lib/LTO/LTOCodeGenerator.cpp

   1 //===-LTOCodeGenerator.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 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/LTOCodeGenerator.h"
  15
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/ADT/StringExtras.h"
  18 #include "llvm/Analysis/Passes.h"
  19 #include "llvm/Analysis/TargetLibraryInfo.h"
  20 #include "llvm/Analysis/TargetTransformInfo.h"
  21 #include "llvm/Bitcode/BitcodeWriter.h"
  22 #include "llvm/CodeGen/ParallelCG.h"
  23 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  24 #include "llvm/Config/config.h"
  25 #include "llvm/IR/Constants.h"
  26 #include "llvm/IR/DataLayout.h"
  27 #include "llvm/IR/DebugInfo.h"
  28 #include "llvm/IR/DerivedTypes.h"
  29 #include "llvm/IR/DiagnosticInfo.h"
  30 #include "llvm/IR/DiagnosticPrinter.h"
  31 #include "llvm/IR/LLVMContext.h"
  32 #include "llvm/IR/LegacyPassManager.h"
  33 #include "llvm/IR/Mangler.h"
  34 #include "llvm/IR/Module.h"
  35 #include "llvm/IR/PassTimingInfo.h"
  36 #include "llvm/IR/RemarkStreamer.h"
  37 #include "llvm/IR/Verifier.h"
  38 #include "llvm/InitializePasses.h"
  39 #include "llvm/LTO/LTO.h"
  40 #include "llvm/LTO/legacy/LTOModule.h"
  41 #include "llvm/LTO/legacy/UpdateCompilerUsed.h"
  42 #include "llvm/Linker/Linker.h"
  43 #include "llvm/MC/MCAsmInfo.h"
  44 #include "llvm/MC/MCContext.h"
  45 #include "llvm/MC/SubtargetFeature.h"
  46 #include "llvm/Support/CommandLine.h"
  47 #include "llvm/Support/FileSystem.h"
  48 #include "llvm/Support/Host.h"
  49 #include "llvm/Support/MemoryBuffer.h"
  50 #include "llvm/Support/Signals.h"
  51 #include "llvm/Support/TargetRegistry.h"
  52 #include "llvm/Support/TargetSelect.h"
  53 #include "llvm/Support/ToolOutputFile.h"
  54 #include "llvm/Support/YAMLTraits.h"
  55 #include "llvm/Support/raw_ostream.h"
  56 #include "llvm/Target/TargetOptions.h"
  57 #include "llvm/Transforms/IPO.h"
  58 #include "llvm/Transforms/IPO/Internalize.h"
  59 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
  60 #include "llvm/Transforms/ObjCARC.h"
  61 #include "llvm/Transforms/Utils/ModuleUtils.h"
  62 #include <system_error>
  63 using namespace llvm;
  64
  65 const char* LTOCodeGenerator::getVersionString() {
  66 #ifdef LLVM_VERSION_INFO
  67   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
  68 #else
  69   return PACKAGE_NAME " version " PACKAGE_VERSION;
  70 #endif
  71 }
  72
  73 namespace llvm {
  74 cl::opt<bool> LTODiscardValueNames(
  75     "lto-discard-value-names",
  76     cl::desc("Strip names from Value during LTO (other than GlobalValue)."),
  77 #ifdef NDEBUG
  78     cl::init(true),
  79 #else
  80     cl::init(false),
  81 #endif
  82     cl::Hidden);
  83
  84 cl::opt<bool> RemarksWithHotness(
  85     "lto-pass-remarks-with-hotness",
  86     cl::desc("With PGO, include profile count in optimization remarks"),
  87     cl::Hidden);
  88
  89 cl::opt<std::string>
  90     RemarksFilename("lto-pass-remarks-output",
  91                     cl::desc("Output filename for pass remarks"),
  92                     cl::value_desc("filename"));
  93
  94 cl::opt<std::string>
  95     RemarksPasses("lto-pass-remarks-filter",
  96                   cl::desc("Only record optimization remarks from passes whose "
  97                            "names match the given regular expression"),
  98                   cl::value_desc("regex"));
  99
 100 cl::opt<std::string> RemarksFormat(
 101     "lto-pass-remarks-format",
 102     cl::desc("The format used for serializing remarks (default: YAML)"),
 103     cl::value_desc("format"), cl::init("yaml"));
 104
 105 cl::opt<std::string> LTOStatsFile(
 106     "lto-stats-file",
 107     cl::desc("Save statistics to the specified file"),
 108     cl::Hidden);
 109 }
 110
 111 LTOCodeGenerator::LTOCodeGenerator(LLVMContext &Context)
 112     : Context(Context), MergedModule(new Module("ld-temp.o", Context)),
 113       TheLinker(new Linker(*MergedModule)) {
 114   Context.setDiscardValueNames(LTODiscardValueNames);
 115   Context.enableDebugTypeODRUniquing();
 116   initializeLTOPasses();
 117 }
 118
 119 LTOCodeGenerator::~LTOCodeGenerator() {}
 120
 121 // Initialize LTO passes. Please keep this function in sync with
 122 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
 123 // passes are initialized.
