llvm.org GIT mirror llvm / 1a7f705 lib / LTO / LTOModule.cpp
1a7f705

Tree @1a7f705 (Download .tar.gz)

LTOModule.cpp @1a7f705raw · history · blame

  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
//===-- LTOModule.cpp - LLVM Link Time Optimizer --------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the Link Time Optimization library. This library is
// intended to be used by linker to optimize code at link time.
//
//===----------------------------------------------------------------------===//

#include "llvm/LTO/LTOModule.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCTargetAsmParser.h"
#include "llvm/MC/SubtargetFeature.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
#include <system_error>
using namespace llvm;

LTOModule::LTOModule(std::unique_ptr<object::IRObjectFile> Obj,
                     llvm::TargetMachine *TM)
    : IRFile(std::move(Obj)), _target(TM) {}

/// isBitcodeFile - Returns 'true' if the file (or memory contents) is LLVM
/// bitcode.
bool LTOModule::isBitcodeFile(const void *mem, size_t length) {
  return sys::fs::identify_magic(StringRef((const char *)mem, length)) ==
         sys::fs::file_magic::bitcode;
}

bool LTOModule::isBitcodeFile(const char *path) {
  sys::fs::file_magic type;
  if (sys::fs::identify_magic(path, type))
    return false;
  return type == sys::fs::file_magic::bitcode;
}

bool LTOModule::isBitcodeForTarget(MemoryBuffer *buffer,
                                   StringRef triplePrefix) {
  std::string Triple =
      getBitcodeTargetTriple(buffer->getMemBufferRef(), getGlobalContext());
  return StringRef(Triple).startswith(triplePrefix);
}

LTOModule *LTOModule::createFromFile(const char *path, TargetOptions options,
                                     std::string &errMsg) {
  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
      MemoryBuffer::getFile(path);
  if (std::error_code EC = BufferOrErr.getError()) {
    errMsg = EC.message();
    return nullptr;
  }
  std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOrErr.get());
  return makeLTOModule(Buffer->getMemBufferRef(), options, errMsg);
}

LTOModule *LTOModule::createFromOpenFile(int fd, const char *path, size_t size,
                                         TargetOptions options,
                                         std::string &errMsg) {
  return createFromOpenFileSlice(fd, path, size, 0, options, errMsg);
}

LTOModule *LTOModule::createFromOpenFileSlice(int fd, const char *path,
                                              size_t map_size, off_t offset,
                                              TargetOptions options,
                                              std::string &errMsg) {
  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
      MemoryBuffer::getOpenFileSlice(fd, path, map_size, offset);
  if (std::error_code EC = BufferOrErr.getError()) {
    errMsg = EC.message();
    return nullptr;
  }
  std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOrErr.get());
  return makeLTOModule(Buffer->getMemBufferRef(), options, errMsg);
}

LTOModule *LTOModule::createFromBuffer(const void *mem, size_t length,
                                       TargetOptions options,
                                       std::string &errMsg, StringRef path) {
  StringRef Data((const char *)mem, length);
  MemoryBufferRef Buffer(Data, path);
  return makeLTOModule(Buffer, options, errMsg);
}

LTOModule *LTOModule::makeLTOModule(MemoryBufferRef Buffer,
                                    TargetOptions options,
                                    std::string &errMsg) {
  ErrorOr<Module *> MOrErr = parseBitcodeFile(Buffer, getGlobalContext());
  if (std::error_code EC = MOrErr.getError()) {
    errMsg = EC.message();
    return nullptr;
  }
  std::unique_ptr<Module> M(MOrErr.get());

  std::string TripleStr = M->getTargetTriple();
  if (TripleStr.empty())
    TripleStr = sys::getDefaultTargetTriple();
  llvm::Triple Triple(TripleStr);

  // find machine architecture for this module
  const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
  if (!march)
    return nullptr;

  // construct LTOModule, hand over ownership of module and target
  SubtargetFeatures Features;
  Features.getDefaultSubtargetFeatures(Triple);
  std::string FeatureStr = Features.getString();
  // Set a default CPU for Darwin triples.
  std::string CPU;
  if (Triple.isOSDarwin()) {
    if (Triple.getArch() == llvm::Triple::x86_64)
      CPU = "core2";
    else if (Triple.getArch() == llvm::Triple::x86)
      CPU = "yonah";
    else if (Triple.getArch() == llvm::Triple::aarch64)
      CPU = "cyclone";
  }

  TargetMachine *target = march->createTargetMachine(TripleStr, CPU, FeatureStr,
                                                     options);
  M->setDataLayout(target->getSubtargetImpl()->getDataLayout());

  std::unique_ptr<object::IRObjectFile> IRObj(
      new object::IRObjectFile(Buffer, std::move(M)));

