lib/LTO/LTOCodeGenerator.cpp

   1 //===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the Link Time Optimization library. This library is
  11 // intended to be used by linker to optimize code at link time.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/LTO/legacy/LTOCodeGenerator.h"
  16
  17 #include "llvm/ADT/Statistic.h"
  18 #include "llvm/ADT/StringExtras.h"
  19 #include "llvm/Analysis/Passes.h"
  20 #include "llvm/Analysis/TargetLibraryInfo.h"
  21 #include "llvm/Analysis/TargetTransformInfo.h"
  22 #include "llvm/Bitcode/BitcodeWriter.h"
  23 #include "llvm/CodeGen/ParallelCG.h"
  24 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  25 #include "llvm/Config/config.h"
  26 #include "llvm/IR/Constants.h"
  27 #include "llvm/IR/DataLayout.h"
  28 #include "llvm/IR/DebugInfo.h"
  29 #include "llvm/IR/DerivedTypes.h"
  30 #include "llvm/IR/DiagnosticInfo.h"
  31 #include "llvm/IR/DiagnosticPrinter.h"
  32 #include "llvm/IR/LLVMContext.h"
  33 #include "llvm/IR/LegacyPassManager.h"
  34 #include "llvm/IR/Mangler.h"
  35 #include "llvm/IR/Module.h"
  36 #include "llvm/IR/PassTimingInfo.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<std::string>
  85     LTORemarksFilename("lto-pass-remarks-output",
  86                        cl::desc("Output filename for pass remarks"),
  87                        cl::value_desc("filename"));
  88
  89 cl::opt<bool> LTOPassRemarksWithHotness(
  90     "lto-pass-remarks-with-hotness",
  91     cl::desc("With PGO, include profile count in optimization remarks"),
  92     cl::Hidden);
  93 }
  94
  95 LTOCodeGenerator::LTOCodeGenerator(LLVMContext &Context)
  96     : Context(Context), MergedModule(new Module("ld-temp.o", Context)),
  97       TheLinker(new Linker(*MergedModule)) {
  98   Context.setDiscardValueNames(LTODiscardValueNames);
  99   Context.enableDebugTypeODRUniquing();
 100   initializeLTOPasses();
 101 }
 102
 103 LTOCodeGenerator::~LTOCodeGenerator() {}
 104
 105 // Initialize LTO passes. Please keep this function in sync with
 106 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
 107 // passes are initialized.
 108 void LTOCodeGenerator::initializeLTOPasses() {
 109   PassRegistry &R = *PassRegistry::getPassRegistry();
 110
 111   initializeInternalizeLegacyPassPass(R);
 112   initializeIPSCCPLegacyPassPass(R);
 113   initializeGlobalOptLegacyPassPass(R);
 114   initializeConstantMergeLegacyPassPass(R);
 115   initializeDAHPass(R);
 116   initializeInstructionCombiningPassPass(R);
 117   initializeSimpleInlinerPass(R);
 118   initializePruneEHPass(R);
 119   initializeGlobalDCELegacyPassPass(R);
 120   initializeArgPromotionPass(R);
 121   initializeJumpThreadingPass(R);
 122   initializeSROALegacyPassPass(R);
 123   initializePostOrderFunctionAttrsLegacyPassPass(R);
 124   initializeReversePostOrderFunctionAttrsLegacyPassPass(R);
 125   initializeGlobalsAAWrapperPassPass(R);
 126   initializeLegacyLICMPassPass(R);
 127   initializeMergedLoadStoreMotionLegacyPassPass(R);
 128   initializeGVNLegacyPassPass(R);
 129   initializeMemCpyOptLegacyPassPass(R);
 130   initializeDCELegacyPassPass(R);
 131   initializeCFGSimplifyPassPass(R);
 132 }
 133
 134 void LTOCodeGenerator::setAsmUndefinedRefs(LTOModule *Mod) {
 135   const std::vector<StringRef> &undefs = Mod->getAsmUndefinedRefs();
 136   for (int i = 0, e = undefs.size(); i != e; ++i)
 137     AsmUndefinedRefs[undefs[i]] = 1;
 138 }
 139
 140 bool LTOCodeGenerator::addModule(LTOModule *Mod) {
 141   assert(&Mod->getModule().getContext() == &Context &&
 142          "Expected module in same context");
 143
 144   bool ret = TheLinker->linkInModule(Mod->takeModule());
 145   setAsmUndefinedRefs(Mod);
 146
 147   // We've just changed the input, so let's make sure we verify it.
