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