  LTOModule *Ret = new LTOModule(std::move(IRObj), target);

  if (Ret->parseSymbols(errMsg)) {
    delete Ret;
    return nullptr;
  }

  Ret->parseMetadata();

  return Ret;
}

/// Create a MemoryBuffer from a memory range with an optional name.
std::unique_ptr<MemoryBuffer>
LTOModule::makeBuffer(const void *mem, size_t length, StringRef name) {
  const char *startPtr = (const char*)mem;
  return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), name, false);
}

/// objcClassNameFromExpression - Get string that the data pointer points to.
bool
LTOModule::objcClassNameFromExpression(const Constant *c, std::string &name) {
  if (const ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
    Constant *op = ce->getOperand(0);
    if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
      Constant *cn = gvn->getInitializer();
      if (ConstantDataArray *ca = dyn_cast<ConstantDataArray>(cn)) {
        if (ca->isCString()) {
          name = ".objc_class_name_" + ca->getAsCString().str();
          return true;
        }
      }
    }
  }
  return false;
}

/// addObjCClass - Parse i386/ppc ObjC class data structure.
void LTOModule::addObjCClass(const GlobalVariable *clgv) {
  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
  if (!c) return;

  // second slot in __OBJC,__class is pointer to superclass name
  std::string superclassName;
  if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
    NameAndAttributes info;
    StringMap<NameAndAttributes>::value_type &entry =
      _undefines.GetOrCreateValue(superclassName);
    if (!entry.getValue().name) {
      const char *symbolName = entry.getKey().data();
      info.name = symbolName;
      info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
      info.isFunction = false;
      info.symbol = clgv;
      entry.setValue(info);
    }
  }

  // third slot in __OBJC,__class is pointer to class name
  std::string className;
  if (objcClassNameFromExpression(c->getOperand(2), className)) {
    StringSet::value_type &entry = _defines.GetOrCreateValue(className);
    entry.setValue(1);

    NameAndAttributes info;
    info.name = entry.getKey().data();
    info.attributes = LTO_SYMBOL_PERMISSIONS_DATA |
      LTO_SYMBOL_DEFINITION_REGULAR | LTO_SYMBOL_SCOPE_DEFAULT;
    info.isFunction = false;
    info.symbol = clgv;
    _symbols.push_back(info);
  }
}

/// addObjCCategory - Parse i386/ppc ObjC category data structure.
void LTOModule::addObjCCategory(const GlobalVariable *clgv) {
  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
  if (!c) return;

  // second slot in __OBJC,__category is pointer to target class name
  std::string targetclassName;
  if (!objcClassNameFromExpression(c->getOperand(1), targetclassName))
    return;

  NameAndAttributes info;
  StringMap<NameAndAttributes>::value_type &entry =
    _undefines.GetOrCreateValue(targetclassName);

  if (entry.getValue().name)
    return;

  const char *symbolName = entry.getKey().data();
  info.name = symbolName;
  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
  info.isFunction = false;
  info.symbol = clgv;
  entry.setValue(info);
}

/// addObjCClassRef - Parse i386/ppc ObjC class list data structure.
void LTOModule::addObjCClassRef(const GlobalVariable *clgv) {
  std::string targetclassName;
  if (!objcClassNameFromExpression(clgv->getInitializer(), targetclassName))
    return;

  NameAndAttributes info;
  StringMap<NameAndAttributes>::value_type &entry =
    _undefines.GetOrCreateValue(targetclassName);
  if (entry.getValue().name)
    return;

  const char *symbolName = entry.getKey().data();
  info.name = symbolName;
  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
  info.isFunction = false;
  info.symbol = clgv;
  entry.setValue(info);
}

void LTOModule::addDefinedDataSymbol(const object::BasicSymbolRef &Sym) {
  SmallString<64> Buffer;
  {
    raw_svector_ostream OS(Buffer);
    Sym.printName(OS);
  }

  const GlobalValue *V = IRFile->getSymbolGV(Sym.getRawDataRefImpl());
  addDefinedDataSymbol(Buffer.c_str(), V);
}

void LTOModule::addDefinedDataSymbol(const char *Name, const GlobalValue *v) {
  // Add to list of defined symbols.
  addDefinedSymbol(Name, v, false);

  if (!v->hasSection() /* || !isTargetDarwin */)
    return;

  // Special case i386/ppc ObjC data structures in magic sections:
  // The issue is that the old ObjC object format did some strange
  // contortions to avoid real linker symbols.  For instance, the
  // ObjC class data structure is allocated statically in the executable
  // that defines that class.  That data structures contains a pointer to
  // its superclass.  But instead of just initializing that part of the
  // struct to the address of its superclass, and letting the static and
  // dynamic linkers do the rest, the runtime works by having that field
  // instead point to a C-string that is the name of the superclass.
  // At runtime the objc initialization updates that pointer and sets
  // it to point to the actual super class.  As far as the linker
  // knows it is just a pointer to a string.  But then someone wanted the
  // linker to issue errors at build time if the superclass was not found.
  // So they figured out a way in mach-o object format to use an absolute
  // symbols (.objc_class_name_Foo = 0) and a floating reference
  // (.reference .objc_class_name_Bar) to cause the linker into erroring when
  // a class was missing.
  // The following synthesizes the implicit .objc_* symbols for the linker
  // from the ObjC data structures generated by the front end.

