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/Analysis/TargetLibraryInfo.h"
19#include "llvm/Analysis/TargetTransformInfo.h"
20#include "llvm/Bitcode/ReaderWriter.h"
21#include "llvm/CodeGen/Analysis.h"
22#include "llvm/CodeGen/CommandFlags.h"
23#include "llvm/IR/AutoUpgrade.h"
24#include "llvm/IR/Constants.h"
25#include "llvm/IR/DiagnosticInfo.h"
26#include "llvm/IR/DiagnosticPrinter.h"
27#include "llvm/IR/LLVMContext.h"
28#include "llvm/IR/LegacyPassManager.h"
29#include "llvm/IR/Module.h"
30#include "llvm/IR/Verifier.h"
31#include "llvm/Linker/Linker.h"
32#include "llvm/MC/SubtargetFeature.h"
33#include "llvm/Object/IRObjectFile.h"
34#include "llvm/Support/raw_ostream.h"
35#include "llvm/Support/Host.h"
36#include "llvm/Support/ManagedStatic.h"
37#include "llvm/Support/MemoryBuffer.h"
38#include "llvm/Support/TargetRegistry.h"
39#include "llvm/Support/TargetSelect.h"
40#include "llvm/Transforms/IPO.h"
41#include "llvm/Transforms/IPO/PassManagerBuilder.h"
42#include "llvm/Transforms/Utils/GlobalStatus.h"
43#include "llvm/Transforms/Utils/ModuleUtils.h"
44#include "llvm/Transforms/Utils/ValueMapper.h"
45#include <list>
46#include <plugin-api.h>
47#include <system_error>
48#include <vector>
49
50#ifndef LDPO_PIE
51// FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
52// Precise and Debian Wheezy (binutils 2.23 is required)
53# define LDPO_PIE 3
54#endif
55
56using namespace llvm;
57
58namespace {
59struct claimed_file {
60  void *handle;
61  std::vector<ld_plugin_symbol> syms;
62};
63}
64
65static ld_plugin_status discard_message(int level, const char *format, ...) {
66  // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
67  // callback in the transfer vector. This should never be called.
68  abort();
69}
70
71static ld_plugin_get_input_file get_input_file = nullptr;
72static ld_plugin_release_input_file release_input_file = nullptr;
73static ld_plugin_add_symbols add_symbols = nullptr;
74static ld_plugin_get_symbols get_symbols = nullptr;
75static ld_plugin_add_input_file add_input_file = nullptr;
76static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
77static ld_plugin_get_view get_view = nullptr;
78static ld_plugin_message message = discard_message;
79static Reloc::Model RelocationModel = Reloc::Default;
80static std::string output_name = "";
81static std::list<claimed_file> Modules;
82static std::vector<std::string> Cleanup;
83static llvm::TargetOptions TargetOpts;
84
85namespace options {
86  enum OutputType {
87    OT_NORMAL,
88    OT_DISABLE,
89    OT_BC_ONLY,
90    OT_SAVE_TEMPS
91  };
92  static bool generate_api_file = false;
93  static OutputType TheOutputType = OT_NORMAL;
94  static unsigned OptLevel = 2;
95  static std::string obj_path;
96  static std::string extra_library_path;
97  static std::string triple;
98  static std::string mcpu;
99  // Additional options to pass into the code generator.
100  // Note: This array will contain all plugin options which are not claimed
101  // as plugin exclusive to pass to the code generator.
102  // For example, "generate-api-file" and "as"options are for the plugin
103  // use only and will not be passed.
