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      1 //===--- BackendUtil.cpp - LLVM Backend Utilities -------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 
     10 #include "clang/CodeGen/BackendUtil.h"
     11 #include "clang/Basic/Diagnostic.h"
     12 #include "clang/Basic/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 void addAddressSanitizerPass(const PassManagerBuilder &Builder,
    125                                     PassManagerBase &PM) {
    126   PM.add(createAddressSanitizerPass());
    127 }
    128 
    129 static void addThreadSanitizerPass(const PassManagerBuilder &Builder,
    130                                    PassManagerBase &PM) {
    131   PM.add(createThreadSanitizerPass());
    132 }
    133 
    134 void EmitAssemblyHelper::CreatePasses() {
    135   unsigned OptLevel = CodeGenOpts.OptimizationLevel;
    136   CodeGenOptions::InliningMethod Inlining = CodeGenOpts.Inlining;
    137 
    138   // Handle disabling of LLVM optimization, where we want to preserve the
    139   // internal module before any optimization.
    140   if (CodeGenOpts.DisableLLVMOpts) {
    141     OptLevel = 0;
    142     Inlining = CodeGenOpts.NoInlining;
    143   }
    144 
    145   PassManagerBuilder PMBuilder;
    146   PMBuilder.OptLevel = OptLevel;
    147   PMBuilder.SizeLevel = CodeGenOpts.OptimizeSize;
    148 
    149   PMBuilder.DisableSimplifyLibCalls = !CodeGenOpts.SimplifyLibCalls;
    150   PMBuilder.DisableUnitAtATime = !CodeGenOpts.UnitAtATime;
    151   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
    152 
    153   // In ObjC ARC mode, add the main ARC optimization passes.
    154   if (LangOpts.ObjCAutoRefCount) {
    155     PMBuilder.addExtension(PassManagerBuilder::EP_EarlyAsPossible,
    156                            addObjCARCExpandPass);
    157     PMBuilder.addExtension(PassManagerBuilder::EP_ModuleOptimizerEarly,
    158                            addObjCARCAPElimPass);
    159     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
    160                            addObjCARCOptPass);
    161   }
    162 
    163   if (LangOpts.AddressSanitizer) {
    164     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
    165                            addAddressSanitizerPass);
    166     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    167                            addAddressSanitizerPass);
    168   }
    169 
    170   if (LangOpts.ThreadSanitizer) {
    171     PMBuilder.addExtension(PassManagerBuilder::EP_OptimizerLast,
    172                            addThreadSanitizerPass);
    173     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,
    174                            addThreadSanitizerPass);
    175   }
    176 
    177   // Figure out TargetLibraryInfo.
    178   Triple TargetTriple(TheModule->getTargetTriple());
    179   PMBuilder.LibraryInfo = new TargetLibraryInfo(TargetTriple);
    180   if (!CodeGenOpts.SimplifyLibCalls)
    181     PMBuilder.LibraryInfo->disableAllFunctions();
    182 
    183   switch (Inlining) {
    184   case CodeGenOptions::NoInlining: break;
    185   case CodeGenOptions::NormalInlining: {
    186     // FIXME: Derive these constants in a principled fashion.
    187     unsigned Threshold = 225;
    188     if (CodeGenOpts.OptimizeSize == 1)      // -Os
    189       Threshold = 75;
    190     else if (CodeGenOpts.OptimizeSize == 2) // -Oz
    191       Threshold = 25;
    192     else if (OptLevel > 2)
    193       Threshold = 275;
    194     PMBuilder.Inliner = createFunctionInliningPass(Threshold);
    195     break;
    196   }
    197   case CodeGenOptions::OnlyAlwaysInlining:
    198     // Respect always_inline.
    199     if (OptLevel == 0)
    200       // Do not insert lifetime intrinsics at -O0.
    201       PMBuilder.Inliner = createAlwaysInlinerPass(false);
    202     else
    203       PMBuilder.Inliner = createAlwaysInlinerPass();
    204     break;
    205   }
    206 
    207 
    208   // Set up the per-function pass manager.