  // special case if this data blob is an ObjC class definition
  std::string Section = v->getSection();
  if (Section.compare(0, 15, "__OBJC,__class,") == 0) {
    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
      addObjCClass(gv);
    }
  }

  // special case if this data blob is an ObjC category definition
  else if (Section.compare(0, 18, "__OBJC,__category,") == 0) {
    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
      addObjCCategory(gv);
    }
  }

  // special case if this data blob is the list of referenced classes
  else if (Section.compare(0, 18, "__OBJC,__cls_refs,") == 0) {
    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
      addObjCClassRef(gv);
    }
  }
}

void LTOModule::addDefinedFunctionSymbol(const object::BasicSymbolRef &Sym) {
  SmallString<64> Buffer;
  {
    raw_svector_ostream OS(Buffer);
    Sym.printName(OS);
  }

  const Function *F =
      cast<Function>(IRFile->getSymbolGV(Sym.getRawDataRefImpl()));
  addDefinedFunctionSymbol(Buffer.c_str(), F);
}

void LTOModule::addDefinedFunctionSymbol(const char *Name, const Function *F) {
  // add to list of defined symbols
  addDefinedSymbol(Name, F, true);
}

void LTOModule::addDefinedSymbol(const char *Name, const GlobalValue *def,
                                 bool isFunction) {
  // set alignment part log2() can have rounding errors
  uint32_t align = def->getAlignment();
  uint32_t attr = align ? countTrailingZeros(align) : 0;

  // set permissions part
  if (isFunction) {
    attr |= LTO_SYMBOL_PERMISSIONS_CODE;
  } else {
    const GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
    if (gv && gv->isConstant())
      attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
    else
      attr |= LTO_SYMBOL_PERMISSIONS_DATA;
  }

  // set definition part
  if (def->hasWeakLinkage() || def->hasLinkOnceLinkage())
    attr |= LTO_SYMBOL_DEFINITION_WEAK;
  else if (def->hasCommonLinkage())
    attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
  else
    attr |= LTO_SYMBOL_DEFINITION_REGULAR;

  // set scope part
  if (def->hasLocalLinkage())
    // Ignore visibility if linkage is local.
    attr |= LTO_SYMBOL_SCOPE_INTERNAL;
  else if (def->hasHiddenVisibility())
    attr |= LTO_SYMBOL_SCOPE_HIDDEN;
  else if (def->hasProtectedVisibility())
    attr |= LTO_SYMBOL_SCOPE_PROTECTED;
  else if (canBeOmittedFromSymbolTable(def))
    attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
  else
    attr |= LTO_SYMBOL_SCOPE_DEFAULT;

  StringSet::value_type &entry = _defines.GetOrCreateValue(Name);
  entry.setValue(1);

  // fill information structure
  NameAndAttributes info;
  StringRef NameRef = entry.getKey();
  info.name = NameRef.data();
  assert(info.name[NameRef.size()] == '\0');
  info.attributes = attr;
  info.isFunction = isFunction;
  info.symbol = def;

  // add to table of symbols
  _symbols.push_back(info);
}

/// addAsmGlobalSymbol - Add a global symbol from module-level ASM to the
/// defined list.
void LTOModule::addAsmGlobalSymbol(const char *name,
                                   lto_symbol_attributes scope) {
  StringSet::value_type &entry = _defines.GetOrCreateValue(name);

  // only add new define if not already defined
  if (entry.getValue())
    return;

  entry.setValue(1);

  NameAndAttributes &info = _undefines[entry.getKey().data()];

  if (info.symbol == nullptr) {
    // FIXME: This is trying to take care of module ASM like this:
    //
    //   module asm ".zerofill __FOO, __foo, _bar_baz_qux, 0"
    //
    // but is gross and its mother dresses it funny. Have the ASM parser give us
    // more details for this type of situation so that we're not guessing so
    // much.

