tools/llc/llc.cpp

   1 //===-- llc.cpp - Implement the LLVM Native Code Generator ----------------===//
   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 is the llc code generator driver. It provides a convenient
  11 // command-line interface for generating native assembly-language code
  12 // or C code, given LLVM bitcode.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/ADT/STLExtras.h"
  17 #include "llvm/ADT/Triple.h"
  18 #include "llvm/Analysis/TargetLibraryInfo.h"
  19 #include "llvm/CodeGen/CommandFlags.inc"
  20 #include "llvm/CodeGen/LinkAllAsmWriterComponents.h"
  21 #include "llvm/CodeGen/LinkAllCodegenComponents.h"
  22 #include "llvm/CodeGen/MIRParser/MIRParser.h"
  23 #include "llvm/CodeGen/MachineFunctionPass.h"
  24 #include "llvm/CodeGen/MachineModuleInfo.h"
  25 #include "llvm/CodeGen/TargetPassConfig.h"
  26 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  27 #include "llvm/IR/AutoUpgrade.h"
  28 #include "llvm/IR/DataLayout.h"
  29 #include "llvm/IR/DiagnosticInfo.h"
  30 #include "llvm/IR/DiagnosticPrinter.h"
  31 #include "llvm/IR/IRPrintingPasses.h"
  32 #include "llvm/IR/LLVMContext.h"
  33 #include "llvm/IR/LegacyPassManager.h"
  34 #include "llvm/IR/Module.h"
  35 #include "llvm/IR/Verifier.h"
  36 #include "llvm/IRReader/IRReader.h"
  37 #include "llvm/MC/SubtargetFeature.h"
  38 #include "llvm/Pass.h"
  39 #include "llvm/Support/CommandLine.h"
  40 #include "llvm/Support/Debug.h"
  41 #include "llvm/Support/FileSystem.h"
  42 #include "llvm/Support/FormattedStream.h"
  43 #include "llvm/Support/Host.h"
  44 #include "llvm/Support/InitLLVM.h"
  45 #include "llvm/Support/ManagedStatic.h"
  46 #include "llvm/Support/PluginLoader.h"
  47 #include "llvm/Support/SourceMgr.h"
  48 #include "llvm/Support/TargetRegistry.h"
  49 #include "llvm/Support/TargetSelect.h"
  50 #include "llvm/Support/ToolOutputFile.h"
  51 #include "llvm/Support/WithColor.h"
  52 #include "llvm/Target/TargetMachine.h"
  53 #include "llvm/Transforms/Utils/Cloning.h"
  54 #include <memory>
  55 using namespace llvm;
  56
  57 // General options for llc.  Other pass-specific options are specified
  58 // within the corresponding llc passes, and target-specific options
  59 // and back-end code generation options are specified with the target machine.
  60 //
  61 static cl::opt<std::string>
  62 InputFilename(cl::Positional, cl::desc("<input bitcode>"), cl::init("-"));
  63
  64 static cl::opt<std::string>
  65 InputLanguage("x", cl::desc("Input language ('ir' or 'mir')"));
  66
  67 static cl::opt<std::string>
  68 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"));
  69
  70 static cl::opt<std::string>
  71     SplitDwarfOutputFile("split-dwarf-output",
  72                          cl::desc(".dwo output filename"),
  73                          cl::value_desc("filename"));
  74
  75 static cl::opt<unsigned>
  76 TimeCompilations("time-compilations", cl::Hidden, cl::init(1u),
  77                  cl::value_desc("N"),
  78                  cl::desc("Repeat compilation N times for timing"));
  79
  80 static cl::opt<bool>
  81 NoIntegratedAssembler("no-integrated-as", cl::Hidden,
  82                       cl::desc("Disable integrated assembler"));
  83
  84 static cl::opt<bool>
  85     PreserveComments("preserve-as-comments", cl::Hidden,
  86                      cl::desc("Preserve Comments in outputted assembly"),
  87                      cl::init(true));
  88
  89 // Determine optimization level.
