentifier();
+      std::string Path = PathPrefix + "." + PathSuffix + ".bc";
+      std::error_code EC;
+      raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
+      // Because -save-temps is a debugging feature, we report the error
+      // directly and exit.
+      if (EC)
+        reportOpenError(Path, EC.message());
+      WriteBitcodeToFile(&M, OS, /*ShouldPreserveUseListOrder=*/false);
+      return true;
+    };
+  };
+
+  setHook("0.preopt", PreOptModuleHook);
+  setHook("1.promote", PostPromoteModuleHook);
+  setHook("2.internalize", PostInternalizeModuleHook);
+  setHook("3.import", PostImportModuleHook);
+  setHook("4.opt", PostOptModuleHook);
+  setHook("5.precodegen", PreCodeGenModuleHook);
+
+  CombinedIndexHook = [=](const ModuleSummaryIndex &Index) {
+    std::string Path = OutputFileName + "index.bc";
+    std::error_code EC;
+    raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
+    // Because -save-temps is a debugging feature, we report the error
+    // directly and exit.
+    if (EC)
+      reportOpenError(Path, EC.message());
+    WriteIndexToFile(Index, OS);
+    return true;
+  };
+
+  return Error::success();
+}
+
+namespace {
+
+std::unique_ptr<TargetMachine>
+createTargetMachine(Config &Conf, const Target *TheTarget, Module &M) {
+  StringRef TheTriple = M.getTargetTriple();
+  SubtargetFeatures Features;
+  Features.getDefaultSubtargetFeatures(Triple(TheTriple));
+  for (const std::string &A : Conf.MAttrs)
+    Features.AddFeature(A);
+
+  Reloc::Model RelocModel;
+  if (Conf.RelocModel)
+    RelocModel = *Conf.RelocModel;
+  else
+    RelocModel =
+        M.getPICLevel() == PICLevel::NotPIC ? Reloc::Static : Reloc::PIC_;
+
+  return std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
+      TheTriple, Conf.CPU, Features.getString(), Conf.Options, RelocModel,
+      Conf.CodeModel, Conf.CGOptLevel));
+}
+
+static void runNewPMPasses(Config &Conf, Module &Mod, TargetMachine *TM,
+                           unsigned OptLevel, bool IsThinLTO) {
+  Optional<PGOOptions> PGOOpt;
+  if (!Conf.SampleProfile.empty())
+    PGOOpt = PGOOptions("", "", Conf.SampleProfile, false, true);
+
+  PassBuilder PB(TM, PGOOpt);
+  AAManager AA;
+
+  // Parse a custom AA pipeline if asked to.
+  if (!PB.parseAAPipeline(AA, "default"))
+    report_fatal_error("Error parsing default AA pipeline");
+
+  LoopAnalysisManager LAM(Conf.DebugPassManager);
+  FunctionAnalysisManager FAM(Conf.DebugPassManager);
+  CGSCCAnalysisManager CGAM(Conf.DebugPassManager);
+  ModuleAnalysisManager MAM(Conf.DebugPassManager);
+
+  // Register the AA manager first so that our version is the one used.
+  FAM.registerPass([&] { return std::move(AA); });
+
+  // Register all the basic analyses with the managers.
+  PB.registerModuleAnalyses(MAM);
+  PB.registerCGSCCAnalyses(CGAM);
+  PB.registerFunctionAnalyses(FAM);
+  PB.registerLoopAnalyses(LAM);
+  PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
+
+  ModulePassManager MPM(Conf.DebugPassManager);
+  // FIXME (davide): verify the input.
+
+  PassBuilder::OptimizationLevel OL;
+
+  switch (OptLevel) {
+  default:
+    llvm_unreachable("Invalid optimization level");
+  case 0:
+    OL = PassBuilder::O0;
+    break;
+  case 1:
+    OL = PassBuilder::O1;
+    break;
+  case 2:
+    OL = PassBuilder::O2;
+    break;
+  case 3:
+    OL = PassBuilder::O3;
+    break;
+  }
+
+  if (IsThinLTO)
+    MPM = PB.buildThinLTODefaultPipeline(OL, Conf.DebugPassManager);
+  else
+    MPM = PB.buildLTODefaultPipeline(OL, Conf.DebugPassManager);
+  MPM.run(Mod, MAM);
+
+  // FIXME (davide): verify the output.
+}
+
+static void runNewPMCustomPasses(Module &Mod, TargetMachine *TM,
+                                 std::string PipelineDesc,
+                                 std::string AAPipelineDesc,
+                                 bool DisableVerify) {
+  PassBuilder PB(TM);
+  AAManager AA;
+
+  // Parse a custom AA pipeline if asked to.
