tools/lto/LTOCodeGenerator.cpp

   1 //===-LTOCodeGenerator.cpp - LLVM Link Time Optimizer ---------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // 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 "LTOModule.h"
  16 #include "LTOCodeGenerator.h"
  17
  18
  19 #include "llvm/Module.h"
  20 #include "llvm/PassManager.h"
  21 #include "llvm/Linker.h"
  22 #include "llvm/Constants.h"
  23 #include "llvm/DerivedTypes.h"
  24 #include "llvm/ModuleProvider.h"
  25 #include "llvm/Bitcode/ReaderWriter.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/SystemUtils.h"
  28 #include "llvm/Support/Mangler.h"
  29 #include "llvm/Support/MemoryBuffer.h"
  30 #include "llvm/Support/raw_ostream.h"
  31 #include "llvm/System/Signals.h"
  32 #include "llvm/Analysis/Passes.h"
  33 #include "llvm/Analysis/LoopPass.h"
  34 #include "llvm/Analysis/Verifier.h"
  35 #include "llvm/CodeGen/FileWriters.h"
  36 #include "llvm/Target/SubtargetFeature.h"
  37 #include "llvm/Target/TargetOptions.h"
  38 #include "llvm/Target/TargetData.h"
  39 #include "llvm/Target/TargetMachine.h"
  40 #include "llvm/Target/TargetMachineRegistry.h"
  41 #include "llvm/Target/TargetAsmInfo.h"
  42 #include "llvm/Transforms/IPO.h"
  43 #include "llvm/Transforms/Scalar.h"
  44 #include "llvm/ADT/StringExtras.h"
  45 #include "llvm/Config/config.h"
  46
  47
  48 #include <fstream>
  49 #include <unistd.h>
  50 #include <stdlib.h>
  51 #include <fcntl.h>
  52
  53
  54 using namespace llvm;
  55
  56 static cl::opt<bool> DisableInline("disable-inlining",
  57   cl::desc("Do not run the inliner pass"));
  58
  59
  60 const char* LTOCodeGenerator::getVersionString()
  61 {
  62 #ifdef LLVM_VERSION_INFO
  63     return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
  64 #else
  65     return PACKAGE_NAME " version " PACKAGE_VERSION;
  66 #endif
  67 }
  68
  69
  70 LTOCodeGenerator::LTOCodeGenerator()
  71     : _linker("LinkTimeOptimizer", "ld-temp.o"), _target(NULL),
  72       _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
  73       _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
  74       _nativeObjectFile(NULL)
  75 {
  76
  77 }
  78
  79 LTOCodeGenerator::~LTOCodeGenerator()
  80 {
  81     delete _target;
  82     delete _nativeObjectFile;
  83 }
  84
  85
  86
  87 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
  88 {
  89     return _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
  90 }
  91
  92
  93 bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
  94 {
  95     switch (debug) {
  96         case LTO_DEBUG_MODEL_NONE:
  97             _emitDwarfDebugInfo = false;
  98             return false;
  99
 100         case LTO_DEBUG_MODEL_DWARF:
 101             _emitDwarfDebugInfo = true;
 102             return false;
 103     }
 104     errMsg = "unknown debug format";
 105     return true;
 106 }
 107
 108
 109 bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
 110                                                         std::string& errMsg)
 111 {
 112     switch (model) {
 113         case LTO_CODEGEN_PIC_MODEL_STATIC:
 114         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 115         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 116             _codeModel = model;
 117             return false;
 118     }
 119     errMsg = "unknown pic model";
 120     return true;
 121 }
 122
 123 void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
 124 {
 125     _mustPreserveSymbols[sym] = 1;
 126 }
 127
 128
 129 bool LTOCodeGenerator::writeMergedModules(const char* path, std::string& errMsg)
 130 {
 131     if ( this->determineTarget(errMsg) )
 132         return true;
 133
 134     // mark which symbols can not be internalized
 135     this->applyScopeRestrictions();
 136
 137     // create output file
 138     std::ofstream out(path, std::ios_base::out|std::ios::trunc|std::ios::binary);
 139     if ( out.fail() ) {
 140         errMsg = "could not open bitcode file for writing: ";
 141         errMsg += path;
 142         return true;
 143     }
 144
 145     // write bitcode to it
 146     WriteBitcodeToFile(_linker.getModule(), out);
 147     if ( out.fail() ) {
 148         errMsg = "could not write bitcode file: ";
 149         errMsg += path;
 150         return true;
 151     }
 152
 153     return false;
 154 }
 155
 156
 157 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
 158 {
 159     // make unique temp .s file to put generated assembly code
 160     sys::Path uniqueAsmPath("lto-llvm.s");
 161     if ( uniqueAsmPath.createTemporaryFileOnDisk(true, &errMsg) )
 162         return NULL;
