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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/Bitcode/ReaderWriter.h"
     19 #include "llvm/CodeGen/RuntimeLibcalls.h"
     20 #include "llvm/Config/config.h"
     21 #include "llvm/IR/Constants.h"
     22 #include "llvm/IR/DataLayout.h"
     23 #include "llvm/IR/DerivedTypes.h"
     24 #include "llvm/IR/DiagnosticInfo.h"
     25 #include "llvm/IR/DiagnosticPrinter.h"
     26 #include "llvm/IR/LLVMContext.h"
     27 #include "llvm/IR/Mangler.h"
     28 #include "llvm/IR/Module.h"
     29 #include "llvm/IR/Verifier.h"
     30 #include "llvm/InitializePasses.h"
     31 #include "llvm/LTO/LTOModule.h"
     32 #include "llvm/Linker/Linker.h"
     33 #include "llvm/MC/MCAsmInfo.h"
     34 #include "llvm/MC/MCContext.h"
     35 #include "llvm/MC/SubtargetFeature.h"
     36 #include "llvm/PassManager.h"
     37 #include "llvm/Support/CommandLine.h"
     38 #include "llvm/Support/FileSystem.h"
     39 #include "llvm/Support/FormattedStream.h"
     40 #include "llvm/Support/Host.h"
     41 #include "llvm/Support/MemoryBuffer.h"
     42 #include "llvm/Support/Signals.h"
     43 #include "llvm/Support/TargetRegistry.h"
     44 #include "llvm/Support/TargetSelect.h"
     45 #include "llvm/Support/ToolOutputFile.h"
     46 #include "llvm/Support/raw_ostream.h"
     47 #include "llvm/Target/TargetLibraryInfo.h"
     48 #include "llvm/Target/TargetLowering.h"
     49 #include "llvm/Target/TargetOptions.h"
     50 #include "llvm/Target/TargetRegisterInfo.h"
     51 #include "llvm/Transforms/IPO.h"
     52 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
     53 #include "llvm/Transforms/ObjCARC.h"
     54 #include <system_error>
     55 using namespace llvm;
     56 
     57 const char* LTOCodeGenerator::getVersionString() {
     58 #ifdef LLVM_VERSION_INFO
     59   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
     60 #else
     61   return PACKAGE_NAME " version " PACKAGE_VERSION;
     62 #endif
     63 }
     64 
     65 LTOCodeGenerator::LTOCodeGenerator()
     66     : Context(getGlobalContext()), IRLinker(new Module("ld-temp.o", Context)),
     67       TargetMach(nullptr), EmitDwarfDebugInfo(false),
     68       ScopeRestrictionsDone(false), CodeModel(LTO_CODEGEN_PIC_MODEL_DEFAULT),
     69       NativeObjectFile(nullptr), DiagHandler(nullptr), DiagContext(nullptr) {
     70   initializeLTOPasses();
     71 }
     72 
     73 LTOCodeGenerator::~LTOCodeGenerator() {
     74   delete TargetMach;
     75   delete NativeObjectFile;
     76   TargetMach = nullptr;
     77   NativeObjectFile = nullptr;
     78 
     79   IRLinker.deleteModule();
     80 
     81   for (std::vector<char *>::iterator I = CodegenOptions.begin(),
     82                                      E = CodegenOptions.end();
     83        I != E; ++I)
     84     free(*I);
     85 }
     86 
     87 // Initialize LTO passes. Please keep this funciton in sync with
     88 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
     89 // passes are initialized.
