lto.cpp revision fe085f3fde7676ddfc2241ed7ff4dbd68f88f326
1//===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by Devang Patel and is distributed under 6// the University of Illinois Open Source 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/Module.h" 16#include "llvm/PassManager.h" 17#include "llvm/Linker.h" 18#include "llvm/Constants.h" 19#include "llvm/DerivedTypes.h" 20#include "llvm/ModuleProvider.h" 21#include "llvm/Bitcode/ReaderWriter.h" 22#include "llvm/Support/CommandLine.h" 23#include "llvm/Support/FileUtilities.h" 24#include "llvm/Support/SystemUtils.h" 25#include "llvm/Support/Mangler.h" 26#include "llvm/Support/MemoryBuffer.h" 27#include "llvm/System/Program.h" 28#include "llvm/System/Signals.h" 29#include "llvm/Analysis/Passes.h" 30#include "llvm/Analysis/LoopPass.h" 31#include "llvm/Analysis/Verifier.h" 32#include "llvm/CodeGen/FileWriters.h" 33#include "llvm/Target/SubtargetFeature.h" 34#include "llvm/Target/TargetData.h" 35#include "llvm/Target/TargetMachine.h" 36#include "llvm/Target/TargetMachineRegistry.h" 37#include "llvm/Target/TargetAsmInfo.h" 38#include "llvm/Transforms/IPO.h" 39#include "llvm/Transforms/Scalar.h" 40#include "llvm/Analysis/LoadValueNumbering.h" 41#include "llvm/Support/MathExtras.h" 42#include "llvm/LinkTimeOptimizer.h" 43#include <fstream> 44#include <ostream> 45using namespace llvm; 46 47extern "C" 48llvm::LinkTimeOptimizer *createLLVMOptimizer() 49{ 50 llvm::LTO *l = new llvm::LTO(); 51 return l; 52} 53 54/// If symbol is not used then make it internal and let optimizer takes 55/// care of it. 56void LLVMSymbol::mayBeNotUsed() { 57 gv->setLinkage(GlobalValue::InternalLinkage); 58} 59 60// Map LLVM LinkageType to LTO LinakgeType 61static LTOLinkageTypes 62getLTOLinkageType(GlobalValue *v) 63{ 64 LTOLinkageTypes lt; 65 if (v->hasExternalLinkage()) 66 lt = LTOExternalLinkage; 67 else if (v->hasLinkOnceLinkage()) 68 lt = LTOLinkOnceLinkage; 69 else if (v->hasWeakLinkage()) 70 lt = LTOWeakLinkage; 71 else 72 // Otherwise it is internal linkage for link time optimizer 73 lt = LTOInternalLinkage; 74 return lt; 75} 76 77// Find exeternal symbols referenced by VALUE. This is a recursive function. 78static void 79findExternalRefs(Value *value, std::set<std::string> &references, 80 Mangler &mangler) { 81 82 if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) { 83 LTOLinkageTypes lt = getLTOLinkageType(gv); 84 if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5)) 85 references.insert(mangler.getValueName(gv)); 86 } 87 88 // GlobalValue, even with InternalLinkage type, may have operands with 89 // ExternalLinkage type. Do not ignore these operands. 90 if (Constant *c = dyn_cast<Constant>(value)) 91 // Handle ConstantExpr, ConstantStruct, ConstantArry etc.. 92 for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i) 93 findExternalRefs(c->getOperand(i), references, mangler); 94} 95 96/// If Module with InputFilename is available then remove it from allModules 97/// and call delete on it. 98void 99LTO::removeModule (const std::string &InputFilename) 100{ 101 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 102 if (pos == allModules.end()) 103 return; 104 105 Module *m = pos->second; 106 allModules.erase(pos); 107 delete m; 108} 109 110/// InputFilename is a LLVM bitcode file. If Module with InputFilename is 111/// available then return it. Otherwise parseInputFilename. 112Module * 113LTO::getModule(const std::string &InputFilename) 114{ 115 Module *m = NULL; 116 117 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 118 if (pos != allModules.end()) 119 m = allModules[InputFilename.c_str()]; 120 else { 121 if (MemoryBuffer *Buffer 122 = MemoryBuffer::getFile(&InputFilename[0], InputFilename.size())) { 123 m = ParseBitcodeFile(Buffer); 124 delete Buffer; 125 } 126 allModules[InputFilename.c_str()] = m; 127 } 128 return m; 129} 130 131/// InputFilename is a LLVM bitcode file. Reade this bitcode file and 132/// set corresponding target triplet string. 