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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 "LTOCodeGenerator.h"
     16 #include "LTOModule.h"
     17 #include "llvm/ADT/StringExtras.h"
     18 #include "llvm/Analysis/Passes.h"
     19 #include "llvm/Analysis/Verifier.h"
     20 #include "llvm/Bitcode/ReaderWriter.h"
     21 #include "llvm/Config/config.h"
     22 #include "llvm/IR/Constants.h"
     23 #include "llvm/IR/DataLayout.h"
     24 #include "llvm/IR/DerivedTypes.h"
     25 #include "llvm/IR/LLVMContext.h"
     26 #include "llvm/IR/Module.h"
     27 #include "llvm/InitializePasses.h"
     28 #include "llvm/Linker.h"
     29 #include "llvm/MC/MCAsmInfo.h"
     30 #include "llvm/MC/MCContext.h"
     31 #include "llvm/MC/SubtargetFeature.h"
     32 #include "llvm/PassManager.h"
     33 #include "llvm/Support/CommandLine.h"
     34 #include "llvm/Support/FileSystem.h"
     35 #include "llvm/Support/FormattedStream.h"
     36 #include "llvm/Support/Host.h"
     37 #include "llvm/Support/MemoryBuffer.h"
     38 #include "llvm/Support/Signals.h"
     39 #include "llvm/Support/TargetRegistry.h"
     40 #include "llvm/Support/TargetSelect.h"
     41 #include "llvm/Support/ToolOutputFile.h"
     42 #include "llvm/Support/system_error.h"
     43 #include "llvm/Target/Mangler.h"
     44 #include "llvm/Target/TargetMachine.h"
     45 #include "llvm/Target/TargetOptions.h"
     46 #include "llvm/Target/TargetRegisterInfo.h"
     47 #include "llvm/Transforms/IPO.h"
     48 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
     49 #include "llvm/Transforms/ObjCARC.h"
     50 using namespace llvm;
     51 
     52 static cl::opt<bool>
     53 DisableOpt("disable-opt", cl::init(false),
     54   cl::desc("Do not run any optimization passes"));
     55 
     56 static cl::opt<bool>
     57 DisableInline("disable-inlining", cl::init(false),
     58   cl::desc("Do not run the inliner pass"));
     59 
     60 static cl::opt<bool>
     61 DisableGVNLoadPRE("disable-gvn-loadpre", cl::init(false),
     62   cl::desc("Do not run the GVN load PRE pass"));
     63 
     64 const char* LTOCodeGenerator::getVersionString() {
     65 #ifdef LLVM_VERSION_INFO
     66   return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
     67 #else
     68   return PACKAGE_NAME " version " PACKAGE_VERSION;
     69 #endif
     70 }
     71 
     72 LTOCodeGenerator::LTOCodeGenerator()
     73   : _context(getGlobalContext()),
     74     _linker(new Module("ld-temp.o", _context)), _target(NULL),
     75     _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
     76     _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
     77     _nativeObjectFile(NULL) {
     78   InitializeAllTargets();
     79   InitializeAllTargetMCs();
     80   InitializeAllAsmPrinters();
     81   initializeLTOPasses();
     82 }
     83 
     84 LTOCodeGenerator::~LTOCodeGenerator() {
     85   delete _target;
     86   delete _nativeObjectFile;
     87   delete _linker.getModule();
     88 
     89   for (std::vector<char*>::iterator I = _codegenOptions.begin(),
     90          E = _codegenOptions.end(); I != E; ++I)
     91     free(*I);
     92 }
     93 
     94 // Initialize LTO passes. Please keep this funciton in sync with
     95 // PassManagerBuilder::populateLTOPassManager(), and make sure all LTO
     96 // passes are initialized.