 163     sys::RemoveFileOnSignal(uniqueAsmPath);
 164
 165     // generate assembly code
 166     std::string error;
 167     bool genResult = false;
 168     {
 169       raw_fd_ostream asmFile(uniqueAsmPath.c_str(), error);
 170       genResult = this->generateAssemblyCode(asmFile, errMsg);
 171     }
 172     if ( genResult ) {
 173         if ( uniqueAsmPath.exists() )
 174             uniqueAsmPath.eraseFromDisk();
 175         return NULL;
 176     }
 177
 178     // make unique temp .o file to put generated object file
 179     sys::PathWithStatus uniqueObjPath("lto-llvm.o");
 180     if ( uniqueObjPath.createTemporaryFileOnDisk(true, &errMsg) ) {
 181         if ( uniqueAsmPath.exists() )
 182             uniqueAsmPath.eraseFromDisk();
 183         return NULL;
 184     }
 185     sys::RemoveFileOnSignal(uniqueObjPath);
 186
 187     // assemble the assembly code
 188     const std::string& uniqueObjStr = uniqueObjPath.toString();
 189     bool asmResult = this->assemble(uniqueAsmPath.toString(),
 190                                                         uniqueObjStr, errMsg);
 191     if ( !asmResult ) {
 192         // remove old buffer if compile() called twice
 193         delete _nativeObjectFile;
 194
 195         // read .o file into memory buffer
 196         _nativeObjectFile = MemoryBuffer::getFile(uniqueObjStr.c_str(),&errMsg);
 197     }
 198
 199     // remove temp files
 200     uniqueAsmPath.eraseFromDisk();
 201     uniqueObjPath.eraseFromDisk();
 202
 203     // return buffer, unless error
 204     if ( _nativeObjectFile == NULL )
 205         return NULL;
 206     *length = _nativeObjectFile->getBufferSize();
 207     return _nativeObjectFile->getBufferStart();
 208 }
 209
 210
 211 bool LTOCodeGenerator::assemble(const std::string& asmPath,
 212                                 const std::string& objPath, std::string& errMsg)
 213 {
 214     // find compiler driver
 215     const sys::Path gcc = sys::Program::FindProgramByName("gcc");
 216     if ( gcc.isEmpty() ) {
 217         errMsg = "can't locate gcc";
 218         return true;
 219     }
 220
 221     // build argument list
 222     std::vector<const char*> args;
 223     std::string targetTriple = _linker.getModule()->getTargetTriple();
 224     args.push_back(gcc.c_str());
 225     if ( targetTriple.find("darwin") != targetTriple.size() ) {
 226         if (strncmp(targetTriple.c_str(), "i686-apple-", 11) == 0) {
 227             args.push_back("-arch");
 228             args.push_back("i386");
 229         }
 230         else if (strncmp(targetTriple.c_str(), "x86_64-apple-", 13) == 0) {
 231             args.push_back("-arch");
 232             args.push_back("x86_64");
 233         }
 234         else if (strncmp(targetTriple.c_str(), "powerpc-apple-", 14) == 0) {
 235             args.push_back("-arch");
 236             args.push_back("ppc");
 237         }
 238         else if (strncmp(targetTriple.c_str(), "powerpc64-apple-", 16) == 0) {
 239             args.push_back("-arch");
 240             args.push_back("ppc64");
 241         }
 242     }
 243     args.push_back("-c");
 244     args.push_back("-x");
 245     args.push_back("assembler");
 246     args.push_back("-o");
 247     args.push_back(objPath.c_str());
 248     args.push_back(asmPath.c_str());
 249     args.push_back(0);
 250
 251     // invoke assembler
 252     if ( sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 0, 0, &errMsg) ) {
 253         errMsg = "error in assembly";
 254         return true;
 255     }
 256     return false; // success
 257 }
 258
 259
 260
 261 bool LTOCodeGenerator::determineTarget(std::string& errMsg)
 262 {
 263     if ( _target == NULL ) {
 264         // create target machine from info for merged modules
 265         Module* mergedModule = _linker.getModule();
 266         const TargetMachineRegistry::entry* march =
 267           TargetMachineRegistry::getClosestStaticTargetForModule(
 268                                                        *mergedModule, errMsg);
 269         if ( march == NULL )
 270             return true;
 271
 272         // construct LTModule, hand over ownership of module and target
 273         std::string FeatureStr =
 274           getFeatureString(_linker.getModule()->getTargetTriple().c_str());
 275         _target = march->CtorFn(*mergedModule, FeatureStr.c_str());
 276     }
 277     return false;
 278 }
 279
 280 void LTOCodeGenerator::applyScopeRestrictions()
 281 {
 282     if ( !_scopeRestrictionsDone ) {
 283         Module* mergedModule = _linker.getModule();
 284
 285         // Start off with a verification pass.
