src/llvm/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/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
  16 #include "llvm/ADT/DenseSet.h"
  17 #include "llvm/ADT/StringSet.h"
  18 #include "llvm/Bitcode/ReaderWriter.h"
  19 #include "llvm/CodeGen/Analysis.h"
  20 #include "llvm/CodeGen/CommandFlags.h"
  21 #include "llvm/IR/Constants.h"
  22 #include "llvm/IR/DiagnosticInfo.h"
  23 #include "llvm/IR/DiagnosticPrinter.h"
  24 #include "llvm/IR/LLVMContext.h"
  25 #include "llvm/IR/Module.h"
  26 #include "llvm/IR/Verifier.h"
  27 #include "llvm/Linker/Linker.h"
  28 #include "llvm/MC/SubtargetFeature.h"
  29 #include "llvm/Object/IRObjectFile.h"
  30 #include "llvm/PassManager.h"
  31 #include "llvm/Support/FormattedStream.h"
  32 #include "llvm/Support/Host.h"
  33 #include "llvm/Support/ManagedStatic.h"
  34 #include "llvm/Support/MemoryBuffer.h"
  35 #include "llvm/Support/TargetRegistry.h"
  36 #include "llvm/Support/TargetSelect.h"
  37 #include "llvm/Target/TargetLibraryInfo.h"
  38 #include "llvm/Transforms/IPO.h"
  39 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
  40 #include "llvm/Transforms/Utils/GlobalStatus.h"
  41 #include "llvm/Transforms/Utils/ModuleUtils.h"
  42 #include "llvm/Transforms/Utils/ValueMapper.h"
  43 #include <list>
  44 #include <plugin-api.h>
  45 #include <system_error>
  46 #include <vector>
  47
  48 #ifndef LDPO_PIE
  49 // FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
  50 // Precise and Debian Wheezy (binutils 2.23 is required)
  51 # define LDPO_PIE 3
  52 #endif
  53
  54 using namespace llvm;
  55
  56 namespace {
  57 struct claimed_file {
  58   void *handle;
  59   std::vector<ld_plugin_symbol> syms;
  60 };
  61 }
  62
  63 static ld_plugin_status discard_message(int level, const char *format, ...) {
  64   // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
  65   // callback in the transfer vector. This should never be called.
  66   abort();
  67 }
  68
  69 static ld_plugin_get_input_file get_input_file = nullptr;
  70 static ld_plugin_release_input_file release_input_file = nullptr;
  71 static ld_plugin_add_symbols add_symbols = nullptr;
  72 static ld_plugin_get_symbols get_symbols = nullptr;
  73 static ld_plugin_add_input_file add_input_file = nullptr;
  74 static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
  75 static ld_plugin_get_view get_view = nullptr;
  76 static ld_plugin_message message = discard_message;
  77 static Reloc::Model RelocationModel = Reloc::Default;
  78 static std::string output_name = "";
  79 static std::list<claimed_file> Modules;
  80 static std::vector<std::string> Cleanup;
  81 static llvm::TargetOptions TargetOpts;
  82
  83 namespace options {
  84   enum OutputType {
  85     OT_NORMAL,
  86     OT_DISABLE,
  87     OT_BC_ONLY,
  88     OT_SAVE_TEMPS
  89   };
  90   static bool generate_api_file = false;
  91   static OutputType TheOutputType = OT_NORMAL;
  92   static std::string obj_path;
  93   static std::string extra_library_path;
  94   static std::string triple;
  95   static std::string mcpu;
  96   // Additional options to pass into the code generator.
  97   // Note: This array will contain all plugin options which are not claimed
  98   // as plugin exclusive to pass to the code generator.
  99   // For example, "generate-api-file" and "as"options are for the plugin
 100   // use only and will not be passed.
