aboutsummaryrefslogtreecommitdiffstats
path: root/tools/gold/gold-plugin.cpp
blob: e3a57b55f3342aa39bfbe0ec5c9873ae77f40bce (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
//===-- gold-plugin.cpp - Plugin to gold for Link Time Optimization  ------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a gold plugin for LLVM. It provides an LLVM implementation of the
// interface described in http://gcc.gnu.org/wiki/whopr/driver .
//
//===----------------------------------------------------------------------===//

#include "llvm/Config/config.h" // plugin-api.h requires HAVE_STDINT_H
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/IR/AutoUpgrade.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Linker/Linker.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Object/IRObjectFile.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/ValueMapper.h"
#include <list>
#include <plugin-api.h>
#include <system_error>
#include <vector>

#ifndef LDPO_PIE
// FIXME: remove this declaration when we stop maintaining Ubuntu Quantal and
// Precise and Debian Wheezy (binutils 2.23 is required)
# define LDPO_PIE 3
#endif

using namespace llvm;

namespace {
struct claimed_file {
  void *handle;
  std::vector<ld_plugin_symbol> syms;
};
}

static ld_plugin_status discard_message(int level, const char *format, ...) {
  // Die loudly. Recent versions of Gold pass ld_plugin_message as the first
  // callback in the transfer vector. This should never be called.
  abort();
}

static ld_plugin_get_input_file get_input_file = nullptr;
static ld_plugin_release_input_file release_input_file = nullptr;
static ld_plugin_add_symbols add_symbols = nullptr;
static ld_plugin_get_symbols get_symbols = nullptr;
static ld_plugin_add_input_file add_input_file = nullptr;
static ld_plugin_set_extra_library_path set_extra_library_path = nullptr;
static ld_plugin_get_view get_view = nullptr;
static ld_plugin_message message = discard_message;
static Reloc::Model RelocationModel = Reloc::Default;
static std::string output_name = "";
static std::list<claimed_file> Modules;
static std::vector<std::string> Cleanup;
static llvm::TargetOptions TargetOpts;

namespace options {
  enum OutputType {
    OT_NORMAL,
    OT_DISABLE,
    OT_BC_ONLY,
    OT_SAVE_TEMPS
  };
  static bool generate_api_file = false;
  static OutputType TheOutputType = OT_NORMAL;
  static std::string obj_path;
  static std::string extra_library_path;
  static std::string triple;
  static std::string mcpu;
  // Additional options to pass into the code generator.
  // Note: This array will contain all plugin options which are not claimed
  // as plugin exclusive to pass to the code generator.
  // For example, "generate-api-file" and "as"options are for the plugin
  // use only and will not be passed.
  static std::vector<const char *> extra;

  static void process_plugin_option(const char* opt_)
  {
    if (opt_ == nullptr)
      return;
    llvm::StringRef opt = opt_;

    if (opt == "generate-api-file") {
      generate_api_file = true;
    } else if (opt.startswith("mcpu=")) {
      mcpu = opt.substr(strlen("mcpu="));
    } else if (opt.startswith("extra-library-path=")) {
      extra_library_path = opt.substr(strlen("extra_library_path="));
    } else if (opt.startswith("mtriple=")) {
      triple = opt.substr(strlen("mtriple="));
    } else if (opt.startswith("obj-path=")) {
      obj_path = opt.substr(strlen("obj-path="));
    } else if (opt == "emit-llvm") {
      TheOutputType = OT_BC_ONLY;
    } else if (opt == "save-temps") {
      TheOutputType = OT_SAVE_TEMPS;
    } else if (opt == "disable-output") {
      TheOutputType = OT_DISABLE;
    } else {
      // Save this option to pass to the code generator.
      // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
      // add that.
      if (extra.empty())
        extra.push_back("LLVMgold");

      extra.push_back(opt_);
    }
  }
}

static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
                                        int *claimed);
static ld_plugin_status all_symbols_read_hook(void);
static ld_plugin_status cleanup_hook(void);

extern "C" ld_plugin_status onload(ld_plugin_tv *tv);
ld_plugin_status onload(ld_plugin_tv *tv) {
  InitializeAllTargetInfos();
  InitializeAllTargets();
  InitializeAllTargetMCs();
  InitializeAllAsmParsers();
  InitializeAllAsmPrinters();