  90 static cl::opt<char>
  91 OptLevel("O",
  92          cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
  93                   "(default = '-O2')"),
  94          cl::Prefix,
  95          cl::ZeroOrMore,
  96          cl::init(' '));
  97
  98 static cl::opt<std::string>
  99 TargetTriple("mtriple", cl::desc("Override target triple for module"));
 100
 101 static cl::opt<std::string> SplitDwarfFile(
 102     "split-dwarf-file",
 103     cl::desc(
 104         "Specify the name of the .dwo file to encode in the DWARF output"));
 105
 106 static cl::opt<bool> NoVerify("disable-verify", cl::Hidden,
 107                               cl::desc("Do not verify input module"));
 108
 109 static cl::opt<bool> DisableSimplifyLibCalls("disable-simplify-libcalls",
 110                                              cl::desc("Disable simplify-libcalls"));
 111
 112 static cl::opt<bool> ShowMCEncoding("show-mc-encoding", cl::Hidden,
 113                                     cl::desc("Show encoding in .s output"));
 114
 115 static cl::opt<bool> EnableDwarfDirectory(
 116     "enable-dwarf-directory", cl::Hidden,
 117     cl::desc("Use .file directives with an explicit directory."));
 118
 119 static cl::opt<bool> AsmVerbose("asm-verbose",
 120                                 cl::desc("Add comments to directives."),
 121                                 cl::init(true));
 122
 123 static cl::opt<bool>
 124     CompileTwice("compile-twice", cl::Hidden,
 125                  cl::desc("Run everything twice, re-using the same pass "
 126                           "manager and verify the result is the same."),
 127                  cl::init(false));
 128
 129 static cl::opt<bool> DiscardValueNames(
 130     "discard-value-names",
 131     cl::desc("Discard names from Value (other than GlobalValue)."),
 132     cl::init(false), cl::Hidden);
 133
 134 static cl::list<std::string> IncludeDirs("I", cl::desc("include search path"));
 135
 136 static cl::opt<bool> PassRemarksWithHotness(
 137     "pass-remarks-with-hotness",
 138     cl::desc("With PGO, include profile count in optimization remarks"),
 139     cl::Hidden);
 140
 141 static cl::opt<unsigned> PassRemarksHotnessThreshold(
 142     "pass-remarks-hotness-threshold",
 143     cl::desc("Minimum profile count required for an optimization remark to be output"),
 144     cl::Hidden);
 145
 146 static cl::opt<std::string>
 147     RemarksFilename("pass-remarks-output",
 148                     cl::desc("YAML output filename for pass remarks"),
 149                     cl::value_desc("filename"));
 150
 151 namespace {
 152 static ManagedStatic<std::vector<std::string>> RunPassNames;
 153
 154 struct RunPassOption {
 155   void operator=(const std::string &Val) const {
 156     if (Val.empty())
 157       return;
 158     SmallVector<StringRef, 8> PassNames;
 159     StringRef(Val).split(PassNames, ',', -1, false);
 160     for (auto PassName : PassNames)
 161       RunPassNames->push_back(PassName);
 162   }
 163 };
 164 }
 165
 166 static RunPassOption RunPassOpt;
 167
 168 static cl::opt<RunPassOption, true, cl::parser<std::string>> RunPass(
 169     "run-pass",
 170     cl::desc("Run compiler only for specified passes (comma separated list)"),
 171     cl::value_desc("pass-name"), cl::ZeroOrMore, cl::location(RunPassOpt));
 172
 173 static int compileModule(char **, LLVMContext &);
 174
 175 static std::unique_ptr<ToolOutputFile> GetOutputStream(const char *TargetName,
 176                                                        Triple::OSType OS,
 177                                                        const char *ProgName) {
 178   // If we don't yet have an output filename, make one.
 179   if (OutputFilename.empty()) {
 180     if (InputFilename == "-")
 181       OutputFilename = "-";
 182     else {
 183       // If InputFilename ends in .bc or .ll, remove it.
 184       StringRef IFN = InputFilename;
 185       if (IFN.endswith(".bc") || IFN.endswith(".ll"))
 186         OutputFilename = IFN.drop_back(3);
 187       else if (IFN.endswith(".mir"))
 188         OutputFilename = IFN.drop_back(4);
 189       else
 190         OutputFilename = IFN;
 191
 192       switch (FileType) {
 193       case TargetMachine::CGFT_AssemblyFile:
 194         if (TargetName[0] == 'c') {
 195           if (TargetName[1] == 0)
 196             OutputFilename += ".cbe.c";
 197           else if (TargetName[1] == 'p' && TargetName[2] == 'p')
 198             OutputFilename += ".cpp";
 199           else
 200             OutputFilename += ".s";
 201         } else
 202           OutputFilename += ".s";
 203         break;
 204       case TargetMachine::CGFT_ObjectFile:
 205         if (OS == Triple::Win32)
 206           OutputFilename += ".obj";
 207         else
 208           OutputFilename += ".o";
 209         break;
 210       case TargetMachine::CGFT_Null:
 211         OutputFilename += ".null";
 212         break;
 213       }
 214     }
 215   }
 216
 217   // Decide if we need "binary" output.
