llvm/lib/LTO/ThinLTOCodeGenerator.cpp

   1 //===-ThinLTOCodeGenerator.cpp - LLVM Link Time Optimizer -----------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the Thin Link Time Optimization library. This library is
  10 // intended to be used by linker to optimize code at link time.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/LTO/legacy/ThinLTOCodeGenerator.h"
  15 #include "llvm/Support/CommandLine.h"
  16
  17 #include "llvm/ADT/ScopeExit.h"
  18 #include "llvm/ADT/Statistic.h"
  19 #include "llvm/ADT/StringExtras.h"
  20 #include "llvm/Analysis/AliasAnalysis.h"
  21 #include "llvm/Analysis/ModuleSummaryAnalysis.h"
  22 #include "llvm/Analysis/ProfileSummaryInfo.h"
  23 #include "llvm/Analysis/TargetLibraryInfo.h"
  24 #include "llvm/Analysis/TargetTransformInfo.h"
  25 #include "llvm/Bitcode/BitcodeReader.h"
  26 #include "llvm/Bitcode/BitcodeWriter.h"
  27 #include "llvm/Bitcode/BitcodeWriterPass.h"
  28 #include "llvm/Config/llvm-config.h"
  29 #include "llvm/IR/DebugInfo.h"
  30 #include "llvm/IR/DiagnosticPrinter.h"
  31 #include "llvm/IR/LLVMContext.h"
  32 #include "llvm/IR/LLVMRemarkStreamer.h"
  33 #include "llvm/IR/LegacyPassManager.h"
  34 #include "llvm/IR/Mangler.h"
  35 #include "llvm/IR/PassTimingInfo.h"
  36 #include "llvm/IR/Verifier.h"
  37 #include "llvm/IRReader/IRReader.h"
  38 #include "llvm/LTO/LTO.h"
  39 #include "llvm/LTO/SummaryBasedOptimizations.h"
  40 #include "llvm/MC/SubtargetFeature.h"
  41 #include "llvm/MC/TargetRegistry.h"
  42 #include "llvm/Object/IRObjectFile.h"
  43 #include "llvm/Passes/PassBuilder.h"
  44 #include "llvm/Passes/StandardInstrumentations.h"
  45 #include "llvm/Remarks/HotnessThresholdParser.h"
  46 #include "llvm/Support/CachePruning.h"
  47 #include "llvm/Support/Debug.h"
  48 #include "llvm/Support/Error.h"
  49 #include "llvm/Support/FileUtilities.h"
  50 #include "llvm/Support/Path.h"
  51 #include "llvm/Support/SHA1.h"
  52 #include "llvm/Support/SmallVectorMemoryBuffer.h"
  53 #include "llvm/Support/ThreadPool.h"
  54 #include "llvm/Support/Threading.h"
  55 #include "llvm/Support/ToolOutputFile.h"
  56 #include "llvm/Target/TargetMachine.h"
  57 #include "llvm/Transforms/IPO.h"
  58 #include "llvm/Transforms/IPO/FunctionAttrs.h"
  59 #include "llvm/Transforms/IPO/FunctionImport.h"
  60 #include "llvm/Transforms/IPO/Internalize.h"
  61 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
  62 #include "llvm/Transforms/IPO/WholeProgramDevirt.h"
  63 #include "llvm/Transforms/ObjCARC.h"
  64 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
  65
  66 #include <numeric>
  67
  68 #if !defined(_MSC_VER) && !defined(__MINGW32__)
  69 #include <unistd.h>
  70 #else
  71 #include <io.h>
  72 #endif
  73
  74 using namespace llvm;
  75
  76 #define DEBUG_TYPE "thinlto"
  77
  78 namespace llvm {
  79 // Flags -discard-value-names, defined in LTOCodeGenerator.cpp
  80 extern cl::opt<bool> LTODiscardValueNames;
  81 extern cl::opt<std::string> RemarksFilename;
  82 extern cl::opt<std::string> RemarksPasses;
  83 extern cl::opt<bool> RemarksWithHotness;
  84 extern cl::opt<Optional<uint64_t>, false, remarks::HotnessThresholdParser>
  85     RemarksHotnessThreshold;
  86 extern cl::opt<std::string> RemarksFormat;
  87 }
  88
  89 namespace {
  90
  91 // Default to using all available threads in the system, but using only one
  92 // thred per core, as indicated by the usage of
  93 // heavyweight_hardware_concurrency() below.
  94 static cl::opt<int> ThreadCount("threads", cl::init(0));
  95
  96 // Simple helper to save temporary files for debug.
  97 static void saveTempBitcode(const Module &TheModule, StringRef TempDir,
  98                             unsigned count, StringRef Suffix) {
  99   if (TempDir.empty())
 100     return;
 101   // User asked to save temps, let dump the bitcode file after import.
 102   std::string SaveTempPath = (TempDir + llvm::Twine(count) + Suffix).str();
 103   std::error_code EC;
 104   raw_fd_ostream OS(SaveTempPath, EC, sys::fs::OF_None);
 105   if (EC)
 106     report_fatal_error(Twine("Failed to open ") + SaveTempPath +
 107                        " to save optimized bitcode\n");
 108   WriteBitcodeToFile(TheModule, OS, /* ShouldPreserveUseListOrder */ true);
 109 }
 110
 111 static const GlobalValueSummary *
 112 getFirstDefinitionForLinker(const GlobalValueSummaryList &GVSummaryList) {
 113   // If there is any strong definition anywhere, get it.
 114   auto StrongDefForLinker = llvm::find_if(
 115       GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
 116         auto Linkage = Summary->linkage();
 117         return !GlobalValue::isAvailableExternallyLinkage(Linkage) &&
 118                !GlobalValue::isWeakForLinker(Linkage);
 119       });
 120   if (StrongDefForLinker != GVSummaryList.end())
 121     return StrongDefForLinker->get();
 122   // Get the first *linker visible* definition for this global in the summary
 123   // list.
 124   auto FirstDefForLinker = llvm::find_if(
 125       GVSummaryList, [](const std::unique_ptr<GlobalValueSummary> &Summary) {
 126         auto Linkage = Summary->linkage();
 127         return !GlobalValue::isAvailableExternallyLinkage(Linkage);
 128       });
 129   // Extern templates can be emitted as available_externally.
 130   if (FirstDefForLinker == GVSummaryList.end())
 131     return nullptr;
 132   return FirstDefForLinker->get();
 133 }
 134
 135 // Populate map of GUID to the prevailing copy for any multiply defined
 136 // symbols. Currently assume first copy is prevailing, or any strong
 137 // definition. Can be refined with Linker information in the future.
