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 "clang/Frontend/Utils.h"
17 #include "llvm/ADT/StringSwitch.h"
18 #include "llvm/Bitcode/BitcodeWriterPass.h"
19 #include "llvm/CodeGen/RegAllocRegistry.h"
20 #include "llvm/CodeGen/SchedulerRegistry.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/IRPrintingPasses.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/Verifier.h"
25 #include "llvm/MC/SubtargetFeature.h"
26 #include "llvm/PassManager.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/FormattedStream.h"
29 #include "llvm/Support/PrettyStackTrace.h"
30 #include "llvm/Support/TargetRegistry.h"
31 #include "llvm/Support/Timer.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include "llvm/Target/TargetLibraryInfo.h"
34 #include "llvm/Target/TargetMachine.h"
35 #include "llvm/Target/TargetOptions.h"
36 #include "llvm/Target/TargetSubtargetInfo.h"
37 #include "llvm/Transforms/IPO.h"
38 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
39 #include "llvm/Transforms/Instrumentation.h"
40 #include "llvm/Transforms/ObjCARC.h"
41 #include "llvm/Transforms/Scalar.h"
42 #include <memory>
43 using namespace clang;
44 using namespace llvm;
45 
46 namespace {
47 
48 class EmitAssemblyHelper {
49   DiagnosticsEngine &Diags;
50   const CodeGenOptions &CodeGenOpts;
51   const clang::TargetOptions &TargetOpts;
52   const LangOptions &LangOpts;
53   Module *TheModule;
54 
55   Timer CodeGenerationTime;
56 
57   mutable PassManager *CodeGenPasses;
58   mutable PassManager *PerModulePasses;
59   mutable FunctionPassManager *PerFunctionPasses;
60 
61 private:
62   PassManager *getCodeGenPasses() const {
63     if (!CodeGenPasses) {
64       CodeGenPasses = new PassManager();
65       CodeGenPasses->add(new DataLayoutPass());
66       if (TM)
67         TM->addAnalysisPasses(*CodeGenPasses);
68     }
69     return CodeGenPasses;
70   }
71 
72   PassManager *getPerModulePasses() const {
73     if (!PerModulePasses) {
74       PerModulePasses = new PassManager();
75       PerModulePasses->add(new DataLayoutPass());
76       if (TM)
77         TM->addAnalysisPasses(*PerModulePasses);
78     }
79     return PerModulePasses;
80   }
81 
82   FunctionPassManager *getPerFunctionPasses() const {
83     if (!PerFunctionPasses) {
84       PerFunctionPasses = new FunctionPassManager(TheModule);
85       PerFunctionPasses->add(new DataLayoutPass());
86       if (TM)
87         TM->addAnalysisPasses(*PerFunctionPasses);
88     }
89     return PerFunctionPasses;
90   }
91 
92   void CreatePasses();
93 
94   /// CreateTargetMachine - Generates the TargetMachine.
95   /// Returns Null if it is unable to create the target machine.
96   /// Some of our clang tests specify triples which are not built
97   /// into clang. This is okay because these tests check the generated
98   /// IR, and they require DataLayout which depends on the triple.
99   /// In this case, we allow this method to fail and not report an error.
100   /// When MustCreateTM is used, we print an error if we are unable to load
101   /// the requested target.
102   TargetMachine *CreateTargetMachine(bool MustCreateTM);
103 
104   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
105   ///
106   /// \return True on success.
107   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);
108 
109 public:
110   EmitAssemblyHelper(DiagnosticsEngine &_Diags,
111                      const CodeGenOptions &CGOpts,
112                      const clang::TargetOptions &TOpts,
113                      const LangOptions &LOpts,
114                      Module *M)
115     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
116       TheModule(M), CodeGenerationTime("Code Generation Time"),
117       CodeGenPasses(nullptr), PerModulePasses(nullptr),
118       PerFunctionPasses(nullptr) {}
119 
120   ~EmitAssemblyHelper() {
121     delete CodeGenPasses;
122     delete PerModulePasses;
123     delete PerFunctionPasses;
124     if (CodeGenOpts.DisableFree)
125       BuryPointer(std::move(TM));
126   }
127 
128   std::unique_ptr<TargetMachine> TM;
129 
130   void EmitAssembly(BackendAction Action, raw_ostream *OS);
131 };
132 
133 // We need this wrapper to access LangOpts and CGOpts from extension functions
134 // that we add to the PassManagerBuilder.