 218   bool Binary = false;
 219   switch (FileType) {
 220   case TargetMachine::CGFT_AssemblyFile:
 221     break;
 222   case TargetMachine::CGFT_ObjectFile:
 223   case TargetMachine::CGFT_Null:
 224     Binary = true;
 225     break;
 226   }
 227
 228   // Open the file.
 229   std::error_code EC;
 230   sys::fs::OpenFlags OpenFlags = sys::fs::F_None;
 231   if (!Binary)
 232     OpenFlags |= sys::fs::F_Text;
 233   auto FDOut = llvm::make_unique<ToolOutputFile>(OutputFilename, EC, OpenFlags);
 234   if (EC) {
 235     WithColor::error() << EC.message() << '\n';
 236     return nullptr;
 237   }
 238
 239   return FDOut;
 240 }
 241
 242 struct LLCDiagnosticHandler : public DiagnosticHandler {
 243   bool *HasError;
 244   LLCDiagnosticHandler(bool *HasErrorPtr) : HasError(HasErrorPtr) {}
 245   bool handleDiagnostics(const DiagnosticInfo &DI) override {
 246     if (DI.getSeverity() == DS_Error)
 247       *HasError = true;
 248
 249     if (auto *Remark = dyn_cast<DiagnosticInfoOptimizationBase>(&DI))
 250       if (!Remark->isEnabled())
 251         return true;
 252
 253     DiagnosticPrinterRawOStream DP(errs());
 254     errs() << LLVMContext::getDiagnosticMessagePrefix(DI.getSeverity()) << ": ";
 255     DI.print(DP);
 256     errs() << "\n";
 257     return true;
 258   }
 259 };
 260
 261 static void InlineAsmDiagHandler(const SMDiagnostic &SMD, void *Context,
 262                                  unsigned LocCookie) {
 263   bool *HasError = static_cast<bool *>(Context);
 264   if (SMD.getKind() == SourceMgr::DK_Error)
 265     *HasError = true;
 266
 267   SMD.print(nullptr, errs());
 268
 269   // For testing purposes, we print the LocCookie here.
 270   if (LocCookie)
 271     WithColor::note() << "!srcloc = " << LocCookie << "\n";
 272 }
 273
 274 // main - Entry point for the llc compiler.
 275 //
 276 int main(int argc, char **argv) {
 277   InitLLVM X(argc, argv);
 278
 279   // Enable debug stream buffering.
 280   EnableDebugBuffering = true;
 281
 282   LLVMContext Context;
 283
 284   // Initialize targets first, so that --version shows registered targets.
 285   InitializeAllTargets();
 286   InitializeAllTargetMCs();
 287   InitializeAllAsmPrinters();
 288   InitializeAllAsmParsers();
 289
 290   // Initialize codegen and IR passes used by llc so that the -print-after,
 291   // -print-before, and -stop-after options work.
 292   PassRegistry *Registry = PassRegistry::getPassRegistry();
 293   initializeCore(*Registry);
 294   initializeCodeGen(*Registry);
 295   initializeLoopStrengthReducePass(*Registry);
 296   initializeLowerIntrinsicsPass(*Registry);
 297   initializeEntryExitInstrumenterPass(*Registry);
 298   initializePostInlineEntryExitInstrumenterPass(*Registry);
 299   initializeUnreachableBlockElimLegacyPassPass(*Registry);
 300   initializeConstantHoistingLegacyPassPass(*Registry);
 301   initializeScalarOpts(*Registry);
 302   initializeVectorization(*Registry);
 303   initializeScalarizeMaskedMemIntrinPass(*Registry);
 304   initializeExpandReductionsPass(*Registry);
 305
 306   // Initialize debugging passes.
 307   initializeScavengerTestPass(*Registry);
 308
 309   // Register the target printer for --version.
