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
  18 #include "llvm/Constants.h"
  19 #include "llvm/DerivedTypes.h"
  20 #include "llvm/Linker.h"
  21 #include "llvm/LLVMContext.h"
  22 #include "llvm/Module.h"
  23 #include "llvm/PassManager.h"
  24 #include "llvm/ADT/StringExtras.h"
  25 #include "llvm/ADT/Triple.h"
  26 #include "llvm/Analysis/Passes.h"
  27 #include "llvm/Bitcode/ReaderWriter.h"
  28 #include "llvm/MC/MCAsmInfo.h"
  29 #include "llvm/MC/MCContext.h"
  30 #include "llvm/Target/Mangler.h"
  31 #include "llvm/Target/SubtargetFeature.h"
  32 #include "llvm/Target/TargetOptions.h"
  33 #include "llvm/Target/TargetData.h"
  34 #include "llvm/Target/TargetMachine.h"
  35 #include "llvm/Target/TargetRegistry.h"
  36 #include "llvm/Target/TargetSelect.h"
  37 #include "llvm/Support/CommandLine.h"
  38 #include "llvm/Support/FormattedStream.h"
  39 #include "llvm/Support/MemoryBuffer.h"
  40 #include "llvm/Support/StandardPasses.h"
  41 #include "llvm/Support/SystemUtils.h"
  42 #include "llvm/Support/ToolOutputFile.h"
  43 #include "llvm/Support/Host.h"
  44 #include "llvm/Support/Program.h"
  45 #include "llvm/Support/Signals.h"
  46 #include "llvm/Support/system_error.h"
  47 #include "llvm/Config/config.h"
  48 #include <cstdlib>
  49 #include <unistd.h>
  50 #include <fcntl.h>
  51
  52
  53 using namespace llvm;
  54
  55 static cl::opt<bool> DisableInline("disable-inlining",
  56   cl::desc("Do not run the inliner pass"));
  57
  58
  59 const char* LTOCodeGenerator::getVersionString()
  60 {
  61 #ifdef LLVM_VERSION_INFO
  62     return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
  63 #else
  64     return PACKAGE_NAME " version " PACKAGE_VERSION;
  65 #endif
  66 }
  67
  68
  69 LTOCodeGenerator::LTOCodeGenerator()
  70     : _context(getGlobalContext()),
  71       _linker("LinkTimeOptimizer", "ld-temp.o", _context), _target(NULL),
  72       _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
  73       _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
  74       _nativeObjectFile(NULL)
  75 {
  76     InitializeAllTargets();
  77     InitializeAllAsmPrinters();
  78 }
  79
  80 LTOCodeGenerator::~LTOCodeGenerator()
  81 {
  82     delete _target;
  83     delete _nativeObjectFile;
  84 }
  85
  86
  87
  88 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
  89 {
  90
  91   if(mod->getLLVVMModule()->MaterializeAllPermanently(&errMsg))
  92     return true;
  93
  94   bool ret = _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
  95
  96   const std::vector<const char*> &undefs = mod->getAsmUndefinedRefs();
  97   for (int i = 0, e = undefs.size(); i != e; ++i)
  98     _asmUndefinedRefs[undefs[i]] = 1;
  99
 100   return ret;
 101 }
 102
 103
 104 bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
 105 {
 106     switch (debug) {
 107         case LTO_DEBUG_MODEL_NONE:
 108             _emitDwarfDebugInfo = false;
 109             return false;
 110
 111         case LTO_DEBUG_MODEL_DWARF:
 112             _emitDwarfDebugInfo = true;
 113             return false;
 114     }
 115     errMsg = "unknown debug format";
 116     return true;
 117 }
 118
 119
 120 bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
 121                                        std::string& errMsg)
 122 {
 123     switch (model) {
 124         case LTO_CODEGEN_PIC_MODEL_STATIC:
 125         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 126         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 127             _codeModel = model;
 128             return false;
 129     }
 130     errMsg = "unknown pic model";
 131     return true;
 132 }
 133
 134 void LTOCodeGenerator::setCpu(const char* mCpu)
 135 {
 136   _mCpu = mCpu;
 137 }
 138
 139 void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
 140 {
 141     _mustPreserveSymbols[sym] = 1;
 142 }
 143
 144
 145 bool LTOCodeGenerator::writeMergedModules(const char *path,
 146                                           std::string &errMsg) {
 147   if (determineTarget(errMsg))
 148     return true;
 149
 150   // mark which symbols can not be internalized
 151   applyScopeRestrictions();
 152
 153   // create output file
 154   std::string ErrInfo;
 155   tool_output_file Out(path, ErrInfo,
 156                        raw_fd_ostream::F_Binary);
 157   if (!ErrInfo.empty()) {
 158     errMsg = "could not open bitcode file for writing: ";
 159     errMsg += path;
 160     return true;
 161   }
 162
 163   // write bitcode to it
 164   WriteBitcodeToFile(_linker.getModule(), Out.os());
 165   Out.os().close();
 166
 167   if (Out.os().has_error()) {
 168     errMsg = "could not write bitcode file: ";
 169     errMsg += path;
 170     Out.os().clear_error();
 171     return true;
