630 lines · cpp
1//===-- llvm-lto2: test harness for the resolution-based LTO interface ----===//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// This program takes in a list of bitcode files, links them and performs10// link-time optimization according to the provided symbol resolutions using the11// resolution-based LTO interface, and outputs one or more object files.12//13// This program is intended to eventually replace llvm-lto which uses the legacy14// LTO interface.15//16//===----------------------------------------------------------------------===//17 18#include "llvm/Bitcode/BitcodeReader.h"19#include "llvm/CodeGen/CommandFlags.h"20#include "llvm/IR/DiagnosticPrinter.h"21#include "llvm/LTO/LTO.h"22#include "llvm/Passes/PassPlugin.h"23#include "llvm/Remarks/HotnessThresholdParser.h"24#include "llvm/Support/Caching.h"25#include "llvm/Support/CommandLine.h"26#include "llvm/Support/FileSystem.h"27#include "llvm/Support/InitLLVM.h"28#include "llvm/Support/PluginLoader.h"29#include "llvm/Support/TargetSelect.h"30#include "llvm/Support/Threading.h"31#include <atomic>32 33using namespace llvm;34using namespace lto;35 36static codegen::RegisterCodeGenFlags CGF;37 38static cl::opt<char>39 OptLevel("O",40 cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "41 "(default = '-O2')"),42 cl::Prefix, cl::init('2'));43 44static cl::opt<char> CGOptLevel(45 "cg-opt-level",46 cl::desc("Codegen optimization level (0, 1, 2 or 3, default = '2')"),47 cl::init('2'));48 49static cl::list<std::string> InputFilenames(cl::Positional, cl::OneOrMore,50 cl::desc("<input bitcode files>"));51 52static cl::opt<std::string> OutputFilename("o", cl::Required,53 cl::desc("Output filename"),54 cl::value_desc("filename"));55 56static cl::opt<std::string> CacheDir("cache-dir", cl::desc("Cache Directory"),57 cl::value_desc("directory"));58 59static cl::opt<std::string> OptPipeline("opt-pipeline",60 cl::desc("Optimizer Pipeline"),61 cl::value_desc("pipeline"));62 63static cl::opt<std::string> AAPipeline("aa-pipeline",64 cl::desc("Alias Analysis Pipeline"),65 cl::value_desc("aapipeline"));66 67static cl::opt<bool> SaveTemps("save-temps", cl::desc("Save temporary files"));68 69static cl::list<std::string> SelectSaveTemps(70 "select-save-temps",71 cl::value_desc("One, or multiple of: "72 "resolution,preopt,promote,internalize,import,opt,precodegen"73 ",combinedindex"),74 cl::desc("Save selected temporary files. Cannot be specified together with "75 "-save-temps"),76 cl::CommaSeparated);77 78constexpr const char *SaveTempsValues[] = {79 "resolution", "preopt", "promote", "internalize",80 "import", "opt", "precodegen", "combinedindex"};81 82static cl::opt<bool>83 ThinLTODistributedIndexes("thinlto-distributed-indexes",84 cl::desc("Write out individual index and "85 "import files for the "86 "distributed backend case"));87 88static cl::opt<bool>89 ThinLTOEmitIndexes("thinlto-emit-indexes",90 cl::desc("Write out individual index files via "91 "InProcessThinLTO"));92 93static cl::opt<bool>94 ThinLTOEmitImports("thinlto-emit-imports",95 cl::desc("Write out individual imports files via "96 "InProcessThinLTO. Has no effect unless "97 "specified with -thinlto-emit-indexes or "98 "-thinlto-distributed-indexes"));99 100static cl::opt<std::string> DTLTODistributor(101 "dtlto-distributor",102 cl::desc("Distributor to use for ThinLTO backend compilations. Specifying "103 "this enables DTLTO."));104 105static cl::list<std::string> DTLTODistributorArgs(106 "dtlto-distributor-arg", cl::CommaSeparated,107 cl::desc("Arguments to pass to the DTLTO distributor process."),108 