tools/lto2/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/SystemUtils.h"
  27 #include "llvm/Support/Mangler.h"
  28 #include "llvm/Support/MemoryBuffer.h"
  29 #include "llvm/System/Signals.h"
  30 #include "llvm/Analysis/Passes.h"
  31 #include "llvm/Analysis/LoopPass.h"
  32 #include "llvm/Analysis/Verifier.h"
  33 #include "llvm/Analysis/LoadValueNumbering.h"
  34 #include "llvm/CodeGen/FileWriters.h"
  35 #include "llvm/Target/TargetOptions.h"
  36 #include "llvm/Target/TargetData.h"
  37 #include "llvm/Target/TargetMachine.h"
  38 #include "llvm/Target/TargetMachineRegistry.h"
  39 #include "llvm/Target/TargetAsmInfo.h"
  40 #include "llvm/Transforms/IPO.h"
  41 #include "llvm/Transforms/Scalar.h"
  42 #include "llvm/Config/config.h"
  43
  44
  45 #include <fstream>
  46 #include <unistd.h>
  47 #include <stdlib.h>
  48 #include <fcntl.h>
  49
  50
  51 using namespace llvm;
  52
  53
  54
  55 const char* LTOCodeGenerator::getVersionString()
  56 {
  57 #ifdef LLVM_VERSION_INFO
  58     return PACKAGE_NAME " version " PACKAGE_VERSION ", " LLVM_VERSION_INFO;
  59 #else
  60     return PACKAGE_NAME " version " PACKAGE_VERSION;
  61 #endif
  62 }
  63
  64
  65 LTOCodeGenerator::LTOCodeGenerator()
  66     : _linker("LinkTimeOptimizer", "ld-temp.o"), _target(NULL),
  67       _emitDwarfDebugInfo(false), _scopeRestrictionsDone(false),
  68       _codeModel(LTO_CODEGEN_PIC_MODEL_DYNAMIC),
  69       _nativeObjectFile(NULL)
  70 {
  71
  72 }
  73
  74 LTOCodeGenerator::~LTOCodeGenerator()
  75 {
  76     delete _target;
  77     delete _nativeObjectFile;
  78 }
  79
  80
  81
  82 bool LTOCodeGenerator::addModule(LTOModule* mod, std::string& errMsg)
  83 {
  84     return _linker.LinkInModule(mod->getLLVVMModule(), &errMsg);
  85 }
  86
  87
  88 bool LTOCodeGenerator::setDebugInfo(lto_debug_model debug, std::string& errMsg)
  89 {
  90     switch (debug) {
  91         case LTO_DEBUG_MODEL_NONE:
  92             _emitDwarfDebugInfo = false;
  93             return false;
  94
  95         case LTO_DEBUG_MODEL_DWARF:
  96             _emitDwarfDebugInfo = true;
  97             return false;
  98     }
  99     errMsg = "unknown debug format";
 100     return true;
 101 }
 102
 103
 104 bool LTOCodeGenerator::setCodePICModel(lto_codegen_model model,
 105                                                         std::string& errMsg)
 106 {
 107     switch (model) {
 108         case LTO_CODEGEN_PIC_MODEL_STATIC:
 109         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 110         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 111             _codeModel = model;
 112             return false;
 113     }
 114     errMsg = "unknown pic model";
 115     return true;
 116 }
 117
 118
 119 void LTOCodeGenerator::addMustPreserveSymbol(const char* sym)
 120 {
 121     _mustPreserveSymbols[sym] = 1;
 122 }
 123
 124
 125 bool LTOCodeGenerator::writeMergedModules(const char* path, std::string& errMsg)
 126 {
 127     if ( this->determineTarget(errMsg) )
 128         return true;
 129
 130     // mark which symbols can not be internalized
 131     this->applyScopeRestrictions();
 132
 133     // create output file
 134     std::ofstream out(path, std::ios_base::out|std::ios::trunc|std::ios::binary);
 135     if ( out.fail() ) {
 136         errMsg = "could not open bitcode file for writing: ";
 137         errMsg += path;
 138         return true;
 139     }
 140
 141     // write bitcode to it
 142     WriteBitcodeToFile(_linker.getModule(), out);
 143     if ( out.fail() ) {
 144         errMsg = "could not write bitcode file: ";
 145         errMsg += path;
 146         return true;
 147     }
 148
 149     return false;
 150 }
 151
 152