 172   }
 173
 174   Out.keep();
 175   return false;
 176 }
 177
 178
 179 bool LTOCodeGenerator::compile_to_file(const char** name, std::string& errMsg)
 180 {
 181   // make unique temp .o file to put generated object file
 182   sys::PathWithStatus uniqueObjPath("lto-llvm.o");
 183   if ( uniqueObjPath.createTemporaryFileOnDisk(false, &errMsg) ) {
 184     uniqueObjPath.eraseFromDisk();
 185     return true;
 186   }
 187   sys::RemoveFileOnSignal(uniqueObjPath);
 188
 189   // generate object file
 190   bool genResult = false;
 191   tool_output_file objFile(uniqueObjPath.c_str(), errMsg);
 192   if (!errMsg.empty())
 193     return NULL;
 194   genResult = this->generateObjectFile(objFile.os(), errMsg);
 195   objFile.os().close();
 196   if (objFile.os().has_error()) {
 197     objFile.os().clear_error();
 198     return true;
 199   }
 200   objFile.keep();
 201   if ( genResult ) {
 202     uniqueObjPath.eraseFromDisk();
 203     return true;
 204   }
 205
 206   _nativeObjectPath = uniqueObjPath.str();
 207   *name = _nativeObjectPath.c_str();
 208   return false;
 209 }
 210
 211 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
 212 {
 213   const char *name;
 214   if (compile_to_file(&name, errMsg))
 215     return NULL;
 216
 217   // remove old buffer if compile() called twice
 218   delete _nativeObjectFile;
 219
 220   // read .o file into memory buffer
 221   OwningPtr<MemoryBuffer> BuffPtr;
 222   if (error_code ec = MemoryBuffer::getFile(name, BuffPtr, -1, false)) {
 223     errMsg = ec.message();
 224     return NULL;
 225   }
 226   _nativeObjectFile = BuffPtr.take();
 227
 228   // remove temp files
 229   sys::Path(_nativeObjectPath).eraseFromDisk();
 230
 231   // return buffer, unless error
 232   if ( _nativeObjectFile == NULL )
 233     return NULL;
 234   *length = _nativeObjectFile->getBufferSize();
 235   return _nativeObjectFile->getBufferStart();
 236 }
 237
 238 bool LTOCodeGenerator::determineTarget(std::string& errMsg)
 239 {
 240     if ( _target == NULL ) {
 241         std::string Triple = _linker.getModule()->getTargetTriple();
 242         if (Triple.empty())
 243           Triple = sys::getHostTriple();
 244
 245         // create target machine from info for merged modules
 246         const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
 247         if ( march == NULL )
 248             return true;
 249
 250         // The relocation model is actually a static member of TargetMachine
 251         // and needs to be set before the TargetMachine is instantiated.
 252         switch( _codeModel ) {
 253         case LTO_CODEGEN_PIC_MODEL_STATIC:
 254             TargetMachine::setRelocationModel(Reloc::Static);
 255             break;
 256         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 257             TargetMachine::setRelocationModel(Reloc::PIC_);
 258             break;
 259         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 260             TargetMachine::setRelocationModel(Reloc::DynamicNoPIC);
 261             break;
 262         }
 263
 264         // construct LTModule, hand over ownership of module and target
 265         SubtargetFeatures Features;
 266         Features.getDefaultSubtargetFeatures(_mCpu, llvm::Triple(Triple));
 267         std::string FeatureStr = Features.getString();
 268         _target = march->createTargetMachine(Triple, FeatureStr);
 269     }
 270     return false;
 271 }
 272
 273 void LTOCodeGenerator::applyRestriction(GlobalValue &GV,
 274                                      std::vector<const char*> &mustPreserveList,
 275                                         SmallPtrSet<GlobalValue*, 8> &asmUsed,
 276                                         Mangler &mangler) {
 277   SmallString<64> Buffer;
 278   mangler.getNameWithPrefix(Buffer, &GV, false);
 279
 280   if (GV.isDeclaration())
 281     return;
 282   if (_mustPreserveSymbols.count(Buffer))
 283     mustPreserveList.push_back(GV.getName().data());
 284   if (_asmUndefinedRefs.count(Buffer))
 285     asmUsed.insert(&GV);
 286 }
 287
 288 static void findUsedValues(GlobalVariable *LLVMUsed,
 289                            SmallPtrSet<GlobalValue*, 8> &UsedValues) {
 290   if (LLVMUsed == 0) return;
 291
 292   ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
 293   if (Inits == 0) return;
 294
 295   for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
 296     if (GlobalValue *GV =
 297           dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
 298       UsedValues.insert(GV);
 299 }
 300
 301 void LTOCodeGenerator::applyScopeRestrictions() {
 302   if (_scopeRestrictionsDone) return;
 303   Module *mergedModule = _linker.getModule();
 304
 305   // Start off with a verification pass.
