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/Bitcode/BitcodeWriterPass.h"
18 #include "llvm/CodeGen/RegAllocRegistry.h"
19 #include "llvm/CodeGen/SchedulerRegistry.h"
20 #include "llvm/IR/DataLayout.h"
21 #include "llvm/IR/IRPrintingPasses.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/IR/Verifier.h"
24 #include "llvm/MC/SubtargetFeature.h"
25 #include "llvm/PassManager.h"
26 #include "llvm/Support/CommandLine.h"
27 #include "llvm/Support/FormattedStream.h"
28 #include "llvm/Support/PrettyStackTrace.h"
29 #include "llvm/Support/TargetRegistry.h"
30 #include "llvm/Support/Timer.h"
31 #include "llvm/Support/raw_ostream.h"
32 #include "llvm/Target/TargetLibraryInfo.h"
33 #include "llvm/Target/TargetMachine.h"
34 #include "llvm/Target/TargetOptions.h"
35 #include "llvm/Transforms/IPO.h"
36 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
37 #include "llvm/Transforms/Instrumentation.h"
38 #include "llvm/Transforms/ObjCARC.h"
39 #include "llvm/Transforms/Scalar.h"
40 #include <memory>
41 using namespace clang;
42 using namespace llvm;
43 
44 namespace {
45 
46 class EmitAssemblyHelper {
47   DiagnosticsEngine &Diags;
48   const CodeGenOptions &CodeGenOpts;
49   const clang::TargetOptions &TargetOpts;
50   const LangOptions &LangOpts;
51   Module *TheModule;
52 
53   Timer CodeGenerationTime;
54 
55   mutable PassManager *CodeGenPasses;
56   mutable PassManager *PerModulePasses;
57   mutable FunctionPassManager *PerFunctionPasses;
58 
59 private:
60   PassManager *getCodeGenPasses() const {
61     if (!CodeGenPasses) {
62       CodeGenPasses = new PassManager();
63       CodeGenPasses->add(new DataLayoutPass(TheModule));
64       if (TM)
65         TM->addAnalysisPasses(*CodeGenPasses);
66     }
67     return CodeGenPasses;
68   }
69 
70   PassManager *getPerModulePasses() const {
71     if (!PerModulePasses) {
72       PerModulePasses = new PassManager();
73       PerModulePasses->add(new DataLayoutPass(TheModule));
74       if (TM)
75         TM->addAnalysisPasses(*PerModulePasses);
76     }
77     return PerModulePasses;
78   }
79 
80   FunctionPassManager *getPerFunctionPasses() const {
81     if (!PerFunctionPasses) {
82       PerFunctionPasses = new FunctionPassManager(TheModule);
83       PerFunctionPasses->add(new DataLayoutPass(TheModule));
84       if (TM)
85         TM->addAnalysisPasses(*PerFunctionPasses);
86     }
87     return PerFunctionPasses;
88   }
89 
90   void CreatePasses();
91 
92   /// CreateTargetMachine - Generates the TargetMachine.
93   /// Returns Null if it is unable to create the target machine.
94   /// Some of our clang tests specify triples which are not built
95   /// into clang. This is okay because these tests check the generated
96   /// IR, and they require DataLayout which depends on the triple.
97   /// In this case, we allow this method to fail and not report an error.
98   /// When MustCreateTM is used, we print an error if we are unable to load
99   /// the requested target.
100   TargetMachine *CreateTargetMachine(bool MustCreateTM);
101 
102   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
103   ///
104   /// \return True on success.
105   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);
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     if (CodeGenOpts.DisableFree)
122       BuryPointer(TM.release());
123   }
124 
125   std::unique_ptr<TargetMachine> TM;
126 
127   void EmitAssembly(BackendAction Action, raw_ostream *OS);
128 };
129 
130 // We need this wrapper to access LangOpts and CGOpts from extension functions
131 // that we add to the PassManagerBuilder.
