//===-lto.cpp - LLVM Link Time Optimizer ----------------------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the Link Time Optimization library. This library is // intended to be used by linker to optimize code at link time. // //===----------------------------------------------------------------------===// #include "llvm/Module.h" #include "llvm/PassManager.h" #include "llvm/Linker.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/ModuleProvider.h" #include "llvm/Bitcode/ReaderWriter.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/FileUtilities.h" #include "llvm/Support/SystemUtils.h" #include "llvm/Support/Mangler.h" #include "llvm/Support/MemoryBuffer.h" #include "llvm/System/Program.h" #include "llvm/System/Signals.h" #include "llvm/Analysis/Passes.h" #include "llvm/Analysis/LoopPass.h" #include "llvm/Analysis/Verifier.h" #include "llvm/CodeGen/FileWriters.h" #include "llvm/Target/SubtargetFeature.h" #include "llvm/Target/TargetOptions.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/TargetMachineRegistry.h" #include "llvm/Target/TargetAsmInfo.h" #include "llvm/Transforms/IPO.h" #include "llvm/Transforms/Scalar.h" #include "llvm/Analysis/LoadValueNumbering.h" #include "llvm/Support/MathExtras.h" #include "llvm/LinkTimeOptimizer.h" #include #include using namespace llvm; extern "C" llvm::LinkTimeOptimizer *createLLVMOptimizer(unsigned VERSION) { // Linker records LLVM_LTO_VERSION based on llvm optimizer available // during linker build. Match linker's recorded LTO VERSION number // with installed llvm optimizer version. If these numbers do not match // then linker may not be able to use llvm optimizer dynamically. if (VERSION != LLVM_LTO_VERSION) return NULL; llvm::LTO *l = new llvm::LTO(); return l; } /// If symbol is not used then make it internal and let optimizer takes /// care of it. void LLVMSymbol::mayBeNotUsed() { gv->setLinkage(GlobalValue::InternalLinkage); } // Map LLVM LinkageType to LTO LinakgeType static LTOLinkageTypes getLTOLinkageType(GlobalValue *v) { LTOLinkageTypes lt; if (v->hasExternalLinkage()) lt = LTOExternalLinkage; else if (v->hasLinkOnceLinkage()) lt = LTOLinkOnceLinkage; else if (v->hasWeakLinkage()) lt = LTOWeakLinkage; else // Otherwise it is internal linkage for link time optimizer lt = LTOInternalLinkage; return lt; } // MAP LLVM VisibilityType to LTO VisibilityType static LTOVisibilityTypes getLTOVisibilityType(GlobalValue *v) { LTOVisibilityTypes vis; if (v->hasHiddenVisibility()) vis = LTOHiddenVisibility; else if (v->hasProtectedVisibility()) vis = LTOProtectedVisibility; else vis = LTODefaultVisibility; return vis; } // Find exeternal symbols referenced by VALUE. This is a recursive function. static void findExternalRefs(Value *value, std::set &references, Mangler &mangler) { if (GlobalValue *gv = dyn_cast(value)) { LTOLinkageTypes lt = getLTOLinkageType(gv); if (lt != LTOInternalLinkage && strncmp (gv->getName().c_str(), "llvm.", 5)) references.insert(mangler.getValueName(gv)); } // GlobalValue, even with InternalLinkage type, may have operands with // ExternalLinkage type. Do not ignore these operands. if (Constant *c = dyn_cast(value)) // Handle ConstantExpr, ConstantStruct, ConstantArry etc.. for (unsigned i = 0, e = c->getNumOperands(); i != e; ++i) findExternalRefs(c->getOperand(i), references, mangler); } /// If Module with InputFilename is available then remove it from allModules /// and call delete on it. void LTO::removeModule (const std::string &InputFilename) { NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); if (pos == allModules.end()) return; Module *m = pos->second; allModules.erase(pos); delete m; } /// InputFilename is a LLVM bitcode file. If Module with InputFilename is /// available then return it. Otherwise parseInputFilename. Module * LTO::getModule(const std::string &InputFilename) { Module *m = NULL; NameToModuleMap::iterator pos = allModules.find(InputFilename.c_str()); if (pos != allModules.end()) m = allModules[InputFilename.c_str()]; else { if (MemoryBuffer *Buffer = MemoryBuffer::getFile(&InputFilename[0], InputFilename.size())) { m = ParseBitcodeFile(Buffer); delete Buffer; } allModules[InputFilename.c_str()] = m; } return m; } /// InputFilename is a LLVM bitcode file. Reade this bitcode file and /// set corresponding target triplet string. void LTO::getTargetTriple(const std::string &InputFilename, std::string &targetTriple) { Module *m = getModule(InputFilename); if (m) targetTriple = m->getTargetTriple(); } /// InputFilename is a LLVM bitcode file. Read it using bitcode reader. /// Collect global functions and symbol names in symbols vector. /// Collect external references in references vector. /// Return LTO_READ_SUCCESS if there is no error. enum LTOStatus LTO::readLLVMObjectFile(const std::string &InputFilename, NameToSymbolMap &symbols, std::set &references) { Module *m = getModule(InputFilename); if (!m) return LTO_READ_FAILURE; // Collect Target info getTarget(m); if (!Target) return LTO_READ_FAILURE; // Use mangler to add GlobalPrefix to names to match linker names. // FIXME : Instead of hard coding "-" use GlobalPrefix. Mangler mangler(*m, Target->getTargetAsmInfo()->getGlobalPrefix()); modules.push_back(m); for (Module::iterator f = m->begin(), e = m->end(); f != e; ++f) { LTOLinkageTypes lt = getLTOLinkageType(f); LTOVisibilityTypes vis = getLTOVisibilityType(f); if (!f->isDeclaration() && lt != LTOInternalLinkage && strncmp (f->getName().c_str(), "llvm.", 5)) { int alignment = ( 16 > f->getAlignment() ? 16 : f->getAlignment()); LLVMSymbol *newSymbol = new LLVMSymbol(lt, vis, f, f->getName(), mangler.getValueName(f), Log2_32(alignment)); symbols[newSymbol->getMangledName()] = newSymbol; allSymbols[newSymbol->getMangledName()] = newSymbol; } // Collect external symbols referenced by this function. for (Function::iterator b = f->begin(), fe = f->end(); b != fe; ++b) for (BasicBlock::iterator i = b->begin(), be = b->end(); i != be; ++i) { for (unsigned count = 0, total = i->getNumOperands(); count != total; ++count) findExternalRefs(i->getOperand(count), references, mangler); } } for (Module::global_iterator v = m->global_begin(), e = m->global_end(); v != e; ++v) { LTOLinkageTypes lt = getLTOLinkageType(v); LTOVisibilityTypes vis = getLTOVisibilityType(v); if (!v->isDeclaration() && lt != LTOInternalLinkage && strncmp (v->getName().c_str(), "llvm.", 5)) { const TargetData *TD = Target->getTargetData(); LLVMSymbol *newSymbol = new LLVMSymbol(lt, vis, v, v->getName(), mangler.getValueName(v), TD->getPreferredAlignmentLog(v)); symbols[newSymbol->getMangledName()] = newSymbol; allSymbols[newSymbol->getMangledName()] = newSymbol; for (unsigned count = 0, total = v->getNumOperands(); count != total; ++count) findExternalRefs(v->getOperand(count), references, mangler); } } return LTO_READ_SUCCESS; } /// Get TargetMachine. /// Use module M to find appropriate Target. void LTO::getTarget (Module *M) { if (Target) return; std::string Err; const TargetMachineRegistry::entry* March = TargetMachineRegistry::getClosestStaticTargetForModule(*M, Err); if (March == 0) return; // Create target SubtargetFeatures Features; std::string FeatureStr; std::string TargetTriple = M->getTargetTriple(); if (strncmp(TargetTriple.c_str(), "powerpc-apple-", 14) == 0) Features.AddFeature("altivec", true); else if (strncmp(TargetTriple.c_str(), "powerpc64-apple-", 16) == 0) { Features.AddFeature("64bit", true); Features.AddFeature("altivec", true); } FeatureStr = Features.getString(); Target = March->CtorFn(*M, FeatureStr); } /// Optimize module M using various IPO passes. Use exportList to /// internalize selected symbols. Target platform is selected /// based on information available to module M. No new target /// features are selected. enum LTOStatus LTO::optimize(Module *M, std::ostream &Out, std::vector &exportList) { // Instantiate the pass manager to organize the passes. PassManager Passes; // Collect Target info getTarget(M); if (!Target) return