lto.cpp revision 2a4dd685357e2fd248ab458d3bed4ea21350815b
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/Transforms/IPO.h" 36#include "llvm/Transforms/Scalar.h" 37#include "llvm/Analysis/LoadValueNumbering.h" 38#include "llvm/LinkTimeOptimizer.h" 39#include <fstream> 40#include <iostream> 41 42using namespace llvm; 43 44extern "C" 45llvm::LinkTimeOptimizer *createLLVMOptimizer() 46{ 47 llvm::LTO *l = new llvm::LTO(); 48 return l; 49} 50 51 52 53/// If symbol is not used then make it internal and let optimizer takes 54/// care of it. 55void LLVMSymbol::mayBeNotUsed() { 56 gv->setLinkage(GlobalValue::InternalLinkage); 57} 58 59// Helper routine 60// FIXME : Take advantage of GlobalPrefix from AsmPrinter 61static const char *addUnderscore(const char *name) { 62 size_t namelen = strlen(name); 63 char *symName = (char*)malloc(namelen+2); 64 symName[0] = '_'; 65 strcpy(&symName[1], name); 66 return symName; 67} 68 69// Map LLVM LinkageType to LTO LinakgeType 70static LTOLinkageTypes 71getLTOLinkageType(GlobalValue *v) 72{ 73 LTOLinkageTypes lt; 74 if (v->hasExternalLinkage()) 75 lt = LTOExternalLinkage; 76 else if (v->hasLinkOnceLinkage()) 77 lt = LTOLinkOnceLinkage; 78 else if (v->hasWeakLinkage()) 79 lt = LTOWeakLinkage; 80 else 81 // Otherwise it is internal linkage for link time optimizer 82 lt = LTOInternalLinkage; 83 return lt; 84} 85 86// Find exeternal symbols referenced by VALUE. This is a recursive function. 87static void 88findExternalRefs(Value *value, std::set<std::string> &references, 89 Mangler &mangler) { 90 91 if (GlobalValue *gv = dyn_cast<GlobalValue>(value)) { 92 LTOLinkageTypes lt = getLTOLinkageType(gv); 93 if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5)) 94 references.insert(mangler.getValueName(gv)); 95 } 96 97 // GlobalValue, even with InternalLinkage type, may have operands with 98 // ExternalLinkage type. Do not ignore these operands. 99 if (Constant *c = dyn_cast<Constant>(value)) 100 // Handle ConstantExpr, ConstantStruct, ConstantArry etc.. 101 for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i) 102 findExternalRefs(c->getOperand(i), references, mangler); 103} 104 105/// If Module with InputFilename is available then remove it from allModules 106/// and call delete on it. 107void 108LTO::removeModule (const std::string &InputFilename) 109{ 110 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 111 if (pos == allModules.end()) 112 return; 113 114 Module *m = pos->second; 115 allModules.erase(pos); 116 delete m; 117} 118 119/// InputFilename is a LLVM bytecode file. If Module with InputFilename is 120/// available then return it. Otherwise parseInputFilename. 121Module * 122LTO::getModule(const std::string &InputFilename) 123{ 124 Module *m = NULL; 125 126 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 127 if (pos != allModules.end()) 128 m = allModules[InputFilename.c_str()]; 129 else { 130 m = ParseBytecodeFile(InputFilename); 131 allModules[InputFilename.c_str()] = m; 132 } 133 return m; 134} 135 136/// InputFilename is a LLVM bytecode file. Reade this bytecode file and 137/// set corresponding target triplet string. 138void 139LTO::getTargetTriple(const std::string &InputFilename, 140 std::string &targetTriple) 141{ 142 Module *m = getModule(InputFilename); 143 if (m) 144 targetTriple = m->getTargetTriple(); 145} 146 147/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. 148/// Collect global functions and symbol names in symbols vector. 149/// Collect external references in references vector. 150/// Return LTO_READ_SUCCESS if there is no error. 151enum LTOStatus 152LTO::readLLVMObjectFile(const std::string &InputFilename, 153 NameToSymbolMap &symbols, 154 std::set<std::string> &references) 155{ 156 Module *m = getModule(InputFilename); 157 if (!m) 158 return LTO_READ_FAILURE; 159 160 // Use mangler to add GlobalPrefix to names to match linker names. 161 // FIXME : Instead of hard coding "-" use GlobalPrefix. 162 Mangler mangler(*m, "_"); 163 164 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->isExternal() && lt != LTOInternalLinkage 171 && strncmp (f->getName().c_str(), "llvm.", 5)) { 172 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 173 mangler.getValueName(f)); 174 symbols[newSymbol->getMangledName()] = newSymbol; 175 allSymbols[newSymbol->getMangledName()] = newSymbol; 176 } 177 178 // Collect external symbols referenced by this function. 