 310   cl::AddExtraVersionPrinter(TargetRegistry::printRegisteredTargetsForVersion);
 311
 312   cl::ParseCommandLineOptions(argc, argv, "llvm system compiler\n");
 313
 314   Context.setDiscardValueNames(DiscardValueNames);
 315
 316   // Set a diagnostic handler that doesn't exit on the first error
 317   bool HasError = false;
 318   Context.setDiagnosticHandler(
 319       llvm::make_unique<LLCDiagnosticHandler>(&HasError));
 320   Context.setInlineAsmDiagnosticHandler(InlineAsmDiagHandler, &HasError);
 321
 322   if (PassRemarksWithHotness)
 323     Context.setDiagnosticsHotnessRequested(true);
 324
 325   if (PassRemarksHotnessThreshold)
 326     Context.setDiagnosticsHotnessThreshold(PassRemarksHotnessThreshold);
 327
 328   std::unique_ptr<ToolOutputFile> YamlFile;
 329   if (RemarksFilename != "") {
 330     std::error_code EC;
 331     YamlFile =
 332         llvm::make_unique<ToolOutputFile>(RemarksFilename, EC, sys::fs::F_None);
 333     if (EC) {
 334       WithColor::error(errs(), argv[0]) << EC.message() << '\n';
 335       return 1;
 336     }
 337     Context.setDiagnosticsOutputFile(
 338         llvm::make_unique<yaml::Output>(YamlFile->os()));
 339   }
 340
 341   if (InputLanguage != "" && InputLanguage != "ir" &&
 342       InputLanguage != "mir") {
 343     WithColor::error(errs(), argv[0])
 344         << "input language must be '', 'IR' or 'MIR'\n";
 345     return 1;
 346   }
 347
 348   // Compile the module TimeCompilations times to give better compile time
 349   // metrics.
 350   for (unsigned I = TimeCompilations; I; --I)
 351     if (int RetVal = compileModule(argv, Context))
 352       return RetVal;
 353
 354   if (YamlFile)
 355     YamlFile->keep();
 356   return 0;
 357 }
 358
 359 static bool addPass(PassManagerBase &PM, const char *argv0,
 360                     StringRef PassName, TargetPassConfig &TPC) {
 361   if (PassName == "none")
 362     return false;
 363
 364   const PassRegistry *PR = PassRegistry::getPassRegistry();
 365   const PassInfo *PI = PR->getPassInfo(PassName);
 366   if (!PI) {
 367     WithColor::error(errs(), argv0)
 368         << "run-pass " << PassName << " is not registered.\n";
 369     return true;
 370   }
 371
 372   Pass *P;
 373   if (PI->getNormalCtor())
 374     P = PI->getNormalCtor()();
 375   else {
 376     WithColor::error(errs(), argv0)
 377         << "cannot create pass: " << PI->getPassName() << "\n";
 378     return true;
 379   }
 380   std::string Banner = std::string("After ") + std::string(P->getPassName());
 381   PM.add(P);
 382   TPC.printAndVerify(Banner);
 383
 384   return false;
 385 }
 386
 387 static int compileModule(char **argv, LLVMContext &Context) {
 388   // Load the module to be compiled...
 389   SMDiagnostic Err;
 390   std::unique_ptr<Module> M;
 391   std::unique_ptr<MIRParser> MIR;
 392   Triple TheTriple;
 393
 394   bool SkipModule = MCPU == "help" ||
 395                     (!MAttrs.empty() && MAttrs.front() == "help");
 396
 397   // If user just wants to list available options, skip module loading
 398   if (!SkipModule) {
 399     if (InputLanguage == "mir" ||
 400         (InputLanguage == "" && StringRef(InputFilename).endswith(".mir"))) {
 401       MIR = createMIRParserFromFile(InputFilename, Err, Context);
 402       if (MIR)
 403         M = MIR->parseIRModule();
 404     } else
 405       M = parseIRFile(InputFilename, Err, Context, false);
 406     if (!M) {
 407       Err.print(argv[0], WithColor::error(errs(), argv[0]));
 408       return 1;
 409     }
 410
 411     // If we are supposed to override the target triple, do so now.
 412     if (!TargetTriple.empty())
 413       M->setTargetTriple(Triple::normalize(TargetTriple));
 414     TheTriple = Triple(M->getTargetTriple());
 415   } else {
 416     TheTriple = Triple(Triple::normalize(TargetTriple));
 417   }
 418
 419   if (TheTriple.getTriple().empty())
 420     TheTriple.setTriple(sys::getDefaultTargetTriple());
 421
 422   // Get the target specific parser.