 138 static void computePrevailingCopies(
 139     const ModuleSummaryIndex &Index,
 140     DenseMap<GlobalValue::GUID, const GlobalValueSummary *> &PrevailingCopy) {
 141   auto HasMultipleCopies = [&](const GlobalValueSummaryList &GVSummaryList) {
 142     return GVSummaryList.size() > 1;
 143   };
 144
 145   for (auto &I : Index) {
 146     if (HasMultipleCopies(I.second.SummaryList))
 147       PrevailingCopy[I.first] =
 148           getFirstDefinitionForLinker(I.second.SummaryList);
 149   }
 150 }
 151
 152 static StringMap<lto::InputFile *>
 153 generateModuleMap(std::vector<std::unique_ptr<lto::InputFile>> &Modules) {
 154   StringMap<lto::InputFile *> ModuleMap;
 155   for (auto &M : Modules) {
 156     assert(ModuleMap.find(M->getName()) == ModuleMap.end() &&
 157            "Expect unique Buffer Identifier");
 158     ModuleMap[M->getName()] = M.get();
 159   }
 160   return ModuleMap;
 161 }
 162
 163 static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index,
 164                           bool ClearDSOLocalOnDeclarations) {
 165   if (renameModuleForThinLTO(TheModule, Index, ClearDSOLocalOnDeclarations))
 166     report_fatal_error("renameModuleForThinLTO failed");
 167 }
 168
 169 namespace {
 170 class ThinLTODiagnosticInfo : public DiagnosticInfo {
 171   const Twine &Msg;
 172 public:
 173   ThinLTODiagnosticInfo(const Twine &DiagMsg,
 174                         DiagnosticSeverity Severity = DS_Error)
 175       : DiagnosticInfo(DK_Linker, Severity), Msg(DiagMsg) {}
 176   void print(DiagnosticPrinter &DP) const override { DP << Msg; }
 177 };
 178 }
 179
 180 /// Verify the module and strip broken debug info.
 181 static void verifyLoadedModule(Module &TheModule) {
 182   bool BrokenDebugInfo = false;
 183   if (verifyModule(TheModule, &dbgs(), &BrokenDebugInfo))
 184     report_fatal_error("Broken module found, compilation aborted!");
 185   if (BrokenDebugInfo) {
 186     TheModule.getContext().diagnose(ThinLTODiagnosticInfo(
 187         "Invalid debug info found, debug info will be stripped", DS_Warning));
 188     StripDebugInfo(TheModule);
 189   }
 190 }
 191
 192 static std::unique_ptr<Module> loadModuleFromInput(lto::InputFile *Input,
 193                                                    LLVMContext &Context,
 194                                                    bool Lazy,
 195                                                    bool IsImporting) {
 196   auto &Mod = Input->getSingleBitcodeModule();
 197   SMDiagnostic Err;
 198   Expected<std::unique_ptr<Module>> ModuleOrErr =
 199       Lazy ? Mod.getLazyModule(Context,
 200                                /* ShouldLazyLoadMetadata */ true, IsImporting)
 201            : Mod.parseModule(Context);
 202   if (!ModuleOrErr) {
 203     handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
 204       SMDiagnostic Err = SMDiagnostic(Mod.getModuleIdentifier(),
 205                                       SourceMgr::DK_Error, EIB.message());
 206       Err.print("ThinLTO", errs());
 207     });
 208     report_fatal_error("Can't load module, abort.");
 209   }
 210   if (!Lazy)
 211     verifyLoadedModule(*ModuleOrErr.get());
 212   return std::move(*ModuleOrErr);
 213 }
 214
 215 static void
 216 crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
 217                       StringMap<lto::InputFile *> &ModuleMap,
 218                       const FunctionImporter::ImportMapTy &ImportList,
 219                       bool ClearDSOLocalOnDeclarations) {
 220   auto Loader = [&](StringRef Identifier) {
 221     auto &Input = ModuleMap[Identifier];
 222     return loadModuleFromInput(Input, TheModule.getContext(),
 223                                /*Lazy=*/true, /*IsImporting*/ true);
 224   };
 225
 226   FunctionImporter Importer(Index, Loader, ClearDSOLocalOnDeclarations);
 227   Expected<bool> Result = Importer.importFunctions(TheModule, ImportList);
 228   if (!Result) {
 229     handleAllErrors(Result.takeError(), [&](ErrorInfoBase &EIB) {
 230       SMDiagnostic Err = SMDiagnostic(TheModule.getModuleIdentifier(),
 231                                       SourceMgr::DK_Error, EIB.message());
 232       Err.print("ThinLTO", errs());
 233     });
 234     report_fatal_error("importFunctions failed");
 235   }
 236   // Verify again after cross-importing.
 237   verifyLoadedModule(TheModule);
 238 }
 239
 240 static void optimizeModule(Module &TheModule, TargetMachine &TM,
 241                            unsigned OptLevel, bool Freestanding,
 242                            ModuleSummaryIndex *Index) {
 243   // Populate the PassManager
 244   PassManagerBuilder PMB;
 245   PMB.LibraryInfo = new TargetLibraryInfoImpl(TM.getTargetTriple());
 246   if (Freestanding)
 247     PMB.LibraryInfo->disableAllFunctions();
 248   PMB.Inliner = createFunctionInliningPass();
 249   // FIXME: should get it from the bitcode?
 250   PMB.OptLevel = OptLevel;
 251   PMB.LoopVectorize = true;
 252   PMB.SLPVectorize = true;
 253   // Already did this in verifyLoadedModule().
 254   PMB.VerifyInput = false;
 255   PMB.VerifyOutput = false;
 256   PMB.ImportSummary = Index;
 257
 258   legacy::PassManager PM;
 259
 260   // Add the TTI (required to inform the vectorizer about register size for
 261   // instance)
 262   PM.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
 263
 264   // Add optimizations
 265   PMB.populateThinLTOPassManager(PM);
 266
 267   PM.run(TheModule);
 268 }
 269
 270 static void optimizeModuleNewPM(Module &TheModule, TargetMachine &TM,
 271                                 unsigned OptLevel, bool Freestanding,
 272                                 bool DebugPassManager,
 273                                 ModuleSummaryIndex *Index) {
 274   Optional<PGOOptions> PGOOpt;
 275   LoopAnalysisManager LAM;
 276   FunctionAnalysisManager FAM;
 277   CGSCCAnalysisManager CGAM;
 278   ModuleAnalysisManager MAM;
 279
 280   PassInstrumentationCallbacks PIC;
 281   StandardInstrumentations SI(DebugPassManager);
 282   SI.registerCallbacks(PIC, &FAM);
 283   PipelineTuningOptions PTO;
 284   PTO.LoopVectorization = true;
 285   PTO.SLPVectorization = true;
 286   PassBuilder PB(&TM, PTO, PGOOpt, &PIC);
 287
 288   std::unique_ptr<TargetLibraryInfoImpl> TLII(
 289       new TargetLibraryInfoImpl(Triple(TM.getTargetTriple())));
 290   if (Freestanding)
 291     TLII->disableAllFunctions();
 292   FAM.registerPass([&] { return TargetLibraryAnalysis(*TLII); });
 293
 294   // Register all the basic analyses with the managers.