135 class PassManagerBuilderWrapper : public PassManagerBuilder {
136 public:
137   PassManagerBuilderWrapper(const CodeGenOptions &CGOpts,
138                             const LangOptions &LangOpts)
139       : PassManagerBuilder(), CGOpts(CGOpts), LangOpts(LangOpts) {}
140   const CodeGenOptions &getCGOpts() const { return CGOpts; }
141   const LangOptions &getLangOpts() const { return LangOpts; }
142 private:
143   const CodeGenOptions &CGOpts;
144   const LangOptions &LangOpts;
145 };
146 
147 }
148 
149 static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
150   if (Builder.OptLevel > 0)
151     PM.add(createObjCARCAPElimPass());
152 }
153 
154 static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
155   if (Builder.OptLevel > 0)
156     PM.add(createObjCARCExpandPass());
157 }
158 
159 static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
160   if (Builder.OptLevel > 0)
161     PM.add(createObjCARCOptPass());
162 }
163 
164 static void addSampleProfileLoaderPass(const PassManagerBuilder &Builder,
165                                        PassManagerBase &PM) {
166   const PassManagerBuilderWrapper &BuilderWrapper =
167       static_cast<const PassManagerBuilderWrapper &>(Builder);
168   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
169   PM.add(createSampleProfileLoaderPass(CGOpts.SampleProfileFile));
170 }
171 
172 static void addAddDiscriminatorsPass(const PassManagerBuilder &Builder,
173                                      PassManagerBase &PM) {
174   PM.add(createAddDiscriminatorsPass());
175 }
176 
177 static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
178                                     PassManagerBase &PM) {
179   PM.add(createBoundsCheckingPass());
180 }
181 
182 static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
183                                       PassManagerBase &PM) {
184   PM.add(createAddressSanitizerFunctionPass());
185   PM.add(createAddressSanitizerModulePass());
186 }
187 
188 static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
189                                    PassManagerBase &PM) {
190   const PassManagerBuilderWrapper &BuilderWrapper =
191       static_cast<const PassManagerBuilderWrapper&>(Builder);
192   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
193   PM.add(createMemorySanitizerPass(CGOpts.SanitizeMemoryTrackOrigins));
194 
195   // MemorySanitizer inserts complex instrumentation that mostly follows
196   // the logic of the original code, but operates on "shadow" values.
197   // It can benefit from re-running some general purpose optimization passes.
198   if (Builder.OptLevel > 0) {
199     PM.add(createEarlyCSEPass());
200     PM.add(createReassociatePass());
201     PM.add(createLICMPass());
202     PM.add(createGVNPass());
203     PM.add(createInstructionCombiningPass());
204     PM.add(createDeadStoreEliminationPass());
205   }
206 }
207 
208 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
209                                    PassManagerBase &PM) {
210   PM.add(createThreadSanitizerPass());
211 }
212 
213 static void addDataFlowSanitizerPass(const PassManagerBuilder &Builder,
214                                      PassManagerBase &PM) {
215   const PassManagerBuilderWrapper &BuilderWrapper =
216       static_cast<const PassManagerBuilderWrapper&>(Builder);
217   const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
218   PM.add(createDataFlowSanitizerPass(LangOpts.Sanitize.BlacklistFile));
219 }
220 
221 static TargetLibraryInfo *createTLI(llvm::Triple &TargetTriple,
222                                     const CodeGenOptions &CodeGenOpts) {
223   TargetLibraryInfo *TLI = new TargetLibraryInfo(TargetTriple);
224   if (!CodeGenOpts.SimplifyLibCalls)
225     TLI->disableAllFunctions();
226   return TLI;
227 }
228 
229 void EmitAssemblyHelper::CreatePasses() {
230   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
231   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.getInlining();
232 
233   // Handle disabling of LLVM optimization, where we want to preserve the
234   // internal module before any optimization.
235   if (CodeGenOpts.DisableLLVMOpts) {
236     OptLevel = 0;
237     Inlining = CodeGenOpts.NoInlining;
238   }
239 
240   PassManagerBuilderWrapper PMBuilder(CodeGenOpts, LangOpts);
241   PMBuilder.OptLevel = OptLevel;
242   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
243   PMBuilder.BBVectorize = CodeGenOpts.VectorizeBB;
244   PMBuilder.SLPVectorize = CodeGenOpts.VectorizeSLP;
245   PMBuilder.LoopVectorize = CodeGenOpts.VectorizeLoop;
246 
247   PMBuilder.DisableTailCalls = CodeGenOpts.DisableTailCalls;
248   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
249   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
250   PMBuilder.MergeFunctions = CodeGenOpts.MergeFunctions;
251   PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
252 
253   PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
254                          addAddDiscriminatorsPass);
255 
256   if (!CodeGenOpts.SampleProfileFile.empty())
257     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
258                            addSampleProfileLoaderPass);
259 
260   // In ObjC ARC mode, add the main ARC optimization passes.