 124 void LTOCodeGenerator::initializeLTOPasses() {
 125   PassRegistry &R = *PassRegistry::getPassRegistry();
 126
 127   initializeInternalizeLegacyPassPass(R);
 128   initializeIPSCCPLegacyPassPass(R);
 129   initializeGlobalOptLegacyPassPass(R);
 130   initializeConstantMergeLegacyPassPass(R);
 131   initializeDAHPass(R);
 132   initializeInstructionCombiningPassPass(R);
 133   initializeSimpleInlinerPass(R);
 134   initializePruneEHPass(R);
 135   initializeGlobalDCELegacyPassPass(R);
 136   initializeArgPromotionPass(R);
 137   initializeJumpThreadingPass(R);
 138   initializeSROALegacyPassPass(R);
 139   initializeAttributorLegacyPassPass(R);
 140   initializePostOrderFunctionAttrsLegacyPassPass(R);
 141   initializeReversePostOrderFunctionAttrsLegacyPassPass(R);
 142   initializeGlobalsAAWrapperPassPass(R);
 143   initializeLegacyLICMPassPass(R);
 144   initializeMergedLoadStoreMotionLegacyPassPass(R);
 145   initializeGVNLegacyPassPass(R);
 146   initializeMemCpyOptLegacyPassPass(R);
 147   initializeDCELegacyPassPass(R);
 148   initializeCFGSimplifyPassPass(R);
 149 }
 150
 151 void LTOCodeGenerator::setAsmUndefinedRefs(LTOModule *Mod) {
 152   const std::vector<StringRef> &undefs = Mod->getAsmUndefinedRefs();
 153   for (int i = 0, e = undefs.size(); i != e; ++i)
 154     AsmUndefinedRefs[undefs[i]] = 1;
 155 }
 156
 157 bool LTOCodeGenerator::addModule(LTOModule *Mod) {
 158   assert(&Mod->getModule().getContext() == &Context &&
 159          "Expected module in same context");
 160
 161   bool ret = TheLinker->linkInModule(Mod->takeModule());
 162   setAsmUndefinedRefs(Mod);
 163
 164   // We've just changed the input, so let's make sure we verify it.
 165   HasVerifiedInput = false;
 166
 167   return !ret;
 168 }
 169
 170 void LTOCodeGenerator::setModule(std::unique_ptr<LTOModule> Mod) {
 171   assert(&Mod->getModule().getContext() == &Context &&
 172          "Expected module in same context");
 173
 174   AsmUndefinedRefs.clear();
 175
 176   MergedModule = Mod->takeModule();
 177   TheLinker = std::make_unique<Linker>(*MergedModule);
 178   setAsmUndefinedRefs(&*Mod);
 179
 180   // We've just changed the input, so let's make sure we verify it.
