tools/lto/LTOCodeGenerator.cpp

   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 "LTOModule.h"
  16 #include "LTOCodeGenerator.h"
  17 #include "llvm/Constants.h"
  18 #include "llvm/DerivedTypes.h"
  19 #include "llvm/Linker.h"
  20 #include "llvm/LLVMContext.h"
  21 #include "llvm/Module.h"
  22 #include "llvm/PassManager.h"
  23 #include "llvm/ADT/StringExtras.h"
  24 #include "llvm/ADT/Triple.h"
  25 #include "llvm/Analysis/Passes.h"
  26 #include "llvm/Bitcode/ReaderWriter.h"
  27 #include "llvm/MC/MCAsmInfo.h"
  28 #include "llvm/MC/MCContext.h"
  29 #include "llvm/MC/SubtargetFeature.h"
  30 #include "llvm/Target/Mangler.h"
  31 #include "llvm/Target/TargetOptions.h"
  32 #include "llvm/Target/TargetData.h"
  33 #include "llvm/Target/TargetMachine.h"
  34 #include "llvm/Target/TargetRegistry.h"
  35 #include "llvm/Target/TargetSelect.h"
  36 #include "llvm/Support/CommandLine.h"
  37 #include "llvm/Support/FormattedStream.h"
  38 #include "llvm/Support/MemoryBuffer.h"
  39 #include "llvm/Support/PassManagerBuilder.h"
  40 #include "llvm/Support/SystemUtils.h"
  41 #include "llvm/Support/ToolOutputFile.h"
  42 #include "llvm/Support/Host.h"
  43 #include "llvm/Support/Program.h"
  44 #include "llvm/Support/Signals.h"
  45 #include "llvm/Support/system_error.h"
  46 #include "llvm/Config/config.h"
  47 #include <cstdlib>
  48 #include <unistd.h>
  49 #include <fcntl.h>
  50
  51
  52 using namespace llvm;
  53
  54 static cl::opt<bool> DisableInline("disable-inlining",
  55   cl::desc("Do not run the inliner pass"));
  56
  57
  58 const char* LTOCodeGenerator::getVersionString()
  59 {
  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
  68 LTOCodeGenerator::LTOCodeGenerator()
  69     : _context(getGlobalContext()),
  70       _linker("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
  71       _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
  72       _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
  73       _nativeObjectFile(NULL)
  74 {
  75     InitializeAllTargets();
  76     InitializeAllAsmPrinters();
  77 }
  78
  79 LTOCodeGenerator::~LTOCodeGenerator()
  80 {
  81     delete _target;
  82     delete _nativeObjectFile;
  83 }
  84
  85
  86
  87 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
  88 {
  89
  90   if(mod->getLLVVMModule()->MaterializeAllPermanently(&errMsg))
  91     return true;
  92
  93   bool ret = _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
  94
  95   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
  96   for (int i = 0, e = undefs.size(); i != e; ++i)
  97     _asmUndefinedRefs[undefs[i]] = 1;
  98
  99   return ret;
 100 }
 101
 102
 103 bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
 104 {
 105     switch (debug) {
 106         case LTO_DEBUG_MODEL_NONE:
 107             _emitDwarfDebugInfo = false;
 108             return false;
 109
 110         case LTO_DEBUG_MODEL_DWARF:
 111             _emitDwarfDebugInfo = true;
 112             return false;
 113     }
 114     errMsg = "unknown debug format";
 115     return true;
 116 }
 117
 118
 119 bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
 120                                        std::string& errMsg)
 121 {
 122     switch (model) {
 123         case LTO_CODEGEN_PIC_MODEL_STATIC:
 124         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 125         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 126             _codeModel = model;
 127             return false;
 128     }
 129     errMsg = "unknown pic model";
 130     return true;
 131 }
 132
 133 void LTOCodeGenerator::setCpu(const char* mCpu)
 134 {
 135   _mCpu = mCpu;
 136 }
 137
 138 void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
 139 {
 140     _mustPreserveSymbols[sym] = 1;
 141 }
 142
 143
 144 bool LTOCodeGenerator::writeMergedModules(const char *path,
 145                                           std::string &errMsg) {
 146   if (determineTarget(errMsg))
 147     return true;
 148
 149   // mark which symbols can not be internalized
 150   applyScopeRestrictions();
 151
 152   // create output file
 153   std::string ErrInfo;
 154   tool_output_file Out(path, ErrInfo,
 155                        raw_fd_ostream::F_Binary);
 156   if (!ErrInfo.empty()) {
 157     errMsg = "could not open bitcode file for writing: ";
 158     errMsg += path;
 159     return true;
 160   }
 161
 162   // write bitcode to it
 163   WriteBitcodeToFile(_linker.getModule(), Out.os());
 164   Out.os().close();
 165
 166   if (Out.os().has_error()) {
 167     errMsg = "could not write bitcode file: ";
 168     errMsg += path;
 169     Out.os().clear_error();
 170     return true;
 171   }
