lld/wasm/Driver.cpp

   1 //===- Driver.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 "lld/Common/Driver.h"
  10 #include "Config.h"
  11 #include "InputChunks.h"
  12 #include "InputElement.h"
  13 #include "MarkLive.h"
  14 #include "SymbolTable.h"
  15 #include "Writer.h"
  16 #include "lld/Common/Args.h"
  17 #include "lld/Common/CommonLinkerContext.h"
  18 #include "lld/Common/ErrorHandler.h"
  19 #include "lld/Common/Filesystem.h"
  20 #include "lld/Common/Memory.h"
  21 #include "lld/Common/Reproduce.h"
  22 #include "lld/Common/Strings.h"
  23 #include "lld/Common/Version.h"
  24 #include "llvm/ADT/Twine.h"
  25 #include "llvm/Config/llvm-config.h"
  26 #include "llvm/Object/Wasm.h"
  27 #include "llvm/Option/Arg.h"
  28 #include "llvm/Option/ArgList.h"
  29 #include "llvm/Support/CommandLine.h"
  30 #include "llvm/Support/Parallel.h"
  31 #include "llvm/Support/Path.h"
  32 #include "llvm/Support/Process.h"
  33 #include "llvm/Support/TarWriter.h"
  34 #include "llvm/Support/TargetSelect.h"
  35 #include "llvm/TargetParser/Host.h"
  36 #include <optional>
  37
  38 #define DEBUG_TYPE "lld"
  39
  40 using namespace llvm;
  41 using namespace llvm::object;
  42 using namespace llvm::opt;
  43 using namespace llvm::sys;
  44 using namespace llvm::wasm;
  45
  46 namespace lld::wasm {
  47 Configuration *config;
  48
  49 namespace {
  50
  51 // Create enum with OPT_xxx values for each option in Options.td
  52 enum {
  53   OPT_INVALID = 0,
  54 #define OPTION(...) LLVM_MAKE_OPT_ID(__VA_ARGS__),
  55 #include "Options.inc"
  56 #undef OPTION
  57 };
  58
  59 // This function is called on startup. We need this for LTO since
  60 // LTO calls LLVM functions to compile bitcode files to native code.
  61 // Technically this can be delayed until we read bitcode files, but
  62 // we don't bother to do lazily because the initialization is fast.
  63 static void initLLVM() {
  64   InitializeAllTargets();
  65   InitializeAllTargetMCs();
  66   InitializeAllAsmPrinters();
  67   InitializeAllAsmParsers();
  68 }
  69
  70 class LinkerDriver {
  71 public:
  72   void linkerMain(ArrayRef<const char *> argsArr);
  73
  74 private:
  75   void createFiles(opt::InputArgList &args);
  76   void addFile(StringRef path);
  77   void addLibrary(StringRef name);
  78
  79   // True if we are in --whole-archive and --no-whole-archive.
  80   bool inWholeArchive = false;
  81
  82   std::vector<InputFile *> files;
  83 };
  84 } // anonymous namespace
  85
  86 bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
  87           llvm::raw_ostream &stderrOS, bool exitEarly, bool disableOutput) {
  88   // This driver-specific context will be freed later by unsafeLldMain().
  89   auto *ctx = new CommonLinkerContext;
  90
  91   ctx->e.initialize(stdoutOS, stderrOS, exitEarly, disableOutput);
  92   ctx->e.logName = args::getFilenameWithoutExe(args[0]);
  93   ctx->e.errorLimitExceededMsg = "too many errors emitted, stopping now (use "
  94                                  "-error-limit=0 to see all errors)";
  95
  96   config = make<Configuration>();
  97   symtab = make<SymbolTable>();
  98
  99   initLLVM();
 100   LinkerDriver().linkerMain(args);
 101
 102   return errorCount() == 0;
 103 }
 104
 105 // Create prefix string literals used in Options.td
 106 #define PREFIX(NAME, VALUE)                                                    \
 107   static constexpr StringLiteral NAME##_init[] = VALUE;                        \
 108   static constexpr ArrayRef<StringLiteral> NAME(NAME##_init,                   \
 109                                                 std::size(NAME##_init) - 1);
 110 #include "Options.inc"
 111 #undef PREFIX
 112
 113 // Create table mapping all options defined in Options.td
 114 static constexpr opt::OptTable::Info optInfo[] = {
 115 #define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS,         \
 116                VISIBILITY, PARAM, HELPTEXT, METAVAR, VALUES)                   \
 117   {PREFIX,      NAME,        HELPTEXT,                                         \
 118    METAVAR,     OPT_##ID,    opt::Option::KIND##Class,                         \
 119    PARAM,       FLAGS,       VISIBILITY,                                       \
 120    OPT_##GROUP, OPT_##ALIAS, ALIASARGS,                                        \
 121    VALUES},
 122 #include "Options.inc"
 123 #undef OPTION
 124 };
 125
 126 namespace {
 127 class WasmOptTable : public opt::GenericOptTable {
 128 public:
 129   WasmOptTable() : opt::GenericOptTable(optInfo) {}
 130   opt::InputArgList parse(ArrayRef<const char *> argv);
 131 };
 132 } // namespace
 133
 134 // Set color diagnostics according to -color-diagnostics={auto,always,never}
 135 // or -no-color-diagnostics flags.
 136 static void handleColorDiagnostics(opt::InputArgList &args) {
 137   auto *arg = args.getLastArg(OPT_color_diagnostics, OPT_color_diagnostics_eq,
 138                               OPT_no_color_diagnostics);
 139   if (!arg)
 140     return;
 141   if (arg->getOption().getID() == OPT_color_diagnostics) {
 142     lld::errs().enable_colors(true);
 143   } else if (arg->getOption().getID() == OPT_no_color_diagnostics) {
 144     lld::errs().enable_colors(false);
 145   } else {
 146     StringRef s = arg->getValue();
 147     if (s == "always")
 148       lld::errs().enable_colors(true);
 149     else if (s == "never")
 150       lld::errs().enable_colors(false);
 151     else if (s != "auto")
 152       error("unknown option: --color-diagnostics=" + s);
 153   }
 154 }
 155
 156 static cl::TokenizerCallback getQuotingStyle(opt::InputArgList &args) {
 157   if (auto *arg = args.getLastArg(OPT_rsp_quoting)) {
 158     StringRef s = arg->getValue();
 159     if (s != "windows" && s != "posix")
 160       error("invalid response file quoting: " + s);
 161     if (s == "windows")
 162       return cl::TokenizeWindowsCommandLine;
 163     return cl::TokenizeGNUCommandLine;
 164   }
 165   if (Triple(sys::getProcessTriple()).isOSWindows())
 166     return cl::TokenizeWindowsCommandLine;
 167   return cl::TokenizeGNUCommandLine;
 168 }
 169
 170 // Find a file by concatenating given paths.