104  static std::vector<const char *> extra;
105
106  static void process_plugin_option(const char* opt_)
107  {
108    if (opt_ == nullptr)
109      return;
110    llvm::StringRef opt = opt_;
111
112    if (opt == "generate-api-file") {
113      generate_api_file = true;
114    } else if (opt.startswith("mcpu=")) {
115      mcpu = opt.substr(strlen("mcpu="));
116    } else if (opt.startswith("extra-library-path=")) {
117      extra_library_path = opt.substr(strlen("extra_library_path="));
118    } else if (opt.startswith("mtriple=")) {
119      triple = opt.substr(strlen("mtriple="));
120    } else if (opt.startswith("obj-path=")) {
121      obj_path = opt.substr(strlen("obj-path="));
122    } else if (opt == "emit-llvm") {
123      TheOutputType = OT_BC_ONLY;
124    } else if (opt == "save-temps") {
125      TheOutputType = OT_SAVE_TEMPS;
126    } else if (opt == "disable-output") {
127      TheOutputType = OT_DISABLE;
128    } else if (opt.size() == 2 && opt[0] == 'O') {
129      if (opt[1] < '0' || opt[1] > '3')
130        report_fatal_error("Optimization level must be between 0 and 3");
131      OptLevel = opt[1] - '0';
132    } else {
133      // Save this option to pass to the code generator.
134      // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
135      // add that.
136      if (extra.empty())
137        extra.push_back("LLVMgold");
138
139      extra.push_back(opt_);
140    }
141  }
142}
143
144static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
145                                        int *claimed);
146static ld_plugin_status all_symbols_read_hook(void);
147static ld_plugin_status cleanup_hook(void);
148
149extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
150ld_plugin_status onload(ld_plugin_tv *tv) {
151  InitializeAllTargetInfos();
152  InitializeAllTargets();
153  InitializeAllTargetMCs();
154  InitializeAllAsmParsers();
155  InitializeAllAsmPrinters();
156
157  // We're given a pointer to the first transfer vector. We read through them
158  // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
159  // contain pointers to functions that we need to call to register our own
160  // hooks. The others are addresses of functions we can use to call into gold
161  // for services.
162
163  bool registeredClaimFile = false;
164  bool RegisteredAllSymbolsRead = false;
165
166  for (; tv->tv_tag != LDPT_NULL; ++tv) {
167    switch (tv->tv_tag) {
168      case LDPT_OUTPUT_NAME:
169        output_name = tv->tv_u.tv_string;
170        break;
171      case LDPT_LINKER_OUTPUT:
172        switch (tv->tv_u.tv_val) {
173          case LDPO_REL:  // .o
174          case LDPO_DYN:  // .so
175          case LDPO_PIE:  // position independent executable
176            RelocationModel = Reloc::PIC_;
177            break;
178          case LDPO_EXEC:  // .exe
179            RelocationModel = Reloc::Static;
180            break;
181          default:
182            message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
183            return LDPS_ERR;
184        }
185        break;
186      case LDPT_OPTION:
187        options::process_plugin_option(tv->tv_u.tv_string);
188        break;
189      case LDPT_REGISTER_CLAIM_FILE_HOOK: {
190        ld_plugin_register_claim_file callback;
191        callback = tv->tv_u.tv_register_claim_file;
192
193        if (callback(claim_file_hook) != LDPS_OK)
194          return LDPS_ERR;
195
196        registeredClaimFile = true;
197      } break;
198      case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
199        ld_plugin_register_all_symbols_read callback;
200        callback = tv->tv_u.tv_register_all_symbols_read;
201
202        if (callback(all_symbols_read_hook) != LDPS_OK)
203          return LDPS_ERR;
204
205        RegisteredAllSymbolsRead = true;
206      } break;
207      case LDPT_REGISTER_CLEANUP_HOOK: {
