lto.cpp revision 6152b7ec25b8d225dc1e146e241d1c6061c8221b
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 implementes 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/LinkTimeOptimizer.h" 40#include <fstream> 41#include <iostream> 42 43using namespace llvm; 44 45extern "C" 46llvm::LinkTimeOptimizer *createLLVMOptimizer() 47{ 48 llvm::LTO *l = new llvm::LTO(); 49 return l; 50} 51 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 bytecode 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 m = ParseBytecodeFile(InputFilename); 122 allModules[InputFilename.c_str()] = m; 123 } 124 return m; 125} 126 127/// InputFilename is a LLVM bytecode file. Reade this bytecode file and 128/// set corresponding target triplet string. 129void 130LTO::getTargetTriple(const std::string &InputFilename, 131 std::string &targetTriple) 132{ 133 Module *m = getModule(InputFilename); 134 if (m) 135 targetTriple = m->getTargetTriple(); 136} 137 138/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. 139/// Collect global functions and symbol names in symbols vector. 140/// Collect external references in references vector. 141/// Return LTO_READ_SUCCESS if there is no error. 142enum LTOStatus 143LTO::readLLVMObjectFile(const std::string &InputFilename, 144 NameToSymbolMap &symbols, 145 std::set<std::string> &references) 146{ 147 Module *m = getModule(InputFilename); 148 if (!m) 149 return LTO_READ_FAILURE; 150 151 // Collect Target info 152 if (!Target) 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 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 170 mangler.getValueName(f)); 171 symbols[newSymbol->getMangledName()] = newSymbol; 172 allSymbols[newSymbol->getMangledName()] = newSymbol; 173 } 174 175 // Collect external symbols referenced by this function. 176 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 177 for (BasicBlock::iterator i = b->begin(), be = b->end(); 178 i != be; ++i) 179 for (unsigned count = 0, total = i->getNumOperands(); 180 count != total; ++count) 181 findExternalRefs(i->getOperand(count), references, mangler); 182 } 183 184 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 185 v != e; ++v) { 186 LTOLinkageTypes lt = getLTOLinkageType(v); 187 if (!v->isExternal() && lt != LTOInternalLinkage 188 && strncmp (v->getName().c_str(), "llvm.", 5)) { 189 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 190 mangler.getValueName(v)); 191 symbols[newSymbol->getMangledName()] = newSymbol; 192 allSymbols[newSymbol->getMangledName()] = newSymbol; 193 194 for (unsigned count = 0, total = v->getNumOperands(); 195 count != total; ++count) 196 findExternalRefs(v->getOperand(count), references, mangler); 197 198 } 199 } 200 201 return LTO_READ_SUCCESS; 202} 203 204/// Get TargetMachine. 205/// Use module M to find appropriate Target. 206void 207LTO::getTarget (Module *M) { 208 209 std::string Err; 210 const TargetMachineRegistry::Entry* March = 211 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 212 213 if (March == 0) 214 return; 215 216 // Create target 217 std::string Features; 218 Target = March->CtorFn(*M, Features); 219} 220 221/// Optimize module M using various IPO passes. Use exportList to 222/// internalize selected symbols. Target platform is selected 223/// based on information available to module M. No new target 224/// features are selected. 225enum LTOStatus 226LTO::optimize(Module *M, std::ostream &Out, 227 std::vector<const char *> &exportList) 228{ 229 // Instantiate the pass manager to organize the passes. 230 PassManager Passes; 231 232 // Collect Target info 233 if (!Target) 234 getTarget(M); 235 236 if (!Target) 237 return LTO_NO_TARGET; 238 239 // Start off with a verification pass. 240 Passes.add(createVerifierPass()); 241 242 // Add an appropriate TargetData instance for this module... 243 Passes.add(new TargetData(*Target->getTargetData())); 244 245 // Often if the programmer does not specify proper prototypes for the 246 // functions they are calling, they end up calling a vararg version of the 247 // function that does not get a body filled in (the real function has typed 248 // arguments). This pass merges the two functions. 249 Passes.add(createFunctionResolvingPass()); 250 251 // Internalize symbols if export list is nonemty 252 if (!exportList.empty()) 253 Passes.add(createInternalizePass(exportList)); 254 255 // Now that we internalized some globals, see if we can hack on them! 256 Passes.add(createGlobalOptimizerPass()); 257 258 // Linking modules together can lead to duplicated global constants, only 259 // keep one copy of each constant... 260 Passes.add(createConstantMergePass()); 261 262 // If the -s command line option was specified, strip the symbols out of the 263 // resulting program to make it smaller. -s is a GLD option that we are 264 // supporting. 265 Passes.add(createStripSymbolsPass()); 266 267 // Propagate constants at call sites into the functions they call. 268 Passes.add(createIPConstantPropagationPass()); 269 270 // Remove unused arguments from functions... 271 Passes.add(createDeadArgEliminationPass()); 272 273 Passes.add(createFunctionInliningPass()); // Inline small functions 274 275 Passes.add(createPruneEHPass()); // Remove dead EH info 276 277 Passes.add(createGlobalDCEPass()); // Remove dead functions 278 279 // If we didn't decide to inline a function, check to see if we can 280 // transform it to pass arguments by value instead of by reference. 