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/Transforms/IPO.h"
37 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
38 #include "llvm/Transforms/Instrumentation.h"
39 #include "llvm/Transforms/ObjCARC.h"
40 #include "llvm/Transforms/Scalar.h"
41 #include <memory>
42 using namespace clang;
43 using namespace llvm;
44 
45 namespace {
46 
47 class EmitAssemblyHelper {
48   DiagnosticsEngine &Diags;
49   const CodeGenOptions &CodeGenOpts;
50   const clang::TargetOptions &TargetOpts;
51   const LangOptions &LangOpts;
52   Module *TheModule;
53 
54   Timer CodeGenerationTime;
55 
56   mutable PassManager *CodeGenPasses;
57   mutable PassManager *PerModulePasses;
58   mutable FunctionPassManager *PerFunctionPasses;
59 
60 private:
61   PassManager *getCodeGenPasses() const {
62     if (!CodeGenPasses) {
63       CodeGenPasses = new PassManager();
64       CodeGenPasses->add(new DataLayoutPass(TheModule));
65       if (TM)
66         TM->addAnalysisPasses(*CodeGenPasses);
67     }
68     return CodeGenPasses;
69   }
70 
71   PassManager *getPerModulePasses() const {
72     if (!PerModulePasses) {
73       PerModulePasses = new PassManager();
74       PerModulePasses->add(new DataLayoutPass(TheModule));
75       if (TM)
76         TM->addAnalysisPasses(*PerModulePasses);
77     }
78     return PerModulePasses;
79   }
80 
81   FunctionPassManager *getPerFunctionPasses() const {
82     if (!PerFunctionPasses) {
83       PerFunctionPasses = new FunctionPassManager(TheModule);
84       PerFunctionPasses->add(new DataLayoutPass(TheModule));
85       if (TM)
86         TM->addAnalysisPasses(*PerFunctionPasses);
87     }
88     return PerFunctionPasses;
89   }
90 
91   void CreatePasses();
92 
93   /// CreateTargetMachine - Generates the TargetMachine.
94   /// Returns Null if it is unable to create the target machine.
95   /// Some of our clang tests specify triples which are not built
96   /// into clang. This is okay because these tests check the generated
97   /// IR, and they require DataLayout which depends on the triple.
98   /// In this case, we allow this method to fail and not report an error.
99   /// When MustCreateTM is used, we print an error if we are unable to load
100   /// the requested target.
101   TargetMachine *CreateTargetMachine(bool MustCreateTM);
102 
103   /// AddEmitPasses - Add passes necessary to emit assembly or LLVM IR.
104   ///
105   /// \return True on success.
106   bool AddEmitPasses(BackendAction Action, formatted_raw_ostream &OS);
107 
108 public:
109   EmitAssemblyHelper(DiagnosticsEngine &_Diags,
110                      const CodeGenOptions &CGOpts,
111                      const clang::TargetOptions &TOpts,
112                      const LangOptions &LOpts,
113                      Module *M)
114     : Diags(_Diags), CodeGenOpts(CGOpts), TargetOpts(TOpts), LangOpts(LOpts),
115       TheModule(M), CodeGenerationTime("Code Generation Time"),
116       CodeGenPasses(nullptr), PerModulePasses(nullptr),
117       PerFunctionPasses(nullptr) {}
118 
119   ~EmitAssemblyHelper() {
120     delete CodeGenPasses;
121     delete PerModulePasses;
122     delete PerFunctionPasses;
123     if (CodeGenOpts.DisableFree)
124       BuryPointer(TM.release());
125   }
126 
127   std::unique_ptr<TargetMachine> TM;
128 
129   void EmitAssembly(BackendAction Action, raw_ostream *OS);
130 };
131 
132 // We need this wrapper to access LangOpts and CGOpts from extension functions
133 // that we add to the PassManagerBuilder.