     90 void LTOCodeGenerator::initializeLTOPasses() {
     91   PassRegistry &R = *PassRegistry::getPassRegistry();
     92 
     93   initializeInternalizePassPass(R);
     94   initializeIPSCCPPass(R);
     95   initializeGlobalOptPass(R);
     96   initializeConstantMergePass(R);
     97   initializeDAHPass(R);
     98   initializeInstCombinerPass(R);
     99   initializeSimpleInlinerPass(R);
    100   initializePruneEHPass(R);
    101   initializeGlobalDCEPass(R);
    102   initializeArgPromotionPass(R);
    103   initializeJumpThreadingPass(R);
    104   initializeSROAPass(R);
    105   initializeSROA_DTPass(R);
    106   initializeSROA_SSAUpPass(R);
    107   initializeFunctionAttrsPass(R);
    108   initializeGlobalsModRefPass(R);
    109   initializeLICMPass(R);
    110   initializeGVNPass(R);
    111   initializeMemCpyOptPass(R);
    112   initializeDCEPass(R);
    113   initializeCFGSimplifyPassPass(R);
    114 }
    115 
    116 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
    117   bool ret = IRLinker.linkInModule(&mod->getModule(), &errMsg);
    118 
    119   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
    120   for (int i = 0, e = undefs.size(); i != e; ++i)
    121     AsmUndefinedRefs[undefs[i]] = 1;
    122 
    123   return !ret;
    124 }
    125 
    126 void LTOCodeGenerator::setTargetOptions(TargetOptions options) {
    127   Options = options;
    128 }
    129 
    130 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
    131   switch (debug) {
    132   case LTO_DEBUG_MODEL_NONE:
    133     EmitDwarfDebugInfo = false;
    134     return;
    135 
    136   case LTO_DEBUG_MODEL_DWARF:
    137     EmitDwarfDebugInfo = true;
    138     return;
    139   }
    140   llvm_unreachable("Unknown debug format!");
    141 }
    142 
    143 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
    144   switch (model) {
    145   case LTO_CODEGEN_PIC_MODEL_STATIC:
    146   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    147   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    148   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
    149     CodeModel = model;
    150     return;
    151   }
    152   llvm_unreachable("Unknown PIC model!");
    153 }
    154 
    155 bool LTOCodeGenerator::writeMergedModules(const char *path,
    156                                           std::string &errMsg) {
    157   if (!determineTarget(errMsg))
    158     return false;
    159 
    160   // mark which symbols can not be internalized
    161   applyScopeRestrictions();
    162 
    163   // create output file
    164   std::string ErrInfo;
    165   tool_output_file Out(path, ErrInfo, sys::fs::F_None);
    166   if (!ErrInfo.empty()) {
    167     errMsg = "could not open bitcode file for writing: ";
    168     errMsg += path;
    169     return false;
    170   }
    171 
    172   // write bitcode to it
    173   WriteBitcodeToFile(IRLinker.getModule(), Out.os());
    174   Out.os().close();
    175 
    176   if (Out.os().has_error()) {
    177     errMsg = "could not write bitcode file: ";
    178     errMsg += path;
    179     Out.os().clear_error();
    180     return false;
    181   }
    182 
    183   Out.keep();
    184   return true;
    185 }
    186 
    187 bool LTOCodeGenerator::compile_to_file(const char** name,
    188                                        bool disableOpt,
    189                                        bool disableInline,
    190                                        bool disableGVNLoadPRE,
    191                                        std::string& errMsg) {
    192   // make unique temp .o file to put generated object file
    193   SmallString<128> Filename;
    194   int FD;
    195   std::error_code EC =
    196       sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
    197   if (EC) {
    198     errMsg = EC.message();
    199     return false;
    200   }
    201 
    202   // generate object file
    203   tool_output_file objFile(Filename.c_str(), FD);
    204 
    205   bool genResult = generateObjectFile(objFile.os(), disableOpt, disableInline,
    206                                       disableGVNLoadPRE, errMsg);
    207   objFile.os().close();
    208   if (objFile.os().has_error()) {
    209     objFile.os().clear_error();
    210     sys::fs::remove(Twine(Filename));
    211     return false;
    212   }
    213 
    214   objFile.keep();
    215   if (!genResult) {
    216     sys::fs::remove(Twine(Filename));
    217     return false;
    218   }
    219 
    220   NativeObjectPath = Filename.c_str();
    221   *name = NativeObjectPath.c_str();
    222   return true;
    223 }
    224 
    225 const void* LTOCodeGenerator::compile(size_t* length,
    226                                       bool disableOpt,
    227                                       bool disableInline,
    228                                       bool disableGVNLoadPRE,
    229                                       std::string& errMsg) {
    230   const char *name;
    231   if (!compile_to_file(&name, disableOpt, disableInline, disableGVNLoadPRE,
    232                        errMsg))
    233     return nullptr;
    234 
    235   // remove old buffer if compile() called twice
    236   delete NativeObjectFile;
    237 
    238   // read .o file into memory buffer
    239   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
    240       MemoryBuffer::getFile(name, -1, false);
    241   if (std::error_code EC = BufferOrErr.getError()) {
    242     errMsg = EC.message();
    243     sys::fs::remove(NativeObjectPath);
    244     return nullptr;
    245   }
    246   NativeObjectFile = BufferOrErr.get().release();
    247 
    248   // remove temp files
    249   sys::fs::remove(NativeObjectPath);
    250 
    251   // return buffer, unless error
    252   if (!NativeObjectFile)
    253     return nullptr;
    254   *length = NativeObjectFile->getBufferSize();
    255   return NativeObjectFile->getBufferStart();
    256 }
    257 
    258 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
    259   if (TargetMach)
    260     return true;
    261 
    262   std::string TripleStr = IRLinker.getModule()->getTargetTriple();
    263   if (TripleStr.empty())
    264     TripleStr = sys::getDefaultTargetTriple();
    265   llvm::Triple Triple(TripleStr);
    266 
    267   // create target machine from info for merged modules
    268   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
    269   if (!march)
    270     return false;
    271 
    272   // The relocation model is actually a static member of TargetMachine and
    273   // needs to be set before the TargetMachine is instantiated.
