lto.cpp revision 544ea34a9f7aeef5fa3cbfdaae5933f93f4f68ec
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::LinkTimeOptimizer *l = new llvm::LinkTimeOptimizer(); 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/// InputFilename is a LLVM bytecode file. If Module with InputFilename is 106/// available then return it. Otherwise parseInputFilename. 107Module * 108LinkTimeOptimizer::getModule(const std::string &InputFilename) 109{ 110 Module *m = NULL; 111 112 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 113 if (pos != allModules.end()) 114 m = allModules[InputFilename.c_str()]; 115 else { 116 m = ParseBytecodeFile(InputFilename); 117 allModules[InputFilename.c_str()] = m; 118 } 119 return m; 120} 121 122/// InputFilename is a LLVM bytecode file. Reade this bytecode file and 123/// set corresponding target triplet string. 124void 125LinkTimeOptimizer::getTargetTriple(const std::string &InputFilename, 126 std::string &targetTriple) 127{ 128 Module *m = getModule(InputFilename); 129 if (m) 130 targetTriple = m->getTargetTriple(); 131} 132 133/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. 134/// Collect global functions and symbol names in symbols vector. 135/// Collect external references in references vector. 136/// Return LTO_READ_SUCCESS if there is no error. 137enum LTOStatus 138LinkTimeOptimizer::readLLVMObjectFile(const std::string &InputFilename, 139 NameToSymbolMap &symbols, 140 std::set<std::string> &references) 141{ 142 Module *m = getModule(InputFilename); 143 if (!m) 144 return LTO_READ_FAILURE; 145 146 // Use mangler to add GlobalPrefix to names to match linker names. 147 // FIXME : Instead of hard coding "-" use GlobalPrefix. 148 Mangler mangler(*m, "_"); 149 150 modules.push_back(m); 151 152 for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { 153 154 LTOLinkageTypes lt = getLTOLinkageType(f); 155 156 if (!f->isExternal() && lt != LTOInternalLinkage 157 && strncmp (f->getName().c_str(), "llvm.", 5)) { 158 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 159 mangler.getValueName(f)); 160 symbols[newSymbol->getMangledName()] = newSymbol; 161 allSymbols[newSymbol->getMangledName()] = newSymbol; 162 } 163 164 // Collect external symbols referenced by this function. 165 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 166 for (BasicBlock::iterator i = b->begin(), be = b->end(); 167 i != be; ++i) 168 for (unsigned count = 0, total = i->getNumOperands(); 169 count != total; ++count) 170 findExternalRefs(i->getOperand(count), references, mangler); 171 } 172 173 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 174 v != e; ++v) { 175 LTOLinkageTypes lt = getLTOLinkageType(v); 176 if (!v->isExternal() && lt != LTOInternalLinkage 177 && strncmp (v->getName().c_str(), "llvm.", 5)) { 178 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 179 mangler.getValueName(v)); 180 symbols[newSymbol->getMangledName()] = newSymbol; 181 allSymbols[newSymbol->getMangledName()] = newSymbol; 182 183 for (unsigned count = 0, total = v->getNumOperands(); 184 count != total; ++count) 185 findExternalRefs(v->getOperand(count), references, mangler); 186 187 } 188 } 189 190 return LTO_READ_SUCCESS; 191} 192 193/// Optimize module M using various IPO passes. Use exportList to 194/// internalize selected symbols. Target platform is selected 195/// based on information available to module M. No new target 196/// features are selected. 197static enum LTOStatus lto_optimize(Module *M, std::ostream &Out, 198 std::vector<const char *> &exportList) 199{ 200 // Instantiate the pass manager to organize the passes. 201 PassManager Passes; 202 203 // Collect Target info 204 std::string Err; 205 const TargetMachineRegistry::Entry* March = 206 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 207 208 if (March == 0) 209 return LTO_NO_TARGET; 210 211 // Create target 212 std::string Features; 213 std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features)); 214 if (!target.get()) 215 return LTO_NO_TARGET; 216 217 TargetMachine &Target = *target.get(); 218 219 // Start off with a verification pass. 220 Passes.add(createVerifierPass()); 221 222 // Add an appropriate TargetData instance for this module... 223 Passes.add(new TargetData(*Target.getTargetData())); 224 225 // Often if the programmer does not specify proper prototypes for the 226 // functions they are calling, they end up calling a vararg version of the 227 // function that does not get a body filled in (the real function has typed 228 // arguments). This pass merges the two functions. 229 Passes.add(createFunctionResolvingPass()); 230 231 // Internalize symbols if export list is nonemty 232 if (!exportList.empty()) 233 Passes.add(createInternalizePass(exportList)); 234 235 // Now that we internalized some globals, see if we can hack on them! 236 Passes.add(createGlobalOptimizerPass()); 237 238 // Linking modules together can lead to duplicated global constants, only 239 // keep one copy of each constant... 240 Passes.add(createConstantMergePass()); 241 242 // If the -s command line option was specified, strip the symbols out of the 243 // resulting program to make it smaller. -s is a GLD option that we are 244 // supporting. 