 181   HasVerifiedInput = false;
 182 }
 183
 184 void LTOCodeGenerator::setTargetOptions(const TargetOptions &Options) {
 185   this->Options = Options;
 186 }
 187
 188 void LTOCodeGenerator::setDebugInfo(lto_debug_model Debug) {
 189   switch (Debug) {
 190   case LTO_DEBUG_MODEL_NONE:
 191     EmitDwarfDebugInfo = false;
 192     return;
 193
 194   case LTO_DEBUG_MODEL_DWARF:
 195     EmitDwarfDebugInfo = true;
 196     return;
 197   }
 198   llvm_unreachable("Unknown debug format!");
 199 }
 200
 201 void LTOCodeGenerator::setOptLevel(unsigned Level) {
 202   OptLevel = Level;
 203   switch (OptLevel) {
 204   case 0:
 205     CGOptLevel = CodeGenOpt::None;
 206     return;
 207   case 1:
 208     CGOptLevel = CodeGenOpt::Less;
 209     return;
 210   case 2:
 211     CGOptLevel = CodeGenOpt::Default;
 212     return;
 213   case 3:
 214     CGOptLevel = CodeGenOpt::Aggressive;
 215     return;
 216   }
 217   llvm_unreachable("Unknown optimization level!");
 218 }
 219
 220 bool LTOCodeGenerator::writeMergedModules(StringRef Path) {
 221   if (!determineTarget())
 222     return false;
 223
 224   // We always run the verifier once on the merged module.
 225   verifyMergedModuleOnce();
 226
 227   // mark which symbols can not be internalized
 228   applyScopeRestrictions();
 229
 230   // create output file
 231   std::error_code EC;
 232   ToolOutputFile Out(Path, EC, sys::fs::OF_None);
 233   if (EC) {
 234     std::string ErrMsg = "could not open bitcode file for writing: ";
 235     ErrMsg += Path.str() + ": " + EC.message();
 236     emitError(ErrMsg);
 237     return false;
 238   }
 239
 240   // write bitcode to it
 241   WriteBitcodeToFile(*MergedModule, Out.os(), ShouldEmbedUselists);
 242   Out.os().close();
 243
 244   if (Out.os().has_error()) {
 245     std::string ErrMsg = "could not write bitcode file: ";
 246     ErrMsg += Path.str() + ": " + Out.os().error().message();
 247     emitError(ErrMsg);
 248     Out.os().clear_error();
 249     return false;
 250   }
 251
 252   Out.keep();
 253   return true;
 254 }
 255
 256 bool LTOCodeGenerator::compileOptimizedToFile(const char **Name) {
 257   // make unique temp output file to put generated code
 258   SmallString<128> Filename;
 259   int FD;
 260
 261   StringRef Extension
 262       (FileType == TargetMachine::CGFT_AssemblyFile ? "s" : "o");
 263
 264   std::error_code EC =
 265       sys::fs::createTemporaryFile("lto-llvm", Extension, FD, Filename);
 266   if (EC) {
 267     emitError(EC.message());
 268     return false;
 269   }
 270
 271   // generate object file
 272   ToolOutputFile objFile(Filename, FD);
 273
 274   bool genResult = compileOptimized(&objFile.os());
 275   objFile.os().close();
 276   if (objFile.os().has_error()) {
 277     emitError((Twine("could not write object file: ") + Filename + ": " +
 278                objFile.os().error().message())
 279                   .str());
 280     objFile.os().clear_error();
 281     sys::fs::remove(Twine(Filename));
 282     return false;
 283   }
 284
 285   objFile.keep();
 286   if (!genResult) {
 287     sys::fs::remove(Twine(Filename));
 288     return false;
 289   }
 290
 291   NativeObjectPath = Filename.c_str();
 292   *Name = NativeObjectPath.c_str();
 293   return true;
 294 }
 295
 296 std::unique_ptr<MemoryBuffer>
 297 LTOCodeGenerator::compileOptimized() {
 298   const char *name;
 299   if (!compileOptimizedToFile(&name))
 300     return nullptr;
 301
 302   // read .o file into memory buffer
 303   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
 304       MemoryBuffer::getFile(name, -1, false);
 305   if (std::error_code EC = BufferOrErr.getError()) {
 306     emitError(EC.message());
 307     sys::fs::remove(NativeObjectPath);
 308     return nullptr;
 309   }
 310
 311   // remove temp files
 312   sys::fs::remove(NativeObjectPath);
 313
 314   return std::move(*BufferOrErr);
 315 }
 316