 295   PB.registerModuleAnalyses(MAM);
 296   PB.registerCGSCCAnalyses(CGAM);
 297   PB.registerFunctionAnalyses(FAM);
 298   PB.registerLoopAnalyses(LAM);
 299   PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
 300
 301   ModulePassManager MPM;
 302
 303   OptimizationLevel OL;
 304
 305   switch (OptLevel) {
 306   default:
 307     llvm_unreachable("Invalid optimization level");
 308   case 0:
 309     OL = OptimizationLevel::O0;
 310     break;
 311   case 1:
 312     OL = OptimizationLevel::O1;
 313     break;
 314   case 2:
 315     OL = OptimizationLevel::O2;
 316     break;
 317   case 3:
 318     OL = OptimizationLevel::O3;
 319     break;
 320   }
 321
 322   MPM.addPass(PB.buildThinLTODefaultPipeline(OL, Index));
 323
 324   MPM.run(TheModule, MAM);
 325 }
 326
 327 static void
 328 addUsedSymbolToPreservedGUID(const lto::InputFile &File,
 329                              DenseSet<GlobalValue::GUID> &PreservedGUID) {
 330   for (const auto &Sym : File.symbols()) {
 331     if (Sym.isUsed())
 332       PreservedGUID.insert(GlobalValue::getGUID(Sym.getIRName()));
 333   }
 334 }
 335
 336 // Convert the PreservedSymbols map from "Name" based to "GUID" based.
 337 static void computeGUIDPreservedSymbols(const lto::InputFile &File,
 338                                         const StringSet<> &PreservedSymbols,
 339                                         const Triple &TheTriple,
 340                                         DenseSet<GlobalValue::GUID> &GUIDs) {
 341   // Iterate the symbols in the input file and if the input has preserved symbol
 342   // compute the GUID for the symbol.
 343   for (const auto &Sym : File.symbols()) {
 344     if (PreservedSymbols.count(Sym.getName()) && !Sym.getIRName().empty())
 345       GUIDs.insert(GlobalValue::getGUID(GlobalValue::getGlobalIdentifier(
 346           Sym.getIRName(), GlobalValue::ExternalLinkage, "")));
 347   }
 348 }
 349
 350 static DenseSet<GlobalValue::GUID>
 351 computeGUIDPreservedSymbols(const lto::InputFile &File,
 352                             const StringSet<> &PreservedSymbols,
 353                             const Triple &TheTriple) {
 354   DenseSet<GlobalValue::GUID> GUIDPreservedSymbols(PreservedSymbols.size());
 355   computeGUIDPreservedSymbols(File, PreservedSymbols, TheTriple,
 356                               GUIDPreservedSymbols);
 357   return GUIDPreservedSymbols;
 358 }
 359
 360 std::unique_ptr<MemoryBuffer> codegenModule(Module &TheModule,
 361                                             TargetMachine &TM) {
 362   SmallVector<char, 128> OutputBuffer;
 363
 364   // CodeGen
 365   {
 366     raw_svector_ostream OS(OutputBuffer);
 367     legacy::PassManager PM;
 368
 369     // If the bitcode files contain ARC code and were compiled with optimization,
 370     // the ObjCARCContractPass must be run, so do it unconditionally here.
 371     PM.add(createObjCARCContractPass());
 372
 373     // Setup the codegen now.
 374     if (TM.addPassesToEmitFile(PM, OS, nullptr, CGFT_ObjectFile,
 375                                /* DisableVerify */ true))
 376       report_fatal_error("Failed to setup codegen");
 377
 378     // Run codegen now. resulting binary is in OutputBuffer.
 379     PM.run(TheModule);
 380   }
 381   return std::make_unique<SmallVectorMemoryBuffer>(
 382       std::move(OutputBuffer), /*RequiresNullTerminator=*/false);
 383 }
 384
 385 /// Manage caching for a single Module.
 386 class ModuleCacheEntry {
 387   SmallString<128> EntryPath;
 388
 389 public:
 390   // Create a cache entry. This compute a unique hash for the Module considering
 391   // the current list of export/import, and offer an interface to query to
 392   // access the content in the cache.
 393   ModuleCacheEntry(
 394       StringRef CachePath, const ModuleSummaryIndex &Index, StringRef ModuleID,
 395       const FunctionImporter::ImportMapTy &ImportList,
 396       const FunctionImporter::ExportSetTy &ExportList,
 397       const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
 398       const GVSummaryMapTy &DefinedGVSummaries, unsigned OptLevel,
 399       bool Freestanding, const TargetMachineBuilder &TMBuilder) {
 400     if (CachePath.empty())
 401       return;
 402
 403     if (!Index.modulePaths().count(ModuleID))
 404       // The module does not have an entry, it can't have a hash at all
 405       return;
 406
 407     if (all_of(Index.getModuleHash(ModuleID),
 408                [](uint32_t V) { return V == 0; }))
 409       // No hash entry, no caching!
 410       return;
 411
 412     llvm::lto::Config Conf;
 413     Conf.OptLevel = OptLevel;
 414     Conf.Options = TMBuilder.Options;
 415     Conf.CPU = TMBuilder.MCpu;
 416     Conf.MAttrs.push_back(TMBuilder.MAttr);
 417     Conf.RelocModel = TMBuilder.RelocModel;
 418     Conf.CGOptLevel = TMBuilder.CGOptLevel;
 419     Conf.Freestanding = Freestanding;
 420     SmallString<40> Key;
 421     computeLTOCacheKey(Key, Conf, Index, ModuleID, ImportList, ExportList,
 422                        ResolvedODR, DefinedGVSummaries);
 423
 424     // This choice of file name allows the cache to be pruned (see pruneCache()
 425     // in include/llvm/Support/CachePruning.h).
 426     sys::path::append(EntryPath, CachePath, "llvmcache-" + Key);
 427   }
 428
 429   // Access the path to this entry in the cache.
 430   StringRef getEntryPath() { return EntryPath; }
 431
 432   // Try loading the buffer for this cache entry.