245 Passes.add(createStripSymbolsPass()); 246 247 // Propagate constants at call sites into the functions they call. 248 Passes.add(createIPConstantPropagationPass()); 249 250 // Remove unused arguments from functions... 251 Passes.add(createDeadArgEliminationPass()); 252 253 Passes.add(createFunctionInliningPass()); // Inline small functions 254 255 Passes.add(createPruneEHPass()); // Remove dead EH info 256 257 Passes.add(createGlobalDCEPass()); // Remove dead functions 258 259 // If we didn't decide to inline a function, check to see if we can 260 // transform it to pass arguments by value instead of by reference. 261 Passes.add(createArgumentPromotionPass()); 262 263 // The IPO passes may leave cruft around. Clean up after them. 264 Passes.add(createInstructionCombiningPass()); 265 266 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 267 268 // Run a few AA driven optimizations here and now, to cleanup the code. 269 Passes.add(createGlobalsModRefPass()); // IP alias analysis 270 271 Passes.add(createLICMPass()); // Hoist loop invariants 272 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 273 Passes.add(createGCSEPass()); // Remove common subexprs 274 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 275 276 // Cleanup and simplify the code after the scalar optimizations. 277 Passes.add(createInstructionCombiningPass()); 278 279 // Delete basic blocks, which optimization passes may have killed... 280 Passes.add(createCFGSimplificationPass()); 281 282 // Now that we have optimized the program, discard unreachable functions... 283 Passes.add(createGlobalDCEPass()); 284 285 // Make sure everything is still good. 286 Passes.add(createVerifierPass()); 287 288 FunctionPassManager *CodeGenPasses = 289 new FunctionPassManager(new ExistingModuleProvider(M)); 290 291 CodeGenPasses->add(new TargetData(*Target.getTargetData())); 292 Target.addPassesToEmitFile(*CodeGenPasses, Out, TargetMachine::AssemblyFile, 293 true); 294 295 // Run our queue of passes all at once now, efficiently. 296 Passes.run(*M); 297 298 // Run the code generator, if present. 299 CodeGenPasses->doInitialization(); 300 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { 301 if (!I->isExternal()) 302 CodeGenPasses->run(*I); 303 } 304 CodeGenPasses->doFinalization(); 305 306 return LTO_OPT_SUCCESS; 307} 308 309///Link all modules together and optimize them using IPO. Generate 310/// native object file using OutputFilename 311/// Return appropriate LTOStatus. 312enum LTOStatus 313LinkTimeOptimizer::optimizeModules(const std::string &OutputFilename, 314 std::vector<const char *> &exportList, 315 std::string &targetTriple) 316{ 317 if (modules.empty()) 318 return LTO_NO_WORK; 319 320 std::ios::openmode io_mode = 321 std::ios::out | std::ios::trunc | std::ios::binary; 322 std::string *errMsg = NULL; 323 Module *bigOne = modules[0]; 324 Linker theLinker("LinkTimeOptimizer", bigOne, false); 325 for (unsigned i = 1, e = modules.size(); i != e; ++i) 326 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 327 return LTO_MODULE_MERGE_FAILURE; 328 329#if 0 330 // Enable this when -save-temps is used 331 std::ofstream Out("big.bc", io_mode); 332 WriteBytecodeToFile(bigOne, Out, true); 333#endif 334 335 // Strip leading underscore because it was added to match names 336 // seen by linker. 337 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 338 const char *name = exportList[i]; 339 NameToSymbolMap::iterator itr = allSymbols.find(name); 340 if (itr != allSymbols.end()) 341 exportList[i] = allSymbols[name]->getName(); 342 } 343 344 sys::Path tmpAsmFilePath("/tmp/"); 345 std::string ErrMsg; 346 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) { 347 std::cerr << "lto: " << ErrMsg << "\n"; 348 return LTO_WRITE_FAILURE; 349 } 350 sys::RemoveFileOnSignal(tmpAsmFilePath); 351 352 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 353 if (!asmFile.is_open() || asmFile.bad()) { 354 if (tmpAsmFilePath.exists()) 355 tmpAsmFilePath.eraseFromDisk(); 356 return LTO_WRITE_FAILURE; 357 } 358 359 enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList); 360 asmFile.close(); 361 if (status != LTO_OPT_SUCCESS) { 362 tmpAsmFilePath.eraseFromDisk(); 363 return status; 364 } 365 366 targetTriple = bigOne->getTargetTriple(); 367 368 // Run GCC to assemble and link the program into native code. 369 // 370 // Note: 371 // We can't just assemble and link the file with the system assembler 372 // and linker because we don't know where to put the _start symbol. 373 // GCC mysteriously knows how to do it. 374 const sys::Path gcc = FindExecutable("gcc", "/"); 375 if (gcc.isEmpty()) { 376 tmpAsmFilePath.eraseFromDisk(); 377 return LTO_ASM_FAILURE; 378 } 379 380 std::vector<const char*> args; 381 args.push_back(gcc.c_str()); 382 args.push_back("-c"); 383 args.push_back("-x"); 384 args.push_back("assembler"); 385 args.push_back("-o"); 386 args.push_back(OutputFilename.c_str()); 387 args.push_back(tmpAsmFilePath.c_str()); 388 args.push_back(0); 389 390 sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1); 391 392 tmpAsmFilePath.eraseFromDisk(); 393 394 return LTO_OPT_SUCCESS; 395} 396