C++ global_iterator::hasLocalLinkage方法代码示例

/// StripSymbolNames - Strip symbol names.
static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {

  SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
  findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
  findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues);

  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I) {
    if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
      if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
        I->setName("");     // Internal symbols can't participate in linkage
  }
  
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
    if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
      if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
        I->setName("");     // Internal symbols can't participate in linkage
    StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
  }
  
  // Remove all names from types.
  StripTypeSymtab(M.getTypeSymbolTable(), PreserveDbgInfo);

  return true;
}

/// AnalyzeGlobals - Scan through the users of all of the internal
/// GlobalValue's in the program.  If none of them have their "address taken"
/// (really, their address passed to something nontrivial), record this fact,
/// and record the functions that they are used directly in.
void GlobalsModRef::AnalyzeGlobals(Module &M) {
  std::vector<Function*> Readers, Writers;
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (I->hasLocalLinkage()) {
      if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
        // Remember that we are tracking this global.
        NonAddressTakenGlobals.insert(I);
        ++NumNonAddrTakenFunctions;
      }
      Readers.clear(); Writers.clear();
    }

  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    if (I->hasLocalLinkage()) {
      if (!AnalyzeUsesOfPointer(I, Readers, Writers)) {
        // Remember that we are tracking this global, and the mod/ref fns
        NonAddressTakenGlobals.insert(I);

        for (unsigned i = 0, e = Readers.size(); i != e; ++i)
          FunctionInfo[Readers[i]].GlobalInfo[I] |= Ref;

        if (!I->isConstant())  // No need to keep track of writers to constants
          for (unsigned i = 0, e = Writers.size(); i != e; ++i)
            FunctionInfo[Writers[i]].GlobalInfo[I] |= Mod;
        ++NumNonAddrTakenGlobalVars;

        // If this global holds a pointer type, see if it is an indirect global.
        if (I->getType()->getElementType()->isPointerTy() &&
            AnalyzeIndirectGlobalMemory(I))
          ++NumIndirectGlobalVars;
      }
      Readers.clear(); Writers.clear();
    }
}

bool GlobalMerge::doInitialization(Module &M) {
  DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
                                                        BSSGlobals;
  const DataLayout *TD = TLI->getDataLayout();
  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
  bool Changed = false;

  // Grab all non-const globals.
  for (Module::global_iterator I = M.global_begin(),
         E = M.global_end(); I != E; ++I) {
    // Merge is safe for "normal" internal globals only
    if (!I->hasLocalLinkage() || I->isThreadLocal() || I->hasSection())
      continue;

    PointerType *PT = dyn_cast<PointerType>(I->getType());
    assert(PT && "Global variable is not a pointer!");

    unsigned AddressSpace = PT->getAddressSpace();

    // Ignore fancy-aligned globals for now.
    unsigned Alignment = TD->getPreferredAlignment(I);
    Type *Ty = I->getType()->getElementType();
    if (Alignment > TD->getABITypeAlignment(Ty))
      continue;

    // Ignore all 'special' globals.
    if (I->getName().startswith("llvm.") ||
        I->getName().startswith(".llvm."))
      continue;

    if (TD->getTypeAllocSize(Ty) < MaxOffset) {
      if (TargetLoweringObjectFile::getKindForGlobal(I, TLI->getTargetMachine())
          .isBSSLocal())
        BSSGlobals[AddressSpace].push_back(I);
      else if (I->isConstant())
        ConstGlobals[AddressSpace].push_back(I);
      else
        Globals[AddressSpace].push_back(I);
    }
  }

  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
       I = Globals.begin(), E = Globals.end(); I != E; ++I)
    if (I->second.size() > 1)
      Changed |= doMerge(I->second, M, false, I->first);

  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
       I = BSSGlobals.begin(), E = BSSGlobals.end(); I != E; ++I)
    if (I->second.size() > 1)
      Changed |= doMerge(I->second, M, false, I->first);