 433   ErrorOr<std::unique_ptr<MemoryBuffer>> tryLoadingBuffer() {
 434     if (EntryPath.empty())
 435       return std::error_code();
 436     SmallString<64> ResultPath;
 437     Expected<sys::fs::file_t> FDOrErr = sys::fs::openNativeFileForRead(
 438         Twine(EntryPath), sys::fs::OF_UpdateAtime, &ResultPath);
 439     if (!FDOrErr)
 440       return errorToErrorCode(FDOrErr.takeError());
 441     ErrorOr<std::unique_ptr<MemoryBuffer>> MBOrErr = MemoryBuffer::getOpenFile(
 442         *FDOrErr, EntryPath, /*FileSize=*/-1, /*RequiresNullTerminator=*/false);
 443     sys::fs::closeFile(*FDOrErr);
 444     return MBOrErr;
 445   }
 446
 447   // Cache the Produced object file
 448   void write(const MemoryBuffer &OutputBuffer) {
 449     if (EntryPath.empty())
 450       return;
 451
 452     // Write to a temporary to avoid race condition
 453     SmallString<128> TempFilename;
 454     SmallString<128> CachePath(EntryPath);
 455     llvm::sys::path::remove_filename(CachePath);
 456     sys::path::append(TempFilename, CachePath, "Thin-%%%%%%.tmp.o");
 457
 458     if (auto Err = handleErrors(
 459             llvm::writeFileAtomically(TempFilename, EntryPath,
 460                                       OutputBuffer.getBuffer()),
 461             [](const llvm::AtomicFileWriteError &E) {
 462               std::string ErrorMsgBuffer;
 463               llvm::raw_string_ostream S(ErrorMsgBuffer);
 464               E.log(S);
 465
 466               if (E.Error ==
 467                   llvm::atomic_write_error::failed_to_create_uniq_file) {
 468                 errs() << "Error: " << ErrorMsgBuffer << "\n";
 469                 report_fatal_error("ThinLTO: Can't get a temporary file");
 470               }
 471             })) {
 472       // FIXME
 473       consumeError(std::move(Err));
 474     }
 475   }
 476 };
 477
 478 static std::unique_ptr<MemoryBuffer>
 479 ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
 480                      StringMap<lto::InputFile *> &ModuleMap, TargetMachine &TM,
 481                      const FunctionImporter::ImportMapTy &ImportList,
 482                      const FunctionImporter::ExportSetTy &ExportList,
 483                      const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
 484                      const GVSummaryMapTy &DefinedGlobals,
 485                      const ThinLTOCodeGenerator::CachingOptions &CacheOptions,
 486                      bool DisableCodeGen, StringRef SaveTempsDir,
 487                      bool Freestanding, unsigned OptLevel, unsigned count,
 488                      bool UseNewPM, bool DebugPassManager) {
 489
 490   // "Benchmark"-like optimization: single-source case
 491   bool SingleModule = (ModuleMap.size() == 1);
 492
 493   // When linking an ELF shared object, dso_local should be dropped. We
 494   // conservatively do this for -fpic.
 495   bool ClearDSOLocalOnDeclarations =
 496       TM.getTargetTriple().isOSBinFormatELF() &&
 497       TM.getRelocationModel() != Reloc::Static &&
 498       TheModule.getPIELevel() == PIELevel::Default;
 499
 500   if (!SingleModule) {
 501     promoteModule(TheModule, Index, ClearDSOLocalOnDeclarations);
 502
 503     // Apply summary-based prevailing-symbol resolution decisions.
 504     thinLTOFinalizeInModule(TheModule, DefinedGlobals, /*PropagateAttrs=*/true);
 505
 506     // Save temps: after promotion.
 507     saveTempBitcode(TheModule, SaveTempsDir, count, ".1.promoted.bc");
 508   }
 509
 510   // Be friendly and don't nuke totally the module when the client didn't
 511   // supply anything to preserve.
 512   if (!ExportList.empty() || !GUIDPreservedSymbols.empty()) {
 513     // Apply summary-based internalization decisions.
 514     thinLTOInternalizeModule(TheModule, DefinedGlobals);
 515   }
 516
 517   // Save internalized bitcode
 518   saveTempBitcode(TheModule, SaveTempsDir, count, ".2.internalized.bc");
 519
 520   if (!SingleModule) {
 521     crossImportIntoModule(TheModule, Index, ModuleMap, ImportList,
 522                           ClearDSOLocalOnDeclarations);
 523
 524     // Save temps: after cross-module import.
 525     saveTempBitcode(TheModule, SaveTempsDir, count, ".3.imported.bc");
 526   }
 527
 528   if (UseNewPM)
 529     optimizeModuleNewPM(TheModule, TM, OptLevel, Freestanding, DebugPassManager,
 530                         &Index);
 531   else
 532     optimizeModule(TheModule, TM, OptLevel, Freestanding, &Index);
 533
 534   saveTempBitcode(TheModule, SaveTempsDir, count, ".4.opt.bc");
 535
 536   if (DisableCodeGen) {
 537     // Configured to stop before CodeGen, serialize the bitcode and return.
 538     SmallVector<char, 128> OutputBuffer;
 539     {
 540       raw_svector_ostream OS(OutputBuffer);
 541       ProfileSummaryInfo PSI(TheModule);
 542       auto Index = buildModuleSummaryIndex(TheModule, nullptr, &PSI);
 543       WriteBitcodeToFile(TheModule, OS, true, &Index);
 544     }
 545     return std::make_unique<SmallVectorMemoryBuffer>(
 546         std::move(OutputBuffer), /*RequiresNullTerminator=*/false);
 547   }
 548
 549   return codegenModule(TheModule, TM);
 550 }
 551
 552 /// Resolve prevailing symbols. Record resolutions in the \p ResolvedODR map
 553 /// for caching, and in the \p Index for application during the ThinLTO
 554 /// backends. This is needed for correctness for exported symbols (ensure
 555 /// at least one copy kept) and a compile-time optimization (to drop duplicate
 556 /// copies when possible).
 557 static void resolvePrevailingInIndex(
 558     ModuleSummaryIndex &Index,
 559     StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>>
 560         &ResolvedODR,
 561     const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
 562     const DenseMap<GlobalValue::GUID, const GlobalValueSummary *>
 563         &PrevailingCopy) {
 564
 565   auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
 566     const auto &Prevailing = PrevailingCopy.find(GUID);
 567     // Not in map means that there was only one copy, which must be prevailing.
 568     if (Prevailing == PrevailingCopy.end())
 569       return true;
 570     return Prevailing->second == S;
 571   };
 572
 573   auto recordNewLinkage = [&](StringRef ModuleIdentifier,
 574                               GlobalValue::GUID GUID,
 575                               GlobalValue::LinkageTypes NewLinkage) {
 576     ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
 577   };
 578
 579   // TODO Conf.VisibilityScheme can be lto::Config::ELF for ELF.
 580   lto::Config Conf;
 581   thinLTOResolvePrevailingInIndex(Conf, Index, isPrevailing, recordNewLinkage,
 582                                   GUIDPreservedSymbols);
 583 }
 584
 585 // Initialize the TargetMachine builder for a given Triple
 586 static void initTMBuilder(TargetMachineBuilder &TMBuilder,
 587                           const Triple &TheTriple) {
 588   // Set a default CPU for Darwin triples (copied from LTOCodeGenerator).
 589   // FIXME this looks pretty terrible...