 153 const void* LTOCodeGenerator::compile(size_t* length, std::string& errMsg)
 154 {
 155     // make unique temp .s file to put generated assembly code
 156     sys::Path uniqueAsmPath("lto-llvm.s");
 157     if ( uniqueAsmPath.createTemporaryFileOnDisk(true, &errMsg) )
 158         return NULL;
 159     sys::RemoveFileOnSignal(uniqueAsmPath);
 160
 161     // generate assembly code
 162     std::ofstream asmFile(uniqueAsmPath.c_str());
 163     bool genResult = this->generateAssemblyCode(asmFile, errMsg);
 164     asmFile.close();
 165     if ( genResult ) {
 166         if ( uniqueAsmPath.exists() )
 167             uniqueAsmPath.eraseFromDisk();
 168         return NULL;
 169     }
 170
 171     // make unique temp .o file to put generated object file
 172     sys::PathWithStatus uniqueObjPath("lto-llvm.o");
 173     if ( uniqueObjPath.createTemporaryFileOnDisk(true, &errMsg) ) {
 174         if ( uniqueAsmPath.exists() )
 175             uniqueAsmPath.eraseFromDisk();
 176         return NULL;
 177     }
 178     sys::RemoveFileOnSignal(uniqueObjPath);
 179
 180     // assemble the assembly code
 181     const std::string& uniqueObjStr = uniqueObjPath.toString();
 182     bool asmResult = this->assemble(uniqueAsmPath.toString(),
 183                                                         uniqueObjStr, errMsg);
 184     if ( !asmResult ) {
 185         // remove old buffer if compile() called twice
 186         delete _nativeObjectFile;
 187
 188         // read .o file into memory buffer
 189         _nativeObjectFile = MemoryBuffer::getFile(uniqueObjStr.c_str(),&errMsg);
 190     }
 191
 192     // remove temp files
 193     uniqueAsmPath.eraseFromDisk();
 194     uniqueObjPath.eraseFromDisk();
 195
 196     // return buffer, unless error
 197     if ( _nativeObjectFile == NULL )
 198         return NULL;
 199     *length = _nativeObjectFile->getBufferSize();
 200     return _nativeObjectFile->getBufferStart();
 201 }
 202
 203
 204 bool LTOCodeGenerator::assemble(const std::string& asmPath,
 205                                 const std::string& objPath, std::string& errMsg)
 206 {
 207     // find compiler driver
 208     const sys::Path gcc = sys::Program::FindProgramByName("gcc");
 209     if ( gcc.isEmpty() ) {
 210         errMsg = "can't locate gcc";
 211         return true;
 212     }
 213
 214     // build argument list
 215     std::vector<const char*> args;
 216     std::string targetTriple = _linker.getModule()->getTargetTriple();
 217     args.push_back(gcc.c_str());
 218     if ( targetTriple.find("darwin") != targetTriple.size() ) {
 219         if (strncmp(targetTriple.c_str(), "i686-apple-", 11) == 0) {
 220             args.push_back("-arch");
 221             args.push_back("i386");
 222         }
 223         else if (strncmp(targetTriple.c_str(), "x86_64-apple-", 13) == 0) {
 224             args.push_back("-arch");
 225             args.push_back("x86_64");
 226         }
 227         else if (strncmp(targetTriple.c_str(), "powerpc-apple-", 14) == 0) {
 228             args.push_back("-arch");
 229             args.push_back("ppc");
 230         }
 231         else if (strncmp(targetTriple.c_str(), "powerpc64-apple-", 16) == 0) {
 232             args.push_back("-arch");
 233             args.push_back("ppc64");
 234         }
 235     }
 236     args.push_back("-c");
 237     args.push_back("-x");
 238     args.push_back("assembler");
 239     args.push_back("-o");
 240     args.push_back(objPath.c_str());
 241     args.push_back(asmPath.c_str());
 242     args.push_back(0);
 243
 244     // invoke assembler
 245     if ( sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 0, 0, &errMsg) ) {
 246         errMsg = "error in assembly";
