304 lines · cpp
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-exception6//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/CommonLinkerContext.h"17#include "lld/Common/Filesystem.h"18#include "lld/Common/Strings.h"19#include "lld/Common/TargetOptionsCommandFlags.h"20#include "llvm/Bitcode/BitcodeWriter.h"21#include "llvm/LTO/Config.h"22#include "llvm/LTO/LTO.h"23#include "llvm/Support/Caching.h"24#include "llvm/Support/FileSystem.h"25#include "llvm/Support/Path.h"26#include "llvm/Support/raw_ostream.h"27 28using namespace lld;29using namespace lld::macho;30using namespace llvm;31using namespace llvm::MachO;32using namespace llvm::sys;33 34static std::string getThinLTOOutputFile(StringRef modulePath) {35 return lto::getThinLTOOutputFile(modulePath, config->thinLTOPrefixReplaceOld,36 config->thinLTOPrefixReplaceNew);37}38 39static lto::Config createConfig() {40 lto::Config c;41 c.Options = initTargetOptionsFromCodeGenFlags();42 c.Options.EmitAddrsig = config->icfLevel == ICFLevel::safe;43 for (StringRef C : config->mllvmOpts)44 c.MllvmArgs.emplace_back(C.str());45 for (StringRef pluginFn : config->passPlugins)46 c.PassPlugins.push_back(std::string(pluginFn));47 c.OptPipeline = std::string(config->ltoNewPmPasses);48 c.CodeModel = getCodeModelFromCMModel();49 c.CPU = getCPUStr();50 c.MAttrs = getMAttrs();51 c.DiagHandler = diagnosticHandler;52 53 c.AlwaysEmitRegularLTOObj = !config->ltoObjPath.empty();54 55 c.TimeTraceEnabled = config->timeTraceEnabled;56 c.TimeTraceGranularity = config->timeTraceGranularity;57 c.DebugPassManager = config->ltoDebugPassManager;58 c.CSIRProfile = std::string(config->csProfilePath);59 c.RunCSIRInstr = config->csProfileGenerate;60 c.PGOWarnMismatch = config->pgoWarnMismatch;61 c.DisableVerify = config->disableVerify;62 c.OptLevel = config->ltoo;63 c.CGOptLevel = config->ltoCgo;64 if (config->saveTemps)65 checkError(c.addSaveTemps(config->outputFile.str() + ".",66 /*UseInputModulePath=*/true));67 return c;68}69 70// If `originalPath` exists, hardlinks `path` to `originalPath`. If that fails,71// or `originalPath` is not set, saves `buffer` to `path`.72static void saveOrHardlinkBuffer(StringRef buffer, const Twine &path,73 std::optional<StringRef> originalPath) {74 if (originalPath) {75 auto err = fs::create_hard_link(*originalPath, path);76 if (!err)77 return;78 }79 saveBuffer(buffer, path);80}81 82BitcodeCompiler::BitcodeCompiler() {83 // Initialize indexFile.84 if (!config->thinLTOIndexOnlyArg.empty())85 indexFile = openFile(config->thinLTOIndexOnlyArg);86 87 // Initialize ltoObj.88 lto::ThinBackend backend;89 auto onIndexWrite = [&](StringRef S) { thinIndices.erase(S); };90 if (config->thinLTOIndexOnly) {91 backend = lto::createWriteIndexesThinBackend(92 llvm::hardware_concurrency(config->thinLTOJobs),93 std::string(config->thinLTOPrefixReplaceOld),94 std::string(config->thinLTOPrefixReplaceNew),95 std::string(config->thinLTOPrefixReplaceNativeObject),96 config->thinLTOEmitImportsFiles, indexFile.get(), onIndexWrite);97 } else {98 backend = lto::createInProcessThinBackend(99 llvm::heavyweight_hardware_concurrency(config->thinLTOJobs),100 onIndexWrite, config->thinLTOEmitIndexFiles,101 config->thinLTOEmitImportsFiles);102 }103 104 ltoObj = std::make_unique<lto::LTO>(createConfig(), backend);105}106 107void BitcodeCompiler::add(BitcodeFile &f) {108 lto::InputFile &obj = *f.obj;109 