cl::value_desc("arg"));109 110static cl::opt<std::string> DTLTOCompiler(111 "dtlto-compiler",112 cl::desc("Compiler to use for DTLTO ThinLTO backend compilations."));113 114static cl::list<std::string> DTLTOCompilerPrependArgs(115 "dtlto-compiler-prepend-arg", cl::CommaSeparated,116 cl::desc("Prepend arguments to pass to the remote compiler for backend "117 "compilations."),118 cl::value_desc("arg"));119 120static cl::list<std::string> DTLTOCompilerArgs(121 "dtlto-compiler-arg", cl::CommaSeparated,122 cl::desc("Arguments to pass to the remote compiler for backend "123 "compilations."),124 cl::value_desc("arg"));125 126// Default to using all available threads in the system, but using only one127// thread per core (no SMT).128// Use -thinlto-threads=all to use hardware_concurrency() instead, which means129// to use all hardware threads or cores in the system.130static cl::opt<std::string> Threads("thinlto-threads");131 132static cl::list<std::string> SymbolResolutions(133 "r",134 cl::desc("Specify a symbol resolution: filename,symbolname,resolution\n"135 "where \"resolution\" is a sequence (which may be empty) of the\n"136 "following characters:\n"137 " p - prevailing: the linker has chosen this definition of the\n"138 " symbol\n"139 " l - local: the definition of this symbol is unpreemptable at\n"140 " runtime and is known to be in this linkage unit\n"141 " x - externally visible: the definition of this symbol is\n"142 " visible outside of the LTO unit\n"143 "A resolution for each symbol must be specified"));144 145static cl::opt<std::string> OverrideTriple(146 "override-triple",147 cl::desc("Replace target triples in input files with this triple"));148 149static cl::opt<std::string> DefaultTriple(150 "default-triple",151 cl::desc(152 "Replace unspecified target triples in input files with this triple"));153 154static cl::opt<bool> RemarksWithHotness(155 "pass-remarks-with-hotness",156 cl::desc("With PGO, include profile count in optimization remarks"),157 cl::Hidden);158 159static cl::opt<std::optional<uint64_t>, false, remarks::HotnessThresholdParser>160 RemarksHotnessThreshold(161 "pass-remarks-hotness-threshold",162 cl::desc("Minimum profile count required for an "163 "optimization remark to be output."164 " Use 'auto' to apply the threshold from profile summary."),165 cl::value_desc("uint or 'auto'"), cl::init(0), cl::Hidden);166 167static cl::opt<std::string>168 RemarksFilename("pass-remarks-output",169 cl::desc("Output filename for pass remarks"),170 cl::value_desc("filename"));171 172static cl::opt<std::string>173 RemarksPasses("pass-remarks-filter",174 cl::desc("Only record optimization remarks from passes whose "175 "names match the given regular expression"),176 cl::value_desc("regex"));177 178static cl::opt<std::string> RemarksFormat(179 "pass-remarks-format",180 cl::desc("The format used for serializing remarks (default: YAML)"),181 cl::value_desc("format"), cl::init("yaml"));182 183static cl::opt<std::string>184 SamplePGOFile("lto-sample-profile-file",185 cl::desc("Specify a SamplePGO profile file"));186 187static cl::opt<std::string>188 CSPGOFile("lto-cspgo-profile-file",189 cl::desc("Specify a context sensitive PGO profile file"));190 191static cl::opt<bool>192 RunCSIRInstr("lto-cspgo-gen",193 cl::desc("Run PGO context sensitive IR instrumentation"),194 cl::Hidden);195 196static cl::opt<bool>197 DebugPassManager("debug-pass-manager", cl::Hidden,198 cl::desc("Print pass management debugging information"));199 200static cl::opt<std::string>201 StatsFile("stats-file", cl::desc("Filename to write statistics to"));202 203static