  // FIXME: This currently breaks the EH processing due to way how the
  // typeinfo detection works. We might want to detect the TIs and ignore
  // them in the future.
  // if (ConstGlobals.size() > 1)
  //  Changed |= doMerge(ConstGlobals, M, true);

  return Changed;
}

bool ARMGlobalMerge::doInitialization(Module &M) {
  SmallVector<GlobalVariable*, 16> Globals, ConstGlobals, BSSGlobals;
  const TargetData *TD = TLI->getTargetData();
  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
  bool Changed = false;

  // Disable this pass on darwin. The debugger is not yet ready to extract
  // variable's  info from a merged global.
  if (TLI->getTargetMachine().getSubtarget<ARMSubtarget>().isTargetDarwin())
    return false;

  // Grab all non-const globals.
  for (Module::global_iterator I = M.global_begin(),
         E = M.global_end(); I != E; ++I) {
    // Merge is safe for "normal" internal globals only
    if (!I->hasLocalLinkage() || I->isThreadLocal() || I->hasSection())
      continue;

    // Ignore fancy-aligned globals for now.
    if (I->getAlignment() != 0)
      continue;

    // Ignore all 'special' globals.
    if (I->getName().startswith("llvm.") ||
        I->getName().startswith(".llvm."))
      continue;

    if (TD->getTypeAllocSize(I->getType()->getElementType()) < MaxOffset) {
      const TargetLoweringObjectFile &TLOF = TLI->getObjFileLowering();
      if (TLOF.getKindForGlobal(I, TLI->getTargetMachine()).isBSSLocal())
        BSSGlobals.push_back(I);
      else if (I->isConstant())
        ConstGlobals.push_back(I);
      else
        Globals.push_back(I);
    }
  }

  if (Globals.size() > 1)
    Changed |= doMerge(Globals, M, false);
  if (BSSGlobals.size() > 1)
    Changed |= doMerge(BSSGlobals, M, false);

  // FIXME: This currently breaks the EH processing due to way how the 
  // typeinfo detection works. We might want to detect the TIs and ignore 
  // them in the future.
  // if (ConstGlobals.size() > 1)
  //  Changed |= doMerge(ConstGlobals, M, true);

  return Changed;
}

/// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
/// exist in an LLVM module. This is a bit tricky because there may be two
/// symbols with the same name but different LLVM types that will be resolved to
/// each other but aren't currently (thus we need to treat it as resolved).
///
/// Inputs:
///  M - The module in which to find undefined symbols.
///
/// Outputs:
///  UndefinedSymbols - A set of C++ strings containing the name of all
///                     undefined symbols.
///
static void
GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
  std::set<std::string> DefinedSymbols;
  UndefinedSymbols.clear();

  // If the program doesn't define a main, try pulling one in from a .a file.
  // This is needed for programs where the main function is defined in an
  // archive, such f2c'd programs.
  Function *Main = M->getFunction("main");
  if (Main == 0 || Main->isDeclaration())
    UndefinedSymbols.insert("main");

  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    if (I->hasName()) {
      if (I->isDeclaration())
        UndefinedSymbols.insert(I->getName());
      else if (!I->hasLocalLinkage()) {
        assert(!I->hasDLLImportLinkage()
               && "Found dllimported non-external symbol!");
        DefinedSymbols.insert(I->getName());
      }      
    }

  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I)
    if (I->hasName()) {
      if (I->isDeclaration())
        UndefinedSymbols.insert(I->getName());
      else if (!I->hasLocalLinkage()) {
        assert(!I->hasDLLImportLinkage()
               && "Found dllimported non-external symbol!");
        DefinedSymbols.insert(I->getName());
      }      
    }

  for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I)
    if (I->hasName())
      DefinedSymbols.insert(I->getName());

  // Prune out any defined symbols from the undefined symbols set...
  for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
       I != UndefinedSymbols.end(); )
    if (DefinedSymbols.count(*I))
      UndefinedSymbols.erase(I++);  // This symbol really is defined!
    else
      ++I; // Keep this symbol in the undefined symbols list
}

void
AndroidBitcodeLinker::GetAllSymbols(Module *M,
  std::set<std::string> &UndefinedSymbols,
  std::set<std::string> &DefinedSymbols) {

