lto.cpp revision 11fdadf407642167c5e2b8a1ed40c66c0c6dbdf2
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/SymbolTable.h" 21#include "llvm/Bytecode/Reader.h" 22#include "llvm/Bytecode/Writer.h" 23#include "llvm/Support/CommandLine.h" 24#include "llvm/Support/FileUtilities.h" 25#include "llvm/Support/SystemUtils.h" 26#include "llvm/Support/Mangler.h" 27#include "llvm/System/Program.h" 28#include "llvm/System/Signals.h" 29#include "llvm/Analysis/Passes.h" 30#include "llvm/Analysis/Verifier.h" 31#include "llvm/Target/SubtargetFeature.h" 32#include "llvm/Target/TargetData.h" 33#include "llvm/Target/TargetMachine.h" 34#include "llvm/Target/TargetMachineRegistry.h" 35#include "llvm/Target/TargetAsmInfo.h" 36#include "llvm/Transforms/IPO.h" 37#include "llvm/Transforms/Scalar.h" 38#include "llvm/Analysis/LoadValueNumbering.h" 39#include "llvm/Support/MathExtras.h" 40#include "llvm/Support/Streams.h" 41#include "llvm/LinkTimeOptimizer.h" 42#include <fstream> 43#include <ostream> 44using namespace llvm; 45 46extern "C" 47llvm::LinkTimeOptimizer *createLLVMOptimizer() 48{ 49 llvm::LTO *l = new llvm::LTO(); 50 return l; 51} 52 53 54 55/// If symbol is not used then make it internal and let optimizer takes 56/// care of it. 57void LLVMSymbol::mayBeNotUsed() { 58 gv->setLinkage(GlobalValue::InternalLinkage); 59} 60 61// Map LLVM LinkageType to LTO LinakgeType 62static LTOLinkageTypes 63getLTOLinkageType(GlobalValue *v) 64{ 65 LTOLinkageTypes lt; 66 if (v->hasExternalLinkage()) 67 lt = LTOExternalLinkage; 68 else if (v->hasLinkOnceLinkage()) 69 lt = LTOLinkOnceLinkage; 70 else if (v->hasWeakLinkage()) 71 lt = LTOWeakLinkage; 72 else 73 // Otherwise it is internal linkage for link time optimizer 74 lt = LTOInternalLinkage; 75 return lt; 76} 77 78// Find exeternal symbols referenced by VALUE. This is a recursive function. 79static void 80findExternalRefs(Value *value, std::set<std::string> &references, 81 Mangler &mangler) { 82 83 if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) { 84 LTOLinkageTypes lt = getLTOLinkageType(gv); 85 if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5)) 86 references.insert(mangler.getValueName(gv)); 87 } 88 89 // GlobalValue, even with InternalLinkage type, may have operands with 90 // ExternalLinkage type. Do not ignore these operands. 91 if (Constant *c = dyn_cast<Constant>(value)) 92 // Handle ConstantExpr, ConstantStruct, ConstantArry etc.. 93 for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i) 94 findExternalRefs(c->getOperand(i), references, mangler); 95} 96 97/// If Module with InputFilename is available then remove it from allModules 98/// and call delete on it. 99void 100LTO::removeModule (const std::string &InputFilename) 101{ 102 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 103 if (pos == allModules.end()) 104 return; 105 106 Module *m = pos->second; 107 allModules.erase(pos); 108 delete m; 109} 110 111/// InputFilename is a LLVM bytecode file. If Module with InputFilename is 112/// available then return it. Otherwise parseInputFilename. 113Module * 114LTO::getModule(const std::string &InputFilename) 115{ 116 Module *m = NULL; 117 118 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 119 if (pos != allModules.end()) 120 m = allModules[InputFilename.c_str()]; 121 else { 122 m = ParseBytecodeFile(InputFilename); 123 allModules[InputFilename.c_str()] = m; 124 } 125 return m; 126} 127 128/// InputFilename is a LLVM bytecode file. Reade this bytecode file and 129/// set corresponding target triplet string. 130void 131LTO::getTargetTriple(const std::string &InputFilename, 132 std::string &targetTriple) 133{ 134 Module *m = getModule(InputFilename); 135 if (m) 136 targetTriple = m->getTargetTriple(); 137} 138 139/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. 