 247         return true;
 248     }
 249     return false; // success
 250 }
 251
 252
 253
 254 bool LTOCodeGenerator::determineTarget(std::string& errMsg)
 255 {
 256     if ( _target == NULL ) {
 257         // create target machine from info for merged modules
 258         Module* mergedModule = _linker.getModule();
 259         const TargetMachineRegistry::entry* march =
 260           TargetMachineRegistry::getClosestStaticTargetForModule(
 261                                                        *mergedModule, errMsg);
 262         if ( march == NULL )
 263             return true;
 264         std::string features;
 265         _target = march->CtorFn(*mergedModule, features);
 266     }
 267     return false;
 268 }
 269
 270 void LTOCodeGenerator::applyScopeRestrictions()
 271 {
 272     if ( !_scopeRestrictionsDone ) {
 273         Module* mergedModule = _linker.getModule();
 274
 275         // Start off with a verification pass.
 276         PassManager passes;
 277         passes.add(createVerifierPass());
 278
 279         // mark which symbols can not be internalized
 280         if ( !_mustPreserveSymbols.empty() ) {
 281             Mangler mangler(*mergedModule,
 282                                 _target->getTargetAsmInfo()->getGlobalPrefix());
 283             std::vector<const char*> mustPreserveList;
 284             for (Module::iterator f = mergedModule->begin(),
 285                                         e = mergedModule->end(); f != e; ++f) {
 286                 if ( !f->isDeclaration()
 287                   && _mustPreserveSymbols.count(mangler.getValueName(f)) )
 288                     mustPreserveList.push_back(::strdup(f->getName().c_str()));
 289             }
 290             for (Module::global_iterator v = mergedModule->global_begin(),
 291                                  e = mergedModule->global_end(); v !=  e; ++v) {
 292                 if ( !v->isDeclaration()
 293                   && _mustPreserveSymbols.count(mangler.getValueName(v)) )
 294                     mustPreserveList.push_back(::strdup(v->getName().c_str()));
 295             }
 296             passes.add(createInternalizePass(mustPreserveList));
 297         }
 298         // apply scope restrictions
 299         passes.run(*mergedModule);
 300
 301         _scopeRestrictionsDone = true;
 302     }
 303 }
 304
 305
 306 /// Optimize merged modules using various IPO passes
 307 bool LTOCodeGenerator::generateAssemblyCode(std::ostream& out, std::string& errMsg)
 308 {
 309     if (  this->determineTarget(errMsg) )
 310         return true;
 311
 312     // mark which symbols can not be internalized
 313     this->applyScopeRestrictions();
 314
 315     Module* mergedModule = _linker.getModule();
 316
 317      // If target supports exception handling then enable it now.
 318     if ( _target->getTargetAsmInfo()->doesSupportExceptionHandling() )
 319         llvm::ExceptionHandling = true;
 320
 321     // set codegen model
 322     switch( _codeModel ) {
 323         case LTO_CODEGEN_PIC_MODEL_STATIC:
 324             _target->setRelocationModel(Reloc::Static);
 325             break;
 326         case LTO_CODEGEN_PIC_MODEL_DYNAMIC:
 327             _target->setRelocationModel(Reloc::PIC_);
 328             break;
 329         case LTO_CODEGEN_PIC_MODEL_DYNAMIC_NO_PIC:
 330             _target->setRelocationModel(Reloc::DynamicNoPIC);
 331             break;
 332     }
 333
 334     // Instantiate the pass manager to organize the passes.
 335     PassManager passes;
 336
 337     // Start off with a verification pass.
 338     passes.add(createVerifierPass());
 339
 340     // Add an appropriate TargetData instance for this module...