 172
 173   Out.keep();
 174   return false;
 175 }
 176
 177
 178 bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg)
 179 {
 180   // make unique temp .o file to put generated object file
 181   sys::PathWithStatus uniqueObjPath("lto-llvm.o");
 182   if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
 183     uniqueObjPath.eraseFromDisk();
 184     return true;
 185   }
 186   sys::RemoveFileOnSignal(uniqueObjPath);
 187
 188   // generate object file
 189   bool genResult = false;
 190   tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
 191   if (!errMsg.empty())
 192     return NULL;
 193   genResult = this->generateObjectFile(objFile.os(), errMsg);
 194   objFile.os().close();
 195   if (objFile.os().has_error()) {
 196     objFile.os().clear_error();
 197     return true;
 198   }
 199   objFile.keep();
 200   if ( genResult ) {
 201     uniqueObjPath.eraseFromDisk();
 202     return true;
 203   }
 204
 205   _nativeObjectPath = uniqueObjPath.str();
 206   *name = _nativeObjectPath.c_str();
 207   return false;
 208 }
 209
 210 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
 211 {
 212   const char *name;
 213   if (compile_to_file(&name, errMsg))
 214     return NULL;
 215
 216   // remove old buffer if compile() called twice
 217   delete _nativeObjectFile;
 218
 219   // read .o file into memory buffer
 220   OwningPtr<MemoryBuffer> BuffPtr;
 221   if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
 222     errMsg = ec.message();
 223     return NULL;
 224   }
 225   _nativeObjectFile = BuffPtr.take();
 226
 227   // remove temp files
 228   sys::Path(_nativeObjectPath).eraseFromDisk();
 229
 230   // return buffer, unless error
 231   if ( _nativeObjectFile == NULL )
 232     return NULL;
 233   *length = _nativeObjectFile->getBufferSize();
 234   return _nativeObjectFile->getBufferStart();
 235 }
 236
 237 bool LTOCodeGenerator::determineTarget(std::string& errMsg)
 238 {
 239     if ( _target == NULL ) {
 240         std::string Triple = _linker.getModule()->getTargetTriple();
 241         if (Triple.empty())
 242           Triple = sys::getHostTriple();
 243
 244         // create target machine from info for merged modules
 245         const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
 246         if ( march == NULL )
 247             return true;
 248
 249         // The relocation model is actually a static member of TargetMachine
 250         // and needs to be set before the TargetMachine is instantiated.
 251         switch( _codeModel ) {
 252         case LTO_CODEGEN_PIC_MODEL_STATIC:
 253             TargetMachine::setRelocationModel(Reloc::Static);
 254             break;
 255         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 256             TargetMachine::setRelocationModel(Reloc::PIC_);
 257             break;
 258         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 259             TargetMachine::setRelocationModel(Reloc::DynamicNoPIC);
 260             break;
 261         }
 262
 263         // construct LTModule, hand over ownership of module and target
 264         SubtargetFeatures Features;
 265         Features.getDefaultSubtargetFeatures(llvm::Triple(Triple));
 266         std::string FeatureStr = Features.getString();
 267         _target = march->createTargetMachine(Triple, _mCpu, FeatureStr);
 268     }
 269     return false;
 270 }
 271
 272 void LTOCodeGenerator::applyRestriction(GlobalValue &GV,
 273                                      std::vector<const char*> &mustPreserveList,
 274                                         SmallPtrSet<GlobalValue*, 8> &asmUsed,
 275                                         Mangler &mangler) {
 276   SmallString<64> Buffer;
 277   mangler.getNameWithPrefix(Buffer, &GV, false);
 278
 279   if (GV.isDeclaration())
 280     return;
 281   if (_mustPreserveSymbols.count(Buffer))
 282     mustPreserveList.push_back(GV.getName().data());
 283   if (_asmUndefinedRefs.count(Buffer))
 284     asmUsed.insert(&GV);
 285 }
 286
 287 static void findUsedValues(GlobalVariable *LLVMUsed,
 288                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
 289   if (LLVMUsed == 0) return;
 290
 291   ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
 292   if (Inits == 0) return;
 293
 294   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
 295     if (GlobalValue *GV =
 296           dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
 297       UsedValues.insert(GV);
 298 }
 299
 300 void LTOCodeGenerator::applyScopeRestrictions() {
 301   if (_scopeRestrictionsDone) return;
 302   Module *mergedModule = _linker.getModule();
 303
 304   // Start off with a verification pass.
