tools/lto/lto.cpp

   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/ModuleProvider.h"
  21 #include "llvm/Bitcode/ReaderWriter.h"
  22 #include "llvm/Support/CommandLine.h"
  23 #include "llvm/Support/FileUtilities.h"
  24 #include "llvm/Support/SystemUtils.h"
  25 #include "llvm/Support/Mangler.h"
  26 #include "llvm/Support/MemoryBuffer.h"
  27 #include "llvm/System/Program.h"
  28 #include "llvm/System/Signals.h"
  29 #include "llvm/Analysis/Passes.h"
  30 #include "llvm/Analysis/LoopPass.h"
  31 #include "llvm/Analysis/Verifier.h"
  32 #include "llvm/CodeGen/FileWriters.h"
  33 #include "llvm/Target/SubtargetFeature.h"
  34 #include "llvm/Target/TargetData.h"
  35 #include "llvm/Target/TargetMachine.h"
  36 #include "llvm/Target/TargetMachineRegistry.h"
  37 #include "llvm/Target/TargetAsmInfo.h"
  38 #include "llvm/Transforms/IPO.h"
  39 #include "llvm/Transforms/Scalar.h"
  40 #include "llvm/Analysis/LoadValueNumbering.h"
  41 #include "llvm/Support/MathExtras.h"
  42 #include "llvm/LinkTimeOptimizer.h"
  43 #include <fstream>
  44 #include <ostream>
  45 using namespace llvm;
  46
  47 extern "C"
  48 llvm::LinkTimeOptimizer *createLLVMOptimizer()
  49 {
  50   llvm::LTO *l = new llvm::LTO();
  51   return l;
  52 }
  53
  54 /// If symbol is not used then make it internal and let optimizer takes
  55 /// care of it.
  56 void LLVMSymbol::mayBeNotUsed() {
  57   gv->setLinkage(GlobalValue::InternalLinkage);
  58 }
  59
  60 // Map LLVM LinkageType to LTO LinakgeType
  61 static LTOLinkageTypes
  62 getLTOLinkageType(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.
  78 static void
  79 findExternalRefs(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.
  98 void
  99 LTO::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.
 112 Module *
 113 LTO::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     if (MemoryBuffer *Buffer
 122         = MemoryBuffer::getFile(&InputFilename[0], InputFilename.size())) {
 123       m = ParseBitcodeFile(Buffer);
 124       delete Buffer;
 125     }
 126     allModules[InputFilename.c_str()] = m;
 127   }
 128   return m;
 129 }
 130
 131 /// InputFilename is a LLVM bytecode file. Reade this bytecode file and
 132 /// set corresponding target triplet string.
 133 void
 134 LTO::getTargetTriple(const std::string &InputFilename,
 135                      std::string &targetTriple)
 136 {
 137   Module *m = getModule(InputFilename);
 138   if (m)
 139     targetTriple = m->getTargetTriple();
 140 }
 141
 142 /// InputFilename is a LLVM bytecode file. Read it using bytecode reader.
 143 /// Collect global functions and symbol names in symbols vector.
 144 /// Collect external references in references vector.
 145 /// Return LTO_READ_SUCCESS if there is no error.
 146 enum LTOStatus
 147 LTO::readLLVMObjectFile(const std::string &InputFilename,
 148                         NameToSymbolMap &symbols,
 149                         std::set<std::string> &references)
 150 {
 151   Module *m = getModule(InputFilename);
 152   if (!m)
 153     return LTO_READ_FAILURE;
 154
 155   // Collect Target info
 156   getTarget(m);
 157
 158   if (!Target)
 159     return LTO_READ_FAILURE;
 160
 161   // Use mangler to add GlobalPrefix to names to match linker names.
 162   // FIXME : Instead of hard coding "-" use GlobalPrefix.
 163   Mangler mangler(*m, Target->getTargetAsmInfo()->getGlobalPrefix());
 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->isDeclaration() && lt != LTOInternalLinkage
 171         && strncmp (f->getName().c_str(), "llvm.", 5)) {
 172       int alignment = ( 16 > f->getAlignment() ? 16 : f->getAlignment());
 173       LLVMSymbol *newSymbol = new LLVMSymbol(lt, f, f->getName(),
 174                                              mangler.getValueName(f),
 175                                              Log2_32(alignment));
 176       symbols[newSymbol->getMangledName()] = newSymbol;
 177       allSymbols[newSymbol->getMangledName()] = newSymbol;
 178     }
 179
 180     // Collect external symbols referenced by this function.