134 class PassManagerBuilderWrapper : public PassManagerBuilder {
135 public:
136   PassManagerBuilderWrapper(const CodeGenOptions &CGOpts,
137                             const LangOptions &LangOpts)
138       : PassManagerBuilder(), CGOpts(CGOpts), LangOpts(LangOpts) {}
139   const CodeGenOptions &getCGOpts() const { return CGOpts; }
140   const LangOptions &getLangOpts() const { return LangOpts; }
141 private:
142   const CodeGenOptions &CGOpts;
143   const LangOptions &LangOpts;
144 };
145 
146 }
147 
148 static void addObjCARCAPElimPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
149   if (Builder.OptLevel > 0)
150     PM.add(createObjCARCAPElimPass());
151 }
152 
153 static void addObjCARCExpandPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
154   if (Builder.OptLevel > 0)
155     PM.add(createObjCARCExpandPass());
156 }
157 
158 static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase &PM) {
159   if (Builder.OptLevel > 0)
160     PM.add(createObjCARCOptPass());
161 }
162 
163 static void addSampleProfileLoaderPass(const PassManagerBuilder &Builder,
164                                        PassManagerBase &PM) {
165   const PassManagerBuilderWrapper &BuilderWrapper =
166       static_cast<const PassManagerBuilderWrapper &>(Builder);
167   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
168   PM.add(createSampleProfileLoaderPass(CGOpts.SampleProfileFile));
169 }
170 
171 static void addAddDiscriminatorsPass(const PassManagerBuilder &Builder,
172                                      PassManagerBase &PM) {
173   PM.add(createAddDiscriminatorsPass());
174 }
175 
176 static void addBoundsCheckingPass(const PassManagerBuilder &Builder,
177                                     PassManagerBase &PM) {
178   PM.add(createBoundsCheckingPass());
179 }
180 
181 static void addAddressSanitizerPasses(const PassManagerBuilder &Builder,
182                                       PassManagerBase &PM) {
183   const PassManagerBuilderWrapper &BuilderWrapper =
184       static_cast<const PassManagerBuilderWrapper&>(Builder);
185   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
186   const LangOptions &LangOpts = BuilderWrapper.getLangOpts();
187   PM.add(createAddressSanitizerFunctionPass(
188       LangOpts.Sanitize.InitOrder,
189       LangOpts.Sanitize.UseAfterReturn,
190       LangOpts.Sanitize.UseAfterScope,
191       CGOpts.SanitizerBlacklistFile));
192   PM.add(createAddressSanitizerModulePass(
193       LangOpts.Sanitize.InitOrder,
194       CGOpts.SanitizerBlacklistFile));
195 }
196 
197 static void addMemorySanitizerPass(const PassManagerBuilder &Builder,
198                                    PassManagerBase &PM) {
199   const PassManagerBuilderWrapper &BuilderWrapper =
200       static_cast<const PassManagerBuilderWrapper&>(Builder);
201   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
202   PM.add(createMemorySanitizerPass(CGOpts.SanitizeMemoryTrackOrigins,
203                                    CGOpts.SanitizerBlacklistFile));
204 
205   // MemorySanitizer inserts complex instrumentation that mostly follows
206   // the logic of the original code, but operates on "shadow" values.
207   // It can benefit from re-running some general purpose optimization passes.
208   if (Builder.OptLevel > 0) {
209     PM.add(createEarlyCSEPass());
210     PM.add(createReassociatePass());
211     PM.add(createLICMPass());
212     PM.add(createGVNPass());
213     PM.add(createInstructionCombiningPass());
214     PM.add(createDeadStoreEliminationPass());
215   }
216 }
217 
218 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
219                                    PassManagerBase &PM) {
220   const PassManagerBuilderWrapper &BuilderWrapper =
221       static_cast<const PassManagerBuilderWrapper&>(Builder);
222   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
223   PM.add(createThreadSanitizerPass(CGOpts.SanitizerBlacklistFile));
224 }
225 
226 static void addDataFlowSanitizerPass(const PassManagerBuilder &Builder,
227                                      PassManagerBase &PM) {
228   const PassManagerBuilderWrapper &BuilderWrapper =
229       static_cast<const PassManagerBuilderWrapper&>(Builder);
230   const CodeGenOptions &CGOpts = BuilderWrapper.getCGOpts();
231   PM.add(createDataFlowSanitizerPass(CGOpts.SanitizerBlacklistFile));
232 }
233 
234 void EmitAssemblyHelper::CreatePasses() {
235   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
236   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.getInlining();
237 
238   // Handle disabling of LLVM optimization, where we want to preserve the
239   // internal module before any optimization.