 306   PassManager passes;
 307   passes.add(createVerifierPass());
 308
 309   // mark which symbols can not be internalized
 310   MCContext Context(*_target->getMCAsmInfo(), NULL);
 311   Mangler mangler(Context, *_target->getTargetData());
 312   std::vector<const char*> mustPreserveList;
 313   SmallPtrSet<GlobalValue*, 8> asmUsed;
 314
 315   for (Module::iterator f = mergedModule->begin(),
 316          e = mergedModule->end(); f != e; ++f)
 317     applyRestriction(*f, mustPreserveList, asmUsed, mangler);
 318   for (Module::global_iterator v = mergedModule->global_begin(),
 319          e = mergedModule->global_end(); v !=  e; ++v)
 320     applyRestriction(*v, mustPreserveList, asmUsed, mangler);
 321   for (Module::alias_iterator a = mergedModule->alias_begin(),
 322          e = mergedModule->alias_end(); a != e; ++a)
 323     applyRestriction(*a, mustPreserveList, asmUsed, mangler);
 324
 325   GlobalVariable *LLVMCompilerUsed =
 326     mergedModule->getGlobalVariable("llvm.compiler.used");
 327   findUsedValues(LLVMCompilerUsed, asmUsed);
 328   if (LLVMCompilerUsed)
 329     LLVMCompilerUsed->eraseFromParent();
 330
 331   const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
 332   std::vector<Constant*> asmUsed2;
 333   for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
 334          e = asmUsed.end(); i !=e; ++i) {
 335     GlobalValue *GV = *i;
 336     Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
 337     asmUsed2.push_back(c);
 338   }
 339
 340   llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
 341   LLVMCompilerUsed =
 342     new llvm::GlobalVariable(*mergedModule, ATy, false,
 343                              llvm::GlobalValue::AppendingLinkage,
 344                              llvm::ConstantArray::get(ATy, asmUsed2),
 345                              "llvm.compiler.used");
 346
 347   LLVMCompilerUsed->setSection("llvm.metadata");
 348
 349   passes.add(createInternalizePass(mustPreserveList));
 350
 351   // apply scope restrictions
 352   passes.run(*mergedModule);
 353
 354   _scopeRestrictionsDone = true;
 355 }
 356
 357 /// Optimize merged modules using various IPO passes
 358 bool LTOCodeGenerator::generateObjectFile(raw_ostream& out,
 359                                           std::string& errMsg)
 360 {
 361     if ( this->determineTarget(errMsg) )
 362         return true;
 363
 364     // mark which symbols can not be internalized
 365     this->applyScopeRestrictions();
 366
 367     Module* mergedModule = _linker.getModule();
 368
 369     // if options were requested, set them
 370     if ( !_codegenOptions.empty() )
 371         cl::ParseCommandLineOptions(_codegenOptions.size(),
 372                                     const_cast<char **>(&_codegenOptions[0]));
 373
 374     // Instantiate the pass manager to organize the passes.
 375     PassManager passes;
 376
 377     // Start off with a verification pass.
 378     passes.add(createVerifierPass());
 379
 380     // Add an appropriate TargetData instance for this module...
 381     passes.add(new TargetData(*_target->getTargetData()));
 382
 383     createStandardLTOPasses(&passes, /*Internalize=*/ false, !DisableInline,
 384                             /*VerifyEach=*/ false);
 385
 386     // Make sure everything is still good.
 387     passes.add(createVerifierPass());
 388
 389     FunctionPassManager* codeGenPasses = new FunctionPassManager(mergedModule);
 390
 391     codeGenPasses->add(new TargetData(*_target->getTargetData()));
 392
 393     formatted_raw_ostream Out(out);
 394
 395     if (_target->addPassesToEmitFile(*codeGenPasses, Out,
 396                                      TargetMachine::CGFT_ObjectFile,
 397                                      CodeGenOpt::Aggressive)) {
 398       errMsg = "target file type not supported";
 399       return true;
 400     }
 401
 402     // Run our queue of passes all at once now, efficiently.
 403     passes.run(*mergedModule);
 404
 405     // Run the code generator, and write assembly file
 406     codeGenPasses->doInitialization();
 407
 408     for (Module::iterator
 409            it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
 410       if (!it->isDeclaration())
 411         codeGenPasses->run(*it);
 412
 413     codeGenPasses->doFinalization();
 414     delete codeGenPasses;
 415
 416     return false; // success
 417 }
 418
 419
 420 /// Optimize merged modules using various IPO passes
 421 void LTOCodeGenerator::setCodeGenDebugOptions(const char* options)
 422 {
 423     for (std::pair<StringRef, StringRef> o = getToken(options);
 424          !o.first.empty(); o = getToken(o.second)) {
 425         // ParseCommandLineOptions() expects argv[0] to be program name.
 426         // Lazily add that.
 427         if ( _codegenOptions.empty() )
 428             _codegenOptions.push_back("libLTO");
 429         _codegenOptions.push_back(strdup(o.first.str().c_str()));
 430     }
 431 }