  // We're given a pointer to the first transfer vector. We read through them
  // until we find one where tv_tag == LDPT_NULL. The REGISTER_* tagged values
  // contain pointers to functions that we need to call to register our own
  // hooks. The others are addresses of functions we can use to call into gold
  // for services.

  bool registeredClaimFile = false;
  bool RegisteredAllSymbolsRead = false;

  for (; tv->tv_tag != LDPT_NULL; ++tv) {
    switch (tv->tv_tag) {
      case LDPT_OUTPUT_NAME:
        output_name = tv->tv_u.tv_string;
        break;
      case LDPT_LINKER_OUTPUT:
        switch (tv->tv_u.tv_val) {
          case LDPO_REL:  // .o
          case LDPO_DYN:  // .so
          case LDPO_PIE:  // position independent executable
            RelocationModel = Reloc::PIC_;
            break;
          case LDPO_EXEC:  // .exe
            RelocationModel = Reloc::Static;
            break;
          default:
            message(LDPL_ERROR, "Unknown output file type %d", tv->tv_u.tv_val);
            return LDPS_ERR;
        }
        break;
      case LDPT_OPTION:
        options::process_plugin_option(tv->tv_u.tv_string);
        break;
      case LDPT_REGISTER_CLAIM_FILE_HOOK: {
        ld_plugin_register_claim_file callback;
        callback = tv->tv_u.tv_register_claim_file;

        if (callback(claim_file_hook) != LDPS_OK)
          return LDPS_ERR;

        registeredClaimFile = true;
      } break;
      case LDPT_REGISTER_ALL_SYMBOLS_READ_HOOK: {
        ld_plugin_register_all_symbols_read callback;
        callback = tv->tv_u.tv_register_all_symbols_read;

        if (callback(all_symbols_read_hook) != LDPS_OK)
          return LDPS_ERR;

        RegisteredAllSymbolsRead = true;
      } break;
      case LDPT_REGISTER_CLEANUP_HOOK: {
        ld_plugin_register_cleanup callback;
        callback = tv->tv_u.tv_register_cleanup;

        if (callback(cleanup_hook) != LDPS_OK)
          return LDPS_ERR;
      } break;
      case LDPT_GET_INPUT_FILE:
        get_input_file = tv->tv_u.tv_get_input_file;
        break;
      case LDPT_RELEASE_INPUT_FILE:
        release_input_file = tv->tv_u.tv_release_input_file;
        break;
      case LDPT_ADD_SYMBOLS:
        add_symbols = tv->tv_u.tv_add_symbols;
        break;
      case LDPT_GET_SYMBOLS_V2:
        get_symbols = tv->tv_u.tv_get_symbols;
        break;
      case LDPT_ADD_INPUT_FILE:
        add_input_file = tv->tv_u.tv_add_input_file;
        break;
      case LDPT_SET_EXTRA_LIBRARY_PATH:
        set_extra_library_path = tv->tv_u.tv_set_extra_library_path;
        break;
      case LDPT_GET_VIEW:
        get_view = tv->tv_u.tv_get_view;
        break;
      case LDPT_MESSAGE:
        message = tv->tv_u.tv_message;
        break;
      default:
        break;
    }
  }

  if (!registeredClaimFile) {
    message(LDPL_ERROR, "register_claim_file not passed to LLVMgold.");
    return LDPS_ERR;
  }
  if (!add_symbols) {
    message(LDPL_ERROR, "add_symbols not passed to LLVMgold.");
    return LDPS_ERR;
  }

  if (!RegisteredAllSymbolsRead)
    return LDPS_OK;

