LTOModule.cpp revision 280031 
1//===-- LTOModule.cpp - LLVM Link Time Optimizer --------------------------===//
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 file implements the Link Time Optimization library. This library is
11// intended to be used by linker to optimize code at link time.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/LTO/LTOModule.h"
16#include "llvm/ADT/Triple.h"
17#include "llvm/Bitcode/ReaderWriter.h"
18#include "llvm/CodeGen/Analysis.h"
19#include "llvm/IR/Constants.h"
20#include "llvm/IR/DiagnosticPrinter.h"
21#include "llvm/IR/LLVMContext.h"
22#include "llvm/IR/Metadata.h"
23#include "llvm/IR/Module.h"
24#include "llvm/MC/MCExpr.h"
25#include "llvm/MC/MCInst.h"
26#include "llvm/MC/MCInstrInfo.h"
27#include "llvm/MC/MCParser/MCAsmParser.h"
28#include "llvm/MC/MCSection.h"
29#include "llvm/MC/MCSubtargetInfo.h"
30#include "llvm/MC/MCSymbol.h"
31#include "llvm/MC/MCTargetAsmParser.h"
32#include "llvm/MC/SubtargetFeature.h"
33#include "llvm/Object/IRObjectFile.h"
34#include "llvm/Object/ObjectFile.h"
35#include "llvm/Support/CommandLine.h"
36#include "llvm/Support/FileSystem.h"
37#include "llvm/Support/Host.h"
38#include "llvm/Support/MemoryBuffer.h"
39#include "llvm/Support/Path.h"
40#include "llvm/Support/SourceMgr.h"
41#include "llvm/Support/TargetRegistry.h"
42#include "llvm/Support/TargetSelect.h"
43#include "llvm/Target/TargetLowering.h"
44#include "llvm/Target/TargetLoweringObjectFile.h"
45#include "llvm/Target/TargetRegisterInfo.h"
46#include "llvm/Target/TargetSubtargetInfo.h"
47#include "llvm/Transforms/Utils/GlobalStatus.h"
48#include <system_error>
49using namespace llvm;
50using namespace llvm::object;
51
52LTOModule::LTOModule(std::unique_ptr<object::IRObjectFile> Obj,
53                     llvm::TargetMachine *TM)
54    : IRFile(std::move(Obj)), _target(TM) {}
55
56LTOModule::LTOModule(std::unique_ptr<object::IRObjectFile> Obj,
57                     llvm::TargetMachine *TM,
58                     std::unique_ptr<LLVMContext> Context)
59    : OwnedContext(std::move(Context)), IRFile(std::move(Obj)), _target(TM) {}
60
61LTOModule::~LTOModule() {}
62
63/// isBitcodeFile - Returns 'true' if the file (or memory contents) is LLVM
64/// bitcode.
65bool LTOModule::isBitcodeFile(const void *Mem, size_t Length) {
66  ErrorOr<MemoryBufferRef> BCData = IRObjectFile::findBitcodeInMemBuffer(
67      MemoryBufferRef(StringRef((const char *)Mem, Length), "<mem>"));
68  return bool(BCData);
69}
70
71bool LTOModule::isBitcodeFile(const char *Path) {
72  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
73      MemoryBuffer::getFile(Path);
74  if (!BufferOrErr)
75    return false;
76
77  ErrorOr<MemoryBufferRef> BCData = IRObjectFile::findBitcodeInMemBuffer(
78      BufferOrErr.get()->getMemBufferRef());
79  return bool(BCData);
80}
81
82bool LTOModule::isBitcodeForTarget(MemoryBuffer *Buffer,
83                                   StringRef TriplePrefix) {
84  ErrorOr<MemoryBufferRef> BCOrErr =
85      IRObjectFile::findBitcodeInMemBuffer(Buffer->getMemBufferRef());
86  if (!BCOrErr)
87    return false;
88  LLVMContext Context;
89  std::string Triple = getBitcodeTargetTriple(*BCOrErr, Context);
90  return StringRef(Triple).startswith(TriplePrefix);
91}
92
93LTOModule *LTOModule::createFromFile(const char *path, TargetOptions options,
94                                     std::string &errMsg) {
95  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
96      MemoryBuffer::getFile(path);
97  if (std::error_code EC = BufferOrErr.getError()) {
98    errMsg = EC.message();
99    return nullptr;
100  }
101  std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOrErr.get());
102  return makeLTOModule(Buffer->getMemBufferRef(), options, errMsg,
103                       &getGlobalContext());
104}
105
106LTOModule *LTOModule::createFromOpenFile(int fd, const char *path, size_t size,
107                                         TargetOptions options,
108                                         std::string &errMsg) {
109  return createFromOpenFileSlice(fd, path, size, 0, options, errMsg);
110}
111
112LTOModule *LTOModule::createFromOpenFileSlice(int fd, const char *path,
113                                              size_t map_size, off_t offset,