 101   static std::vector<const char *> extra;
 102
 103   static void process_plugin_option(const char* opt_)
 104   {
 105     if (opt_ == nullptr)
 106       return;
 107     llvm::StringRef opt = opt_;
 108
 109     if (opt == "generate-api-file") {
 110       generate_api_file = true;
 111     } else if (opt.startswith("mcpu=")) {
 112       mcpu = opt.substr(strlen("mcpu="));
 113     } else if (opt.startswith("extra-library-path=")) {
 114       extra_library_path = opt.substr(strlen("extra_library_path="));
 115     } else if (opt.startswith("mtriple=")) {
 116       triple = opt.substr(strlen("mtriple="));
 117     } else if (opt.startswith("obj-path=")) {
 118       obj_path = opt.substr(strlen("obj-path="));
 119     } else if (opt == "emit-llvm") {
 120       TheOutputType = OT_BC_ONLY;
 121     } else if (opt == "save-temps") {
 122       TheOutputType = OT_SAVE_TEMPS;
 123     } else if (opt == "disable-output") {
 124       TheOutputType = OT_DISABLE;
 125     } else {
 126       // Save this option to pass to the code generator.
 127       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
 128       // add that.
 129       if (extra.empty())
 130         extra.push_back("LLVMgold");
 131
 132       extra.push_back(opt_);
 133     }
 134   }
 135 }
 136
 137 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 138                                         int *claimed);
 139 static ld_plugin_status all_symbols_read_hook(void);
 140 static ld_plugin_status cleanup_hook(void);
 141
 142 extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
 143 ld_plugin_status onload(ld_plugin_tv *tv) {
 144   InitializeAllTargetInfos();
 145   InitializeAllTargets();
 146   InitializeAllTargetMCs();
 147   InitializeAllAsmParsers();
 148   InitializeAllAsmPrinters();
 149
 150   // We're given a pointer to the first transfer vector. We read through them
 151   // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
 152   // contain pointers to functions that we need to call to register our own
 153   // hooks. The others are addresses of functions we can use to call into gold
 154   // for services.
 155
 156   bool registeredClaimFile = false;
 157   bool RegisteredAllSymbolsRead = false;
 158
 159   for (; tv->tv_tag != LDPT_NULL; ++tv) {
 160     switch (tv->tv_tag) {
 161       case LDPT_OUTPUT_NAME:
 162         output_name = tv->tv_u.tv_string;
 163         break;
 164       case LDPT_LINKER_OUTPUT:
 165         switch (tv->tv_u.tv_val) {
 166           case LDPO_REL:  // .o
 167           case LDPO_DYN:  // .so
 168           case LDPO_PIE:  // position independent executable
 169             RelocationModel = Reloc::PIC_;
 170             break;
 171           case LDPO_EXEC:  // .exe
 172             RelocationModel = Reloc::Static;
 173             break;
 174           default:
 175             message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
 176             return LDPS_ERR;
 177         }
 178         break;
 179       case LDPT_OPTION:
 180         options::process_plugin_option(tv->tv_u.tv_string);
 181         break;
 182       case LDPT_REGISTER_CLAIM_FILE_HOOK: {
 183         ld_plugin_register_claim_file callback;
 184         callback = tv->tv_u.tv_register_claim_file;
 185
 186         if (callback(claim_file_hook) != LDPS_OK)
 187           return LDPS_ERR;
 188
 189         registeredClaimFile = true;
 190       } break;
 191       case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
 192         ld_plugin_register_all_symbols_read callback;
 193         callback = tv->tv_u.tv_register_all_symbols_read;
 194
 195         if (callback(all_symbols_read_hook) != LDPS_OK)
 196           return LDPS_ERR;
 197
 198         RegisteredAllSymbolsRead = true;
 199       } break;
 200       case LDPT_REGISTER_CLEANUP_HOOK: {
