tools/gold/gold-plugin.cpp

   1 //===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization  ------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This is a gold plugin for LLVM. It provides an LLVM implementation of the
  11 // interface described in http://gcc.gnu.org/wiki/whopr/driver .
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/ADT/Statistic.h"
  16 #include "llvm/Bitcode/BitcodeReader.h"
  17 #include "llvm/Bitcode/BitcodeWriter.h"
  18 #include "llvm/CodeGen/CommandFlags.inc"
  19 #include "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
  20 #include "llvm/IR/Constants.h"
  21 #include "llvm/IR/DiagnosticPrinter.h"
  22 #include "llvm/LTO/Caching.h"
  23 #include "llvm/LTO/LTO.h"
  24 #include "llvm/Object/Error.h"
  25 #include "llvm/Support/CachePruning.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/FileSystem.h"
  28 #include "llvm/Support/ManagedStatic.h"
  29 #include "llvm/Support/MemoryBuffer.h"
  30 #include "llvm/Support/Path.h"
  31 #include "llvm/Support/TargetSelect.h"
  32 #include "llvm/Support/raw_ostream.h"
  33 #include <list>
  34 #include <map>
  35 #include <plugin-api.h>
  36 #include <string>
  37 #include <system_error>
  38 #include <utility>
  39 #include <vector>
  40
  41 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
  42 // Precise and Debian Wheezy (binutils 2.23 is required)
  43 #define LDPO_PIE 3
  44
  45 #define LDPT_GET_SYMBOLS_V3 28
  46
  47 // FIXME: Remove when binutils 2.31 (containing gold 1.16) is the minimum
  48 // required version.
  49 #define LDPT_GET_WRAP_SYMBOLS 32
  50
  51 using namespace llvm;
  52 using namespace lto;
  53
  54 // FIXME: Remove when binutils 2.31 (containing gold 1.16) is the minimum
  55 // required version.
  56 typedef enum ld_plugin_status (*ld_plugin_get_wrap_symbols)(
  57     uint64_t *num_symbols, const char ***wrap_symbol_list);
  58
  59 static ld_plugin_status discard_message(int level, const char *format, ...) {
  60   // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
  61   // callback in the transfer vector. This should never be called.
  62   abort();
  63 }
  64
  65 static ld_plugin_release_input_file release_input_file = nullptr;
  66 static ld_plugin_get_input_file get_input_file = nullptr;
  67 static ld_plugin_message message = discard_message;
  68 static ld_plugin_get_wrap_symbols get_wrap_symbols = nullptr;
  69
  70 namespace {
  71 struct claimed_file {
  72   void *handle;
  73   void *leader_handle;
  74   std::vector<ld_plugin_symbol> syms;
  75   off_t filesize;
  76   std::string name;
  77 };
  78
  79 /// RAII wrapper to manage opening and releasing of a ld_plugin_input_file.
  80 struct PluginInputFile {
  81   void *Handle;
  82   std::unique_ptr<ld_plugin_input_file> File;
  83
  84   PluginInputFile(void *Handle) : Handle(Handle) {
  85     File = llvm::make_unique<ld_plugin_input_file>();
  86     if (get_input_file(Handle, File.get()) != LDPS_OK)
  87       message(LDPL_FATAL, "Failed to get file information");
  88   }
  89   ~PluginInputFile() {
  90     // File would have been reset to nullptr if we moved this object
  91     // to a new owner.
  92     if (File)
  93       if (release_input_file(Handle) != LDPS_OK)
  94         message(LDPL_FATAL, "Failed to release file information");
  95   }
  96
  97   ld_plugin_input_file &file() { return *File; }
  98
  99   PluginInputFile(PluginInputFile &&RHS) = default;
 100   PluginInputFile &operator=(PluginInputFile &&RHS) = default;
 101 };
 102
 103 struct ResolutionInfo {
 104   bool CanOmitFromDynSym = true;
 105   bool DefaultVisibility = true;
 106   bool CanInline = true;
 107   bool IsUsedInRegularObj = false;
 108 };
 109
 110 }
 111
 112 static ld_plugin_add_symbols add_symbols = nullptr;
 113 static ld_plugin_get_symbols get_symbols = nullptr;
 114 static ld_plugin_add_input_file add_input_file = nullptr;
 115 static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
 116 static ld_plugin_get_view get_view = nullptr;
 117 static bool IsExecutable = false;
 118 static bool SplitSections = true;
 119 static Optional<Reloc::Model> RelocationModel = None;
 120 static std::string output_name = "";
 121 static std::list<claimed_file> Modules;
 122 static DenseMap<int, void *> FDToLeaderHandle;
 123 static StringMap<ResolutionInfo> ResInfo;
 124 static std::vector<std::string> Cleanup;
 125
 126 namespace options {
 127   enum OutputType {
 128     OT_NORMAL,
 129     OT_DISABLE,
 130     OT_BC_ONLY,
 131     OT_ASM_ONLY,
 132     OT_SAVE_TEMPS
 133   };
 134   static OutputType TheOutputType = OT_NORMAL;
 135   static unsigned OptLevel = 2;
 136   // Default parallelism of 0 used to indicate that user did not specify.
 137   // Actual parallelism default value depends on implementation.
 138   // Currently only affects ThinLTO, where the default is
 139   // llvm::heavyweight_hardware_concurrency.
 140   static unsigned Parallelism = 0;
 141   // Default regular LTO codegen parallelism (number of partitions).
 142   static unsigned ParallelCodeGenParallelismLevel = 1;
 143 #ifdef NDEBUG
 144   static bool DisableVerify = true;
 145 #else
 146   static bool DisableVerify = false;
 147 #endif
 148   static std::string obj_path;
 149   static std::string extra_library_path;
 150   static std::string triple;
 151   static std::string mcpu;
 152   // When the thinlto plugin option is specified, only read the function
 153   // the information from intermediate files and write a combined
 154   // global index for the ThinLTO backends.
 155   static bool thinlto = false;
 156   // If false, all ThinLTO backend compilations through code gen are performed
 157   // using multiple threads in the gold-plugin, before handing control back to
 158   // gold. If true, write individual backend index files which reflect
 159   // the import decisions, and exit afterwards. The assumption is
 160   // that the build system will launch the backend processes.
