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      1 //===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
      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 #include "clang/CodeGen/BackendUtil.h"
     11 #include "clang/Basic/Diagnostic.h"
     12 #include "clang/Basic/LangOptions.h"
     13 #include "clang/Basic/TargetOptions.h"
     14 #include "clang/Frontend/CodeGenOptions.h"
     15 #include "clang/Frontend/FrontendDiagnostic.h"
     16 #include "llvm/Analysis/Verifier.h"
     17 #include "llvm/Assembly/PrintModulePass.h"
     18 #include "llvm/Bitcode/ReaderWriter.h"
     19 #include "llvm/CodeGen/RegAllocRegistry.h"
     20 #include "llvm/CodeGen/SchedulerRegistry.h"
     21 #include "llvm/IR/DataLayout.h"
     22 #include "llvm/IR/Module.h"
     23 #include "llvm/MC/SubtargetFeature.h"
     24 #include "llvm/PassManager.h"
     25 #include "llvm/Support/CommandLine.h"
     26 #include "llvm/Support/FormattedStream.h"
     27 #include "llvm/Support/PrettyStackTrace.h"
     28 #include "llvm/Support/TargetRegistry.h"
     29 #include "llvm/Support/Timer.h"
     30 #include "llvm/Support/raw_ostream.h"
     31 #include "llvm/Target/TargetLibraryInfo.h"
     32 #include "llvm/Target/TargetMachine.h"
     33 #include "llvm/Target/TargetOptions.h"
     34 #include "llvm/Transforms/IPO.h"
     35 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
     36 #include "llvm/Transforms/Instrumentation.h"
     37 #include "llvm/Transforms/ObjCARC.h"
     38 #include "llvm/Transforms/Scalar.h"
     39 using namespace clang;
     40 using namespace llvm;
     41 
     42 namespace {
     43 
     44 class EmitAssemblyHelper {
     45   DiagnosticsEngine &Diags;
     46   const CodeGenOptions &CodeGenOpts;
     47   const clang::TargetOptions &TargetOpts;
     48   const LangOptions &LangOpts;
     49   Module *TheModule;
     50 
     51   Timer CodeGenerationTime;
     52 
     53   mutable PassManager *CodeGenPasses;
     54   mutable PassManager *PerModulePasses;
     55   mutable FunctionPassManager *PerFunctionPasses;
     56 
     57 private:
     58   PassManager *getCodeGenPasses(TargetMachine *TM) const {
     59     if (!CodeGenPasses) {
     60       CodeGenPasses = new PassManager();
     61       CodeGenPasses->add(new DataLayout(TheModule));
     62       if (TM)
     63         TM->addAnalysisPasses(*CodeGenPasses);
     64     }
     65     return CodeGenPasses;
     66   }
     67 
     68   PassManager *getPerModulePasses(TargetMachine *TM) const {
     69     if (!PerModulePasses) {
     70       PerModulePasses = new PassManager();
     71       PerModulePasses->add(new DataLayout(TheModule));
     72       if (TM)
     73         TM->addAnalysisPasses(*PerModulePasses);
     74     }
     75     return PerModulePasses;
     76   }
     77 
     78   FunctionPassManager *getPerFunctionPasses(TargetMachine *TM) const {
     79     if (!PerFunctionPasses) {
     80       PerFunctionPasses = new FunctionPassManager(TheModule);
     81       PerFunctionPasses->add(new DataLayout(TheModule));
     82       if (TM)
     83         TM->addAnalysisPasses(*PerFunctionPasses);
     84     }
     85     return PerFunctionPasses;
     86   }
     87 
     88 
     89   void CreatePasses(TargetMachine *TM);
     90 
     91   /// CreateTargetMachine - Generates the TargetMachine.
     92   /// Returns Null if it is unable to create the target machine.
     93   /// Some of our clang tests specify triples which are not built
     94   /// into clang. This is okay because these tests check the generated
     95   /// IR, and they require DataLayout which depends on the triple.
     96   /// In this case, we allow this method to fail and not report an error.
     97   /// When MustCreateTM is used, we print an error if we are unable to load
     98   /// the requested target.
     99   TargetMachine *CreateTargetMachine(bool MustCreateTM);
    100 
    101   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
    102   ///
    103   /// \return True on success.