 590   if (TMBuilder.MCpu.empty() && TheTriple.isOSDarwin()) {
 591     if (TheTriple.getArch() == llvm::Triple::x86_64)
 592       TMBuilder.MCpu = "core2";
 593     else if (TheTriple.getArch() == llvm::Triple::x86)
 594       TMBuilder.MCpu = "yonah";
 595     else if (TheTriple.getArch() == llvm::Triple::aarch64 ||
 596              TheTriple.getArch() == llvm::Triple::aarch64_32)
 597       TMBuilder.MCpu = "cyclone";
 598   }
 599   TMBuilder.TheTriple = std::move(TheTriple);
 600 }
 601
 602 } // end anonymous namespace
 603
 604 void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
 605   MemoryBufferRef Buffer(Data, Identifier);
 606
 607   auto InputOrError = lto::InputFile::create(Buffer);
 608   if (!InputOrError)
 609     report_fatal_error(Twine("ThinLTO cannot create input file: ") +
 610                        toString(InputOrError.takeError()));
 611
 612   auto TripleStr = (*InputOrError)->getTargetTriple();
 613   Triple TheTriple(TripleStr);
 614
 615   if (Modules.empty())
 616     initTMBuilder(TMBuilder, Triple(TheTriple));
 617   else if (TMBuilder.TheTriple != TheTriple) {
 618     if (!TMBuilder.TheTriple.isCompatibleWith(TheTriple))
 619       report_fatal_error("ThinLTO modules with incompatible triples not "
 620                          "supported");
 621     initTMBuilder(TMBuilder, Triple(TMBuilder.TheTriple.merge(TheTriple)));
 622   }
 623
 624   Modules.emplace_back(std::move(*InputOrError));
 625 }
 626
 627 void ThinLTOCodeGenerator::preserveSymbol(StringRef Name) {
 628   PreservedSymbols.insert(Name);
 629 }
 630
 631 void ThinLTOCodeGenerator::crossReferenceSymbol(StringRef Name) {
 632   // FIXME: At the moment, we don't take advantage of this extra information,
 633   // we're conservatively considering cross-references as preserved.
 634   //  CrossReferencedSymbols.insert(Name);
 635   PreservedSymbols.insert(Name);
 636 }
 637
 638 // TargetMachine factory
 639 std::unique_ptr<TargetMachine> TargetMachineBuilder::create() const {
 640   std::string ErrMsg;
 641   const Target *TheTarget =
 642       TargetRegistry::lookupTarget(TheTriple.str(), ErrMsg);
 643   if (!TheTarget) {
 644     report_fatal_error(Twine("Can't load target for this Triple: ") + ErrMsg);
 645   }
 646
 647   // Use MAttr as the default set of features.
 648   SubtargetFeatures Features(MAttr);
 649   Features.getDefaultSubtargetFeatures(TheTriple);
 650   std::string FeatureStr = Features.getString();
 651
 652   std::unique_ptr<TargetMachine> TM(
 653       TheTarget->createTargetMachine(TheTriple.str(), MCpu, FeatureStr, Options,
 654                                      RelocModel, None, CGOptLevel));
 655   assert(TM && "Cannot create target machine");
 656
 657   return TM;
 658 }
 659
 660 /**
 661  * Produce the combined summary index from all the bitcode files:
 662  * "thin-link".
 663  */
 664 std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
 665   std::unique_ptr<ModuleSummaryIndex> CombinedIndex =
 666       std::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false);
 667   uint64_t NextModuleId = 0;
 668   for (auto &Mod : Modules) {
 669     auto &M = Mod->getSingleBitcodeModule();
 670     if (Error Err =
 671             M.readSummary(*CombinedIndex, Mod->getName(), NextModuleId++)) {
 672       // FIXME diagnose
 673       logAllUnhandledErrors(
 674           std::move(Err), errs(),
 675           "error: can't create module summary index for buffer: ");
 676       return nullptr;
 677     }
 678   }
 679   return CombinedIndex;
 680 }
 681
 682 namespace {
 683 struct IsExported {
 684   const StringMap<FunctionImporter::ExportSetTy> &ExportLists;
 685   const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols;
 686
 687   IsExported(const StringMap<FunctionImporter::ExportSetTy> &ExportLists,
 688              const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols)
 689       : ExportLists(ExportLists), GUIDPreservedSymbols(GUIDPreservedSymbols) {}
 690
 691   bool operator()(StringRef ModuleIdentifier, ValueInfo VI) const {
 692     const auto &ExportList = ExportLists.find(ModuleIdentifier);
 693     return (ExportList != ExportLists.end() && ExportList->second.count(VI)) ||
 694            GUIDPreservedSymbols.count(VI.getGUID());
 695   }
 696 };
 697
 698 struct IsPrevailing {
 699   const DenseMap<GlobalValue::GUID, const GlobalValueSummary *> &PrevailingCopy;
 700   IsPrevailing(const DenseMap<GlobalValue::GUID, const GlobalValueSummary *>
 701                    &PrevailingCopy)
 702       : PrevailingCopy(PrevailingCopy) {}
 703
 704   bool operator()(GlobalValue::GUID GUID, const GlobalValueSummary *S) const {
 705     const auto &Prevailing = PrevailingCopy.find(GUID);
 706     // Not in map means that there was only one copy, which must be prevailing.
 707     if (Prevailing == PrevailingCopy.end())
 708       return true;
 709     return Prevailing->second == S;
 710   };
 711 };
 712 } // namespace
 713
 714 static void computeDeadSymbolsInIndex(
 715     ModuleSummaryIndex &Index,
 716     const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols) {
 717   // We have no symbols resolution available. And can't do any better now in the
 718   // case where the prevailing symbol is in a native object. It can be refined
 719   // with linker information in the future.
 720   auto isPrevailing = [&](GlobalValue::GUID G) {
 721     return PrevailingType::Unknown;
 722   };
 723   computeDeadSymbolsWithConstProp(Index, GUIDPreservedSymbols, isPrevailing,
 724                                   /* ImportEnabled = */ true);
 725 }
 726
 727 /**
 728  * Perform promotion and renaming of exported internal functions.
 729  * Index is updated to reflect linkage changes from weak resolution.
 730  */
 731 void ThinLTOCodeGenerator::promote(Module &TheModule, ModuleSummaryIndex &Index,
 732                                    const lto::InputFile &File) {
 733   auto ModuleCount = Index.modulePaths().size();
 734   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 735
 736   // Collect for each module the list of function it defines (GUID -> Summary).
 737   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries;
 738   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 739
 740   // Convert the preserved symbols set from string to GUID
 741   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
 742       File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
 743
 744   // Add used symbol to the preserved symbols.
 745   addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
 746
 747   // Compute "dead" symbols, we don't want to import/export these!
 748   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 749
 750   // Generate import/export list
 751   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
 752   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
 753   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
 754                            ExportLists);
 755
 756   DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
 757   computePrevailingCopies(Index, PrevailingCopy);
 758
 759   // Resolve prevailing symbols
 760   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
 761   resolvePrevailingInIndex(Index, ResolvedODR, GUIDPreservedSymbols,
 762                            PrevailingCopy);
 763
 764   thinLTOFinalizeInModule(TheModule,
 765                           ModuleToDefinedGVSummaries[ModuleIdentifier],
 766                           /*PropagateAttrs=*/false);
 767
 768   // Promote the exported values in the index, so that they are promoted
 769   // in the module.