 317 bool LTOCodeGenerator::compile_to_file(const char **Name, bool DisableVerify,
 318                                        bool DisableInline,
 319                                        bool DisableGVNLoadPRE,
 320                                        bool DisableVectorization) {
 321   if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
 322                 DisableVectorization))
 323     return false;
 324
 325   return compileOptimizedToFile(Name);
 326 }
 327
 328 std::unique_ptr<MemoryBuffer>
 329 LTOCodeGenerator::compile(bool DisableVerify, bool DisableInline,
 330                           bool DisableGVNLoadPRE, bool DisableVectorization) {
 331   if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
 332                 DisableVectorization))
 333     return nullptr;
 334
 335   return compileOptimized();
 336 }
 337
 338 bool LTOCodeGenerator::determineTarget() {
 339   if (TargetMach)
 340     return true;
 341
 342   TripleStr = MergedModule->getTargetTriple();
 343   if (TripleStr.empty()) {
 344     TripleStr = sys::getDefaultTargetTriple();
 345     MergedModule->setTargetTriple(TripleStr);
 346   }
 347   llvm::Triple Triple(TripleStr);
 348
 349   // create target machine from info for merged modules
 350   std::string ErrMsg;
 351   MArch = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
 352   if (!MArch) {
 353     emitError(ErrMsg);
 354     return false;
 355   }
 356
 357   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
 358   // the default set of features.
 359   SubtargetFeatures Features(MAttr);
 360   Features.getDefaultSubtargetFeatures(Triple);
 361   FeatureStr = Features.getString();
 362   // Set a default CPU for Darwin triples.
 363   if (MCpu.empty() && Triple.isOSDarwin()) {
 364     if (Triple.getArch() == llvm::Triple::x86_64)
 365       MCpu = "core2";
 366     else if (Triple.getArch() == llvm::Triple::x86)
 367       MCpu = "yonah";
 368     else if (Triple.getArch() == llvm::Triple::aarch64 ||
 369              Triple.getArch() == llvm::Triple::aarch64_32)
 370       MCpu = "cyclone";
 371   }
 372
 373   TargetMach = createTargetMachine();
 374   return true;
 375 }
 376
 377 std::unique_ptr<TargetMachine> LTOCodeGenerator::createTargetMachine() {
 378   return std::unique_ptr<TargetMachine>(MArch->createTargetMachine(
 379       TripleStr, MCpu, FeatureStr, Options, RelocModel, None, CGOptLevel));
 380 }
 381
 382 // If a linkonce global is present in the MustPreserveSymbols, we need to make
 383 // sure we honor this. To force the compiler to not drop it, we add it to the
 384 // "llvm.compiler.used" global.
 385 void LTOCodeGenerator::preserveDiscardableGVs(
 386     Module &TheModule,
 387     llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV) {
 388   std::vector<GlobalValue *> Used;
 389   auto mayPreserveGlobal = [&](GlobalValue &GV) {
 390     if (!GV.isDiscardableIfUnused() || GV.isDeclaration() ||
 391         !mustPreserveGV(GV))
 392       return;
 393     if (GV.hasAvailableExternallyLinkage())
 394       return emitWarning(
 395           (Twine("Linker asked to preserve available_externally global: '") +
 396            GV.getName() + "'").str());
 397     if (GV.hasInternalLinkage())
 398       return emitWarning((Twine("Linker asked to preserve internal global: '") +
 399                    GV.getName() + "'").str());
 400     Used.push_back(&GV);
 401   };
 402   for (auto &GV : TheModule)
 403     mayPreserveGlobal(GV);
 404   for (auto &GV : TheModule.globals())
 405     mayPreserveGlobal(GV);
 406   for (auto &GV : TheModule.aliases())
 407     mayPreserveGlobal(GV);
 408
 409   if (Used.empty())
 410     return;
 411
 412   appendToCompilerUsed(TheModule, Used);
 413 }
 414
 415 void LTOCodeGenerator::applyScopeRestrictions() {
 416   if (ScopeRestrictionsDone)
 417     return;
 418
 419   // Declare a callback for the internalize pass that will ask for every
 420   // candidate GlobalValue if it can be internalized or not.