 161   static bool thinlto_index_only = false;
 162   // If non-empty, holds the name of a file in which to write the list of
 163   // oject files gold selected for inclusion in the link after symbol
 164   // resolution (i.e. they had selected symbols). This will only be non-empty
 165   // in the thinlto_index_only case. It is used to identify files, which may
 166   // have originally been within archive libraries specified via
 167   // --start-lib/--end-lib pairs, that should be included in the final
 168   // native link process (since intervening function importing and inlining
 169   // may change the symbol resolution detected in the final link and which
 170   // files to include out of --start-lib/--end-lib libraries as a result).
 171   static std::string thinlto_linked_objects_file;
 172   // If true, when generating individual index files for distributed backends,
 173   // also generate a "${bitcodefile}.imports" file at the same location for each
 174   // bitcode file, listing the files it imports from in plain text. This is to
 175   // support distributed build file staging.
 176   static bool thinlto_emit_imports_files = false;
 177   // Option to control where files for a distributed backend (the individual
 178   // index files and optional imports files) are created.
 179   // If specified, expects a string of the form "oldprefix:newprefix", and
 180   // instead of generating these files in the same directory path as the
 181   // corresponding bitcode file, will use a path formed by replacing the
 182   // bitcode file's path prefix matching oldprefix with newprefix.
 183   static std::string thinlto_prefix_replace;
 184   // Option to control the name of modules encoded in the individual index
 185   // files for a distributed backend. This enables the use of minimized
 186   // bitcode files for the thin link, assuming the name of the full bitcode
 187   // file used in the backend differs just in some part of the file suffix.
 188   // If specified, expects a string of the form "oldsuffix:newsuffix".
 189   static std::string thinlto_object_suffix_replace;
 190   // Optional path to a directory for caching ThinLTO objects.
 191   static std::string cache_dir;
 192   // Optional pruning policy for ThinLTO caches.
 193   static std::string cache_policy;
 194   // Additional options to pass into the code generator.
 195   // Note: This array will contain all plugin options which are not claimed
 196   // as plugin exclusive to pass to the code generator.
 197   static std::vector<const char *> extra;
 198   // Sample profile file path
 199   static std::string sample_profile;
 200   // New pass manager
 201   static bool new_pass_manager = false;
 202   // Debug new pass manager
 203   static bool debug_pass_manager = false;
 204   // Directory to store the .dwo files.
 205   static std::string dwo_dir;
 206   /// Statistics output filename.
 207   static std::string stats_file;
 208
 209   // Optimization remarks filename and hotness options
 210   static std::string OptRemarksFilename;
 211   static bool OptRemarksWithHotness = false;
 212
 213   static void process_plugin_option(const char *opt_)
 214   {
 215     if (opt_ == nullptr)
 216       return;
 217     llvm::StringRef opt = opt_;
 218
 219     if (opt.startswith("mcpu=")) {
 220       mcpu = opt.substr(strlen("mcpu="));
 221     } else if (opt.startswith("extra-library-path=")) {
 222       extra_library_path = opt.substr(strlen("extra_library_path="));
 223     } else if (opt.startswith("mtriple=")) {
 224       triple = opt.substr(strlen("mtriple="));
 225     } else if (opt.startswith("obj-path=")) {
 226       obj_path = opt.substr(strlen("obj-path="));
 227     } else if (opt == "emit-llvm") {
 228       TheOutputType = OT_BC_ONLY;
 229     } else if (opt == "save-temps") {
 230       TheOutputType = OT_SAVE_TEMPS;
 231     } else if (opt == "disable-output") {
 232       TheOutputType = OT_DISABLE;
 233     } else if (opt == "emit-asm") {
 234       TheOutputType = OT_ASM_ONLY;
 235     } else if (opt == "thinlto") {
 236       thinlto = true;
 237     } else if (opt == "thinlto-index-only") {
 238       thinlto_index_only = true;
 239     } else if (opt.startswith("thinlto-index-only=")) {
 240       thinlto_index_only = true;
 241       thinlto_linked_objects_file = opt.substr(strlen("thinlto-index-only="));
 242     } else if (opt == "thinlto-emit-imports-files") {
 243       thinlto_emit_imports_files = true;
 244     } else if (opt.startswith("thinlto-prefix-replace=")) {
 245       thinlto_prefix_replace = opt.substr(strlen("thinlto-prefix-replace="));
 246       if (thinlto_prefix_replace.find(';') == std::string::npos)
 247         message(LDPL_FATAL, "thinlto-prefix-replace expects 'old;new' format");
 248     } else if (opt.startswith("thinlto-object-suffix-replace=")) {
 249       thinlto_object_suffix_replace =
 250           opt.substr(strlen("thinlto-object-suffix-replace="));
 251       if (thinlto_object_suffix_replace.find(';') == std::string::npos)
 252         message(LDPL_FATAL,
 253                 "thinlto-object-suffix-replace expects 'old;new' format");
 254     } else if (opt.startswith("cache-dir=")) {
 255       cache_dir = opt.substr(strlen("cache-dir="));
 256     } else if (opt.startswith("cache-policy=")) {
 257       cache_policy = opt.substr(strlen("cache-policy="));
 258     } else if (opt.size() == 2 && opt[0] == 'O') {
 259       if (opt[1] < '0' || opt[1] > '3')
 260         message(LDPL_FATAL, "Optimization level must be between 0 and 3");
 261       OptLevel = opt[1] - '0';
 262     } else if (opt.startswith("jobs=")) {
 263       if (StringRef(opt_ + 5).getAsInteger(10, Parallelism))
 264         message(LDPL_FATAL, "Invalid parallelism level: %s", opt_ + 5);
 265     } else if (opt.startswith("lto-partitions=")) {
 266       if (opt.substr(strlen("lto-partitions="))
 267               .getAsInteger(10, ParallelCodeGenParallelismLevel))
 268         message(LDPL_FATAL, "Invalid codegen partition level: %s", opt_ + 5);
 269     } else if (opt == "disable-verify") {
 270       DisableVerify = true;
 271     } else if (opt.startswith("sample-profile=")) {
 272       sample_profile= opt.substr(strlen("sample-profile="));
 273     } else if (opt == "new-pass-manager") {
 274       new_pass_manager = true;
 275     } else if (opt == "debug-pass-manager") {
 276       debug_pass_manager = true;
 277     } else if (opt.startswith("dwo_dir=")) {
 278       dwo_dir = opt.substr(strlen("dwo_dir="));
 279     } else if (opt.startswith("opt-remarks-filename=")) {
 280       OptRemarksFilename = opt.substr(strlen("opt-remarks-filename="));
 281     } else if (opt == "opt-remarks-with-hotness") {
 282       OptRemarksWithHotness = true;
 283     } else if (opt.startswith("stats-file=")) {
 284       stats_file = opt.substr(strlen("stats-file="));
 285     } else {
 286       // Save this option to pass to the code generator.