 148   HasVerifiedInput = false;
 149
 150   return !ret;
 151 }
 152
 153 void LTOCodeGenerator::setModule(std::unique_ptr<LTOModule> Mod) {
 154   assert(&Mod->getModule().getContext() == &Context &&
 155          "Expected module in same context");
 156
 157   AsmUndefinedRefs.clear();
 158
 159   MergedModule = Mod->takeModule();
 160   TheLinker = make_unique<Linker>(*MergedModule);
 161   setAsmUndefinedRefs(&*Mod);
 162
 163   // We've just changed the input, so let's make sure we verify it.
 164   HasVerifiedInput = false;
 165 }
 166
 167 void LTOCodeGenerator::setTargetOptions(const TargetOptions &Options) {
 168   this->Options = Options;
 169 }
 170
 171 void LTOCodeGenerator::setDebugInfo(lto_debug_model Debug) {
 172   switch (Debug) {
 173   case LTO_DEBUG_MODEL_NONE:
 174     EmitDwarfDebugInfo = false;
 175     return;
 176
 177   case LTO_DEBUG_MODEL_DWARF:
 178     EmitDwarfDebugInfo = true;
 179     return;
 180   }
 181   llvm_unreachable("Unknown debug format!");
 182 }
 183
 184 void LTOCodeGenerator::setOptLevel(unsigned Level) {
 185   OptLevel = Level;
 186   switch (OptLevel) {
 187   case 0:
 188     CGOptLevel = CodeGenOpt::None;
 189     return;
 190   case 1:
 191     CGOptLevel = CodeGenOpt::Less;
 192     return;
 193   case 2:
 194     CGOptLevel = CodeGenOpt::Default;
 195     return;
 196   case 3:
 197     CGOptLevel = CodeGenOpt::Aggressive;
 198     return;
 199   }
 200   llvm_unreachable("Unknown optimization level!");
 201 }
 202
 203 bool LTOCodeGenerator::writeMergedModules(StringRef Path) {
 204   if (!determineTarget())
 205     return false;
 206
 207   // We always run the verifier once on the merged module.
 208   verifyMergedModuleOnce();
 209
 210   // mark which symbols can not be internalized
 211   applyScopeRestrictions();
 212
 213   // create output file
 214   std::error_code EC;
 215   ToolOutputFile Out(Path, EC, sys::fs::F_None);
 216   if (EC) {
 217     std::string ErrMsg = "could not open bitcode file for writing: ";
 218     ErrMsg += Path.str() + ": " + EC.message();
 219     emitError(ErrMsg);
 220     return false;
 221   }
 222
 223   // write bitcode to it
 224   WriteBitcodeToFile(*MergedModule, Out.os(), ShouldEmbedUselists);
 225   Out.os().close();
 226
 227   if (Out.os().has_error()) {
 228     std::string ErrMsg = "could not write bitcode file: ";
 229     ErrMsg += Path.str() + ": " + Out.os().error().message();
 230     emitError(ErrMsg);
 231     Out.os().clear_error();
 232     return false;
 233   }
 234
 235   Out.keep();
 236   return true;
 237 }
 238
 239 bool LTOCodeGenerator::compileOptimizedToFile(const char **Name) {
 240   // make unique temp output file to put generated code
 241   SmallString<128> Filename;
 242   int FD;
 243
 244   StringRef Extension
 245       (FileType == TargetMachine::CGFT_AssemblyFile ? "s" : "o");
 246
 247   std::error_code EC =
 248       sys::fs::createTemporaryFile("lto-llvm", Extension, FD, Filename);
 249   if (EC) {
 250     emitError(EC.message());
 251     return false;
 252   }
 253
 254   // generate object file
 255   ToolOutputFile objFile(Filename, FD);
 256
 257   bool genResult = compileOptimized(&objFile.os());
 258   objFile.os().close();
 259   if (objFile.os().has_error()) {
 260     emitError((Twine("could not write object file: ") + Filename + ": " +
 261                objFile.os().error().message())
 262                   .str());
 263     objFile.os().clear_error();
 264     sys::fs::remove(Twine(Filename));