  if (!get_input_file) {
    message(LDPL_ERROR, "get_input_file not passed to LLVMgold.");
    return LDPS_ERR;
  }
  if (!release_input_file) {
    message(LDPL_ERROR, "relesase_input_file not passed to LLVMgold.");
    return LDPS_ERR;
  }

  return LDPS_OK;
}

static const GlobalObject *getBaseObject(const GlobalValue &GV) {
  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
    return GA->getBaseObject();
  return cast<GlobalObject>(&GV);
}

static bool shouldSkip(uint32_t Symflags) {
  if (!(Symflags & object::BasicSymbolRef::SF_Global))
    return true;
  if (Symflags & object::BasicSymbolRef::SF_FormatSpecific)
    return true;
  return false;
}

static void diagnosticHandler(const DiagnosticInfo &DI, void *Context) {
  if (const auto *BDI = dyn_cast<BitcodeDiagnosticInfo>(&DI)) {
    std::error_code EC = BDI->getError();
    if (EC == BitcodeError::InvalidBitcodeSignature)
      return;
  }

  std::string ErrStorage;
  {
    raw_string_ostream OS(ErrStorage);
    DiagnosticPrinterRawOStream DP(OS);
    DI.print(DP);
  }
  ld_plugin_level Level;
  switch (DI.getSeverity()) {
  case DS_Error:
    message(LDPL_FATAL, "LLVM gold plugin has failed to create LTO module: %s",
            ErrStorage.c_str());
    llvm_unreachable("Fatal doesn't return.");
  case DS_Warning:
    Level = LDPL_WARNING;
    break;
  case DS_Remark:
  case DS_Note:
    Level = LDPL_INFO;
    break;
  }
  message(Level, "LLVM gold plugin: %s",  ErrStorage.c_str());
}

/// Called by gold to see whether this file is one that our plugin can handle.
/// We'll try to open it and register all the symbols with add_symbol if
/// possible.
static ld_plugin_status claim_file_hook(const ld_plugin_input_file *file,
                                        int *claimed) {
  LLVMContext Context;
  MemoryBufferRef BufferRef;
  std::unique_ptr<MemoryBuffer> Buffer;
  if (get_view) {
    const void *view;
    if (get_view(file->handle, &view) != LDPS_OK) {
      message(LDPL_ERROR, "Failed to get a view of %s", file->name);
      return LDPS_ERR;
    }
    BufferRef = MemoryBufferRef(StringRef((const char *)view, file->filesize), "");
  } else {
    int64_t offset = 0;
    // Gold has found what might be IR part-way inside of a file, such as
    // an .a archive.
    if (file->offset) {
      offset = file->offset;
    }
    ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
        MemoryBuffer::getOpenFileSlice(file->fd, file->name, file->filesize,
                                       offset);
    if (std::error_code EC = BufferOrErr.getError()) {
      message(LDPL_ERROR, EC.message().c_str());
      return LDPS_ERR;
    }
    Buffer = std::move(BufferOrErr.get());
    BufferRef = Buffer->getMemBufferRef();
  }

  Context.setDiagnosticHandler(diagnosticHandler);
  ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
      object::IRObjectFile::create(BufferRef, Context);
  std::error_code EC = ObjOrErr.getError();
  if (EC == object::object_error::invalid_file_type ||
      EC == object::object_error::bitcode_section_not_found)
    return LDPS_OK;

  *claimed = 1;

  if (EC) {
    message(LDPL_ERROR, "LLVM gold plugin has failed to create LTO module: %s",
            EC.message().c_str());
    return LDPS_ERR;
  }
  std::unique_ptr<object::IRObjectFile> Obj = std::move(*ObjOrErr);

  Modules.resize(Modules.size() + 1);
  claimed_file &cf = Modules.back();

  cf.handle = file->handle;

  for (auto &Sym : Obj->symbols()) {
    uint32_t Symflags = Sym.getFlags();
    if (shouldSkip(Symflags))
      continue;

    cf.syms.push_back(ld_plugin_symbol());
    ld_plugin_symbol &sym = cf.syms.back();
    sym.version = nullptr;