 201         ld_plugin_register_cleanup callback;
 202         callback = tv->tv_u.tv_register_cleanup;
 203
 204         if (callback(cleanup_hook) != LDPS_OK)
 205           return LDPS_ERR;
 206       } break;
 207       case LDPT_GET_INPUT_FILE:
 208         get_input_file = tv->tv_u.tv_get_input_file;
 209         break;
 210       case LDPT_RELEASE_INPUT_FILE:
 211         release_input_file = tv->tv_u.tv_release_input_file;
 212         break;
 213       case LDPT_ADD_SYMBOLS:
 214         add_symbols = tv->tv_u.tv_add_symbols;
 215         break;
 216       case LDPT_GET_SYMBOLS_V2:
 217         get_symbols = tv->tv_u.tv_get_symbols;
 218         break;
 219       case LDPT_ADD_INPUT_FILE:
 220         add_input_file = tv->tv_u.tv_add_input_file;
 221         break;
 222       case LDPT_SET_EXTRA_LIBRARY_PATH:
 223         set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
 224         break;
 225       case LDPT_GET_VIEW:
 226         get_view = tv->tv_u.tv_get_view;
 227         break;
 228       case LDPT_MESSAGE:
 229         message = tv->tv_u.tv_message;
 230         break;
 231       default:
 232         break;
 233     }
 234   }
 235
 236   if (!registeredClaimFile) {
 237     message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
 238     return LDPS_ERR;
 239   }
 240   if (!add_symbols) {
 241     message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
 242     return LDPS_ERR;
 243   }
 244
 245   if (!RegisteredAllSymbolsRead)
 246     return LDPS_OK;
 247
 248   if (!get_input_file) {
 249     message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
 250     return LDPS_ERR;
 251   }
 252   if (!release_input_file) {
 253     message(LDPL_ERROR, "relesase_input_file not passed to LLVMgold.");
 254     return LDPS_ERR;
 255   }
 256
 257   return LDPS_OK;
 258 }
 259
 260 static const GlobalObject *getBaseObject(const GlobalValue &GV) {
 261   if (auto *GA = dyn_cast<GlobalAlias>(&GV))
 262     return GA->getBaseObject();
 263   return cast<GlobalObject>(&GV);
 264 }
 265
 266 static bool shouldSkip(uint32_t Symflags) {
 267   if (!(Symflags & object::BasicSymbolRef::SF_Global))
 268     return true;
 269   if (Symflags & object::BasicSymbolRef::SF_FormatSpecific)
 270     return true;
 271   return false;
 272 }
 273
 274 static void diagnosticHandler(const DiagnosticInfo &DI, void *Context) {
 275   assert(DI.getSeverity() == DS_Error && "Only expecting errors");
 276   const auto &BDI = cast<BitcodeDiagnosticInfo>(DI);
 277   std::error_code EC = BDI.getError();
 278   if (EC == BitcodeError::InvalidBitcodeSignature)
 279     return;
 280
 281   std::string ErrStorage;
 282   {
 283     raw_string_ostream OS(ErrStorage);
 284     DiagnosticPrinterRawOStream DP(OS);
 285     DI.print(DP);
 286   }
 287   message(LDPL_FATAL, "LLVM gold plugin has failed to create LTO module: %s",
 288           ErrStorage.c_str());
 289 }
 290
 291 /// Called by gold to see whether this file is one that our plugin can handle.
 292 /// We'll try to open it and register all the symbols with add_symbol if
 293 /// possible.
 294 static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
 295                                         int *claimed) {
 296   LLVMContext Context;
 297   MemoryBufferRef BufferRef;
 298   std::unique_ptr<MemoryBuffer> Buffer;
 299   if (get_view) {
 300     const void *view;
 301     if (get_view(file->handle, &view) != LDPS_OK) {
 302       message(LDPL_ERROR, "Failed to get a view of %s", file->name);
 303       return LDPS_ERR;
 304     }
 305     BufferRef = MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
 306   } else {
 307     int64_t offset = 0;
 308     // Gold has found what might be IR part-way inside of a file, such as
 309     // an .a archive.