 423   std::string Error;
 424   const Target *TheTarget = TargetRegistry::lookupTarget(MArch, TheTriple,
 425                                                          Error);
 426   if (!TheTarget) {
 427     WithColor::error(errs(), argv[0]) << Error;
 428     return 1;
 429   }
 430
 431   std::string CPUStr = getCPUStr(), FeaturesStr = getFeaturesStr();
 432
 433   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
 434   switch (OptLevel) {
 435   default:
 436     WithColor::error(errs(), argv[0]) << "invalid optimization level.\n";
 437     return 1;
 438   case ' ': break;
 439   case '0': OLvl = CodeGenOpt::None; break;
 440   case '1': OLvl = CodeGenOpt::Less; break;
 441   case '2': OLvl = CodeGenOpt::Default; break;
 442   case '3': OLvl = CodeGenOpt::Aggressive; break;
 443   }
 444
 445   TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
 446   Options.DisableIntegratedAS = NoIntegratedAssembler;
 447   Options.MCOptions.ShowMCEncoding = ShowMCEncoding;
 448   Options.MCOptions.MCUseDwarfDirectory = EnableDwarfDirectory;
 449   Options.MCOptions.AsmVerbose = AsmVerbose;
 450   Options.MCOptions.PreserveAsmComments = PreserveComments;
 451   Options.MCOptions.IASSearchPaths = IncludeDirs;
 452   Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
 453
 454   std::unique_ptr<TargetMachine> Target(TheTarget->createTargetMachine(
 455       TheTriple.getTriple(), CPUStr, FeaturesStr, Options, getRelocModel(),
 456       getCodeModel(), OLvl));
 457
 458   assert(Target && "Could not allocate target machine!");
 459
 460   // If we don't have a module then just exit now. We do this down
 461   // here since the CPU/Feature help is underneath the target machine
 462   // creation.
 463   if (SkipModule)
 464     return 0;
 465
 466   assert(M && "Should have exited if we didn't have a module!");
 467   if (FloatABIForCalls != FloatABI::Default)
 468     Options.FloatABIType = FloatABIForCalls;
 469
 470   // Figure out where we are going to send the output.
 471   std::unique_ptr<ToolOutputFile> Out =
 472       GetOutputStream(TheTarget->getName(), TheTriple.getOS(), argv[0]);
 473   if (!Out) return 1;
 474
 475   std::unique_ptr<ToolOutputFile> DwoOut;
 476   if (!SplitDwarfOutputFile.empty()) {
 477     std::error_code EC;
 478     DwoOut = llvm::make_unique<ToolOutputFile>(SplitDwarfOutputFile, EC,
 479                                                sys::fs::F_None);
 480     if (EC) {
 481       WithColor::error(errs(), argv[0]) << EC.message() << '\n';
 482       return 1;
 483     }
 484   }
 485
 486   // Build up all of the passes that we want to do to the module.
 487   legacy::PassManager PM;
 488
 489   // Add an appropriate TargetLibraryInfo pass for the module's triple.
 490   TargetLibraryInfoImpl TLII(Triple(M->getTargetTriple()));
 491
 492   // The -disable-simplify-libcalls flag actually disables all builtin optzns.
 493   if (DisableSimplifyLibCalls)
 494     TLII.disableAllFunctions();
 495   PM.add(new TargetLibraryInfoWrapperPass(TLII));
 496
 497   // Add the target data from the target machine, if it exists, or the module.
 498   M->setDataLayout(Target->createDataLayout());
 499
 500   // This needs to be done after setting datalayout since it calls verifier
 501   // to check debug info whereas verifier relies on correct datalayout.
 502   UpgradeDebugInfo(*M);
 503
 504   // Verify module immediately to catch problems before doInitialization() is
 505   // called on any passes.
 506   if (!NoVerify && verifyModule(*M, &errs())) {
 507     std::string Prefix =
 508         (Twine(argv[0]) + Twine(": ") + Twine(InputFilename)).str();
 509     WithColor::error(errs(), Prefix) << "input module is broken!\n";
 510     return 1;
 511   }
 512
 513   // Override function attributes based on CPUStr, FeaturesStr, and command line
 514   // flags.