 171 static std::optional<std::string> findFile(StringRef path1,
 172                                            const Twine &path2) {
 173   SmallString<128> s;
 174   path::append(s, path1, path2);
 175   if (fs::exists(s))
 176     return std::string(s);
 177   return std::nullopt;
 178 }
 179
 180 opt::InputArgList WasmOptTable::parse(ArrayRef<const char *> argv) {
 181   SmallVector<const char *, 256> vec(argv.data(), argv.data() + argv.size());
 182
 183   unsigned missingIndex;
 184   unsigned missingCount;
 185
 186   // We need to get the quoting style for response files before parsing all
 187   // options so we parse here before and ignore all the options but
 188   // --rsp-quoting.
 189   opt::InputArgList args = this->ParseArgs(vec, missingIndex, missingCount);
 190
 191   // Expand response files (arguments in the form of @<filename>)
 192   // and then parse the argument again.
 193   cl::ExpandResponseFiles(saver(), getQuotingStyle(args), vec);
 194   args = this->ParseArgs(vec, missingIndex, missingCount);
 195
 196   handleColorDiagnostics(args);
 197   if (missingCount)
 198     error(Twine(args.getArgString(missingIndex)) + ": missing argument");
 199
 200   for (auto *arg : args.filtered(OPT_UNKNOWN))
 201     error("unknown argument: " + arg->getAsString(args));
 202   return args;
 203 }
 204
 205 // Currently we allow a ".imports" to live alongside a library. This can
 206 // be used to specify a list of symbols which can be undefined at link
 207 // time (imported from the environment.  For example libc.a include an
 208 // import file that lists the syscall functions it relies on at runtime.
 209 // In the long run this information would be better stored as a symbol
 210 // attribute/flag in the object file itself.
 211 // See: https://github.com/WebAssembly/tool-conventions/issues/35
 212 static void readImportFile(StringRef filename) {
 213   if (std::optional<MemoryBufferRef> buf = readFile(filename))
 214     for (StringRef sym : args::getLines(*buf))
 215       config->allowUndefinedSymbols.insert(sym);
 216 }
 217
 218 // Returns slices of MB by parsing MB as an archive file.
 219 // Each slice consists of a member file in the archive.
 220 std::vector<MemoryBufferRef> static getArchiveMembers(MemoryBufferRef mb) {
 221   std::unique_ptr<Archive> file =
 222       CHECK(Archive::create(mb),
 223             mb.getBufferIdentifier() + ": failed to parse archive");
 224
 225   std::vector<MemoryBufferRef> v;
 226   Error err = Error::success();
 227   for (const Archive::Child &c : file->children(err)) {
 228     MemoryBufferRef mbref =
 229         CHECK(c.getMemoryBufferRef(),
 230               mb.getBufferIdentifier() +
 231                   ": could not get the buffer for a child of the archive");
 232     v.push_back(mbref);
 233   }
 234   if (err)
 235     fatal(mb.getBufferIdentifier() +
 236           ": Archive::children failed: " + toString(std::move(err)));
 237
 238   // Take ownership of memory buffers created for members of thin archives.
 239   for (std::unique_ptr<MemoryBuffer> &mb : file->takeThinBuffers())
 240     make<std::unique_ptr<MemoryBuffer>>(std::move(mb));
 241
 242   return v;
 243 }
 244
 245 void LinkerDriver::addFile(StringRef path) {
 246   std::optional<MemoryBufferRef> buffer = readFile(path);
 247   if (!buffer)
 248     return;
 249   MemoryBufferRef mbref = *buffer;
 250
 251   switch (identify_magic(mbref.getBuffer())) {
 252   case file_magic::archive: {
 253     SmallString<128> importFile = path;
 254     path::replace_extension(importFile, ".imports");
 255     if (fs::exists(importFile))
 256       readImportFile(importFile.str());
 257
 258     // Handle -whole-archive.
 259     if (inWholeArchive) {
 260       for (MemoryBufferRef &m : getArchiveMembers(mbref)) {
 261         auto *object = createObjectFile(m, path);
 262         // Mark object as live; object members are normally not
 263         // live by default but -whole-archive is designed to treat
 264         // them as such.
 265         object->markLive();
 266         files.push_back(object);
 267       }
 268
 269       return;
 270     }
 271
 272     std::unique_ptr<Archive> file =
 273         CHECK(Archive::create(mbref), path + ": failed to parse archive");
 274
 275     if (!file->isEmpty() && !file->hasSymbolTable()) {
 276       error(mbref.getBufferIdentifier() +
 277             ": archive has no index; run ranlib to add one");
 278     }
 279
 280     files.push_back(make<ArchiveFile>(mbref));
 281     return;
 282   }
 283   case file_magic::bitcode:
 284   case file_magic::wasm_object:
 285     files.push_back(createObjectFile(mbref));
 286     break;
 287   case file_magic::unknown:
 288     if (mbref.getBuffer().starts_with("#STUB")) {
 289       files.push_back(make<StubFile>(mbref));
 290       break;
 291     }
 292     [[fallthrough]];
 293   default:
 294     error("unknown file type: " + mbref.getBufferIdentifier());
 295   }
 296 }
 297
 298 static std::optional<std::string> findFromSearchPaths(StringRef path) {
 299   for (StringRef dir : config->searchPaths)
 300     if (std::optional<std::string> s = findFile(dir, path))
 301       return s;
 302   return std::nullopt;
 303 }
 304
 305 // This is for -l<basename>. We'll look for lib<basename>.a from
 306 // search paths.
 307 static std::optional<std::string> searchLibraryBaseName(StringRef name) {
 308   for (StringRef dir : config->searchPaths) {
 309     // Currently we don't enable dynamic linking at all unless -shared or -pie
 310     // are used, so don't even look for .so files in that case..
 311     if (config->isPic && !config->isStatic)
 312       if (std::optional<std::string> s = findFile(dir, "lib" + name + ".so"))
 313         return s;
 314     if (std::optional<std::string> s = findFile(dir, "lib" + name + ".a"))
 315       return s;
 316   }
 317   return std::nullopt;
 318 }
 319
 320 // This is for -l<namespec>.
 321 static std::optional<std::string> searchLibrary(StringRef name) {
 322   if (name.starts_with(":"))
 323     return findFromSearchPaths(name.substr(1));
 324   return searchLibraryBaseName(name);
 325 }
 326
 327 // Add a given library by searching it from input search paths.
 328 void LinkerDriver::addLibrary(StringRef name) {
 329   if (std::optional<std::string> path = searchLibrary(name))
 330     addFile(saver().save(*path));
 331   else
 332     error("unable to find library -l" + name, ErrorTag::LibNotFound, {name});
 333 }
 334
 335 void LinkerDriver::createFiles(opt::InputArgList &args) {
 336   for (auto *arg : args) {
 337     switch (arg->getOption().getID()) {
 338     case OPT_library:
 339       addLibrary(arg->getValue());
 340       break;
 341     case OPT_INPUT:
 342       addFile(arg->getValue());
 343       break;
 344     case OPT_Bstatic:
 345       config->isStatic = true;
 346       break;
 347     case OPT_Bdynamic:
 348       config->isStatic = false;
 349       break;
 350     case OPT_whole_archive:
 351       inWholeArchive = true;
 352       break;
 353     case OPT_no_whole_archive:
 354       inWholeArchive = false;
 355       break;
 356     }
 357   }
 358   if (files.empty() && errorCount() == 0)
 359     error("no input files");
 360 }
 361
 362 static StringRef getEntry(opt::InputArgList &args) {
 363   auto *arg = args.getLastArg(OPT_entry, OPT_no_entry);
 364   if (!arg) {
 365     if (args.hasArg(OPT_relocatable))
 366       return "";
 367     if (args.hasArg(OPT_shared))
 368       return "__wasm_call_ctors";
 369     return "_start";
 370   }
 371   if (arg->getOption().getID() == OPT_no_entry)
 372     return "";
 373   return arg->getValue();
 374 }
 375
 376 // Determines what we should do if there are remaining unresolved
 377 // symbols after the name resolution.