261   if (LangOpts.ObjCAutoRefCount) {
262     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
263                            addObjCARCExpandPass);
264     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
265                            addObjCARCAPElimPass);
266     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
267                            addObjCARCOptPass);
268   }
269 
270   if (LangOpts.Sanitize.LocalBounds) {
271     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
272                            addBoundsCheckingPass);
273     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
274                            addBoundsCheckingPass);
275   }
276 
277   if (LangOpts.Sanitize.Address) {
278     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
279                            addAddressSanitizerPasses);
280     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
281                            addAddressSanitizerPasses);
282   }
283 
284   if (LangOpts.Sanitize.Memory) {
285     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
286                            addMemorySanitizerPass);
287     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
288                            addMemorySanitizerPass);
289   }
290 
291   if (LangOpts.Sanitize.Thread) {
292     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
293                            addThreadSanitizerPass);
294     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
295                            addThreadSanitizerPass);
296   }
297 
298   if (LangOpts.Sanitize.DataFlow) {
299     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
300                            addDataFlowSanitizerPass);
301     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
302                            addDataFlowSanitizerPass);
303   }
304 
305   // Figure out TargetLibraryInfo.
306   Triple TargetTriple(TheModule->getTargetTriple());
307   PMBuilder.LibraryInfo = createTLI(TargetTriple, CodeGenOpts);
308 
309   switch (Inlining) {
310   case CodeGenOptions::NoInlining: break;
311   case CodeGenOptions::NormalInlining: {
312     PMBuilder.Inliner =
313         createFunctionInliningPass(OptLevel, CodeGenOpts.OptimizeSize);
314     break;
315   }
316   case CodeGenOptions::OnlyAlwaysInlining:
317     // Respect always_inline.
318     if (OptLevel == 0)
319       // Do not insert lifetime intrinsics at -O0.
320       PMBuilder.Inliner = createAlwaysInlinerPass(false);
321     else
322       PMBuilder.Inliner = createAlwaysInlinerPass();
323     break;
324   }
325 
326   // Set up the per-function pass manager.
327   FunctionPassManager *FPM = getPerFunctionPasses();
328   if (CodeGenOpts.VerifyModule)
329     FPM->add(createVerifierPass());
330   PMBuilder.populateFunctionPassManager(*FPM);
331 
332   // Set up the per-module pass manager.
333   PassManager *MPM = getPerModulePasses();
334   if (CodeGenOpts.VerifyModule)
335     MPM->add(createDebugInfoVerifierPass());
336 
337   if (!CodeGenOpts.DisableGCov &&
338       (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes)) {
339     // Not using 'GCOVOptions::getDefault' allows us to avoid exiting if
340     // LLVM's -default-gcov-version flag is set to something invalid.
341     GCOVOptions Options;
342     Options.EmitNotes = CodeGenOpts.EmitGcovNotes;
343     Options.EmitData = CodeGenOpts.EmitGcovArcs;
344     memcpy(Options.Version, CodeGenOpts.CoverageVersion, 4);
345     Options.UseCfgChecksum = CodeGenOpts.CoverageExtraChecksum;
346     Options.NoRedZone = CodeGenOpts.DisableRedZone;
347     Options.FunctionNamesInData =
348         !CodeGenOpts.CoverageNoFunctionNamesInData;
349     MPM->add(createGCOVProfilerPass(Options));
350     if (CodeGenOpts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
351       MPM->add(createStripSymbolsPass(true));
352   }
353 
354   PMBuilder.populateModulePassManager(*MPM);
355 }
356 
357 TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
358   // Create the TargetMachine for generating code.