    209   FunctionPassManager *FPM = getPerFunctionPasses();
    210   if (CodeGenOpts.VerifyModule)
    211     FPM->add(createVerifierPass());
    212   PMBuilder.populateFunctionPassManager(*FPM);
    213 
    214   // Set up the per-module pass manager.
    215   PassManager *MPM = getPerModulePasses();
    216 
    217   if (CodeGenOpts.EmitGcovArcs || CodeGenOpts.EmitGcovNotes) {
    218     MPM->add(createGCOVProfilerPass(CodeGenOpts.EmitGcovNotes,
    219                                     CodeGenOpts.EmitGcovArcs,
    220                                     TargetTriple.isMacOSX()));
    221 
    222     if (!CodeGenOpts.DebugInfo)
    223       MPM->add(createStripSymbolsPass(true));
    224   }
    225 
    226 
    227   PMBuilder.populateModulePassManager(*MPM);
    228 }
    229 
    230 bool EmitAssemblyHelper::AddEmitPasses(BackendAction Action,
    231                                        formatted_raw_ostream &OS) {
    232   // Create the TargetMachine for generating code.
    233   std::string Error;
    234   std::string Triple = TheModule->getTargetTriple();
    235   const llvm::Target *TheTarget = TargetRegistry::lookupTarget(Triple, Error);
    236   if (!TheTarget) {
    237     Diags.Report(diag::err_fe_unable_to_create_target) << Error;
    238     return false;
    239   }
    240 
    241   // FIXME: Expose these capabilities via actual APIs!!!! Aside from just
    242   // being gross, this is also totally broken if we ever care about
    243   // concurrency.
    244 
    245   TargetMachine::setAsmVerbosityDefault(CodeGenOpts.AsmVerbose);
    246 
    247   TargetMachine::setFunctionSections(CodeGenOpts.FunctionSections);
    248   TargetMachine::setDataSections    (CodeGenOpts.DataSections);
    249 
    250   // FIXME: Parse this earlier.
    251   llvm::CodeModel::Model CM;
    252   if (CodeGenOpts.CodeModel == "small") {
    253     CM = llvm::CodeModel::Small;
    254   } else if (CodeGenOpts.CodeModel == "kernel") {
    255     CM = llvm::CodeModel::Kernel;
    256   } else if (CodeGenOpts.CodeModel == "medium") {
    257     CM = llvm::CodeModel::Medium;
    258   } else if (CodeGenOpts.CodeModel == "large") {
    259     CM = llvm::CodeModel::Large;
    260   } else {
    261     assert(CodeGenOpts.CodeModel.empty() && "Invalid code model!");
