Home | History | Annotate | Download | only in LTO 
      1 //===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
      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 // This file implements the Link Time Optimization library. This library is
     11 // intended to be used by linker to optimize code at link time.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "llvm/LTO/LTOCodeGenerator.h"
     16 #include "llvm/ADT/StringExtras.h"
     17 #include "llvm/Analysis/Passes.h"
     18 #include "llvm/Analysis/TargetLibraryInfo.h"
     19 #include "llvm/Analysis/TargetTransformInfo.h"
     20 #include "llvm/Bitcode/ReaderWriter.h"
     21 #include "llvm/CodeGen/RuntimeLibcalls.h"
     22 #include "llvm/Config/config.h"
     23 #include "llvm/IR/Constants.h"
     24 #include "llvm/IR/DataLayout.h"
     25 #include "llvm/IR/DerivedTypes.h"
     26 #include "llvm/IR/DiagnosticInfo.h"
     27 #include "llvm/IR/DiagnosticPrinter.h"
     28 #include "llvm/IR/LLVMContext.h"
     29 #include "llvm/IR/LegacyPassManager.h"
     30 #include "llvm/IR/Mangler.h"
     31 #include "llvm/IR/Module.h"
     32 #include "llvm/IR/Verifier.h"
     33 #include "llvm/InitializePasses.h"
     34 #include "llvm/LTO/LTOModule.h"
     35 #include "llvm/Linker/Linker.h"
     36 #include "llvm/MC/MCAsmInfo.h"
     37 #include "llvm/MC/MCContext.h"
     38 #include "llvm/MC/SubtargetFeature.h"
     39 #include "llvm/Support/CommandLine.h"
     40 #include "llvm/Support/FileSystem.h"
     41 #include "llvm/Support/Host.h"
     42 #include "llvm/Support/MemoryBuffer.h"
     43 #include "llvm/Support/Signals.h"
     44 #include "llvm/Support/TargetRegistry.h"
     45 #include "llvm/Support/TargetSelect.h"
     46 #include "llvm/Support/ToolOutputFile.h"
     47 #include "llvm/Support/raw_ostream.h"
     48 #include "llvm/Target/TargetLowering.h"
     49 #include "llvm/Target/TargetOptions.h"
     50 #include "llvm/Target/TargetRegisterInfo.h"
     51 #include "llvm/Target/TargetSubtargetInfo.h"
     52 #include "llvm/Transforms/IPO.h"
     53 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
     54 #include "llvm/Transforms/ObjCARC.h"
     55 #include <system_error>
     56 using namespace llvm;
     57 
     58 const char* LTOCodeGenerator::getVersionString() {
     59 #ifdef LLVM_VERSION_INFO
     60   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
     61 #else
     62   return PACKAGE_NAME " version " PACKAGE_VERSION;
     63 #endif
     64 }
     65 
     66 LTOCodeGenerator::LTOCodeGenerator()
     67     : Context(getGlobalContext()), IRLinker(new Module("ld-temp.o", Context)) {
     68   initialize();
     69 }
     70 
     71 LTOCodeGenerator::LTOCodeGenerator(std::unique_ptr<LLVMContext> Context)
     72     : OwnedContext(std::move(Context)), Context(*OwnedContext),
     73       IRLinker(new Module("ld-temp.o", *OwnedContext)), OptLevel(2) {
     74   initialize();
     75 }
     76 
     77 void LTOCodeGenerator::initialize() {
     78   TargetMach = nullptr;
     79   EmitDwarfDebugInfo = false;
     80   ScopeRestrictionsDone = false;
     81   CodeModel = LTO_CODEGEN_PIC_MODEL_DEFAULT;
     82   DiagHandler = nullptr;
     83   DiagContext = nullptr;
     84   OwnedModule = nullptr;
     85 
     86   initializeLTOPasses();
     87 }
     88 
     89 void LTOCodeGenerator::destroyMergedModule() {
     90   if (OwnedModule) {
     91     assert(IRLinker.getModule() == &OwnedModule->getModule() &&
     92            "The linker's module should be the same as the owned module");
     93     delete OwnedModule;
     94     OwnedModule = nullptr;
     95   } else if (IRLinker.getModule())
     96     IRLinker.deleteModule();
     97 }
     98 
     99 LTOCodeGenerator::~LTOCodeGenerator() {
    100   destroyMergedModule();
    101 
    102   delete TargetMach;
    103   TargetMach = nullptr;
    104 
    105   for (std::vector<char *>::iterator I = CodegenOptions.begin(),
    106                                      E = CodegenOptions.end();
    107        I != E; ++I)
    108     free(*I);
    109 }
    110 
    111 // Initialize LTO passes. Please keep this funciton in sync with
    112 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
    113 // passes are initialized.