 181     for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b)
 182       for (BasicBlock::iterator i = b->begin(), be = b->end();
 183            i != be; ++i)
 184         for (unsigned count = 0, total = i->getNumOperands();
 185              count != total; ++count)
 186           findExternalRefs(i->getOperand(count), references, mangler);
 187   }
 188
 189   for (Module::global_iterator v = m->global_begin(), e = m->global_end();
 190        v !=  e; ++v) {
 191     LTOLinkageTypes lt = getLTOLinkageType(v);
 192     if (!v->isDeclaration() && lt != LTOInternalLinkage
 193         && strncmp (v->getName().c_str(), "llvm.", 5)) {
 194       const TargetData *TD = Target->getTargetData();
 195       LLVMSymbol *newSymbol = new LLVMSymbol(lt, v, v->getName(),
 196                                              mangler.getValueName(v),
 197                                              TD->getPreferredAlignmentLog(v));
 198       symbols[newSymbol->getMangledName()] = newSymbol;
 199       allSymbols[newSymbol->getMangledName()] = newSymbol;
 200
 201       for (unsigned count = 0, total = v->getNumOperands();
 202            count != total; ++count)
 203         findExternalRefs(v->getOperand(count), references, mangler);
 204
 205     }
 206   }
 207
 208   return LTO_READ_SUCCESS;
 209 }
 210
 211 /// Get TargetMachine.
 212 /// Use module M to find appropriate Target.
 213 void
 214 LTO::getTarget (Module *M) {
 215
 216   if (Target)
 217     return;
 218
 219   std::string Err;
 220   const TargetMachineRegistry::Entry* March =
 221     TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err);
 222
 223   if (March == 0)
 224     return;
 225
 226   // Create target
 227   std::string Features;
 228   Target = March->CtorFn(*M, Features);
 229 }
 230
 231 /// Optimize module M using various IPO passes. Use exportList to
 232 /// internalize selected symbols. Target platform is selected
 233 /// based on information available to module M. No new target
 234 /// features are selected.
 235 enum LTOStatus
 236 LTO::optimize(Module *M, std::ostream &Out,
 237               std::vector<const char *> &exportList)
 238 {
 239   // Instantiate the pass manager to organize the passes.
 240   PassManager Passes;
 241
 242   // Collect Target info
 243   getTarget(M);
 244
 245   if (!Target)
 246     return LTO_NO_TARGET;
 247
 248   // Start off with a verification pass.
 249   Passes.add(createVerifierPass());
 250
 251   // Add an appropriate TargetData instance for this module...
 252   Passes.add(new TargetData(*Target->getTargetData()));
 253
 254   // Internalize symbols if export list is nonemty
 255   if (!exportList.empty())
 256     Passes.add(createInternalizePass(exportList));
 257
 258   // Now that we internalized some globals, see if we can hack on them!
 259   Passes.add(createGlobalOptimizerPass());
 260
 261   // Linking modules together can lead to duplicated global constants, only
 262   // keep one copy of each constant...
 263   Passes.add(createConstantMergePass());
 264
 265   // If the -s command line option was specified, strip the symbols out of the
 266   // resulting program to make it smaller.  -s is a GLD option that we are
 267   // supporting.
 268   Passes.add(createStripSymbolsPass());
 269
 270   // Propagate constants at call sites into the functions they call.
 271   Passes.add(createIPConstantPropagationPass());
 272
 273   // Remove unused arguments from functions...
 274   Passes.add(createDeadArgEliminationPass());
 275
 276   Passes.add(createFunctionInliningPass()); // Inline small functions
 277
 278   Passes.add(createPruneEHPass());            // Remove dead EH info
 279
 280   Passes.add(createGlobalDCEPass());          // Remove dead functions
 281
 282   // If we didn't decide to inline a function, check to see if we can
 283   // transform it to pass arguments by value instead of by reference.
 284   Passes.add(createArgumentPromotionPass());
 285
 286   // The IPO passes may leave cruft around.  Clean up after them.