208        ld_plugin_register_cleanup callback;
209        callback = tv->tv_u.tv_register_cleanup;
210
211        if (callback(cleanup_hook) != LDPS_OK)
212          return LDPS_ERR;
213      } break;
214      case LDPT_GET_INPUT_FILE:
215        get_input_file = tv->tv_u.tv_get_input_file;
216        break;
217      case LDPT_RELEASE_INPUT_FILE:
218        release_input_file = tv->tv_u.tv_release_input_file;
219        break;
220      case LDPT_ADD_SYMBOLS:
221        add_symbols = tv->tv_u.tv_add_symbols;
222        break;
223      case LDPT_GET_SYMBOLS_V2:
224        get_symbols = tv->tv_u.tv_get_symbols;
225        break;
226      case LDPT_ADD_INPUT_FILE:
227        add_input_file = tv->tv_u.tv_add_input_file;
228        break;
229      case LDPT_SET_EXTRA_LIBRARY_PATH:
230        set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
231        break;
232      case LDPT_GET_VIEW:
233        get_view = tv->tv_u.tv_get_view;
234        break;
235      case LDPT_MESSAGE:
236        message = tv->tv_u.tv_message;
237        break;
238      default:
239        break;
240    }
241  }
242
243  if (!registeredClaimFile) {
244    message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
245    return LDPS_ERR;
246  }
247  if (!add_symbols) {
248    message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
249    return LDPS_ERR;
250  }
251
252  if (!RegisteredAllSymbolsRead)
253    return LDPS_OK;
254
255  if (!get_input_file) {
256    message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
257    return LDPS_ERR;
258  }
259  if (!release_input_file) {
260    message(LDPL_ERROR, "relesase_input_file not passed to LLVMgold.");
261    return LDPS_ERR;
262  }
263
264  return LDPS_OK;
265}
266
267static const GlobalObject *getBaseObject(const GlobalValue &GV) {
268  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
269    return GA->getBaseObject();
270  return cast<GlobalObject>(&GV);
271}
272
273static bool shouldSkip(uint32_t Symflags) {
274  if (!(Symflags & object::BasicSymbolRef::SF_Global))
275    return true;
276  if (Symflags & object::BasicSymbolRef::SF_FormatSpecific)
277    return true;
278  return false;
279}
280
281static void diagnosticHandler(const DiagnosticInfo &DI, void *Context) {
282  if (const auto *BDI = dyn_cast<BitcodeDiagnosticInfo>(&DI)) {
283    std::error_code EC = BDI->getError();
284    if (EC == BitcodeError::InvalidBitcodeSignature)
285      return;
286  }
287
288  std::string ErrStorage;
289  {
290    raw_string_ostream OS(ErrStorage);
291    DiagnosticPrinterRawOStream DP(OS);
292    DI.print(DP);
293  }
294  ld_plugin_level Level;
295  switch (DI.getSeverity()) {
296  case DS_Error:
297    message(LDPL_FATAL, "LLVM gold plugin has failed to create LTO module: %s",
298            ErrStorage.c_str());
299    llvm_unreachable("Fatal doesn't return.");
300  case DS_Warning:
301    Level = LDPL_WARNING;
302    break;
303  case DS_Note:
304  case DS_Remark:
305    Level = LDPL_INFO;
306    break;
307  }
308  message(Level, "LLVM gold plugin: %s",  ErrStorage.c_str());
309}
310
311/// Called by gold to see whether this file is one that our plugin can handle.
312/// We'll try to open it and register all the symbols with add_symbol if
313/// possible.
314static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
315                                        int *claimed) {
316  LLVMContext Context;
317  MemoryBufferRef BufferRef;
318  std::unique_ptr<MemoryBuffer> Buffer;
319  if (get_view) {
320    const void *view;
321    if (get_view(file->handle, &view) != LDPS_OK) {
322      message(LDPL_ERROR, "Failed to get a view of %s", file->name);
323      return LDPS_ERR;
324    }
325    BufferRef = MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
326  } else {
327    int64_t offset = 0;
328    // Gold has found what might be IR part-way inside of a file, such as
329    // an .a archive.