    104   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS,
    105                      TargetMachine *TM);
    106 
    107 public:
    108   EmitAssemblyHelper(DiagnosticsEngine &_Diags,
    109                      const CodeGenOptions &CGOpts,
    110                      const clang::TargetOptions &TOpts,
    111                      const LangOptions &LOpts,
    112                      Module *M)
    113     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
    114       TheModule(M), CodeGenerationTime("Code Generation Time"),
    115       CodeGenPasses(0), PerModulePasses(0), PerFunctionPasses(0) {}
    116 
    117   ~EmitAssemblyHelper() {
    118     delete CodeGenPasses;
    119     delete PerModulePasses;
    120     delete PerFunctionPasses;
    121   }
    122 
    123   void EmitAssembly(BackendAction Action, raw_ostream *OS);
    124 };
    125 
    126 // We need this wrapper to access LangOpts and CGOpts from extension functions
    127 // that we add to the PassManagerBuilder.
    128 class PassManagerBuilderWrapper : public PassManagerBuilder {
    129 public:
    130   PassManagerBuilderWrapper(const CodeGenOptions &CGOpts,
    131                             const LangOptions &LangOpts)
    132       : PassManagerBuilder(), CGOpts(CGOpts), LangOpts(LangOpts) {}
    133   const CodeGenOptions &getCGOpts() const { return CGOpts; }
    134   const LangOptions &getLangOpts() const { return LangOpts; }
    135 private:
    136   const CodeGenOptions &CGOpts;
    137   const LangOptions &LangOpts;
    138 };
    139 
    140 }
    141 
    142 static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
    143   if (Builder.OptLevel > 0)
    144     PM.add(createObjCARCAPElimPass());
    145 }
    146 
    147 static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
    148   if (Builder.OptLevel > 0)
    149     PM.add(createObjCARCExpandPass());
    150 }
    151 
    152 static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
    153   if (Builder.OptLevel > 0)
    154     PM.add(createObjCARCOptPass());
    155 }
    156 
    157 static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
    158                                     PassManagerBase &PM) {
    159   PM.add(createBoundsCheckingPass());
    160 }
    161 
    162 static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
    163                                       PassManagerBase &PM) {
    164   const PassManagerBuilderWrapper &BuilderWrapper =
    165       static_cast<const PassManagerBuilderWrapper&>(Builder);
    166   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
    167   const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
    168   PM.add(createAddressSanitizerFunctionPass(
    169       LangOpts.Sanitize.InitOrder,
    170       LangOpts.Sanitize.UseAfterReturn,
    171       LangOpts.Sanitize.UseAfterScope,
    172       CGOpts.SanitizerBlacklistFile,
    173       CGOpts.SanitizeAddressZeroBaseShadow));
    174   PM.add(createAddressSanitizerModulePass(
    175       LangOpts.Sanitize.InitOrder,
    176       CGOpts.SanitizerBlacklistFile,
    177       CGOpts.SanitizeAddressZeroBaseShadow));
    178 }
    179 
    180 static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
    181                                    PassManagerBase &PM) {
    182   const PassManagerBuilderWrapper &BuilderWrapper =
    183       static_cast<const PassManagerBuilderWrapper&>(Builder);
    184   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
    185   PM.add(createMemorySanitizerPass(CGOpts.SanitizeMemoryTrackOrigins,
    186                                    CGOpts.SanitizerBlacklistFile));
    187 
    188   // MemorySanitizer inserts complex instrumentation that mostly follows
    189   // the logic of the original code, but operates on "shadow" values.
    190   // It can benefit from re-running some general purpose optimization passes.
    191   if (Builder.OptLevel > 0) {
    192     PM.add(createEarlyCSEPass());
    193     PM.add(createReassociatePass());
    194     PM.add(createLICMPass());
    195     PM.add(createGVNPass());
    196     PM.add(createInstructionCombiningPass());
    197     PM.add(createDeadStoreEliminationPass());
    198   }
    199 }
    200 
    201 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
    202                                    PassManagerBase &PM) {
    203   const PassManagerBuilderWrapper &BuilderWrapper =
    204       static_cast<const PassManagerBuilderWrapper&>(Builder);
    205   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
    206   PM.add(createThreadSanitizerPass(CGOpts.SanitizerBlacklistFile));
    207 }
    208 
    209 void EmitAssemblyHelper::CreatePasses(TargetMachine *TM) {
    210   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
    211   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.getInlining();
    212 
    213   // Handle disabling of LLVM optimization, where we want to preserve the
    214   // internal module before any optimization.
    215   if (CodeGenOpts.DisableLLVMOpts) {
    216     OptLevel = 0;
    217     Inlining = CodeGenOpts.NoInlining;
    218   }
    219 
    220   PassManagerBuilderWrapper PMBuilder(CodeGenOpts, LangOpts);
    221   PMBuilder.OptLevel = OptLevel;
    222   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
    223 
    224   PMBuilder.DisableSimplifyLibCalls = !CodeGenOpts.SimplifyLibCalls;
    225   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
    226   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
    227 
    228   // In ObjC ARC mode, add the main ARC optimization passes.