240   if (CodeGenOpts.DisableLLVMOpts) {
241     OptLevel = 0;
242     Inlining = CodeGenOpts.NoInlining;
243   }
244 
245   PassManagerBuilderWrapper PMBuilder(CodeGenOpts, LangOpts);
246   PMBuilder.OptLevel = OptLevel;
247   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
248   PMBuilder.BBVectorize = CodeGenOpts.VectorizeBB;
249   PMBuilder.SLPVectorize = CodeGenOpts.VectorizeSLP;
250   PMBuilder.LoopVectorize = CodeGenOpts.VectorizeLoop;
251 
252   PMBuilder.DisableTailCalls = CodeGenOpts.DisableTailCalls;
253   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
254   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
255   PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;
256 
257   PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
258                          addAddDiscriminatorsPass);
259 
260   if (!CodeGenOpts.SampleProfileFile.empty())
261     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
262                            addSampleProfileLoaderPass);
263 
264   // In ObjC ARC mode, add the main ARC optimization passes.
265   if (LangOpts.ObjCAutoRefCount) {
266     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
267                            addObjCARCExpandPass);
268     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
269                            addObjCARCAPElimPass);
270     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
271                            addObjCARCOptPass);
272   }
273 
274   if (LangOpts.Sanitize.LocalBounds) {
275     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
276                            addBoundsCheckingPass);
277     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
278                            addBoundsCheckingPass);
279   }
280 
281   if (LangOpts.Sanitize.Address) {
282     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
283                            addAddressSanitizerPasses);
284     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
285                            addAddressSanitizerPasses);
286   }
287 
288   if (LangOpts.Sanitize.Memory) {
289     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
290                            addMemorySanitizerPass);
291     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
292                            addMemorySanitizerPass);
293   }
294 
295   if (LangOpts.Sanitize.Thread) {
296     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
297                            addThreadSanitizerPass);
298     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
299                            addThreadSanitizerPass);
300   }
301 
302   if (LangOpts.Sanitize.DataFlow) {
303     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
304                            addDataFlowSanitizerPass);
305     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
306                            addDataFlowSanitizerPass);
307   }
308 
309   // Figure out TargetLibraryInfo.
310   Triple TargetTriple(TheModule->getTargetTriple());
311   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
312   if (!CodeGenOpts.SimplifyLibCalls)
313     PMBuilder.LibraryInfo->disableAllFunctions();
314 
315   switch (Inlining) {
316   case CodeGenOptions::NoInlining: break;
317   case CodeGenOptions::NormalInlining: {
318     PMBuilder.Inliner =
319         createFunctionInliningPass(OptLevel, CodeGenOpts.OptimizeSize);
320     break;
321   }
322   case CodeGenOptions::OnlyAlwaysInlining:
323     // Respect always_inline.
324     if (OptLevel == 0)
325       // Do not insert lifetime intrinsics at -O0.
326       PMBuilder.Inliner = createAlwaysInlinerPass(false);
327     else
328       PMBuilder.Inliner = createAlwaysInlinerPass();
329     break;
330   }
331 
332   // Set up the per-function pass manager.
333   FunctionPassManager *FPM = getPerFunctionPasses();
334   if (CodeGenOpts.VerifyModule)
335     FPM->add(createVerifierPass());
336   PMBuilder.populateFunctionPassManager(*FPM);
337 
338   // Set up the per-module pass manager.
339   PassManager *MPM = getPerModulePasses();
340   if (CodeGenOpts.VerifyModule)
341     MPM->add(createDebugInfoVerifierPass());
342 
343   if (!CodeGenOpts.DisableGCov &&
344       (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes)) {
345     // Not using 'GCOVOptions::getDefault' allows us to avoid exiting if
346     // LLVM's -default-gcov-version flag is set to something invalid.
347     GCOVOptions Options;
348     Options.EmitNotes = CodeGenOpts.EmitGcovNotes;
349     Options.EmitData = CodeGenOpts.EmitGcovArcs;
350     memcpy(Options.Version, CodeGenOpts.CoverageVersion, 4);
351     Options.UseCfgChecksum = CodeGenOpts.CoverageExtraChecksum;
352     Options.NoRedZone = CodeGenOpts.DisableRedZone;
353     Options.FunctionNamesInData =
354         !CodeGenOpts.CoverageNoFunctionNamesInData;
355     MPM->add(createGCOVProfilerPass(Options));
356     if (CodeGenOpts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
357       MPM->add(createStripSymbolsPass(true));
358   }
359 
360   PMBuilder.populateModulePassManager(*MPM);
361 }
362 
363 TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
364   // Create the TargetMachine for generating code.