    114 void LTOCodeGenerator::initializeLTOPasses() {
    115   PassRegistry &R = *PassRegistry::getPassRegistry();
    116 
    117   initializeInternalizePassPass(R);
    118   initializeIPSCCPPass(R);
    119   initializeGlobalOptPass(R);
    120   initializeConstantMergePass(R);
    121   initializeDAHPass(R);
    122   initializeInstructionCombiningPassPass(R);
    123   initializeSimpleInlinerPass(R);
    124   initializePruneEHPass(R);
    125   initializeGlobalDCEPass(R);
    126   initializeArgPromotionPass(R);
    127   initializeJumpThreadingPass(R);
    128   initializeSROAPass(R);
    129   initializeSROA_DTPass(R);
    130   initializeSROA_SSAUpPass(R);
    131   initializeFunctionAttrsPass(R);
    132   initializeGlobalsModRefPass(R);
    133   initializeLICMPass(R);
    134   initializeMergedLoadStoreMotionPass(R);
    135   initializeGVNPass(R);
    136   initializeMemCpyOptPass(R);
    137   initializeDCEPass(R);
    138   initializeCFGSimplifyPassPass(R);
    139 }
    140 
    141 bool LTOCodeGenerator::addModule(LTOModule *mod) {
    142   assert(&mod->getModule().getContext() == &Context &&
    143          "Expected module in same context");
    144 
    145   bool ret = IRLinker.linkInModule(&mod->getModule());
    146 
    147   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
    148   for (int i = 0, e = undefs.size(); i != e; ++i)
    149     AsmUndefinedRefs[undefs[i]] = 1;
    150 
    151   return !ret;
    152 }
    153 
    154 void LTOCodeGenerator::setModule(LTOModule *Mod) {
    155   assert(&Mod->getModule().getContext() == &Context &&
    156          "Expected module in same context");
    157 
    158   // Delete the old merged module.
    159   destroyMergedModule();
    160   AsmUndefinedRefs.clear();
    161 
    162   OwnedModule = Mod;
    163   IRLinker.setModule(&Mod->getModule());
    164 
    165   const std::vector<const char*> &Undefs = Mod->getAsmUndefinedRefs();
    166   for (int I = 0, E = Undefs.size(); I != E; ++I)
    167     AsmUndefinedRefs[Undefs[I]] = 1;
    168 }
    169 
    170 void LTOCodeGenerator::setTargetOptions(TargetOptions options) {
    171   Options = options;
    172 }
    173 
    174 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
    175   switch (debug) {
    176   case LTO_DEBUG_MODEL_NONE:
    177     EmitDwarfDebugInfo = false;
    178     return;
    179 
    180   case LTO_DEBUG_MODEL_DWARF:
    181     EmitDwarfDebugInfo = true;
    182     return;
    183   }
    184   llvm_unreachable("Unknown debug format!");
    185 }
    186 
    187 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
    188   switch (model) {
    189   case LTO_CODEGEN_PIC_MODEL_STATIC:
    190   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    191   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    192   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
    193     CodeModel = model;
    194     return;
    195   }
    196   llvm_unreachable("Unknown PIC model!");
    197 }
    198 
    199 bool LTOCodeGenerator::writeMergedModules(const char *path,
    200                                           std::string &errMsg) {
    201   if (!determineTarget(errMsg))
    202     return false;
    203 
    204   // mark which symbols can not be internalized
    205   applyScopeRestrictions();
    206 
    207   // create output file
    208   std::error_code EC;
    209   tool_output_file Out(path, EC, sys::fs::F_None);
    210   if (EC) {
    211     errMsg = "could not open bitcode file for writing: ";
    212     errMsg += path;
    213     return false;
    214   }
    215 
    216   // write bitcode to it
    217   WriteBitcodeToFile(IRLinker.getModule(), Out.os(),
    218                      /* ShouldPreserveUseListOrder */ true);
    219   Out.os().close();
    220 
    221   if (Out.os().has_error()) {
    222     errMsg = "could not write bitcode file: ";
    223     errMsg += path;
    224     Out.os().clear_error();
    225     return false;