110 if (config->thinLTOEmitIndexFiles)111 thinIndices.insert(obj.getName());112 113 ArrayRef<lto::InputFile::Symbol> objSyms = obj.symbols();114 std::vector<lto::SymbolResolution> resols;115 resols.reserve(objSyms.size());116 117 // Provide a resolution to the LTO API for each symbol.118 bool exportDynamic =119 config->outputType != MH_EXECUTE || config->exportDynamic;120 auto symIt = f.symbols.begin();121 for (const lto::InputFile::Symbol &objSym : objSyms) {122 resols.emplace_back();123 lto::SymbolResolution &r = resols.back();124 Symbol *sym = *symIt++;125 126 // Ideally we shouldn't check for SF_Undefined but currently IRObjectFile127 // reports two symbols for module ASM defined. Without this check, lld128 // flags an undefined in IR with a definition in ASM as prevailing.129 // Once IRObjectFile is fixed to report only one symbol this hack can130 // be removed.131 r.Prevailing = !objSym.isUndefined() && sym->getFile() == &f;132 133 if (const auto *defined = dyn_cast<Defined>(sym)) {134 r.ExportDynamic =135 defined->isExternal() && !defined->privateExtern && exportDynamic;136 r.FinalDefinitionInLinkageUnit =137 !defined->isExternalWeakDef() && !defined->interposable;138 } else if (const auto *common = dyn_cast<CommonSymbol>(sym)) {139 r.ExportDynamic = !common->privateExtern && exportDynamic;140 r.FinalDefinitionInLinkageUnit = true;141 }142 143 r.VisibleToRegularObj =144 sym->isUsedInRegularObj || (r.Prevailing && r.ExportDynamic);145 146 // Un-define the symbol so that we don't get duplicate symbol errors when we147 // load the ObjFile emitted by LTO compilation.148 if (r.Prevailing)149 replaceSymbol<Undefined>(sym, sym->getName(), sym->getFile(),150 RefState::Strong, /*wasBitcodeSymbol=*/true);151 152 // TODO: set the other resolution configs properly153 }154 checkError(ltoObj->add(std::move(f.obj), resols));155 hasFiles = true;156}157 158// If LazyObjFile has not been added to link, emit empty index files.159// This is needed because this is what GNU gold plugin does and we have a160// distributed build system that depends on that behavior.161static void thinLTOCreateEmptyIndexFiles() {162 DenseSet<StringRef> linkedBitCodeFiles;163 for (InputFile *file : inputFiles)164 if (auto *f = dyn_cast<BitcodeFile>(file))165 if (!f->lazy)166 linkedBitCodeFiles.insert(f->getName());167 168 for (InputFile *file : inputFiles) {169 if (auto *f = dyn_cast<BitcodeFile>(file)) {170 if (!f->lazy)171 continue;172 if (linkedBitCodeFiles.contains(f->getName()))173 continue;174 std::string path =175 replaceThinLTOSuffix(getThinLTOOutputFile(f->obj->getName()));176 std::unique_ptr<raw_fd_ostream> os = openFile(path + ".thinlto.bc");177 if (!os)178 continue;179 180 ModuleSummaryIndex m(/*HaveGVs=*/false);181 m.setSkipModuleByDistributedBackend();182 writeIndexToFile(m, *os);183 if (config->thinLTOEmitImportsFiles)184 openFile(path + ".imports");185 }186 }187}188 189// Merge all the bitcode files we have seen, codegen the result190// and return the resulting ObjectFile(s).191std::vector<ObjFile *> BitcodeCompiler::compile() {192 unsigned maxTasks = ltoObj->getMaxTasks();193 buf.resize(maxTasks);194 files.resize(maxTasks);195 196 // The -cache_path_lto option specifies the path to a directory in which197 // to cache native object files for ThinLTO incremental builds. If a path was198 // specified, configure LTO to use it as the cache