    SmallString<64> Name;
    {
      raw_svector_ostream OS(Name);
      Sym.printName(OS);
    }
    sym.name = strdup(Name.c_str());

    const GlobalValue *GV = Obj->getSymbolGV(Sym.getRawDataRefImpl());

    sym.visibility = LDPV_DEFAULT;
    if (GV) {
      switch (GV->getVisibility()) {
      case GlobalValue::DefaultVisibility:
        sym.visibility = LDPV_DEFAULT;
        break;
      case GlobalValue::HiddenVisibility:
        sym.visibility = LDPV_HIDDEN;
        break;
      case GlobalValue::ProtectedVisibility:
        sym.visibility = LDPV_PROTECTED;
        break;
      }
    }

    if (Symflags & object::BasicSymbolRef::SF_Undefined) {
      sym.def = LDPK_UNDEF;
      if (GV && GV->hasExternalWeakLinkage())
        sym.def = LDPK_WEAKUNDEF;
    } else {
      sym.def = LDPK_DEF;
      if (GV) {
        assert(!GV->hasExternalWeakLinkage() &&
               !GV->hasAvailableExternallyLinkage() && "Not a declaration!");
        if (GV->hasCommonLinkage())
          sym.def = LDPK_COMMON;
        else if (GV->isWeakForLinker())
          sym.def = LDPK_WEAKDEF;
      }
    }

    sym.size = 0;
    sym.comdat_key = nullptr;
    if (GV) {
      const GlobalObject *Base = getBaseObject(*GV);
      if (!Base)
        message(LDPL_FATAL, "Unable to determine comdat of alias!");
      const Comdat *C = Base->getComdat();
      if (C)
        sym.comdat_key = strdup(C->getName().str().c_str());
      else if (Base->hasWeakLinkage() || Base->hasLinkOnceLinkage())
        sym.comdat_key = strdup(sym.name);
    }

    sym.resolution = LDPR_UNKNOWN;
  }

  if (!cf.syms.empty()) {
    if (add_symbols(cf.handle, cf.syms.size(), &cf.syms[0]) != LDPS_OK) {
      message(LDPL_ERROR, "Unable to add symbols!");
      return LDPS_ERR;
    }
  }

  return LDPS_OK;
}

static void keepGlobalValue(GlobalValue &GV,
                            std::vector<GlobalAlias *> &KeptAliases) {
  assert(!GV.hasLocalLinkage());

  if (auto *GA = dyn_cast<GlobalAlias>(&GV))
    KeptAliases.push_back(GA);

  switch (GV.getLinkage()) {
  default:
    break;
  case GlobalValue::LinkOnceAnyLinkage:
    GV.setLinkage(GlobalValue::WeakAnyLinkage);
    break;
  case GlobalValue::LinkOnceODRLinkage:
    GV.setLinkage(GlobalValue::WeakODRLinkage);
    break;
  }

  assert(!GV.isDiscardableIfUnused());
}

static void internalize(GlobalValue &GV) {
  if (GV.isDeclarationForLinker())
    return; // We get here if there is a matching asm definition.
  if (!GV.hasLocalLinkage())
    GV.setLinkage(GlobalValue::InternalLinkage);
}

static void drop(GlobalValue &GV) {
  if (auto *F = dyn_cast<Function>(&GV)) {
    F->deleteBody();
    F->setComdat(nullptr); // Should deleteBody do this?
    return;
  }

  if (auto *Var = dyn_cast<GlobalVariable>(&GV)) {
    Var->setInitializer(nullptr);
    Var->setLinkage(
        GlobalValue::ExternalLinkage); // Should setInitializer do this?
    Var->setComdat(nullptr); // and this?
    return;
  }