 287       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
 288       // add that.
 289       if (extra.empty())
 290         extra.push_back("LLVMgold");
 291
 292       extra.push_back(opt_);
 293     }
 294   }
 295 }
 296
 297 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 298                                         int *claimed);
 299 static ld_plugin_status all_symbols_read_hook(void);
 300 static ld_plugin_status cleanup_hook(void);
 301
 302 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
 303 ld_plugin_status onload(ld_plugin_tv *tv) {
 304   InitializeAllTargetInfos();
 305   InitializeAllTargets();
 306   InitializeAllTargetMCs();
 307   InitializeAllAsmParsers();
 308   InitializeAllAsmPrinters();
 309
 310   // We're given a pointer to the first transfer vector. We read through them
 311   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
 312   // contain pointers to functions that we need to call to register our own
 313   // hooks. The others are addresses of functions we can use to call into gold
 314   // for services.
 315
 316   bool registeredClaimFile = false;
 317   bool RegisteredAllSymbolsRead = false;
 318
 319   for (; tv->tv_tag != LDPT_NULL; ++tv) {
 320     // Cast tv_tag to int to allow values not in "enum ld_plugin_tag", like, for
 321     // example, LDPT_GET_SYMBOLS_V3 when building against an older plugin-api.h
 322     // header.
 323     switch (static_cast<int>(tv->tv_tag)) {
 324     case LDPT_OUTPUT_NAME:
 325       output_name = tv->tv_u.tv_string;
 326       break;
 327     case LDPT_LINKER_OUTPUT:
 328       switch (tv->tv_u.tv_val) {
 329       case LDPO_REL: // .o
 330         IsExecutable = false;
 331         SplitSections = false;
 332         break;
 333       case LDPO_DYN: // .so
 334         IsExecutable = false;
 335         RelocationModel = Reloc::PIC_;
 336         break;
 337       case LDPO_PIE: // position independent executable
 338         IsExecutable = true;
 339         RelocationModel = Reloc::PIC_;
 340         break;
 341       case LDPO_EXEC: // .exe
 342         IsExecutable = true;
 343         RelocationModel = Reloc::Static;
 344         break;
 345       default:
 346         message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
 347         return LDPS_ERR;
 348       }
 349       break;
 350     case LDPT_OPTION:
 351       options::process_plugin_option(tv->tv_u.tv_string);
 352       break;
 353     case LDPT_REGISTER_CLAIM_FILE_HOOK: {
 354       ld_plugin_register_claim_file callback;
 355       callback = tv->tv_u.tv_register_claim_file;
 356
 357       if (callback(claim_file_hook) != LDPS_OK)
 358         return LDPS_ERR;
 359
 360       registeredClaimFile = true;
 361     } break;
 362     case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
 363       ld_plugin_register_all_symbols_read callback;
 364       callback = tv->tv_u.tv_register_all_symbols_read;
 365
 366       if (callback(all_symbols_read_hook) != LDPS_OK)
 367         return LDPS_ERR;
 368
 369       RegisteredAllSymbolsRead = true;
 370     } break;
 371     case LDPT_REGISTER_CLEANUP_HOOK: {
 372       ld_plugin_register_cleanup callback;
 373       callback = tv->tv_u.tv_register_cleanup;
 374
 375       if (callback(cleanup_hook) != LDPS_OK)
 376         return LDPS_ERR;
 377     } break;
 378     case LDPT_GET_INPUT_FILE:
 379       get_input_file = tv->tv_u.tv_get_input_file;
 380       break;
 381     case LDPT_RELEASE_INPUT_FILE:
 382       release_input_file = tv->tv_u.tv_release_input_file;
 383       break;
 384     case LDPT_ADD_SYMBOLS:
 385       add_symbols = tv->tv_u.tv_add_symbols;
 386       break;
 387     case LDPT_GET_SYMBOLS_V2:
 388       // Do not override get_symbols_v3 with get_symbols_v2.