    // fill information structure
    info.name = entry.getKey().data();
    info.attributes =
      LTO_SYMBOL_PERMISSIONS_DATA | LTO_SYMBOL_DEFINITION_REGULAR | scope;
    info.isFunction = false;
    info.symbol = nullptr;

    // add to table of symbols
    _symbols.push_back(info);
    return;
  }

  if (info.isFunction)
    addDefinedFunctionSymbol(info.name, cast<Function>(info.symbol));
  else
    addDefinedDataSymbol(info.name, info.symbol);

  _symbols.back().attributes &= ~LTO_SYMBOL_SCOPE_MASK;
  _symbols.back().attributes |= scope;
}

/// addAsmGlobalSymbolUndef - Add a global symbol from module-level ASM to the
/// undefined list.
void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
  StringMap<NameAndAttributes>::value_type &entry =
    _undefines.GetOrCreateValue(name);

  _asm_undefines.push_back(entry.getKey().data());

  // we already have the symbol
  if (entry.getValue().name)
    return;

  uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;
  attr |= LTO_SYMBOL_SCOPE_DEFAULT;
  NameAndAttributes info;
  info.name = entry.getKey().data();
  info.attributes = attr;
  info.isFunction = false;
  info.symbol = nullptr;

  entry.setValue(info);
}

/// Add a symbol which isn't defined just yet to a list to be resolved later.
void LTOModule::addPotentialUndefinedSymbol(const object::BasicSymbolRef &Sym,
                                            bool isFunc) {
  SmallString<64> name;
  {
    raw_svector_ostream OS(name);
    Sym.printName(OS);
  }

  StringMap<NameAndAttributes>::value_type &entry =
    _undefines.GetOrCreateValue(name);

  // we already have the symbol
  if (entry.getValue().name)
    return;

  NameAndAttributes info;

  info.name = entry.getKey().data();

  const GlobalValue *decl = IRFile->getSymbolGV(Sym.getRawDataRefImpl());

  if (decl->hasExternalWeakLinkage())
    info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
  else
    info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;

  info.isFunction = isFunc;
  info.symbol = decl;

  entry.setValue(info);
}

/// parseSymbols - Parse the symbols from the module and model-level ASM and add
/// them to either the defined or undefined lists.
bool LTOModule::parseSymbols(std::string &errMsg) {
  for (auto &Sym : IRFile->symbols()) {
    const GlobalValue *GV = IRFile->getSymbolGV(Sym.getRawDataRefImpl());
    uint32_t Flags = Sym.getFlags();
    if (Flags & object::BasicSymbolRef::SF_FormatSpecific)
      continue;

    bool IsUndefined = Flags & object::BasicSymbolRef::SF_Undefined;

    if (!GV) {
      SmallString<64> Buffer;
      {
        raw_svector_ostream OS(Buffer);
        Sym.printName(OS);
      }
      const char *Name = Buffer.c_str();

      if (IsUndefined)
        addAsmGlobalSymbolUndef(Name);
      else if (Flags & object::BasicSymbolRef::SF_Global)
        addAsmGlobalSymbol(Name, LTO_SYMBOL_SCOPE_DEFAULT);
      else
        addAsmGlobalSymbol(Name, LTO_SYMBOL_SCOPE_INTERNAL);
      continue;
    }

    auto *F = dyn_cast<Function>(GV);
    if (IsUndefined) {
      addPotentialUndefinedSymbol(Sym, F != nullptr);
      continue;
    }

    if (F) {
      addDefinedFunctionSymbol(Sym);
      continue;
    }

    if (isa<GlobalVariable>(GV)) {
      addDefinedDataSymbol(Sym);
      continue;
    }

    assert(isa<GlobalAlias>(GV));
    addDefinedDataSymbol(Sym);
  }

  // make symbols for all undefines
  for (StringMap<NameAndAttributes>::iterator u =_undefines.begin(),
         e = _undefines.end(); u != e; ++u) {
    // If this symbol also has a definition, then don't make an undefine because
    // it is a tentative definition.
    if (_defines.count(u->getKey())) continue;
    NameAndAttributes info = u->getValue();
    _symbols.push_back(info);
  }

  return false;
}

/// parseMetadata - Parse metadata from the module
void LTOModule::parseMetadata() {
  // Linker Options
  if (Value *Val = getModule().getModuleFlag("Linker Options")) {
    MDNode *LinkerOptions = cast<MDNode>(Val);
    for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
      MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
      for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
        MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
        StringRef Op = _linkeropt_strings.
            GetOrCreateValue(MDOption->getString()).getKey();
        StringRef DepLibName = _target->getSubtargetImpl()
                                   ->getTargetLowering()
                                   ->getObjFileLowering()
                                   .getDepLibFromLinkerOpt(Op);
        if (!DepLibName.empty())
          _deplibs.push_back(DepLibName.data());
        else if (!Op.empty())
          _linkeropts.push_back(Op.data());
      }
    }
  }

  // Add other interesting metadata here.
}