 305   PassManager passes;
 306   passes.add(createVerifierPass());
 307
 308   // mark which symbols can not be internalized
 309   MCContext Context(*_target->getMCAsmInfo(), NULL);
 310   Mangler mangler(Context, *_target->getTargetData());
 311   std::vector<const char*> mustPreserveList;
 312   SmallPtrSet<GlobalValue*, 8> asmUsed;
 313
 314   for (Module::iterator f = mergedModule->begin(),
 315          e = mergedModule->end(); f != e; ++f)
 316     applyRestriction(*f, mustPreserveList, asmUsed, mangler);
 317   for (Module::global_iterator v = mergedModule->global_begin(),
 318          e = mergedModule->global_end(); v !=  e; ++v)
 319     applyRestriction(*v, mustPreserveList, asmUsed, mangler);
 320   for (Module::alias_iterator a = mergedModule->alias_begin(),
 321          e = mergedModule->alias_end(); a != e; ++a)
 322     applyRestriction(*a, mustPreserveList, asmUsed, mangler);
 323
 324   GlobalVariable *LLVMCompilerUsed =
 325     mergedModule->getGlobalVariable("llvm.compiler.used");
 326   findUsedValues(LLVMCompilerUsed, asmUsed);
 327   if (LLVMCompilerUsed)
 328     LLVMCompilerUsed->eraseFromParent();
 329
 330   const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
 331   std::vector<Constant*> asmUsed2;
 332   for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
 333          e = asmUsed.end(); i !=e; ++i) {
 334     GlobalValue *GV = *i;
 335     Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
 336     asmUsed2.push_back(c);
 337   }
 338
 339   llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
 340   LLVMCompilerUsed =
 341     new llvm::GlobalVariable(*mergedModule, ATy, false,
 342                              llvm::GlobalValue::AppendingLinkage,
 343                              llvm::ConstantArray::get(ATy, asmUsed2),
 344                              "llvm.compiler.used");
 345
 346   LLVMCompilerUsed->setSection("llvm.metadata");
 347
 348   passes.add(createInternalizePass(mustPreserveList));
 349
 350   // apply scope restrictions
 351   passes.run(*mergedModule);
 352
 353   _scopeRestrictionsDone = true;
 354 }
 355
 356 /// Optimize merged modules using various IPO passes
 357 bool LTOCodeGenerator::generateObjectFile(raw_ostream &out,
 358                                           std::string &errMsg) {
 359     if ( this->determineTarget(errMsg) )
 360         return true;
 361
 362     // mark which symbols can not be internalized
 363     this->applyScopeRestrictions();
 364
 365     Module* mergedModule = _linker.getModule();
 366
 367     // if options were requested, set them
 368     if ( !_codegenOptions.empty() )
 369         cl::ParseCommandLineOptions(_codegenOptions.size(),
 370                                     const_cast<char **>(&_codegenOptions[0]));
 371
 372     // Instantiate the pass manager to organize the passes.
 373     PassManager passes;
 374
 375     // Start off with a verification pass.
 376     passes.add(createVerifierPass());
 377
 378     // Add an appropriate TargetData instance for this module...
 379     passes.add(new TargetData(*_target->getTargetData()));
 380
 381     PassManagerBuilder().populateLTOPassManager(passes, /*Internalize=*/ false,
 382                                                 !DisableInline);
 383
 384     // Make sure everything is still good.
 385     passes.add(createVerifierPass());
 386
 387     FunctionPassManager *codeGenPasses = new FunctionPassManager(mergedModule);
 388
 389     codeGenPasses->add(new TargetData(*_target->getTargetData()));
 390
 391     formatted_raw_ostream Out(out);
 392
 393     if (_target->addPassesToEmitFile(*codeGenPasses, Out,
 394                                      TargetMachine::CGFT_ObjectFile,
 395                                      CodeGenOpt::Aggressive)) {
 396       errMsg = "target file type not supported";
 397       return true;
 398     }
 399
 400     // Run our queue of passes all at once now, efficiently.
 401     passes.run(*mergedModule);
 402
 403     // Run the code generator, and write assembly file
 404     codeGenPasses->doInitialization();
 405
 406     for (Module::iterator
 407            it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
 408       if (!it->isDeclaration())
 409         codeGenPasses->run(*it);
 410
 411     codeGenPasses->doFinalization();
 412     delete codeGenPasses;
 413
 414     return false; // success
 415 }
 416
 417
 418 /// Optimize merged modules using various IPO passes
 419 void LTOCodeGenerator::setCodeGenDebugOptions(const char* options)
 420 {
 421     for (std::pair<StringRef, StringRef> o = getToken(options);
 422          !o.first.empty(); o = getToken(o.second)) {
 423         // ParseCommandLineOptions() expects argv[0] to be program name.
 424         // Lazily add that.
 425         if ( _codegenOptions.empty() )
 426             _codegenOptions.push_back("libLTO");
 427         _codegenOptions.push_back(strdup(o.first.str().c_str()));
 428     }
 429 }