140/// Collect global functions and symbol names in symbols vector. 141/// Collect external references in references vector. 142/// Return LTO_READ_SUCCESS if there is no error. 143enum LTOStatus 144LTO::readLLVMObjectFile(const std::string &InputFilename, 145 NameToSymbolMap &symbols, 146 std::set<std::string> &references) 147{ 148 Module *m = getModule(InputFilename); 149 if (!m) 150 return LTO_READ_FAILURE; 151 152 // Collect Target info 153 getTarget(m); 154 155 if (!Target) 156 return LTO_READ_FAILURE; 157 158 // Use mangler to add GlobalPrefix to names to match linker names. 159 // FIXME : Instead of hard coding "-" use GlobalPrefix. 160 Mangler mangler(*m, Target->getTargetAsmInfo()->getGlobalPrefix()); 161 modules.push_back(m); 162 163 for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { 164 165 LTOLinkageTypes lt = getLTOLinkageType(f); 166 167 if (!f->isExternal() && lt != LTOInternalLinkage 168 && strncmp (f->getName().c_str(), "llvm.", 5)) { 169 int alignment = ( 16 > f->getAlignment() ? 16 : f->getAlignment()); 170 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 171 mangler.getValueName(f), 172 Log2_32(alignment)); 173 symbols[newSymbol->getMangledName()] = newSymbol; 174 allSymbols[newSymbol->getMangledName()] = newSymbol; 175 } 176 177 // Collect external symbols referenced by this function. 178 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 179 for (BasicBlock::iterator i = b->begin(), be = b->end(); 180 i != be; ++i) 181 for (unsigned count = 0, total = i->getNumOperands(); 182 count != total; ++count) 183 findExternalRefs(i->getOperand(count), references, mangler); 184 } 185 186 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 187 v != e; ++v) { 188 LTOLinkageTypes lt = getLTOLinkageType(v); 189 if (!v->isExternal() && lt != LTOInternalLinkage 190 && strncmp (v->getName().c_str(), "llvm.", 5)) { 191 const TargetData *TD = Target->getTargetData(); 192 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 193 mangler.getValueName(v), 194 TD->getPreferredAlignmentLog(v)); 195 symbols[newSymbol->getMangledName()] = newSymbol; 196 allSymbols[newSymbol->getMangledName()] = newSymbol; 197 198 for (unsigned count = 0, total = v->getNumOperands(); 199 count != total; ++count) 200 findExternalRefs(v->getOperand(count), references, mangler); 201 202 } 203 } 204 205 return LTO_READ_SUCCESS; 206} 207 208/// Get TargetMachine. 209/// Use module M to find appropriate Target. 210void 211LTO::getTarget (Module *M) { 212 213 if (Target) 214 return; 215 216 std::string Err; 217 const TargetMachineRegistry::Entry* March = 218 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 219 220 if (March == 0) 221 return; 222 223 // Create target 224 std::string Features; 225 Target = March->CtorFn(*M, Features); 226} 227 228/// Optimize module M using various IPO passes. Use exportList to 229/// internalize selected symbols. Target platform is selected 230/// based on information available to module M. No new target 231/// features are selected. 232enum LTOStatus 233LTO::optimize(Module *M, std::ostream &Out, 234 std::vector<const char *> &exportList) 235{ 236 // Instantiate the pass manager to organize the passes. 237 PassManager Passes; 238 239 // Collect Target info 240 getTarget(M); 241 242 if (!Target) 243 return LTO_NO_TARGET; 244 245 // Start off with a verification pass. 246 Passes.add(createVerifierPass()); 247 248 // Add an appropriate TargetData instance for this module... 