 265     return false;
 266   }
 267
 268   objFile.keep();
 269   if (!genResult) {
 270     sys::fs::remove(Twine(Filename));
 271     return false;
 272   }
 273
 274   NativeObjectPath = Filename.c_str();
 275   *Name = NativeObjectPath.c_str();
 276   return true;
 277 }
 278
 279 std::unique_ptr<MemoryBuffer>
 280 LTOCodeGenerator::compileOptimized() {
 281   const char *name;
 282   if (!compileOptimizedToFile(&name))
 283     return nullptr;
 284
 285   // read .o file into memory buffer
 286   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
 287       MemoryBuffer::getFile(name, -1, false);
 288   if (std::error_code EC = BufferOrErr.getError()) {
 289     emitError(EC.message());
 290     sys::fs::remove(NativeObjectPath);
 291     return nullptr;
 292   }
 293
 294   // remove temp files
 295   sys::fs::remove(NativeObjectPath);
 296
 297   return std::move(*BufferOrErr);
 298 }
 299
 300 bool LTOCodeGenerator::compile_to_file(const char **Name, bool DisableVerify,
 301                                        bool DisableInline,
 302                                        bool DisableGVNLoadPRE,
 303                                        bool DisableVectorization) {
 304   if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
 305                 DisableVectorization))
 306     return false;
 307
 308   return compileOptimizedToFile(Name);
 309 }
 310
 311 std::unique_ptr<MemoryBuffer>
 312 LTOCodeGenerator::compile(bool DisableVerify, bool DisableInline,
 313                           bool DisableGVNLoadPRE, bool DisableVectorization) {
 314   if (!optimize(DisableVerify, DisableInline, DisableGVNLoadPRE,
 315                 DisableVectorization))
 316     return nullptr;
 317
 318   return compileOptimized();
 319 }
 320
 321 bool LTOCodeGenerator::determineTarget() {
 322   if (TargetMach)
 323     return true;
 324
 325   TripleStr = MergedModule->getTargetTriple();
 326   if (TripleStr.empty()) {
 327     TripleStr = sys::getDefaultTargetTriple();
 328     MergedModule->setTargetTriple(TripleStr);
 329   }
 330   llvm::Triple Triple(TripleStr);
 331
 332   // create target machine from info for merged modules
 333   std::string ErrMsg;
 334   MArch = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
 335   if (!MArch) {
 336     emitError(ErrMsg);
 337     return false;
 338   }
 339
 340   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
 341   // the default set of features.
 342   SubtargetFeatures Features(MAttr);
 343   Features.getDefaultSubtargetFeatures(Triple);
 344   FeatureStr = Features.getString();
 345   // Set a default CPU for Darwin triples.
 346   if (MCpu.empty() && Triple.isOSDarwin()) {
 347     if (Triple.getArch() == llvm::Triple::x86_64)
 348       MCpu = "core2";
 349     else if (Triple.getArch() == llvm::Triple::x86)
 350       MCpu = "yonah";
 351     else if (Triple.getArch() == llvm::Triple::aarch64)
 352       MCpu = "cyclone";
 353   }
 354
 355   TargetMach = createTargetMachine();
 356   return true;
 357 }
 358
 359 std::unique_ptr<TargetMachine> LTOCodeGenerator::createTargetMachine() {
 360   return std::unique_ptr<TargetMachine>(MArch->createTargetMachine(
 361       TripleStr, MCpu, FeatureStr, Options, RelocModel, None, CGOptLevel));
 362 }
 363
 364 // If a linkonce global is present in the MustPreserveSymbols, we need to make
 365 // sure we honor this. To force the compiler to not drop it, we add it to the
 366 // "llvm.compiler.used" global.