 770   thinLTOInternalizeAndPromoteInIndex(
 771       Index, IsExported(ExportLists, GUIDPreservedSymbols),
 772       IsPrevailing(PrevailingCopy));
 773
 774   // FIXME Set ClearDSOLocalOnDeclarations.
 775   promoteModule(TheModule, Index, /*ClearDSOLocalOnDeclarations=*/false);
 776 }
 777
 778 /**
 779  * Perform cross-module importing for the module identified by ModuleIdentifier.
 780  */
 781 void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
 782                                              ModuleSummaryIndex &Index,
 783                                              const lto::InputFile &File) {
 784   auto ModuleMap = generateModuleMap(Modules);
 785   auto ModuleCount = Index.modulePaths().size();
 786
 787   // Collect for each module the list of function it defines (GUID -> Summary).
 788   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
 789   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 790
 791   // Convert the preserved symbols set from string to GUID
 792   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
 793       File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
 794
 795   addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
 796
 797   // Compute "dead" symbols, we don't want to import/export these!
 798   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 799
 800   // Generate import/export list
 801   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
 802   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
 803   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
 804                            ExportLists);
 805   auto &ImportList = ImportLists[TheModule.getModuleIdentifier()];
 806
 807   // FIXME Set ClearDSOLocalOnDeclarations.
 808   crossImportIntoModule(TheModule, Index, ModuleMap, ImportList,
 809                         /*ClearDSOLocalOnDeclarations=*/false);
 810 }
 811
 812 /**
 813  * Compute the list of summaries needed for importing into module.
 814  */
 815 void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
 816     Module &TheModule, ModuleSummaryIndex &Index,
 817     std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
 818     const lto::InputFile &File) {
 819   auto ModuleCount = Index.modulePaths().size();
 820   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 821
 822   // Collect for each module the list of function it defines (GUID -> Summary).
 823   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
 824   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 825
 826   // Convert the preserved symbols set from string to GUID
 827   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
 828       File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
 829
 830   addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
 831
 832   // Compute "dead" symbols, we don't want to import/export these!
 833   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 834
 835   // Generate import/export list
 836   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
 837   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
 838   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
 839                            ExportLists);
 840
 841   llvm::gatherImportedSummariesForModule(
 842       ModuleIdentifier, ModuleToDefinedGVSummaries,
 843       ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
 844 }
 845
 846 /**
 847  * Emit the list of files needed for importing into module.
 848  */
 849 void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
 850                                        ModuleSummaryIndex &Index,
 851                                        const lto::InputFile &File) {
 852   auto ModuleCount = Index.modulePaths().size();
 853   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 854
 855   // Collect for each module the list of function it defines (GUID -> Summary).
 856   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
 857   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 858
 859   // Convert the preserved symbols set from string to GUID
 860   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
 861       File, PreservedSymbols, Triple(TheModule.getTargetTriple()));
 862
 863   addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
 864
 865   // Compute "dead" symbols, we don't want to import/export these!
 866   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 867
 868   // Generate import/export list
 869   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
 870   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
 871   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
 872                            ExportLists);
 873
 874   std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
 875   llvm::gatherImportedSummariesForModule(
 876       ModuleIdentifier, ModuleToDefinedGVSummaries,
 877       ImportLists[ModuleIdentifier], ModuleToSummariesForIndex);
 878
 879   std::error_code EC;
 880   if ((EC = EmitImportsFiles(ModuleIdentifier, OutputName,
 881                              ModuleToSummariesForIndex)))
 882     report_fatal_error(Twine("Failed to open ") + OutputName +
 883                        " to save imports lists\n");
 884 }
 885
 886 /**
 887  * Perform internalization. Runs promote and internalization together.
 888  * Index is updated to reflect linkage changes.
 889  */
 890 void ThinLTOCodeGenerator::internalize(Module &TheModule,
 891                                        ModuleSummaryIndex &Index,
 892                                        const lto::InputFile &File) {
 893   initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
 894   auto ModuleCount = Index.modulePaths().size();
 895   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 896
 897   // Convert the preserved symbols set from string to GUID
 898   auto GUIDPreservedSymbols =
 899       computeGUIDPreservedSymbols(File, PreservedSymbols, TMBuilder.TheTriple);
 900
 901   addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
 902
 903   // Collect for each module the list of function it defines (GUID -> Summary).
 904   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
 905   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
 906
 907   // Compute "dead" symbols, we don't want to import/export these!
 908   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 909
 910   // Generate import/export list
 911   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
 912   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
 913   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
 914                            ExportLists);
 915   auto &ExportList = ExportLists[ModuleIdentifier];
 916
 917   // Be friendly and don't nuke totally the module when the client didn't
 918   // supply anything to preserve.
 919   if (ExportList.empty() && GUIDPreservedSymbols.empty())
 920     return;
 921
 922   DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
 923   computePrevailingCopies(Index, PrevailingCopy);
 924
 925   // Resolve prevailing symbols
 926   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
 927   resolvePrevailingInIndex(Index, ResolvedODR, GUIDPreservedSymbols,
 928                            PrevailingCopy);
 929
 930   // Promote the exported values in the index, so that they are promoted
 931   // in the module.
 932   thinLTOInternalizeAndPromoteInIndex(
 933       Index, IsExported(ExportLists, GUIDPreservedSymbols),
 934       IsPrevailing(PrevailingCopy));
 935
 936   // FIXME Set ClearDSOLocalOnDeclarations.
 937   promoteModule(TheModule, Index, /*ClearDSOLocalOnDeclarations=*/false);
 938
 939   // Internalization
 940   thinLTOFinalizeInModule(TheModule,
 941                           ModuleToDefinedGVSummaries[ModuleIdentifier],
 942                           /*PropagateAttrs=*/false);
 943
 944   thinLTOInternalizeModule(TheModule,
 945                            ModuleToDefinedGVSummaries[ModuleIdentifier]);
 946 }
 947
 948 /**
 949  * Perform post-importing ThinLTO optimizations.
 950  */
 951 void ThinLTOCodeGenerator::optimize(Module &TheModule) {
 952   initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
 953
 954   // Optimize now
 955   optimizeModule(TheModule, *TMBuilder.create(), OptLevel, Freestanding,
 956                  nullptr);
 957 }
 958
 959 /// Write out the generated object file, either from CacheEntryPath or from
 960 /// OutputBuffer, preferring hard-link when possible.
 961 /// Returns the path to the generated file in SavedObjectsDirectoryPath.