249 Passes.add(new TargetData(*Target->getTargetData())); 250 251 // Often if the programmer does not specify proper prototypes for the 252 // functions they are calling, they end up calling a vararg version of the 253 // function that does not get a body filled in (the real function has typed 254 // arguments). This pass merges the two functions. 255 Passes.add(createFunctionResolvingPass()); 256 257 // Internalize symbols if export list is nonemty 258 if (!exportList.empty()) 259 Passes.add(createInternalizePass(exportList)); 260 261 // Now that we internalized some globals, see if we can hack on them! 262 Passes.add(createGlobalOptimizerPass()); 263 264 // Linking modules together can lead to duplicated global constants, only 265 // keep one copy of each constant... 266 Passes.add(createConstantMergePass()); 267 268 // If the -s command line option was specified, strip the symbols out of the 269 // resulting program to make it smaller. -s is a GLD option that we are 270 // supporting. 271 Passes.add(createStripSymbolsPass()); 272 273 // Propagate constants at call sites into the functions they call. 274 Passes.add(createIPConstantPropagationPass()); 275 276 // Remove unused arguments from functions... 277 Passes.add(createDeadArgEliminationPass()); 278 279 Passes.add(createFunctionInliningPass()); // Inline small functions 280 281 Passes.add(createPruneEHPass()); // Remove dead EH info 282 283 Passes.add(createGlobalDCEPass()); // Remove dead functions 284 285 // If we didn't decide to inline a function, check to see if we can 286 // transform it to pass arguments by value instead of by reference. 287 Passes.add(createArgumentPromotionPass()); 288 289 // The IPO passes may leave cruft around. Clean up after them. 290 Passes.add(createInstructionCombiningPass()); 291 292 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 293 294 // Run a few AA driven optimizations here and now, to cleanup the code. 295 Passes.add(createGlobalsModRefPass()); // IP alias analysis 296 297 Passes.add(createLICMPass()); // Hoist loop invariants 298 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 299 Passes.add(createGCSEPass()); // Remove common subexprs 300 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 301 302 // Cleanup and simplify the code after the scalar optimizations. 303 Passes.add(createInstructionCombiningPass()); 304 305 // Delete basic blocks, which optimization passes may have killed... 306 Passes.add(createCFGSimplificationPass()); 307 308 // Now that we have optimized the program, discard unreachable functions... 309 Passes.add(createGlobalDCEPass()); 310 311 // Make sure everything is still good. 312 Passes.add(createVerifierPass()); 313 314 FunctionPassManager *CodeGenPasses = 315 new FunctionPassManager(new ExistingModuleProvider(M)); 316 317 CodeGenPasses->add(new TargetData(*Target->getTargetData())); 318 Target->addPassesToEmitFile(*CodeGenPasses, Out, TargetMachine::AssemblyFile, 319 true); 320 321 // Run our queue of passes all at once now, efficiently. 322 Passes.run(*M); 323 324 // Run the code generator, if present. 325 CodeGenPasses->doInitialization(); 326 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { 327 if (!I->isExternal()) 328 CodeGenPasses->run(*I); 329 } 330 CodeGenPasses->doFinalization(); 331 332 return LTO_OPT_SUCCESS; 333} 334 335///Link all modules together and optimize them using IPO. Generate 336/// native object file using OutputFilename 337/// Return appropriate LTOStatus. 