  auto &Alias = cast<GlobalAlias>(GV);
  Module &M = *Alias.getParent();
  PointerType &Ty = *cast<PointerType>(Alias.getType());
  GlobalValue::LinkageTypes L = Alias.getLinkage();
  auto *Var =
      new GlobalVariable(M, Ty.getElementType(), /*isConstant*/ false, L,
                         /*Initializer*/ nullptr);
  Var->takeName(&Alias);
  Alias.replaceAllUsesWith(Var);
  Alias.eraseFromParent();
}

static const char *getResolutionName(ld_plugin_symbol_resolution R) {
  switch (R) {
  case LDPR_UNKNOWN:
    return "UNKNOWN";
  case LDPR_UNDEF:
    return "UNDEF";
  case LDPR_PREVAILING_DEF:
    return "PREVAILING_DEF";
  case LDPR_PREVAILING_DEF_IRONLY:
    return "PREVAILING_DEF_IRONLY";
  case LDPR_PREEMPTED_REG:
    return "PREEMPTED_REG";
  case LDPR_PREEMPTED_IR:
    return "PREEMPTED_IR";
  case LDPR_RESOLVED_IR:
    return "RESOLVED_IR";
  case LDPR_RESOLVED_EXEC:
    return "RESOLVED_EXEC";
  case LDPR_RESOLVED_DYN:
    return "RESOLVED_DYN";
  case LDPR_PREVAILING_DEF_IRONLY_EXP:
    return "PREVAILING_DEF_IRONLY_EXP";
  }
  llvm_unreachable("Unknown resolution");
}

namespace {
class LocalValueMaterializer : public ValueMaterializer {
  DenseSet<GlobalValue *> &Dropped;
  DenseMap<GlobalObject *, GlobalObject *> LocalVersions;

public:
  LocalValueMaterializer(DenseSet<GlobalValue *> &Dropped) : Dropped(Dropped) {}
  Value *materializeValueFor(Value *V) override;
};
}

Value *LocalValueMaterializer::materializeValueFor(Value *V) {
  auto *GO = dyn_cast<GlobalObject>(V);
  if (!GO)
    return nullptr;

  auto I = LocalVersions.find(GO);
  if (I != LocalVersions.end())
    return I->second;

  if (!Dropped.count(GO))
    return nullptr;

  Module &M = *GO->getParent();
  GlobalValue::LinkageTypes L = GO->getLinkage();
  GlobalObject *Declaration;
  if (auto *F = dyn_cast<Function>(GO)) {
    Declaration = Function::Create(F->getFunctionType(), L, "", &M);
  } else {
    auto *Var = cast<GlobalVariable>(GO);
    Declaration = new GlobalVariable(M, Var->getType()->getElementType(),
                                     Var->isConstant(), L,
                                     /*Initializer*/ nullptr);
  }
  Declaration->takeName(GO);
  Declaration->copyAttributesFrom(GO);

  GO->setLinkage(GlobalValue::InternalLinkage);
  GO->setName(Declaration->getName());
  Dropped.erase(GO);
  GO->replaceAllUsesWith(Declaration);

  LocalVersions[Declaration] = GO;

  return GO;
}

static Constant *mapConstantToLocalCopy(Constant *C, ValueToValueMapTy &VM,
                                        LocalValueMaterializer *Materializer) {
  return MapValue(C, VM, RF_IgnoreMissingEntries, nullptr, Materializer);
}

static void freeSymName(ld_plugin_symbol &Sym) {
  free(Sym.name);
  free(Sym.comdat_key);
  Sym.name = nullptr;
  Sym.comdat_key = nullptr;
}

static std::unique_ptr<Module>
getModuleForFile(LLVMContext &Context, claimed_file &F,
                 ld_plugin_input_file &Info, raw_fd_ostream *ApiFile,
                 StringSet<> &Internalize, StringSet<> &Maybe) {

  if (get_symbols(F.handle, F.syms.size(), &F.syms[0]) != LDPS_OK)
    message(LDPL_FATAL, "Failed to get symbol information");

  const void *View;
  if (get_view(F.handle, &View) != LDPS_OK)
    message(LDPL_FATAL, "Failed to get a view of file");