114                                              TargetOptions options,
115                                              std::string &errMsg) {
116  ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOrErr =
117      MemoryBuffer::getOpenFileSlice(fd, path, map_size, offset);
118  if (std::error_code EC = BufferOrErr.getError()) {
119    errMsg = EC.message();
120    return nullptr;
121  }
122  std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOrErr.get());
123  return makeLTOModule(Buffer->getMemBufferRef(), options, errMsg,
124                       &getGlobalContext());
125}
126
127LTOModule *LTOModule::createFromBuffer(const void *mem, size_t length,
128                                       TargetOptions options,
129                                       std::string &errMsg, StringRef path) {
130  return createInContext(mem, length, options, errMsg, path,
131                         &getGlobalContext());
132}
133
134LTOModule *LTOModule::createInLocalContext(const void *mem, size_t length,
135                                           TargetOptions options,
136                                           std::string &errMsg,
137                                           StringRef path) {
138  return createInContext(mem, length, options, errMsg, path, nullptr);
139}
140
141LTOModule *LTOModule::createInContext(const void *mem, size_t length,
142                                      TargetOptions options,
143                                      std::string &errMsg, StringRef path,
144                                      LLVMContext *Context) {
145  StringRef Data((const char *)mem, length);
146  MemoryBufferRef Buffer(Data, path);
147  return makeLTOModule(Buffer, options, errMsg, Context);
148}
149
150static Module *parseBitcodeFileImpl(MemoryBufferRef Buffer,
151                                    LLVMContext &Context, bool ShouldBeLazy,
152                                    std::string &ErrMsg) {
153
154  // Find the buffer.
155  ErrorOr<MemoryBufferRef> MBOrErr =
156      IRObjectFile::findBitcodeInMemBuffer(Buffer);
157  if (std::error_code EC = MBOrErr.getError()) {
158    ErrMsg = EC.message();
159    return nullptr;
160  }
161
162  std::function<void(const DiagnosticInfo &)> DiagnosticHandler =
163      [&ErrMsg](const DiagnosticInfo &DI) {
164        raw_string_ostream Stream(ErrMsg);
165        DiagnosticPrinterRawOStream DP(Stream);
166        DI.print(DP);
167      };
168
169  if (!ShouldBeLazy) {
170    // Parse the full file.
171    ErrorOr<Module *> M =
172        parseBitcodeFile(*MBOrErr, Context, DiagnosticHandler);
173    if (!M)
174      return nullptr;
175    return *M;
176  }
177
178  // Parse lazily.
179  std::unique_ptr<MemoryBuffer> LightweightBuf =
180      MemoryBuffer::getMemBuffer(*MBOrErr, false);
181  ErrorOr<Module *> M = getLazyBitcodeModule(std::move(LightweightBuf), Context,
182                                             DiagnosticHandler);
183  if (!M)
184    return nullptr;
185  return *M;
186}
187
188LTOModule *LTOModule::makeLTOModule(MemoryBufferRef Buffer,
189                                    TargetOptions options, std::string &errMsg,
190                                    LLVMContext *Context) {
191  std::unique_ptr<LLVMContext> OwnedContext;
192  if (!Context) {
193    OwnedContext = llvm::make_unique<LLVMContext>();
194    Context = OwnedContext.get();
195  }
196
197  // If we own a context, we know this is being used only for symbol
198  // extraction, not linking.  Be lazy in that case.
199  std::unique_ptr<Module> M(parseBitcodeFileImpl(
200      Buffer, *Context,
201      /* ShouldBeLazy */ static_cast<bool>(OwnedContext), errMsg));
202  if (!M)
203    return nullptr;
204
205  std::string TripleStr = M->getTargetTriple();
206  if (TripleStr.empty())
207    TripleStr = sys::getDefaultTargetTriple();
208  llvm::Triple Triple(TripleStr);
209
210  // find machine architecture for this module
211  const Target *march = TargetRegistry::lookupTarget(TripleStr, errMsg);
212  if (!march)
213    return nullptr;
214
215  // construct LTOModule, hand over ownership of module and target
216  SubtargetFeatures Features;
217  Features.getDefaultSubtargetFeatures(Triple);
218  std::string FeatureStr = Features.getString();
219  // Set a default CPU for Darwin triples.