    229   if (LangOpts.ObjCAutoRefCount) {
    230     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
    231                            addObjCARCExpandPass);
    232     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
    233                            addObjCARCAPElimPass);
    234     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
    235                            addObjCARCOptPass);
    236   }
    237 
    238   if (LangOpts.Sanitize.Bounds) {
    239     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
    240                            addBoundsCheckingPass);
    241     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    242                            addBoundsCheckingPass);
    243   }
    244 
    245   if (LangOpts.Sanitize.Address) {
    246     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
    247                            addAddressSanitizerPasses);
    248     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    249                            addAddressSanitizerPasses);
    250   }
    251 
    252   if (LangOpts.Sanitize.Memory) {
    253     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
    254                            addMemorySanitizerPass);
    255     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    256                            addMemorySanitizerPass);
    257   }
    258 
    259   if (LangOpts.Sanitize.Thread) {
    260     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
    261                            addThreadSanitizerPass);
    262     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    263                            addThreadSanitizerPass);
    264   }
    265 
    266   // Figure out TargetLibraryInfo.
    267   Triple TargetTriple(TheModule->getTargetTriple());
    268   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
    269   if (!CodeGenOpts.SimplifyLibCalls)
    270     PMBuilder.LibraryInfo->disableAllFunctions();
    271 
    272   switch (Inlining) {
    273   case CodeGenOptions::NoInlining: break;
    274   case CodeGenOptions::NormalInlining: {
    275     // FIXME: Derive these constants in a principled fashion.
    276     unsigned Threshold = 225;
    277     if (CodeGenOpts.OptimizeSize == 1)      // -Os
    278       Threshold = 75;
    279     else if (CodeGenOpts.OptimizeSize == 2) // -Oz
    280       Threshold = 25;
    281     else if (OptLevel > 2)
    282       Threshold = 275;
    283     PMBuilder.Inliner = createFunctionInliningPass(Threshold);
    284     break;
    285   }
    286   case CodeGenOptions::OnlyAlwaysInlining:
    287     // Respect always_inline.
    288     if (OptLevel == 0)
    289       // Do not insert lifetime intrinsics at -O0.
    290       PMBuilder.Inliner = createAlwaysInlinerPass(false);
    291     else
    292       PMBuilder.Inliner = createAlwaysInlinerPass();
    293     break;
    294   }
    295 
    296   // Set up the per-function pass manager.
    297   FunctionPassManager *FPM = getPerFunctionPasses(TM);
    298   if (CodeGenOpts.VerifyModule)
    299     FPM->add(createVerifierPass());
    300   PMBuilder.populateFunctionPassManager(*FPM);
    301 
    302   // Set up the per-module pass manager.
    303   PassManager *MPM = getPerModulePasses(TM);
    304 
    305   if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
    306     // Not using 'GCOVOptions::getDefault' allows us to avoid exiting if
    307     // LLVM's -default-gcov-version flag is set to something invalid.
    308     GCOVOptions Options;
    309     Options.EmitNotes = CodeGenOpts.EmitGcovNotes;
    310     Options.EmitData = CodeGenOpts.EmitGcovArcs;
    311     memcpy(Options.Version, CodeGenOpts.CoverageVersion, 4);
    312     Options.UseCfgChecksum = CodeGenOpts.CoverageExtraChecksum;
    313     Options.NoRedZone = CodeGenOpts.DisableRedZone;
    314     // FIXME: the clang flag name is backwards.
    315     Options.FunctionNamesInData =
    316         !CodeGenOpts.CoverageFunctionNamesInData;
    317     MPM->add(createGCOVProfilerPass(Options));
    318     if (CodeGenOpts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
    319       MPM->add(createStripSymbolsPass(true));
    320   }
    321 
    322   PMBuilder.populateModulePassManager(*MPM);
    323 }
    324 
    325 TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
    326   // Create the TargetMachine for generating code.
    327   std::string Error;
    328   std::string Triple = TheModule->getTargetTriple();
    329   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
    330   if (!TheTarget) {
    331     if (MustCreateTM)
    332       Diags.Report(diag::err_fe_unable_to_create_target) << Error;
    333     return 0;
    334   }
    335 
    336   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
    337   // being gross, this is also totally broken if we ever care about
    338   // concurrency.
    339 
    340   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
    341 
    342   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
    343   TargetMachine::setDataSections    (CodeGenOpts.DataSections);
    344 
    345   // FIXME: Parse this earlier.