  MemoryBufferRef BufferRef(StringRef((const char *)View, Info.filesize),
                            Info.name);
  ErrorOr<std::unique_ptr<object::IRObjectFile>> ObjOrErr =
      object::IRObjectFile::create(BufferRef, Context);

  if (std::error_code EC = ObjOrErr.getError())
    message(LDPL_FATAL, "Could not read bitcode from file : %s",
            EC.message().c_str());

  object::IRObjectFile &Obj = **ObjOrErr;

  Module &M = Obj.getModule();

  UpgradeDebugInfo(M);

  SmallPtrSet<GlobalValue *, 8> Used;
  collectUsedGlobalVariables(M, Used, /*CompilerUsed*/ false);

  DenseSet<GlobalValue *> Drop;
  std::vector<GlobalAlias *> KeptAliases;

  unsigned SymNum = 0;
  for (auto &ObjSym : Obj.symbols()) {
    if (shouldSkip(ObjSym.getFlags()))
      continue;
    ld_plugin_symbol &Sym = F.syms[SymNum];
    ++SymNum;

    ld_plugin_symbol_resolution Resolution =
        (ld_plugin_symbol_resolution)Sym.resolution;

    if (options::generate_api_file)
      *ApiFile << Sym.name << ' ' << getResolutionName(Resolution) << '\n';

    GlobalValue *GV = Obj.getSymbolGV(ObjSym.getRawDataRefImpl());
    if (!GV) {
      freeSymName(Sym);
      continue; // Asm symbol.
    }

    if (Resolution != LDPR_PREVAILING_DEF_IRONLY && GV->hasCommonLinkage()) {
      // Common linkage is special. There is no single symbol that wins the
      // resolution. Instead we have to collect the maximum alignment and size.
      // The IR linker does that for us if we just pass it every common GV.
      // We still have to keep track of LDPR_PREVAILING_DEF_IRONLY so we
      // internalize once the IR linker has done its job.
      freeSymName(Sym);
      continue;
    }

    switch (Resolution) {
    case LDPR_UNKNOWN:
      llvm_unreachable("Unexpected resolution");

    case LDPR_RESOLVED_IR:
    case LDPR_RESOLVED_EXEC:
    case LDPR_RESOLVED_DYN:
      assert(GV->isDeclarationForLinker());
      break;

    case LDPR_UNDEF:
      if (!GV->isDeclarationForLinker()) {
        assert(GV->hasComdat());
        Drop.insert(GV);
      }
      break;

    case LDPR_PREVAILING_DEF_IRONLY: {
      keepGlobalValue(*GV, KeptAliases);
      if (!Used.count(GV)) {
        // Since we use the regular lib/Linker, we cannot just internalize GV
        // now or it will not be copied to the merged module. Instead we force
        // it to be copied and then internalize it.
        Internalize.insert(GV->getName());
      }
      break;
    }

    case LDPR_PREVAILING_DEF:
      keepGlobalValue(*GV, KeptAliases);
      break;

    case LDPR_PREEMPTED_IR:
      // Gold might have selected a linkonce_odr and preempted a weak_odr.
      // In that case we have to make sure we don't end up internalizing it.
      if (!GV->isDiscardableIfUnused())
        Maybe.erase(GV->getName());

      // fall-through
    case LDPR_PREEMPTED_REG:
      Drop.insert(GV);
      break;

    case LDPR_PREVAILING_DEF_IRONLY_EXP: {
      // We can only check for address uses after we merge the modules. The
      // reason is that this GV might have a copy in another module
      // and in that module the address might be significant, but that
      // copy will be LDPR_PREEMPTED_IR.
      if (GV->hasLinkOnceODRLinkage())
        Maybe.insert(GV->getName());
      keepGlobalValue(*GV, KeptAliases);
      break;
    }
    }