     97 //
     98 void LTOCodeGenerator::initializeLTOPasses() {
     99   PassRegistry &R = *PassRegistry::getPassRegistry();
    100 
    101   initializeInternalizePassPass(R);
    102   initializeIPSCCPPass(R);
    103   initializeGlobalOptPass(R);
    104   initializeConstantMergePass(R);
    105   initializeDAHPass(R);
    106   initializeInstCombinerPass(R);
    107   initializeSimpleInlinerPass(R);
    108   initializePruneEHPass(R);
    109   initializeGlobalDCEPass(R);
    110   initializeArgPromotionPass(R);
    111   initializeJumpThreadingPass(R);
    112   initializeSROAPass(R);
    113   initializeSROA_DTPass(R);
    114   initializeSROA_SSAUpPass(R);
    115   initializeFunctionAttrsPass(R);
    116   initializeGlobalsModRefPass(R);
    117   initializeLICMPass(R);
    118   initializeGVNPass(R);
    119   initializeMemCpyOptPass(R);
    120   initializeDCEPass(R);
    121   initializeCFGSimplifyPassPass(R);
    122 }
    123 
    124 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg) {
    125   bool ret = _linker.linkInModule(mod->getLLVVMModule(), &errMsg);
    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   return !ret;
    132 }
    133 
    134 void LTOCodeGenerator::setDebugInfo(lto_debug_model debug) {
    135   switch (debug) {
    136   case LTO_DEBUG_MODEL_NONE:
    137     _emitDwarfDebugInfo = false;
    138     return;
    139 
    140   case LTO_DEBUG_MODEL_DWARF:
    141     _emitDwarfDebugInfo = true;
    142     return;
    143   }
    144   llvm_unreachable("Unknown debug format!");
    145 }
    146 
    147 void LTOCodeGenerator::setCodePICModel(lto_codegen_model model) {
    148   switch (model) {
    149   case LTO_CODEGEN_PIC_MODEL_STATIC:
    150   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    151   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    152     _codeModel = model;
    153     return;
    154   }
    155   llvm_unreachable("Unknown PIC model!");
    156 }
    157 
    158 bool LTOCodeGenerator::writeMergedModules(const char *path,
    159                                           std::string &errMsg) {
    160   if (!determineTarget(errMsg))
    161     return false;
    162 
    163   // Run the verifier on the merged modules.
    164   PassManager passes;
    165   passes.add(createVerifierPass());
    166   passes.run(*_linker.getModule());
    167 
    168   // create output file
    169   std::string ErrInfo;
    170   tool_output_file Out(path, ErrInfo, sys::fs::F_Binary);
    171   if (!ErrInfo.empty()) {
    172     errMsg = "could not open bitcode file for writing: ";
    173     errMsg += path;
    174     return false;
    175   }
    176 
    177   // write bitcode to it
    178   WriteBitcodeToFile(_linker.getModule(), Out.os());
    179   Out.os().close();
    180 
    181   if (Out.os().has_error()) {
    182     errMsg = "could not write bitcode file: ";
    183     errMsg += path;
    184     Out.os().clear_error();
    185     return false;
    186   }
    187 
    188   Out.keep();
    189   return true;
    190 }
    191 
    192 bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg) {
    193   // make unique temp .o file to put generated object file
    194   SmallString<128> Filename;
    195   int FD;
    196   error_code EC = 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(), errMsg);
    206   objFile.os().close();
    207   if (objFile.os().has_error()) {
    208     objFile.os().clear_error();
    209     sys::fs::remove(Twine(Filename));
    210     return false;
    211   }
    212 
    213   objFile.keep();
    214   if (!genResult) {
    215     sys::fs::remove(Twine(Filename));
    216     return false;
    217   }
    218 
    219   _nativeObjectPath = Filename.c_str();
    220   *name = _nativeObjectPath.c_str();
    221   return true;
    222 }
    223 
    224 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg) {
    225   const char *name;
    226   if (!compile_to_file(&name, errMsg))
    227     return NULL;
    228 
    229   // remove old buffer if compile() called twice
    230   delete _nativeObjectFile;
    231 
    232   // read .o file into memory buffer
    233   OwningPtr<MemoryBuffer> BuffPtr;
    234   if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
    235     errMsg = ec.message();
    236     sys::fs::remove(_nativeObjectPath);
    237     return NULL;
    238   }
    239   _nativeObjectFile = BuffPtr.take();
    240 
    241   // remove temp files
    242   sys::fs::remove(_nativeObjectPath);
    243 
    244   // return buffer, unless error
    245   if (_nativeObjectFile == NULL)
    246     return NULL;
    247   *length = _nativeObjectFile->getBufferSize();
    248   return _nativeObjectFile->getBufferStart();
    249 }
    250 
    251 bool LTOCodeGenerator::determineTarget(std::string &errMsg) {
    252   if (_target != NULL)
    253     return true;
    254 
    255   // if options were requested, set them
    256   if (!_codegenOptions.empty())
    257     cl::ParseCommandLineOptions(_codegenOptions.size(),
    258                                 const_cast<char **>(&_codegenOptions[0]));
    259 
    260   std::string TripleStr = _linker.getModule()->getTargetTriple();
    261   if (TripleStr.empty())
    262     TripleStr = sys::getDefaultTargetTriple();
    263   llvm::Triple Triple(TripleStr);
    264 
    265   // create target machine from info for merged modules
    266   const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
    267   if (march == NULL)
    268     return false;
    269 
    270   // The relocation model is actually a static member of TargetMachine and
    271   // needs to be set before the TargetMachine is instantiated.