    346   llvm::CodeModel::Model CM;
    347   if (CodeGenOpts.CodeModel == "small") {
    348     CM = llvm::CodeModel::Small;
    349   } else if (CodeGenOpts.CodeModel == "kernel") {
    350     CM = llvm::CodeModel::Kernel;
    351   } else if (CodeGenOpts.CodeModel == "medium") {
    352     CM = llvm::CodeModel::Medium;
    353   } else if (CodeGenOpts.CodeModel == "large") {
    354     CM = llvm::CodeModel::Large;
    355   } else {
    356     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
    357     CM = llvm::CodeModel::Default;
    358   }
    359 
    360   SmallVector<const char *, 16> BackendArgs;
    361   BackendArgs.push_back("clang"); // Fake program name.
    362   if (!CodeGenOpts.DebugPass.empty()) {
    363     BackendArgs.push_back("-debug-pass");
    364     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
    365   }
    366   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
    367     BackendArgs.push_back("-limit-float-precision");
    368     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
    369   }
    370   if (llvm::TimePassesIsEnabled)
    371     BackendArgs.push_back("-time-passes");
    372   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
    373     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
    374   if (CodeGenOpts.NoGlobalMerge)
    375     BackendArgs.push_back("-global-merge=false");
    376   BackendArgs.push_back(0);
    377   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
    378                                     BackendArgs.data());
    379 
    380   std::string FeaturesStr;
    381   if (TargetOpts.Features.size()) {
    382     SubtargetFeatures Features;
    383     for (std::vector<std::string>::const_iterator
    384            it = TargetOpts.Features.begin(),
    385            ie = TargetOpts.Features.end(); it != ie; ++it)
    386       Features.AddFeature(*it);
    387     FeaturesStr = Features.getString();
    388   }
    389 
    390   llvm::Reloc::Model RM = llvm::Reloc::Default;
    391   if (CodeGenOpts.RelocationModel == "static") {
    392     RM = llvm::Reloc::Static;
    393   } else if (CodeGenOpts.RelocationModel == "pic") {
    394     RM = llvm::Reloc::PIC_;
    395   } else {
    396     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
    397            "Invalid PIC model!");
    398     RM = llvm::Reloc::DynamicNoPIC;
    399   }
    400 
    401   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
    402   switch (CodeGenOpts.OptimizationLevel) {
    403   default: break;
    404   case 0: OptLevel = CodeGenOpt::None; break;
    405   case 3: OptLevel = CodeGenOpt::Aggressive; break;
    406   }
    407 
    408   llvm::TargetOptions Options;
    409 
    410   // Set frame pointer elimination mode.
    411   if (!CodeGenOpts.DisableFPElim) {
    412     Options.NoFramePointerElim = false;
    413     Options.NoFramePointerElimNonLeaf = false;
    414   } else if (CodeGenOpts.OmitLeafFramePointer) {
    415     Options.NoFramePointerElim = false;
    416     Options.NoFramePointerElimNonLeaf = true;
    417   } else {
    418     Options.NoFramePointerElim = true;
    419     Options.NoFramePointerElimNonLeaf = true;
    420   }
    421 
    422   if (CodeGenOpts.UseInitArray)
    423     Options.UseInitArray = true;
    424 
    425   // Set float ABI type.
    426   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
    427     Options.FloatABIType = llvm::FloatABI::Soft;
    428   else if (CodeGenOpts.FloatABI == "hard")
    429     Options.FloatABIType = llvm::FloatABI::Hard;
    430   else {
    431     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
    432     Options.FloatABIType = llvm::FloatABI::Default;
    433   }
    434 
    435   // Set FP fusion mode.
    436   switch (CodeGenOpts.getFPContractMode()) {
    437   case CodeGenOptions::FPC_Off:
    438     Options.AllowFPOpFusion = llvm::FPOpFusion::Strict;
    439     break;
    440   case CodeGenOptions::FPC_On:
    441     Options.AllowFPOpFusion = llvm::FPOpFusion::Standard;
    442     break;
    443   case CodeGenOptions::FPC_Fast:
    444     Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
    445     break;
    446   }
    447 
    448   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
    449   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
    450   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
    451   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
    452   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
    453   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
    454   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
    455   Options.RealignStack = CodeGenOpts.StackRealignment;
    456   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
    457   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
    458   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
    459   Options.SSPBufferSize = CodeGenOpts.SSPBufferSize;
    460 
    461   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
    462                                                      FeaturesStr, Options,
    463                                                      RM, CM, OptLevel);
    464 
    465   if (CodeGenOpts.RelaxAll)
    466     TM->setMCRelaxAll(true);
    467   if (CodeGenOpts.SaveTempLabels)
    468     TM->setMCSaveTempLabels(true);
    469   if (CodeGenOpts.NoDwarf2CFIAsm)
    470     TM->setMCUseCFI(false);
    471   if (!CodeGenOpts.NoDwarfDirectoryAsm)
    472     TM->setMCUseDwarfDirectory(true);
    473   if (CodeGenOpts.NoExecStack)
    474     TM->setMCNoExecStack(true);
    475 
    476   return TM;
    477 }
    478 
    479 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
    480                                        formatted_raw_ostream &OS,
    481                                        TargetMachine *TM) {
    482 
    483   // Create the code generator passes.
