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/ErrorHandler.h" 17 #include "lld/Common/Strings.h" 18 #include "lld/Common/TargetOptionsCommandFlags.h" 19 #include "llvm/LTO/LTO.h" 20 #include "llvm/Support/FileSystem.h" 21 #include "llvm/Support/Path.h" 22 #include "llvm/Support/raw_ostream.h" 23 #include "llvm/Transforms/ObjCARC.h" 24 25 using namespace lld; 26 using namespace lld::macho; 27 using namespace llvm; 28 using namespace llvm::MachO; 29 using namespace llvm::sys; 30 31 static lto::Config createConfig() { 32 lto::Config c; 33 c.Options = initTargetOptionsFromCodeGenFlags(); 34 c.CodeModel = getCodeModelFromCMModel(); 35 c.CPU = getCPUStr(); 36 c.MAttrs = getMAttrs(); 37 c.UseNewPM = config->ltoNewPassManager; 38 c.PreCodeGenPassesHook = [](legacy::PassManager &pm) { 39 pm.add(createObjCARCContractPass()); 40 }; 41 c.TimeTraceEnabled = config->timeTraceEnabled; 42 c.TimeTraceGranularity = config->timeTraceGranularity; 43 if (config->saveTemps) 44 checkError(c.addSaveTemps(config->outputFile.str() + ".", 45 /*UseInputModulePath=*/true)); 46 return c; 47 } 48 49 BitcodeCompiler::BitcodeCompiler() { 50 lto::ThinBackend backend = lto::createInProcessThinBackend( 51 heavyweight_hardware_concurrency(config->thinLTOJobs)); 52 ltoObj = std::make_unique<lto::LTO>(createConfig(), backend); 53 } 54 55 void BitcodeCompiler::add(BitcodeFile &f) { 56 ArrayRef<lto::InputFile::Symbol> objSyms = f.obj->symbols(); 57 std::vector<lto::SymbolResolution> resols; 58 resols.reserve(objSyms.size()); 59 60 // Provide a resolution to the LTO API for each symbol. 61 auto symIt = f.symbols.begin(); 62 for (const lto::InputFile::Symbol &objSym : objSyms) { 63 resols.emplace_back(); 64 lto::SymbolResolution &r = resols.back(); 65 Symbol *sym = *symIt++; 66 67 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile 68 // reports two symbols for module ASM defined. Without this check, lld 69 // flags an undefined in IR with a definition in ASM as prevailing. 70 // Once IRObjectFile is fixed to report only one symbol this hack can 71 // be removed. 72 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f; 73 74 // FIXME: What about other output types? And we can probably be less 75 // restrictive with -flat_namespace, but it's an infrequent use case. 76 r.VisibleToRegularObj = config->outputType != MH_EXECUTE || 77 config->namespaceKind == NamespaceKind::flat || 78 sym->isUsedInRegularObj; 79 80 // Un-define the symbol so that we don't get duplicate symbol errors when we 81 // load the ObjFile emitted by LTO compilation. 82 if (r.Prevailing) 83 replaceSymbol<Undefined>(sym, sym->getName(), sym->getFile(), 84 RefState::Strong); 85 86 // TODO: set the other resolution configs properly 87 } 88 checkError(ltoObj->add(std::move(f.obj), resols)); 89 } 90 91 // Merge all the bitcode files we have seen, codegen the result 92 // and return the resulting ObjectFile(s). 93 std::vector<ObjFile *> BitcodeCompiler::compile() { 94 unsigned maxTasks = ltoObj->getMaxTasks(); 95 buf.resize(maxTasks); 96 97 checkError(ltoObj->run([&](size_t task) { 98 return std::make_unique<lto::NativeObjectStream>( 99 std::make_unique<raw_svector_ostream>(buf[task])); 100 })); 101 102 if (config->saveTemps) { 103 if (!buf[0].empty()) 104 saveBuffer(buf[0], config->outputFile + ".lto.o"); 105 for (unsigned i = 1; i != maxTasks; ++i) 106 saveBuffer(buf[i], config->outputFile + Twine(i) + ".lto.o"); 107 } 108 109 if (!config->ltoObjPath.empty()) 110 fs::create_directories(config->ltoObjPath); 111 112 std::vector<ObjFile *> ret; 113 for (unsigned i = 0; i != maxTasks; ++i) { 114 if (buf[i].empty()) 115 continue; 116 SmallString<261> filePath("/tmp/lto.tmp"); 117 uint32_t modTime = 0; 118 if (!config->ltoObjPath.empty()) { 119 filePath = config->ltoObjPath; 120 path::append(filePath, Twine(i) + "." + 121 getArchitectureName(config->arch()) + 122 ".lto.o"); 123 saveBuffer(buf[i], filePath); 124 modTime = getModTime(filePath); 125 } 126 ret.push_back(make<ObjFile>( 127 MemoryBufferRef(buf[i], saver.save(filePath.str())), modTime, "")); 128 } 129 130 return ret; 131 } 132