 287   Passes.add(createInstructionCombiningPass());
 288
 289   Passes.add(createScalarReplAggregatesPass()); // Break up allocas
 290
 291   // Run a few AA driven optimizations here and now, to cleanup the code.
 292   Passes.add(createGlobalsModRefPass());      // IP alias analysis
 293
 294   Passes.add(createLICMPass());               // Hoist loop invariants
 295   Passes.add(createLoadValueNumberingPass()); // GVN for load instrs
 296   Passes.add(createGCSEPass());               // Remove common subexprs
 297   Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
 298
 299   // Cleanup and simplify the code after the scalar optimizations.
 300   Passes.add(createInstructionCombiningPass());
 301
 302   // Delete basic blocks, which optimization passes may have killed...
 303   Passes.add(createCFGSimplificationPass());
 304
 305   // Now that we have optimized the program, discard unreachable functions...
 306   Passes.add(createGlobalDCEPass());
 307
 308   // Make sure everything is still good.
 309   Passes.add(createVerifierPass());
 310
 311   FunctionPassManager *CodeGenPasses =
 312     new FunctionPassManager(new ExistingModuleProvider(M));
 313
 314   CodeGenPasses->add(new TargetData(*Target->getTargetData()));
 315
 316   MachineCodeEmitter *MCE = 0;
 317
 318   switch (Target->addPassesToEmitFile(*CodeGenPasses, Out,
 319                                       TargetMachine::AssemblyFile, true)) {
 320   default:
 321   case FileModel::Error:
 322     return LTO_WRITE_FAILURE;
 323   case FileModel::AsmFile:
 324     break;
 325   case FileModel::MachOFile:
 326     MCE = AddMachOWriter(*CodeGenPasses, Out, *Target);
 327     break;
 328   case FileModel::ElfFile:
 329     MCE = AddELFWriter(*CodeGenPasses, Out, *Target);
 330     break;
 331   }
 332
 333   if (Target->addPassesToEmitFileFinish(*CodeGenPasses, MCE, true))
 334     return LTO_WRITE_FAILURE;
 335
 336   // Run our queue of passes all at once now, efficiently.
 337   Passes.run(*M);
 338
 339   // Run the code generator, if present.
 340   CodeGenPasses->doInitialization();
 341   for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) {
 342     if (!I->isDeclaration())
 343       CodeGenPasses->run(*I);
 344   }
 345   CodeGenPasses->doFinalization();
 346
 347   return LTO_OPT_SUCCESS;
 348 }
 349
 350 ///Link all modules together and optimize them using IPO. Generate
 351 /// native object file using OutputFilename
 352 /// Return appropriate LTOStatus.
 353 enum LTOStatus
 354 LTO::optimizeModules(const std::string &OutputFilename,
 355                      std::vector<const char *> &exportList,
 356                      std::string &targetTriple,
 357                      bool saveTemps,
 358                      const char *FinalOutputFilename)
 359 {
 360   if (modules.empty())
 361     return LTO_NO_WORK;
 362
 363   std::ios::openmode io_mode =
 364     std::ios::out | std::ios::trunc | std::ios::binary;
 365   std::string *errMsg = NULL;
 366   Module *bigOne = modules[0];
 367   Linker theLinker("LinkTimeOptimizer", bigOne, false);
 368   for (unsigned i = 1, e = modules.size(); i != e; ++i)
 369     if (theLinker.LinkModules(bigOne, modules[i], errMsg))
 370       return LTO_MODULE_MERGE_FAILURE;
 371   //  all modules have been handed off to the linker.
 372   modules.clear();
 373
 374   sys::Path FinalOutputPath(FinalOutputFilename);
 375   FinalOutputPath.eraseSuffix();
 376
 377   if (saveTemps) {
 378     std::string tempFileName(FinalOutputPath.c_str());
 379     tempFileName += "0.bc";
 380     std::ofstream Out(tempFileName.c_str(), io_mode);
 381     WriteBitcodeToFile(bigOne, Out);
 382   }
 383
 384   // Strip leading underscore because it was added to match names
 385   // seen by linker.