 378 static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &args) {
 379   UnresolvedPolicy errorOrWarn = args.hasFlag(OPT_error_unresolved_symbols,
 380                                               OPT_warn_unresolved_symbols, true)
 381                                      ? UnresolvedPolicy::ReportError
 382                                      : UnresolvedPolicy::Warn;
 383
 384   if (auto *arg = args.getLastArg(OPT_unresolved_symbols)) {
 385     StringRef s = arg->getValue();
 386     if (s == "ignore-all")
 387       return UnresolvedPolicy::Ignore;
 388     if (s == "import-dynamic")
 389       return UnresolvedPolicy::ImportDynamic;
 390     if (s == "report-all")
 391       return errorOrWarn;
 392     error("unknown --unresolved-symbols value: " + s);
 393   }
 394
 395   return errorOrWarn;
 396 }
 397
 398 // Parse --build-id or --build-id=<style>. We handle "tree" as a
 399 // synonym for "sha1" because all our hash functions including
 400 // -build-id=sha1 are actually tree hashes for performance reasons.
 401 static std::pair<BuildIdKind, SmallVector<uint8_t, 0>>
 402 getBuildId(opt::InputArgList &args) {
 403   auto *arg = args.getLastArg(OPT_build_id, OPT_build_id_eq);
 404   if (!arg)
 405     return {BuildIdKind::None, {}};
 406
 407   if (arg->getOption().getID() == OPT_build_id)
 408     return {BuildIdKind::Fast, {}};
 409
 410   StringRef s = arg->getValue();
 411   if (s == "fast")
 412     return {BuildIdKind::Fast, {}};
 413   if (s == "sha1" || s == "tree")
 414     return {BuildIdKind::Sha1, {}};
 415   if (s == "uuid")
 416     return {BuildIdKind::Uuid, {}};
 417   if (s.starts_with("0x"))
 418     return {BuildIdKind::Hexstring, parseHex(s.substr(2))};
 419
 420   if (s != "none")
 421     error("unknown --build-id style: " + s);
 422   return {BuildIdKind::None, {}};
 423 }
 424
 425 // Initializes Config members by the command line options.
 426 static void readConfigs(opt::InputArgList &args) {
 427   config->bsymbolic = args.hasArg(OPT_Bsymbolic);
 428   config->checkFeatures =
 429       args.hasFlag(OPT_check_features, OPT_no_check_features, true);
 430   config->compressRelocations = args.hasArg(OPT_compress_relocations);
 431   config->demangle = args.hasFlag(OPT_demangle, OPT_no_demangle, true);
 432   config->disableVerify = args.hasArg(OPT_disable_verify);
 433   config->emitRelocs = args.hasArg(OPT_emit_relocs);
 434   config->experimentalPic = args.hasArg(OPT_experimental_pic);
 435   config->entry = getEntry(args);
 436   config->exportAll = args.hasArg(OPT_export_all);
 437   config->exportTable = args.hasArg(OPT_export_table);
 438   config->growableTable = args.hasArg(OPT_growable_table);
 439
 440   if (args.hasArg(OPT_import_memory_with_name)) {
 441     config->memoryImport =
 442         args.getLastArgValue(OPT_import_memory_with_name).split(",");
 443   } else if (args.hasArg(OPT_import_memory)) {
 444     config->memoryImport =
 445         std::pair<llvm::StringRef, llvm::StringRef>(defaultModule, memoryName);
 446   } else {
 447     config->memoryImport =
 448         std::optional<std::pair<llvm::StringRef, llvm::StringRef>>();
 449   }
 450
 451   if (args.hasArg(OPT_export_memory_with_name)) {
 452     config->memoryExport =
 453         args.getLastArgValue(OPT_export_memory_with_name);
 454   } else if (args.hasArg(OPT_export_memory)) {
 455     config->memoryExport = memoryName;
 456   } else {
 457     config->memoryExport = std::optional<llvm::StringRef>();
 458   }
 459
 460   config->sharedMemory = args.hasArg(OPT_shared_memory);
 461   config->soName = args.getLastArgValue(OPT_soname);
 462   config->importTable = args.hasArg(OPT_import_table);
 463   config->importUndefined = args.hasArg(OPT_import_undefined);
 464   config->ltoo = args::getInteger(args, OPT_lto_O, 2);
 465   if (config->ltoo > 3)
 466     error("invalid optimization level for LTO: " + Twine(config->ltoo));
 467   unsigned ltoCgo =
 468       args::getInteger(args, OPT_lto_CGO, args::getCGOptLevel(config->ltoo));
 469   if (auto level = CodeGenOpt::getLevel(ltoCgo))
 470     config->ltoCgo = *level;
 471   else
 472     error("invalid codegen optimization level for LTO: " + Twine(ltoCgo));
 473   config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
 474   config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
 475   config->mapFile = args.getLastArgValue(OPT_Map);
 476   config->optimize = args::getInteger(args, OPT_O, 1);
 477   config->outputFile = args.getLastArgValue(OPT_o);
 478   config->relocatable = args.hasArg(OPT_relocatable);
 479   config->gcSections =
 480       args.hasFlag(OPT_gc_sections, OPT_no_gc_sections, !config->relocatable);
 481   config->mergeDataSegments =
 482       args.hasFlag(OPT_merge_data_segments, OPT_no_merge_data_segments,
 483                    !config->relocatable);
 484   config->pie = args.hasFlag(OPT_pie, OPT_no_pie, false);
 485   config->printGcSections =
 486       args.hasFlag(OPT_print_gc_sections, OPT_no_print_gc_sections, false);
 487   config->saveTemps = args.hasArg(OPT_save_temps);
 488   config->searchPaths = args::getStrings(args, OPT_library_path);
 489   config->shared = args.hasArg(OPT_shared);
 490   config->stripAll = args.hasArg(OPT_strip_all);
 491   config->stripDebug = args.hasArg(OPT_strip_debug);
 492   config->stackFirst = args.hasArg(OPT_stack_first);
 493   config->trace = args.hasArg(OPT_trace);
 494   config->thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
 495   config->thinLTOCachePolicy = CHECK(
 496       parseCachePruningPolicy(args.getLastArgValue(OPT_thinlto_cache_policy)),
 497       "--thinlto-cache-policy: invalid cache policy");
 498   config->unresolvedSymbols = getUnresolvedSymbolPolicy(args);
 499   config->whyExtract = args.getLastArgValue(OPT_why_extract);
 500   errorHandler().verbose = args.hasArg(OPT_verbose);
 501   LLVM_DEBUG(errorHandler().verbose = true);
 502
 503   config->initialMemory = args::getInteger(args, OPT_initial_memory, 0);
 504   config->globalBase = args::getInteger(args, OPT_global_base, 0);
 505   config->tableBase = args::getInteger(args, OPT_table_base, 0);
 506   config->maxMemory = args::getInteger(args, OPT_max_memory, 0);
 507   config->zStackSize =
 508       args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize);
 509
 510   // Default value of exportDynamic depends on `-shared`
 511   config->exportDynamic =
 512       args.hasFlag(OPT_export_dynamic, OPT_no_export_dynamic, config->shared);
 513
 514   // Parse wasm32/64.