    226   }
    227 
    228   Out.keep();
    229   return true;
    230 }
    231 
    232 bool LTOCodeGenerator::compileOptimizedToFile(const char **name,
    233                                               std::string &errMsg) {
    234   // make unique temp .o file to put generated object file
    235   SmallString<128> Filename;
    236   int FD;
    237   std::error_code EC =
    238       sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
    239   if (EC) {
    240     errMsg = EC.message();
    241     return false;
    242   }
    243 
    244   // generate object file
    245   tool_output_file objFile(Filename.c_str(), FD);
    246 
    247   bool genResult = compileOptimized(objFile.os(), errMsg);
    248   objFile.os().close();
    249   if (objFile.os().has_error()) {
    250     objFile.os().clear_error();
    251     sys::fs::remove(Twine(Filename));
    252     return false;
    253   }
    254 
    255   objFile.keep();
    256   if (!genResult) {
    257     sys::fs::remove(Twine(Filename));
    258     return false;
    259   }
    260 
    261   NativeObjectPath = Filename.c_str();
    262   *name = NativeObjectPath.c_str();
    263   return true;
    264 }
    265 
    266 const void *LTOCodeGenerator::compileOptimized(size_t *length,
    267                                                std::string &errMsg) {
    268   const char *name;
    269   if (!compileOptimizedToFile(&name, errMsg))
    270     return nullptr;
    271 
    272   // read .o file into memory buffer
    273   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
    274       MemoryBuffer::getFile(name, -1, false);
    275   if (std::error_code EC = BufferOrErr.getError()) {
    276     errMsg = EC.message();
    277     sys::fs::remove(NativeObjectPath);
    278     return nullptr;
    279   }
    280   NativeObjectFile = std::move(*BufferOrErr);
    281 
    282   // remove temp files
    283   sys::fs::remove(NativeObjectPath);
    284 
    285   // return buffer, unless error
    286   if (!NativeObjectFile)
    287     return nullptr;
    288   *length = NativeObjectFile->getBufferSize();
    289   return NativeObjectFile->getBufferStart();
    290 }
    291 
    292 
    293 bool LTOCodeGenerator::compile_to_file(const char **name,
    294                                        bool disableInline,
    295                                        bool disableGVNLoadPRE,
    296                                        bool disableVectorization,
    297                                        std::string &errMsg) {
    298   if (!optimize(disableInline, disableGVNLoadPRE,
    299                 disableVectorization, errMsg))
    300     return false;
    301 
    302   return compileOptimizedToFile(name, errMsg);
    303 }
    304 
    305 const void* LTOCodeGenerator::compile(size_t *length,
    306                                       bool disableInline,
    307                                       bool disableGVNLoadPRE,
    308                                       bool disableVectorization,
    309                                       std::string &errMsg) {
    310   if (!optimize(disableInline, disableGVNLoadPRE,
    311                 disableVectorization, errMsg))
    312     return nullptr;
    313 
    314   return compileOptimized(length, errMsg);
    315 }
    316 
    317 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
    318   if (TargetMach)
    319     return true;
    320 
    321   std::string TripleStr = IRLinker.getModule()->getTargetTriple();
    322   if (TripleStr.empty())
    323     TripleStr = sys::getDefaultTargetTriple();
    324   llvm::Triple Triple(TripleStr);
    325 
    326   // create target machine from info for merged modules
    327   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
    328   if (!march)
    329     return false;
    330 
    331   // The relocation model is actually a static member of TargetMachine and
    332   // needs to be set before the TargetMachine is instantiated.
