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