 367 void LTOCodeGenerator::preserveDiscardableGVs(
 368     Module &TheModule,
 369     llvm::function_ref<bool(const GlobalValue &)> mustPreserveGV) {
 370   std::vector<GlobalValue *> Used;
 371   auto mayPreserveGlobal = [&](GlobalValue &GV) {
 372     if (!GV.isDiscardableIfUnused() || GV.isDeclaration() ||
 373         !mustPreserveGV(GV))
 374       return;
 375     if (GV.hasAvailableExternallyLinkage())
 376       return emitWarning(
 377           (Twine("Linker asked to preserve available_externally global: '") +
 378            GV.getName() + "'").str());
 379     if (GV.hasInternalLinkage())
 380       return emitWarning((Twine("Linker asked to preserve internal global: '") +
 381                    GV.getName() + "'").str());
 382     Used.push_back(&GV);
 383   };
 384   for (auto &GV : TheModule)
 385     mayPreserveGlobal(GV);
 386   for (auto &GV : TheModule.globals())
 387     mayPreserveGlobal(GV);
 388   for (auto &GV : TheModule.aliases())
 389     mayPreserveGlobal(GV);
 390
 391   if (Used.empty())
 392     return;
 393
 394   appendToCompilerUsed(TheModule, Used);
 395 }
 396
 397 void LTOCodeGenerator::applyScopeRestrictions() {
 398   if (ScopeRestrictionsDone)
 399     return;
 400
 401   // Declare a callback for the internalize pass that will ask for every
 402   // candidate GlobalValue if it can be internalized or not.
 403   Mangler Mang;
 404   SmallString<64> MangledName;
 405   auto mustPreserveGV = [&](const GlobalValue &GV) -> bool {
 406     // Unnamed globals can't be mangled, but they can't be preserved either.
 407     if (!GV.hasName())
 408       return false;
 409
 410     // Need to mangle the GV as the "MustPreserveSymbols" StringSet is filled
 411     // with the linker supplied name, which on Darwin includes a leading
 412     // underscore.
 413     MangledName.clear();
 414     MangledName.reserve(GV.getName().size() + 1);
 415     Mang.getNameWithPrefix(MangledName, &GV, /*CannotUsePrivateLabel=*/false);
 416     return MustPreserveSymbols.count(MangledName);
 417   };
 418
 419   // Preserve linkonce value on linker request
 420   preserveDiscardableGVs(*MergedModule, mustPreserveGV);
 421
 422   if (!ShouldInternalize)
 423     return;
 424
 425   if (ShouldRestoreGlobalsLinkage) {
 426     // Record the linkage type of non-local symbols so they can be restored
 427     // prior
 428     // to module splitting.
 429     auto RecordLinkage = [&](const GlobalValue &GV) {
 430       if (!GV.hasAvailableExternallyLinkage() && !GV.hasLocalLinkage() &&
 431           GV.hasName())
 432         ExternalSymbols.insert(std::make_pair(GV.getName(), GV.getLinkage()));
 433     };
 434     for (auto &GV : *MergedModule)
 435       RecordLinkage(GV);
 436     for (auto &GV : MergedModule->globals())
 437       RecordLinkage(GV);
 438     for (auto &GV : MergedModule->aliases())
 439       RecordLinkage(GV);
 440   }
 441
 442   // Update the llvm.compiler_used globals to force preserving libcalls and
 443   // symbols referenced from asm
 444   updateCompilerUsed(*MergedModule, *TargetMach, AsmUndefinedRefs);
 445
 446   internalizeModule(*MergedModule, mustPreserveGV);
 447
 448   ScopeRestrictionsDone = true;
 449 }
 450
 451 /// Restore original linkage for symbols that may have been internalized
 452 void LTOCodeGenerator::restoreLinkageForExternals() {
 453   if (!ShouldInternalize || !ShouldRestoreGlobalsLinkage)
 454     return;
 455
 456   assert(ScopeRestrictionsDone &&
 457          "Cannot externalize without internalization!");
 458
 459   if (ExternalSymbols.empty())
 460     return;
 461
 462   auto externalize = [this](GlobalValue &GV) {
 463     if (!GV.hasLocalLinkage() || !GV.hasName())
 464       return;
 465
 466     auto I = ExternalSymbols.find(GV.getName());
 467     if (I == ExternalSymbols.end())
 468       return;
 469
 470     GV.setLinkage(I->second);
 471   };
 472
 473   llvm::for_each(MergedModule->functions(), externalize);
 474   llvm::for_each(MergedModule->globals(), externalize);
 475   llvm::for_each(MergedModule->aliases(), externalize);
 476 }
 477
 478 void LTOCodeGenerator::verifyMergedModuleOnce() {
 479   // Only run on the first call.