 515   if (auto *arg = args.getLastArg(OPT_m)) {
 516     StringRef s = arg->getValue();
 517     if (s == "wasm32")
 518       config->is64 = false;
 519     else if (s == "wasm64")
 520       config->is64 = true;
 521     else
 522       error("invalid target architecture: " + s);
 523   }
 524
 525   // --threads= takes a positive integer and provides the default value for
 526   // --thinlto-jobs=.
 527   if (auto *arg = args.getLastArg(OPT_threads)) {
 528     StringRef v(arg->getValue());
 529     unsigned threads = 0;
 530     if (!llvm::to_integer(v, threads, 0) || threads == 0)
 531       error(arg->getSpelling() + ": expected a positive integer, but got '" +
 532             arg->getValue() + "'");
 533     parallel::strategy = hardware_concurrency(threads);
 534     config->thinLTOJobs = v;
 535   }
 536   if (auto *arg = args.getLastArg(OPT_thinlto_jobs))
 537     config->thinLTOJobs = arg->getValue();
 538
 539   if (auto *arg = args.getLastArg(OPT_features)) {
 540     config->features =
 541         std::optional<std::vector<std::string>>(std::vector<std::string>());
 542     for (StringRef s : arg->getValues())
 543       config->features->push_back(std::string(s));
 544   }
 545
 546   if (auto *arg = args.getLastArg(OPT_extra_features)) {
 547     config->extraFeatures =
 548         std::optional<std::vector<std::string>>(std::vector<std::string>());
 549     for (StringRef s : arg->getValues())
 550       config->extraFeatures->push_back(std::string(s));
 551   }
 552
 553   // Legacy --allow-undefined flag which is equivalent to
 554   // --unresolve-symbols=ignore + --import-undefined
 555   if (args.hasArg(OPT_allow_undefined)) {
 556     config->importUndefined = true;
 557     config->unresolvedSymbols = UnresolvedPolicy::Ignore;
 558   }
 559
 560   if (args.hasArg(OPT_print_map))
 561     config->mapFile = "-";
 562
 563   std::tie(config->buildId, config->buildIdVector) = getBuildId(args);
 564 }
 565
 566 // Some Config members do not directly correspond to any particular
 567 // command line options, but computed based on other Config values.
 568 // This function initialize such members. See Config.h for the details
 569 // of these values.
 570 static void setConfigs() {
 571   config->isPic = config->pie || config->shared;
 572
 573   if (config->isPic) {
 574     if (config->exportTable)
 575       error("-shared/-pie is incompatible with --export-table");
 576     config->importTable = true;
 577   } else {
 578     // Default table base.  Defaults to 1, reserving 0 for the NULL function
 579     // pointer.
 580     if (!config->tableBase)
 581       config->tableBase = 1;
 582     // The default offset for static/global data, for when --global-base is
 583     // not specified on the command line.  The precise value of 1024 is
 584     // somewhat arbitrary, and pre-dates wasm-ld (Its the value that
 585     // emscripten used prior to wasm-ld).
 586     if (!config->globalBase && !config->relocatable && !config->stackFirst)
 587       config->globalBase = 1024;
 588   }
 589
 590   if (config->relocatable) {
 591     if (config->exportTable)
 592       error("--relocatable is incompatible with --export-table");
 593     if (config->growableTable)
 594       error("--relocatable is incompatible with --growable-table");
 595     // Ignore any --import-table, as it's redundant.
 596     config->importTable = true;
 597   }
 598
 599   if (config->shared) {
 600     if (config->memoryExport.has_value()) {
 601       error("--export-memory is incompatible with --shared");
 602     }
 603     if (!config->memoryImport.has_value()) {
 604       config->memoryImport =
 605           std::pair<llvm::StringRef, llvm::StringRef>(defaultModule, memoryName);
 606     }
 607     config->importUndefined = true;
 608   }
 609
 610   // If neither export-memory nor import-memory is specified, default to
 611   // exporting memory under its default name.
 612   if (!config->memoryExport.has_value() && !config->memoryImport.has_value()) {
 613     config->memoryExport = memoryName;
 614   }
 615 }
 616
 617 // Some command line options or some combinations of them are not allowed.
 618 // This function checks for such errors.
 619 static void checkOptions(opt::InputArgList &args) {
 620   if (!config->stripDebug && !config->stripAll && config->compressRelocations)
 621     error("--compress-relocations is incompatible with output debug"
 622           " information. Please pass --strip-debug or --strip-all");
 623
 624   if (config->ltoPartitions == 0)
 625     error("--lto-partitions: number of threads must be > 0");
 626   if (!get_threadpool_strategy(config->thinLTOJobs))
 627     error("--thinlto-jobs: invalid job count: " + config->thinLTOJobs);
 628
 629   if (config->pie && config->shared)
 630     error("-shared and -pie may not be used together");
 631
 632   if (config->outputFile.empty())
 633     error("no output file specified");
 634
 635   if (config->importTable && config->exportTable)
 636     error("--import-table and --export-table may not be used together");
 637
 638   if (config->relocatable) {
 639     if (!config->entry.empty())
 640       error("entry point specified for relocatable output file");
 641     if (config->gcSections)
 642       error("-r and --gc-sections may not be used together");
 643     if (config->compressRelocations)
 644       error("-r -and --compress-relocations may not be used together");
 645     if (args.hasArg(OPT_undefined))
 646       error("-r -and --undefined may not be used together");
 647     if (config->pie)
 648       error("-r and -pie may not be used together");
 649     if (config->sharedMemory)
 650       error("-r and --shared-memory may not be used together");
 651     if (config->globalBase)
 652       error("-r and --global-base may not by used together");
 653   }
 654
 655   // To begin to prepare for Module Linking-style shared libraries, start
 656   // warning about uses of `-shared` and related flags outside of Experimental
 657   // mode, to give anyone using them a heads-up that they will be changing.
 658   //
 659   // Also, warn about flags which request explicit exports.
 660   if (!config->experimentalPic) {
 661     // -shared will change meaning when Module Linking is implemented.
 662     if (config->shared) {
 663       warn("creating shared libraries, with -shared, is not yet stable");
 664     }
 665
 666     // -pie will change meaning when Module Linking is implemented.