133void 134LTO::getTargetTriple(const std::string &InputFilename, 135 std::string &targetTriple) 136{ 137 Module *m = getModule(InputFilename); 138 if (m) 139 targetTriple = m->getTargetTriple(); 140} 141 142/// InputFilename is a LLVM bitcode file. Read it using bitcode reader. 143/// Collect global functions and symbol names in symbols vector. 144/// Collect external references in references vector. 145/// Return LTO_READ_SUCCESS if there is no error. 146enum LTOStatus 147LTO::readLLVMObjectFile(const std::string &InputFilename, 148 NameToSymbolMap &symbols, 149 std::set<std::string> &references) 150{ 151 Module *m = getModule(InputFilename); 152 if (!m) 153 return LTO_READ_FAILURE; 154 155 // Collect Target info 156 getTarget(m); 157 158 if (!Target) 159 return LTO_READ_FAILURE; 160 161 // Use mangler to add GlobalPrefix to names to match linker names. 162 // FIXME : Instead of hard coding "-" use GlobalPrefix. 163 Mangler mangler(*m, Target->getTargetAsmInfo()->getGlobalPrefix()); 164 modules.push_back(m); 165 166 for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { 167 168 LTOLinkageTypes lt = getLTOLinkageType(f); 169 170 if (!f->isDeclaration() && lt != LTOInternalLinkage 171 && strncmp (f->getName().c_str(), "llvm.", 5)) { 172 int alignment = ( 16 > f->getAlignment() ? 16 : f->getAlignment()); 173 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 174 mangler.getValueName(f), 175 Log2_32(alignment)); 176 symbols[newSymbol->getMangledName()] = newSymbol; 177 allSymbols[newSymbol->getMangledName()] = newSymbol; 178 } 179 180 // Collect external symbols referenced by this function. 181 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 182 for (BasicBlock::iterator i = b->begin(), be = b->end(); 183 i != be; ++i) 184 for (unsigned count = 0, total = i->getNumOperands(); 185 count != total; ++count) 186 findExternalRefs(i->getOperand(count), references, mangler); 187 } 188 189 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 190 v != e; ++v) { 191 LTOLinkageTypes lt = getLTOLinkageType(v); 192 if (!v->isDeclaration() && lt != LTOInternalLinkage 193 && strncmp (v->getName().c_str(), "llvm.", 5)) { 194 const TargetData *TD = Target->getTargetData(); 195 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 196 mangler.getValueName(v), 197 TD->getPreferredAlignmentLog(v)); 198 symbols[newSymbol->getMangledName()] = newSymbol; 199 allSymbols[newSymbol->getMangledName()] = newSymbol; 200 201 for (unsigned count = 0, total = v->getNumOperands(); 202 count != total; ++count) 203 findExternalRefs(v->getOperand(count), references, mangler); 204 205 } 206 } 207 208 return LTO_READ_SUCCESS; 209} 210 211/// Get TargetMachine. 212/// Use module M to find appropriate Target. 213void 214LTO::getTarget (Module *M) { 215 216 if (Target) 217 return; 218 219 std::string Err; 220 const TargetMachineRegistry::entry* March = 221 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 222 223 if (March == 0) 224 return; 225 226 // Create target 227 std::string Features; 228 Target = March->CtorFn(*M, Features); 229} 230 231/// Optimize module M using various IPO passes. Use exportList to 232/// internalize selected symbols. Target platform is selected 233/// based on information available to module M. No new target 234/// features are selected. 235enum LTOStatus 236LTO::optimize(Module *M, std::ostream &Out, 237 std::vector<const char *> &exportList) 238{ 239 // Instantiate the pass manager to organize the passes. 240 PassManager Passes; 241 242 // Collect Target info 243 getTarget(M); 244 245 if (!Target) 246 return LTO_NO_TARGET; 247 248 // Start off with a verification pass. 249 Passes.add(createVerifierPass()); 250 251 // Add an appropriate TargetData instance for this module... 