359   std::string Error;
360   std::string Triple = TheModule->getTargetTriple();
361   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
362   if (!TheTarget) {
363     if (MustCreateTM)
364       Diags.Report(diag::err_fe_unable_to_create_target) << Error;
365     return nullptr;
366   }
367 
368   unsigned CodeModel =
369     llvm::StringSwitch<unsigned>(CodeGenOpts.CodeModel)
370       .Case("small", llvm::CodeModel::Small)
371       .Case("kernel", llvm::CodeModel::Kernel)
372       .Case("medium", llvm::CodeModel::Medium)
373       .Case("large", llvm::CodeModel::Large)
374       .Case("default", llvm::CodeModel::Default)
375       .Default(~0u);
376   assert(CodeModel != ~0u && "invalid code model!");
377   llvm::CodeModel::Model CM = static_cast<llvm::CodeModel::Model>(CodeModel);
378 
379   SmallVector<const char *, 16> BackendArgs;
380   BackendArgs.push_back("clang"); // Fake program name.
381   if (!CodeGenOpts.DebugPass.empty()) {
382     BackendArgs.push_back("-debug-pass");
383     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
384   }
385   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
386     BackendArgs.push_back("-limit-float-precision");
387     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
388   }
389   if (llvm::TimePassesIsEnabled)
390     BackendArgs.push_back("-time-passes");
391   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
392     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
393   if (CodeGenOpts.NoGlobalMerge)
394     BackendArgs.push_back("-enable-global-merge=false");
395   BackendArgs.push_back(nullptr);
396   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
397                                     BackendArgs.data());
398 
399   std::string FeaturesStr;
400   if (TargetOpts.Features.size()) {
401     SubtargetFeatures Features;
402     for (std::vector<std::string>::const_iterator
403            it = TargetOpts.Features.begin(),
404            ie = TargetOpts.Features.end(); it != ie; ++it)
405       Features.AddFeature(*it);
406     FeaturesStr = Features.getString();
407   }
408 
409   llvm::Reloc::Model RM = llvm::Reloc::Default;
410   if (CodeGenOpts.RelocationModel == "static") {
411     RM = llvm::Reloc::Static;
412   } else if (CodeGenOpts.RelocationModel == "pic") {
413     RM = llvm::Reloc::PIC_;
414   } else {
415     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
416            "Invalid PIC model!");
417     RM = llvm::Reloc::DynamicNoPIC;
418   }
419 
420   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
421   switch (CodeGenOpts.OptimizationLevel) {
422   default: break;
423   case 0: OptLevel = CodeGenOpt::None; break;
424   case 3: OptLevel = CodeGenOpt::Aggressive; break;
425   }
426 
427   llvm::TargetOptions Options;
428 
429   Options.ThreadModel =
430     llvm::StringSwitch<llvm::ThreadModel::Model>(CodeGenOpts.ThreadModel)
431       .Case("posix", llvm::ThreadModel::POSIX)
432       .Case("single", llvm::ThreadModel::Single);
433 
434   if (CodeGenOpts.DisableIntegratedAS)
435     Options.DisableIntegratedAS = true;
436 
437   if (CodeGenOpts.CompressDebugSections)
438     Options.CompressDebugSections = true;
439 
440   // Set frame pointer elimination mode.
441   if (!CodeGenOpts.DisableFPElim) {
442     Options.NoFramePointerElim = false;
443   } else if (CodeGenOpts.OmitLeafFramePointer) {
444     Options.NoFramePointerElim = false;
445   } else {
446     Options.NoFramePointerElim = true;
447   }
448 
449   if (CodeGenOpts.UseInitArray)
450     Options.UseInitArray = true;
451 
452   // Set float ABI type.
453   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
454     Options.FloatABIType = llvm::FloatABI::Soft;
455   else if (CodeGenOpts.FloatABI == "hard")
456     Options.FloatABIType = llvm::FloatABI::Hard;
457   else {
458     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
459     Options.FloatABIType = llvm::FloatABI::Default;
460   }
461 
462   // Set FP fusion mode.
463   switch (CodeGenOpts.getFPContractMode()) {
464   case CodeGenOptions::FPC_Off:
465     Options.AllowFPOpFusion = llvm::FPOpFusion::Strict;
466     break;
467   case CodeGenOptions::FPC_On:
468     Options.AllowFPOpFusion = llvm::FPOpFusion::Standard;
469     break;
470   case CodeGenOptions::FPC_Fast:
471     Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
472     break;
473   }
474 
475   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
476   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
477   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
478   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
479   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
480   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
481   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
482   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
483   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
484   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
485   Options.FunctionSections = CodeGenOpts.FunctionSections;
486   Options.DataSections = CodeGenOpts.DataSections;
487 
488   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
489   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
490   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
491   Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
492   Options.MCOptions.MCFatalWarnings = CodeGenOpts.FatalWarnings;
493   Options.MCOptions.AsmVerbose = CodeGenOpts.AsmVerbose;
494 
495   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
496                                                      FeaturesStr, Options,
497                                                      RM, CM, OptLevel);
498 
499   return TM;
500 }
501 
502 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
503                                        formatted_raw_ostream &OS) {
504 
505   // Create the code generator passes.