132 class PassManagerBuilderWrapper : public PassManagerBuilder {
133 public:
134   PassManagerBuilderWrapper(const CodeGenOptions &CGOpts,
135                             const LangOptions &LangOpts)
136       : PassManagerBuilder(), CGOpts(CGOpts), LangOpts(LangOpts) {}
137   const CodeGenOptions &getCGOpts() const { return CGOpts; }
138   const LangOptions &getLangOpts() const { return LangOpts; }
139 private:
140   const CodeGenOptions &CGOpts;
141   const LangOptions &LangOpts;
142 };
143 
144 }
145 
146 static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
147   if (Builder.OptLevel > 0)
148     PM.add(createObjCARCAPElimPass());
149 }
150 
151 static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
152   if (Builder.OptLevel > 0)
153     PM.add(createObjCARCExpandPass());
154 }
155 
156 static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
157   if (Builder.OptLevel > 0)
158     PM.add(createObjCARCOptPass());
159 }
160 
161 static void addSampleProfileLoaderPass(const PassManagerBuilder &Builder,
162                                        PassManagerBase &PM) {
163   const PassManagerBuilderWrapper &BuilderWrapper =
164       static_cast<const PassManagerBuilderWrapper &>(Builder);
165   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
166   PM.add(createSampleProfileLoaderPass(CGOpts.SampleProfileFile));
167 }
168 
169 static void addAddDiscriminatorsPass(const PassManagerBuilder &Builder,
170                                      PassManagerBase &PM) {
171   PM.add(createAddDiscriminatorsPass());
172 }
173 
174 static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
175                                     PassManagerBase &PM) {
176   PM.add(createBoundsCheckingPass());
177 }
178 
179 static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
180                                       PassManagerBase &PM) {
181   const PassManagerBuilderWrapper &BuilderWrapper =
182       static_cast<const PassManagerBuilderWrapper&>(Builder);
183   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
184   const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
185   PM.add(createAddressSanitizerFunctionPass(
186       LangOpts.Sanitize.InitOrder,
187       LangOpts.Sanitize.UseAfterReturn,
188       LangOpts.Sanitize.UseAfterScope,
189       CGOpts.SanitizerBlacklistFile));
190   PM.add(createAddressSanitizerModulePass(
191       LangOpts.Sanitize.InitOrder,
192       CGOpts.SanitizerBlacklistFile));
193 }
194 
195 static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
196                                    PassManagerBase &PM) {
197   const PassManagerBuilderWrapper &BuilderWrapper =
198       static_cast<const PassManagerBuilderWrapper&>(Builder);
199   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
200   PM.add(createMemorySanitizerPass(CGOpts.SanitizeMemoryTrackOrigins,
201                                    CGOpts.SanitizerBlacklistFile));
202 
203   // MemorySanitizer inserts complex instrumentation that mostly follows
204   // the logic of the original code, but operates on "shadow" values.
205   // It can benefit from re-running some general purpose optimization passes.
206   if (Builder.OptLevel > 0) {
207     PM.add(createEarlyCSEPass());
208     PM.add(createReassociatePass());
209     PM.add(createLICMPass());
210     PM.add(createGVNPass());
211     PM.add(createInstructionCombiningPass());
212     PM.add(createDeadStoreEliminationPass());
213   }
214 }
215 
216 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
217                                    PassManagerBase &PM) {
218   const PassManagerBuilderWrapper &BuilderWrapper =
219       static_cast<const PassManagerBuilderWrapper&>(Builder);
220   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
221   PM.add(createThreadSanitizerPass(CGOpts.SanitizerBlacklistFile));
222 }
223 
224 static void addDataFlowSanitizerPass(const PassManagerBuilder &Builder,
225                                      PassManagerBase &PM) {
226   const PassManagerBuilderWrapper &BuilderWrapper =
227       static_cast<const PassManagerBuilderWrapper&>(Builder);
228   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
229   PM.add(createDataFlowSanitizerPass(CGOpts.SanitizerBlacklistFile));
230 }
231 
232 void EmitAssemblyHelper::CreatePasses() {
233   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
234   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.getInlining();
235 
236   // Handle disabling of LLVM optimization, where we want to preserve the
237   // internal module before any optimization.
238   if (CodeGenOpts.DisableLLVMOpts) {
239     OptLevel = 0;
240     Inlining = CodeGenOpts.NoInlining;
241   }
242 
243   PassManagerBuilderWrapper PMBuilder(CodeGenOpts, LangOpts);
244   PMBuilder.OptLevel = OptLevel;
245   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
246   PMBuilder.BBVectorize = CodeGenOpts.VectorizeBB;
247   PMBuilder.SLPVectorize = CodeGenOpts.VectorizeSLP;
248   PMBuilder.LoopVectorize = CodeGenOpts.VectorizeLoop;
249 
250   PMBuilder.DisableTailCalls = CodeGenOpts.DisableTailCalls;
251   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
252   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
253   PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
254 
255   PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
256                          addAddDiscriminatorsPass);
257 
258   if (!CodeGenOpts.SampleProfileFile.empty())
259     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
260                            addSampleProfileLoaderPass);
261 
262   // In ObjC ARC mode, add the main ARC optimization passes.