252 Passes.add(new TargetData(*Target->getTargetData())); 253 254 // Internalize symbols if export list is nonemty 255 if (!exportList.empty()) 256 Passes.add(createInternalizePass(exportList)); 257 258 // Now that we internalized some globals, see if we can hack on them! 259 Passes.add(createGlobalOptimizerPass()); 260 261 // Linking modules together can lead to duplicated global constants, only 262 // keep one copy of each constant... 263 Passes.add(createConstantMergePass()); 264 265 // If the -s command line option was specified, strip the symbols out of the 266 // resulting program to make it smaller. -s is a GLD option that we are 267 // supporting. 268 Passes.add(createStripSymbolsPass()); 269 270 // Propagate constants at call sites into the functions they call. 271 Passes.add(createIPConstantPropagationPass()); 272 273 // Remove unused arguments from functions... 274 Passes.add(createDeadArgEliminationPass()); 275 276 Passes.add(createFunctionInliningPass()); // Inline small functions 277 278 Passes.add(createPruneEHPass()); // Remove dead EH info 279 280 Passes.add(createGlobalDCEPass()); // Remove dead functions 281 282 // If we didn't decide to inline a function, check to see if we can 283 // transform it to pass arguments by value instead of by reference. 284 Passes.add(createArgumentPromotionPass()); 285 286 // The IPO passes may leave cruft around. Clean up after them. 287 Passes.add(createInstructionCombiningPass()); 288 289 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 290 291 // Run a few AA driven optimizations here and now, to cleanup the code. 292 Passes.add(createGlobalsModRefPass()); // IP alias analysis 293 294 Passes.add(createLICMPass()); // Hoist loop invariants 295 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 296 Passes.add(createGCSEPass()); // Remove common subexprs 297 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 298 299 // Cleanup and simplify the code after the scalar optimizations. 300 Passes.add(createInstructionCombiningPass()); 301 302 // Delete basic blocks, which optimization passes may have killed... 303 Passes.add(createCFGSimplificationPass()); 304 305 // Now that we have optimized the program, discard unreachable functions... 306 Passes.add(createGlobalDCEPass()); 307 308 // Make sure everything is still good. 309 Passes.add(createVerifierPass()); 310 311 FunctionPassManager *CodeGenPasses = 312 new FunctionPassManager(new ExistingModuleProvider(M)); 313 314 CodeGenPasses->add(new TargetData(*Target->getTargetData())); 315 316 MachineCodeEmitter *MCE = 0; 317 318 switch (Target->addPassesToEmitFile(*CodeGenPasses, Out, 319 TargetMachine::AssemblyFile, true)) { 320 default: 321 case FileModel::Error: 322 return LTO_WRITE_FAILURE; 323 case FileModel::AsmFile: 324 break; 325 case FileModel::MachOFile: 326 MCE = AddMachOWriter(*CodeGenPasses, Out, *Target); 327 break; 328 case FileModel::ElfFile: 329 MCE = AddELFWriter(*CodeGenPasses, Out, *Target); 330 break; 331 } 332 333 if (Target->addPassesToEmitFileFinish(*CodeGenPasses, MCE, true)) 334 return LTO_WRITE_FAILURE; 335 336 // Run our queue of passes all at once now, efficiently. 337 Passes.run(*M); 338 339 // Run the code generator, if present. 340 CodeGenPasses->doInitialization(); 341 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { 342 if (!I->isDeclaration()) 343 CodeGenPasses->run(*I); 344 } 345 CodeGenPasses->doFinalization(); 346 347 return LTO_OPT_SUCCESS; 348} 349 350///Link all modules together and optimize them using IPO. Generate 351/// native object file using OutputFilename 352/// Return appropriate LTOStatus. 353enum LTOStatus 354LTO::optimizeModules(const std::string &OutputFilename, 355 std::vector<const char *> &exportList, 356 std::string &targetTriple, 357 bool saveTemps, 358 const char *FinalOutputFilename) 359{ 360 if (modules.empty()) 361 return LTO_NO_WORK; 362 363 std::ios::openmode io_mode = 364 std::ios::out | std::ios::trunc | std::ios::binary; 365 std::string *errMsg = NULL; 366 Module *bigOne = modules[0]; 367 Linker theLinker("LinkTimeOptimizer", bigOne, false); 368 for (unsigned i = 1, e = modules.size(); i != e; ++i) 369 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 370 return LTO_MODULE_MERGE_FAILURE; 371 // all modules have been handed off to the linker. 