lto.cpp revision bdaf3dc8c33161babe436a19ee35748871657573
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 else if (Constant *c = dyn_cast<Constant>(value)) 97 // Handle ConstantExpr, ConstantStruct, ConstantArry etc.. 98 for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i) 99 findExternalRefs(c->getOperand(i), references, mangler); 100} 101 102/// InputFilename is a LLVM bytecode file. If Module with InputFilename is 103/// available then return it. Otherwise parseInputFilename. 104Module * 105LinkTimeOptimizer::getModule(const std::string &InputFilename) 106{ 107 Module *m = NULL; 108 109 NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); 110 if (pos != allModules.end()) 111 m = allModules[InputFilename.c_str()]; 112 else { 113 m = ParseBytecodeFile(InputFilename); 114 allModules[InputFilename.c_str()] = m; 115 } 116 return m; 117} 118 119/// InputFilename is a LLVM bytecode file. Reade this bytecode file and 120/// set corresponding target triplet string. 121void 122LinkTimeOptimizer::getTargetTriple(const std::string &InputFilename, 123 std::string &targetTriple) 124{ 125 Module *m = getModule(InputFilename); 126 if (m) 127 targetTriple = m->getTargetTriple(); 128} 129 130/// InputFilename is a LLVM bytecode file. Read it using bytecode reader. 131/// Collect global functions and symbol names in symbols vector. 132/// Collect external references in references vector. 133/// Return LTO_READ_SUCCESS if there is no error. 134enum LTOStatus 135LinkTimeOptimizer::readLLVMObjectFile(const std::string &InputFilename, 136 NameToSymbolMap &symbols, 137 std::set<std::string> &references) 138{ 139 Module *m = getModule(InputFilename); 140 if (!m) 141 return LTO_READ_FAILURE; 142 143 // Use mangler to add GlobalPrefix to names to match linker names. 144 // FIXME : Instead of hard coding "-" use GlobalPrefix. 145 Mangler mangler(*m, "_"); 146 147 modules.push_back(m); 148 149 for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { 150 151 LTOLinkageTypes lt = getLTOLinkageType(f); 152 153 if (!f->isExternal() && lt != LTOInternalLinkage 154 && strncmp (f->getName().c_str(), "llvm.", 5)) { 155 LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(), 156 mangler.getValueName(f)); 157 symbols[newSymbol->getMangledName()] = newSymbol; 158 allSymbols[newSymbol->getMangledName()] = newSymbol; 159 } 160 161 // Collect external symbols referenced by this function. 162 for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) 163 for (BasicBlock::iterator i = b->begin(), be = b->end(); 164 i != be; ++i) 165 for (unsigned count = 0, total = i->getNumOperands(); 166 count != total; ++count) 167 findExternalRefs(i->getOperand(count), references, mangler); 168 } 169 170 for (Module::global_iterator v = m->global_begin(), e = m->global_end(); 171 v != e; ++v) { 172 LTOLinkageTypes lt = getLTOLinkageType(v); 173 if (!v->isExternal() && lt != LTOInternalLinkage 174 && strncmp (v->getName().c_str(), "llvm.", 5)) { 175 LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(), 176 mangler.getValueName(v)); 177 symbols[newSymbol->getMangledName()] = newSymbol; 178 allSymbols[newSymbol->getMangledName()] = newSymbol; 179 180 for (unsigned count = 0, total = v->getNumOperands(); 181 count != total; ++count) 182 findExternalRefs(v->getOperand(count), references, mangler); 183 184 } 185 } 186 187 return LTO_READ_SUCCESS; 188} 189 190/// Optimize module M using various IPO passes. Use exportList to 191/// internalize selected symbols. Target platform is selected 192/// based on information available to module M. No new target 193/// features are selected. 194static enum LTOStatus lto_optimize(Module *M, std::ostream &Out, 195 std::vector<const char *> &exportList) 196{ 197 // Instantiate the pass manager to organize the passes. 198 PassManager Passes; 199 200 // Collect Target info 201 std::string Err; 202 const TargetMachineRegistry::Entry* March = 203 TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); 204 205 if (March == 0) 206 return LTO_NO_TARGET; 207 208 // Create target 209 std::string Features; 210 std::auto_ptr<TargetMachine> target(March->CtorFn(*M, Features)); 211 if (!target.get()) 212 return LTO_NO_TARGET; 213 214 TargetMachine &Target = *target.get(); 215 216 // Start off with a verification pass. 217 Passes.add(createVerifierPass()); 218 219 // Add an appropriate TargetData instance for this module... 220 Passes.add(new TargetData(*Target.getTargetData())); 221 222 // Often if the programmer does not specify proper prototypes for the 223 // functions they are calling, they end up calling a vararg version of the 224 // function that does not get a body filled in (the real function has typed 225 // arguments). This pass merges the two functions. 226 Passes.add(createFunctionResolvingPass()); 227 228 // Internalize symbols if export list is nonemty 229 if (!exportList.empty()) 230 Passes.add(createInternalizePass(exportList)); 231 232 // Now that we internalized some globals, see if we can hack on them! 233 Passes.add(createGlobalOptimizerPass()); 234 235 // Linking modules together can lead to duplicated global constants, only 236 // keep one copy of each constant... 