263   if (LangOpts.ObjCAutoRefCount) {
264     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
265                            addObjCARCExpandPass);
266     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
267                            addObjCARCAPElimPass);
268     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
269                            addObjCARCOptPass);
270   }
271 
272   if (LangOpts.Sanitize.LocalBounds) {
273     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
274                            addBoundsCheckingPass);
275     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
276                            addBoundsCheckingPass);
277   }
278 
279   if (LangOpts.Sanitize.Address) {
280     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
281                            addAddressSanitizerPasses);
282     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
283                            addAddressSanitizerPasses);
284   }
285 
286   if (LangOpts.Sanitize.Memory) {
287     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
288                            addMemorySanitizerPass);
289     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
290                            addMemorySanitizerPass);
291   }
292 
293   if (LangOpts.Sanitize.Thread) {
294     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
295                            addThreadSanitizerPass);
296     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
297                            addThreadSanitizerPass);
298   }
299 
300   if (LangOpts.Sanitize.DataFlow) {
301     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
302                            addDataFlowSanitizerPass);
303     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
304                            addDataFlowSanitizerPass);
305   }
306 
307   // Figure out TargetLibraryInfo.
308   Triple TargetTriple(TheModule->getTargetTriple());
309   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
310   if (!CodeGenOpts.SimplifyLibCalls)
311     PMBuilder.LibraryInfo->disableAllFunctions();
312 
313   switch (Inlining) {
314   case CodeGenOptions::NoInlining: break;
315   case CodeGenOptions::NormalInlining: {
316     PMBuilder.Inliner =
317         createFunctionInliningPass(OptLevel, CodeGenOpts.OptimizeSize);
318     break;
319   }
320   case CodeGenOptions::OnlyAlwaysInlining:
321     // Respect always_inline.
322     if (OptLevel == 0)
323       // Do not insert lifetime intrinsics at -O0.
324       PMBuilder.Inliner = createAlwaysInlinerPass(false);
325     else
326       PMBuilder.Inliner = createAlwaysInlinerPass();
327     break;
328   }
329 
330   // Set up the per-function pass manager.
331   FunctionPassManager *FPM = getPerFunctionPasses();
332   if (CodeGenOpts.VerifyModule)
333     FPM->add(createVerifierPass());
334   PMBuilder.populateFunctionPassManager(*FPM);
335 
336   // Set up the per-module pass manager.
337   PassManager *MPM = getPerModulePasses();
338   if (CodeGenOpts.VerifyModule)
339     MPM->add(createDebugInfoVerifierPass());
340 
341   if (!CodeGenOpts.DisableGCov &&
342       (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes)) {
343     // Not using 'GCOVOptions::getDefault' allows us to avoid exiting if
344     // LLVM's -default-gcov-version flag is set to something invalid.
345     GCOVOptions Options;
346     Options.EmitNotes = CodeGenOpts.EmitGcovNotes;
347     Options.EmitData = CodeGenOpts.EmitGcovArcs;
348     memcpy(Options.Version, CodeGenOpts.CoverageVersion, 4);
349     Options.UseCfgChecksum = CodeGenOpts.CoverageExtraChecksum;
350     Options.NoRedZone = CodeGenOpts.DisableRedZone;
351     Options.FunctionNamesInData =
352         !CodeGenOpts.CoverageNoFunctionNamesInData;
353     MPM->add(createGCOVProfilerPass(Options));
354     if (CodeGenOpts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
355       MPM->add(createStripSymbolsPass(true));
356   }
357 
358   PMBuilder.populateModulePassManager(*MPM);
359 }
360 
361 TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
362   // Create the TargetMachine for generating code.
363   std::string Error;
364   std::string Triple = TheModule->getTargetTriple();
365   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
366   if (!TheTarget) {
367     if (MustCreateTM)
368       Diags.Report(diag::err_fe_unable_to_create_target) << Error;
369     return 0;
370   }
371 
372   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
373   // being gross, this is also totally broken if we ever care about
374   // concurrency.
375 
376   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
377 
378   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
379   TargetMachine::setDataSections    (CodeGenOpts.DataSections);
380 
381   // FIXME: Parse this earlier.