directory.199 FileCache cache;200 if (!config->thinLTOCacheDir.empty())201 cache = check(localCache("ThinLTO", "Thin", config->thinLTOCacheDir,202 [&](size_t task, const Twine &moduleName,203 std::unique_ptr<MemoryBuffer> mb) {204 files[task] = std::move(mb);205 }));206 207 if (hasFiles)208 checkError(ltoObj->run(209 [&](size_t task, const Twine &moduleName) {210 return std::make_unique<CachedFileStream>(211 std::make_unique<raw_svector_ostream>(buf[task]));212 },213 cache));214 215 // Emit empty index files for non-indexed files216 for (StringRef s : thinIndices) {217 std::string path = getThinLTOOutputFile(s);218 openFile(path + ".thinlto.bc");219 if (config->thinLTOEmitImportsFiles)220 openFile(path + ".imports");221 }222 223 if (config->thinLTOEmitIndexFiles)224 thinLTOCreateEmptyIndexFiles();225 226 // In ThinLTO mode, Clang passes a temporary directory in -object_path_lto,227 // while the argument is a single file in FullLTO mode.228 bool objPathIsDir = true;229 if (!config->ltoObjPath.empty()) {230 if (std::error_code ec = fs::create_directories(config->ltoObjPath))231 fatal("cannot create LTO object path " + config->ltoObjPath + ": " +232 ec.message());233 234 if (!fs::is_directory(config->ltoObjPath)) {235 objPathIsDir = false;236 unsigned objCount =237 count_if(buf, [](const SmallString<0> &b) { return !b.empty(); });238 if (objCount > 1)239 fatal("-object_path_lto must specify a directory when using ThinLTO");240 }241 }242 243 auto outputFilePath = [objPathIsDir](int i) {244 SmallString<261> filePath("/tmp/lto.tmp");245 if (!config->ltoObjPath.empty()) {246 filePath = config->ltoObjPath;247 if (objPathIsDir)248 path::append(filePath, Twine(i) + "." +249 getArchitectureName(config->arch()) +250 ".lto.o");251 }252 return filePath;253 };254 255 // ThinLTO with index only option is required to generate only the index256 // files. After that, we exit from linker and ThinLTO backend runs in a257 // distributed environment.258 if (config->thinLTOIndexOnly) {259 if (!config->ltoObjPath.empty())260 saveBuffer(buf[0], outputFilePath(0));261 if (indexFile)262 indexFile->close();263 return {};264 }265 266 if (!config->thinLTOCacheDir.empty())267 pruneCache(config->thinLTOCacheDir, config->thinLTOCachePolicy, files);268 269 std::vector<ObjFile *> ret;270 for (unsigned i = 0; i < maxTasks; ++i) {271 // Get the native object contents either from the cache or from memory. Do272 // not use the cached MemoryBuffer directly to ensure dsymutil does not273 // race with the cache pruner.274 StringRef objBuf;275 std::optional<StringRef> cachePath;276 if (files[i]) {277 objBuf = files[i]->getBuffer();278 cachePath = files[i]->getBufferIdentifier();279 } else {280 objBuf = buf[i];281 }282 if (objBuf.empty())283 continue;284 285 // FIXME: should `saveTemps` and `ltoObjPath` use the same file name?286 if (config->saveTemps)287 saveBuffer(objBuf,288 config->outputFile + ((i == 0) ? "" : Twine(i)) + ".lto.o");289 290 auto filePath = outputFilePath(i);291 uint32_t modTime = 0;292 if (!config->ltoObjPath.empty()) {293 saveOrHardlinkBuffer(objBuf, filePath, cachePath);294 modTime = getModTime(filePath);295 }296 ret.push_back(make<ObjFile>(297 MemoryBufferRef(objBuf, saver().save(filePath.str())), modTime,298 /*archiveName=*/"", /*lazy=*/false,299 /*forceHidden=*/false, /*compatArch=*/true, /*builtFromBitcode=*/true));300 }301 302 return ret;303}304