506   PassManager *PM = getCodeGenPasses();
507 
508   // Add LibraryInfo.
509   llvm::Triple TargetTriple(TheModule->getTargetTriple());
510   PM->add(createTLI(TargetTriple, CodeGenOpts));
511 
512   // Add Target specific analysis passes.
513   TM->addAnalysisPasses(*PM);
514 
515   // Normal mode, emit a .s or .o file by running the code generator. Note,
516   // this also adds codegenerator level optimization passes.
517   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
518   if (Action == Backend_EmitObj)
519     CGFT = TargetMachine::CGFT_ObjectFile;
520   else if (Action == Backend_EmitMCNull)
521     CGFT = TargetMachine::CGFT_Null;
522   else
523     assert(Action == Backend_EmitAssembly && "Invalid action!");
524 
525   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
526   // "codegen" passes so that it isn't run multiple times when there is
527   // inlining happening.
528   if (LangOpts.ObjCAutoRefCount &&
529       CodeGenOpts.OptimizationLevel > 0)
530     PM->add(createObjCARCContractPass());
531 
532   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
533                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
534     Diags.Report(diag::err_fe_unable_to_interface_with_target);
535     return false;
536   }
537 
538   return true;
539 }
540 
541 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
542   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : nullptr);
543   llvm::formatted_raw_ostream FormattedOS;
544 
545   bool UsesCodeGen = (Action != Backend_EmitNothing &&
546                       Action != Backend_EmitBC &&
547                       Action != Backend_EmitLL);
548   if (!TM)
549     TM.reset(CreateTargetMachine(UsesCodeGen));
550 
551   if (UsesCodeGen && !TM) return;
552   CreatePasses();
553 
554   switch (Action) {
555   case Backend_EmitNothing:
556     break;
557 
558   case Backend_EmitBC:
559     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
560     break;
561 
562   case Backend_EmitLL:
563     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
564     getPerModulePasses()->add(createPrintModulePass(FormattedOS));
565     break;
566 
567   default:
568     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
569     if (!AddEmitPasses(Action, FormattedOS))
570       return;
571   }
572 
573   // Before executing passes, print the final values of the LLVM options.
574   cl::PrintOptionValues();
575 
576   // Run passes. For now we do all passes at once, but eventually we
577   // would like to have the option of streaming code generation.
578 
579   if (PerFunctionPasses) {
580     PrettyStackTraceString CrashInfo("Per-function optimization");
581 
582     PerFunctionPasses->doInitialization();
583     for (Module::iterator I = TheModule->begin(),
584            E = TheModule->end(); I != E; ++I)
585       if (!I->isDeclaration())
586         PerFunctionPasses->run(*I);
587     PerFunctionPasses->doFinalization();
588   }
589 
590   if (PerModulePasses) {
591     PrettyStackTraceString CrashInfo("Per-module optimization passes");
592     PerModulePasses->run(*TheModule);
593   }
594 
595   if (CodeGenPasses) {
596     PrettyStackTraceString CrashInfo("Code generation");
597     CodeGenPasses->run(*TheModule);
598   }
599 }
600 
601 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
602                               const CodeGenOptions &CGOpts,
603                               const clang::TargetOptions &TOpts,
604                               const LangOptions &LOpts, StringRef TDesc,
605                               Module *M, BackendAction Action,
606                               raw_ostream *OS) {
607   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);
608 
609   AsmHelper.EmitAssembly(Action, OS);
610 
611   // If an optional clang TargetInfo description string was passed in, use it to
612   // verify the LLVM TargetMachine's DataLayout.
613   if (AsmHelper.TM && !TDesc.empty()) {
614     std::string DLDesc = AsmHelper.TM->getSubtargetImpl()
615                              ->getDataLayout()
616                              ->getStringRepresentation();
617     if (DLDesc != TDesc) {
618       unsigned DiagID = Diags.getCustomDiagID(
619           DiagnosticsEngine::Error, "backend data layout '%0' does not match "
620                                     "expected target description '%1'");
621       Diags.Report(DiagID) << DLDesc << TDesc;
622     }
623   }
624 }
625