    262     CM = llvm::CodeModel::Default;
    263   }
    264 
    265   SmallVector<const char *, 16> BackendArgs;
    266   BackendArgs.push_back("clang"); // Fake program name.
    267   if (!CodeGenOpts.DebugPass.empty()) {
    268     BackendArgs.push_back("-debug-pass");
    269     BackendArgs.push_back(CodeGenOpts.DebugPass.c_str());
    270   }
    271   if (!CodeGenOpts.LimitFloatPrecision.empty()) {
    272     BackendArgs.push_back("-limit-float-precision");
    273     BackendArgs.push_back(CodeGenOpts.LimitFloatPrecision.c_str());
    274   }
    275   if (llvm::TimePassesIsEnabled)
    276     BackendArgs.push_back("-time-passes");
    277   for (unsigned i = 0, e = CodeGenOpts.BackendOptions.size(); i != e; ++i)
    278     BackendArgs.push_back(CodeGenOpts.BackendOptions[i].c_str());
    279   if (CodeGenOpts.NoGlobalMerge)
    280     BackendArgs.push_back("-global-merge=false");
    281   BackendArgs.push_back(0);
    282   llvm::cl::ParseCommandLineOptions(BackendArgs.size() - 1,
    283                                     BackendArgs.data());
    284 
    285   std::string FeaturesStr;
    286   if (TargetOpts.Features.size()) {
    287     SubtargetFeatures Features;
    288     for (std::vector<std::string>::const_iterator
    289            it = TargetOpts.Features.begin(),
    290            ie = TargetOpts.Features.end(); it != ie; ++it)
    291       Features.AddFeature(*it);
    292     FeaturesStr = Features.getString();
    293   }
    294 
    295   llvm::Reloc::Model RM = llvm::Reloc::Default;
    296   if (CodeGenOpts.RelocationModel == "static") {
    297     RM = llvm::Reloc::Static;
    298   } else if (CodeGenOpts.RelocationModel == "pic") {
    299     RM = llvm::Reloc::PIC_;
    300   } else {
    301     assert(CodeGenOpts.RelocationModel == "dynamic-no-pic" &&
    302            "Invalid PIC model!");
    303     RM = llvm::Reloc::DynamicNoPIC;
    304   }
    305 
    306   CodeGenOpt::Level OptLevel = CodeGenOpt::Default;
    307   switch (CodeGenOpts.OptimizationLevel) {
    308   default: break;
    309   case 0: OptLevel = CodeGenOpt::None; break;
    310   case 3: OptLevel = CodeGenOpt::Aggressive; break;
    311   }
    312 
    313   llvm::TargetOptions Options;
    314 
    315   // Set frame pointer elimination mode.
    316   if (!CodeGenOpts.DisableFPElim) {
    317     Options.NoFramePointerElim = false;
    318     Options.NoFramePointerElimNonLeaf = false;
    319   } else if (CodeGenOpts.OmitLeafFramePointer) {
    320     Options.NoFramePointerElim = false;
    321     Options.NoFramePointerElimNonLeaf = true;
    322   } else {
    323     Options.NoFramePointerElim = true;
    324     Options.NoFramePointerElimNonLeaf = true;
    325   }
    326 
    327   // Set float ABI type.
    328   if (CodeGenOpts.FloatABI == "soft" || CodeGenOpts.FloatABI == "softfp")
    329     Options.FloatABIType = llvm::FloatABI::Soft;
    330   else if (CodeGenOpts.FloatABI == "hard")
    331     Options.FloatABIType = llvm::FloatABI::Hard;
    332   else {
    333     assert(CodeGenOpts.FloatABI.empty() && "Invalid float abi!");
    334     Options.FloatABIType = llvm::FloatABI::Default;
    335   }
    336 
    337   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
    338   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
    339   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
    340   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
    341   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
    342   Options.UseSoftFloat = CodeGenOpts.SoftFloat;
    343   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
    344   Options.RealignStack = CodeGenOpts.StackRealignment;
    345   Options.DisableTailCalls = CodeGenOpts.DisableTailCalls;
    346   Options.TrapFuncName = CodeGenOpts.TrapFuncName;
    347   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
    348 
    349   TargetMachine *TM = TheTarget->createTargetMachine(Triple, TargetOpts.CPU,
    350                                                      FeaturesStr, Options,
    351                                                      RM, CM, OptLevel);
    352 
    353   if (CodeGenOpts.RelaxAll)
    354     TM->setMCRelaxAll(true);
    355   if (CodeGenOpts.SaveTempLabels)
    356     TM->setMCSaveTempLabels(true);
    357   if (CodeGenOpts.NoDwarf2CFIAsm)
    358     TM->setMCUseCFI(false);
    359   if (!CodeGenOpts.NoDwarfDirectoryAsm)
    360     TM->setMCUseDwarfDirectory(true);
    361   if (CodeGenOpts.NoExecStack)
    362     TM->setMCNoExecStack(true);
    363 
    364   // Create the code generator passes.
    365   PassManager *PM = getCodeGenPasses();
    366 
    367   // Add LibraryInfo.