 421   Mangler Mang;
 422   SmallString<64> MangledName;
 423   auto mustPreserveGV = [&](const GlobalValue &GV) -> bool {
 424     // Unnamed globals can't be mangled, but they can't be preserved either.
 425     if (!GV.hasName())
 426       return false;
 427
 428     // Need to mangle the GV as the "MustPreserveSymbols" StringSet is filled
 429     // with the linker supplied name, which on Darwin includes a leading
 430     // underscore.
 431     MangledName.clear();
 432     MangledName.reserve(GV.getName().size() + 1);
 433     Mang.getNameWithPrefix(MangledName, &GV, /*CannotUsePrivateLabel=*/false);
 434     return MustPreserveSymbols.count(MangledName);
 435   };
 436
 437   // Preserve linkonce value on linker request
 438   preserveDiscardableGVs(*MergedModule, mustPreserveGV);
 439
 440   if (!ShouldInternalize)
 441     return;
 442
 443   if (ShouldRestoreGlobalsLinkage) {
 444     // Record the linkage type of non-local symbols so they can be restored
 445     // prior
 446     // to module splitting.
 447     auto RecordLinkage = [&](const GlobalValue &GV) {
 448       if (!GV.hasAvailableExternallyLinkage() && !GV.hasLocalLinkage() &&
 449           GV.hasName())
 450         ExternalSymbols.insert(std::make_pair(GV.getName(), GV.getLinkage()));
 451     };
 452     for (auto &GV : *MergedModule)
 453       RecordLinkage(GV);
 454     for (auto &GV : MergedModule->globals())
 455       RecordLinkage(GV);
 456     for (auto &GV : MergedModule->aliases())
 457       RecordLinkage(GV);
 458   }
 459
 460   // Update the llvm.compiler_used globals to force preserving libcalls and
 461   // symbols referenced from asm
 462   updateCompilerUsed(*MergedModule, *TargetMach, AsmUndefinedRefs);
 463
 464   internalizeModule(*MergedModule, mustPreserveGV);
 465
 466   ScopeRestrictionsDone = true;
 467 }
 468
 469 /// Restore original linkage for symbols that may have been internalized
 470 void LTOCodeGenerator::restoreLinkageForExternals() {
 471   if (!ShouldInternalize || !ShouldRestoreGlobalsLinkage)
 472     return;
 473
 474   assert(ScopeRestrictionsDone &&
 475          "Cannot externalize without internalization!");
 476
 477   if (ExternalSymbols.empty())
 478     return;
 479
 480   auto externalize = [this](GlobalValue &GV) {
 481     if (!GV.hasLocalLinkage() || !GV.hasName())
 482       return;
 483
 484     auto I = ExternalSymbols.find(GV.getName());
 485     if (I == ExternalSymbols.end())
 486       return;
 487
 488     GV.setLinkage(I->second);
 489   };
 490
 491   llvm::for_each(MergedModule->functions(), externalize);
 492   llvm::for_each(MergedModule->globals(), externalize);
 493   llvm::for_each(MergedModule->aliases(), externalize);
 494 }
 495
 496 void LTOCodeGenerator::verifyMergedModuleOnce() {
 497   // Only run on the first call.