330    if (file->offset) {
331      offset = file->offset;
332    }
333    ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
334        MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
335                                       offset);
336    if (std::error_code EC = BufferOrErr.getError()) {
337      message(LDPL_ERROR, EC.message().c_str());
338      return LDPS_ERR;
339    }
340    Buffer = std::move(BufferOrErr.get());
341    BufferRef = Buffer->getMemBufferRef();
342  }
343
344  Context.setDiagnosticHandler(diagnosticHandler);
345  ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
346      object::IRObjectFile::create(BufferRef, Context);
347  std::error_code EC = ObjOrErr.getError();
348  if (EC == object::object_error::invalid_file_type ||
349      EC == object::object_error::bitcode_section_not_found)
350    return LDPS_OK;
351
352  *claimed = 1;
353
354  if (EC) {
355    message(LDPL_ERROR, "LLVM gold plugin has failed to create LTO module: %s",
356            EC.message().c_str());
357    return LDPS_ERR;
358  }
359  std::unique_ptr<object::IRObjectFile> Obj = std::move(*ObjOrErr);
360
361  Modules.resize(Modules.size() + 1);
362  claimed_file &cf = Modules.back();
363
364  cf.handle = file->handle;
365
366  for (auto &Sym : Obj->symbols()) {
367    uint32_t Symflags = Sym.getFlags();
368    if (shouldSkip(Symflags))
369      continue;
370
371    cf.syms.push_back(ld_plugin_symbol());
372    ld_plugin_symbol &sym = cf.syms.back();
373    sym.version = nullptr;
374
375    SmallString<64> Name;
376    {
377      raw_svector_ostream OS(Name);
378      Sym.printName(OS);
379    }
380    sym.name = strdup(Name.c_str());
381
382    const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());
383
384    sym.visibility = LDPV_DEFAULT;
385    if (GV) {
386      switch (GV->getVisibility()) {
387      case GlobalValue::DefaultVisibility:
388        sym.visibility = LDPV_DEFAULT;
389        break;
390      case GlobalValue::HiddenVisibility:
391        sym.visibility = LDPV_HIDDEN;
392        break;
393      case GlobalValue::ProtectedVisibility:
394        sym.visibility = LDPV_PROTECTED;
395        break;
396      }
397    }
398
399    if (Symflags & object::BasicSymbolRef::SF_Undefined) {
400      sym.def = LDPK_UNDEF;
401      if (GV && GV->hasExternalWeakLinkage())
402        sym.def = LDPK_WEAKUNDEF;
403    } else {
404      sym.def = LDPK_DEF;
405      if (GV) {
406        assert(!GV->hasExternalWeakLinkage() &&
407               !GV->hasAvailableExternallyLinkage() && "Not a declaration!");
408        if (GV->hasCommonLinkage())
409          sym.def = LDPK_COMMON;
410        else if (GV->isWeakForLinker())
411          sym.def = LDPK_WEAKDEF;
412      }
413    }
414
415    sym.size = 0;
416    sym.comdat_key = nullptr;
417    if (GV) {
418      const GlobalObject *Base = getBaseObject(*GV);
419      if (!Base)
420        message(LDPL_FATAL, "Unable to determine comdat of alias!");
421      const Comdat *C = Base->getComdat();
422      if (C)
423        sym.comdat_key = strdup(C->getName().str().c_str());
424      else if (Base->hasWeakLinkage() || Base->hasLinkOnceLinkage())
425        sym.comdat_key = strdup(sym.name);
426    }
427
428    sym.resolution = LDPR_UNKNOWN;
429  }
430
431  if (!cf.syms.empty()) {
432    if (add_symbols(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
433      message(LDPL_ERROR, "Unable to add symbols!");
434      return LDPS_ERR;
435    }
436  }
437
438  return LDPS_OK;
439}
440
441static void keepGlobalValue(GlobalValue &GV,
442                            std::vector<GlobalAlias *> &KeptAliases) {
443  assert(!GV.hasLocalLinkage());
444
445  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
446    KeptAliases.push_back(GA);
447
448  switch (GV.getLinkage()) {
449  default:
450    break;
451  case GlobalValue::LinkOnceAnyLinkage:
452    GV.setLinkage(GlobalValue::WeakAnyLinkage);
453    break;
454  case GlobalValue::LinkOnceODRLinkage:
455    GV.setLinkage(GlobalValue::WeakODRLinkage);
456    break;
457  }
458
459  assert(!GV.isDiscardableIfUnused());
460}
461
462static void internalize(GlobalValue &GV) {
463  if (GV.isDeclarationForLinker())
464    return; // We get here if there is a matching asm definition.
