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