 667     if (config->pie) {
 668       warn("creating PIEs, with -pie, is not yet stable");
 669     }
 670
 671     if (config->unresolvedSymbols == UnresolvedPolicy::ImportDynamic) {
 672       warn("dynamic imports are not yet stable "
 673            "(--unresolved-symbols=import-dynamic)");
 674     }
 675   }
 676
 677   if (config->bsymbolic && !config->shared) {
 678     warn("-Bsymbolic is only meaningful when combined with -shared");
 679   }
 680
 681   if (config->isPic) {
 682     if (config->globalBase)
 683       error("--global-base may not be used with -shared/-pie");
 684     if (config->tableBase)
 685       error("--table-base may not be used with -shared/-pie");
 686   }
 687 }
 688
 689 static const char *getReproduceOption(opt::InputArgList &args) {
 690   if (auto *arg = args.getLastArg(OPT_reproduce))
 691     return arg->getValue();
 692   return getenv("LLD_REPRODUCE");
 693 }
 694
 695 // Force Sym to be entered in the output. Used for -u or equivalent.
 696 static Symbol *handleUndefined(StringRef name, const char *option) {
 697   Symbol *sym = symtab->find(name);
 698   if (!sym)
 699     return nullptr;
 700
 701   // Since symbol S may not be used inside the program, LTO may
 702   // eliminate it. Mark the symbol as "used" to prevent it.
 703   sym->isUsedInRegularObj = true;
 704
 705   if (auto *lazySym = dyn_cast<LazySymbol>(sym)) {
 706     lazySym->fetch();
 707     if (!config->whyExtract.empty())
 708       config->whyExtractRecords.emplace_back(option, sym->getFile(), *sym);
 709   }
 710
 711   return sym;
 712 }
 713
 714 static void handleLibcall(StringRef name) {
 715   Symbol *sym = symtab->find(name);
 716   if (!sym)
 717     return;
 718
 719   if (auto *lazySym = dyn_cast<LazySymbol>(sym)) {
 720     MemoryBufferRef mb = lazySym->getMemberBuffer();
 721     if (isBitcode(mb)) {
 722       if (!config->whyExtract.empty())
 723         config->whyExtractRecords.emplace_back("<libcall>", sym->getFile(),
 724                                                *sym);
 725       lazySym->fetch();
 726     }
 727   }
 728 }
 729
 730 static void writeWhyExtract() {
 731   if (config->whyExtract.empty())
 732     return;
 733
 734   std::error_code ec;
 735   raw_fd_ostream os(config->whyExtract, ec, sys::fs::OF_None);
 736   if (ec) {
 737     error("cannot open --why-extract= file " + config->whyExtract + ": " +
 738           ec.message());
 739     return;
 740   }
 741
 742   os << "reference\textracted\tsymbol\n";
 743   for (auto &entry : config->whyExtractRecords) {
 744     os << std::get<0>(entry) << '\t' << toString(std::get<1>(entry)) << '\t'
 745        << toString(std::get<2>(entry)) << '\n';
 746   }
 747 }
 748
 749 // Equivalent of demote demoteSharedAndLazySymbols() in the ELF linker
 750 static void demoteLazySymbols() {
 751   for (Symbol *sym : symtab->symbols()) {
 752     if (auto* s = dyn_cast<LazySymbol>(sym)) {
 753       if (s->signature) {
 754         LLVM_DEBUG(llvm::dbgs()
 755                    << "demoting lazy func: " << s->getName() << "\n");
 756         replaceSymbol<UndefinedFunction>(s, s->getName(), std::nullopt,
 757                                          std::nullopt, WASM_SYMBOL_BINDING_WEAK,
 758                                          s->getFile(), s->signature);
 759       }
 760     }
 761   }
 762 }
 763
 764 static UndefinedGlobal *
 765 createUndefinedGlobal(StringRef name, llvm::wasm::WasmGlobalType *type) {
 766   auto *sym = cast<UndefinedGlobal>(symtab->addUndefinedGlobal(
 767       name, std::nullopt, std::nullopt, WASM_SYMBOL_UNDEFINED, nullptr, type));
 768   config->allowUndefinedSymbols.insert(sym->getName());
 769   sym->isUsedInRegularObj = true;
 770   return sym;
 771 }
 772
 773 static InputGlobal *createGlobal(StringRef name, bool isMutable) {
 774   llvm::wasm::WasmGlobal wasmGlobal;
 775   bool is64 = config->is64.value_or(false);
 776   wasmGlobal.Type = {uint8_t(is64 ? WASM_TYPE_I64 : WASM_TYPE_I32), isMutable};
 777   wasmGlobal.InitExpr = intConst(0, is64);
 778   wasmGlobal.SymbolName = name;
 779   return make<InputGlobal>(wasmGlobal, nullptr);
 780 }
 781
 782 static GlobalSymbol *createGlobalVariable(StringRef name, bool isMutable) {
 783   InputGlobal *g = createGlobal(name, isMutable);
 784   return symtab->addSyntheticGlobal(name, WASM_SYMBOL_VISIBILITY_HIDDEN, g);
 785 }
 786
 787 static GlobalSymbol *createOptionalGlobal(StringRef name, bool isMutable) {
 788   InputGlobal *g = createGlobal(name, isMutable);
 789   return symtab->addOptionalGlobalSymbol(name, g);
 790 }
 791
 792 // Create ABI-defined synthetic symbols
 793 static void createSyntheticSymbols() {
 794   if (config->relocatable)
 795     return;
 796
 797   static WasmSignature nullSignature = {{}, {}};
 798   static WasmSignature i32ArgSignature = {{}, {ValType::I32}};
 799   static WasmSignature i64ArgSignature = {{}, {ValType::I64}};
 800   static llvm::wasm::WasmGlobalType globalTypeI32 = {WASM_TYPE_I32, false};
 801   static llvm::wasm::WasmGlobalType globalTypeI64 = {WASM_TYPE_I64, false};
 802   static llvm::wasm::WasmGlobalType mutableGlobalTypeI32 = {WASM_TYPE_I32,
 803                                                             true};
 804   static llvm::wasm::WasmGlobalType mutableGlobalTypeI64 = {WASM_TYPE_I64,
 805                                                             true};
 806   WasmSym::callCtors = symtab->addSyntheticFunction(
 807       "__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
 808       make<SyntheticFunction>(nullSignature, "__wasm_call_ctors"));
 809
 810   bool is64 = config->is64.value_or(false);
 811
 812   if (config->isPic) {
 813     WasmSym::stackPointer =
 814         createUndefinedGlobal("__stack_pointer", config->is64.value_or(false)
 815                                                      ? &mutableGlobalTypeI64
 816                                                      : &mutableGlobalTypeI32);
 817     // For PIC code, we import two global variables (__memory_base and
 818     // __table_base) from the environment and use these as the offset at
 819     // which to load our static data and function table.