    272   Reloc::Model RelocModel = Reloc::Default;
    273   switch (_codeModel) {
    274   case LTO_CODEGEN_PIC_MODEL_STATIC:
    275     RelocModel = Reloc::Static;
    276     break;
    277   case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
    278     RelocModel = Reloc::PIC_;
    279     break;
    280   case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
    281     RelocModel = Reloc::DynamicNoPIC;
    282     break;
    283   }
    284 
    285   // construct LTOModule, hand over ownership of module and target
    286   SubtargetFeatures Features;
    287   Features.getDefaultSubtargetFeatures(Triple);
    288   std::string FeatureStr = Features.getString();
    289   // Set a default CPU for Darwin triples.
    290   if (_mCpu.empty() && Triple.isOSDarwin()) {
    291     if (Triple.getArch() == llvm::Triple::x86_64)
    292       _mCpu = "core2";
    293     else if (Triple.getArch() == llvm::Triple::x86)
    294       _mCpu = "yonah";
    295   }
    296   TargetOptions Options;
    297   LTOModule::getTargetOptions(Options);
    298   _target = march->createTargetMachine(TripleStr, _mCpu, FeatureStr, Options,
    299                                        RelocModel, CodeModel::Default,
    300                                        CodeGenOpt::Aggressive);
    301   return true;
    302 }
    303 
    304 void LTOCodeGenerator::
    305 applyRestriction(GlobalValue &GV,
    306                  std::vector<const char*> &mustPreserveList,
    307                  SmallPtrSet<GlobalValue*, 8> &asmUsed,
    308                  Mangler &mangler) {
    309   SmallString<64> Buffer;
    310   mangler.getNameWithPrefix(Buffer, &GV, false);
    311 
    312   if (GV.isDeclaration())
    313     return;
    314   if (_mustPreserveSymbols.count(Buffer))
    315     mustPreserveList.push_back(GV.getName().data());
    316   if (_asmUndefinedRefs.count(Buffer))
    317     asmUsed.insert(&GV);
    318 }
    319 
    320 static void findUsedValues(GlobalVariable *LLVMUsed,
    321                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
    322   if (LLVMUsed == 0) return;
    323 
    324   ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
    325   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
    326     if (GlobalValue *GV =
    327         dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
    328       UsedValues.insert(GV);
    329 }
    330 
    331 void LTOCodeGenerator::applyScopeRestrictions() {
    332   if (_scopeRestrictionsDone) return;
    333   Module *mergedModule = _linker.getModule();
    334 
    335   // Start off with a verification pass.