 515   setFunctionAttributes(CPUStr, FeaturesStr, *M);
 516
 517   if (RelaxAll.getNumOccurrences() > 0 &&
 518       FileType != TargetMachine::CGFT_ObjectFile)
 519     WithColor::warning(errs(), argv[0])
 520         << ": warning: ignoring -mc-relax-all because filetype != obj";
 521
 522   {
 523     raw_pwrite_stream *OS = &Out->os();
 524
 525     // Manually do the buffering rather than using buffer_ostream,
 526     // so we can memcmp the contents in CompileTwice mode
 527     SmallVector<char, 0> Buffer;
 528     std::unique_ptr<raw_svector_ostream> BOS;
 529     if ((FileType != TargetMachine::CGFT_AssemblyFile &&
 530          !Out->os().supportsSeeking()) ||
 531         CompileTwice) {
 532       BOS = make_unique<raw_svector_ostream>(Buffer);
 533       OS = BOS.get();
 534     }
 535
 536     const char *argv0 = argv[0];
 537     LLVMTargetMachine &LLVMTM = static_cast<LLVMTargetMachine&>(*Target);
 538     MachineModuleInfo *MMI = new MachineModuleInfo(&LLVMTM);
 539
 540     // Construct a custom pass pipeline that starts after instruction
 541     // selection.
 542     if (!RunPassNames->empty()) {
 543       if (!MIR) {
 544         WithColor::warning(errs(), argv[0])
 545             << "run-pass is for .mir file only.\n";
 546         return 1;
 547       }
 548       TargetPassConfig &TPC = *LLVMTM.createPassConfig(PM);
 549       if (TPC.hasLimitedCodeGenPipeline()) {
 550         WithColor::warning(errs(), argv[0])
 551             << "run-pass cannot be used with "
 552             << TPC.getLimitedCodeGenPipelineReason(" and ") << ".\n";
 553         return 1;
 554       }
 555
 556       TPC.setDisableVerify(NoVerify);
 557       PM.add(&TPC);
 558       PM.add(MMI);
 559       TPC.printAndVerify("");
 560       for (const std::string &RunPassName : *RunPassNames) {
 561         if (addPass(PM, argv0, RunPassName, TPC))
 562           return 1;
 563       }
 564       TPC.setInitialized();
 565       PM.add(createPrintMIRPass(*OS));
 566       PM.add(createFreeMachineFunctionPass());
 567     } else if (Target->addPassesToEmitFile(PM, *OS,
 568                                            DwoOut ? &DwoOut->os() : nullptr,
 569                                            FileType, NoVerify, MMI)) {
 570       WithColor::warning(errs(), argv[0])
 571           << "target does not support generation of this"
 572           << " file type!\n";
 573       return 1;
 574     }
 575
 576     if (MIR) {
 577       assert(MMI && "Forgot to create MMI?");
 578       if (MIR->parseMachineFunctions(*M, *MMI))
 579         return 1;
 580     }
 581
 582     // Before executing passes, print the final values of the LLVM options.
 583     cl::PrintOptionValues();
 584
 585     // If requested, run the pass manager over the same module again,
 586     // to catch any bugs due to persistent state in the passes. Note that
 587     // opt has the same functionality, so it may be worth abstracting this out
 588     // in the future.
 589     SmallVector<char, 0> CompileTwiceBuffer;
 590     if (CompileTwice) {
 591       std::unique_ptr<Module> M2(llvm::CloneModule(*M));
 592       PM.run(*M2);
 593       CompileTwiceBuffer = Buffer;
 594       Buffer.clear();
 595     }
 596
 597     PM.run(*M);
 598
 599     auto HasError =
 600         ((const LLCDiagnosticHandler *)(Context.getDiagHandlerPtr()))->HasError;
 601     if (*HasError)
 602       return 1;
 603
 604     // Compare the two outputs and make sure they're the same
 605     if (CompileTwice) {
 606       if (Buffer.size() != CompileTwiceBuffer.size() ||
 607           (memcmp(Buffer.data(), CompileTwiceBuffer.data(), Buffer.size()) !=
 608            0)) {
 609         errs()
 610             << "Running the pass manager twice changed the output.\n"
 611                "Writing the result of the second run to the specified output\n"
 612                "To generate the one-run comparison binary, just run without\n"
 613                "the compile-twice option\n";
 614         Out->os() << Buffer;
 615         Out->keep();
 616         return 1;
 617       }
 618     }
 619
 620     if (BOS) {
 621       Out->os() << Buffer;
 622     }
 623   }
 624
 625   // Declare success.
 626   Out->keep();
 627   if (DwoOut)
 628     DwoOut->keep();
 629
 630   return 0;
 631 }