 962 std::string
 963 ThinLTOCodeGenerator::writeGeneratedObject(int count, StringRef CacheEntryPath,
 964                                            const MemoryBuffer &OutputBuffer) {
 965   auto ArchName = TMBuilder.TheTriple.getArchName();
 966   SmallString<128> OutputPath(SavedObjectsDirectoryPath);
 967   llvm::sys::path::append(OutputPath,
 968                           Twine(count) + "." + ArchName + ".thinlto.o");
 969   OutputPath.c_str(); // Ensure the string is null terminated.
 970   if (sys::fs::exists(OutputPath))
 971     sys::fs::remove(OutputPath);
 972
 973   // We don't return a memory buffer to the linker, just a list of files.
 974   if (!CacheEntryPath.empty()) {
 975     // Cache is enabled, hard-link the entry (or copy if hard-link fails).
 976     auto Err = sys::fs::create_hard_link(CacheEntryPath, OutputPath);
 977     if (!Err)
 978       return std::string(OutputPath.str());
 979     // Hard linking failed, try to copy.
 980     Err = sys::fs::copy_file(CacheEntryPath, OutputPath);
 981     if (!Err)
 982       return std::string(OutputPath.str());
 983     // Copy failed (could be because the CacheEntry was removed from the cache
 984     // in the meantime by another process), fall back and try to write down the
 985     // buffer to the output.
 986     errs() << "remark: can't link or copy from cached entry '" << CacheEntryPath
 987            << "' to '" << OutputPath << "'\n";
 988   }
 989   // No cache entry, just write out the buffer.
 990   std::error_code Err;
 991   raw_fd_ostream OS(OutputPath, Err, sys::fs::OF_None);
 992   if (Err)
 993     report_fatal_error(Twine("Can't open output '") + OutputPath + "'\n");
 994   OS << OutputBuffer.getBuffer();
 995   return std::string(OutputPath.str());
 996 }
 997
 998 // Main entry point for the ThinLTO processing
 999 void ThinLTOCodeGenerator::run() {
1000   timeTraceProfilerBegin("ThinLink", StringRef(""));
1001   auto TimeTraceScopeExit = llvm::make_scope_exit([]() {
1002     if (llvm::timeTraceProfilerEnabled())
1003       llvm::timeTraceProfilerEnd();
1004   });
1005   // Prepare the resulting object vector
1006   assert(ProducedBinaries.empty() && "The generator should not be reused");
1007   if (SavedObjectsDirectoryPath.empty())
1008     ProducedBinaries.resize(Modules.size());
1009   else {
1010     sys::fs::create_directories(SavedObjectsDirectoryPath);
1011     bool IsDir;
1012     sys::fs::is_directory(SavedObjectsDirectoryPath, IsDir);
1013     if (!IsDir)
1014       report_fatal_error(Twine("Unexistent dir: '") + SavedObjectsDirectoryPath + "'");
1015     ProducedBinaryFiles.resize(Modules.size());
1016   }
1017
1018   if (CodeGenOnly) {
1019     // Perform only parallel codegen and return.
1020     ThreadPool Pool;
1021     int count = 0;
1022     for (auto &Mod : Modules) {
1023       Pool.async([&](int count) {
1024         LLVMContext Context;
1025         Context.setDiscardValueNames(LTODiscardValueNames);
1026
1027         // Parse module now
1028         auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
1029                                              /*IsImporting*/ false);
1030
1031         // CodeGen
1032         auto OutputBuffer = codegenModule(*TheModule, *TMBuilder.create());
1033         if (SavedObjectsDirectoryPath.empty())
1034           ProducedBinaries[count] = std::move(OutputBuffer);
1035         else
1036           ProducedBinaryFiles[count] =
1037               writeGeneratedObject(count, "", *OutputBuffer);
1038       }, count++);
1039     }
1040
1041     return;
1042   }
1043
1044   // Sequential linking phase
1045   auto Index = linkCombinedIndex();
1046
1047   // Save temps: index.
1048   if (!SaveTempsDir.empty()) {
1049     auto SaveTempPath = SaveTempsDir + "index.bc";
1050     std::error_code EC;
1051     raw_fd_ostream OS(SaveTempPath, EC, sys::fs::OF_None);
1052     if (EC)
1053       report_fatal_error(Twine("Failed to open ") + SaveTempPath +
1054                          " to save optimized bitcode\n");
1055     WriteIndexToFile(*Index, OS);
1056   }
1057
1058
1059   // Prepare the module map.
1060   auto ModuleMap = generateModuleMap(Modules);
1061   auto ModuleCount = Modules.size();
1062
1063   // Collect for each module the list of function it defines (GUID -> Summary).
1064   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
1065   Index->collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
1066
1067   // Convert the preserved symbols set from string to GUID, this is needed for
1068   // computing the caching hash and the internalization.
1069   DenseSet<GlobalValue::GUID> GUIDPreservedSymbols;
1070   for (const auto &M : Modules)
1071     computeGUIDPreservedSymbols(*M, PreservedSymbols, TMBuilder.TheTriple,
1072                                 GUIDPreservedSymbols);
1073
1074   // Add used symbol from inputs to the preserved symbols.
1075   for (const auto &M : Modules)
1076     addUsedSymbolToPreservedGUID(*M, GUIDPreservedSymbols);
1077
1078   // Compute "dead" symbols, we don't want to import/export these!
1079   computeDeadSymbolsInIndex(*Index, GUIDPreservedSymbols);
1080
1081   // Synthesize entry counts for functions in the combined index.
1082   computeSyntheticCounts(*Index);
1083
1084   // Currently there is no support for enabling whole program visibility via a
1085   // linker option in the old LTO API, but this call allows it to be specified
1086   // via the internal option. Must be done before WPD below.
1087   updateVCallVisibilityInIndex(*Index,
1088                                /* WholeProgramVisibilityEnabledInLTO */ false,
1089                                // FIXME: This needs linker information via a
1090                                // TBD new interface.
1091                                /* DynamicExportSymbols */ {});
1092
1093   // Perform index-based WPD. This will return immediately if there are
1094   // no index entries in the typeIdMetadata map (e.g. if we are instead
1095   // performing IR-based WPD in hybrid regular/thin LTO mode).
1096   std::map<ValueInfo, std::vector<VTableSlotSummary>> LocalWPDTargetsMap;
1097   std::set<GlobalValue::GUID> ExportedGUIDs;
1098   runWholeProgramDevirtOnIndex(*Index, ExportedGUIDs, LocalWPDTargetsMap);
1099   for (auto GUID : ExportedGUIDs)
1100     GUIDPreservedSymbols.insert(GUID);
1101
1102   // Collect the import/export lists for all modules from the call-graph in the
1103   // combined index.
1104   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
1105   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
1106   ComputeCrossModuleImport(*Index, ModuleToDefinedGVSummaries, ImportLists,
1107                            ExportLists);
1108
1109   // We use a std::map here to be able to have a defined ordering when
1110   // producing a hash for the cache entry.