    336   PassManager passes;
    337   passes.add(createVerifierPass());
    338 
    339   // mark which symbols can not be internalized
    340   MCContext Context(_target->getMCAsmInfo(), _target->getRegisterInfo(), NULL);
    341   Mangler mangler(Context, _target);
    342   std::vector<const char*> mustPreserveList;
    343   SmallPtrSet<GlobalValue*, 8> asmUsed;
    344 
    345   for (Module::iterator f = mergedModule->begin(),
    346          e = mergedModule->end(); f != e; ++f)
    347     applyRestriction(*f, mustPreserveList, asmUsed, mangler);
    348   for (Module::global_iterator v = mergedModule->global_begin(),
    349          e = mergedModule->global_end(); v !=  e; ++v)
    350     applyRestriction(*v, mustPreserveList, asmUsed, mangler);
    351   for (Module::alias_iterator a = mergedModule->alias_begin(),
    352          e = mergedModule->alias_end(); a != e; ++a)
    353     applyRestriction(*a, mustPreserveList, asmUsed, mangler);
    354 
    355   GlobalVariable *LLVMCompilerUsed =
    356     mergedModule->getGlobalVariable("llvm.compiler.used");
    357   findUsedValues(LLVMCompilerUsed, asmUsed);
    358   if (LLVMCompilerUsed)
    359     LLVMCompilerUsed->eraseFromParent();
    360 
    361   if (!asmUsed.empty()) {
    362     llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
    363     std::vector<Constant*> asmUsed2;
    364     for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
    365            e = asmUsed.end(); i !=e; ++i) {
    366       GlobalValue *GV = *i;
    367       Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
    368       asmUsed2.push_back(c);
    369     }
    370 
    371     llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
    372     LLVMCompilerUsed =
    373       new llvm::GlobalVariable(*mergedModule, ATy, false,
    374                                llvm::GlobalValue::AppendingLinkage,
    375                                llvm::ConstantArray::get(ATy, asmUsed2),
    376                                "llvm.compiler.used");
    377 
    378     LLVMCompilerUsed->setSection("llvm.metadata");
    379   }
    380 
    381   passes.add(createInternalizePass(mustPreserveList));
    382 
    383   // apply scope restrictions
    384   passes.run(*mergedModule);
    385 
    386   _scopeRestrictionsDone = true;
    387 }
    388 
    389 /// Optimize merged modules using various IPO passes
    390 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
    391                                           std::string &errMsg) {
    392   if (!this->determineTarget(errMsg))
    393     return false;
    394 
    395   Module* mergedModule = _linker.getModule();
    396 
    397   // Mark which symbols can not be internalized
    398   this->applyScopeRestrictions();
    399 
    400   // Instantiate the pass manager to organize the passes.
    401   PassManager passes;
    402 
    403   // Start off with a verification pass.
    404   passes.add(createVerifierPass());
    405 
    406   // Add an appropriate DataLayout instance for this module...
    407   passes.add(new DataLayout(*_target->getDataLayout()));
    408   _target->addAnalysisPasses(passes);
    409 
    410   // Enabling internalize here would use its AllButMain variant. It
    411   // keeps only main if it exists and does nothing for libraries. Instead
    412   // we create the pass ourselves with the symbol list provided by the linker.
    413   if (!DisableOpt)
    414     PassManagerBuilder().populateLTOPassManager(passes,
    415                                               /*Internalize=*/false,
    416                                               !DisableInline,
    417                                               DisableGVNLoadPRE);
    418 
    419   // Make sure everything is still good.
    420   passes.add(createVerifierPass());
    421 
    422   PassManager codeGenPasses;
    423 
    424   codeGenPasses.add(new DataLayout(*_target->getDataLayout()));
    425   _target->addAnalysisPasses(codeGenPasses);
    426 
    427   formatted_raw_ostream Out(out);
    428 
    429   // If the bitcode files contain ARC code and were compiled with optimization,
    430   // the ObjCARCContractPass must be run, so do it unconditionally here.
    431   codeGenPasses.add(createObjCARCContractPass());
    432 
    433   if (_target->addPassesToEmitFile(codeGenPasses, Out,
    434                                    TargetMachine::CGFT_ObjectFile)) {
    435     errMsg = "target file type not supported";
    436     return false;
    437   }
    438 
    439   // Run our queue of passes all at once now, efficiently.
    440   passes.run(*mergedModule);
    441 
    442   // Run the code generator, and write assembly file
    443   codeGenPasses.run(*mergedModule);
    444 
    445   return true;
    446 }
    447 
    448 /// setCodeGenDebugOptions - Set codegen debugging options to aid in debugging
    449 /// LTO problems.
    450 void LTOCodeGenerator::setCodeGenDebugOptions(const char *options) {
    451   for (std::pair<StringRef, StringRef> o = getToken(options);
    452        !o.first.empty(); o = getToken(o.second)) {
    453     // ParseCommandLineOptions() expects argv[0] to be program name. Lazily add
    454     // that.
    455     if (_codegenOptions.empty())
    456       _codegenOptions.push_back(strdup("libLTO"));
    457     _codegenOptions.push_back(strdup(o.first.str().c_str()));
    458   }
    459 }
    460