    333   Reloc::Model RelocModel = Reloc::Default;
    334   switch (CodeModel) {
    335   case LTO_CODEGEN_PIC_MODEL_STATIC:
    336     RelocModel = Reloc::Static;
    337     break;
    338   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    339     RelocModel = Reloc::PIC_;
    340     break;
    341   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    342     RelocModel = Reloc::DynamicNoPIC;
    343     break;
    344   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
    345     // RelocModel is already the default, so leave it that way.
    346     break;
    347   }
    348 
    349   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
    350   // the default set of features.
    351   SubtargetFeatures Features(MAttr);
    352   Features.getDefaultSubtargetFeatures(Triple);
    353   std::string FeatureStr = Features.getString();
    354   // Set a default CPU for Darwin triples.
    355   if (MCpu.empty() && Triple.isOSDarwin()) {
    356     if (Triple.getArch() == llvm::Triple::x86_64)
    357       MCpu = "core2";
    358     else if (Triple.getArch() == llvm::Triple::x86)
    359       MCpu = "yonah";
    360     else if (Triple.getArch() == llvm::Triple::aarch64)
    361       MCpu = "cyclone";
    362   }
    363 
    364   CodeGenOpt::Level CGOptLevel;
    365   switch (OptLevel) {
    366   case 0:
    367     CGOptLevel = CodeGenOpt::None;
    368     break;
    369   case 1:
    370     CGOptLevel = CodeGenOpt::Less;
    371     break;
    372   case 2:
    373     CGOptLevel = CodeGenOpt::Default;
    374     break;
    375   case 3:
    376     CGOptLevel = CodeGenOpt::Aggressive;
    377     break;
    378   }
    379 
    380   TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
    381                                           RelocModel, CodeModel::Default,
    382                                           CGOptLevel);
    383   return true;
    384 }
    385 
    386 void LTOCodeGenerator::
    387 applyRestriction(GlobalValue &GV,
    388                  ArrayRef<StringRef> Libcalls,
    389                  std::vector<const char*> &MustPreserveList,
    390                  SmallPtrSetImpl<GlobalValue*> &AsmUsed,
    391                  Mangler &Mangler) {
    392   // There are no restrictions to apply to declarations.
    393   if (GV.isDeclaration())
    394     return;
    395 
    396   // There is nothing more restrictive than private linkage.
    397   if (GV.hasPrivateLinkage())
    398     return;
    399 
    400   SmallString<64> Buffer;
    401   TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
    402 
    403   if (MustPreserveSymbols.count(Buffer))
    404     MustPreserveList.push_back(GV.getName().data());
    405   if (AsmUndefinedRefs.count(Buffer))
    406     AsmUsed.insert(&GV);
    407 
    408   // Conservatively append user-supplied runtime library functions to
    409   // llvm.compiler.used.  These could be internalized and deleted by
    410   // optimizations like -globalopt, causing problems when later optimizations
    411   // add new library calls (e.g., llvm.memset => memset and printf => puts).
    412   // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
    413   if (isa<Function>(GV) &&
    414       std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
    415     AsmUsed.insert(&GV);
    416 }
    417 
    418 static void findUsedValues(GlobalVariable *LLVMUsed,
    419                            SmallPtrSetImpl<GlobalValue*> &UsedValues) {
    420   if (!LLVMUsed) return;
    421 
    422   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
    423   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
    424     if (GlobalValue *GV =
    425         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
    426       UsedValues.insert(GV);
    427 }
    428 
    429 // Collect names of runtime library functions. User-defined functions with the
    430 // same names are added to llvm.compiler.used to prevent them from being
    431 // deleted by optimizations.
    432 static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
    433                                       const TargetLibraryInfo& TLI,
    434                                       const Module &Mod,
    435                                       const TargetMachine &TM) {
    436   // TargetLibraryInfo has info on C runtime library calls on the current
    437   // target.
    438   for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
    439        I != E; ++I) {
    440     LibFunc::Func F = static_cast<LibFunc::Func>(I);
    441     if (TLI.has(F))
    442       Libcalls.push_back(TLI.getName(F));
    443   }
    444 
    445   SmallPtrSet<const TargetLowering *, 1> TLSet;
    446 
    447   for (const Function &F : Mod) {
    448     const TargetLowering *Lowering =
    449         TM.getSubtargetImpl(F)->getTargetLowering();
    450 
    451     if (Lowering && TLSet.insert(Lowering).second)
    452       // TargetLowering has info on library calls that CodeGen expects to be
    453       // available, both from the C runtime and compiler-rt.