220  std::string CPU;
221  if (Triple.isOSDarwin()) {
222    if (Triple.getArch() == llvm::Triple::x86_64)
223      CPU = "core2";
224    else if (Triple.getArch() == llvm::Triple::x86)
225      CPU = "yonah";
226    else if (Triple.getArch() == llvm::Triple::aarch64)
227      CPU = "cyclone";
228  }
229
230  TargetMachine *target = march->createTargetMachine(TripleStr, CPU, FeatureStr,
231                                                     options);
232  M->setDataLayout(target->getSubtargetImpl()->getDataLayout());
233
234  std::unique_ptr<object::IRObjectFile> IRObj(
235      new object::IRObjectFile(Buffer, std::move(M)));
236
237  LTOModule *Ret;
238  if (OwnedContext)
239    Ret = new LTOModule(std::move(IRObj), target, std::move(OwnedContext));
240  else
241    Ret = new LTOModule(std::move(IRObj), target);
242
243  if (Ret->parseSymbols(errMsg)) {
244    delete Ret;
245    return nullptr;
246  }
247
248  Ret->parseMetadata();
249
250  return Ret;
251}
252
253/// Create a MemoryBuffer from a memory range with an optional name.
254std::unique_ptr<MemoryBuffer>
255LTOModule::makeBuffer(const void *mem, size_t length, StringRef name) {
256  const char *startPtr = (const char*)mem;
257  return MemoryBuffer::getMemBuffer(StringRef(startPtr, length), name, false);
258}
259
260/// objcClassNameFromExpression - Get string that the data pointer points to.
261bool
262LTOModule::objcClassNameFromExpression(const Constant *c, std::string &name) {
263  if (const ConstantExpr *ce = dyn_cast<ConstantExpr>(c)) {
264    Constant *op = ce->getOperand(0);
265    if (GlobalVariable *gvn = dyn_cast<GlobalVariable>(op)) {
266      Constant *cn = gvn->getInitializer();
267      if (ConstantDataArray *ca = dyn_cast<ConstantDataArray>(cn)) {
268        if (ca->isCString()) {
269          name = ".objc_class_name_" + ca->getAsCString().str();
270          return true;
271        }
272      }
273    }
274  }
275  return false;
276}
277
278/// addObjCClass - Parse i386/ppc ObjC class data structure.
279void LTOModule::addObjCClass(const GlobalVariable *clgv) {
280  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
281  if (!c) return;
282
283  // second slot in __OBJC,__class is pointer to superclass name
284  std::string superclassName;
285  if (objcClassNameFromExpression(c->getOperand(1), superclassName)) {
286    auto IterBool =
287        _undefines.insert(std::make_pair(superclassName, NameAndAttributes()));
288    if (IterBool.second) {
289      NameAndAttributes &info = IterBool.first->second;
290      info.name = IterBool.first->first().data();
291      info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
292      info.isFunction = false;
293      info.symbol = clgv;
294    }
295  }
296
297  // third slot in __OBJC,__class is pointer to class name
298  std::string className;
299  if (objcClassNameFromExpression(c->getOperand(2), className)) {
300    auto Iter = _defines.insert(className).first;
301
302    NameAndAttributes info;
303    info.name = Iter->first().data();
304    info.attributes = LTO_SYMBOL_PERMISSIONS_DATA |
305      LTO_SYMBOL_DEFINITION_REGULAR | LTO_SYMBOL_SCOPE_DEFAULT;
306    info.isFunction = false;
307    info.symbol = clgv;
308    _symbols.push_back(info);
309  }
310}
311
312/// addObjCCategory - Parse i386/ppc ObjC category data structure.