382   llvm::CodeModel::Model CM;
383   if (CodeGenOpts.CodeModel == "small") {
384     CM = llvm::CodeModel::Small;
385   } else if (CodeGenOpts.CodeModel == "kernel") {
386     CM = llvm::CodeModel::Kernel;
387   } else if (CodeGenOpts.CodeModel == "medium") {
388     CM = llvm::CodeModel::Medium;
389   } else if (CodeGenOpts.CodeModel == "large") {
390     CM = llvm::CodeModel::Large;
391   } else {
392     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
393     CM = llvm::CodeModel::Default;
394   }
395 
396   SmallVector<const char *, 16> BackendArgs;
397   BackendArgs.push_back("clang"); // Fake program name.
398   if (!CodeGenOpts.DebugPass.empty()) {
399     BackendArgs.push_back("-debug-pass");
400     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
401   }
402   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
403     BackendArgs.push_back("-limit-float-precision");
404     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
405   }
406   if (llvm::TimePassesIsEnabled)
407     BackendArgs.push_back("-time-passes");
408   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
409     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
410   if (CodeGenOpts.NoGlobalMerge)
411     BackendArgs.push_back("-global-merge=false");
412   BackendArgs.push_back(0);
413   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
414                                     BackendArgs.data());
415 
416   std::string FeaturesStr;
417   if (TargetOpts.Features.size()) {
418     SubtargetFeatures Features;
419     for (std::vector<std::string>::const_iterator
420            it = TargetOpts.Features.begin(),
421            ie = TargetOpts.Features.end(); it != ie; ++it)
422       Features.AddFeature(*it);
423     FeaturesStr = Features.getString();
424   }
425 
426   llvm::Reloc::Model RM = llvm::Reloc::Default;
427   if (CodeGenOpts.RelocationModel == "static") {
428     RM = llvm::Reloc::Static;
429   } else if (CodeGenOpts.RelocationModel == "pic") {
430     RM = llvm::Reloc::PIC_;
431   } else {
432     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
433            "Invalid PIC model!");
434     RM = llvm::Reloc::DynamicNoPIC;
435   }
436 
437   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
438   switch (CodeGenOpts.OptimizationLevel) {
439   default: break;
440   case 0: OptLevel = CodeGenOpt::None; break;
441   case 3: OptLevel = CodeGenOpt::Aggressive; break;
442   }
443 
444   llvm::TargetOptions Options;
445 
446   if (CodeGenOpts.DisableIntegratedAS)
447     Options.DisableIntegratedAS = true;
448 
449   if (CodeGenOpts.CompressDebugSections)
450     Options.CompressDebugSections = true;
451 
452   // Set frame pointer elimination mode.
453   if (!CodeGenOpts.DisableFPElim) {
454     Options.NoFramePointerElim = false;
455   } else if (CodeGenOpts.OmitLeafFramePointer) {
456     Options.NoFramePointerElim = false;
457   } else {
458     Options.NoFramePointerElim = true;
459   }
460 
461   if (CodeGenOpts.UseInitArray)
462     Options.UseInitArray = true;
463 
464   // Set float ABI type.
465   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
466     Options.FloatABIType = llvm::FloatABI::Soft;
467   else if (CodeGenOpts.FloatABI == "hard")
468     Options.FloatABIType = llvm::FloatABI::Hard;
469   else {
470     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
471     Options.FloatABIType = llvm::FloatABI::Default;
472   }
473 
474   // Set FP fusion mode.
475   switch (CodeGenOpts.getFPContractMode()) {
476   case CodeGenOptions::FPC_Off:
477     Options.AllowFPOpFusion = llvm::FPOpFusion::Strict;
478     break;
479   case CodeGenOptions::FPC_On:
480     Options.AllowFPOpFusion = llvm::FPOpFusion::Standard;
481     break;
482   case CodeGenOptions::FPC_Fast:
483     Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
484     break;
485   }
486 
487   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
488   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
489   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
490   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
491   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
492   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
493   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
494   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
495   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
496   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
497 
498   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
499                                                      FeaturesStr, Options,
500                                                      RM, CM, OptLevel);
501 
502   if (CodeGenOpts.RelaxAll)
503     TM->setMCRelaxAll(true);
504   if (CodeGenOpts.SaveTempLabels)
505     TM->setMCSaveTempLabels(true);
506   if (!CodeGenOpts.NoDwarfDirectoryAsm)
507     TM->setMCUseDwarfDirectory(true);
508   if (CodeGenOpts.NoExecStack)
509     TM->setMCNoExecStack(true);
510 
511   return TM;
512 }
513 
514 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
515                                        formatted_raw_ostream &OS) {
516 
517   // Create the code generator passes.