 480   if (HasVerifiedInput)
 481     return;
 482   HasVerifiedInput = true;
 483
 484   bool BrokenDebugInfo = false;
 485   if (verifyModule(*MergedModule, &dbgs(), &BrokenDebugInfo))
 486     report_fatal_error("Broken module found, compilation aborted!");
 487   if (BrokenDebugInfo) {
 488     emitWarning("Invalid debug info found, debug info will be stripped");
 489     StripDebugInfo(*MergedModule);
 490   }
 491 }
 492
 493 void LTOCodeGenerator::finishOptimizationRemarks() {
 494   if (DiagnosticOutputFile) {
 495     DiagnosticOutputFile->keep();
 496     // FIXME: LTOCodeGenerator dtor is not invoked on Darwin
 497     DiagnosticOutputFile->os().flush();
 498   }
 499 }
 500
 501 /// Optimize merged modules using various IPO passes
 502 bool LTOCodeGenerator::optimize(bool DisableVerify, bool DisableInline,
 503                                 bool DisableGVNLoadPRE,
 504                                 bool DisableVectorization) {
 505   if (!this->determineTarget())
 506     return false;
 507
 508   auto DiagFileOrErr = lto::setupOptimizationRemarks(
 509       Context, LTORemarksFilename, LTOPassRemarksWithHotness);
 510   if (!DiagFileOrErr) {
 511     errs() << "Error: " << toString(DiagFileOrErr.takeError()) << "\n";
 512     report_fatal_error("Can't get an output file for the remarks");
 513   }
 514   DiagnosticOutputFile = std::move(*DiagFileOrErr);
 515
 516   // We always run the verifier once on the merged module, the `DisableVerify`
 517   // parameter only applies to subsequent verify.
 518   verifyMergedModuleOnce();
 519
 520   // Mark which symbols can not be internalized
 521   this->applyScopeRestrictions();
 522
 523   // Instantiate the pass manager to organize the passes.
 524   legacy::PassManager passes;
 525
 526   // Add an appropriate DataLayout instance for this module...
 527   MergedModule->setDataLayout(TargetMach->createDataLayout());
 528
 529   passes.add(
 530       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
 531
 532   Triple TargetTriple(TargetMach->getTargetTriple());
 533   PassManagerBuilder PMB;
 534   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
 535   PMB.LoopVectorize = !DisableVectorization;
 536   PMB.SLPVectorize = !DisableVectorization;
 537   if (!DisableInline)
 538     PMB.Inliner = createFunctionInliningPass();
 539   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
 540   if (Freestanding)
 541     PMB.LibraryInfo->disableAllFunctions();
 542   PMB.OptLevel = OptLevel;
 543   PMB.VerifyInput = !DisableVerify;
 544   PMB.VerifyOutput = !DisableVerify;
 545
 546   PMB.populateLTOPassManager(passes);
 547
 548   // Run our queue of passes all at once now, efficiently.
 549   passes.run(*MergedModule);
 550
 551   return true;
 552 }
 553
 554 bool LTOCodeGenerator::compileOptimized(ArrayRef<raw_pwrite_stream *> Out) {
 555   if (!this->determineTarget())
 556     return false;
 557
 558   // We always run the verifier once on the merged module.  If it has already
 559   // been called in optimize(), this call will return early.
 560   verifyMergedModuleOnce();
 561
 562   legacy::PassManager preCodeGenPasses;
 563
 564   // If the bitcode files contain ARC code and were compiled with optimization,
 565   // the ObjCARCContractPass must be run, so do it unconditionally here.
 566   preCodeGenPasses.add(createObjCARCContractPass());
 567   preCodeGenPasses.run(*MergedModule);
 568
 569   // Re-externalize globals that may have been internalized to increase scope
 570   // for splitting
 571   restoreLinkageForExternals();
 572
 573   // Do code generation. We need to preserve the module in case the client calls
 574   // writeMergedModules() after compilation, but we only need to allow this at
 575   // parallelism level 1. This is achieved by having splitCodeGen return the
 576   // original module at parallelism level 1 which we then assign back to
 577   // MergedModule.
 578   MergedModule = splitCodeGen(std::move(MergedModule), Out, {},
 579                               [&]() { return createTargetMachine(); }, FileType,
 580                               ShouldRestoreGlobalsLinkage);
 581
 582   // If statistics were requested, print them out after codegen.