 389       if (!get_symbols)
 390         get_symbols = tv->tv_u.tv_get_symbols;
 391       break;
 392     case LDPT_GET_SYMBOLS_V3:
 393       get_symbols = tv->tv_u.tv_get_symbols;
 394       break;
 395     case LDPT_ADD_INPUT_FILE:
 396       add_input_file = tv->tv_u.tv_add_input_file;
 397       break;
 398     case LDPT_SET_EXTRA_LIBRARY_PATH:
 399       set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
 400       break;
 401     case LDPT_GET_VIEW:
 402       get_view = tv->tv_u.tv_get_view;
 403       break;
 404     case LDPT_MESSAGE:
 405       message = tv->tv_u.tv_message;
 406       break;
 407     case LDPT_GET_WRAP_SYMBOLS:
 408       // FIXME: When binutils 2.31 (containing gold 1.16) is the minimum
 409       // required version, this should be changed to:
 410       // get_wrap_symbols = tv->tv_u.tv_get_wrap_symbols;
 411       get_wrap_symbols =
 412           (ld_plugin_get_wrap_symbols)tv->tv_u.tv_message;
 413       break;
 414     default:
 415       break;
 416     }
 417   }
 418
 419   if (!registeredClaimFile) {
 420     message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
 421     return LDPS_ERR;
 422   }
 423   if (!add_symbols) {
 424     message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
 425     return LDPS_ERR;
 426   }
 427
 428   if (!RegisteredAllSymbolsRead)
 429     return LDPS_OK;
 430
 431   if (!get_input_file) {
 432     message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
 433     return LDPS_ERR;
 434   }
 435   if (!release_input_file) {
 436     message(LDPL_ERROR, "release_input_file not passed to LLVMgold.");
 437     return LDPS_ERR;
 438   }
 439
 440   return LDPS_OK;
 441 }
 442
 443 static void diagnosticHandler(const DiagnosticInfo &DI) {
 444   std::string ErrStorage;
 445   {
 446     raw_string_ostream OS(ErrStorage);
 447     DiagnosticPrinterRawOStream DP(OS);
 448     DI.print(DP);
 449   }
 450   ld_plugin_level Level;
 451   switch (DI.getSeverity()) {
 452   case DS_Error:
 453     Level = LDPL_FATAL;
 454     break;
 455   case DS_Warning:
 456     Level = LDPL_WARNING;
 457     break;
 458   case DS_Note:
 459   case DS_Remark:
 460     Level = LDPL_INFO;
 461     break;
 462   }
 463   message(Level, "LLVM gold plugin: %s",  ErrStorage.c_str());
 464 }
 465
 466 static void check(Error E, std::string Msg = "LLVM gold plugin") {
 467   handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error {
 468     message(LDPL_FATAL, "%s: %s", Msg.c_str(), EIB.message().c_str());
 469     return Error::success();
 470   });
 471 }
 472
 473 template <typename T> static T check(Expected<T> E) {
 474   if (E)
 475     return std::move(*E);
 476   check(E.takeError());
 477   return T();
 478 }
 479
 480 /// Called by gold to see whether this file is one that our plugin can handle.
 481 /// We'll try to open it and register all the symbols with add_symbol if
 482 /// possible.
 483 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 484                                         int *claimed) {
 485   MemoryBufferRef BufferRef;
 486   std::unique_ptr<MemoryBuffer> Buffer;
 487   if (get_view) {
 488     const void *view;
 489     if (get_view(file->handle, &view) != LDPS_OK) {
 490       message(LDPL_ERROR, "Failed to get a view of %s", file->name);
 491       return LDPS_ERR;
 492     }
 493     BufferRef =
 494         MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
 495   } else {
 496     int64_t offset = 0;
 497     // Gold has found what might be IR part-way inside of a file, such as
 498     // an .a archive.
 499     if (file->offset) {
 500       offset = file->offset;
 501     }
 502     ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
 503         MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
 504                                        offset);
 505     if (std::error_code EC = BufferOrErr.getError()) {
 506       message(LDPL_ERROR, EC.message().c_str());
 507       return LDPS_ERR;
 508     }
 509     Buffer = std::move(BufferOrErr.get());
 510     BufferRef = Buffer->getMemBufferRef();
 511   }
 512
 513   *claimed = 1;
 514
 515   Expected<std::unique_ptr<InputFile>> ObjOrErr = InputFile::create(BufferRef);
 516   if (!ObjOrErr) {
 517     handleAllErrors(ObjOrErr.takeError(), [&](const ErrorInfoBase &EI) {
 518       std::error_code EC = EI.convertToErrorCode();
 519       if (EC == object::object_error::invalid_file_type ||
 520           EC == object::object_error::bitcode_section_not_found)
 521         *claimed = 0;
 522       else
 523         message(LDPL_FATAL,
 524                 "LLVM gold plugin has failed to create LTO module: %s",
 525                 EI.message().c_str());
 526     });
 527
 528     return *claimed ? LDPS_ERR : LDPS_OK;
 529   }
 530
 531   std::unique_ptr<InputFile> Obj = std::move(*ObjOrErr);
 532
 533   Modules.emplace_back();
 534   claimed_file &cf = Modules.back();
 535
 536   cf.handle = file->handle;
 537   // Keep track of the first handle for each file descriptor, since there are
 538   // multiple in the case of an archive. This is used later in the case of
 539   // ThinLTO parallel backends to ensure that each file is only opened and
 540   // released once.
 541   auto LeaderHandle =
 542       FDToLeaderHandle.insert(std::make_pair(file->fd, file->handle)).first;
 543   cf.leader_handle = LeaderHandle->second;
 544   // Save the filesize since for parallel ThinLTO backends we can only
 545   // invoke get_input_file once per archive (only for the leader handle).
 546   cf.filesize = file->filesize;
 547   // In the case of an archive library, all but the first member must have a
 548   // non-zero offset, which we can append to the file name to obtain a
 549   // unique name.
 550   cf.name = file->name;
 551   if (file->offset)
 552     cf.name += ".llvm." + std::to_string(file->offset) + "." +
 553                sys::path::filename(Obj->getSourceFileName()).str();
 554
 555   for (auto &Sym : Obj->symbols()) {
 556     cf.syms.push_back(ld_plugin_symbol());
 557     ld_plugin_symbol &sym = cf.syms.back();
 558     sym.version = nullptr;
 559     StringRef Name = Sym.getName();
 560     sym.name = strdup(Name.str().c_str());
 561
 562     ResolutionInfo &Res = ResInfo[Name];
 563
 564     Res.CanOmitFromDynSym &= Sym.canBeOmittedFromSymbolTable();
 565
 566     sym.visibility = LDPV_DEFAULT;
 567     GlobalValue::VisibilityTypes Vis = Sym.getVisibility();
 568     if (Vis != GlobalValue::DefaultVisibility)
 569       Res.DefaultVisibility = false;
 570     switch (Vis) {
 571     case GlobalValue::DefaultVisibility:
 572       break;
 573     case GlobalValue::HiddenVisibility:
 574       sym.visibility = LDPV_HIDDEN;
 575       break;
 576     case GlobalValue::ProtectedVisibility:
 577       sym.visibility = LDPV_PROTECTED;
 578       break;
 579     }
 580
 581     if (Sym.isUndefined()) {
 582       sym.def = LDPK_UNDEF;
 583       if (Sym.isWeak())
 584         sym.def = LDPK_WEAKUNDEF;
 585     } else if (Sym.isCommon())
 586       sym.def = LDPK_COMMON;
 587     else if (Sym.isWeak())
 588       sym.def = LDPK_WEAKDEF;
 589     else
 590       sym.def = LDPK_DEF;
 591
 592     sym.size = 0;
 593     sym.comdat_key = nullptr;
 594     int CI = Sym.getComdatIndex();
 595     if (CI != -1) {
 596       StringRef C = Obj->getComdatTable()[CI];
 597       sym.comdat_key = strdup(C.str().c_str());
 598     }
 599
 600     sym.resolution = LDPR_UNKNOWN;
 601   }
 602
 603   if (!cf.syms.empty()) {
 604     if (add_symbols(cf.handle, cf.syms.size(), cf.syms.data()) != LDPS_OK) {
 605       message(LDPL_ERROR, "Unable to add symbols!");
 606       return LDPS_ERR;
 607     }
 608   }
 609
 610   // Handle any --wrap options passed to gold, which are than passed
 611   // along to the plugin.