    274   Reloc::Model RelocModel = Reloc::Default;
    275   switch (CodeModel) {
    276   case LTO_CODEGEN_PIC_MODEL_STATIC:
    277     RelocModel = Reloc::Static;
    278     break;
    279   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    280     RelocModel = Reloc::PIC_;
    281     break;
    282   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    283     RelocModel = Reloc::DynamicNoPIC;
    284     break;
    285   case LTO_CODEGEN_PIC_MODEL_DEFAULT:
    286     // RelocModel is already the default, so leave it that way.
    287     break;
    288   }
    289 
    290   // Construct LTOModule, hand over ownership of module and target. Use MAttr as
    291   // the default set of features.
    292   SubtargetFeatures Features(MAttr);
    293   Features.getDefaultSubtargetFeatures(Triple);
    294   std::string FeatureStr = Features.getString();
    295   // Set a default CPU for Darwin triples.
    296   if (MCpu.empty() && Triple.isOSDarwin()) {
    297     if (Triple.getArch() == llvm::Triple::x86_64)
    298       MCpu = "core2";
    299     else if (Triple.getArch() == llvm::Triple::x86)
    300       MCpu = "yonah";
    301     else if (Triple.getArch() == llvm::Triple::arm64 ||
    302              Triple.getArch() == llvm::Triple::aarch64)
    303       MCpu = "cyclone";
    304   }
    305 
    306   TargetMach = march->createTargetMachine(TripleStr, MCpu, FeatureStr, Options,
    307                                           RelocModel, CodeModel::Default,
    308                                           CodeGenOpt::Aggressive);
    309   return true;
    310 }
    311 
    312 void LTOCodeGenerator::
    313 applyRestriction(GlobalValue &GV,
    314                  const ArrayRef<StringRef> &Libcalls,
    315                  std::vector<const char*> &MustPreserveList,
    316                  SmallPtrSet<GlobalValue*, 8> &AsmUsed,
    317                  Mangler &Mangler) {
    318   // There are no restrictions to apply to declarations.
    319   if (GV.isDeclaration())
    320     return;
    321 
    322   // There is nothing more restrictive than private linkage.
    323   if (GV.hasPrivateLinkage())
    324     return;
    325 
    326   SmallString<64> Buffer;
    327   TargetMach->getNameWithPrefix(Buffer, &GV, Mangler);
    328 
    329   if (MustPreserveSymbols.count(Buffer))
    330     MustPreserveList.push_back(GV.getName().data());
    331   if (AsmUndefinedRefs.count(Buffer))
    332     AsmUsed.insert(&GV);
    333 
    334   // Conservatively append user-supplied runtime library functions to
    335   // llvm.compiler.used.  These could be internalized and deleted by
    336   // optimizations like -globalopt, causing problems when later optimizations
    337   // add new library calls (e.g., llvm.memset => memset and printf => puts).
    338   // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
    339   if (isa<Function>(GV) &&
    340       std::binary_search(Libcalls.begin(), Libcalls.end(), GV.getName()))
    341     AsmUsed.insert(&GV);
    342 }
    343 
    344 static void findUsedValues(GlobalVariable *LLVMUsed,
    345                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
    346   if (!LLVMUsed) return;
    347 
    348   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
    349   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
    350     if (GlobalValue *GV =
    351         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
    352       UsedValues.insert(GV);
    353 }
    354 
    355 static void accumulateAndSortLibcalls(std::vector<StringRef> &Libcalls,
    356                                       const TargetLibraryInfo& TLI,
    357                                       const TargetLowering *Lowering)
    358 {
    359   // TargetLibraryInfo has info on C runtime library calls on the current
    360   // target.