338enum LTOStatus 339LTO::optimizeModules(const std::string &OutputFilename, 340 std::vector<const char *> &exportList, 341 std::string &targetTriple, 342 bool saveTemps, 343 const char *FinalOutputFilename) 344{ 345 if (modules.empty()) 346 return LTO_NO_WORK; 347 348 std::ios::openmode io_mode = 349 std::ios::out | std::ios::trunc | std::ios::binary; 350 std::string *errMsg = NULL; 351 Module *bigOne = modules[0]; 352 Linker theLinker("LinkTimeOptimizer", bigOne, false); 353 for (unsigned i = 1, e = modules.size(); i != e; ++i) 354 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 355 return LTO_MODULE_MERGE_FAILURE; 356 357 sys::Path FinalOutputPath(FinalOutputFilename); 358 FinalOutputPath.eraseSuffix(); 359 360 if (saveTemps) { 361 std::string tempFileName(FinalOutputPath.c_str()); 362 tempFileName += "0.bc"; 363 std::ofstream Out(tempFileName.c_str(), io_mode); 364 OStream L(Out); 365 WriteBytecodeToFile(bigOne, L, true); 366 } 367 368 // Strip leading underscore because it was added to match names 369 // seen by linker. 370 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 371 const char *name = exportList[i]; 372 NameToSymbolMap::iterator itr = allSymbols.find(name); 373 if (itr != allSymbols.end()) 374 exportList[i] = allSymbols[name]->getName(); 375 } 376 377 378 std::string ErrMsg; 379 sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg); 380 if (TempDir.isEmpty()) { 381 cerr << "lto: " << ErrMsg << "\n"; 382 return LTO_WRITE_FAILURE; 383 } 384 sys::Path tmpAsmFilePath(TempDir); 385 if (!tmpAsmFilePath.appendComponent("lto")) { 386 cerr << "lto: " << ErrMsg << "\n"; 387 TempDir.eraseFromDisk(true); 388 return LTO_WRITE_FAILURE; 389 } 390 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) { 391 cerr << "lto: " << ErrMsg << "\n"; 392 TempDir.eraseFromDisk(true); 393 return LTO_WRITE_FAILURE; 394 } 395 sys::RemoveFileOnSignal(tmpAsmFilePath); 396 397 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 398 if (!asmFile.is_open() || asmFile.bad()) { 399 if (tmpAsmFilePath.exists()) { 400 tmpAsmFilePath.eraseFromDisk(); 401 TempDir.eraseFromDisk(true); 402 } 403 return LTO_WRITE_FAILURE; 404 } 405 406 enum LTOStatus status = optimize(bigOne, asmFile, exportList); 407 asmFile.close(); 408 if (status != LTO_OPT_SUCCESS) { 409 tmpAsmFilePath.eraseFromDisk(); 410 TempDir.eraseFromDisk(true); 411 return status; 412 } 413 414 if (saveTemps) { 415 std::string tempFileName(FinalOutputPath.c_str()); 416 tempFileName += "1.bc"; 417 std::ofstream Out(tempFileName.c_str(), io_mode); 418 OStream L(Out); 419 WriteBytecodeToFile(bigOne, L, true); 420 } 421 422 targetTriple = bigOne->getTargetTriple(); 423 424 // Run GCC to assemble and link the program into native code. 425 // 426 // Note: 427 // We can't just assemble and link the file with the system assembler 428 // and linker because we don't know where to put the _start symbol. 429 // GCC mysteriously knows how to do it. 430 const sys::Path gcc = sys::Program::FindProgramByName("gcc"); 431 if (gcc.isEmpty()) { 432 tmpAsmFilePath.eraseFromDisk(); 433 TempDir.eraseFromDisk(true); 434 return LTO_ASM_FAILURE; 435 } 436 437 std::vector<const char*> args; 438 args.push_back(gcc.c_str()); 439 args.push_back("-c"); 440 args.push_back("-x"); 441 args.push_back("assembler"); 442 args.push_back("-o"); 443 args.push_back(OutputFilename.c_str()); 444 args.push_back(tmpAsmFilePath.c_str()); 445 args.push_back(0); 446 447 if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1, &ErrMsg)) { 448 cerr << "lto: " << ErrMsg << "\n"; 449 return LTO_ASM_FAILURE; 450 } 451 452 tmpAsmFilePath.eraseFromDisk(); 453 TempDir.eraseFromDisk(true); 454 455 return LTO_OPT_SUCCESS; 456} 457 458/// Destruct LTO. Delete all modules, symbols and target. 459LTO::~LTO() { 460 461 for (std::vector<Module *>::iterator itr = modules.begin(), e = modules.end(); 462 itr != e; ++itr) 463 delete *itr; 464 465 modules.clear(); 466 467 for (NameToSymbolMap::iterator itr = allSymbols.begin(), e = allSymbols.end(); 468 itr != e; ++itr) 469 delete itr->second; 470 471 allSymbols.clear(); 472 473 delete Target; 474} 475