tools/lto/LTOCodeGenerator.cpp

//===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file implements the Link Time Optimization library. This library is 
// intended to be used by linker to optimize code at link time.
//
//===----------------------------------------------------------------------===//

#include "LTOModule.h"
#include "LTOCodeGenerator.h"

#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Linker.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/SubtargetFeature.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetSelect.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/StandardPasses.h"
#include "llvm/Support/SystemUtils.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/system_error.h"
#include "llvm/Config/config.h"
#include <cstdlib>
#include <unistd.h>
#include <fcntl.h>


using namespace llvm;

static cl::opt<bool> DisableInline("disable-inlining",
  cl::desc("Do not run the inliner pass"));


const char* LTOCodeGenerator::getVersionString()
{
#ifdef LLVM_VERSION_INFO
    return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
#else
    return PACKAGE_NAME " version " PACKAGE_VERSION;
#endif
}


LTOCodeGenerator::LTOCodeGenerator() 
    : _context(getGlobalContext()),
      _linker("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
      _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
      _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
      _nativeObjectFile(NULL)
{
    InitializeAllTargets();
    InitializeAllAsmPrinters();
}

LTOCodeGenerator::~LTOCodeGenerator()
{
    delete _target;
    delete _nativeObjectFile;
}



bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
{
  bool ret = _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);

  const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
  for (int i = 0, e = undefs.size(); i != e; ++i)
    _asmUndefinedRefs[undefs[i]] = 1;

  return ret;
}
    

bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
{
    switch (debug) {
        case LTO_DEBUG_MODEL_NONE:
            _emitDwarfDebugInfo = false;
            return false;
            
        case LTO_DEBUG_MODEL_DWARF:
            _emitDwarfDebugInfo = true;
            return false;
    }
    errMsg = "unknown debug format";
    return true;
}


bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model, 
                                       std::string& errMsg)
{
    switch (model) {
        case LTO_CODEGEN_PIC_MODEL_STATIC:
        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
            _codeModel = model;
            return false;
    }
    errMsg = "unknown pic model";
    return true;
}

void LTOCodeGenerator::setCpu(const char* mCpu)
{
  _mCpu = mCpu;
}

void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
{
    _mustPreserveSymbols[sym] = 1;
}


bool LTOCodeGenerator::writeMergedModules(const char *path,
                                          std::string &errMsg) {
  if (determineTarget(errMsg))
    return true;

  // mark which symbols can not be internalized 
  applyScopeRestrictions();

  // create output file
  std::string ErrInfo;
  tool_output_file Out(path, ErrInfo,
                       raw_fd_ostream::F_Binary);
  if (!ErrInfo.empty()) {
    errMsg = "could not open bitcode file for writing: ";
    errMsg += path;
    return true;
  }
    
  // write bitcode to it
  WriteBitcodeToFile(_linker.getModule(), Out.os());
  Out.os().close();

  if (Out.os().has_error()) {
    errMsg = "could not write bitcode file: ";
    errMsg += path;
    Out.os().clear_error();
    return true;
  }
  
  Out.keep();
  return false;
}


const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
{
    // make unique temp .o file to put generated object file
    sys::PathWithStatus uniqueObjPath("lto-llvm.o");
    if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
        uniqueObjPath.eraseFromDisk();
        return NULL;
    }
    sys::RemoveFileOnSignal(uniqueObjPath);

    // generate object file
    bool genResult = false;
    tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
    if (!errMsg.empty())
      return NULL;
    genResult = this->generateObjectFile(objFile.os(), errMsg);
    objFile.os().close();
    if (objFile.os().has_error()) {
      objFile.os().clear_error();
      return NULL;
    }
    objFile.keep();
    if ( genResult ) {
      uniqueObjPath.eraseFromDisk();
      return NULL;
    }

    const std::string& uniqueObjStr = uniqueObjPath.str();
    // remove old buffer if compile() called twice
    delete _nativeObjectFile;

    // read .o file into memory buffer
    OwningPtr<MemoryBuffer> BuffPtr;
    if (error_code ec = MemoryBuffer::getFile(uniqueObjStr.c_str(),BuffPtr))
      errMsg = ec.message();
    _nativeObjectFile = BuffPtr.take();

    // remove temp files
    uniqueObjPath.eraseFromDisk();

    // return buffer, unless error
    if ( _nativeObjectFile == NULL )
        return NULL;
    *length = _nativeObjectFile->getBufferSize();
    return _nativeObjectFile->getBufferStart();
}

bool LTOCodeGenerator::determineTarget(std::string& errMsg)
{
    if ( _target == NULL ) {
        std::string Triple = _linker.getModule()->getTargetTriple();
        if (Triple.empty())
          Triple = sys::getHostTriple();

        // create target machine from info for merged modules
        const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
        if ( march == NULL )
            return true;

        // The relocation model is actually a static member of TargetMachine
        // and needs to be set before the TargetMachine is instantiated.
        switch( _codeModel ) {
        case LTO_CODEGEN_PIC_MODEL_STATIC:
            TargetMachine::setRelocationModel(Reloc::Static);
            break;
        case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
            TargetMachine::setRelocationModel(Reloc::PIC_);
            break;
        case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
            TargetMachine::setRelocationModel(Reloc::DynamicNoPIC);
            break;
        }