 341     passes.add(new TargetData(*_target->getTargetData()));
 342
 343     // Now that we internalized some globals, see if we can hack on them!
 344     passes.add(createGlobalOptimizerPass());
 345
 346     // Linking modules together can lead to duplicated global constants, only
 347     // keep one copy of each constant...
 348     passes.add(createConstantMergePass());
 349
 350     // If the -s command line option was specified, strip the symbols out of the
 351     // resulting program to make it smaller.  -s is a GLD option that we are
 352     // supporting.
 353     passes.add(createStripSymbolsPass());
 354
 355     // Propagate constants at call sites into the functions they call.
 356     passes.add(createIPConstantPropagationPass());
 357
 358     // Remove unused arguments from functions...
 359     passes.add(createDeadArgEliminationPass());
 360
 361     passes.add(createFunctionInliningPass()); // Inline small functions
 362
 363     passes.add(createPruneEHPass());            // Remove dead EH info
 364
 365     passes.add(createGlobalDCEPass());          // Remove dead functions
 366
 367     // If we didn't decide to inline a function, check to see if we can
 368     // transform it to pass arguments by value instead of by reference.
 369     passes.add(createArgumentPromotionPass());
 370
 371     // The IPO passes may leave cruft around.  Clean up after them.
 372     passes.add(createInstructionCombiningPass());
 373     passes.add(createJumpThreadingPass());        // Thread jumps.
 374     passes.add(createScalarReplAggregatesPass()); // Break up allocas
 375
 376     // Run a few AA driven optimizations here and now, to cleanup the code.
 377     passes.add(createGlobalsModRefPass());      // IP alias analysis
 378
 379     passes.add(createLICMPass());               // Hoist loop invariants
 380     passes.add(createGVNPass());               // Remove common subexprs
 381     passes.add(createMemCpyOptPass());  // Remove dead memcpy's
 382     passes.add(createDeadStoreEliminationPass()); // Nuke dead stores
 383
 384     // Cleanup and simplify the code after the scalar optimizations.
 385     passes.add(createInstructionCombiningPass());
 386
 387     passes.add(createJumpThreadingPass());        // Thread jumps.
 388
 389     // Delete basic blocks, which optimization passes may have killed...
 390     passes.add(createCFGSimplificationPass());
 391
 392     // Now that we have optimized the program, discard unreachable functions...
 393     passes.add(createGlobalDCEPass());
 394
 395     // Make sure everything is still good.
 396     passes.add(createVerifierPass());
 397
 398     FunctionPassManager* codeGenPasses =
 399             new FunctionPassManager(new ExistingModuleProvider(mergedModule));
 400
 401     codeGenPasses->add(new TargetData(*_target->getTargetData()));
 402
 403     MachineCodeEmitter* mce = NULL;
 404
 405     switch (_target->addPassesToEmitFile(*codeGenPasses, out,
 406                                       TargetMachine::AssemblyFile, true)) {
 407         case FileModel::MachOFile:
 408             mce = AddMachOWriter(*codeGenPasses, out, *_target);
 409             break;
 410         case FileModel::ElfFile:
 411             mce = AddELFWriter(*codeGenPasses, out, *_target);
 412             break;
 413         case FileModel::AsmFile:
 414             break;
 415         case FileModel::Error:
 416         case FileModel::None:
 417             errMsg = "target file type not supported";
 418             return true;
 419     }
 420
 421     if (_target->addPassesToEmitFileFinish(*codeGenPasses, mce, true)) {
 422         errMsg = "target does not support generation of this file type";
 423         return true;
 424     }
 425
 426     // Run our queue of passes all at once now, efficiently.
 427     passes.run(*mergedModule);
 428
 429     // Run the code generator, and write assembly file
 430     codeGenPasses->doInitialization();
 431     for (Module::iterator it = mergedModule->begin(),
 432                 e = mergedModule->end(); it != e; ++it) {
 433         if (!it->isDeclaration())
 434             codeGenPasses->run(*it);
 435     }
 436     codeGenPasses->doFinalization();
 437
 438     return false; // success
 439 }
 440
 441
 442