    freeSymName(Sym);
  }

  ValueToValueMapTy VM;
  LocalValueMaterializer Materializer(Drop);
  for (GlobalAlias *GA : KeptAliases) {
    // Gold told us to keep GA. It is possible that a GV usied in the aliasee
    // expression is being dropped. If that is the case, that GV must be copied.
    Constant *Aliasee = GA->getAliasee();
    Constant *Replacement = mapConstantToLocalCopy(Aliasee, VM, &Materializer);
    GA->setAliasee(Replacement);
  }

  for (auto *GV : Drop)
    drop(*GV);

  return Obj.takeModule();
}

static void runLTOPasses(Module &M, TargetMachine &TM) {
  if (const DataLayout *DL = TM.getDataLayout())
    M.setDataLayout(DL);

  legacy::PassManager passes;
  passes.add(new DataLayoutPass());
  passes.add(createTargetTransformInfoWrapperPass(TM.getTargetIRAnalysis()));

  PassManagerBuilder PMB;
  PMB.LibraryInfo = new TargetLibraryInfoImpl(Triple(TM.getTargetTriple()));
  PMB.Inliner = createFunctionInliningPass();
  PMB.VerifyInput = true;
  PMB.VerifyOutput = true;
  PMB.LoopVectorize = true;
  PMB.SLPVectorize = true;
  PMB.populateLTOPassManager(passes);
  passes.run(M);
}

static void saveBCFile(StringRef Path, Module &M) {
  std::error_code EC;
  raw_fd_ostream OS(Path, EC, sys::fs::OpenFlags::F_None);
  if (EC)
    message(LDPL_FATAL, "Failed to write the output file.");
  WriteBitcodeToFile(&M, OS);
}

static void codegen(Module &M) {
  const std::string &TripleStr = M.getTargetTriple();
  Triple TheTriple(TripleStr);

  std::string ErrMsg;
  const Target *TheTarget = TargetRegistry::lookupTarget(TripleStr, ErrMsg);
  if (!TheTarget)
    message(LDPL_FATAL, "Target not found: %s", ErrMsg.c_str());

  if (unsigned NumOpts = options::extra.size())
    cl::ParseCommandLineOptions(NumOpts, &options::extra[0]);

  SubtargetFeatures Features;
  Features.getDefaultSubtargetFeatures(TheTriple);
  for (const std::string &A : MAttrs)
    Features.AddFeature(A);

  TargetOptions Options = InitTargetOptionsFromCodeGenFlags();
  std::unique_ptr<TargetMachine> TM(TheTarget->createTargetMachine(
      TripleStr, options::mcpu, Features.getString(), Options, RelocationModel,
      CodeModel::Default, CodeGenOpt::Aggressive));

  runLTOPasses(M, *TM);

  if (options::TheOutputType == options::OT_SAVE_TEMPS)
    saveBCFile(output_name + ".opt.bc", M);

  legacy::PassManager CodeGenPasses;
  CodeGenPasses.add(new DataLayoutPass());

  SmallString<128> Filename;
  int FD;
  if (options::obj_path.empty()) {
    std::error_code EC =
        sys::fs::createTemporaryFile("lto-llvm", "o", FD, Filename);
    if (EC)
      message(LDPL_FATAL, "Could not create temporary file: %s",
              EC.message().c_str());
  } else {
    Filename = options::obj_path;
    std::error_code EC =
        sys::fs::openFileForWrite(Filename.c_str(), FD, sys::fs::F_None);
    if (EC)
      message(LDPL_FATAL, "Could not open file: %s", EC.message().c_str());
  }

  {
    raw_fd_ostream OS(FD, true);
    formatted_raw_ostream FOS(OS);

    if (TM->addPassesToEmitFile(CodeGenPasses, FOS,
                                TargetMachine::CGFT_ObjectFile))
      message(LDPL_FATAL, "Failed to setup codegen");
    CodeGenPasses.run(M);
  }

  if (add_input_file(Filename.c_str()) != LDPS_OK)
    message(LDPL_FATAL,
            "Unable to add .o file to the link. File left behind in: %s",
            Filename.c_str());

  if (options::obj_path.empty())
    Cleanup.push_back(Filename.c_str());
}

/// gold informs us that all symbols have been read. At this point, we use
/// get_symbols to see if any of our definitions have been overridden by a
/// native object file. Then, perform optimization and codegen.
static ld_plugin_status allSymbolsReadHook(raw_fd_ostream *ApiFile) {
  if (Modules.empty())
    return LDPS_OK;