    368   TargetLibraryInfo *TLI = new TargetLibraryInfo();
    369   if (!CodeGenOpts.SimplifyLibCalls)
    370     TLI->disableAllFunctions();
    371   PM->add(TLI);
    372 
    373   // Normal mode, emit a .s or .o file by running the code generator. Note,
    374   // this also adds codegenerator level optimization passes.
    375   TargetMachine::CodeGenFileType CGFT = TargetMachine::CGFT_AssemblyFile;
    376   if (Action == Backend_EmitObj)
    377     CGFT = TargetMachine::CGFT_ObjectFile;
    378   else if (Action == Backend_EmitMCNull)
    379     CGFT = TargetMachine::CGFT_Null;
    380   else
    381     assert(Action == Backend_EmitAssembly && "Invalid action!");
    382 
    383   // Add ObjC ARC final-cleanup optimizations. This is done as part of the
    384   // "codegen" passes so that it isn't run multiple times when there is
    385   // inlining happening.
    386   if (LangOpts.ObjCAutoRefCount &&
    387       CodeGenOpts.OptimizationLevel > 0)
    388     PM->add(createObjCARCContractPass());
    389 
    390   if (TM->addPassesToEmitFile(*PM, OS, CGFT,
    391                               /*DisableVerify=*/!CodeGenOpts.VerifyModule)) {
    392     Diags.Report(diag::err_fe_unable_to_interface_with_target);
    393     return false;
    394   }
    395 
    396   return true;
    397 }
    398 
    399 void EmitAssemblyHelper::EmitAssembly(BackendAction Action, raw_ostream *OS) {
    400   TimeRegion Region(llvm::TimePassesIsEnabled ? &CodeGenerationTime : 0);
    401   llvm::formatted_raw_ostream FormattedOS;
    402 
    403   CreatePasses();
    404   switch (Action) {
    405   case Backend_EmitNothing:
    406     break;
    407 
    408   case Backend_EmitBC:
    409     getPerModulePasses()->add(createBitcodeWriterPass(*OS));
    410     break;
    411 
    412   case Backend_EmitLL:
    413     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
    414     getPerModulePasses()->add(createPrintModulePass(&FormattedOS));
    415     break;
    416 
    417   default:
    418     FormattedOS.setStream(*OS, formatted_raw_ostream::PRESERVE_STREAM);
    419     if (!AddEmitPasses(Action, FormattedOS))
    420       return;
    421   }
    422 
    423   // Before executing passes, print the final values of the LLVM options.
    424   cl::PrintOptionValues();
    425 
    426   // Run passes. For now we do all passes at once, but eventually we
    427   // would like to have the option of streaming code generation.
    428 
    429   if (PerFunctionPasses) {
    430     PrettyStackTraceString CrashInfo("Per-function optimization");
    431 
    432     PerFunctionPasses->doInitialization();
    433     for (Module::iterator I = TheModule->begin(),
    434            E = TheModule->end(); I != E; ++I)
    435       if (!I->isDeclaration())
    436         PerFunctionPasses->run(*I);
    437     PerFunctionPasses->doFinalization();
    438   }
    439 
    440   if (PerModulePasses) {
    441     PrettyStackTraceString CrashInfo("Per-module optimization passes");
    442     PerModulePasses->run(*TheModule);
    443   }
    444 
    445   if (CodeGenPasses) {
    446     PrettyStackTraceString CrashInfo("Code generation");
    447     CodeGenPasses->run(*TheModule);
    448   }
    449 }
    450 
    451 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
    452                               const CodeGenOptions &CGOpts,
    453                               const clang::TargetOptions &TOpts,
    454                               const LangOptions &LOpts,
    455                               Module *M,
    456                               BackendAction Action, raw_ostream *OS) {
    457   EmitAssemblyHelper AsmHelper(Diags, CGOpts, TOpts, LOpts, M);
    458 
    459   AsmHelper.EmitAssembly(Action, OS);
    460 }
    461