  UndefinedSymbols.clear();
  DefinedSymbols.clear();

  Function *Main = M->getFunction("main");
  if (Main == 0 || Main->isDeclaration())
    UndefinedSymbols.insert("main");

  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    if (I->hasName()) {
      if (I->isDeclaration())
        UndefinedSymbols.insert(I->getName());
      else if (!I->hasLocalLinkage()) {
        assert(!I->hasDLLImportStorageClass()
               && "Found dllimported non-external symbol!");
        DefinedSymbols.insert(I->getName());
      }
    }

  for (Module::global_iterator I = M->global_begin(), E = M->global_end();
       I != E; ++I)
    if (I->hasName()) {
      if (I->isDeclaration())
        UndefinedSymbols.insert(I->getName());
      else if (!I->hasLocalLinkage()) {
        assert(!I->hasDLLImportStorageClass()
               && "Found dllimported non-external symbol!");
        DefinedSymbols.insert(I->getName());
      }
    }

  for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
       I != E; ++I)
    if (I->hasName())
      DefinedSymbols.insert(I->getName());

  for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
       I != UndefinedSymbols.end(); )
    if (DefinedSymbols.count(*I))
      UndefinedSymbols.erase(I++);
    else
      ++I;
}

/**
 * Print the field declarations.
 */
void JVMWriter::printFields() {
    out << "; Fields\n";
    for(Module::global_iterator i = module->global_begin(),
                                e = module->global_end(); i != e; i++) {
        if(i->isDeclaration()) {
            out << ".extern field ";
            externRefs.insert(i);
        } else
            out << ".field "
                << (i->hasLocalLinkage() ? "private " : "public ")
                << "static final ";
        out << getValueName(i) << ' ' << getTypeDescriptor(i->getType());
        if(debug >= 3)
            out << " ; " << *i;
        else
            out << '\n';
    }
    out << '\n';
}

static void getSymbols(Module*M, std::vector<std::string>& symbols) {
    // Loop over global variables
    for (Module::global_iterator GI = M->global_begin(), GE=M->global_end(); GI != GE; ++GI)
        if (!GI->isDeclaration() && !GI->hasLocalLinkage())
            if (!GI->getName().empty())
                symbols.push_back(GI->getName());

    // Loop over functions
    for (Module::iterator FI = M->begin(), FE = M->end(); FI != FE; ++FI)
        if (!FI->isDeclaration() && !FI->hasLocalLinkage())
            if (!FI->getName().empty())
                symbols.push_back(FI->getName());

    // Loop over aliases
    for (Module::alias_iterator AI = M->alias_begin(), AE = M->alias_end();
            AI != AE; ++AI) {
        if (AI->hasName())
            symbols.push_back(AI->getName());
    }
}

bool ARMGlobalMerge::doInitialization(Module &M) {
  SmallVector<GlobalVariable*, 16> Globals, ConstGlobals;
  const TargetData *TD = TLI->getTargetData();
  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
  bool Changed = false;

  // Grab all non-const globals.
  for (Module::global_iterator I = M.global_begin(),
         E = M.global_end(); I != E; ++I) {
    // Merge is safe for "normal" internal globals only
    if (!I->hasLocalLinkage() || I->isThreadLocal() || I->hasSection())
      continue;

    // Ignore fancy-aligned globals for now.
    if (I->getAlignment() != 0)
      continue;

    // Ignore all 'special' globals.
    if (I->getName().startswith("llvm.") ||
        I->getName().startswith(".llvm."))
      continue;

    if (TD->getTypeAllocSize(I->getType()) < MaxOffset) {
      if (I->isConstant())
        ConstGlobals.push_back(I);
      else
        Globals.push_back(I);
    }
  }

  if (Globals.size() > 1)
    Changed |= doMerge(Globals, M, false);
  // FIXME: This currently breaks the EH processing due to way how the 
  // typeinfo detection works. We might want to detect the TIs and ignore 
  // them in the future.
  