 386   for (unsigned i = 0, e = exportList.size(); i != e; ++i) {
 387     const char *name = exportList[i];
 388     NameToSymbolMap::iterator itr = allSymbols.find(name);
 389     if (itr != allSymbols.end())
 390       exportList[i] = allSymbols[name]->getName();
 391   }
 392
 393
 394   std::string ErrMsg;
 395   sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg);
 396   if (TempDir.isEmpty()) {
 397     cerr << "lto: " << ErrMsg << "\n";
 398     return LTO_WRITE_FAILURE;
 399   }
 400   sys::Path tmpAsmFilePath(TempDir);
 401   if (!tmpAsmFilePath.appendComponent("lto")) {
 402     cerr << "lto: " << ErrMsg << "\n";
 403     TempDir.eraseFromDisk(true);
 404     return LTO_WRITE_FAILURE;
 405   }
 406   if (tmpAsmFilePath.createTemporaryFileOnDisk(&ErrMsg)) {
 407     cerr << "lto: " << ErrMsg << "\n";
 408     TempDir.eraseFromDisk(true);
 409     return LTO_WRITE_FAILURE;
 410   }
 411   sys::RemoveFileOnSignal(tmpAsmFilePath);
 412
 413   std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode);
 414   if (!asmFile.is_open() || asmFile.bad()) {
 415     if (tmpAsmFilePath.exists()) {
 416       tmpAsmFilePath.eraseFromDisk();
 417       TempDir.eraseFromDisk(true);
 418     }
 419     return LTO_WRITE_FAILURE;
 420   }
 421
 422   enum LTOStatus status = optimize(bigOne, asmFile, exportList);
 423   asmFile.close();
 424   if (status != LTO_OPT_SUCCESS) {
 425     tmpAsmFilePath.eraseFromDisk();
 426     TempDir.eraseFromDisk(true);
 427     return status;
 428   }
 429
 430   if (saveTemps) {
 431     std::string tempFileName(FinalOutputPath.c_str());
 432     tempFileName += "1.bc";
 433     std::ofstream Out(tempFileName.c_str(), io_mode);
 434     WriteBitcodeToFile(bigOne, Out);
 435   }
 436
 437   targetTriple = bigOne->getTargetTriple();
 438
 439   // Run GCC to assemble and link the program into native code.
 440   //
 441   // Note:
 442   //  We can't just assemble and link the file with the system assembler
 443   //  and linker because we don't know where to put the _start symbol.
 444   //  GCC mysteriously knows how to do it.
 445   const sys::Path gcc = sys::Program::FindProgramByName("gcc");
 446   if (gcc.isEmpty()) {
 447     tmpAsmFilePath.eraseFromDisk();
 448     TempDir.eraseFromDisk(true);
 449     return LTO_ASM_FAILURE;
 450   }
 451
 452   std::vector<const char*> args;
 453   args.push_back(gcc.c_str());
 454   args.push_back("-c");
 455   args.push_back("-x");
 456   args.push_back("assembler");
 457   args.push_back("-o");
 458   args.push_back(OutputFilename.c_str());
 459   args.push_back(tmpAsmFilePath.c_str());
 460   args.push_back(0);
 461
 462   if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 1, 0, &ErrMsg)) {
 463     cerr << "lto: " << ErrMsg << "\n";
 464     return LTO_ASM_FAILURE;
 465   }
 466
 467   tmpAsmFilePath.eraseFromDisk();
 468   TempDir.eraseFromDisk(true);
 469
 470   return LTO_OPT_SUCCESS;
 471 }
 472
 473 void LTO::printVersion() {
 474     cl::PrintVersionMessage();
 475 }
 476
 477 /// Unused pure-virtual destructor. Must remain empty.
 478 LinkTimeOptimizer::~LinkTimeOptimizer() {}
 479
 480 /// Destruct LTO. Delete all modules, symbols and target.
 481 LTO::~LTO() {
 482
 483   for (std::vector<Module *>::iterator itr = modules.begin(), e = modules.end();
 484        itr != e; ++itr)
 485     delete *itr;
 486
 487   modules.clear();
 488
 489   for (NameToSymbolMap::iterator itr = allSymbols.begin(), e = allSymbols.end();
 490        itr != e; ++itr)
 491     delete itr->second;
 492
 493   allSymbols.clear();
 494
 495   delete Target;
 496 }