313void LTOModule::addObjCCategory(const GlobalVariable *clgv) {
314  const ConstantStruct *c = dyn_cast<ConstantStruct>(clgv->getInitializer());
315  if (!c) return;
316
317  // second slot in __OBJC,__category is pointer to target class name
318  std::string targetclassName;
319  if (!objcClassNameFromExpression(c->getOperand(1), targetclassName))
320    return;
321
322  auto IterBool =
323      _undefines.insert(std::make_pair(targetclassName, NameAndAttributes()));
324
325  if (!IterBool.second)
326    return;
327
328  NameAndAttributes &info = IterBool.first->second;
329  info.name = IterBool.first->first().data();
330  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
331  info.isFunction = false;
332  info.symbol = clgv;
333}
334
335/// addObjCClassRef - Parse i386/ppc ObjC class list data structure.
336void LTOModule::addObjCClassRef(const GlobalVariable *clgv) {
337  std::string targetclassName;
338  if (!objcClassNameFromExpression(clgv->getInitializer(), targetclassName))
339    return;
340
341  auto IterBool =
342      _undefines.insert(std::make_pair(targetclassName, NameAndAttributes()));
343
344  if (!IterBool.second)
345    return;
346
347  NameAndAttributes &info = IterBool.first->second;
348  info.name = IterBool.first->first().data();
349  info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
350  info.isFunction = false;
351  info.symbol = clgv;
352}
353
354void LTOModule::addDefinedDataSymbol(const object::BasicSymbolRef &Sym) {
355  SmallString<64> Buffer;
356  {
357    raw_svector_ostream OS(Buffer);
358    Sym.printName(OS);
359  }
360
361  const GlobalValue *V = IRFile->getSymbolGV(Sym.getRawDataRefImpl());
362  addDefinedDataSymbol(Buffer.c_str(), V);
363}
364
365void LTOModule::addDefinedDataSymbol(const char *Name, const GlobalValue *v) {
366  // Add to list of defined symbols.
367  addDefinedSymbol(Name, v, false);
368
369  if (!v->hasSection() /* || !isTargetDarwin */)
370    return;
371
372  // Special case i386/ppc ObjC data structures in magic sections:
373  // The issue is that the old ObjC object format did some strange
374  // contortions to avoid real linker symbols.  For instance, the
375  // ObjC class data structure is allocated statically in the executable
376  // that defines that class.  That data structures contains a pointer to
377  // its superclass.  But instead of just initializing that part of the
378  // struct to the address of its superclass, and letting the static and
379  // dynamic linkers do the rest, the runtime works by having that field
380  // instead point to a C-string that is the name of the superclass.
381  // At runtime the objc initialization updates that pointer and sets
382  // it to point to the actual super class.  As far as the linker
383  // knows it is just a pointer to a string.  But then someone wanted the
384  // linker to issue errors at build time if the superclass was not found.
385  // So they figured out a way in mach-o object format to use an absolute
386  // symbols (.objc_class_name_Foo = 0) and a floating reference
387  // (.reference .objc_class_name_Bar) to cause the linker into erroring when
388  // a class was missing.
389  // The following synthesizes the implicit .objc_* symbols for the linker
390  // from the ObjC data structures generated by the front end.
391
392  // special case if this data blob is an ObjC class definition
393  std::string Section = v->getSection();
394  if (Section.compare(0, 15, "__OBJC,__class,") == 0) {
395    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
396      addObjCClass(gv);
397    }
398  }
399
400  // special case if this data blob is an ObjC category definition
401  else if (Section.compare(0, 18, "__OBJC,__category,") == 0) {
402    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
403      addObjCCategory(gv);
404    }
405  }
406
407  // special case if this data blob is the list of referenced classes
408  else if (Section.compare(0, 18, "__OBJC,__cls_refs,") == 0) {
409    if (const GlobalVariable *gv = dyn_cast<GlobalVariable>(v)) {
410      addObjCClassRef(gv);
411    }
412  }
413}
414
415void LTOModule::addDefinedFunctionSymbol(const object::BasicSymbolRef &Sym) {
416  SmallString<64> Buffer;
417  {
418    raw_svector_ostream OS(Buffer);
419    Sym.printName(OS);
420  }
421
422  const Function *F =
423      cast<Function>(IRFile->getSymbolGV(Sym.getRawDataRefImpl()));
424  addDefinedFunctionSymbol(Buffer.c_str(), F);
425}
426
427void LTOModule::addDefinedFunctionSymbol(const char *Name, const Function *F) {
428  // add to list of defined symbols
429  addDefinedSymbol(Name, F, true);
430}
431
432void LTOModule::addDefinedSymbol(const char *Name, const GlobalValue *def,
433                                 bool isFunction) {
434  // set alignment part log2() can have rounding errors
435  uint32_t align = def->getAlignment();
436  uint32_t attr = align ? countTrailingZeros(align) : 0;
437
438  // set permissions part
439  if (isFunction) {
440    attr |= LTO_SYMBOL_PERMISSIONS_CODE;
441  } else {
442    const GlobalVariable *gv = dyn_cast<GlobalVariable>(def);
443    if (gv && gv->isConstant())
444      attr |= LTO_SYMBOL_PERMISSIONS_RODATA;
445    else
446      attr |= LTO_SYMBOL_PERMISSIONS_DATA;
447  }
448
449  // set definition part
450  if (def->hasWeakLinkage() || def->hasLinkOnceLinkage())
451    attr |= LTO_SYMBOL_DEFINITION_WEAK;
452  else if (def->hasCommonLinkage())
453    attr |= LTO_SYMBOL_DEFINITION_TENTATIVE;
454  else
455    attr |= LTO_SYMBOL_DEFINITION_REGULAR;
456
457  // set scope part
458  if (def->hasLocalLinkage())
459    // Ignore visibility if linkage is local.