  // if (ConstGlobals.size() > 1)
  //  Changed |= doMerge(ConstGlobals, M, true);

  return Changed;
}

static int runCompilePasses(Module *ModuleRef,
                            unsigned ModuleIndex,
                            ThreadedFunctionQueue *FuncQueue,
                            const Triple &TheTriple,
                            TargetMachine &Target,
                            StringRef ProgramName,
                            raw_pwrite_stream &OS){
  PNaClABIErrorReporter ABIErrorReporter;

  if (SplitModuleCount > 1 || ExternalizeAll) {
    // Add function and global names, and give them external linkage.
    // This relies on LLVM's consistent auto-generation of names, we could
    // maybe do our own in case something changes there.
    for (Function &F : *ModuleRef) {
      if (!F.hasName())
        F.setName("Function");
      if (F.hasInternalLinkage())
        F.setLinkage(GlobalValue::ExternalLinkage);
    }
    for (Module::global_iterator GI = ModuleRef->global_begin(),
         GE = ModuleRef->global_end();
         GI != GE; ++GI) {
      if (!GI->hasName())
        GI->setName("Global");
      if (GI->hasInternalLinkage())
        GI->setLinkage(GlobalValue::ExternalLinkage);
    }
    if (ModuleIndex > 0) {
      // Remove the initializers for all global variables, turning them into
      // declarations.
      for (Module::global_iterator GI = ModuleRef->global_begin(),
          GE = ModuleRef->global_end();
          GI != GE; ++GI) {
        assert(GI->hasInitializer() && "Global variable missing initializer");
        Constant *Init = GI->getInitializer();
        GI->setInitializer(nullptr);
        if (Init->getNumUses() == 0)
          Init->destroyConstant();
      }
    }
  }

  // Make all non-weak symbols hidden for better code. We cannot do
  // this for weak symbols. The linker complains when some weak
  // symbols are not resolved.
  for (Function &F : *ModuleRef) {
    if (!F.isWeakForLinker() && !F.hasLocalLinkage())
      F.setVisibility(GlobalValue::HiddenVisibility);
  }
  for (Module::global_iterator GI = ModuleRef->global_begin(),
           GE = ModuleRef->global_end();
       GI != GE; ++GI) {
    if (!GI->isWeakForLinker() && !GI->hasLocalLinkage())
      GI->setVisibility(GlobalValue::HiddenVisibility);
  }

  // Build up all of the passes that we want to do to the module.
  std::unique_ptr<legacy::PassManagerBase> PM;
  if (LazyBitcode)
    PM.reset(new legacy::FunctionPassManager(ModuleRef));
  else
    PM.reset(new legacy::PassManager());

  // Add the target data from the target machine, if it exists, or the module.
  if (const DataLayout *DL = Target.getDataLayout())
    ModuleRef->setDataLayout(*DL);

  // For conformance with llc, we let the user disable LLVM IR verification with
  // -disable-verify. Unlike llc, when LLVM IR verification is enabled we only
  // run it once, before PNaCl ABI verification.
  if (!NoVerify)
    PM->add(createVerifierPass());

  // Add the ABI verifier pass before the analysis and code emission passes.
  if (PNaClABIVerify)
    PM->add(createPNaClABIVerifyFunctionsPass(&ABIErrorReporter));

  // Add the intrinsic resolution pass. It assumes ABI-conformant code.
  PM->add(createResolvePNaClIntrinsicsPass());

  // Add an appropriate TargetLibraryInfo pass for the module's triple.
  TargetLibraryInfoImpl TLII(TheTriple);

  // The -disable-simplify-libcalls flag actually disables all builtin optzns.
  if (DisableSimplifyLibCalls)
    TLII.disableAllFunctions();
  PM->add(new TargetLibraryInfoWrapperPass(TLII));

  // Allow subsequent passes and the backend to better optimize instructions
  // that were simplified for PNaCl's ABI. This pass uses the TargetLibraryInfo
  // above.
  PM->add(createBackendCanonicalizePass());