cl::list<std::string>204 PassPlugins("load-pass-plugin",205 cl::desc("Load passes from plugin library"));206 207static cl::opt<LTO::LTOKind> UnifiedLTOMode(208 "unified-lto", cl::Optional,209 cl::desc("Set LTO mode with the following options:"),210 cl::values(clEnumValN(LTO::LTOK_UnifiedThin, "thin",211 "ThinLTO with Unified LTO enabled"),212 clEnumValN(LTO::LTOK_UnifiedRegular, "full",213 "Regular LTO with Unified LTO enabled"),214 clEnumValN(LTO::LTOK_Default, "default",215 "Any LTO mode without Unified LTO")),216 cl::value_desc("mode"), cl::init(LTO::LTOK_Default));217 218static cl::opt<bool> EnableFreestanding(219 "lto-freestanding",220 cl::desc("Enable Freestanding (disable builtins / TLI) during LTO"),221 cl::Hidden);222 223static cl::opt<bool> WholeProgramVisibilityEnabledInLTO(224 "whole-program-visibility-enabled-in-lto",225 cl::desc("Enable whole program visibility during LTO"), cl::Hidden);226 227static cl::opt<bool> ValidateAllVtablesHaveTypeInfos(228 "validate-all-vtables-have-type-infos",229 cl::desc("Validate that all vtables have type infos in LTO"), cl::Hidden);230 231static cl::opt<bool>232 AllVtablesHaveTypeInfos("all-vtables-have-type-infos", cl::Hidden,233 cl::desc("All vtables have type infos"));234 235static void check(Error E, std::string Msg) {236 if (!E)237 return;238 handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {239 errs() << "llvm-lto2: " << Msg << ": " << EIB.message().c_str() << '\n';240 });241 exit(1);242}243 244template <typename T> static T check(Expected<T> E, std::string Msg) {245 if (E)246 return std::move(*E);247 check(E.takeError(), Msg);248 return T();249}250 251static void check(std::error_code EC, std::string Msg) {252 check(errorCodeToError(EC), Msg);253}254 255template <typename T> static T check(ErrorOr<T> E, std::string Msg) {256 if (E)257 return std::move(*E);258 check(E.getError(), Msg);259 return T();260}261 262static int usage() {263 errs() << "Available subcommands: dump-symtab run print-guid\n";264 return 1;265}266 267static int run(int argc, char **argv) {268 cl::ParseCommandLineOptions(argc, argv, "Resolution-based LTO test harness");269 270 // FIXME: Workaround PR30396 which means that a symbol can appear271 // more than once if it is defined in module-level assembly and272 // has a GV declaration. We allow (file, symbol) pairs to have multiple273 // resolutions and apply them in the order observed.274 std::map<std::pair<std::string, std::string>, std::list<SymbolResolution>>275 CommandLineResolutions;276 for (StringRef R : SymbolResolutions) {277 StringRef Rest, FileName, SymbolName;278 std::tie(FileName, Rest) = R.split(',');279 if (Rest.empty()) {280 llvm::errs() << "invalid resolution: " << R << '\n';281 return 1;282 }283 std::tie(SymbolName, Rest) = Rest.split(',');284 SymbolResolution Res;285 for (char C : Rest) {286 if (C == 'p')287 Res.Prevailing = true;288 else if (C == 'l')289 Res.FinalDefinitionInLinkageUnit = true;290 else if (C == 'x')291 Res.VisibleToRegularObj = true;292 else if (C == 'r')293 Res.LinkerRedefined = true;294 else {295 llvm::errs() << "invalid character " << C << " in resolution: " << R296 << '\n';297 return 1;298 }299 }300 CommandLineResolutions[{std::string(FileName), std::string(SymbolName)}]301 .push_back(Res);302 }303 304 std::vector<std::unique_ptr<MemoryBuffer>> MBs;305 306 Config Conf;307 308 Conf.CPU = codegen::getMCPU();309 Conf.Options = codegen::InitTargetOptionsFromCodeGenFlags(Triple());310 Conf.MAttrs = codegen::getMAttrs();311 if (auto RM = codegen::getExplicitRelocModel())312 Conf.RelocModel = *RM;313 Conf.CodeModel = codegen::getExplicitCodeModel();314 315 Conf.DebugPassManager = DebugPassManager;316 317 if (SaveTemps && !SelectSaveTemps.empty()) {318 llvm::errs() << "-save-temps cannot be specified with -select-save-temps\n";319 return 1;320 }321 if (SaveTemps || !SelectSaveTemps.empty()) {322 DenseSet<StringRef> SaveTempsArgs;323 for (auto &S : SelectSaveTemps)324 if (is_contained(SaveTempsValues, S))325 SaveTempsArgs.insert(S);326 else {327 llvm::errs() << ("invalid -select-save-temps argument: " + S) << '\n';328 return 1;329 }330 check(Conf.addSaveTemps(OutputFilename + ".", false, SaveTempsArgs),331 "Config::addSaveTemps failed");332 }333 334 // Optimization remarks.335 Conf.RemarksFilename = RemarksFilename;336 Conf.RemarksPasses = RemarksPasses;337 Conf.RemarksWithHotness = RemarksWithHotness;338 Conf.RemarksHotnessThreshold = RemarksHotnessThreshold;339 Conf.RemarksFormat = RemarksFormat;340 341 Conf.SampleProfile = SamplePGOFile;342 Conf.CSIRProfile = CSPGOFile;343 Conf.RunCSIRInstr = RunCSIRInstr;344 345 // Run a custom pipeline, if asked for.346 Conf.OptPipeline = OptPipeline;347 Conf.AAPipeline = AAPipeline;348 349 Conf.OptLevel = OptLevel - '0';350 Conf.Freestanding = EnableFreestanding;351 llvm::append_range(Conf.PassPlugins, PassPlugins);352 if (auto Level = CodeGenOpt::parseLevel(CGOptLevel)) {353 Conf.CGOptLevel = *Level;354 } else {355 llvm::errs() << "invalid cg optimization level: " << CGOptLevel << '\n';356 return 1;357 }358 359 if (auto FT = codegen::getExplicitFileType())360 Conf.CGFileType = *FT;361 362 Conf.OverrideTriple = OverrideTriple;363 Conf.DefaultTriple = DefaultTriple;364 Conf.StatsFile = StatsFile;365 Conf.PTO.LoopVectorization = Conf.OptLevel > 1;366 Conf.PTO.SLPVectorization = Conf.OptLevel > 1;367 368 if (WholeProgramVisibilityEnabledInLTO.getNumOccurrences() > 0)369 Conf.HasWholeProgramVisibility = WholeProgramVisibilityEnabledInLTO;370 if (ValidateAllVtablesHaveTypeInfos.getNumOccurrences() > 0)371 Conf.ValidateAllVtablesHaveTypeInfos = ValidateAllVtablesHaveTypeInfos;372 if (AllVtablesHaveTypeInfos.getNumOccurrences() > 0)373 Conf.AllVtablesHaveTypeInfos = AllVtablesHaveTypeInfos;374 375 if (ThinLTODistributedIndexes && !DTLTODistributor.empty())376 llvm::errs() << "-thinlto-distributed-indexes cannot be specfied together "377 "with -dtlto-distributor\n";378 auto DTLTODistributorArgsSV = llvm::to_vector<0>(llvm::map_range(379 DTLTODistributorArgs, [](const std::string &S) { return StringRef(S); }));380 auto DTLTOCompilerPrependArgsSV = llvm::to_vector<0>(381 llvm::map_range(DTLTOCompilerPrependArgs,382 [](const std::string &S) { return StringRef(S); }));383 auto DTLTOCompilerArgsSV = llvm::to_vector<0>(llvm::map_range(384 DTLTOCompilerArgs, [](const std::string &S) { return StringRef(S); }));385 386 ThinBackend Backend;387 if (ThinLTODistributedIndexes)388 Backend = createWriteIndexesThinBackend(llvm::hardware_concurrency(Threads),389 /*OldPrefix=*/"",390 /*NewPrefix=*/"",391 /*NativeObjectPrefix=*/"",392 ThinLTOEmitImports,393 /*LinkedObjectsFile=*/nullptr,394 /*OnWrite=*/{});395 else if (!DTLTODistributor.empty()) {396 Backend = createOutOfProcessThinBackend(397 llvm::heavyweight_hardware_concurrency(Threads),398 /*OnWrite=*/{}, ThinLTOEmitIndexes, ThinLTOEmitImports, OutputFilename,399 DTLTODistributor, DTLTODistributorArgsSV, DTLTOCompiler,400 DTLTOCompilerPrependArgsSV, DTLTOCompilerArgsSV, SaveTemps);401 } else402 Backend = createInProcessThinBackend(403 llvm::heavyweight_hardware_concurrency(Threads),404 /* OnWrite */ {}, ThinLTOEmitIndexes, ThinLTOEmitImports);405 406 // Track whether we hit an