365   std::string Error;
366   std::string Triple = TheModule->getTargetTriple();
367   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
368   if (!TheTarget) {
369     if (MustCreateTM)
370       Diags.Report(diag::err_fe_unable_to_create_target) << Error;
371     return nullptr;
372   }
373 
374   unsigned CodeModel =
375     llvm::StringSwitch<unsigned>(CodeGenOpts.CodeModel)
376       .Case("small", llvm::CodeModel::Small)
377       .Case("kernel", llvm::CodeModel::Kernel)
378       .Case("medium", llvm::CodeModel::Medium)
379       .Case("large", llvm::CodeModel::Large)
380       .Case("default", llvm::CodeModel::Default)
381       .Default(~0u);
382   assert(CodeModel != ~0u && "invalid code model!");
383   llvm::CodeModel::Model CM = static_cast<llvm::CodeModel::Model>(CodeModel);
384 
385   SmallVector<const char *, 16> BackendArgs;
386   BackendArgs.push_back("clang"); // Fake program name.
387   if (!CodeGenOpts.DebugPass.empty()) {
388     BackendArgs.push_back("-debug-pass");
389     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
390   }
391   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
392     BackendArgs.push_back("-limit-float-precision");
393     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
394   }
395   if (llvm::TimePassesIsEnabled)
396     BackendArgs.push_back("-time-passes");
397   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
398     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
399   if (CodeGenOpts.NoGlobalMerge)
400     BackendArgs.push_back("-global-merge=false");
401   BackendArgs.push_back(nullptr);
402   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
403                                     BackendArgs.data());
404 
405   std::string FeaturesStr;
406   if (TargetOpts.Features.size()) {
407     SubtargetFeatures Features;
408     for (std::vector<std::string>::const_iterator
409            it = TargetOpts.Features.begin(),
410            ie = TargetOpts.Features.end(); it != ie; ++it)
411       Features.AddFeature(*it);
412     FeaturesStr = Features.getString();
413   }
414 
415   llvm::Reloc::Model RM = llvm::Reloc::Default;
416   if (CodeGenOpts.RelocationModel == "static") {
417     RM = llvm::Reloc::Static;
418   } else if (CodeGenOpts.RelocationModel == "pic") {
419     RM = llvm::Reloc::PIC_;
420   } else {
421     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
422            "Invalid PIC model!");
423     RM = llvm::Reloc::DynamicNoPIC;
424   }
425 
426   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
427   switch (CodeGenOpts.OptimizationLevel) {
428   default: break;
429   case 0: OptLevel = CodeGenOpt::None; break;
430   case 3: OptLevel = CodeGenOpt::Aggressive; break;
431   }
432 
433   llvm::TargetOptions Options;
434 
435   if (CodeGenOpts.DisableIntegratedAS)
436     Options.DisableIntegratedAS = true;
437 
438   if (CodeGenOpts.CompressDebugSections)
439     Options.CompressDebugSections = true;
440 
441   // Set frame pointer elimination mode.
442   if (!CodeGenOpts.DisableFPElim) {
443     Options.NoFramePointerElim = false;
444   } else if (CodeGenOpts.OmitLeafFramePointer) {
445     Options.NoFramePointerElim = false;
446   } else {
447     Options.NoFramePointerElim = true;
448   }
449 
450   if (CodeGenOpts.UseInitArray)
451     Options.UseInitArray = true;
452 
453   // Set float ABI type.
454   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
455     Options.FloatABIType = llvm::FloatABI::Soft;
456   else if (CodeGenOpts.FloatABI == "hard")
457     Options.FloatABIType = llvm::FloatABI::Hard;
458   else {
459     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
460     Options.FloatABIType = llvm::FloatABI::Default;
461   }
462 
463   // Set FP fusion mode.