179 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 180 for (BasicBlock::iterator i = b->begin(), be = b->end(); 181 i != be; ++i) 182 for (unsigned count = 0, total = i->getNumOperands(); 183 count != total; ++count) 184 findExternalRefs(i->getOperand(count), references, mangler); 185 } 186 187 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 188 v != e; ++v) { 189 LTOLinkageTypes lt = getLTOLinkageType(v); 190 if (!v->isExternal() && lt != LTOInternalLinkage 191 && strncmp (v->getName().c_str(), "llvm.", 5)) { 192 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 193 mangler.getValueName(v)); 194 symbols[newSymbol->getMangledName()] = newSymbol; 195 allSymbols[newSymbol->getMangledName()] = newSymbol; 196 197 for (unsigned count = 0, total = v->getNumOperands(); 198 count != total; ++count) 199 findExternalRefs(v->getOperand(count), references, mangler); 200 201 } 202 } 203 204 return LTO_READ_SUCCESS; 205} 206 207/// Optimize module M using various IPO passes. Use exportList to 208/// internalize selected symbols. Target platform is selected 209/// based on information available to module M. No new target 210/// features are selected. 211static enum LTOStatus lto_optimize(Module *M, std::ostream &Out, 212 std::vector<const char *> &exportList) 213{ 214 // Instantiate the pass manager to organize the passes. 215 PassManager Passes; 216 217 // Collect Target info 218 std::string Err; 219 const TargetMachineRegistry::Entry* March = 220 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 221 222 if (March == 0) 223 return LTO_NO_TARGET; 224 225 // Create target 226 std::string Features; 227 std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features)); 228 if (!target.get()) 229 return LTO_NO_TARGET; 230 231 TargetMachine &Target = *target.get(); 232 233 // Start off with a verification pass. 234 Passes.add(createVerifierPass()); 235 236 // Add an appropriate TargetData instance for this module... 237 Passes.add(new TargetData(*Target.getTargetData())); 238 239 // Often if the programmer does not specify proper prototypes for the 240 // functions they are calling, they end up calling a vararg version of the 241 // function that does not get a body filled in (the real function has typed 242 // arguments). This pass merges the two functions. 243 Passes.add(createFunctionResolvingPass()); 244 245 // Internalize symbols if export list is nonemty 246 if (!exportList.empty()) 247 Passes.add(createInternalizePass(exportList)); 248 249 // Now that we internalized some globals, see if we can hack on them! 250 Passes.add(createGlobalOptimizerPass()); 251 252 // Linking modules together can lead to duplicated global constants, only 253 // keep one copy of each constant... 254 Passes.add(createConstantMergePass()); 255 256 // If the -s command line option was specified, strip the symbols out of the 257 // resulting program to make it smaller. -s is a GLD option that we are 258 // supporting. 259 Passes.add(createStripSymbolsPass()); 260 261 // Propagate constants at call sites into the functions they call. 262 Passes.add(createIPConstantPropagationPass()); 263 264 // Remove unused arguments from functions... 265 Passes.add(createDeadArgEliminationPass()); 266 267 Passes.add(createFunctionInliningPass()); // Inline small functions 268 269 Passes.add(createPruneEHPass()); // Remove dead EH info 270 271 Passes.add(createGlobalDCEPass()); // Remove dead functions 272 273 // If we didn't decide to inline a function, check to see if we can 274 // transform it to pass arguments by value instead of by reference. 275 Passes.add(createArgumentPromotionPass()); 276 277 // The IPO passes may leave cruft around. Clean up after them. 278 Passes.add(createInstructionCombiningPass()); 279 280 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 281 282 // Run a few AA driven optimizations here and now, to cleanup the code. 283 Passes.add(createGlobalsModRefPass()); // IP alias analysis 284 285 Passes.add(createLICMPass()); // Hoist loop invariants 286 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 287 Passes.add(createGCSEPass()); // Remove common subexprs 288 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 289 290 // Cleanup and simplify the code after the scalar optimizations. 