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