464   switch (CodeGenOpts.getFPContractMode()) {
465   case CodeGenOptions::FPC_Off:
466     Options.AllowFPOpFusion = llvm::FPOpFusion::Strict;
467     break;
468   case CodeGenOptions::FPC_On:
469     Options.AllowFPOpFusion = llvm::FPOpFusion::Standard;
470     break;
471   case CodeGenOptions::FPC_Fast:
472     Options.AllowFPOpFusion = llvm::FPOpFusion::Fast;
473     break;
474   }
475 
476   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
477   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
478   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
479   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
480   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
481   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
482   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
483   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
484   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
485   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
486   Options.FunctionSections = CodeGenOpts.FunctionSections;
487   Options.DataSections = CodeGenOpts.DataSections;
488 
489   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
490   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
491   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;
492   Options.MCOptions.MCNoExecStack = CodeGenOpts.NoExecStack;
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   TargetLibraryInfo *TLI = new TargetLibraryInfo(TargetTriple);
511   if (!CodeGenOpts.SimplifyLibCalls)
512     TLI->disableAllFunctions();
513   PM->add(TLI);
514 
515   // Add Target specific analysis passes.
516   TM->addAnalysisPasses(*PM);
517 
518   // Normal mode, emit a .s or .o file by running the code generator. Note,
519   // this also adds codegenerator level optimization passes.
520   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
521   if (Action == Backend_EmitObj)
522     CGFT = TargetMachine::CGFT_ObjectFile;
523   else if (Action == Backend_EmitMCNull)
524     CGFT = TargetMachine::CGFT_Null;
525   else
526     assert(Action == Backend_EmitAssembly && "Invalid action!");
527 
528   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
529   // "codegen" passes so that it isn't run multiple times when there is
530   // inlining happening.
531   if (LangOpts.ObjCAutoRefCount &&
532       CodeGenOpts.OptimizationLevel > 0)
533     PM->add(createObjCARCContractPass());
534 
535   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
536                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
537     Diags.Report(diag::err_fe_unable_to_interface_with_target);
538     return false;
539   }
540 
541   return true;
542 }
543 
544 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
545   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : nullptr);
546   llvm::formatted_raw_ostream FormattedOS;
547 
548   bool UsesCodeGen = (Action != Backend_EmitNothing &&
549                       Action != Backend_EmitBC &&
550                       Action != Backend_EmitLL);
551   if (!TM)
552     TM.reset(CreateTargetMachine(UsesCodeGen));
553 
554   if (UsesCodeGen && !TM) return;
555   CreatePasses();
556 
557   switch (Action) {
558   case Backend_EmitNothing:
559     break;
560 
561   case Backend_EmitBC:
562     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
563     break;
564 
565   case Backend_EmitLL:
566     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
567     getPerModulePasses()->add(createPrintModulePass(FormattedOS));
568     break;
569 
570   default:
571     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
572     if (!AddEmitPasses(Action, FormattedOS))
573       return;
574   }
575 
576   // Before executing passes, print the final values of the LLVM options.
577   cl::PrintOptionValues();
578 
579   // Run passes. For now we do all passes at once, but eventually we
580   // would like to have the option of streaming code generation.
581 
582   if (PerFunctionPasses) {
583     PrettyStackTraceString CrashInfo("Per-function optimization");
584 
585     PerFunctionPasses->doInitialization();
586     for (Module::iterator I = TheModule->begin(),
587            E = TheModule->end(); I != E; ++I)
588       if (!I->isDeclaration())
589         PerFunctionPasses->run(*I);
590     PerFunctionPasses->doFinalization();
591   }
592 
593   if (PerModulePasses) {
594     PrettyStackTraceString CrashInfo("Per-module optimization passes");
595     PerModulePasses->run(*TheModule);
596   }
597 
598   if (CodeGenPasses) {
599     PrettyStackTraceString CrashInfo("Code generation");
600     CodeGenPasses->run(*TheModule);
601   }
602 }
603 
604 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
605                               const CodeGenOptions &CGOpts,
606                               const clang::TargetOptions &TOpts,
607                               const LangOptions &LOpts, StringRef TDesc,
608                               Module *M, BackendAction Action,
609                               raw_ostream *OS) {
610   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);
611 
612   AsmHelper.EmitAssembly(Action, OS);
613 
614   // If an optional clang TargetInfo description string was passed in, use it to
615   // verify the LLVM TargetMachine's DataLayout.
616   if (AsmHelper.TM && !TDesc.empty()) {
617     std::string DLDesc =
618         AsmHelper.TM->getDataLayout()->getStringRepresentation();
619     if (DLDesc != TDesc) {
620       unsigned DiagID = Diags.getCustomDiagID(
621           DiagnosticsEngine::Error, "backend data layout '%0' does not match "
622                                     "expected target description '%1'");
623       Diags.Report(DiagID) << DLDesc << TDesc;
624     }
625   }
626 }
627