 286         PassManager passes;
 287         passes.add(createVerifierPass());
 288
 289         // mark which symbols can not be internalized
 290         if ( !_mustPreserveSymbols.empty() ) {
 291             Mangler mangler(*mergedModule,
 292                                 _target->getTargetAsmInfo()->getGlobalPrefix());
 293             std::vector<const char*> mustPreserveList;
 294             for (Module::iterator f = mergedModule->begin(),
 295                                         e = mergedModule->end(); f != e; ++f) {
 296                 if ( !f->isDeclaration()
 297                   && _mustPreserveSymbols.count(mangler.getValueName(f)) )
 298                     mustPreserveList.push_back(::strdup(f->getName().c_str()));
 299             }
 300             for (Module::global_iterator v = mergedModule->global_begin(),
 301                                  e = mergedModule->global_end(); v !=  e; ++v) {
 302                 if ( !v->isDeclaration()
 303                   && _mustPreserveSymbols.count(mangler.getValueName(v)) )
 304                     mustPreserveList.push_back(::strdup(v->getName().c_str()));
 305             }
 306             passes.add(createInternalizePass(mustPreserveList));
 307         }
 308         // apply scope restrictions
 309         passes.run(*mergedModule);
 310
 311         _scopeRestrictionsDone = true;
 312     }
 313 }
 314
 315 /// Optimize merged modules using various IPO passes
 316 bool LTOCodeGenerator::generateAssemblyCode(raw_ostream& out,
 317                                             std::string& errMsg)
 318 {
 319     if (  this->determineTarget(errMsg) )
 320         return true;
 321
 322     // mark which symbols can not be internalized
 323     this->applyScopeRestrictions();
 324
 325     Module* mergedModule = _linker.getModule();
 326
 327      // If target supports exception handling then enable it now.
 328     if ( _target->getTargetAsmInfo()->doesSupportExceptionHandling() )
 329         llvm::ExceptionHandling = true;
 330
 331     // set codegen model
 332     switch( _codeModel ) {
 333         case LTO_CODEGEN_PIC_MODEL_STATIC:
 334             _target->setRelocationModel(Reloc::Static);
 335             break;
 336         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 337             _target->setRelocationModel(Reloc::PIC_);
 338             break;
 339         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 340             _target->setRelocationModel(Reloc::DynamicNoPIC);
 341             break;
 342     }
 343
 344     // if options were requested, set them
 345     if ( !_codegenOptions.empty() )
 346         cl::ParseCommandLineOptions(_codegenOptions.size(),
 347                                                 (char**)&_codegenOptions[0]);
 348
 349     // Instantiate the pass manager to organize the passes.
 350     PassManager passes;
 351
 352     // Start off with a verification pass.
 353     passes.add(createVerifierPass());
 354
 355     // Add an appropriate TargetData instance for this module...
 356     passes.add(new TargetData(*_target->getTargetData()));
 357
 358     // Propagate constants at call sites into the functions they call.  This
 359     // opens opportunities for globalopt (and inlining) by substituting function
 360     // pointers passed as arguments to direct uses of functions.
 361     passes.add(createIPSCCPPass());
 362
 363     // Now that we internalized some globals, see if we can hack on them!
 364     passes.add(createGlobalOptimizerPass());
 365
 366     // Linking modules together can lead to duplicated global constants, only
 367     // keep one copy of each constant...
