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