518   PassManager *PM = getCodeGenPasses();
519 
520   // Add LibraryInfo.
521   llvm::Triple TargetTriple(TheModule->getTargetTriple());
522   TargetLibraryInfo *TLI = new TargetLibraryInfo(TargetTriple);
523   if (!CodeGenOpts.SimplifyLibCalls)
524     TLI->disableAllFunctions();
525   PM->add(TLI);
526 
527   // Add Target specific analysis passes.
528   TM->addAnalysisPasses(*PM);
529 
530   // Normal mode, emit a .s or .o file by running the code generator. Note,
531   // this also adds codegenerator level optimization passes.
532   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
533   if (Action == Backend_EmitObj)
534     CGFT = TargetMachine::CGFT_ObjectFile;
535   else if (Action == Backend_EmitMCNull)
536     CGFT = TargetMachine::CGFT_Null;
537   else
538     assert(Action == Backend_EmitAssembly && "Invalid action!");
539 
540   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
541   // "codegen" passes so that it isn't run multiple times when there is
542   // inlining happening.
543   if (LangOpts.ObjCAutoRefCount &&
544       CodeGenOpts.OptimizationLevel > 0)
545     PM->add(createObjCARCContractPass());
546 
547   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
548                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
549     Diags.Report(diag::err_fe_unable_to_interface_with_target);
550     return false;
551   }
552 
553   return true;
554 }
555 
556 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
557   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
558   llvm::formatted_raw_ostream FormattedOS;
559 
560   bool UsesCodeGen = (Action != Backend_EmitNothing &&
561                       Action != Backend_EmitBC &&
562                       Action != Backend_EmitLL);
563   if (!TM)
564     TM.reset(CreateTargetMachine(UsesCodeGen));
565 
566   if (UsesCodeGen && !TM) return;
567   CreatePasses();
568 
569   switch (Action) {
570   case Backend_EmitNothing:
571     break;
572 
573   case Backend_EmitBC:
574     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
575     break;
576 
577   case Backend_EmitLL:
578     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
579     getPerModulePasses()->add(createPrintModulePass(FormattedOS));
580     break;
581 
582   default:
583     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
584     if (!AddEmitPasses(Action, FormattedOS))
585       return;
586   }
587 
588   // Before executing passes, print the final values of the LLVM options.
589   cl::PrintOptionValues();
590 
591   // Run passes. For now we do all passes at once, but eventually we
592   // would like to have the option of streaming code generation.
593 
594   if (PerFunctionPasses) {
595     PrettyStackTraceString CrashInfo("Per-function optimization");
596 
597     PerFunctionPasses->doInitialization();
598     for (Module::iterator I = TheModule->begin(),
599            E = TheModule->end(); I != E; ++I)
600       if (!I->isDeclaration())
601         PerFunctionPasses->run(*I);
602     PerFunctionPasses->doFinalization();
603   }
604 
605   if (PerModulePasses) {
606     PrettyStackTraceString CrashInfo("Per-module optimization passes");
607     PerModulePasses->run(*TheModule);
608   }
609 
610   if (CodeGenPasses) {
611     PrettyStackTraceString CrashInfo("Code generation");
612     CodeGenPasses->run(*TheModule);
613   }
614 }
615 
616 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
617                               const CodeGenOptions &CGOpts,
618                               const clang::TargetOptions &TOpts,
619                               const LangOptions &LOpts, StringRef TDesc,
620                               Module *M, BackendAction Action,
621                               raw_ostream *OS) {
622   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);
623 
624   AsmHelper.EmitAssembly(Action, OS);
625 
626   // If an optional clang TargetInfo description string was passed in, use it to
627   // verify the LLVM TargetMachine's DataLayout.
628   if (AsmHelper.TM && !TDesc.empty()) {
629     std::string DLDesc =
630         AsmHelper.TM->getDataLayout()->getStringRepresentation();
631     if (DLDesc != TDesc) {
632       unsigned DiagID = Diags.getCustomDiagID(
633           DiagnosticsEngine::Error, "backend data layout '%0' does not match "
634                                     "expected target description '%1'");
635       Diags.Report(DiagID) << DLDesc << TDesc;
636     }
637   }
638 }
639