 612   if (get_wrap_symbols) {
 613     const char **wrap_symbols;
 614     uint64_t count = 0;
 615     if (get_wrap_symbols(&count, &wrap_symbols) != LDPS_OK) {
 616       message(LDPL_ERROR, "Unable to get wrap symbols!");
 617       return LDPS_ERR;
 618     }
 619     for (uint64_t i = 0; i < count; i++) {
 620       StringRef Name = wrap_symbols[i];
 621       ResolutionInfo &Res = ResInfo[Name];
 622       ResolutionInfo &WrapRes = ResInfo["__wrap_" + Name.str()];
 623       ResolutionInfo &RealRes = ResInfo["__real_" + Name.str()];
 624       // Tell LTO not to inline symbols that will be overwritten.
 625       Res.CanInline = false;
 626       RealRes.CanInline = false;
 627       // Tell LTO not to eliminate symbols that will be used after renaming.
 628       Res.IsUsedInRegularObj = true;
 629       WrapRes.IsUsedInRegularObj = true;
 630     }
 631   }
 632
 633   return LDPS_OK;
 634 }
 635
 636 static void freeSymName(ld_plugin_symbol &Sym) {
 637   free(Sym.name);
 638   free(Sym.comdat_key);
 639   Sym.name = nullptr;
 640   Sym.comdat_key = nullptr;
 641 }
 642
 643 /// Helper to get a file's symbols and a view into it via gold callbacks.
 644 static const void *getSymbolsAndView(claimed_file &F) {
 645   ld_plugin_status status = get_symbols(F.handle, F.syms.size(), F.syms.data());
 646   if (status == LDPS_NO_SYMS)
 647     return nullptr;
 648
 649   if (status != LDPS_OK)
 650     message(LDPL_FATAL, "Failed to get symbol information");
 651
 652   const void *View;
 653   if (get_view(F.handle, &View) != LDPS_OK)
 654     message(LDPL_FATAL, "Failed to get a view of file");
 655
 656   return View;
 657 }
 658
 659 /// Parse the thinlto-object-suffix-replace option into the \p OldSuffix and
 660 /// \p NewSuffix strings, if it was specified.
 661 static void getThinLTOOldAndNewSuffix(std::string &OldSuffix,
 662                                       std::string &NewSuffix) {
 663   assert(options::thinlto_object_suffix_replace.empty() ||
 664          options::thinlto_object_suffix_replace.find(";") != StringRef::npos);
 665   StringRef SuffixReplace = options::thinlto_object_suffix_replace;
 666   std::tie(OldSuffix, NewSuffix) = SuffixReplace.split(';');
 667 }
 668
 669 /// Given the original \p Path to an output file, replace any filename
 670 /// suffix matching \p OldSuffix with \p NewSuffix.
 671 static std::string getThinLTOObjectFileName(StringRef Path, StringRef OldSuffix,
 672                                             StringRef NewSuffix) {
 673   if (Path.consume_back(OldSuffix))
 674     return (Path + NewSuffix).str();
 675   return Path;
 676 }
 677
 678 // Returns true if S is valid as a C language identifier.
 679 static bool isValidCIdentifier(StringRef S) {
 680   return !S.empty() && (isAlpha(S[0]) || S[0] == '_') &&
 681          std::all_of(S.begin() + 1, S.end(),
 682                      [](char C) { return C == '_' || isAlnum(C); });
 683 }
 684
 685 static bool isUndefined(ld_plugin_symbol &Sym) {
 686   return Sym.def == LDPK_UNDEF || Sym.def == LDPK_WEAKUNDEF;
 687 }
 688
 689 static void addModule(LTO &Lto, claimed_file &F, const void *View,
 690                       StringRef Filename) {
 691   MemoryBufferRef BufferRef(StringRef((const char *)View, F.filesize),
 692                             Filename);
 693   Expected<std::unique_ptr<InputFile>> ObjOrErr = InputFile::create(BufferRef);
 694
 695   if (!ObjOrErr)
 696     message(LDPL_FATAL, "Could not read bitcode from file : %s",
 697             toString(ObjOrErr.takeError()).c_str());
 698
 699   unsigned SymNum = 0;
 700   std::unique_ptr<InputFile> Input = std::move(ObjOrErr.get());
 701   auto InputFileSyms = Input->symbols();
 702   assert(InputFileSyms.size() == F.syms.size());
 703   std::vector<SymbolResolution> Resols(F.syms.size());
 704   for (ld_plugin_symbol &Sym : F.syms) {
 705     const InputFile::Symbol &InpSym = InputFileSyms[SymNum];
 706     SymbolResolution &R = Resols[SymNum++];
 707
 708     ld_plugin_symbol_resolution Resolution =
 709         (ld_plugin_symbol_resolution)Sym.resolution;
 710
 711     ResolutionInfo &Res = ResInfo[Sym.name];
 712
 713     switch (Resolution) {
 714     case LDPR_UNKNOWN:
 715       llvm_unreachable("Unexpected resolution");
 716
 717     case LDPR_RESOLVED_IR:
 718     case LDPR_RESOLVED_EXEC:
 719     case LDPR_RESOLVED_DYN:
 720     case LDPR_PREEMPTED_IR:
 721     case LDPR_PREEMPTED_REG:
 722     case LDPR_UNDEF:
 723       break;
 724
 725     case LDPR_PREVAILING_DEF_IRONLY:
 726       R.Prevailing = !isUndefined(Sym);
 727       break;
 728
 729     case LDPR_PREVAILING_DEF:
 730       R.Prevailing = !isUndefined(Sym);
 731       R.VisibleToRegularObj = true;
 732       break;
 733
 734     case LDPR_PREVAILING_DEF_IRONLY_EXP:
 735       R.Prevailing = !isUndefined(Sym);
 736       if (!Res.CanOmitFromDynSym)
 737         R.VisibleToRegularObj = true;
 738       break;
 739     }
 740
 741     // If the symbol has a C identifier section name, we need to mark
 742     // it as visible to a regular object so that LTO will keep it around
 743     // to ensure the linker generates special __start_<secname> and
 744     // __stop_<secname> symbols which may be used elsewhere.