465  if (!GV.hasLocalLinkage())
466    GV.setLinkage(GlobalValue::InternalLinkage);
467}
468
469static void drop(GlobalValue &GV) {
470  if (auto *F = dyn_cast<Function>(&GV)) {
471    F->deleteBody();
472    F->setComdat(nullptr); // Should deleteBody do this?
473    return;
474  }
475
476  if (auto *Var = dyn_cast<GlobalVariable>(&GV)) {
477    Var->setInitializer(nullptr);
478    Var->setLinkage(
479        GlobalValue::ExternalLinkage); // Should setInitializer do this?
480    Var->setComdat(nullptr); // and this?
481    return;
482  }
483
484  auto &Alias = cast<GlobalAlias>(GV);
485  Module &M = *Alias.getParent();
486  PointerType &Ty = *cast<PointerType>(Alias.getType());
487  GlobalValue::LinkageTypes L = Alias.getLinkage();
488  auto *Var =
489      new GlobalVariable(M, Ty.getElementType(), /*isConstant*/ false, L,
490                         /*Initializer*/ nullptr);
491  Var->takeName(&Alias);
492  Alias.replaceAllUsesWith(Var);
493  Alias.eraseFromParent();
494}
495
496static const char *getResolutionName(ld_plugin_symbol_resolution R) {
497  switch (R) {
498  case LDPR_UNKNOWN:
499    return "UNKNOWN";
500  case LDPR_UNDEF:
501    return "UNDEF";
502  case LDPR_PREVAILING_DEF:
503    return "PREVAILING_DEF";
504  case LDPR_PREVAILING_DEF_IRONLY:
505    return "PREVAILING_DEF_IRONLY";
506  case LDPR_PREEMPTED_REG:
507    return "PREEMPTED_REG";
508  case LDPR_PREEMPTED_IR:
509    return "PREEMPTED_IR";
510  case LDPR_RESOLVED_IR:
511    return "RESOLVED_IR";
512  case LDPR_RESOLVED_EXEC:
513    return "RESOLVED_EXEC";
514  case LDPR_RESOLVED_DYN:
515    return "RESOLVED_DYN";
516  case LDPR_PREVAILING_DEF_IRONLY_EXP:
517    return "PREVAILING_DEF_IRONLY_EXP";
518  }
519  llvm_unreachable("Unknown resolution");
520}
521
522namespace {
523class LocalValueMaterializer : public ValueMaterializer {
524  DenseSet<GlobalValue *> &Dropped;
525  DenseMap<GlobalObject *, GlobalObject *> LocalVersions;
526
527public:
528  LocalValueMaterializer(DenseSet<GlobalValue *> &Dropped) : Dropped(Dropped) {}
529  Value *materializeValueFor(Value *V) override;
530};
531}
532
533Value *LocalValueMaterializer::materializeValueFor(Value *V) {
534  auto *GO = dyn_cast<GlobalObject>(V);
535  if (!GO)
536    return nullptr;
537
538  auto I = LocalVersions.find(GO);
539  if (I != LocalVersions.end())
540    return I->second;
541
542  if (!Dropped.count(GO))
543    return nullptr;
544
545  Module &M = *GO->getParent();
546  GlobalValue::LinkageTypes L = GO->getLinkage();
547  GlobalObject *Declaration;
548  if (auto *F = dyn_cast<Function>(GO)) {
549    Declaration = Function::Create(F->getFunctionType(), L, "", &M);
550  } else {
551    auto *Var = cast<GlobalVariable>(GO);
552    Declaration = new GlobalVariable(M, Var->getType()->getElementType(),
553                                     Var->isConstant(), L,
554                                     /*Initializer*/ nullptr);
555  }
556  Declaration->takeName(GO);
557  Declaration->copyAttributesFrom(GO);
558
559  GO->setLinkage(GlobalValue::InternalLinkage);
560  GO->setName(Declaration->getName());
561  Dropped.erase(GO);
562  GO->replaceAllUsesWith(Declaration);
563
564  LocalVersions[Declaration] = GO;
565
566  return GO;
567}
568
569static Constant *mapConstantToLocalCopy(Constant *C, ValueToValueMapTy &VM,
570                                        LocalValueMaterializer *Materializer) {
571  return MapValue(C, VM, RF_IgnoreMissingEntries, nullptr, Materializer);
572}
573
574static void freeSymName(ld_plugin_symbol &Sym) {
575  free(Sym.name);
576  free(Sym.comdat_key);
577  Sym.name = nullptr;
578  Sym.comdat_key = nullptr;
579}
580
581static std::unique_ptr<Module>
582getModuleForFile(LLVMContext &Context, claimed_file &F,
583                 ld_plugin_input_file &Info, raw_fd_ostream *ApiFile,