    454       for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
    455            I != E; ++I)
    456         if (const char *Name =
    457                 Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
    458           Libcalls.push_back(Name);
    459   }
    460 
    461   array_pod_sort(Libcalls.begin(), Libcalls.end());
    462   Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
    463                  Libcalls.end());
    464 }
    465 
    466 void LTOCodeGenerator::applyScopeRestrictions() {
    467   if (ScopeRestrictionsDone)
    468     return;
    469   Module *mergedModule = IRLinker.getModule();
    470 
    471   // Start off with a verification pass.
    472   legacy::PassManager passes;
    473   passes.add(createVerifierPass());
    474 
    475   // mark which symbols can not be internalized
    476   Mangler Mangler(TargetMach->getDataLayout());
    477   std::vector<const char*> MustPreserveList;
    478   SmallPtrSet<GlobalValue*, 8> AsmUsed;
    479   std::vector<StringRef> Libcalls;
    480   TargetLibraryInfoImpl TLII(Triple(TargetMach->getTargetTriple()));
    481   TargetLibraryInfo TLI(TLII);
    482 
    483   accumulateAndSortLibcalls(Libcalls, TLI, *mergedModule, *TargetMach);
    484 
    485   for (Module::iterator f = mergedModule->begin(),
    486          e = mergedModule->end(); f != e; ++f)
    487     applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
    488   for (Module::global_iterator v = mergedModule->global_begin(),
    489          e = mergedModule->global_end(); v !=  e; ++v)
    490     applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
    491   for (Module::alias_iterator a = mergedModule->alias_begin(),
    492          e = mergedModule->alias_end(); a != e; ++a)
    493     applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);
    494 
    495   GlobalVariable *LLVMCompilerUsed =
    496     mergedModule->getGlobalVariable("llvm.compiler.used");
    497   findUsedValues(LLVMCompilerUsed, AsmUsed);
    498   if (LLVMCompilerUsed)
    499     LLVMCompilerUsed->eraseFromParent();
    500 
    501   if (!AsmUsed.empty()) {
    502     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
    503     std::vector<Constant*> asmUsed2;
    504     for (auto *GV : AsmUsed) {
    505       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
    506       asmUsed2.push_back(c);
    507     }
    508 
    509     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
    510     LLVMCompilerUsed =
    511       new llvm::GlobalVariable(*mergedModule, ATy, false,
    512                                llvm::GlobalValue::AppendingLinkage,
    513                                llvm::ConstantArray::get(ATy, asmUsed2),
    514                                "llvm.compiler.used");
    515 
    516     LLVMCompilerUsed->setSection("llvm.metadata");
    517   }
    518 
    519   passes.add(createInternalizePass(MustPreserveList));
    520 
    521   // apply scope restrictions
    522   passes.run(*mergedModule);
    523 
    524   ScopeRestrictionsDone = true;
    525 }
    526 
    527 /// Optimize merged modules using various IPO passes
    528 bool LTOCodeGenerator::optimize(bool DisableInline,
    529                                 bool DisableGVNLoadPRE,
    530                                 bool DisableVectorization,
    531                                 std::string &errMsg) {
    532   if (!this->determineTarget(errMsg))
    533     return false;
    534 
    535   Module *mergedModule = IRLinker.getModule();
    536 
    537   // Mark which symbols can not be internalized
    538   this->applyScopeRestrictions();
    539 
    540   // Instantiate the pass manager to organize the passes.
    541   legacy::PassManager passes;
    542 
    543   // Add an appropriate DataLayout instance for this module...