 310     if (file->offset) {
 311       offset = file->offset;
 312     }
 313     ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
 314         MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
 315                                        offset);
 316     if (std::error_code EC = BufferOrErr.getError()) {
 317       message(LDPL_ERROR, EC.message().c_str());
 318       return LDPS_ERR;
 319     }
 320     Buffer = std::move(BufferOrErr.get());
 321     BufferRef = Buffer->getMemBufferRef();
 322   }
 323
 324   Context.setDiagnosticHandler(diagnosticHandler);
 325   ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
 326       object::IRObjectFile::create(BufferRef, Context);
 327   std::error_code EC = ObjOrErr.getError();
 328   if (EC == object::object_error::invalid_file_type ||
 329       EC == object::object_error::bitcode_section_not_found)
 330     return LDPS_OK;
 331
 332   *claimed = 1;
 333
 334   if (EC) {
 335     message(LDPL_ERROR, "LLVM gold plugin has failed to create LTO module: %s",
 336             EC.message().c_str());
 337     return LDPS_ERR;
 338   }
 339   std::unique_ptr<object::IRObjectFile> Obj = std::move(*ObjOrErr);
 340
 341   Modules.resize(Modules.size() + 1);
 342   claimed_file &cf = Modules.back();
 343
 344   cf.handle = file->handle;
 345
 346   for (auto &Sym : Obj->symbols()) {
 347     uint32_t Symflags = Sym.getFlags();
 348     if (shouldSkip(Symflags))
 349       continue;
 350
 351     cf.syms.push_back(ld_plugin_symbol());
 352     ld_plugin_symbol &sym = cf.syms.back();
 353     sym.version = nullptr;
 354
 355     SmallString<64> Name;
 356     {
 357       raw_svector_ostream OS(Name);
 358       Sym.printName(OS);
 359     }
 360     sym.name = strdup(Name.c_str());
 361
 362     const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
 363
 364     sym.visibility = LDPV_DEFAULT;
 365     if (GV) {
 366       switch (GV->getVisibility()) {
 367       case GlobalValue::DefaultVisibility:
 368         sym.visibility = LDPV_DEFAULT;
 369         break;
 370       case GlobalValue::HiddenVisibility:
 371         sym.visibility = LDPV_HIDDEN;
 372         break;
 373       case GlobalValue::ProtectedVisibility:
 374         sym.visibility = LDPV_PROTECTED;
 375         break;
 376       }
 377     }
 378
 379     if (Symflags & object::BasicSymbolRef::SF_Undefined) {
 380       sym.def = LDPK_UNDEF;
 381       if (GV && GV->hasExternalWeakLinkage())
 382         sym.def = LDPK_WEAKUNDEF;
 383     } else {
 384       sym.def = LDPK_DEF;
 385       if (GV) {
 386         assert(!GV->hasExternalWeakLinkage() &&
 387                !GV->hasAvailableExternallyLinkage() && "Not a declaration!");
 388         if (GV->hasCommonLinkage())
 389           sym.def = LDPK_COMMON;
 390         else if (GV->isWeakForLinker())
 391           sym.def = LDPK_WEAKDEF;
 392       }
 393     }
 394
 395     sym.size = 0;
 396     sym.comdat_key = nullptr;
 397     if (GV) {
 398       const GlobalObject *Base = getBaseObject(*GV);
 399       if (!Base)
 400         message(LDPL_FATAL, "Unable to determine comdat of alias!");
 401       const Comdat *C = Base->getComdat();
 402       if (C)
 403         sym.comdat_key = strdup(C->getName().str().c_str());
 404       else if (Base->hasWeakLinkage() || Base->hasLinkOnceLinkage())
 405         sym.comdat_key = strdup(sym.name);
 406     }
 407
 408     sym.resolution = LDPR_UNKNOWN;
 409   }
 410
 411   if (!cf.syms.empty()) {
 412     if (add_symbols(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
 413       message(LDPL_ERROR, "Unable to add symbols!");
 414       return LDPS_ERR;
 415     }
 416   }
 417
 418   return LDPS_OK;
 419 }
 420
 421 static void keepGlobalValue(GlobalValue &GV,
 422                             std::vector<GlobalAlias *> &KeptAliases) {
 423   assert(!GV.hasLocalLinkage());
 424
 425   if (auto *GA = dyn_cast<GlobalAlias>(&GV))
 426     KeptAliases.push_back(GA);
 427
 428   switch (GV.getLinkage()) {
 429   default:
 430     break;
 431   case GlobalValue::LinkOnceAnyLinkage:
 432     GV.setLinkage(GlobalValue::WeakAnyLinkage);
 433     break;
 434   case GlobalValue::LinkOnceODRLinkage:
 435     GV.setLinkage(GlobalValue::WeakODRLinkage);
 436     break;
 437   }
 438
 439   assert(!GV.isDiscardableIfUnused());
 440 }
 441
 442 static void internalize(GlobalValue &GV) {
 443   if (GV.isDeclarationForLinker())
 444     return; // We get here if there is a matching asm definition.