460    attr |= LTO_SYMBOL_SCOPE_INTERNAL;
461  else if (def->hasHiddenVisibility())
462    attr |= LTO_SYMBOL_SCOPE_HIDDEN;
463  else if (def->hasProtectedVisibility())
464    attr |= LTO_SYMBOL_SCOPE_PROTECTED;
465  else if (canBeOmittedFromSymbolTable(def))
466    attr |= LTO_SYMBOL_SCOPE_DEFAULT_CAN_BE_HIDDEN;
467  else
468    attr |= LTO_SYMBOL_SCOPE_DEFAULT;
469
470  auto Iter = _defines.insert(Name).first;
471
472  // fill information structure
473  NameAndAttributes info;
474  StringRef NameRef = Iter->first();
475  info.name = NameRef.data();
476  assert(info.name[NameRef.size()] == '\0');
477  info.attributes = attr;
478  info.isFunction = isFunction;
479  info.symbol = def;
480
481  // add to table of symbols
482  _symbols.push_back(info);
483}
484
485/// addAsmGlobalSymbol - Add a global symbol from module-level ASM to the
486/// defined list.
487void LTOModule::addAsmGlobalSymbol(const char *name,
488                                   lto_symbol_attributes scope) {
489  auto IterBool = _defines.insert(name);
490
491  // only add new define if not already defined
492  if (!IterBool.second)
493    return;
494
495  NameAndAttributes &info = _undefines[IterBool.first->first().data()];
496
497  if (info.symbol == nullptr) {
498    // FIXME: This is trying to take care of module ASM like this:
499    //
500    //   module asm ".zerofill __FOO, __foo, _bar_baz_qux, 0"
501    //
502    // but is gross and its mother dresses it funny. Have the ASM parser give us
503    // more details for this type of situation so that we're not guessing so
504    // much.
505
506    // fill information structure
507    info.name = IterBool.first->first().data();
508    info.attributes =
509      LTO_SYMBOL_PERMISSIONS_DATA | LTO_SYMBOL_DEFINITION_REGULAR | scope;
510    info.isFunction = false;
511    info.symbol = nullptr;
512
513    // add to table of symbols
514    _symbols.push_back(info);
515    return;
516  }
517
518  if (info.isFunction)
519    addDefinedFunctionSymbol(info.name, cast<Function>(info.symbol));
520  else
521    addDefinedDataSymbol(info.name, info.symbol);
522
523  _symbols.back().attributes &= ~LTO_SYMBOL_SCOPE_MASK;
524  _symbols.back().attributes |= scope;
525}
526
527/// addAsmGlobalSymbolUndef - Add a global symbol from module-level ASM to the
528/// undefined list.
529void LTOModule::addAsmGlobalSymbolUndef(const char *name) {
530  auto IterBool = _undefines.insert(std::make_pair(name, NameAndAttributes()));
531
532  _asm_undefines.push_back(IterBool.first->first().data());
533
534  // we already have the symbol
535  if (!IterBool.second)
536    return;
537
538  uint32_t attr = LTO_SYMBOL_DEFINITION_UNDEFINED;
539  attr |= LTO_SYMBOL_SCOPE_DEFAULT;
540  NameAndAttributes &info = IterBool.first->second;
541  info.name = IterBool.first->first().data();
542  info.attributes = attr;
543  info.isFunction = false;
544  info.symbol = nullptr;
545}
546
547/// Add a symbol which isn't defined just yet to a list to be resolved later.