LTO_NO_TARGET; // If target supports exception handling then enable it now. if (Target->getTargetAsmInfo()->doesSupportExceptionHandling()) ExceptionHandling = true; // Start off with a verification pass. Passes.add(createVerifierPass()); // Add an appropriate TargetData instance for this module... Passes.add(new TargetData(*Target->getTargetData())); // Internalize symbols if export list is nonemty if (!exportList.empty()) Passes.add(createInternalizePass(exportList)); // Now that we internalized some globals, see if we can hack on them! Passes.add(createGlobalOptimizerPass()); // Linking modules together can lead to duplicated global constants, only // keep one copy of each constant... Passes.add(createConstantMergePass()); // If the -s command line option was specified, strip the symbols out of the // resulting program to make it smaller. -s is a GLD option that we are // supporting. Passes.add(createStripSymbolsPass()); // Propagate constants at call sites into the functions they call. Passes.add(createIPConstantPropagationPass()); // Remove unused arguments from functions... Passes.add(createDeadArgEliminationPass()); Passes.add(createFunctionInliningPass()); // Inline small functions Passes.add(createPruneEHPass()); // Remove dead EH info Passes.add(createGlobalDCEPass()); // Remove dead functions // If we didn't decide to inline a function, check to see if we can // transform it to pass arguments by value instead of by reference. Passes.add(createArgumentPromotionPass()); // The IPO passes may leave cruft around. Clean up after them. Passes.add(createInstructionCombiningPass()); Passes.add(createScalarReplAggregatesPass()); // Break up allocas // Run a few AA driven optimizations here and now, to cleanup the code. Passes.add(createGlobalsModRefPass()); // IP alias analysis Passes.add(createLICMPass()); // Hoist loop invariants Passes.add(createLoadValueNumberingPass()); // GVN for load instrs Passes.add(createGCSEPass()); // Remove common subexprs Passes.add(createDeadStoreEliminationPass()); // Nuke dead stores // Cleanup and simplify the code after the scalar optimizations. Passes.add(createInstructionCombiningPass()); // Delete basic blocks, which optimization passes may have killed... Passes.add(createCFGSimplificationPass()); // Now that we have optimized the program, discard unreachable functions... Passes.add(createGlobalDCEPass()); // Make sure everything is still good. Passes.add(createVerifierPass()); FunctionPassManager *CodeGenPasses = new FunctionPassManager(new ExistingModuleProvider(M)); CodeGenPasses->add(new TargetData(*Target->getTargetData())); MachineCodeEmitter *MCE = 0; switch (Target->addPassesToEmitFile(*CodeGenPasses, Out, TargetMachine::AssemblyFile, true)) { default: case FileModel::Error: return LTO_WRITE_FAILURE; case FileModel::AsmFile: break; case FileModel::MachOFile: MCE = AddMachOWriter(*CodeGenPasses, Out, *Target); break; case FileModel::ElfFile: MCE = AddELFWriter(*CodeGenPasses, Out, *Target); break; } if (Target->addPassesToEmitFileFinish(*CodeGenPasses, MCE, true)) return LTO_WRITE_FAILURE; // Run our queue of passes all at once now, efficiently. Passes.run(*M); // Run the code generator, if present. CodeGenPasses->doInitialization(); for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) { if (!I->isDeclaration()) CodeGenPasses->run(*I); } CodeGenPasses->doFinalization(); return LTO_OPT_SUCCESS; } ///Link all modules together and optimize them using IPO. Generate /// native object file using OutputFilename /// Return appropriate LTOStatus. enum LTOStatus LTO::optimizeModules(const std::string &OutputFilename, std::vector &exportList, std::string &targetTriple, bool saveTemps, const char *FinalOutputFilename) { if (modules.empty()) return LTO_NO_WORK; std::ios::openmode io_mode = std::ios::out | std::ios::trunc | std::ios::binary; std::string *errMsg = NULL; Module *bigOne = modules[0]; Linker theLinker("LinkTimeOptimizer", bigOne, false); for (unsigned i = 1, e = modules.size(); i != e; ++i) if (theLinker.LinkModules(bigOne, modules[i], errMsg)) return LTO_MODULE_MERGE_FAILURE; // all modules have been handed off to the linker. modules.clear(); sys::Path FinalOutputPath(FinalOutputFilename); FinalOutputPath.eraseSuffix(); switch(CGModel) { case LTO_CGM_Dynamic: Target->setRelocationModel(Reloc::PIC_); break; case LTO_CGM_DynamicNoPIC: Target->setRelocationModel(Reloc::DynamicNoPIC); break; case LTO_CGM_Static: Target->setRelocationModel(Reloc::Static); break; } if (saveTemps) { std::string tempFileName(FinalOutputPath.c_str()); tempFileName += "0.bc"; std::ofstream Out(tempFileName.c_str(), io_mode); WriteBitcodeToFile(bigOne, Out); } // Strip leading underscore because it was added to match names // seen by linker. for (unsigned i = 0, e = exportList.size(); i != e; ++i) { const char *name = exportList[i]; NameToSymbolMap::iterator itr = allSymbols.find(name); if (itr != allSymbols.end()) exportList[i] = allSymbols[name]->getName(); } std::string ErrMsg; sys::Path TempDir = sys::Path::GetTemporaryDirectory(&ErrMsg); if (TempDir.isEmpty()) { cerr << "lto: " << ErrMsg << "\n"; return LTO_WRITE_FAILURE; } sys::Path tmpAsmFilePath(TempDir); if (!tmpAsmFilePath.appendComponent("lto")) { cerr << "lto: " << ErrMsg << "\n"; TempDir.eraseFromDisk(true); return LTO_WRITE_FAILURE; } if (tmpAsmFilePath.createTemporaryFileOnDisk(true, &ErrMsg)) { cerr << "lto: " << ErrMsg << "\n"; TempDir.eraseFromDisk(true); return LTO_WRITE_FAILURE; } sys::RemoveFileOnSignal(tmpAsmFilePath); std::ofstream asmFile(tmpAsmFilePath.c_str(), io_mode); if (!asmFile.is_open() || asmFile.bad()) { if (tmpAsmFilePath.exists()) { tmpAsmFilePath.eraseFromDisk(); TempDir.eraseFromDisk(true); } return LTO_WRITE_FAILURE; } enum LTOStatus status = optimize(bigOne, asmFile, exportList); asmFile.close(); if (status != LTO_OPT_SUCCESS) { tmpAsmFilePath.eraseFromDisk(); TempDir.eraseFromDisk(true); return status; } if (saveTemps) { std::string tempFileName(FinalOutputPath.c_str()); tempFileName += "1.bc"; std::ofstream Out(tempFileName.c_str(), io_mode); WriteBitcodeToFile(bigOne, Out); } targetTriple = bigOne->getTargetTriple(); // Run GCC to assemble and link the program into native code. // // Note: // We can't just assemble and link the file with the system assembler // and linker because we don't know where to put the _start symbol. // GCC mysteriously knows how to do it. const sys::Path gcc = sys::Program::FindProgramByName("gcc"); if (gcc.isEmpty()) { tmpAsmFilePath.eraseFromDisk(); TempDir.eraseFromDisk(true); return LTO_ASM_FAILURE; } std::vector args; args.push_back(gcc.c_str()); if (strncmp(targetTriple.c_str(), "i686-apple-", 11) == 0) { args.push_back("-arch"); args.push_back("i386"); } if (strncmp(targetTriple.c_str(), "x86_64-apple-", 13) == 0) { args.push_back("-arch"); args.push_back("x86_64"); } if (strncmp(targetTriple.c_str(), "powerpc-apple-", 14) == 0) { args.push_back("-arch"); args.push_back("ppc"); } if (strncmp(targetTriple.c_str(), "powerpc64-apple-", 16) == 0) { args.push_back("-arch"); args.push_back("ppc64"); } args.push_back("-c"); args.push_back("-x"); args.push_back("assembler"); args.push_back("-o"); args.push_back(OutputFilename.c_str()); args.push_back(tmpAsmFilePath.c_str()); args.push_back(0); if (sys::Program::ExecuteAndWait(gcc, &args[0], 0, 0, 0, 0, &ErrMsg)) { cerr << "lto: " << ErrMsg << "\n"; return LTO_ASM_FAILURE; } tmpAsmFilePath.eraseFromDisk(); TempDir.eraseFromDisk(true); return LTO_OPT_SUCCESS; } void LTO::printVersion() { cl::PrintVersionMessage(); } /// Unused pure-virtual destructor. Must remain empty. LinkTimeOptimizer::~LinkTimeOptimizer() {} /// Destruct LTO. Delete all modules, symbols and target. LTO::~LTO() { for (std::vector::iterator itr = modules.begin(), e = modules.end(); itr != e; ++itr) delete *itr; modules.clear(); for (NameToSymbolMap::iterator itr = allSymbols.begin(), e = allSymbols.end(); itr != e; ++itr) delete itr->second; allSymbols.clear(); delete Target; }