584                 StringSet<> &Internalize, StringSet<> &Maybe) {
585
586  if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
587    message(LDPL_FATAL, "Failed to get symbol information");
588
589  const void *View;
590  if (get_view(F.handle, &View) != LDPS_OK)
591    message(LDPL_FATAL, "Failed to get a view of file");
592
593  MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
594                            Info.name);
595  ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
596      object::IRObjectFile::create(BufferRef, Context);
597
598  if (std::error_code EC = ObjOrErr.getError())
599    message(LDPL_FATAL, "Could not read bitcode from file : %s",
600            EC.message().c_str());
601
602  object::IRObjectFile &Obj = **ObjOrErr;
603
604  Module &M = Obj.getModule();
605
606  M.materializeMetadata();
607  UpgradeDebugInfo(M);
608
609  SmallPtrSet<GlobalValue *, 8> Used;
610  collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);
611
612  DenseSet<GlobalValue *> Drop;
613  std::vector<GlobalAlias *> KeptAliases;
614
615  unsigned SymNum = 0;
616  for (auto &ObjSym : Obj.symbols()) {
617    if (shouldSkip(ObjSym.getFlags()))
618      continue;
619    ld_plugin_symbol &Sym = F.syms[SymNum];
620    ++SymNum;
621
622    ld_plugin_symbol_resolution Resolution =
623        (ld_plugin_symbol_resolution)Sym.resolution;
624
625    if (options::generate_api_file)
626      *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';
627
628    GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
629    if (!GV) {
630      freeSymName(Sym);
631      continue; // Asm symbol.
632    }
633
634    if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
635      // Common linkage is special. There is no single symbol that wins the
636      // resolution. Instead we have to collect the maximum alignment and size.
637      // The IR linker does that for us if we just pass it every common GV.
638      // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
639      // internalize once the IR linker has done its job.
640      freeSymName(Sym);
641      continue;
642    }
643
644    switch (Resolution) {
645    case LDPR_UNKNOWN:
646      llvm_unreachable("Unexpected resolution");
647
648    case LDPR_RESOLVED_IR:
649    case LDPR_RESOLVED_EXEC:
650    case LDPR_RESOLVED_DYN:
651      assert(GV->isDeclarationForLinker());
652      break;
653
654    case LDPR_UNDEF:
655      if (!GV->isDeclarationForLinker()) {
656        assert(GV->hasComdat());
657        Drop.insert(GV);
658      }
659      break;
660
661    case LDPR_PREVAILING_DEF_IRONLY: {
662      keepGlobalValue(*GV, KeptAliases);
663      if (!Used.count(GV)) {
664        // Since we use the regular lib/Linker, we cannot just internalize GV
665        // now or it will not be copied to the merged module. Instead we force
666        // it to be copied and then internalize it.
667        Internalize.insert(GV->getName());
668      }
669      break;
670    }
671
672    case LDPR_PREVAILING_DEF:
673      keepGlobalValue(*GV, KeptAliases);
674      break;
675
676    case LDPR_PREEMPTED_IR:
677      // Gold might have selected a linkonce_odr and preempted a weak_odr.
678      // In that case we have to make sure we don't end up internalizing it.
679      if (!GV->isDiscardableIfUnused())
680        Maybe.erase(GV->getName());
681
682      // fall-through
683    case LDPR_PREEMPTED_REG:
684      Drop.insert(GV);
685      break;
686
687    case LDPR_PREVAILING_DEF_IRONLY_EXP: {
688      // We can only check for address uses after we merge the modules. The
689      // reason is that this GV might have a copy in another module
690      // and in that module the address might be significant, but that
691      // copy will be LDPR_PREEMPTED_IR.