 498   if (HasVerifiedInput)
 499     return;
 500   HasVerifiedInput = true;
 501
 502   bool BrokenDebugInfo = false;
 503   if (verifyModule(*MergedModule, &dbgs(), &BrokenDebugInfo))
 504     report_fatal_error("Broken module found, compilation aborted!");
 505   if (BrokenDebugInfo) {
 506     emitWarning("Invalid debug info found, debug info will be stripped");
 507     StripDebugInfo(*MergedModule);
 508   }
 509 }
 510
 511 void LTOCodeGenerator::finishOptimizationRemarks() {
 512   if (DiagnosticOutputFile) {
 513     DiagnosticOutputFile->keep();
 514     // FIXME: LTOCodeGenerator dtor is not invoked on Darwin
 515     DiagnosticOutputFile->os().flush();
 516   }
 517 }
 518
 519 /// Optimize merged modules using various IPO passes
 520 bool LTOCodeGenerator::optimize(bool DisableVerify, bool DisableInline,
 521                                 bool DisableGVNLoadPRE,
 522                                 bool DisableVectorization) {
 523   if (!this->determineTarget())
 524     return false;
 525
 526   auto DiagFileOrErr =
 527       lto::setupOptimizationRemarks(Context, RemarksFilename, RemarksPasses,
 528                                     RemarksFormat, RemarksWithHotness);
 529   if (!DiagFileOrErr) {
 530     errs() << "Error: " << toString(DiagFileOrErr.takeError()) << "\n";
 531     report_fatal_error("Can't get an output file for the remarks");
 532   }
 533   DiagnosticOutputFile = std::move(*DiagFileOrErr);
 534
 535   // Setup output file to emit statistics.
 536   auto StatsFileOrErr = lto::setupStatsFile(LTOStatsFile);
 537   if (!StatsFileOrErr) {
 538     errs() << "Error: " << toString(StatsFileOrErr.takeError()) << "\n";
 539     report_fatal_error("Can't get an output file for the statistics");
 540   }
 541   StatsFile = std::move(StatsFileOrErr.get());
 542
 543   // We always run the verifier once on the merged module, the `DisableVerify`
 544   // parameter only applies to subsequent verify.
 545   verifyMergedModuleOnce();
 546
 547   // Mark which symbols can not be internalized
 548   this->applyScopeRestrictions();
 549
 550   // Instantiate the pass manager to organize the passes.
 551   legacy::PassManager passes;
 552
 553   // Add an appropriate DataLayout instance for this module...
 554   MergedModule->setDataLayout(TargetMach->createDataLayout());
 555
 556   passes.add(
 557       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
 558
 559   Triple TargetTriple(TargetMach->getTargetTriple());
 560   PassManagerBuilder PMB;
 561   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
 562   PMB.LoopVectorize = !DisableVectorization;
 563   PMB.SLPVectorize = !DisableVectorization;
 564   if (!DisableInline)
 565     PMB.Inliner = createFunctionInliningPass();
 566   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
 567   if (Freestanding)
 568     PMB.LibraryInfo->disableAllFunctions();
 569   PMB.OptLevel = OptLevel;
 570   PMB.VerifyInput = !DisableVerify;
 571   PMB.VerifyOutput = !DisableVerify;
 572
 573   PMB.populateLTOPassManager(passes);
 574
 575   // Run our queue of passes all at once now, efficiently.
 576   passes.run(*MergedModule);
 577
 578   return true;
 579 }
 580
 581 bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out) {
 582   if (!this->determineTarget())
 583     return false;
 584
 585   // We always run the verifier once on the merged module.  If it has already
 586   // been called in optimize(), this call will return early.
 587   verifyMergedModuleOnce();
 588
 589   legacy::PassManager preCodeGenPasses;
 590
 591   // If the bitcode files contain ARC code and were compiled with optimization,
 592   // the ObjCARCContractPass must be run, so do it unconditionally here.
 593   preCodeGenPasses.add(createObjCARCContractPass());
 594   preCodeGenPasses.run(*MergedModule);
 595
 596   // Re-externalize globals that may have been internalized to increase scope
 597   // for splitting
 598   restoreLinkageForExternals();
 599
 600   // Do code generation. We need to preserve the module in case the client calls
 601   // writeMergedModules() after compilation, but we only need to allow this at
 602   // parallelism level 1. This is achieved by having splitCodeGen return the
 603   // original module at parallelism level 1 which we then assign back to
 604   // MergedModule.
 605   MergedModule = splitCodeGen(std::move(MergedModule), Out, {},
 606                               [&]() { return createTargetMachine(); }, FileType,
 607                               ShouldRestoreGlobalsLinkage);
 608
 609   // If statistics were requested, save them to the specified file or
 610   // print them out after codegen.