548void LTOModule::addPotentialUndefinedSymbol(const object::BasicSymbolRef &Sym,
549                                            bool isFunc) {
550  SmallString<64> name;
551  {
552    raw_svector_ostream OS(name);
553    Sym.printName(OS);
554  }
555
556  auto IterBool = _undefines.insert(std::make_pair(name, NameAndAttributes()));
557
558  // we already have the symbol
559  if (!IterBool.second)
560    return;
561
562  NameAndAttributes &info = IterBool.first->second;
563
564  info.name = IterBool.first->first().data();
565
566  const GlobalValue *decl = IRFile->getSymbolGV(Sym.getRawDataRefImpl());
567
568  if (decl->hasExternalWeakLinkage())
569    info.attributes = LTO_SYMBOL_DEFINITION_WEAKUNDEF;
570  else
571    info.attributes = LTO_SYMBOL_DEFINITION_UNDEFINED;
572
573  info.isFunction = isFunc;
574  info.symbol = decl;
575}
576
577/// parseSymbols - Parse the symbols from the module and model-level ASM and add
578/// them to either the defined or undefined lists.
579bool LTOModule::parseSymbols(std::string &errMsg) {
580  for (auto &Sym : IRFile->symbols()) {
581    const GlobalValue *GV = IRFile->getSymbolGV(Sym.getRawDataRefImpl());
582    uint32_t Flags = Sym.getFlags();
583    if (Flags & object::BasicSymbolRef::SF_FormatSpecific)
584      continue;
585
586    bool IsUndefined = Flags & object::BasicSymbolRef::SF_Undefined;
587
588    if (!GV) {
589      SmallString<64> Buffer;
590      {
591        raw_svector_ostream OS(Buffer);
592        Sym.printName(OS);
593      }
594      const char *Name = Buffer.c_str();
595
596      if (IsUndefined)
597        addAsmGlobalSymbolUndef(Name);
598      else if (Flags & object::BasicSymbolRef::SF_Global)
599        addAsmGlobalSymbol(Name, LTO_SYMBOL_SCOPE_DEFAULT);
600      else
601        addAsmGlobalSymbol(Name, LTO_SYMBOL_SCOPE_INTERNAL);
602      continue;
603    }
604
605    auto *F = dyn_cast<Function>(GV);
606    if (IsUndefined) {
607      addPotentialUndefinedSymbol(Sym, F != nullptr);
608      continue;
609    }
610
611    if (F) {
612      addDefinedFunctionSymbol(Sym);
613      continue;
614    }
615
616    if (isa<GlobalVariable>(GV)) {
617      addDefinedDataSymbol(Sym);
618      continue;
619    }
620
621    assert(isa<GlobalAlias>(GV));
622    addDefinedDataSymbol(Sym);
623  }
624
625  // make symbols for all undefines
626  for (StringMap<NameAndAttributes>::iterator u =_undefines.begin(),
627         e = _undefines.end(); u != e; ++u) {
628    // If this symbol also has a definition, then don't make an undefine because
629    // it is a tentative definition.
630    if (_defines.count(u->getKey())) continue;
631    NameAndAttributes info = u->getValue();
632    _symbols.push_back(info);
633  }
634
635  return false;
636}
637
638/// parseMetadata - Parse metadata from the module
639void LTOModule::parseMetadata() {
640  // Linker Options
641  if (Metadata *Val = getModule().getModuleFlag("Linker Options")) {
642    MDNode *LinkerOptions = cast<MDNode>(Val);
643    for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
644      MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
645      for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
646        MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
647        // FIXME: Make StringSet::insert match Self-Associative Container
648        // requirements, returning <iter,bool> rather than bool, and use that
649        // here.
650        StringRef Op =
651            _linkeropt_strings.insert(MDOption->getString()).first->first();
652        StringRef DepLibName = _target->getSubtargetImpl()
653                                   ->getTargetLowering()
654                                   ->getObjFileLowering()
655                                   .getDepLibFromLinkerOpt(Op);
656        if (!DepLibName.empty())
657          _deplibs.push_back(DepLibName.data());
658        else if (!Op.empty())
659          _linkeropts.push_back(Op.data());
660      }
661    }
662  }
663
664  // Add other interesting metadata here.
665}
666