 445   if (!GV.hasLocalLinkage())
 446     GV.setLinkage(GlobalValue::InternalLinkage);
 447 }
 448
 449 static void drop(GlobalValue &GV) {
 450   if (auto *F = dyn_cast<Function>(&GV)) {
 451     F->deleteBody();
 452     F->setComdat(nullptr); // Should deleteBody do this?
 453     return;
 454   }
 455
 456   if (auto *Var = dyn_cast<GlobalVariable>(&GV)) {
 457     Var->setInitializer(nullptr);
 458     Var->setLinkage(
 459         GlobalValue::ExternalLinkage); // Should setInitializer do this?
 460     Var->setComdat(nullptr); // and this?
 461     return;
 462   }
 463
 464   auto &Alias = cast<GlobalAlias>(GV);
 465   Module &M = *Alias.getParent();
 466   PointerType &Ty = *cast<PointerType>(Alias.getType());
 467   GlobalValue::LinkageTypes L = Alias.getLinkage();
 468   auto *Var =
 469       new GlobalVariable(M, Ty.getElementType(), /*isConstant*/ false, L,
 470                          /*Initializer*/ nullptr);
 471   Var->takeName(&Alias);
 472   Alias.replaceAllUsesWith(Var);
 473   Alias.eraseFromParent();
 474 }
 475
 476 static const char *getResolutionName(ld_plugin_symbol_resolution R) {
 477   switch (R) {
 478   case LDPR_UNKNOWN:
 479     return "UNKNOWN";
 480   case LDPR_UNDEF:
 481     return "UNDEF";
 482   case LDPR_PREVAILING_DEF:
 483     return "PREVAILING_DEF";
 484   case LDPR_PREVAILING_DEF_IRONLY:
 485     return "PREVAILING_DEF_IRONLY";
 486   case LDPR_PREEMPTED_REG:
 487     return "PREEMPTED_REG";
 488   case LDPR_PREEMPTED_IR:
 489     return "PREEMPTED_IR";
 490   case LDPR_RESOLVED_IR:
 491     return "RESOLVED_IR";
 492   case LDPR_RESOLVED_EXEC:
 493     return "RESOLVED_EXEC";
 494   case LDPR_RESOLVED_DYN:
 495     return "RESOLVED_DYN";
 496   case LDPR_PREVAILING_DEF_IRONLY_EXP:
 497     return "PREVAILING_DEF_IRONLY_EXP";
 498   }
 499   llvm_unreachable("Unknown resolution");
 500 }
 501
 502 namespace {
 503 class LocalValueMaterializer : public ValueMaterializer {
 504   DenseSet<GlobalValue *> &Dropped;
 505   DenseMap<GlobalObject *, GlobalObject *> LocalVersions;
 506
 507 public:
 508   LocalValueMaterializer(DenseSet<GlobalValue *> &Dropped) : Dropped(Dropped) {}
 509   Value *materializeValueFor(Value *V) override;
 510 };
 511 }
 512
 513 Value *LocalValueMaterializer::materializeValueFor(Value *V) {
 514   auto *GO = dyn_cast<GlobalObject>(V);
 515   if (!GO)
 516     return nullptr;
 517
 518   auto I = LocalVersions.find(GO);
 519   if (I != LocalVersions.end())
 520     return I->second;
 521
 522   if (!Dropped.count(GO))
 523     return nullptr;
 524
 525   Module &M = *GO->getParent();
 526   GlobalValue::LinkageTypes L = GO->getLinkage();
 527   GlobalObject *Declaration;
 528   if (auto *F = dyn_cast<Function>(GO)) {
 529     Declaration = Function::Create(F->getFunctionType(), L, "", &M);
 530   } else {
 531     auto *Var = cast<GlobalVariable>(GO);
 532     Declaration = new GlobalVariable(M, Var->getType()->getElementType(),
 533                                      Var->isConstant(), L,
 534                                      /*Initializer*/ nullptr);
 535   }
 536   Declaration->takeName(GO);
 537   Declaration->copyAttributesFrom(GO);
 538
 539   GO->setLinkage(GlobalValue::InternalLinkage);
 540   GO->setName(Declaration->getName());
 541   Dropped.erase(GO);
 542   GO->replaceAllUsesWith(Declaration);
 543
 544   LocalVersions[Declaration] = GO;
 545
 546   return GO;
 547 }
 548
 549 static Constant *mapConstantToLocalCopy(Constant *C, ValueToValueMapTy &VM,
 550                                         LocalValueMaterializer *Materializer) {
 551   return MapValue(C, VM, RF_IgnoreMissingEntries, nullptr, Materializer);
 552 }
 553
 554 static void freeSymName(ld_plugin_symbol &Sym) {
 555   free(Sym.name);
 556   free(Sym.comdat_key);
 557   Sym.name = nullptr;
 558   Sym.comdat_key = nullptr;
 559 }
 560
 561 static std::unique_ptr<Module>
 562 getModuleForFile(LLVMContext &Context, claimed_file &F,