error; in particular, in the multi-threaded case,407 // we can't exit() early because the rest of the threads wouldn't have had a408 // change to be join-ed, and that would result in a "terminate called without409 // an active exception". Altogether, this results in nondeterministic410 // behavior. Instead, we don't exit in the multi-threaded case, but we make411 // sure to report the error and then at the end (after joining cleanly)412 // exit(1).413 std::atomic<bool> HasErrors{false};414 Conf.DiagHandler = [&](const DiagnosticInfo &DI) {415 DiagnosticPrinterRawOStream DP(errs());416 DI.print(DP);417 errs() << '\n';418 if (DI.getSeverity() == DS_Error)419 HasErrors = true;420 };421 422 LTO::LTOKind LTOMode = UnifiedLTOMode;423 424 LTO Lto(std::move(Conf), std::move(Backend), 1, LTOMode);425 426 for (std::string F : InputFilenames) {427 std::unique_ptr<MemoryBuffer> MB = check(MemoryBuffer::getFile(F), F);428 std::unique_ptr<InputFile> Input =429 check(InputFile::create(MB->getMemBufferRef()), F);430 431 std::vector<SymbolResolution> Res;432 for (const InputFile::Symbol &Sym : Input->symbols()) {433 auto I = CommandLineResolutions.find({F, std::string(Sym.getName())});434 // If it isn't found, look for ".", which would have been added435 // (followed by a hash) when the symbol was promoted during module436 // splitting if it was defined in one part and used in the other.437 // Try looking up the symbol name before the suffix.438 if (I == CommandLineResolutions.end()) {439 auto SplitName = Sym.getName().rsplit(".");440 I = CommandLineResolutions.find({F, std::string(SplitName.first)});441 }442 if (I == CommandLineResolutions.end()) {443 llvm::errs() << argv[0] << ": missing symbol resolution for " << F444 << ',' << Sym.getName() << '\n';445 HasErrors = true;446 } else {447 Res.push_back(I->second.front());448 I->second.pop_front();449 if (I->second.empty())450 CommandLineResolutions.erase(I);451 }452 }453 454 if (HasErrors)455 continue;456 457 MBs.push_back(std::move(MB));458 check(Lto.add(std::move(Input), Res), F);459 }460 461 if (!CommandLineResolutions.empty()) {462 HasErrors = true;463 for (auto UnusedRes : CommandLineResolutions)464 llvm::errs() << argv[0] << ": unused symbol resolution for "465 << UnusedRes.first.first << ',' << UnusedRes.first.second466 << '\n';467 }468 if (HasErrors)469 return 1;470 471 auto AddStream =472 [&](size_t Task,473 const Twine &ModuleName) -> std::unique_ptr<CachedFileStream> {474 std::string Path = OutputFilename + "." + utostr(Task);475 476 std::error_code EC;477 auto S = std::make_unique<raw_fd_ostream>(Path, EC, sys::fs::OF_None);478 check(EC, Path);479 return std::make_unique<CachedFileStream>(std::move(S), Path);480 };481 482 auto AddBuffer = [&](size_t Task, const Twine &ModuleName,483 std::unique_ptr<MemoryBuffer> MB) {484 auto Stream = AddStream(Task, ModuleName);485 *Stream->OS << MB->getBuffer();486 check(Stream->commit(), "Failed to commit cache");487 };488 489 FileCache Cache;490 if (!CacheDir.empty())491 Cache = check(localCache("ThinLTO", "Thin", CacheDir, AddBuffer),492 "failed to create cache");493 494 check(Lto.run(AddStream, Cache), "LTO::run failed");495 return static_cast<int>(HasErrors);496}497 498static int dumpSymtab(int argc, char **argv) {499 for (StringRef F : make_range(argv + 1, argv + argc)) {500 std::unique_ptr<MemoryBuffer> MB =501 check(MemoryBuffer::getFile(F), std::string(F));502 BitcodeFileContents BFC =503 check(getBitcodeFileContents(*MB), std::string(F));504 505 if (BFC.Symtab.size() >= sizeof(irsymtab::storage::Header)) {506 auto *Hdr = reinterpret_cast<const