  LLVMContext Context;
  Context.setDiagnosticHandler(diagnosticHandler);

  std::unique_ptr<Module> Combined(new Module("ld-temp.o", Context));
  Linker L(Combined.get());

  std::string DefaultTriple = sys::getDefaultTargetTriple();

  StringSet<> Internalize;
  StringSet<> Maybe;
  for (claimed_file &F : Modules) {
    ld_plugin_input_file File;
    if (get_input_file(F.handle, &File) != LDPS_OK)
      message(LDPL_FATAL, "Failed to get file information");
    std::unique_ptr<Module> M =
        getModuleForFile(Context, F, File, ApiFile, Internalize, Maybe);
    if (!options::triple.empty())
      M->setTargetTriple(options::triple.c_str());
    else if (M->getTargetTriple().empty()) {
      M->setTargetTriple(DefaultTriple);
    }

    if (L.linkInModule(M.get()))
      message(LDPL_FATAL, "Failed to link module");
    if (release_input_file(F.handle) != LDPS_OK)
      message(LDPL_FATAL, "Failed to release file information");
  }

  for (const auto &Name : Internalize) {
    GlobalValue *GV = Combined->getNamedValue(Name.first());
    if (GV)
      internalize(*GV);
  }

  for (const auto &Name : Maybe) {
    GlobalValue *GV = Combined->getNamedValue(Name.first());
    if (!GV)
      continue;
    GV->setLinkage(GlobalValue::LinkOnceODRLinkage);
    if (canBeOmittedFromSymbolTable(GV))
      internalize(*GV);
  }

  if (options::TheOutputType == options::OT_DISABLE)
    return LDPS_OK;

  if (options::TheOutputType != options::OT_NORMAL) {
    std::string path;
    if (options::TheOutputType == options::OT_BC_ONLY)
      path = output_name;
    else
      path = output_name + ".bc";
    saveBCFile(path, *L.getModule());
    if (options::TheOutputType == options::OT_BC_ONLY)
      return LDPS_OK;
  }

  codegen(*L.getModule());

  if (!options::extra_library_path.empty() &&
      set_extra_library_path(options::extra_library_path.c_str()) != LDPS_OK)
    message(LDPL_FATAL, "Unable to set the extra library path.");

  return LDPS_OK;
}

static ld_plugin_status all_symbols_read_hook(void) {
  ld_plugin_status Ret;
  if (!options::generate_api_file) {
    Ret = allSymbolsReadHook(nullptr);
  } else {
    std::error_code EC;
    raw_fd_ostream ApiFile("apifile.txt", EC, sys::fs::F_None);
    if (EC)
      message(LDPL_FATAL, "Unable to open apifile.txt for writing: %s",
              EC.message().c_str());
    Ret = allSymbolsReadHook(&ApiFile);
  }

  llvm_shutdown();

  if (options::TheOutputType == options::OT_BC_ONLY ||
      options::TheOutputType == options::OT_DISABLE) {
    if (options::TheOutputType == options::OT_DISABLE)
      // Remove the output file here since ld.bfd creates the output file
      // early.
      sys::fs::remove(output_name);
    exit(0);
  }

  return Ret;
}

static ld_plugin_status cleanup_hook(void) {
  for (std::string &Name : Cleanup) {
    std::error_code EC = sys::fs::remove(Name);
    if (EC)
      message(LDPL_ERROR, "Failed to delete '%s': %s", Name.c_str(),
              EC.message().c_str());
  }

  return LDPS_OK;
}