 563                  off_t Filesize, raw_fd_ostream *ApiFile,
 564                  StringSet<> &Internalize, StringSet<> &Maybe) {
 565
 566   if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
 567     message(LDPL_FATAL, "Failed to get symbol information");
 568
 569   const void *View;
 570   if (get_view(F.handle, &View) != LDPS_OK)
 571     message(LDPL_FATAL, "Failed to get a view of file");
 572
 573   MemoryBufferRef BufferRef(StringRef((const char *)View, Filesize), "");
 574   ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
 575       object::IRObjectFile::create(BufferRef, Context);
 576
 577   if (std::error_code EC = ObjOrErr.getError())
 578     message(LDPL_FATAL, "Could not read bitcode from file : %s",
 579             EC.message().c_str());
 580
 581   object::IRObjectFile &Obj = **ObjOrErr;
 582
 583   Module &M = Obj.getModule();
 584
 585   SmallPtrSet<GlobalValue *, 8> Used;
 586   collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
 587
 588   DenseSet<GlobalValue *> Drop;
 589   std::vector<GlobalAlias *> KeptAliases;
 590
 591   unsigned SymNum = 0;
 592   for (auto &ObjSym : Obj.symbols()) {
 593     if (shouldSkip(ObjSym.getFlags()))
 594       continue;
 595     ld_plugin_symbol &Sym = F.syms[SymNum];
 596     ++SymNum;
 597
 598     ld_plugin_symbol_resolution Resolution =
 599         (ld_plugin_symbol_resolution)Sym.resolution;
 600
 601     if (options::generate_api_file)
 602       *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';
 603
 604     GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
 605     if (!GV) {
 606       freeSymName(Sym);
 607       continue; // Asm symbol.
 608     }
 609
 610     if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
 611       // Common linkage is special. There is no single symbol that wins the
 612       // resolution. Instead we have to collect the maximum alignment and size.
 613       // The IR linker does that for us if we just pass it every common GV.
 614       // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
 615       // internalize once the IR linker has done its job.
 616       freeSymName(Sym);
 617       continue;
 618     }
 619
 620     switch (Resolution) {
 621     case LDPR_UNKNOWN:
 622       llvm_unreachable("Unexpected resolution");
 623
 624     case LDPR_RESOLVED_IR:
 625     case LDPR_RESOLVED_EXEC:
 626     case LDPR_RESOLVED_DYN:
 627       assert(GV->isDeclarationForLinker());
 628       break;
 629
 630     case LDPR_UNDEF:
 631       if (!GV->isDeclarationForLinker()) {
 632         assert(GV->hasComdat());
 633         Drop.insert(GV);
 634       }
 635       break;
 636
 637     case LDPR_PREVAILING_DEF_IRONLY: {
 638       keepGlobalValue(*GV, KeptAliases);
 639       if (!Used.count(GV)) {
 640         // Since we use the regular lib/Linker, we cannot just internalize GV
 641         // now or it will not be copied to the merged module. Instead we force
 642         // it to be copied and then internalize it.
 643         Internalize.insert(GV->getName());
 644       }
 645       break;
 646     }
 647
 648     case LDPR_PREVAILING_DEF:
 649       keepGlobalValue(*GV, KeptAliases);
 650       break;
 651
 652     case LDPR_PREEMPTED_IR:
 653       // Gold might have selected a linkonce_odr and preempted a weak_odr.
 654       // In that case we have to make sure we don't end up internalizing it.
 655       if (!GV->isDiscardableIfUnused())
 656         Maybe.erase(GV->getName());
 657
 658       // fall-through
 659     case LDPR_PREEMPTED_REG:
 660       Drop.insert(GV);
 661       break;
 662
 663     case LDPR_PREVAILING_DEF_IRONLY_EXP: {
 664       // We can only check for address uses after we merge the modules. The
 665       // reason is that this GV might have a copy in another module
 666       // and in that module the address might be significant, but that
 667       // copy will be LDPR_PREEMPTED_IR.