281 Passes.add(createArgumentPromotionPass()); 282 283 // The IPO passes may leave cruft around. Clean up after them. 284 Passes.add(createInstructionCombiningPass()); 285 286 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 287 288 // Run a few AA driven optimizations here and now, to cleanup the code. 289 Passes.add(createGlobalsModRefPass()); // IP alias analysis 290 291 Passes.add(createLICMPass()); // Hoist loop invariants 292 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 293 Passes.add(createGCSEPass()); // Remove common subexprs 294 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 295 296 // Cleanup and simplify the code after the scalar optimizations. 297 Passes.add(createInstructionCombiningPass()); 298 299 // Delete basic blocks, which optimization passes may have killed... 300 Passes.add(createCFGSimplificationPass()); 301 302 // Now that we have optimized the program, discard unreachable functions... 303 Passes.add(createGlobalDCEPass()); 304 305 // Make sure everything is still good. 306 Passes.add(createVerifierPass()); 307 308 FunctionPassManager *CodeGenPasses = 309 new FunctionPassManager(new ExistingModuleProvider(M)); 310 311 CodeGenPasses->add(new TargetData(*Target->getTargetData())); 312 Target->addPassesToEmitFile(*CodeGenPasses, Out, TargetMachine::AssemblyFile, 313 true); 314 315 // Run our queue of passes all at once now, efficiently. 316 Passes.run(*M); 317 318 // Run the code generator, if present. 319 CodeGenPasses->doInitialization(); 320 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { 321 if (!I->isExternal()) 322 CodeGenPasses->run(*I); 323 } 324 CodeGenPasses->doFinalization(); 325 326 return LTO_OPT_SUCCESS; 327} 328 329///Link all modules together and optimize them using IPO. Generate 330/// native object file using OutputFilename 331/// Return appropriate LTOStatus. 332enum LTOStatus 333LTO::optimizeModules(const std::string &OutputFilename, 334 std::vector<const char *> &exportList, 335 std::string &targetTriple) 336{ 337 if (modules.empty()) 338 return LTO_NO_WORK; 339 340 std::ios::openmode io_mode = 341 std::ios::out | std::ios::trunc | std::ios::binary; 342 std::string *errMsg = NULL; 343 Module *bigOne = modules[0]; 344 Linker theLinker("LinkTimeOptimizer", bigOne, false); 345 for (unsigned i = 1, e = modules.size(); i != e; ++i) 346 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 347 return LTO_MODULE_MERGE_FAILURE; 348 349#if 0 350 // Enable this when -save-temps is used 351 std::ofstream Out("big.bc", io_mode); 352 WriteBytecodeToFile(bigOne, Out, true); 353#endif 354 355 // Strip leading underscore because it was added to match names 356 // seen by linker. 357 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 358 const char *name = exportList[i]; 359 NameToSymbolMap::iterator itr = allSymbols.find(name); 360 if (itr != allSymbols.end()) 361 exportList[i] = allSymbols[name]->getName(); 362 } 363 364 365 std::string ErrMsg; 366 sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg); 367 if (TempDir.isEmpty()) { 368 std::cerr << "lto: " << ErrMsg << "\n"; 369 return LTO_WRITE_FAILURE; 370 } 371 sys::Path tmpAsmFilePath(TempDir); 372 if (!tmpAsmFilePath.appendComponent("lto")) { 373 std::cerr << "lto: " << ErrMsg << "\n"; 374 TempDir.eraseFromDisk(true); 375 return LTO_WRITE_FAILURE; 376 } 377 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) { 378 std::cerr << "lto: " << ErrMsg << "\n"; 379 TempDir.eraseFromDisk(true); 380 return LTO_WRITE_FAILURE; 381 } 382 sys::RemoveFileOnSignal(tmpAsmFilePath); 383 384 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 385 if (!asmFile.is_open() || asmFile.bad()) { 386 if (tmpAsmFilePath.exists()) { 387 tmpAsmFilePath.eraseFromDisk(); 388 TempDir.eraseFromDisk(true); 389 } 390 return LTO_WRITE_FAILURE; 391 } 392 393 enum LTOStatus status = optimize(bigOne, asmFile, exportList); 394 asmFile.close(); 395 if (status != LTO_OPT_SUCCESS) { 396 tmpAsmFilePath.eraseFromDisk(); 397 TempDir.eraseFromDisk(true); 398 return status; 399 } 400 401 targetTriple = bigOne->getTargetTriple(); 402 403 // Run GCC to assemble and link the program into native code. 404 // 405 // Note: 406 // We can't just assemble and link the file with the system assembler 407 // and linker because we don't know where to put the _start symbol. 408 // GCC mysteriously knows how to do it. 409 const sys::Path gcc = sys::Program::FindProgramByName("gcc"); 410 if (gcc.isEmpty()) { 411 tmpAsmFilePath.eraseFromDisk(); 412 TempDir.eraseFromDisk(true); 413 return LTO_ASM_FAILURE; 414 } 415 416 std::vector<const char*> args; 417 args.push_back(gcc.c_str()); 418 args.push_back("-c"); 419 args.push_back("-x"); 420 args.push_back("assembler"); 421 args.push_back("-o"); 422 args.push_back(OutputFilename.c_str()); 423 args.push_back(tmpAsmFilePath.c_str()); 424 args.push_back(0); 425 426 if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1, &ErrMsg)) { 427 std::cerr << "lto: " << ErrMsg << "\n"; 428 return LTO_ASM_FAILURE; 429 } 430 431 tmpAsmFilePath.eraseFromDisk(); 432 TempDir.eraseFromDisk(true); 433 434 return LTO_OPT_SUCCESS; 435} 436 437/// Destruct LTO. Delete all modules, symbols and target. 438LTO::~LTO() { 439 440 for (std::vector<Module *>::iterator itr = modules.begin(), e = modules.end(); 441 itr != e; ++itr) 442 delete *itr; 443 444 modules.clear(); 445 446 for (NameToSymbolMap::iterator itr = allSymbols.begin(), e = allSymbols.end(); 447 itr != e; ++itr) 448 delete itr->second; 449 450 allSymbols.clear(); 451 452 delete Target; 453} 454