irsymtab::storage::Header *>(507 BFC.Symtab.data());508 outs() << "version: " << Hdr->Version << '\n';509 if (Hdr->Version == irsymtab::storage::Header::kCurrentVersion)510 outs() << "producer: " << Hdr->Producer.get(BFC.StrtabForSymtab)511 << '\n';512 }513 514 std::unique_ptr<InputFile> Input =515 check(InputFile::create(MB->getMemBufferRef()), std::string(F));516 517 outs() << "target triple: " << Input->getTargetTriple() << '\n';518 Triple TT(Input->getTargetTriple());519 520 outs() << "source filename: " << Input->getSourceFileName() << '\n';521 522 if (TT.isOSBinFormatCOFF())523 outs() << "linker opts: " << Input->getCOFFLinkerOpts() << '\n';524 525 if (TT.isOSBinFormatELF()) {526 outs() << "dependent libraries:";527 for (auto L : Input->getDependentLibraries())528 outs() << " \"" << L << "\"";529 outs() << '\n';530 }531 532 ArrayRef<std::pair<StringRef, Comdat::SelectionKind>> ComdatTable =533 Input->getComdatTable();534 for (const InputFile::Symbol &Sym : Input->symbols()) {535 switch (Sym.getVisibility()) {536 case GlobalValue::HiddenVisibility:537 outs() << 'H';538 break;539 case GlobalValue::ProtectedVisibility:540 outs() << 'P';541 break;542 case GlobalValue::DefaultVisibility:543 outs() << 'D';544 break;545 }546 547 auto PrintBool = [&](char C, bool B) { outs() << (B ? C : '-'); };548 PrintBool('U', Sym.isUndefined());549 PrintBool('C', Sym.isCommon());550 PrintBool('W', Sym.isWeak());551 PrintBool('I', Sym.isIndirect());552 PrintBool('O', Sym.canBeOmittedFromSymbolTable());553 PrintBool('T', Sym.isTLS());554 PrintBool('X', Sym.isExecutable());555 outs() << ' ' << Sym.getName() << '\n';556 557 if (Sym.isCommon())558 outs() << " size " << Sym.getCommonSize() << " align "559 << Sym.getCommonAlignment() << '\n';560 561 int Comdat = Sym.getComdatIndex();562 if (Comdat != -1) {563 outs() << " comdat ";564 switch (ComdatTable[Comdat].second) {565 case Comdat::Any:566 outs() << "any";567 break;568 case Comdat::ExactMatch:569 outs() << "exactmatch";570 break;571 case Comdat::Largest:572 outs() << "largest";573 break;574 case Comdat::NoDeduplicate:575 outs() << "nodeduplicate";576 break;577 case Comdat::SameSize:578 outs() << "samesize";579 break;580 }581 outs() << ' ' << ComdatTable[Comdat].first << '\n';582 }583 584 if (TT.isOSBinFormatCOFF() && Sym.isWeak() && Sym.isIndirect())585 outs() << " fallback " << Sym.getCOFFWeakExternalFallback()586 << '\n';587 588 if (!Sym.getSectionName().empty())589 outs() << " section " << Sym.getSectionName() << "\n";590 }591 592 outs() << '\n';593 }594 595 return 0;596}597 598int main(int argc, char **argv) {599 InitLLVM X(argc, argv);600 InitializeAllTargets();601 InitializeAllTargetMCs();602 InitializeAllAsmPrinters();603 InitializeAllAsmParsers();604 605 // FIXME: This should use llvm::cl subcommands, but it isn't currently606 // possible to pass an argument not associated with a subcommand to a607 // subcommand (e.g. -use-new-pm).608 if (argc < 2)609 return usage();610 611 StringRef Subcommand = argv[1];612 // Ensure that argv[0] is correct after adjusting argv/argc.613 argv[1] = argv[0];614 if (Subcommand == "dump-symtab")615 return dumpSymtab(argc - 1, argv + 1);616 if (Subcommand == "run")617 return run(argc - 1, argv + 1);618 if (Subcommand == "print-guid" && argc > 2) {619 // Note the name of the function we're calling: this won't return the right620 // answer for internal linkage symbols.621 outs() << GlobalValue::getGUIDAssumingExternalLinkage(argv[2]) << '\n';622 return 0;623 }624 if (Subcommand == "--version") {625 cl::PrintVersionMessage();626 return 0;627 }628 return usage();629}630