 668       if (GV->hasLinkOnceODRLinkage())
 669         Maybe.insert(GV->getName());
 670       keepGlobalValue(*GV, KeptAliases);
 671       break;
 672     }
 673     }
 674
 675     freeSymName(Sym);
 676   }
 677
 678   ValueToValueMapTy VM;
 679   LocalValueMaterializer Materializer(Drop);
 680   for (GlobalAlias *GA : KeptAliases) {
 681     // Gold told us to keep GA. It is possible that a GV usied in the aliasee
 682     // expression is being dropped. If that is the case, that GV must be copied.
 683     Constant *Aliasee = GA->getAliasee();
 684     Constant *Replacement = mapConstantToLocalCopy(Aliasee, VM, &Materializer);
 685     GA->setAliasee(Replacement);
 686   }
 687
 688   for (auto *GV : Drop)
 689     drop(*GV);
 690
 691   return Obj.takeModule();
 692 }
 693
 694 static void runLTOPasses(Module &M, TargetMachine &TM) {
 695   PassManager passes;
 696   PassManagerBuilder PMB;
 697   PMB.LibraryInfo = new TargetLibraryInfo(Triple(TM.getTargetTriple()));
 698   PMB.Inliner = createFunctionInliningPass();
 699   PMB.VerifyInput = true;
 700   PMB.VerifyOutput = true;
 701   PMB.LoopVectorize = true;
 702   PMB.SLPVectorize = true;
 703   PMB.populateLTOPassManager(passes, &TM);
 704   passes.run(M);
 705 }
 706
 707 static void saveBCFile(StringRef Path, Module &M) {
 708   std::error_code EC;
 709   raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
 710   if (EC)
 711     message(LDPL_FATAL, "Failed to write the output file.");
 712   WriteBitcodeToFile(&M, OS);
 713 }
 714
 715 static void codegen(Module &M) {
 716   const std::string &TripleStr = M.getTargetTriple();
 717   Triple TheTriple(TripleStr);
 718
 719   std::string ErrMsg;
 720   const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
 721   if (!TheTarget)
 722     message(LDPL_FATAL, "Target not found: %s", ErrMsg.c_str());
 723
 724   if (unsigned NumOpts = options::extra.size())
 725     cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
 726
 727   SubtargetFeatures Features;
 728   Features.getDefaultSubtargetFeatures(TheTriple);
 729   for (const std::string &A : MAttrs)
 730     Features.AddFeature(A);
 731
 732   TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
 733   std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
 734       TripleStr, options::mcpu, Features.getString(), Options, RelocationModel,
 735       CodeModel::Default, CodeGenOpt::Aggressive));
 736
 737   runLTOPasses(M, *TM);
 738
 739   if (options::TheOutputType == options::OT_SAVE_TEMPS)
 740     saveBCFile(output_name + ".opt.bc", M);
 741
 742   PassManager CodeGenPasses;
 743   CodeGenPasses.add(new DataLayoutPass());
 744
 745   SmallString<128> Filename;
 746   int FD;
 747   if (options::obj_path.empty()) {
 748     std::error_code EC =
 749         sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
 750     if (EC)
 751       message(LDPL_FATAL, "Could not create temporary file: %s",
 752               EC.message().c_str());
 753   } else {
 754     Filename = options::obj_path;
 755     std::error_code EC =
 756         sys::fs::openFileForWrite(Filename.c_str(), FD, sys::fs::F_None);
 757     if (EC)
 758       message(LDPL_FATAL, "Could not open file: %s", EC.message().c_str());
 759   }
 760
 761   {
 762     raw_fd_ostream OS(FD, true);
 763     formatted_raw_ostream FOS(OS);
 764
 765     if (TM->addPassesToEmitFile(CodeGenPasses, FOS,
 766                                 TargetMachine::CGFT_ObjectFile))
 767       message(LDPL_FATAL, "Failed to setup codegen");
 768     CodeGenPasses.run(M);
 769   }
 770
 771   if (add_input_file(Filename.c_str()) != LDPS_OK)
 772     message(LDPL_FATAL,
 773             "Unable to add .o file to the link. File left behind in: %s",
 774             Filename.c_str());
 775
 776   if (options::obj_path.empty())
 777     Cleanup.push_back(Filename.c_str());
 778 }
 779
 780 /// gold informs us that all symbols have been read. At this point, we use
 781 /// get_symbols to see if any of our definitions have been overridden by a
 782 /// native object file. Then, perform optimization and codegen.