    361   for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
    362        I != E; ++I) {
    363     LibFunc::Func F = static_cast<LibFunc::Func>(I);
    364     if (TLI.has(F))
    365       Libcalls.push_back(TLI.getName(F));
    366   }
    367 
    368   // TargetLowering has info on library calls that CodeGen expects to be
    369   // available, both from the C runtime and compiler-rt.
    370   if (Lowering)
    371     for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
    372          I != E; ++I)
    373       if (const char *Name
    374           = Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
    375         Libcalls.push_back(Name);
    376 
    377   array_pod_sort(Libcalls.begin(), Libcalls.end());
    378   Libcalls.erase(std::unique(Libcalls.begin(), Libcalls.end()),
    379                  Libcalls.end());
    380 }
    381 
    382 void LTOCodeGenerator::applyScopeRestrictions() {
    383   if (ScopeRestrictionsDone)
    384     return;
    385   Module *mergedModule = IRLinker.getModule();
    386 
    387   // Start off with a verification pass.
    388   PassManager passes;
    389   passes.add(createVerifierPass());
    390   passes.add(createDebugInfoVerifierPass());
    391 
    392   // mark which symbols can not be internalized
    393   Mangler Mangler(TargetMach->getDataLayout());
    394   std::vector<const char*> MustPreserveList;
    395   SmallPtrSet<GlobalValue*, 8> AsmUsed;
    396   std::vector<StringRef> Libcalls;
    397   TargetLibraryInfo TLI(Triple(TargetMach->getTargetTriple()));
    398   accumulateAndSortLibcalls(Libcalls, TLI, TargetMach->getTargetLowering());
    399 
    400   for (Module::iterator f = mergedModule->begin(),
    401          e = mergedModule->end(); f != e; ++f)
    402     applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
    403   for (Module::global_iterator v = mergedModule->global_begin(),
    404          e = mergedModule->global_end(); v !=  e; ++v)
    405     applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
    406   for (Module::alias_iterator a = mergedModule->alias_begin(),
    407          e = mergedModule->alias_end(); a != e; ++a)
    408     applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);
    409 
    410   GlobalVariable *LLVMCompilerUsed =
    411     mergedModule->getGlobalVariable("llvm.compiler.used");
    412   findUsedValues(LLVMCompilerUsed, AsmUsed);
    413   if (LLVMCompilerUsed)
    414     LLVMCompilerUsed->eraseFromParent();
    415 
    416   if (!AsmUsed.empty()) {
    417     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
    418     std::vector<Constant*> asmUsed2;
    419     for (auto *GV : AsmUsed) {
    420       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
    421       asmUsed2.push_back(c);
    422     }
    423 
    424     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
    425     LLVMCompilerUsed =
    426       new llvm::GlobalVariable(*mergedModule, ATy, false,
    427                                llvm::GlobalValue::AppendingLinkage,
    428                                llvm::ConstantArray::get(ATy, asmUsed2),
    429                                "llvm.compiler.used");
    430 
    431     LLVMCompilerUsed->setSection("llvm.metadata");
    432   }
    433 
    434   passes.add(createInternalizePass(MustPreserveList));
    435 
    436   // apply scope restrictions
    437   passes.run(*mergedModule);
    438 
    439   ScopeRestrictionsDone = true;
    440 }
    441 
    442 /// Optimize merged modules using various IPO passes
    443 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
    444                                           bool DisableOpt,
    445                                           bool DisableInline,
    446                                           bool DisableGVNLoadPRE,
    447                                           std::string &errMsg) {
    448   if (!this->determineTarget(errMsg))
    449     return false;
    450 
    451   Module *mergedModule = IRLinker.getModule();
    452 
    453   // Mark which symbols can not be internalized
    454   this->applyScopeRestrictions();
    455 
    456   // Instantiate the pass manager to organize the passes.
    457   PassManager passes;
    458 
    459   // Start off with a verification pass.
    460   passes.add(createVerifierPass());
    461   passes.add(createDebugInfoVerifierPass());
    462 
    463   // Add an appropriate DataLayout instance for this module...
    464   mergedModule->setDataLayout(TargetMach->getDataLayout());
    465   passes.add(new DataLayoutPass(mergedModule));
    466 
    467   // Add appropriate TargetLibraryInfo for this module.