1111   // FIXME: we should be able to compute the caching hash for the entry based
1112   // on the index, and nuke this map.
1113   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
1114
1115   DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
1116   computePrevailingCopies(*Index, PrevailingCopy);
1117
1118   // Resolve prevailing symbols, this has to be computed early because it
1119   // impacts the caching.
1120   resolvePrevailingInIndex(*Index, ResolvedODR, GUIDPreservedSymbols,
1121                            PrevailingCopy);
1122
1123   // Use global summary-based analysis to identify symbols that can be
1124   // internalized (because they aren't exported or preserved as per callback).
1125   // Changes are made in the index, consumed in the ThinLTO backends.
1126   updateIndexWPDForExports(*Index,
1127                            IsExported(ExportLists, GUIDPreservedSymbols),
1128                            LocalWPDTargetsMap);
1129   thinLTOInternalizeAndPromoteInIndex(
1130       *Index, IsExported(ExportLists, GUIDPreservedSymbols),
1131       IsPrevailing(PrevailingCopy));
1132
1133   thinLTOPropagateFunctionAttrs(*Index, IsPrevailing(PrevailingCopy));
1134
1135   // Make sure that every module has an entry in the ExportLists, ImportList,
1136   // GVSummary and ResolvedODR maps to enable threaded access to these maps
1137   // below.
1138   for (auto &Module : Modules) {
1139     auto ModuleIdentifier = Module->getName();
1140     ExportLists[ModuleIdentifier];
1141     ImportLists[ModuleIdentifier];
1142     ResolvedODR[ModuleIdentifier];
1143     ModuleToDefinedGVSummaries[ModuleIdentifier];
1144   }
1145
1146   std::vector<BitcodeModule *> ModulesVec;
1147   ModulesVec.reserve(Modules.size());
1148   for (auto &Mod : Modules)
1149     ModulesVec.push_back(&Mod->getSingleBitcodeModule());
1150   std::vector<int> ModulesOrdering = lto::generateModulesOrdering(ModulesVec);
1151
1152   if (llvm::timeTraceProfilerEnabled())
1153     llvm::timeTraceProfilerEnd();
1154
1155   TimeTraceScopeExit.release();
1156
1157   // Parallel optimizer + codegen
1158   {
1159     ThreadPool Pool(heavyweight_hardware_concurrency(ThreadCount));
1160     for (auto IndexCount : ModulesOrdering) {
1161       auto &Mod = Modules[IndexCount];
1162       Pool.async([&](int count) {
1163         auto ModuleIdentifier = Mod->getName();
1164         auto &ExportList = ExportLists[ModuleIdentifier];
1165
1166         auto &DefinedGVSummaries = ModuleToDefinedGVSummaries[ModuleIdentifier];
1167
1168         // The module may be cached, this helps handling it.
1169         ModuleCacheEntry CacheEntry(CacheOptions.Path, *Index, ModuleIdentifier,
1170                                     ImportLists[ModuleIdentifier], ExportList,
1171                                     ResolvedODR[ModuleIdentifier],
1172                                     DefinedGVSummaries, OptLevel, Freestanding,
1173                                     TMBuilder);
1174         auto CacheEntryPath = CacheEntry.getEntryPath();
1175
1176         {
1177           auto ErrOrBuffer = CacheEntry.tryLoadingBuffer();
1178           LLVM_DEBUG(dbgs() << "Cache " << (ErrOrBuffer ? "hit" : "miss")
1179                             << " '" << CacheEntryPath << "' for buffer "
1180                             << count << " " << ModuleIdentifier << "\n");
1181
1182           if (ErrOrBuffer) {
1183             // Cache Hit!
1184             if (SavedObjectsDirectoryPath.empty())
1185               ProducedBinaries[count] = std::move(ErrOrBuffer.get());
1186             else
1187               ProducedBinaryFiles[count] = writeGeneratedObject(
1188                   count, CacheEntryPath, *ErrOrBuffer.get());
1189             return;
1190           }
1191         }
1192
1193         LLVMContext Context;
1194         Context.setDiscardValueNames(LTODiscardValueNames);
1195         Context.enableDebugTypeODRUniquing();
1196         auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
1197             Context, RemarksFilename, RemarksPasses, RemarksFormat,
1198             RemarksWithHotness, RemarksHotnessThreshold, count);
1199         if (!DiagFileOrErr) {
1200           errs() << "Error: " << toString(DiagFileOrErr.takeError()) << "\n";
1201           report_fatal_error("ThinLTO: Can't get an output file for the "
1202                              "remarks");
1203         }
1204
1205         // Parse module now
1206         auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
1207                                              /*IsImporting*/ false);
1208
1209         // Save temps: original file.
1210         saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc");
1211
1212         auto &ImportList = ImportLists[ModuleIdentifier];
1213         // Run the main process now, and generates a binary
1214         auto OutputBuffer = ProcessThinLTOModule(
1215             *TheModule, *Index, ModuleMap, *TMBuilder.create(), ImportList,
1216             ExportList, GUIDPreservedSymbols,
1217             ModuleToDefinedGVSummaries[ModuleIdentifier], CacheOptions,
1218             DisableCodeGen, SaveTempsDir, Freestanding, OptLevel, count,
1219             UseNewPM, DebugPassManager);
1220
1221         // Commit to the cache (if enabled)
1222         CacheEntry.write(*OutputBuffer);
1223
1224         if (SavedObjectsDirectoryPath.empty()) {
1225           // We need to generated a memory buffer for the linker.
1226           if (!CacheEntryPath.empty()) {
1227             // When cache is enabled, reload from the cache if possible.
1228             // Releasing the buffer from the heap and reloading it from the
1229             // cache file with mmap helps us to lower memory pressure.
1230             // The freed memory can be used for the next input file.
1231             // The final binary link will read from the VFS cache (hopefully!)
1232             // or from disk (if the memory pressure was too high).
1233             auto ReloadedBufferOrErr = CacheEntry.tryLoadingBuffer();
1234             if (auto EC = ReloadedBufferOrErr.getError()) {
1235               // On error, keep the preexisting buffer and print a diagnostic.
1236               errs() << "remark: can't reload cached file '" << CacheEntryPath
1237                      << "': " << EC.message() << "\n";
1238             } else {
1239               OutputBuffer = std::move(*ReloadedBufferOrErr);
1240             }
1241           }
1242           ProducedBinaries[count] = std::move(OutputBuffer);
1243           return;
1244         }
1245         ProducedBinaryFiles[count] = writeGeneratedObject(
1246             count, CacheEntryPath, *OutputBuffer);
1247       }, IndexCount);
1248     }
1249   }
1250
1251   pruneCache(CacheOptions.Path, CacheOptions.Policy);
1252
1253   // If statistics were requested, print them out now.
1254   if (llvm::AreStatisticsEnabled())
1255     llvm::PrintStatistics();
1256   reportAndResetTimings();
1257 }