 745     if (isValidCIdentifier(InpSym.getSectionName()))
 746       R.VisibleToRegularObj = true;
 747
 748     if (Resolution != LDPR_RESOLVED_DYN && Resolution != LDPR_UNDEF &&
 749         (IsExecutable || !Res.DefaultVisibility))
 750       R.FinalDefinitionInLinkageUnit = true;
 751
 752     if (!Res.CanInline)
 753       R.LinkerRedefined = true;
 754
 755     if (Res.IsUsedInRegularObj)
 756       R.VisibleToRegularObj = true;
 757
 758     freeSymName(Sym);
 759   }
 760
 761   check(Lto.add(std::move(Input), Resols),
 762         std::string("Failed to link module ") + F.name);
 763 }
 764
 765 static void recordFile(const std::string &Filename, bool TempOutFile) {
 766   if (add_input_file(Filename.c_str()) != LDPS_OK)
 767     message(LDPL_FATAL,
 768             "Unable to add .o file to the link. File left behind in: %s",
 769             Filename.c_str());
 770   if (TempOutFile)
 771     Cleanup.push_back(Filename);
 772 }
 773
 774 /// Return the desired output filename given a base input name, a flag
 775 /// indicating whether a temp file should be generated, and an optional task id.
 776 /// The new filename generated is returned in \p NewFilename.
 777 static int getOutputFileName(StringRef InFilename, bool TempOutFile,
 778                              SmallString<128> &NewFilename, int TaskID) {
 779   int FD = -1;
 780   if (TempOutFile) {
 781     std::error_code EC =
 782         sys::fs::createTemporaryFile("lto-llvm", "o", FD, NewFilename);
 783     if (EC)
 784       message(LDPL_FATAL, "Could not create temporary file: %s",
 785               EC.message().c_str());
 786   } else {
 787     NewFilename = InFilename;
 788     if (TaskID > 0)
 789       NewFilename += utostr(TaskID);
 790     std::error_code EC =
 791         sys::fs::openFileForWrite(NewFilename, FD, sys::fs::CD_CreateAlways);
 792     if (EC)
 793       message(LDPL_FATAL, "Could not open file %s: %s", NewFilename.c_str(),
 794               EC.message().c_str());
 795   }
 796   return FD;
 797 }
 798
 799 static CodeGenOpt::Level getCGOptLevel() {
 800   switch (options::OptLevel) {
 801   case 0:
 802     return CodeGenOpt::None;
 803   case 1:
 804     return CodeGenOpt::Less;
 805   case 2:
 806     return CodeGenOpt::Default;
 807   case 3:
 808     return CodeGenOpt::Aggressive;
 809   }
 810   llvm_unreachable("Invalid optimization level");
 811 }
 812
 813 /// Parse the thinlto_prefix_replace option into the \p OldPrefix and
 814 /// \p NewPrefix strings, if it was specified.
 815 static void getThinLTOOldAndNewPrefix(std::string &OldPrefix,
 816                                       std::string &NewPrefix) {
 817   StringRef PrefixReplace = options::thinlto_prefix_replace;
 818   assert(PrefixReplace.empty() || PrefixReplace.find(";") != StringRef::npos);
 819   std::tie(OldPrefix, NewPrefix) = PrefixReplace.split(';');
 820 }
 821
 822 /// Creates instance of LTO.
 823 /// OnIndexWrite is callback to let caller know when LTO writes index files.
 824 /// LinkedObjectsFile is an output stream to write the list of object files for
 825 /// the final ThinLTO linking. Can be nullptr.
 826 static std::unique_ptr<LTO> createLTO(IndexWriteCallback OnIndexWrite,
 827                                       raw_fd_ostream *LinkedObjectsFile) {
 828   Config Conf;
 829   ThinBackend Backend;
 830
 831   Conf.CPU = options::mcpu;
 832   Conf.Options = InitTargetOptionsFromCodeGenFlags();
 833
 834   // Disable the new X86 relax relocations since gold might not support them.
 835   // FIXME: Check the gold version or add a new option to enable them.
 836   Conf.Options.RelaxELFRelocations = false;
 837
 838   // Toggle function/data sections.