291 Passes.add(createInstructionCombiningPass()); 292 293 // Delete basic blocks, which optimization passes may have killed... 294 Passes.add(createCFGSimplificationPass()); 295 296 // Now that we have optimized the program, discard unreachable functions... 297 Passes.add(createGlobalDCEPass()); 298 299 // Make sure everything is still good. 300 Passes.add(createVerifierPass()); 301 302 FunctionPassManager *CodeGenPasses = 303 new FunctionPassManager(new ExistingModuleProvider(M)); 304 305 CodeGenPasses->add(new TargetData(*Target.getTargetData())); 306 Target.addPassesToEmitFile(*CodeGenPasses, Out, TargetMachine::AssemblyFile, 307 true); 308 309 // Run our queue of passes all at once now, efficiently. 310 Passes.run(*M); 311 312 // Run the code generator, if present. 313 CodeGenPasses->doInitialization(); 314 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { 315 if (!I->isExternal()) 316 CodeGenPasses->run(*I); 317 } 318 CodeGenPasses->doFinalization(); 319 320 return LTO_OPT_SUCCESS; 321} 322 323///Link all modules together and optimize them using IPO. Generate 324/// native object file using OutputFilename 325/// Return appropriate LTOStatus. 326enum LTOStatus 327LTO::optimizeModules(const std::string &OutputFilename, 328 std::vector<const char *> &exportList, 329 std::string &targetTriple) 330{ 331 if (modules.empty()) 332 return LTO_NO_WORK; 333 334 std::ios::openmode io_mode = 335 std::ios::out | std::ios::trunc | std::ios::binary; 336 std::string *errMsg = NULL; 337 Module *bigOne = modules[0]; 338 Linker theLinker("LinkTimeOptimizer", bigOne, false); 339 for (unsigned i = 1, e = modules.size(); i != e; ++i) 340 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 341 return LTO_MODULE_MERGE_FAILURE; 342 343#if 0 344 // Enable this when -save-temps is used 345 std::ofstream Out("big.bc", io_mode); 346 WriteBytecodeToFile(bigOne, Out, true); 347#endif 348 349 // Strip leading underscore because it was added to match names 350 // seen by linker. 351 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 352 const char *name = exportList[i]; 353 NameToSymbolMap::iterator itr = allSymbols.find(name); 354 if (itr != allSymbols.end()) 355 exportList[i] = allSymbols[name]->getName(); 356 } 357 358 359 std::string ErrMsg; 360 sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg); 361 if (TempDir.isEmpty()) { 362 std::cerr << "lto: " << ErrMsg << "\n"; 363 return LTO_WRITE_FAILURE; 364 } 365 sys::Path tmpAsmFilePath(TempDir); 366 if (!tmpAsmFilePath.appendComponent("lto")) { 367 std::cerr << "lto: " << ErrMsg << "\n"; 368 TempDir.eraseFromDisk(true); 369 return LTO_WRITE_FAILURE; 370 } 371 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) { 372 std::cerr << "lto: " << ErrMsg << "\n"; 373 TempDir.eraseFromDisk(true); 374 return LTO_WRITE_FAILURE; 375 } 376 sys::RemoveFileOnSignal(tmpAsmFilePath); 377 378 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 379 if (!asmFile.is_open() || asmFile.bad()) { 380 if (tmpAsmFilePath.exists()) { 381 tmpAsmFilePath.eraseFromDisk(); 382 TempDir.eraseFromDisk(true); 383 } 384 return LTO_WRITE_FAILURE; 385 } 386 387 enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList); 388 asmFile.close(); 389 if (status != LTO_OPT_SUCCESS) { 390 tmpAsmFilePath.eraseFromDisk(); 391 TempDir.eraseFromDisk(true); 392 return status; 393 } 394 395 targetTriple = bigOne->getTargetTriple(); 396 397 // Run GCC to assemble and link the program into native code. 398 // 399 // Note: 400 // We can't just assemble and link the file with the system assembler 401 // and linker because we don't know where to put the _start symbol. 402 // GCC mysteriously knows how to do it. 403 const sys::Path gcc = sys::Program::FindProgramByName("gcc"); 404 if (gcc.isEmpty()) { 405 tmpAsmFilePath.eraseFromDisk(); 406 TempDir.eraseFromDisk(true); 407 return LTO_ASM_FAILURE; 408 } 409 410 std::vector<const char*> args; 411 args.push_back(gcc.c_str()); 412 args.push_back("-c"); 413 args.push_back("-x"); 414 args.push_back("assembler"); 415 args.push_back("-o"); 416 args.push_back(OutputFilename.c_str()); 417 args.push_back(tmpAsmFilePath.c_str()); 418 args.push_back(0); 419 420 if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1, &ErrMsg)) { 421 std::cerr << "lto: " << ErrMsg << "\n"; 422 return LTO_ASM_FAILURE; 423 } 424 425 tmpAsmFilePath.eraseFromDisk(); 426 TempDir.eraseFromDisk(true); 427 428 return LTO_OPT_SUCCESS; 429} 430