 583   if (llvm::AreStatisticsEnabled())
 584     llvm::PrintStatistics();
 585   reportAndResetTimings();
 586
 587   finishOptimizationRemarks();
 588
 589   return true;
 590 }
 591
 592 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
 593 /// LTO problems.
 594 void LTOCodeGenerator::setCodeGenDebugOptions(StringRef Options) {
 595   for (std::pair<StringRef, StringRef> o = getToken(Options); !o.first.empty();
 596        o = getToken(o.second))
 597     CodegenOptions.push_back(o.first);
 598 }
 599
 600 void LTOCodeGenerator::parseCodeGenDebugOptions() {
 601   // if options were requested, set them
 602   if (!CodegenOptions.empty()) {
 603     // ParseCommandLineOptions() expects argv[0] to be program name.
 604     std::vector<const char *> CodegenArgv(1, "libLLVMLTO");
 605     for (std::string &Arg : CodegenOptions)
 606       CodegenArgv.push_back(Arg.c_str());
 607     cl::ParseCommandLineOptions(CodegenArgv.size(), CodegenArgv.data());
 608   }
 609 }
 610
 611
 612 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI) {
 613   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
 614   lto_codegen_diagnostic_severity_t Severity;
 615   switch (DI.getSeverity()) {
 616   case DS_Error:
 617     Severity = LTO_DS_ERROR;
 618     break;
 619   case DS_Warning:
 620     Severity = LTO_DS_WARNING;
 621     break;
 622   case DS_Remark:
 623     Severity = LTO_DS_REMARK;
 624     break;
 625   case DS_Note:
 626     Severity = LTO_DS_NOTE;
 627     break;
 628   }
 629   // Create the string that will be reported to the external diagnostic handler.
 630   std::string MsgStorage;
 631   raw_string_ostream Stream(MsgStorage);
 632   DiagnosticPrinterRawOStream DP(Stream);
 633   DI.print(DP);
 634   Stream.flush();
 635
 636   // If this method has been called it means someone has set up an external
 637   // diagnostic handler. Assert on that.
 638   assert(DiagHandler && "Invalid diagnostic handler");
 639   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
 640 }
 641
 642 namespace {
 643 struct LTODiagnosticHandler : public DiagnosticHandler {
 644   LTOCodeGenerator *CodeGenerator;
 645   LTODiagnosticHandler(LTOCodeGenerator *CodeGenPtr)
 646       : CodeGenerator(CodeGenPtr) {}
 647   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 648     CodeGenerator->DiagnosticHandler(DI);
 649     return true;
 650   }
 651 };
 652 }
 653
 654 void
 655 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
 656                                        void *Ctxt) {
 657   this->DiagHandler = DiagHandler;
 658   this->DiagContext = Ctxt;
 659   if (!DiagHandler)
 660     return Context.setDiagnosticHandler(nullptr);
 661   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
 662   // diagnostic to the external DiagHandler.
 663   Context.setDiagnosticHandler(llvm::make_unique<LTODiagnosticHandler>(this),
 664                                true);
 665 }
 666
 667 namespace {
 668 class LTODiagnosticInfo : public DiagnosticInfo {
 669   const Twine &Msg;
 670 public:
 671   LTODiagnosticInfo(const Twine &DiagMsg, DiagnosticSeverity Severity=DS_Error)
 672       : DiagnosticInfo(DK_Linker, Severity), Msg(DiagMsg) {}
 673   void print(DiagnosticPrinter &DP) const override { DP << Msg; }
 674 };
 675 }
 676
 677 void LTOCodeGenerator::emitError(const std::string &ErrMsg) {
 678   if (DiagHandler)
 679     (*DiagHandler)(LTO_DS_ERROR, ErrMsg.c_str(), DiagContext);
 680   else
 681     Context.diagnose(LTODiagnosticInfo(ErrMsg));
 682 }
 683
 684 void LTOCodeGenerator::emitWarning(const std::string &ErrMsg) {
 685   if (DiagHandler)
 686     (*DiagHandler)(LTO_DS_WARNING, ErrMsg.c_str(), DiagContext);
 687   else
 688     Context.diagnose(LTODiagnosticInfo(ErrMsg, DS_Warning));
 689 }