 820     // See:
 821     // https://github.com/WebAssembly/tool-conventions/blob/main/DynamicLinking.md
 822     auto *globalType = is64 ? &globalTypeI64 : &globalTypeI32;
 823     WasmSym::memoryBase = createUndefinedGlobal("__memory_base", globalType);
 824     WasmSym::tableBase = createUndefinedGlobal("__table_base", globalType);
 825     WasmSym::memoryBase->markLive();
 826     WasmSym::tableBase->markLive();
 827     if (is64) {
 828       WasmSym::tableBase32 =
 829           createUndefinedGlobal("__table_base32", &globalTypeI32);
 830       WasmSym::tableBase32->markLive();
 831     } else {
 832       WasmSym::tableBase32 = nullptr;
 833     }
 834   } else {
 835     // For non-PIC code
 836     WasmSym::stackPointer = createGlobalVariable("__stack_pointer", true);
 837     WasmSym::stackPointer->markLive();
 838   }
 839
 840   if (config->sharedMemory) {
 841     WasmSym::tlsBase = createGlobalVariable("__tls_base", true);
 842     WasmSym::tlsSize = createGlobalVariable("__tls_size", false);
 843     WasmSym::tlsAlign = createGlobalVariable("__tls_align", false);
 844     WasmSym::initTLS = symtab->addSyntheticFunction(
 845         "__wasm_init_tls", WASM_SYMBOL_VISIBILITY_HIDDEN,
 846         make<SyntheticFunction>(
 847             is64 ? i64ArgSignature : i32ArgSignature,
 848             "__wasm_init_tls"));
 849   }
 850
 851   if (config->isPic ||
 852       config->unresolvedSymbols == UnresolvedPolicy::ImportDynamic) {
 853     // For PIC code, or when dynamically importing addresses, we create
 854     // synthetic functions that apply relocations.  These get called from
 855     // __wasm_call_ctors before the user-level constructors.
 856     WasmSym::applyDataRelocs = symtab->addSyntheticFunction(
 857         "__wasm_apply_data_relocs",
 858         WASM_SYMBOL_VISIBILITY_DEFAULT | WASM_SYMBOL_EXPORTED,
 859         make<SyntheticFunction>(nullSignature, "__wasm_apply_data_relocs"));
 860   }
 861 }
 862
 863 static void createOptionalSymbols() {
 864   if (config->relocatable)
 865     return;
 866
 867   WasmSym::dsoHandle = symtab->addOptionalDataSymbol("__dso_handle");
 868
 869   if (!config->shared)
 870     WasmSym::dataEnd = symtab->addOptionalDataSymbol("__data_end");
 871
 872   if (!config->isPic) {
 873     WasmSym::stackLow = symtab->addOptionalDataSymbol("__stack_low");
 874     WasmSym::stackHigh = symtab->addOptionalDataSymbol("__stack_high");
 875     WasmSym::globalBase = symtab->addOptionalDataSymbol("__global_base");
 876     WasmSym::heapBase = symtab->addOptionalDataSymbol("__heap_base");
 877     WasmSym::heapEnd = symtab->addOptionalDataSymbol("__heap_end");
 878     WasmSym::definedMemoryBase = symtab->addOptionalDataSymbol("__memory_base");
 879     WasmSym::definedTableBase = symtab->addOptionalDataSymbol("__table_base");
 880     if (config->is64.value_or(false))
 881       WasmSym::definedTableBase32 =
 882           symtab->addOptionalDataSymbol("__table_base32");
 883   }
 884
 885   // For non-shared memory programs we still need to define __tls_base since we
 886   // allow object files built with TLS to be linked into single threaded
 887   // programs, and such object files can contain references to this symbol.
 888   //
 889   // However, in this case __tls_base is immutable and points directly to the
 890   // start of the `.tdata` static segment.
 891   //
 892   // __tls_size and __tls_align are not needed in this case since they are only
 893   // needed for __wasm_init_tls (which we do not create in this case).
 894   if (!config->sharedMemory)
 895     WasmSym::tlsBase = createOptionalGlobal("__tls_base", false);
 896 }
 897
 898 static void processStubLibrariesPreLTO() {
 899   log("-- processStubLibrariesPreLTO");
 900   for (auto &stub_file : symtab->stubFiles) {
 901     LLVM_DEBUG(llvm::dbgs()
 902                << "processing stub file: " << stub_file->getName() << "\n");
 903     for (auto [name, deps]: stub_file->symbolDependencies) {
 904       auto* sym = symtab->find(name);
 905       // If the symbol is not present at all (yet), or if it is present but
 906       // undefined, then mark the dependent symbols as used by a regular
 907       // object so they will be preserved and exported by the LTO process.
 908       if (!sym || sym->isUndefined()) {
 909         for (const auto dep : deps) {
 910           auto* needed = symtab->find(dep);
 911           if (needed ) {
 912             needed->isUsedInRegularObj = true;
 913           }
 914         }
 915       }
 916     }
 917   }
 918 }
 919
 920 static void processStubLibraries() {
 921   log("-- processStubLibraries");
 922   bool depsAdded = false;
 923   do {
 924     depsAdded = false;
 925     for (auto &stub_file : symtab->stubFiles) {
 926       LLVM_DEBUG(llvm::dbgs()
 927                  << "processing stub file: " << stub_file->getName() << "\n");
 928       for (auto [name, deps]: stub_file->symbolDependencies) {
 929         auto* sym = symtab->find(name);
 930         if (!sym || !sym->isUndefined()) {
 931           if (sym && sym->traced)
 932             message(toString(stub_file) + ": stub symbol not needed: " + name);
 933           else
 934             LLVM_DEBUG(llvm::dbgs() << "stub symbol not needed: `" << name << "`\n");
 935           continue;
 936         }
 937         // The first stub library to define a given symbol sets this and
 938         // definitions in later stub libraries are ignored.
 939         if (sym->forceImport)
 940           continue;  // Already handled
 941         sym->forceImport = true;
 942         if (sym->traced)
 943           message(toString(stub_file) + ": importing " + name);
 944         else
 945           LLVM_DEBUG(llvm::dbgs()
 946                      << toString(stub_file) << ": importing " << name << "\n");
 947         for (const auto dep : deps) {
 948           auto* needed = symtab->find(dep);
 949           if (!needed) {
 950             error(toString(stub_file) + ": undefined symbol: " + dep +
 951                   ". Required by " + toString(*sym));
 952           } else if (needed->isUndefined()) {
 953             error(toString(stub_file) +
 954                   ": undefined symbol: " + toString(*needed) +
 955                   ". Required by " + toString(*sym));
 956           } else {
 957             if (needed->traced)
 958               message(toString(stub_file) + ": exported " + toString(*needed) +
 959                       " due to import of " + name);
 960             else
 961               LLVM_DEBUG(llvm::dbgs()
 962                          << "force export: " << toString(*needed) << "\n");
 963             needed->forceExport = true;
 964             if (auto *lazy = dyn_cast<LazySymbol>(needed)) {
 965               depsAdded = true;
 966               lazy->fetch();
 967               if (!config->whyExtract.empty())
 968                 config->whyExtractRecords.emplace_back(stub_file->getName(),
 969                                                        sym->getFile(), *sym);
 970             }
 971           }
 972         }
 973       }
 974     }
 975   } while (depsAdded);
 976
 977   log("-- done processStubLibraries");
 978 }
 979
 980 // Reconstructs command line arguments so that so that you can re-run
 981 // the same command with the same inputs. This is for --reproduce.