        // construct LTModule, hand over ownership of module and target
        SubtargetFeatures Features;
        Features.getDefaultSubtargetFeatures(_mCpu, llvm::Triple(Triple));
        std::string FeatureStr = Features.getString();
        _target = march->createTargetMachine(Triple, FeatureStr);
    }
    return false;
}

void LTOCodeGenerator::applyRestriction(GlobalValue &GV,
                                     std::vector<const char*> &mustPreserveList,
                                        SmallPtrSet<GlobalValue*, 8> &asmUsed,
                                        Mangler &mangler) {
  SmallString<64> Buffer;
  mangler.getNameWithPrefix(Buffer, &GV, false);

  if (GV.isDeclaration())
    return;
  if (_mustPreserveSymbols.count(Buffer))
    mustPreserveList.push_back(GV.getName().data());
  if (_asmUndefinedRefs.count(Buffer))
    asmUsed.insert(&GV);
}

static void findUsedValues(GlobalVariable *LLVMUsed,
                           SmallPtrSet<GlobalValue*, 8> &UsedValues) {
  if (LLVMUsed == 0) return;

  ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
  if (Inits == 0) return;

  for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
    if (GlobalValue *GV = 
          dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
      UsedValues.insert(GV);
}

void LTOCodeGenerator::applyScopeRestrictions() {
  if (_scopeRestrictionsDone) return;
  Module *mergedModule = _linker.getModule();

  // Start off with a verification pass.
  PassManager passes;
  passes.add(createVerifierPass());

  // mark which symbols can not be internalized 
  MCContext Context(*_target->getMCAsmInfo(), NULL);
  Mangler mangler(Context, *_target->getTargetData());
  std::vector<const char*> mustPreserveList;
  SmallPtrSet<GlobalValue*, 8> asmUsed;

  for (Module::iterator f = mergedModule->begin(),
         e = mergedModule->end(); f != e; ++f)
    applyRestriction(*f, mustPreserveList, asmUsed, mangler);
  for (Module::global_iterator v = mergedModule->global_begin(), 
         e = mergedModule->global_end(); v !=  e; ++v)
    applyRestriction(*v, mustPreserveList, asmUsed, mangler);
  for (Module::alias_iterator a = mergedModule->alias_begin(),
         e = mergedModule->alias_end(); a != e; ++a)
    applyRestriction(*a, mustPreserveList, asmUsed, mangler);

  GlobalVariable *LLVMCompilerUsed =
    mergedModule->getGlobalVariable("llvm.compiler.used");
  findUsedValues(LLVMCompilerUsed, asmUsed);
  if (LLVMCompilerUsed)
    LLVMCompilerUsed->eraseFromParent();

  const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
  std::vector<Constant*> asmUsed2;
  for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
         e = asmUsed.end(); i !=e; ++i) {
    GlobalValue *GV = *i;
    Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
    asmUsed2.push_back(c);
  }

  llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
  LLVMCompilerUsed =
    new llvm::GlobalVariable(*mergedModule, ATy, false,
                             llvm::GlobalValue::AppendingLinkage,
                             llvm::ConstantArray::get(ATy, asmUsed2),
                             "llvm.compiler.used");

  LLVMCompilerUsed->setSection("llvm.metadata");

  passes.add(createInternalizePass(mustPreserveList));

  // apply scope restrictions
  passes.run(*mergedModule);
  
  _scopeRestrictionsDone = true;
}

/// Optimize merged modules using various IPO passes
bool LTOCodeGenerator::generateObjectFile(raw_ostream& out,
                                          std::string& errMsg)
{
    if ( this->determineTarget(errMsg) ) 
        return true;

    // mark which symbols can not be internalized 
    this->applyScopeRestrictions();

    Module* mergedModule = _linker.getModule();

    // if options were requested, set them
    if ( !_codegenOptions.empty() )
        cl::ParseCommandLineOptions(_codegenOptions.size(), 
                                    const_cast<char **>(&_codegenOptions[0]));

    // Instantiate the pass manager to organize the passes.
    PassManager passes;

    // Start off with a verification pass.
    passes.add(createVerifierPass());

    // Add an appropriate TargetData instance for this module...
    passes.add(new TargetData(*_target->getTargetData()));
    
    createStandardLTOPasses(&passes, /*Internalize=*/ false, !DisableInline,
                            /*VerifyEach=*/ false);

    // Make sure everything is still good.
    passes.add(createVerifierPass());

    FunctionPassManager* codeGenPasses = new FunctionPassManager(mergedModule);

    codeGenPasses->add(new TargetData(*_target->getTargetData()));

    formatted_raw_ostream Out(out);

    if (_target->addPassesToEmitFile(*codeGenPasses, Out,
                                     TargetMachine::CGFT_ObjectFile,
                                     CodeGenOpt::Aggressive)) {
      errMsg = "target file type not supported";
      return true;
    }

    // Run our queue of passes all at once now, efficiently.
    passes.run(*mergedModule);

    // Run the code generator, and write assembly file
    codeGenPasses->doInitialization();

    for (Module::iterator
           it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
      if (!it->isDeclaration())
        codeGenPasses->run(*it);

    codeGenPasses->doFinalization();
    delete codeGenPasses;

    return false; // success
}


/// Optimize merged modules using various IPO passes
void LTOCodeGenerator::setCodeGenDebugOptions(const char* options)
{
    for (std::pair<StringRef, StringRef> o = getToken(options);
         !o.first.empty(); o = getToken(o.second)) {
        // ParseCommandLineOptions() expects argv[0] to be program name.
        // Lazily add that.
        if ( _codegenOptions.empty() ) 
            _codegenOptions.push_back("libLTO");
        _codegenOptions.push_back(strdup(o.first.str().c_str()));
    }
}