237 Passes.add(createConstantMergePass()); 238 239 // If the -s command line option was specified, strip the symbols out of the 240 // resulting program to make it smaller. -s is a GLD option that we are 241 // supporting. 242 Passes.add(createStripSymbolsPass()); 243 244 // Propagate constants at call sites into the functions they call. 245 Passes.add(createIPConstantPropagationPass()); 246 247 // Remove unused arguments from functions... 248 Passes.add(createDeadArgEliminationPass()); 249 250 Passes.add(createFunctionInliningPass()); // Inline small functions 251 252 Passes.add(createPruneEHPass()); // Remove dead EH info 253 254 Passes.add(createGlobalDCEPass()); // Remove dead functions 255 256 // If we didn't decide to inline a function, check to see if we can 257 // transform it to pass arguments by value instead of by reference. 258 Passes.add(createArgumentPromotionPass()); 259 260 // The IPO passes may leave cruft around. Clean up after them. 261 Passes.add(createInstructionCombiningPass()); 262 263 Passes.add(createScalarReplAggregatesPass()); // Break up allocas 264 265 // Run a few AA driven optimizations here and now, to cleanup the code. 266 Passes.add(createGlobalsModRefPass()); // IP alias analysis 267 268 Passes.add(createLICMPass()); // Hoist loop invariants 269 Passes.add(createLoadValueNumberingPass()); // GVN for load instrs 270 Passes.add(createGCSEPass()); // Remove common subexprs 271 Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores 272 273 // Cleanup and simplify the code after the scalar optimizations. 274 Passes.add(createInstructionCombiningPass()); 275 276 // Delete basic blocks, which optimization passes may have killed... 277 Passes.add(createCFGSimplificationPass()); 278 279 // Now that we have optimized the program, discard unreachable functions... 280 Passes.add(createGlobalDCEPass()); 281 282 // Make sure everything is still good. 283 Passes.add(createVerifierPass()); 284 285 Target.addPassesToEmitWholeFile(Passes, Out, TargetMachine::AssemblyFile, true); 286 287 // Run our queue of passes all at once now, efficiently. 288 Passes.run(*M); 289 290 return LTO_OPT_SUCCESS; 291} 292 293///Link all modules together and optimize them using IPO. Generate 294/// native object file using OutputFilename 295/// Return appropriate LTOStatus. 296enum LTOStatus 297LinkTimeOptimizer::optimizeModules(const std::string &OutputFilename, 298 std::vector<const char *> &exportList, 299 std::string &targetTriple) 300{ 301 if (modules.empty()) 302 return LTO_NO_WORK; 303 304 std::ios::openmode io_mode = 305 std::ios::out | std::ios::trunc | std::ios::binary; 306 std::string *errMsg = NULL; 307 Module *bigOne = modules[0]; 308 Linker theLinker("LinkTimeOptimizer", bigOne, false); 309 for (unsigned i = 1, e = modules.size(); i != e; ++i) 310 if (theLinker.LinkModules(bigOne, modules[i], errMsg)) 311 return LTO_MODULE_MERGE_FAILURE; 312 313#if 0 314 // Enable this when -save-temps is used 315 std::ofstream Out("big.bc", io_mode); 316 WriteBytecodeToFile(bigOne, Out, true); 317#endif 318 319 // Strip leading underscore because it was added to match names 320 // seen by linker. 321 for (unsigned i = 0, e = exportList.size(); i != e; ++i) { 322 const char *name = exportList[i]; 323 NameToSymbolMap::iterator itr = allSymbols.find(name); 324 if (itr != allSymbols.end()) 325 exportList[i] = allSymbols[name]->getName(); 326 } 327 328 sys::Path tmpAsmFilePath("/tmp/"); 329 std::string ErrMsg; 330 if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) { 331 std::cerr << "lto: " << ErrMsg << "\n"; 332 return LTO_WRITE_FAILURE; 333 } 334 sys::RemoveFileOnSignal(tmpAsmFilePath); 335 336 std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); 337 if (!asmFile.is_open() || asmFile.bad()) { 338 if (tmpAsmFilePath.exists()) 339 tmpAsmFilePath.eraseFromDisk(); 340 return LTO_WRITE_FAILURE; 341 } 342 343 enum LTOStatus status = lto_optimize(bigOne, asmFile, exportList); 344 asmFile.close(); 345 if (status != LTO_OPT_SUCCESS) { 346 tmpAsmFilePath.eraseFromDisk(); 347 return status; 348 } 349 350 targetTriple = bigOne->getTargetTriple(); 351 352 // Run GCC to assemble and link the program into native code. 353 // 354 // Note: 355 // We can't just assemble and link the file with the system assembler 356 // and linker because we don't know where to put the _start symbol. 357 // GCC mysteriously knows how to do it. 358 const sys::Path gcc = FindExecutable("gcc", "/"); 359 if (gcc.isEmpty()) { 360 tmpAsmFilePath.eraseFromDisk(); 361 return LTO_ASM_FAILURE; 362 } 363 364 std::vector<const char*> args; 365 args.push_back(gcc.c_str()); 366 args.push_back("-c"); 367 args.push_back("-x"); 368 args.push_back("assembler"); 369 args.push_back("-o"); 370 args.push_back(OutputFilename.c_str()); 371 args.push_back(tmpAsmFilePath.c_str()); 372 args.push_back(0); 373 374 sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1); 375 376 tmpAsmFilePath.eraseFromDisk(); 377 378 return LTO_OPT_SUCCESS; 379} 380