+  if (!AAPipelineDesc.empty())
+    if (!PB.parseAAPipeline(AA, AAPipelineDesc))
+      report_fatal_error("unable to parse AA pipeline description: " +
+                         AAPipelineDesc);
+
+  LoopAnalysisManager LAM;
+  FunctionAnalysisManager FAM;
+  CGSCCAnalysisManager CGAM;
+  ModuleAnalysisManager MAM;
+
+  // Register the AA manager first so that our version is the one used.
+  FAM.registerPass([&] { return std::move(AA); });
+
+  // Register all the basic analyses with the managers.
+  PB.registerModuleAnalyses(MAM);
+  PB.registerCGSCCAnalyses(CGAM);
+  PB.registerFunctionAnalyses(FAM);
+  PB.registerLoopAnalyses(LAM);
+  PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
+
+  ModulePassManager MPM;
+
+  // Always verify the input.
+  MPM.addPass(VerifierPass());
+
+  // Now, add all the passes we've been requested to.
+  if (!PB.parsePassPipeline(MPM, PipelineDesc))
+    report_fatal_error("unable to parse pass pipeline description: " +
+                       PipelineDesc);
+
+  if (!DisableVerify)
+    MPM.addPass(VerifierPass());
+  MPM.run(Mod, MAM);
+}
+
+static void runOldPMPasses(Config &Conf, Module &Mod, TargetMachine *TM,
+                           bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+                           const ModuleSummaryIndex *ImportSummary) {
+  legacy::PassManager passes;
+  passes.add(createTargetTransformInfoWrapperPass(TM->getTargetIRAnalysis()));
+
+  PassManagerBuilder PMB;
+  PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM->getTargetTriple()));
+  PMB.Inliner = createFunctionInliningPass();
+  PMB.ExportSummary = ExportSummary;
+  PMB.ImportSummary = ImportSummary;
+  // Unconditionally verify input since it is not verified before this
+  // point and has unknown origin.
+  PMB.VerifyInput = true;
+  PMB.VerifyOutput = !Conf.DisableVerify;
+  PMB.LoopVectorize = true;
+  PMB.SLPVectorize = true;
+  PMB.OptLevel = Conf.OptLevel;
+  PMB.PGOSampleUse = Conf.SampleProfile;
+  if (IsThinLTO)
+    PMB.populateThinLTOPassManager(passes);
+  else
+    PMB.populateLTOPassManager(passes);
+  passes.run(Mod);
+}
+
+bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
+         bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
+         const ModuleSummaryIndex *ImportSummary) {
+  // FIXME: Plumb the combined index into the new pass manager.
+  if (!Conf.OptPipeline.empty())
+    runNewPMCustomPasses(Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
+                         Conf.DisableVerify);
+  else if (Conf.UseNewPM)
+    runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO);
+  else
+    runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
+  return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
+}
+
+void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
+             unsigned Task, Module &Mod) {
+  if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
+    return;
+
+  auto Stream = AddStream(Task);
+  legacy::PassManager CodeGenPasses;
+  if (TM->addPassesToEmitFile(CodeGenPasses, *Stream->OS, Conf.CGFileType))
+    report_fatal_error("Failed to setup codegen");
+  CodeGenPasses.run(Mod);
+}
+
+void splitCodeGen(Config &C, TargetMachine *TM, AddStreamFn AddStream,
+                  unsigned ParallelCodeGenParallelismLevel,
+                  std::unique_ptr<Module> Mod) {
+  ThreadPool CodegenThreadPool(ParallelCodeGenParallelismLevel);
+  unsigned ThreadCount = 0;
+  const Target *T = &TM->getTarget();
+
+  SplitModule(
+      std::move(Mod), ParallelCodeGenParallelismLevel,
+      [&](std::unique_ptr<Module> MPart) {
+        // We want to clone the module in a new context to multi-thread the
+        // codegen. We do it by serializing partition modules to bitcode
+        // (while still on the main thread, in order to avoid data races) and
+        // spinning up new threads which deserialize the partitions into
+        // separate contexts.
+        // FIXME: Provide a more direct way to do this in LLVM.