    468   passes.add(new TargetLibraryInfo(Triple(TargetMach->getTargetTriple())));
    469 
    470   TargetMach->addAnalysisPasses(passes);
    471 
    472   // Enabling internalize here would use its AllButMain variant. It
    473   // keeps only main if it exists and does nothing for libraries. Instead
    474   // we create the pass ourselves with the symbol list provided by the linker.
    475   if (!DisableOpt)
    476     PassManagerBuilder().populateLTOPassManager(passes,
    477                                               /*Internalize=*/false,
    478                                               !DisableInline,
    479                                               DisableGVNLoadPRE);
    480 
    481   // Make sure everything is still good.
    482   passes.add(createVerifierPass());
    483   passes.add(createDebugInfoVerifierPass());
    484 
    485   PassManager codeGenPasses;
    486 
    487   codeGenPasses.add(new DataLayoutPass(mergedModule));
    488 
    489   formatted_raw_ostream Out(out);
    490 
    491   // If the bitcode files contain ARC code and were compiled with optimization,
    492   // the ObjCARCContractPass must be run, so do it unconditionally here.
    493   codeGenPasses.add(createObjCARCContractPass());
    494 
    495   if (TargetMach->addPassesToEmitFile(codeGenPasses, Out,
    496                                       TargetMachine::CGFT_ObjectFile)) {
    497     errMsg = "target file type not supported";
    498     return false;
    499   }
    500 
    501   // Run our queue of passes all at once now, efficiently.
    502   passes.run(*mergedModule);
    503 
    504   // Run the code generator, and write assembly file
    505   codeGenPasses.run(*mergedModule);
    506 
    507   return true;
    508 }
    509 
    510 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
    511 /// LTO problems.
    512 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
    513   for (std::pair<StringRef, StringRef> o = getToken(options);
    514        !o.first.empty(); o = getToken(o.second)) {
    515     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
    516     // that.
    517     if (CodegenOptions.empty())
    518       CodegenOptions.push_back(strdup("libLLVMLTO"));
    519     CodegenOptions.push_back(strdup(o.first.str().c_str()));
    520   }
    521 }
    522 
    523 void LTOCodeGenerator::parseCodeGenDebugOptions() {
    524   // if options were requested, set them
    525   if (!CodegenOptions.empty())
    526     cl::ParseCommandLineOptions(CodegenOptions.size(),
    527                                 const_cast<char **>(&CodegenOptions[0]));
    528 }
    529 
    530 void LTOCodeGenerator::DiagnosticHandler(const DiagnosticInfo &DI,
    531                                          void *Context) {
    532   ((LTOCodeGenerator *)Context)->DiagnosticHandler2(DI);
    533 }
    534 
    535 void LTOCodeGenerator::DiagnosticHandler2(const DiagnosticInfo &DI) {
    536   // Map the LLVM internal diagnostic severity to the LTO diagnostic severity.
    537   lto_codegen_diagnostic_severity_t Severity;
    538   switch (DI.getSeverity()) {
    539   case DS_Error:
    540     Severity = LTO_DS_ERROR;
    541     break;
    542   case DS_Warning:
    543     Severity = LTO_DS_WARNING;
    544     break;
    545   case DS_Remark:
    546     Severity = LTO_DS_REMARK;
    547     break;
    548   case DS_Note:
    549     Severity = LTO_DS_NOTE;
    550     break;
    551   }
    552   // Create the string that will be reported to the external diagnostic handler.
    553   std::string MsgStorage;
    554   raw_string_ostream Stream(MsgStorage);
    555   DiagnosticPrinterRawOStream DP(Stream);
    556   DI.print(DP);
    557   Stream.flush();
    558 
    559   // If this method has been called it means someone has set up an external
    560   // diagnostic handler. Assert on that.
    561   assert(DiagHandler && "Invalid diagnostic handler");
    562   (*DiagHandler)(Severity, MsgStorage.c_str(), DiagContext);
    563 }
    564 
    565 void
    566 LTOCodeGenerator::setDiagnosticHandler(lto_diagnostic_handler_t DiagHandler,
    567                                        void *Ctxt) {
    568   this->DiagHandler = DiagHandler;
    569   this->DiagContext = Ctxt;
    570   if (!DiagHandler)
    571     return Context.setDiagnosticHandler(nullptr, nullptr);
    572   // Register the LTOCodeGenerator stub in the LLVMContext to forward the
    573   // diagnostic to the external DiagHandler.
    574   Context.setDiagnosticHandler(LTOCodeGenerator::DiagnosticHandler, this);
    575 }
    576