    484   PassManager *PM = getCodeGenPasses(TM);
    485 
    486   // Add LibraryInfo.
    487   llvm::Triple TargetTriple(TheModule->getTargetTriple());
    488   TargetLibraryInfo *TLI = new TargetLibraryInfo(TargetTriple);
    489   if (!CodeGenOpts.SimplifyLibCalls)
    490     TLI->disableAllFunctions();
    491   PM->add(TLI);
    492 
    493   // Add Target specific analysis passes.
    494   TM->addAnalysisPasses(*PM);
    495 
    496   // Normal mode, emit a .s or .o file by running the code generator. Note,
    497   // this also adds codegenerator level optimization passes.
    498   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
    499   if (Action == Backend_EmitObj)
    500     CGFT = TargetMachine::CGFT_ObjectFile;
    501   else if (Action == Backend_EmitMCNull)
    502     CGFT = TargetMachine::CGFT_Null;
    503   else
    504     assert(Action == Backend_EmitAssembly && "Invalid action!");
    505 
    506   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
    507   // "codegen" passes so that it isn't run multiple times when there is
    508   // inlining happening.
    509   if (LangOpts.ObjCAutoRefCount &&
    510       CodeGenOpts.OptimizationLevel > 0)
    511     PM->add(createObjCARCContractPass());
    512 
    513   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
    514                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
    515     Diags.Report(diag::err_fe_unable_to_interface_with_target);
    516     return false;
    517   }
    518 
    519   return true;
    520 }
    521 
    522 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
    523   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
    524   llvm::formatted_raw_ostream FormattedOS;
    525 
    526   bool UsesCodeGen = (Action != Backend_EmitNothing &&
    527                       Action != Backend_EmitBC &&
    528                       Action != Backend_EmitLL);
    529   TargetMachine *TM = CreateTargetMachine(UsesCodeGen);
    530   CreatePasses(TM);
    531 
    532   switch (Action) {
    533   case Backend_EmitNothing:
    534     break;
    535 
    536   case Backend_EmitBC:
    537     getPerModulePasses(TM)->add(createBitcodeWriterPass(*OS));
    538     break;
    539 
    540   case Backend_EmitLL:
    541     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
    542     getPerModulePasses(TM)->add(createPrintModulePass(&FormattedOS));
    543     break;
    544 
    545   default:
    546     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
    547     if (!AddEmitPasses(Action, FormattedOS, TM))
    548       return;
    549   }
    550 
    551   // Before executing passes, print the final values of the LLVM options.
    552   cl::PrintOptionValues();
    553 
    554   // Run passes. For now we do all passes at once, but eventually we
    555   // would like to have the option of streaming code generation.
    556 
    557   if (PerFunctionPasses) {
    558     PrettyStackTraceString CrashInfo("Per-function optimization");
    559 
    560     PerFunctionPasses->doInitialization();
    561     for (Module::iterator I = TheModule->begin(),
    562            E = TheModule->end(); I != E; ++I)
    563       if (!I->isDeclaration())
    564         PerFunctionPasses->run(*I);
    565     PerFunctionPasses->doFinalization();
    566   }
    567 
    568   if (PerModulePasses) {
    569     PrettyStackTraceString CrashInfo("Per-module optimization passes");
    570     PerModulePasses->run(*TheModule);
    571   }
    572 
    573   if (CodeGenPasses) {
    574     PrettyStackTraceString CrashInfo("Code generation");
    575     CodeGenPasses->run(*TheModule);
    576   }
    577 }
    578 
    579 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
    580                               const CodeGenOptions &CGOpts,
    581                               const clang::TargetOptions &TOpts,
    582                               const LangOptions &LOpts,
    583                               Module *M,
    584                               BackendAction Action, raw_ostream *OS) {
    585   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);
    586 
    587   AsmHelper.EmitAssembly(Action, OS);
    588 }
    589