+        SmallString<0> BC;
+        raw_svector_ostream BCOS(BC);
+        WriteBitcodeToFile(MPart.get(), BCOS);
+
+        // Enqueue the task
+        CodegenThreadPool.async(
+            [&](const SmallString<0> &BC, unsigned ThreadId) {
+              LTOLLVMContext Ctx(C);
+              Expected<std::unique_ptr<Module>> MOrErr = parseBitcodeFile(
+                  MemoryBufferRef(StringRef(BC.data(), BC.size()), "ld-temp.o"),
+                  Ctx);
+              if (!MOrErr)
+                report_fatal_error("Failed to read bitcode");
+              std::unique_ptr<Module> MPartInCtx = std::move(MOrErr.get());
+
+              std::unique_ptr<TargetMachine> TM =
+                  createTargetMachine(C, T, *MPartInCtx);
+
+              codegen(C, TM.get(), AddStream, ThreadId, *MPartInCtx);
+            },
+            // Pass BC using std::move to ensure that it get moved rather than
+            // copied into the thread's context.
+            std::move(BC), ThreadCount++);
+      },
+      false);
+
+  // Because the inner lambda (which runs in a worker thread) captures our local
+  // variables, we need to wait for the worker threads to terminate before we
+  // can leave the function scope.
+  CodegenThreadPool.wait();
+}
+
+Expected<const Target *> initAndLookupTarget(Config &C, Module &Mod) {
+  if (!C.OverrideTriple.empty())
+    Mod.setTargetTriple(C.OverrideTriple);
+  else if (Mod.getTargetTriple().empty())
+    Mod.setTargetTriple(C.DefaultTriple);
+
+  std::string Msg;
+  const Target *T = TargetRegistry::lookupTarget(Mod.getTargetTriple(), Msg);
+  if (!T)
+    return make_error<StringError>(Msg, inconvertibleErrorCode());
+  return T;
+}
+
+}
+
+static void
+finalizeOptimizationRemarks(std::unique_ptr<ToolOutputFile> DiagOutputFile) {
+  // Make sure we flush the diagnostic remarks file in case the linker doesn't
+  // call the global destructors before exiting.
+  if (!DiagOutputFile)
+    return;
+  DiagOutputFile->keep();
+  DiagOutputFile->os().flush();
+}
+
+Error lto::backend(Config &C, AddStreamFn AddStream,
+                   unsigned ParallelCodeGenParallelismLevel,
+                   std::unique_ptr<Module> Mod,
+                   ModuleSummaryIndex &CombinedIndex) {
+  Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod);
+  if (!TOrErr)
+    return TOrErr.takeError();
+
+  std::unique_ptr<TargetMachine> TM = createTargetMachine(C, *TOrErr, *Mod);
+
+  // Setup optimization remarks.
+  auto DiagFileOrErr = lto::setupOptimizationRemarks(
+      Mod->getContext(), C.RemarksFilename, C.RemarksWithHotness);
+  if (!DiagFileOrErr)
+    return DiagFileOrErr.takeError();
+  auto DiagnosticOutputFile = std::move(*DiagFileOrErr);
+
+  if (!C.CodeGenOnly) {
+    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false,
+             /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr)) {
+      finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
+      return Error::success();
+    }
+  }
+
+  if (ParallelCodeGenParallelismLevel == 1) {
+    codegen(C, TM.get(), AddStream, 0, *Mod);
+  } else {
+    splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,
+                 std::move(Mod));
+  }
+  finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));
+  return Error::success();
+}
+
+Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
+                       Module &Mod, const ModuleSummaryIndex &CombinedIndex,
+                       const FunctionImporter::ImportMapTy &ImportList,
+                       const GVSummaryMapTy &DefinedGlobals,
+                       MapVector<StringRef, BitcodeModule> &ModuleMap) {
+  Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
+  if (!TOrErr)
+    return TOrErr.takeError();
+
+  std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod);
+
+  if (Conf.CodeGenOnly) {
+    codegen(Conf, TM.get(), AddStream, Task, Mod);
+    return Error::success();
+  }
+
+  if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
+    return Error::success();
+
+  renameModuleForThinLTO(Mod, CombinedIndex);
+
+  thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
+
+  if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
+    return Error::success();
+
+  if (!DefinedGlobals.empty())
+    thinLTOInternalizeModule(Mod, DefinedGlobals);
+
+  if (Conf.PostInternalizeModuleHook &&
+      !Conf.PostInternalizeModuleHook(Task, Mod))
+    return Error::success();
+
+  auto ModuleLoader = [&](StringRef Identifier) {
+    assert(Mod.getContext().isODRUniquingDebugTypes() &&
+           "ODR Type uniquing should be enabled on the context");
+    auto I = ModuleMap.find(Identifier);
+    assert(I != ModuleMap.end());
+    return I->second.getLazyModule(Mod.getContext(),
+                                   /*ShouldLazyLoadMetadata=*/true,
+                                   /*IsImporting*/ true);
+  };
+
+  FunctionImporter Importer(CombinedIndex, ModuleLoader);
+  if (Error Err = Importer.importFunctions(Mod, ImportList).takeError())
+    return Err;
+
+  if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
+    return Error::success();
+
+  if (!opt(Conf, TM.get(), Task, Mod, /*IsThinLTO=*/true,
+           /*ExportSummary=*/nullptr, /*ImportSummary=*/&CombinedIndex))
+    return Error::success();
+
+  codegen(Conf, TM.get(), AddStream, Task, Mod);
+  return Error::success();
+}

external/llvm/lib/LTO/UpdateCompilerUsed.cpp

@@ -0,0 +1,127 @@
+//==-LTOInternalize.cpp - LLVM Link Time Optimizer Internalization Utility -==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a helper to run the internalization part of LTO.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/legacy/UpdateCompilerUsed.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/CodeGen/TargetLowering.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+
+using namespace llvm;
+
+namespace {
+
+// Helper class that collects AsmUsed and user supplied libcalls.