 982 static std::string createResponseFile(const opt::InputArgList &args) {
 983   SmallString<0> data;
 984   raw_svector_ostream os(data);
 985
 986   // Copy the command line to the output while rewriting paths.
 987   for (auto *arg : args) {
 988     switch (arg->getOption().getID()) {
 989     case OPT_reproduce:
 990       break;
 991     case OPT_INPUT:
 992       os << quote(relativeToRoot(arg->getValue())) << "\n";
 993       break;
 994     case OPT_o:
 995       // If -o path contains directories, "lld @response.txt" will likely
 996       // fail because the archive we are creating doesn't contain empty
 997       // directories for the output path (-o doesn't create directories).
 998       // Strip directories to prevent the issue.
 999       os << "-o " << quote(sys::path::filename(arg->getValue())) << "\n";
1000       break;
1001     default:
1002       os << toString(*arg) << "\n";
1003     }
1004   }
1005   return std::string(data.str());
1006 }
1007
1008 // The --wrap option is a feature to rename symbols so that you can write
1009 // wrappers for existing functions. If you pass `-wrap=foo`, all
1010 // occurrences of symbol `foo` are resolved to `wrap_foo` (so, you are
1011 // expected to write `wrap_foo` function as a wrapper). The original
1012 // symbol becomes accessible as `real_foo`, so you can call that from your
1013 // wrapper.
1014 //
1015 // This data structure is instantiated for each -wrap option.
1016 struct WrappedSymbol {
1017   Symbol *sym;
1018   Symbol *real;
1019   Symbol *wrap;
1020 };
1021
1022 static Symbol *addUndefined(StringRef name) {
1023   return symtab->addUndefinedFunction(name, std::nullopt, std::nullopt,
1024                                       WASM_SYMBOL_UNDEFINED, nullptr, nullptr,
1025                                       false);
1026 }
1027
1028 // Handles -wrap option.
1029 //
1030 // This function instantiates wrapper symbols. At this point, they seem
1031 // like they are not being used at all, so we explicitly set some flags so
1032 // that LTO won't eliminate them.
1033 static std::vector<WrappedSymbol> addWrappedSymbols(opt::InputArgList &args) {
1034   std::vector<WrappedSymbol> v;
1035   DenseSet<StringRef> seen;
1036
1037   for (auto *arg : args.filtered(OPT_wrap)) {
1038     StringRef name = arg->getValue();
1039     if (!seen.insert(name).second)
1040       continue;
1041
1042     Symbol *sym = symtab->find(name);
1043     if (!sym)
1044       continue;
1045
1046     Symbol *real = addUndefined(saver().save("__real_" + name));
1047     Symbol *wrap = addUndefined(saver().save("__wrap_" + name));
1048     v.push_back({sym, real, wrap});
1049
1050     // We want to tell LTO not to inline symbols to be overwritten
1051     // because LTO doesn't know the final symbol contents after renaming.
1052     real->canInline = false;
1053     sym->canInline = false;
1054
1055     // Tell LTO not to eliminate these symbols.
1056     sym->isUsedInRegularObj = true;
1057     wrap->isUsedInRegularObj = true;
1058     real->isUsedInRegularObj = false;
1059   }
1060   return v;
1061 }
1062
1063 // Do renaming for -wrap by updating pointers to symbols.
1064 //
1065 // When this function is executed, only InputFiles and symbol table
1066 // contain pointers to symbol objects. We visit them to replace pointers,
1067 // so that wrapped symbols are swapped as instructed by the command line.
1068 static void wrapSymbols(ArrayRef<WrappedSymbol> wrapped) {
1069   DenseMap<Symbol *, Symbol *> map;
1070   for (const WrappedSymbol &w : wrapped) {
1071     map[w.sym] = w.wrap;
1072     map[w.real] = w.sym;
1073   }
1074
1075   // Update pointers in input files.
1076   parallelForEach(symtab->objectFiles, [&](InputFile *file) {
1077     MutableArrayRef<Symbol *> syms = file->getMutableSymbols();
1078     for (size_t i = 0, e = syms.size(); i != e; ++i)
1079       if (Symbol *s = map.lookup(syms[i]))
1080         syms[i] = s;
1081   });
1082
1083   // Update pointers in the symbol table.
1084   for (const WrappedSymbol &w : wrapped)
1085     symtab->wrap(w.sym, w.real, w.wrap);
1086 }
1087
1088 static void splitSections() {
1089   // splitIntoPieces needs to be called on each MergeInputChunk
1090   // before calling finalizeContents().
1091   LLVM_DEBUG(llvm::dbgs() << "splitSections\n");
1092   parallelForEach(symtab->objectFiles, [](ObjFile *file) {
1093     for (InputChunk *seg : file->segments) {
1094       if (auto *s = dyn_cast<MergeInputChunk>(seg))
1095         s->splitIntoPieces();
1096     }
1097     for (InputChunk *sec : file->customSections) {
1098       if (auto *s = dyn_cast<MergeInputChunk>(sec))
1099         s->splitIntoPieces();
1100     }
1101   });
1102 }
1103
1104 static bool isKnownZFlag(StringRef s) {
1105   // For now, we only support a very limited set of -z flags
1106   return s.starts_with("stack-size=");
1107 }
1108
1109 // Report a warning for an unknown -z option.
1110 static void checkZOptions(opt::InputArgList &args) {
1111   for (auto *arg : args.filtered(OPT_z))
1112     if (!isKnownZFlag(arg->getValue()))
1113       warn("unknown -z value: " + StringRef(arg->getValue()));
1114 }
1115
1116 void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
1117   WasmOptTable parser;
1118   opt::InputArgList args = parser.parse(argsArr.slice(1));
1119
1120   // Interpret these flags early because error()/warn() depend on them.
1121   errorHandler().errorLimit = args::getInteger(args, OPT_error_limit, 20);
1122   errorHandler().fatalWarnings =
1123       args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
1124   checkZOptions(args);
1125
1126   // Handle --help
1127   if (args.hasArg(OPT_help)) {
1128     parser.printHelp(lld::outs(),
1129                      (std::string(argsArr[0]) + " [options] file...").c_str(),
1130                      "LLVM Linker", false);
1131     return;
1132   }
1133
1134   // Handle --version
1135   if (args.hasArg(OPT_version) || args.hasArg(OPT_v)) {
1136     lld::outs() << getLLDVersion() << "\n";
1137     return;
1138   }
1139
1140   // Handle --reproduce
1141   if (const char *path = getReproduceOption(args)) {
1142     Expected<std::unique_ptr<TarWriter>> errOrWriter =
1143         TarWriter::create(path, path::stem(path));
1144     if (errOrWriter) {
1145       tar = std::move(*errOrWriter);
1146       tar->append("response.txt", createResponseFile(args));
1147       tar->append("version.txt", getLLDVersion() + "\n");
1148     } else {
1149       error("--reproduce: " + toString(errOrWriter.takeError()));
1150     }
1151   }
1152
1153   // Parse and evaluate -mllvm options.