372 modules.clear(); 373 374 sys::Path FinalOutputPath(FinalOutputFilename); 375 FinalOutputPath.eraseSuffix(); 376 377 if (saveTemps) { 378 std::string tempFileName(FinalOutputPath.c_str()); 379 tempFileName += "0.bc"; 380 std::ofstream Out(tempFileName.c_str(), io_mode); 381 WriteBitcodeToFile(bigOne, Out); 382 } 383 384 // Strip leading underscore because it was added to match names 385 // seen by linker. 386 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 387 const char *name = exportList[i]; 388 NameToSymbolMap::iterator itr = allSymbols.find(name); 389 if (itr != allSymbols.end()) 390 exportList[i] = allSymbols[name]->getName(); 391 } 392 393 394 std::string ErrMsg; 395 sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg); 396 if (TempDir.isEmpty()) { 397 cerr << "lto: " << ErrMsg << "\n"; 398 return LTO_WRITE_FAILURE; 399 } 400 sys::Path tmpAsmFilePath(TempDir); 401 if (!tmpAsmFilePath.appendComponent("lto")) { 402 cerr << "lto: " << ErrMsg << "\n"; 403 TempDir.eraseFromDisk(true); 404 return LTO_WRITE_FAILURE; 405 } 406 if (tmpAsmFilePath.createTemporaryFileOnDisk(true, &ErrMsg)) { 407 cerr << "lto: " << ErrMsg << "\n"; 408 TempDir.eraseFromDisk(true); 409 return LTO_WRITE_FAILURE; 410 } 411 sys::RemoveFileOnSignal(tmpAsmFilePath); 412 413 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 414 if (!asmFile.is_open() || asmFile.bad()) { 415 if (tmpAsmFilePath.exists()) { 416 tmpAsmFilePath.eraseFromDisk(); 417 TempDir.eraseFromDisk(true); 418 } 419 return LTO_WRITE_FAILURE; 420 } 421 422 enum LTOStatus status = optimize(bigOne, asmFile, exportList); 423 asmFile.close(); 424 if (status != LTO_OPT_SUCCESS) { 425 tmpAsmFilePath.eraseFromDisk(); 426 TempDir.eraseFromDisk(true); 427 return status; 428 } 429 430 if (saveTemps) { 431 std::string tempFileName(FinalOutputPath.c_str()); 432 tempFileName += "1.bc"; 433 std::ofstream Out(tempFileName.c_str(), io_mode); 434 WriteBitcodeToFile(bigOne, Out); 435 } 436 437 targetTriple = bigOne->getTargetTriple(); 438 439 // Run GCC to assemble and link the program into native code. 440 // 441 // Note: 442 // We can't just assemble and link the file with the system assembler 443 // and linker because we don't know where to put the _start symbol. 444 // GCC mysteriously knows how to do it. 445 const sys::Path gcc = sys::Program::FindProgramByName("gcc"); 446 if (gcc.isEmpty()) { 447 tmpAsmFilePath.eraseFromDisk(); 448 TempDir.eraseFromDisk(true); 449 return LTO_ASM_FAILURE; 450 } 451 452 std::vector<const char*> args; 453 args.push_back(gcc.c_str()); 454 args.push_back("-c"); 455 args.push_back("-x"); 456 args.push_back("assembler"); 457 args.push_back("-o"); 458 args.push_back(OutputFilename.c_str()); 459 args.push_back(tmpAsmFilePath.c_str()); 460 args.push_back(0); 461 462 if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1, 0, &ErrMsg)) { 463 cerr << "lto: " << ErrMsg << "\n"; 464 return LTO_ASM_FAILURE; 465 } 466 467 tmpAsmFilePath.eraseFromDisk(); 468 TempDir.eraseFromDisk(true); 469 470 return LTO_OPT_SUCCESS; 471} 472 473void LTO::printVersion() { 474 cl::PrintVersionMessage(); 475} 476 477/// Unused pure-virtual destructor. Must remain empty. 478LinkTimeOptimizer::~LinkTimeOptimizer() {} 479 480/// Destruct LTO. Delete all modules, symbols and target. 481LTO::~LTO() { 482 483 for (std::vector<Module *>::iterator itr = modules.begin(), e = modules.end(); 484 itr != e; ++itr) 485 delete *itr; 486 487 modules.clear(); 488 489 for (NameToSymbolMap::iterator itr = allSymbols.begin(), e = allSymbols.end(); 490 itr != e; ++itr) 491 delete itr->second; 492 493 allSymbols.clear(); 494 495 delete Target; 496} 497