    544   mergedModule->setDataLayout(*TargetMach->getDataLayout());
    545 
    546   passes.add(
    547       createTargetTransformInfoWrapperPass(TargetMach->getTargetIRAnalysis()));
    548 
    549   Triple TargetTriple(TargetMach->getTargetTriple());
    550   PassManagerBuilder PMB;
    551   PMB.DisableGVNLoadPRE = DisableGVNLoadPRE;
    552   PMB.LoopVectorize = !DisableVectorization;
    553   PMB.SLPVectorize = !DisableVectorization;
    554   if (!DisableInline)
    555     PMB.Inliner = createFunctionInliningPass();
    556   PMB.LibraryInfo = new TargetLibraryInfoImpl(TargetTriple);
    557   PMB.OptLevel = OptLevel;
    558   PMB.VerifyInput = true;
    559   PMB.VerifyOutput = true;
    560 
    561   PMB.populateLTOPassManager(passes);
    562 
    563   // Run our queue of passes all at once now, efficiently.
    564   passes.run(*mergedModule);
    565 
    566   return true;
    567 }
    568 
    569 bool LTOCodeGenerator::compileOptimized(raw_pwrite_stream &out,
    570                                         std::string &errMsg) {
    571   if (!this->determineTarget(errMsg))
    572     return false;
    573 
    574   Module *mergedModule = IRLinker.getModule();
    575 
    576   legacy::PassManager codeGenPasses;
    577 
    578   // If the bitcode files contain ARC code and were compiled with optimization,
    579   // the ObjCARCContractPass must be run, so do it unconditionally here.
    580   codeGenPasses.add(createObjCARCContractPass());
    581 
    582   if (TargetMach->addPassesToEmitFile(codeGenPasses, out,
    583                                       TargetMachine::CGFT_ObjectFile)) {
    584     errMsg = "target file type not supported";
    585     return false;
    586   }
    587 
    588   // Run the code generator, and write assembly file
    589   codeGenPasses.run(*mergedModule);
    590 
    591   return true;
    592 }
    593 
    594 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
    595 /// LTO problems.
    596 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
    597   for (std::pair<StringRef, StringRef> o = getToken(options);
    598        !o.first.empty(); o = getToken(o.second)) {
    599     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
    600     // that.
    601     if (CodegenOptions.empty())
    602       CodegenOptions.push_back(strdup("libLLVMLTO"));
    603     CodegenOptions.push_back(strdup(o.first.str().c_str()));
    604   }
    605 }
    606 
    607 void LTOCodeGenerator::parseCodeGenDebugOptions() {
    608   // if options were requested, set them
    609   if (!CodegenOptions.empty())
    610     cl::ParseCommandLineOptions(CodegenOptions.size(),
    611                                 const_cast<char **>(&CodegenOptions[0]));
    612 }
    613 
    614 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI,
    615                                          void *Context) {
    616   ((LTOCodeGenerator *)Context)->DiagnosticHandler2(DI);
    617 }
    618 
    619 void LTOCodeGenerator::DiagnosticHandler2(const DiagnosticInfo &DI) {
    620   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
    621   lto_codegen_diagnostic_severity_t Severity;
    622   switch (DI.getSeverity()) {
    623   case DS_Error:
    624     Severity = LTO_DS_ERROR;
    625     break;
    626   case DS_Warning:
    627     Severity = LTO_DS_WARNING;
    628     break;
    629   case DS_Remark:
    630     Severity = LTO_DS_REMARK;
    631     break;
    632   case DS_Note:
    633     Severity = LTO_DS_NOTE;
    634     break;
    635   }
    636   // Create the string that will be reported to the external diagnostic handler.
    637   std::string MsgStorage;
    638   raw_string_ostream Stream(MsgStorage);
    639   DiagnosticPrinterRawOStream DP(Stream);
    640   DI.print(DP);
    641   Stream.flush();
    642 
    643   // If this method has been called it means someone has set up an external
    644   // diagnostic handler. Assert on that.
    645   assert(DiagHandler && "Invalid diagnostic handler");
    646   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
    647 }
    648 
    649 void
    650 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
    651                                        void *Ctxt) {
    652   this->DiagHandler = DiagHandler;
    653   this->DiagContext = Ctxt;
    654   if (!DiagHandler)
    655     return Context.setDiagnosticHandler(nullptr, nullptr);
    656   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
    657   // diagnostic to the external DiagHandler.
    658   Context.setDiagnosticHandler(LTOCodeGenerator::DiagnosticHandler, this,
    659                                /* RespectFilters */ true);
    660 }
    661