1154   std::vector<const char *> v;
1155   v.push_back("wasm-ld (LLVM option parsing)");
1156   for (auto *arg : args.filtered(OPT_mllvm))
1157     v.push_back(arg->getValue());
1158   cl::ResetAllOptionOccurrences();
1159   cl::ParseCommandLineOptions(v.size(), v.data());
1160
1161   readConfigs(args);
1162   setConfigs();
1163
1164   createFiles(args);
1165   if (errorCount())
1166     return;
1167
1168   checkOptions(args);
1169   if (errorCount())
1170     return;
1171
1172   if (auto *arg = args.getLastArg(OPT_allow_undefined_file))
1173     readImportFile(arg->getValue());
1174
1175   // Fail early if the output file or map file is not writable. If a user has a
1176   // long link, e.g. due to a large LTO link, they do not wish to run it and
1177   // find that it failed because there was a mistake in their command-line.
1178   if (auto e = tryCreateFile(config->outputFile))
1179     error("cannot open output file " + config->outputFile + ": " + e.message());
1180   if (auto e = tryCreateFile(config->mapFile))
1181     error("cannot open map file " + config->mapFile + ": " + e.message());
1182   if (errorCount())
1183     return;
1184
1185   // Handle --trace-symbol.
1186   for (auto *arg : args.filtered(OPT_trace_symbol))
1187     symtab->trace(arg->getValue());
1188
1189   for (auto *arg : args.filtered(OPT_export_if_defined))
1190     config->exportedSymbols.insert(arg->getValue());
1191
1192   for (auto *arg : args.filtered(OPT_export)) {
1193     config->exportedSymbols.insert(arg->getValue());
1194     config->requiredExports.push_back(arg->getValue());
1195   }
1196
1197   createSyntheticSymbols();
1198
1199   // Add all files to the symbol table. This will add almost all
1200   // symbols that we need to the symbol table.
1201   for (InputFile *f : files)
1202     symtab->addFile(f);
1203   if (errorCount())
1204     return;
1205
1206   // Handle the `--undefined <sym>` options.
1207   for (auto *arg : args.filtered(OPT_undefined))
1208     handleUndefined(arg->getValue(), "<internal>");
1209
1210   // Handle the `--export <sym>` options
1211   // This works like --undefined but also exports the symbol if its found
1212   for (auto &iter : config->exportedSymbols)
1213     handleUndefined(iter.first(), "--export");
1214
1215   Symbol *entrySym = nullptr;
1216   if (!config->relocatable && !config->entry.empty()) {
1217     entrySym = handleUndefined(config->entry, "--entry");
1218     if (entrySym && entrySym->isDefined())
1219       entrySym->forceExport = true;
1220     else
1221       error("entry symbol not defined (pass --no-entry to suppress): " +
1222             config->entry);
1223   }
1224
1225   // If the user code defines a `__wasm_call_dtors` function, remember it so
1226   // that we can call it from the command export wrappers. Unlike
1227   // `__wasm_call_ctors` which we synthesize, `__wasm_call_dtors` is defined
1228   // by libc/etc., because destructors are registered dynamically with
1229   // `__cxa_atexit` and friends.
1230   if (!config->relocatable && !config->shared &&
1231       !WasmSym::callCtors->isUsedInRegularObj &&
1232       WasmSym::callCtors->getName() != config->entry &&
1233       !config->exportedSymbols.count(WasmSym::callCtors->getName())) {
1234     if (Symbol *callDtors =
1235             handleUndefined("__wasm_call_dtors", "<internal>")) {
1236       if (auto *callDtorsFunc = dyn_cast<DefinedFunction>(callDtors)) {
1237         if (callDtorsFunc->signature &&
1238             (!callDtorsFunc->signature->Params.empty() ||
1239              !callDtorsFunc->signature->Returns.empty())) {
1240           error("__wasm_call_dtors must have no argument or return values");
1241         }
1242         WasmSym::callDtors = callDtorsFunc;
1243       } else {
1244         error("__wasm_call_dtors must be a function");
1245       }
1246     }
1247   }
1248
1249   if (errorCount())
1250     return;
1251
1252   // Create wrapped symbols for -wrap option.
1253   std::vector<WrappedSymbol> wrapped = addWrappedSymbols(args);
1254
1255   // If any of our inputs are bitcode files, the LTO code generator may create
1256   // references to certain library functions that might not be explicit in the
1257   // bitcode file's symbol table. If any of those library functions are defined
1258   // in a bitcode file in an archive member, we need to arrange to use LTO to
1259   // compile those archive members by adding them to the link beforehand.
1260   //
1261   // We only need to add libcall symbols to the link before LTO if the symbol's
1262   // definition is in bitcode. Any other required libcall symbols will be added
1263   // to the link after LTO when we add the LTO object file to the link.
1264   if (!symtab->bitcodeFiles.empty())
1265     for (auto *s : lto::LTO::getRuntimeLibcallSymbols())
1266       handleLibcall(s);
1267   if (errorCount())
1268     return;
1269
1270   // We process the stub libraries once beofore LTO to ensure that any possible
1271   // required exports are preserved by the LTO process.
1272   processStubLibrariesPreLTO();
1273
1274   // Do link-time optimization if given files are LLVM bitcode files.
1275   // This compiles bitcode files into real object files.
1276   symtab->compileBitcodeFiles();
1277   if (errorCount())
1278     return;
1279
1280   // The LTO process can generate new undefined symbols, specifically libcall
1281   // functions.  Because those symbols might be declared in a stub library we
1282   // need the process the stub libraries once again after LTO to handle all
1283   // undefined symbols, including ones that didn't exist prior to LTO.
1284   processStubLibraries();
1285
1286   writeWhyExtract();
1287
1288   createOptionalSymbols();
1289
1290   // Resolve any variant symbols that were created due to signature
1291   // mismatchs.
1292   symtab->handleSymbolVariants();
1293   if (errorCount())
1294     return;
1295
1296   // Apply symbol renames for -wrap.
1297   if (!wrapped.empty())
1298     wrapSymbols(wrapped);
1299
1300   for (auto &iter : config->exportedSymbols) {
1301     Symbol *sym = symtab->find(iter.first());
1302     if (sym && sym->isDefined())
1303       sym->forceExport = true;
1304   }
1305
1306   if (!config->relocatable && !config->isPic) {
1307     // Add synthetic dummies for weak undefined functions.  Must happen
1308     // after LTO otherwise functions may not yet have signatures.
1309     symtab->handleWeakUndefines();
1310   }
1311
1312   if (entrySym)
1313     entrySym->setHidden(false);
1314
1315   if (errorCount())
1316     return;
1317
1318   // Split WASM_SEG_FLAG_STRINGS sections into pieces in preparation for garbage
1319   // collection.
1320   splitSections();
1321
1322   // Any remaining lazy symbols should be demoted to Undefined
1323   demoteLazySymbols();
1324
1325   // Do size optimizations: garbage collection
1326   markLive();
1327
1328   // Provide the indirect function table if needed.
1329   WasmSym::indirectFunctionTable =
1330       symtab->resolveIndirectFunctionTable(/*required =*/false);
1331
1332   if (errorCount())
1333     return;
1334
1335   // Write the result to the file.
1336   writeResult();
1337 }
1338
1339 } // namespace lld::wasm