692      if (GV->hasLinkOnceODRLinkage())
693        Maybe.insert(GV->getName());
694      keepGlobalValue(*GV, KeptAliases);
695      break;
696    }
697    }
698
699    freeSymName(Sym);
700  }
701
702  ValueToValueMapTy VM;
703  LocalValueMaterializer Materializer(Drop);
704  for (GlobalAlias *GA : KeptAliases) {
705    // Gold told us to keep GA. It is possible that a GV usied in the aliasee
706    // expression is being dropped. If that is the case, that GV must be copied.
707    Constant *Aliasee = GA->getAliasee();
708    Constant *Replacement = mapConstantToLocalCopy(Aliasee, VM, &Materializer);
709    GA->setAliasee(Replacement);
710  }
711
712  for (auto *GV : Drop)
713    drop(*GV);
714
715  return Obj.takeModule();
716}
717
718static void runLTOPasses(Module &M, TargetMachine &TM) {
719  if (const DataLayout *DL = TM.getDataLayout())
720    M.setDataLayout(*DL);
721
722  legacy::PassManager passes;
723  passes.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));
724
725  PassManagerBuilder PMB;
726  PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM.getTargetTriple()));
727  PMB.Inliner = createFunctionInliningPass();
728  PMB.VerifyInput = true;
729  PMB.VerifyOutput = true;
730  PMB.LoopVectorize = true;
731  PMB.SLPVectorize = true;
732  PMB.OptLevel = options::OptLevel;
733  PMB.populateLTOPassManager(passes);
734  passes.run(M);
735}
736
737static void saveBCFile(StringRef Path, Module &M) {
738  std::error_code EC;
739  raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
740  if (EC)
741    message(LDPL_FATAL, "Failed to write the output file.");
742  WriteBitcodeToFile(&M, OS, /* ShouldPreserveUseListOrder */ true);
743}
744
745static void codegen(Module &M) {
746  const std::string &TripleStr = M.getTargetTriple();
747  Triple TheTriple(TripleStr);
748
749  std::string ErrMsg;
750  const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
751  if (!TheTarget)
752    message(LDPL_FATAL, "Target not found: %s", ErrMsg.c_str());
753
754  if (unsigned NumOpts = options::extra.size())
755    cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);
756
757  SubtargetFeatures Features;
758  Features.getDefaultSubtargetFeatures(TheTriple);
759  for (const std::string &A : MAttrs)
760    Features.AddFeature(A);
761
762  TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
763  CodeGenOpt::Level CGOptLevel;
764  switch (options::OptLevel) {
765  case 0:
766    CGOptLevel = CodeGenOpt::None;
767    break;
768  case 1:
769    CGOptLevel = CodeGenOpt::Less;
770    break;
771  case 2:
772    CGOptLevel = CodeGenOpt::Default;
773    break;
774  case 3:
775    CGOptLevel = CodeGenOpt::Aggressive;
776    break;
777  }
778  std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
779      TripleStr, options::mcpu, Features.getString(), Options, RelocationModel,
780      CodeModel::Default, CGOptLevel));
781
782  runLTOPasses(M, *TM);
783
784  if (options::TheOutputType == options::OT_SAVE_TEMPS)
785    saveBCFile(output_name + ".opt.bc", M);
786
787  legacy::PassManager CodeGenPasses;
788
789  SmallString<128> Filename;
790  int FD;
791  if (options::obj_path.empty()) {
792    std::error_code EC =
793        sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
794    if (EC)
795      message(LDPL_FATAL, "Could not create temporary file: %s",
796              EC.message().c_str());
797  } else {
798    Filename = options::obj_path;
799    std::error_code EC =
800        sys::fs::openFileForWrite(Filename.c_str(), FD, sys::fs::F_None);
801    if (EC)
802      message(LDPL_FATAL, "Could not open file: %s", EC.message().c_str());
803  }
804
805  {
806    raw_fd_ostream OS(FD, true);
807
808    if (TM->addPassesToEmitFile(CodeGenPasses, OS,
809                                TargetMachine::CGFT_ObjectFile))
810      message(LDPL_FATAL, "Failed to setup codegen");
811    CodeGenPasses.run(M);
812  }
813
814  if (add_input_file(Filename.c_str()) != LDPS_OK)
815    message(LDPL_FATAL,
816            "Unable to add .o file to the link. File left behind in: %s",
817            Filename.c_str());
818
819  if (options::obj_path.empty())
820    Cleanup.push_back(Filename.c_str());
821}
822
823/// gold informs us that all symbols have been read. At this point, we use
824/// get_symbols to see if any of our definitions have been overridden by a
825/// native object file. Then, perform optimization and codegen.