 839   if (FunctionSections.getNumOccurrences() == 0)
 840     Conf.Options.FunctionSections = SplitSections;
 841   if (DataSections.getNumOccurrences() == 0)
 842     Conf.Options.DataSections = SplitSections;
 843
 844   Conf.MAttrs = MAttrs;
 845   Conf.RelocModel = RelocationModel;
 846   Conf.CodeModel = getCodeModel();
 847   Conf.CGOptLevel = getCGOptLevel();
 848   Conf.DisableVerify = options::DisableVerify;
 849   Conf.OptLevel = options::OptLevel;
 850   if (options::Parallelism)
 851     Backend = createInProcessThinBackend(options::Parallelism);
 852   if (options::thinlto_index_only) {
 853     std::string OldPrefix, NewPrefix;
 854     getThinLTOOldAndNewPrefix(OldPrefix, NewPrefix);
 855     Backend = createWriteIndexesThinBackend(OldPrefix, NewPrefix,
 856                                             options::thinlto_emit_imports_files,
 857                                             LinkedObjectsFile, OnIndexWrite);
 858   }
 859
 860   Conf.OverrideTriple = options::triple;
 861   Conf.DefaultTriple = sys::getDefaultTargetTriple();
 862
 863   Conf.DiagHandler = diagnosticHandler;
 864
 865   switch (options::TheOutputType) {
 866   case options::OT_NORMAL:
 867     break;
 868
 869   case options::OT_DISABLE:
 870     Conf.PreOptModuleHook = [](size_t Task, const Module &M) { return false; };
 871     break;
 872
 873   case options::OT_BC_ONLY:
 874     Conf.PostInternalizeModuleHook = [](size_t Task, const Module &M) {
 875       std::error_code EC;
 876       raw_fd_ostream OS(output_name, EC, sys::fs::OpenFlags::F_None);
 877       if (EC)
 878         message(LDPL_FATAL, "Failed to write the output file.");
 879       WriteBitcodeToFile(M, OS, /* ShouldPreserveUseListOrder */ false);
 880       return false;
 881     };
 882     break;
 883
 884   case options::OT_SAVE_TEMPS:
 885     check(Conf.addSaveTemps(output_name + ".",
 886                             /* UseInputModulePath */ true));
 887     break;
 888   case options::OT_ASM_ONLY:
 889     Conf.CGFileType = TargetMachine::CGFT_AssemblyFile;
 890     break;
 891   }
 892
 893   if (!options::sample_profile.empty())
 894     Conf.SampleProfile = options::sample_profile;
 895
 896   Conf.DwoDir = options::dwo_dir;
 897
 898   // Set up optimization remarks handling.
 899   Conf.RemarksFilename = options::OptRemarksFilename;
 900   Conf.RemarksWithHotness = options::OptRemarksWithHotness;
 901
 902   // Use new pass manager if set in driver
 903   Conf.UseNewPM = options::new_pass_manager;
 904   // Debug new pass manager if requested
 905   Conf.DebugPassManager = options::debug_pass_manager;
 906
 907   Conf.StatsFile = options::stats_file;
 908   return llvm::make_unique<LTO>(std::move(Conf), Backend,
 909                                 options::ParallelCodeGenParallelismLevel);
 910 }
 911
 912 // Write empty files that may be expected by a distributed build
 913 // system when invoked with thinlto_index_only. This is invoked when
 914 // the linker has decided not to include the given module in the
 915 // final link. Frequently the distributed build system will want to
 916 // confirm that all expected outputs are created based on all of the
 917 // modules provided to the linker.
 918 // If SkipModule is true then .thinlto.bc should contain just
 919 // SkipModuleByDistributedBackend flag which requests distributed backend
 920 // to skip the compilation of the corresponding module and produce an empty
 921 // object file.
 922 static void writeEmptyDistributedBuildOutputs(const std::string &ModulePath,
 923                                               const std::string &OldPrefix,
 924                                               const std::string &NewPrefix,
 925                                               bool SkipModule) {
 926   std::string NewModulePath =
 927       getThinLTOOutputFile(ModulePath, OldPrefix, NewPrefix);
 928   std::error_code EC;
 929   {
 930     raw_fd_ostream OS(NewModulePath + ".thinlto.bc", EC,
 931                       sys::fs::OpenFlags::F_None);
 932     if (EC)
 933       message(LDPL_FATAL, "Failed to write '%s': %s",
 934               (NewModulePath + ".thinlto.bc").c_str(), EC.message().c_str());
 935
 936     if (SkipModule) {
 937       ModuleSummaryIndex Index(/*HaveGVs*/ false);
 938       Index.setSkipModuleByDistributedBackend();
 939       WriteIndexToFile(Index, OS, nullptr);
 940     }
 941   }
 942   if (options::thinlto_emit_imports_files) {
 943     raw_fd_ostream OS(NewModulePath + ".imports", EC,
 944                       sys::fs::OpenFlags::F_None);
 945     if (EC)
 946       message(LDPL_FATAL, "Failed to write '%s': %s",
 947               (NewModulePath + ".imports").c_str(), EC.message().c_str());
 948   }
 949 }
 950
 951 // Creates and returns output stream with a list of object files for final
 952 // linking of distributed ThinLTO.
 953 static std::unique_ptr<raw_fd_ostream> CreateLinkedObjectsFile() {
 954   if (options::thinlto_linked_objects_file.empty())
 955     return nullptr;
 956   assert(options::thinlto_index_only);
 957   std::error_code EC;
 958   auto LinkedObjectsFile = llvm::make_unique<raw_fd_ostream>(
 959       options::thinlto_linked_objects_file, EC, sys::fs::OpenFlags::F_None);
 960   if (EC)
 961     message(LDPL_FATAL, "Failed to create '%s': %s",
 962             options::thinlto_linked_objects_file.c_str(), EC.message().c_str());
 963   return LinkedObjectsFile;
 964 }
 965
 966 /// Runs LTO and return a list of pairs <FileName, IsTemporary>.
 967 static std::vector<std::pair<SmallString<128>, bool>> runLTO() {
 968   // Map to own RAII objects that manage the file opening and releasing
 969   // interfaces with gold. This is needed only for ThinLTO mode, since
 970   // unlike regular LTO, where addModule will result in the opened file
 971   // being merged into a new combined module, we need to keep these files open
 972   // through Lto->run().
 973   DenseMap<void *, std::unique_ptr<PluginInputFile>> HandleToInputFile;
 974
 975   // Owns string objects and tells if index file was already created.