 783 static ld_plugin_status allSymbolsReadHook(raw_fd_ostream *ApiFile) {
 784   if (Modules.empty())
 785     return LDPS_OK;
 786
 787   LLVMContext Context;
 788   std::unique_ptr<Module> Combined(new Module("ld-temp.o", Context));
 789   Linker L(Combined.get());
 790
 791   std::string DefaultTriple = sys::getDefaultTargetTriple();
 792
 793   StringSet<> Internalize;
 794   StringSet<> Maybe;
 795   for (claimed_file &F : Modules) {
 796     ld_plugin_input_file File;
 797     if (get_input_file(F.handle, &File) != LDPS_OK)
 798       message(LDPL_FATAL, "Failed to get file information");
 799     std::unique_ptr<Module> M =
 800         getModuleForFile(Context, F, File.filesize, ApiFile,
 801                          Internalize, Maybe);
 802     if (!options::triple.empty())
 803       M->setTargetTriple(options::triple.c_str());
 804     else if (M->getTargetTriple().empty()) {
 805       M->setTargetTriple(DefaultTriple);
 806     }
 807
 808     if (L.linkInModule(M.get()))
 809       message(LDPL_FATAL, "Failed to link module");
 810     if (release_input_file(F.handle) != LDPS_OK)
 811       message(LDPL_FATAL, "Failed to release file information");
 812   }
 813
 814   for (const auto &Name : Internalize) {
 815     GlobalValue *GV = Combined->getNamedValue(Name.first());
 816     if (GV)
 817       internalize(*GV);
 818   }
 819
 820   for (const auto &Name : Maybe) {
 821     GlobalValue *GV = Combined->getNamedValue(Name.first());
 822     if (!GV)
 823       continue;
 824     GV->setLinkage(GlobalValue::LinkOnceODRLinkage);
 825     if (canBeOmittedFromSymbolTable(GV))
 826       internalize(*GV);
 827   }
 828
 829   if (options::TheOutputType == options::OT_DISABLE)
 830     return LDPS_OK;
 831
 832   if (options::TheOutputType != options::OT_NORMAL) {
 833     std::string path;
 834     if (options::TheOutputType == options::OT_BC_ONLY)
 835       path = output_name;
 836     else
 837       path = output_name + ".bc";
 838     saveBCFile(path, *L.getModule());
 839     if (options::TheOutputType == options::OT_BC_ONLY)
 840       return LDPS_OK;
 841   }
 842
 843   codegen(*L.getModule());
 844
 845   if (!options::extra_library_path.empty() &&
 846       set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
 847     message(LDPL_FATAL, "Unable to set the extra library path.");
 848
 849   return LDPS_OK;
 850 }
 851
 852 static ld_plugin_status all_symbols_read_hook(void) {
 853   ld_plugin_status Ret;
 854   if (!options::generate_api_file) {
 855     Ret = allSymbolsReadHook(nullptr);
 856   } else {
 857     std::error_code EC;
 858     raw_fd_ostream ApiFile("apifile.txt", EC, sys::fs::F_None);
 859     if (EC)
 860       message(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
 861               EC.message().c_str());
 862     Ret = allSymbolsReadHook(&ApiFile);
 863   }
 864
 865   llvm_shutdown();
 866
 867   if (options::TheOutputType == options::OT_BC_ONLY ||
 868       options::TheOutputType == options::OT_DISABLE)
 869     exit(0);
 870
 871   return Ret;
 872 }
 873
 874 static ld_plugin_status cleanup_hook(void) {
 875   for (std::string &Name : Cleanup) {
 876     std::error_code EC = sys::fs::remove(Name);
 877     if (EC)
 878       message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
 879               EC.message().c_str());
 880   }
 881
 882   return LDPS_OK;
 883 }