826static ld_plugin_status allSymbolsReadHook(raw_fd_ostream *ApiFile) {
827  if (Modules.empty())
828    return LDPS_OK;
829
830  LLVMContext Context;
831  Context.setDiagnosticHandler(diagnosticHandler, nullptr, true);
832
833  std::unique_ptr<Module> Combined(new Module("ld-temp.o", Context));
834  Linker L(Combined.get());
835
836  std::string DefaultTriple = sys::getDefaultTargetTriple();
837
838  StringSet<> Internalize;
839  StringSet<> Maybe;
840  for (claimed_file &F : Modules) {
841    ld_plugin_input_file File;
842    if (get_input_file(F.handle, &File) != LDPS_OK)
843      message(LDPL_FATAL, "Failed to get file information");
844    std::unique_ptr<Module> M =
845        getModuleForFile(Context, F, File, ApiFile, Internalize, Maybe);
846    if (!options::triple.empty())
847      M->setTargetTriple(options::triple.c_str());
848    else if (M->getTargetTriple().empty()) {
849      M->setTargetTriple(DefaultTriple);
850    }
851
852    if (L.linkInModule(M.get()))
853      message(LDPL_FATAL, "Failed to link module");
854    if (release_input_file(F.handle) != LDPS_OK)
855      message(LDPL_FATAL, "Failed to release file information");
856  }
857
858  for (const auto &Name : Internalize) {
859    GlobalValue *GV = Combined->getNamedValue(Name.first());
860    if (GV)
861      internalize(*GV);
862  }
863
864  for (const auto &Name : Maybe) {
865    GlobalValue *GV = Combined->getNamedValue(Name.first());
866    if (!GV)
867      continue;
868    GV->setLinkage(GlobalValue::LinkOnceODRLinkage);
869    if (canBeOmittedFromSymbolTable(GV))
870      internalize(*GV);
871  }
872
873  if (options::TheOutputType == options::OT_DISABLE)
874    return LDPS_OK;
875
876  if (options::TheOutputType != options::OT_NORMAL) {
877    std::string path;
878    if (options::TheOutputType == options::OT_BC_ONLY)
879      path = output_name;
880    else
881      path = output_name + ".bc";
882    saveBCFile(path, *L.getModule());
883    if (options::TheOutputType == options::OT_BC_ONLY)
884      return LDPS_OK;
885  }
886
887  codegen(*L.getModule());
888
889  if (!options::extra_library_path.empty() &&
890      set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
891    message(LDPL_FATAL, "Unable to set the extra library path.");
892
893  return LDPS_OK;
894}
895
896static ld_plugin_status all_symbols_read_hook(void) {
897  ld_plugin_status Ret;
898  if (!options::generate_api_file) {
899    Ret = allSymbolsReadHook(nullptr);
900  } else {
901    std::error_code EC;
902    raw_fd_ostream ApiFile("apifile.txt", EC, sys::fs::F_None);
903    if (EC)
904      message(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
905              EC.message().c_str());
906    Ret = allSymbolsReadHook(&ApiFile);
907  }
908
909  llvm_shutdown();
910
911  if (options::TheOutputType == options::OT_BC_ONLY ||
912      options::TheOutputType == options::OT_DISABLE) {
913    if (options::TheOutputType == options::OT_DISABLE)
914      // Remove the output file here since ld.bfd creates the output file
915      // early.
916      sys::fs::remove(output_name);
917    exit(0);
918  }
919
920  return Ret;
921}
922
923static ld_plugin_status cleanup_hook(void) {
924  for (std::string &Name : Cleanup) {
925    std::error_code EC = sys::fs::remove(Name);
926    if (EC)
927      message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
928              EC.message().c_str());
929  }
930
931  return LDPS_OK;
932}
933