 611   if (StatsFile)
 612     PrintStatisticsJSON(StatsFile->os());
 613   else if (AreStatisticsEnabled())
 614     PrintStatistics();
 615
 616   reportAndResetTimings();
 617
 618   finishOptimizationRemarks();
 619
 620   return true;
 621 }
 622
 623 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
 624 /// LTO problems.
 625 void LTOCodeGenerator::setCodeGenDebugOptions(StringRef Options) {
 626   for (std::pair<StringRef, StringRef> o = getToken(Options); !o.first.empty();
 627        o = getToken(o.second))
 628     CodegenOptions.push_back(o.first);
 629 }
 630
 631 void LTOCodeGenerator::parseCodeGenDebugOptions() {
 632   // if options were requested, set them
 633   if (!CodegenOptions.empty()) {
 634     // ParseCommandLineOptions() expects argv[0] to be program name.
 635     std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
 636     for (std::string &Arg : CodegenOptions)
 637       CodegenArgv.push_back(Arg.c_str());
 638     cl::ParseCommandLineOptions(CodegenArgv.size(), CodegenArgv.data());
 639   }
 640 }
 641
 642
 643 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI) {
 644   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
 645   lto_codegen_diagnostic_severity_t Severity;
 646   switch (DI.getSeverity()) {
 647   case DS_Error:
 648     Severity = LTO_DS_ERROR;
 649     break;
 650   case DS_Warning:
 651     Severity = LTO_DS_WARNING;
 652     break;
 653   case DS_Remark:
 654     Severity = LTO_DS_REMARK;
 655     break;
 656   case DS_Note:
 657     Severity = LTO_DS_NOTE;
 658     break;
 659   }
 660   // Create the string that will be reported to the external diagnostic handler.
 661   std::string MsgStorage;
 662   raw_string_ostream Stream(MsgStorage);
 663   DiagnosticPrinterRawOStream DP(Stream);
 664   DI.print(DP);
 665   Stream.flush();
 666
 667   // If this method has been called it means someone has set up an external
 668   // diagnostic handler. Assert on that.
 669   assert(DiagHandler && "Invalid diagnostic handler");
 670   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
 671 }
 672
 673 namespace {
 674 struct LTODiagnosticHandler : public DiagnosticHandler {
 675   LTOCodeGenerator *CodeGenerator;
 676   LTODiagnosticHandler(LTOCodeGenerator *CodeGenPtr)
 677       : CodeGenerator(CodeGenPtr) {}
 678   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 679     CodeGenerator->DiagnosticHandler(DI);
 680     return true;
 681   }
 682 };
 683 }
 684
 685 void
 686 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
 687                                        void *Ctxt) {
 688   this->DiagHandler = DiagHandler;
 689   this->DiagContext = Ctxt;
 690   if (!DiagHandler)
 691     return Context.setDiagnosticHandler(nullptr);
 692   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
 693   // diagnostic to the external DiagHandler.
 694   Context.setDiagnosticHandler(std::make_unique<LTODiagnosticHandler>(this),
 695                                true);
 696 }
 697
 698 namespace {
 699 class LTODiagnosticInfo : public DiagnosticInfo {
 700   const Twine &Msg;
 701 public:
 702   LTODiagnosticInfo(const Twine &DiagMsg, DiagnosticSeverity Severity=DS_Error)
 703       : DiagnosticInfo(DK_Linker, Severity), Msg(DiagMsg) {}
 704   void print(DiagnosticPrinter &DP) const override { DP << Msg; }
 705 };
 706 }
 707
 708 void LTOCodeGenerator::emitError(const std::string &ErrMsg) {
 709   if (DiagHandler)
 710     (*DiagHandler)(LTO_DS_ERROR, ErrMsg.c_str(), DiagContext);
 711   else
 712     Context.diagnose(LTODiagnosticInfo(ErrMsg));
 713 }
 714
 715 void LTOCodeGenerator::emitWarning(const std::string &ErrMsg) {
 716   if (DiagHandler)
 717     (*DiagHandler)(LTO_DS_WARNING, ErrMsg.c_str(), DiagContext);
 718   else
 719     Context.diagnose(LTODiagnosticInfo(ErrMsg, DS_Warning));
 720 }