 368     passes.add(createConstantMergePass());
 369
 370     // Remove unused arguments from functions...
 371     passes.add(createDeadArgEliminationPass());
 372
 373     // Reduce the code after globalopt and ipsccp.  Both can open up significant
 374     // simplification opportunities, and both can propagate functions through
 375     // function pointers.  When this happens, we often have to resolve varargs
 376     // calls, etc, so let instcombine do this.
 377     passes.add(createInstructionCombiningPass());
 378     if (!DisableInline)
 379         passes.add(createFunctionInliningPass()); // Inline small functions
 380     passes.add(createPruneEHPass());              // Remove dead EH info
 381     passes.add(createGlobalDCEPass());            // Remove dead functions
 382
 383     // If we didn't decide to inline a function, check to see if we can
 384     // transform it to pass arguments by value instead of by reference.
 385     passes.add(createArgumentPromotionPass());
 386
 387     // The IPO passes may leave cruft around.  Clean up after them.
 388     passes.add(createInstructionCombiningPass());
 389     passes.add(createJumpThreadingPass());        // Thread jumps.
 390     passes.add(createScalarReplAggregatesPass()); // Break up allocas
 391
 392     // Run a few AA driven optimizations here and now, to cleanup the code.
 393     passes.add(createGlobalsModRefPass());        // IP alias analysis
 394     passes.add(createLICMPass());                 // Hoist loop invariants
 395     passes.add(createGVNPass());                  // Remove common subexprs
 396     passes.add(createMemCpyOptPass());            // Remove dead memcpy's
 397     passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
 398
 399     // Cleanup and simplify the code after the scalar optimizations.
 400     passes.add(createInstructionCombiningPass());
 401     passes.add(createJumpThreadingPass());        // Thread jumps.
 402     passes.add(createPromoteMemoryToRegisterPass()); // Cleanup after threading.
 403
 404
 405     // Delete basic blocks, which optimization passes may have killed...
 406     passes.add(createCFGSimplificationPass());
 407
 408     // Now that we have optimized the program, discard unreachable functions...
 409     passes.add(createGlobalDCEPass());
 410
 411     // Make sure everything is still good.
 412     passes.add(createVerifierPass());
 413
 414     FunctionPassManager* codeGenPasses =
 415             new FunctionPassManager(new ExistingModuleProvider(mergedModule));
 416
 417     codeGenPasses->add(new TargetData(*_target->getTargetData()));
 418
 419     MachineCodeEmitter* mce = NULL;
 420
 421     switch (_target->addPassesToEmitFile(*codeGenPasses, out,
 422                                       TargetMachine::AssemblyFile, true)) {
 423         case FileModel::MachOFile:
 424             mce = AddMachOWriter(*codeGenPasses, out, *_target);
 425             break;
 426         case FileModel::ElfFile:
 427             mce = AddELFWriter(*codeGenPasses, out, *_target);
 428             break;
 429         case FileModel::AsmFile:
 430             break;
 431         case FileModel::Error:
 432         case FileModel::None:
 433             errMsg = "target file type not supported";
 434             return true;
 435     }
 436
 437     if (_target->addPassesToEmitFileFinish(*codeGenPasses, mce, true)) {
 438         errMsg = "target does not support generation of this file type";
 439         return true;
 440     }
 441
 442     // Run our queue of passes all at once now, efficiently.
 443     passes.run(*mergedModule);
 444
 445     // Run the code generator, and write assembly file
 446     codeGenPasses->doInitialization();
 447
 448     for (Module::iterator
 449            it = mergedModule->begin(), e = mergedModule->end(); it != e; ++it)
 450       if (!it->isDeclaration())
 451         codeGenPasses->run(*it);
 452
 453     codeGenPasses->doFinalization();
 454     return false; // success
 455 }
 456
 457
 458 /// Optimize merged modules using various IPO passes
 459 void LTOCodeGenerator::setCodeGenDebugOptions(const char* options)
 460 {
 461     std::string ops(options);
 462     for (std::string o = getToken(ops); !o.empty(); o = getToken(ops)) {
 463         // ParseCommandLineOptions() expects argv[0] to be program name.
 464         // Lazily add that.
 465         if ( _codegenOptions.empty() )
 466             _codegenOptions.push_back("libLTO");
 467         _codegenOptions.push_back(strdup(o.c_str()));
 468     }
 469 }