+class PreserveLibCallsAndAsmUsed {
+public:
+  PreserveLibCallsAndAsmUsed(const StringSet<> &AsmUndefinedRefs,
+                             const TargetMachine &TM,
+                             std::vector<GlobalValue *> &LLVMUsed)
+      : AsmUndefinedRefs(AsmUndefinedRefs), TM(TM), LLVMUsed(LLVMUsed) {}
+
+  void findInModule(Module &TheModule) {
+    initializeLibCalls(TheModule);
+    for (Function &F : TheModule)
+      findLibCallsAndAsm(F);
+    for (GlobalVariable &GV : TheModule.globals())
+      findLibCallsAndAsm(GV);
+    for (GlobalAlias &GA : TheModule.aliases())
+      findLibCallsAndAsm(GA);
+  }
+
+private:
+  // Inputs
+  const StringSet<> &AsmUndefinedRefs;
+  const TargetMachine &TM;
+
+  // Temps
+  llvm::Mangler Mangler;
+  StringSet<> Libcalls;
+
+  // Output
+  std::vector<GlobalValue *> &LLVMUsed;
+
+  // Collect names of runtime library functions. User-defined functions with the
+  // same names are added to llvm.compiler.used to prevent them from being
+  // deleted by optimizations.
+  void initializeLibCalls(const Module &TheModule) {
+    TargetLibraryInfoImpl TLII(Triple(TM.getTargetTriple()));
+    TargetLibraryInfo TLI(TLII);
+
+    // TargetLibraryInfo has info on C runtime library calls on the current
+    // target.
+    for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
+         I != E; ++I) {
+      LibFunc F = static_cast<LibFunc>(I);
+      if (TLI.has(F))
+        Libcalls.insert(TLI.getName(F));
+    }
+
+    SmallPtrSet<const TargetLowering *, 1> TLSet;
+
+    for (const Function &F : TheModule) {
+      const TargetLowering *Lowering =
+          TM.getSubtargetImpl(F)->getTargetLowering();
+
+      if (Lowering && TLSet.insert(Lowering).second)
+        // TargetLowering has info on library calls that CodeGen expects to be
+        // available, both from the C runtime and compiler-rt.
+        for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
+             I != E; ++I)
+          if (const char *Name =
+                  Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
+            Libcalls.insert(Name);
+    }
+  }
+
+  void findLibCallsAndAsm(GlobalValue &GV) {
+    // There are no restrictions to apply to declarations.
+    if (GV.isDeclaration())
+      return;
+
+    // There is nothing more restrictive than private linkage.
+    if (GV.hasPrivateLinkage())
+      return;
+
+    // Conservatively append user-supplied runtime library functions to
+    // llvm.compiler.used.  These could be internalized and deleted by
+    // optimizations like -globalopt, causing problems when later optimizations
+    // add new library calls (e.g., llvm.memset => memset and printf => puts).
+    // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
+    if (isa<Function>(GV) && Libcalls.count(GV.getName())) {
+      LLVMUsed.push_back(&GV);
+      return;
+    }
+
+    SmallString<64> Buffer;
+    TM.getNameWithPrefix(Buffer, &GV, Mangler);
+    if (AsmUndefinedRefs.count(Buffer))
+      LLVMUsed.push_back(&GV);
+  }
+};
+
+} // namespace anonymous
+
+void llvm::updateCompilerUsed(Module &TheModule, const TargetMachine &TM,
+                              const StringSet<> &AsmUndefinedRefs) {
+  std::vector<GlobalValue *> UsedValues;
+  PreserveLibCallsAndAsmUsed(AsmUndefinedRefs, TM, UsedValues)
+      .findInModule(TheModule);
+
+  if (UsedValues.empty())
+    return;
+
+  appendToCompilerUsed(TheModule, UsedValues);
+}