tools/gold/gold-plugin.cpp

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