 976   StringMap<bool> ObjectToIndexFileState;
 977
 978   std::unique_ptr<raw_fd_ostream> LinkedObjects = CreateLinkedObjectsFile();
 979   std::unique_ptr<LTO> Lto = createLTO(
 980       [&ObjectToIndexFileState](const std::string &Identifier) {
 981         ObjectToIndexFileState[Identifier] = true;
 982       },
 983       LinkedObjects.get());
 984
 985   std::string OldPrefix, NewPrefix;
 986   if (options::thinlto_index_only)
 987     getThinLTOOldAndNewPrefix(OldPrefix, NewPrefix);
 988
 989   std::string OldSuffix, NewSuffix;
 990   getThinLTOOldAndNewSuffix(OldSuffix, NewSuffix);
 991
 992   for (claimed_file &F : Modules) {
 993     if (options::thinlto && !HandleToInputFile.count(F.leader_handle))
 994       HandleToInputFile.insert(std::make_pair(
 995           F.leader_handle, llvm::make_unique<PluginInputFile>(F.handle)));
 996     // In case we are thin linking with a minimized bitcode file, ensure
 997     // the module paths encoded in the index reflect where the backends
 998     // will locate the full bitcode files for compiling/importing.
 999     std::string Identifier =
1000         getThinLTOObjectFileName(F.name, OldSuffix, NewSuffix);
1001     auto ObjFilename = ObjectToIndexFileState.insert({Identifier, false});
1002     assert(ObjFilename.second);
1003     if (const void *View = getSymbolsAndView(F))
1004       addModule(*Lto, F, View, ObjFilename.first->first());
1005     else if (options::thinlto_index_only) {
1006       ObjFilename.first->second = true;
1007       writeEmptyDistributedBuildOutputs(Identifier, OldPrefix, NewPrefix,
1008                                         /* SkipModule */ true);
1009     }
1010   }
1011
1012   SmallString<128> Filename;
1013   // Note that getOutputFileName will append a unique ID for each task
1014   if (!options::obj_path.empty())
1015     Filename = options::obj_path;
1016   else if (options::TheOutputType == options::OT_SAVE_TEMPS)
1017     Filename = output_name + ".o";
1018   else if (options::TheOutputType == options::OT_ASM_ONLY)
1019     Filename = output_name;
1020   bool SaveTemps = !Filename.empty();
1021
1022   size_t MaxTasks = Lto->getMaxTasks();
1023   std::vector<std::pair<SmallString<128>, bool>> Files(MaxTasks);
1024
1025   auto AddStream =
1026       [&](size_t Task) -> std::unique_ptr<lto::NativeObjectStream> {
1027     Files[Task].second = !SaveTemps;
1028     int FD = getOutputFileName(Filename, /* TempOutFile */ !SaveTemps,
1029                                Files[Task].first, Task);
1030     return llvm::make_unique<lto::NativeObjectStream>(
1031         llvm::make_unique<llvm::raw_fd_ostream>(FD, true));
1032   };
1033
1034   auto AddBuffer = [&](size_t Task, std::unique_ptr<MemoryBuffer> MB) {
1035     *AddStream(Task)->OS << MB->getBuffer();
1036   };
1037
1038   NativeObjectCache Cache;
1039   if (!options::cache_dir.empty())
1040     Cache = check(localCache(options::cache_dir, AddBuffer));
1041
1042   check(Lto->run(AddStream, Cache));
1043
1044   // Write empty output files that may be expected by the distributed build
1045   // system.
1046   if (options::thinlto_index_only)
1047     for (auto &Identifier : ObjectToIndexFileState)
1048       if (!Identifier.getValue())
1049         writeEmptyDistributedBuildOutputs(Identifier.getKey(), OldPrefix,
1050                                           NewPrefix, /* SkipModule */ false);
1051
1052   return Files;
1053 }
1054
1055 /// gold informs us that all symbols have been read. At this point, we use
1056 /// get_symbols to see if any of our definitions have been overridden by a
1057 /// native object file. Then, perform optimization and codegen.
1058 static ld_plugin_status allSymbolsReadHook() {
1059   if (Modules.empty())
1060     return LDPS_OK;
1061
1062   if (unsigned NumOpts = options::extra.size())
1063     cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
1064
1065   std::vector<std::pair<SmallString<128>, bool>> Files = runLTO();
1066
1067   if (options::TheOutputType == options::OT_DISABLE ||
1068       options::TheOutputType == options::OT_BC_ONLY ||
1069       options::TheOutputType == options::OT_ASM_ONLY)
1070     return LDPS_OK;
1071
1072   if (options::thinlto_index_only) {
1073     llvm_shutdown();
1074     cleanup_hook();
1075     exit(0);
1076   }
1077
1078   for (const auto &F : Files)
1079     if (!F.first.empty())
1080       recordFile(F.first.str(), F.second);
1081
1082   if (!options::extra_library_path.empty() &&
1083       set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
1084     message(LDPL_FATAL, "Unable to set the extra library path.");
1085
1086   return LDPS_OK;
1087 }
1088
1089 static ld_plugin_status all_symbols_read_hook(void) {
1090   ld_plugin_status Ret = allSymbolsReadHook();
1091   llvm_shutdown();
1092
1093   if (options::TheOutputType == options::OT_BC_ONLY ||
1094       options::TheOutputType == options::OT_ASM_ONLY ||
1095       options::TheOutputType == options::OT_DISABLE) {
1096     if (options::TheOutputType == options::OT_DISABLE) {
1097       // Remove the output file here since ld.bfd creates the output file
1098       // early.
1099       std::error_code EC = sys::fs::remove(output_name);
1100       if (EC)
1101         message(LDPL_ERROR, "Failed to delete '%s': %s", output_name.c_str(),
1102                 EC.message().c_str());
1103     }
1104     exit(0);
1105   }
1106
1107   return Ret;
1108 }
1109
1110 static ld_plugin_status cleanup_hook(void) {
1111   for (std::string &Name : Cleanup) {
1112     std::error_code EC = sys::fs::remove(Name);
1113     if (EC)
1114       message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
1115               EC.message().c_str());
1116   }
1117
1118   // Prune cache
1119   if (!options::cache_dir.empty()) {
1120     CachePruningPolicy policy = check(parseCachePruningPolicy(options::cache_policy));
1121     pruneCache(options::cache_dir, policy);
1122   }
1123
1124   return LDPS_OK;
1125 }