1 //===- LTO.cpp ------------------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "LTO.h" 10 #include "Config.h" 11 #include "Driver.h" 12 #include "InputFiles.h" 13 #include "Symbols.h" 14 #include "Target.h" 15 16 #include "lld/Common/Args.h" 17 #include "lld/Common/ErrorHandler.h" 18 #include "lld/Common/Strings.h" 19 #include "lld/Common/TargetOptionsCommandFlags.h" 20 #include "llvm/LTO/Caching.h" 21 #include "llvm/LTO/Config.h" 22 #include "llvm/LTO/LTO.h" 23 #include "llvm/Support/FileSystem.h" 24 #include "llvm/Support/Path.h" 25 #include "llvm/Support/raw_ostream.h" 26 #include "llvm/Transforms/ObjCARC.h" 27 28 using namespace lld; 29 using namespace lld::macho; 30 using namespace llvm; 31 using namespace llvm::MachO; 32 using namespace llvm::sys; 33 34 static lto::Config createConfig() { 35 lto::Config c; 36 c.Options = initTargetOptionsFromCodeGenFlags(); 37 c.CodeModel = getCodeModelFromCMModel(); 38 c.CPU = getCPUStr(); 39 c.MAttrs = getMAttrs(); 40 c.UseNewPM = config->ltoNewPassManager; 41 c.PreCodeGenPassesHook = [](legacy::PassManager &pm) { 42 pm.add(createObjCARCContractPass()); 43 }; 44 c.TimeTraceEnabled = config->timeTraceEnabled; 45 c.TimeTraceGranularity = config->timeTraceGranularity; 46 c.OptLevel = config->ltoo; 47 c.CGOptLevel = args::getCGOptLevel(config->ltoo); 48 if (config->saveTemps) 49 checkError(c.addSaveTemps(config->outputFile.str() + ".", 50 /*UseInputModulePath=*/true)); 51 return c; 52 } 53 54 BitcodeCompiler::BitcodeCompiler() { 55 lto::ThinBackend backend = lto::createInProcessThinBackend( 56 heavyweight_hardware_concurrency(config->thinLTOJobs)); 57 ltoObj = std::make_unique<lto::LTO>(createConfig(), backend); 58 } 59 60 void BitcodeCompiler::add(BitcodeFile &f) { 61 ArrayRef<lto::InputFile::Symbol> objSyms = f.obj->symbols(); 62 std::vector<lto::SymbolResolution> resols; 63 resols.reserve(objSyms.size()); 64 65 // Provide a resolution to the LTO API for each symbol. 66 auto symIt = f.symbols.begin(); 67 for (const lto::InputFile::Symbol &objSym : objSyms) { 68 resols.emplace_back(); 69 lto::SymbolResolution &r = resols.back(); 70 Symbol *sym = *symIt++; 71 72 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 73 // reports two symbols for module ASM defined. Without this check, lld 74 // flags an undefined in IR with a definition in ASM as prevailing. 75 // Once IRObjectFile is fixed to report only one symbol this hack can 76 // be removed. 77 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f; 78 79 // FIXME: What about other output types? And we can probably be less 80 // restrictive with -flat_namespace, but it's an infrequent use case. 81 // FIXME: Honor config->exportDynamic. 82 r.VisibleToRegularObj = config->outputType != MH_EXECUTE || 83 config->namespaceKind == NamespaceKind::flat || 84 sym->isUsedInRegularObj; 85 86 // Un-define the symbol so that we don't get duplicate symbol errors when we 87 // load the ObjFile emitted by LTO compilation. 88 if (r.Prevailing) 89 replaceSymbol<Undefined>(sym, sym->getName(), sym->getFile(), 90 RefState::Strong); 91 92 // TODO: set the other resolution configs properly 93 } 94 checkError(ltoObj->add(std::move(f.obj), resols)); 95 } 96 97 // Merge all the bitcode files we have seen, codegen the result 98 // and return the resulting ObjectFile(s). 99 std::vector<ObjFile *> BitcodeCompiler::compile() { 100 unsigned maxTasks = ltoObj->getMaxTasks(); 101 buf.resize(maxTasks); 102 files.resize(maxTasks); 103 104 // The -cache_path_lto option specifies the path to a directory in which 105 // to cache native object files for ThinLTO incremental builds. If a path was 106 // specified, configure LTO to use it as the cache directory. 107 lto::NativeObjectCache cache; 108 if (!config->thinLTOCacheDir.empty()) 109 cache = check( 110 lto::localCache(config->thinLTOCacheDir, 111 [&](size_t task, std::unique_ptr<MemoryBuffer> mb) { 112 files[task] = std::move(mb); 113 })); 114 115 checkError(ltoObj->run( 116 [&](size_t task) { 117 return std::make_unique<lto::NativeObjectStream>( 118 std::make_unique<raw_svector_ostream>(buf[task])); 119 }, 120 cache)); 121 122 if (!config->thinLTOCacheDir.empty()) 123 pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy); 124 125 if (config->saveTemps) { 126 if (!buf[0].empty()) 127 saveBuffer(buf[0], config->outputFile + ".lto.o"); 128 for (unsigned i = 1; i != maxTasks; ++i) 129 saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o"); 130 } 131 132 if (!config->ltoObjPath.empty()) 133 fs::create_directories(config->ltoObjPath); 134 135 std::vector<ObjFile *> ret; 136 for (unsigned i = 0; i != maxTasks; ++i) { 137 if (buf[i].empty()) 138 continue; 139 SmallString<261> filePath("/tmp/lto.tmp"); 140 uint32_t modTime = 0; 141 if (!config->ltoObjPath.empty()) { 142 filePath = config->ltoObjPath; 143 path::append(filePath, Twine(i) + "." + 144 getArchitectureName(config->arch()) + 145 ".lto.o"); 146 saveBuffer(buf[i], filePath); 147 modTime = getModTime(filePath); 148 } 149 ret.push_back(make<ObjFile>( 150 MemoryBufferRef(buf[i], saver.save(filePath.str())), modTime, "")); 151 } 152 for (std::unique_ptr<MemoryBuffer> &file : files) 153 if (file) 154 ret.push_back(make<ObjFile>(*file, 0, "")); 155 return ret; 156 } 157