  // Ask the target to add backend passes as necessary. We explicitly ask it
  // not to add the verifier pass because we added it earlier.
  if (Target.addPassesToEmitFile(*PM, OS, FileType,
                                 /* DisableVerify */ true)) {
    errs() << ProgramName
    << ": target does not support generation of this file type!\n";
    return 1;
//.........这里部分代码省略.........

bool InternalizePass::runOnModule(Module &M) {
  CallGraph *CG = getAnalysisIfAvailable<CallGraph>();
  CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : 0;
  
  if (ExternalNames.empty()) {
    // Return if we're not in 'all but main' mode and have no external api
    if (!AllButMain)
      return false;
    // If no list or file of symbols was specified, check to see if there is a
    // "main" symbol defined in the module.  If so, use it, otherwise do not
    // internalize the module, it must be a library or something.
    //
    Function *MainFunc = M.getFunction("main");
    if (MainFunc == 0 || MainFunc->isDeclaration())
      return false;  // No main found, must be a library...

    // Preserve main, internalize all else.
    ExternalNames.insert(MainFunc->getName());
  }

  bool Changed = false;

  // Never internalize functions which code-gen might insert.
  ExternalNames.insert("__stack_chk_fail");

  // Mark all functions not in the api as internal.
  // FIXME: maybe use private linkage?
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (!I->isDeclaration() &&         // Function must be defined here
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !I->hasLocalLinkage() &&  // Can't already have internal linkage
        !ExternalNames.count(I->getName())) {// Not marked to keep external?
      I->setLinkage(GlobalValue::InternalLinkage);
      // Remove a callgraph edge from the external node to this function.
      if (ExternalNode) ExternalNode->removeOneAbstractEdgeTo((*CG)[I]);
      Changed = true;
      ++NumFunctions;
      DEBUG(dbgs() << "Internalizing func " << I->getName() << "\n");
    }

  // Never internalize the llvm.used symbol.  It is used to implement
  // attribute((used)).
  // FIXME: Shouldn't this just filter on llvm.metadata section??
  ExternalNames.insert("llvm.used");
  ExternalNames.insert("llvm.compiler.used");

  // Never internalize anchors used by the machine module info, else the info
  // won't find them.  (see MachineModuleInfo.)
  ExternalNames.insert("llvm.global_ctors");
  ExternalNames.insert("llvm.global_dtors");
  ExternalNames.insert("llvm.global.annotations");

  // Never internalize symbols code-gen inserts.
  ExternalNames.insert("__stack_chk_guard");

  // Mark all global variables with initializers that are not in the api as
  // internal as well.
  // FIXME: maybe use private linkage?
  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    if (!I->isDeclaration() && !I->hasLocalLinkage() &&
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !ExternalNames.count(I->getName())) {
      I->setLinkage(GlobalValue::InternalLinkage);
      Changed = true;
      ++NumGlobals;
      DEBUG(dbgs() << "Internalized gvar " << I->getName() << "\n");
    }

  // Mark all aliases that are not in the api as internal as well.
  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
       I != E; ++I)
    if (!I->isDeclaration() && !I->hasInternalLinkage() &&
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !ExternalNames.count(I->getName())) {
      I->setLinkage(GlobalValue::InternalLinkage);
      Changed = true;
      ++NumAliases;
      DEBUG(dbgs() << "Internalized alias " << I->getName() << "\n");
    }

  return Changed;
}

bool GlobalMerge::doInitialization(Module &M) {
  if (!EnableGlobalMerge)
    return false;

  DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
                                                        BSSGlobals;
  const TargetLowering *TLI = TM->getTargetLowering();
  const DataLayout *DL = TLI->getDataLayout();
  unsigned MaxOffset = TLI->getMaximalGlobalOffset();
  bool Changed = false;
  setMustKeepGlobalVariables(M);

  // Grab all non-const globals.
  for (Module::global_iterator I = M.global_begin(),
         E = M.global_end(); I != E; ++I) {
    // Merge is safe for "normal" internal globals only
    if (!I->hasLocalLinkage() || I->isThreadLocal() || I->hasSection())
      continue;

    PointerType *PT = dyn_cast<PointerType>(I->getType());
    assert(PT && "Global variable is not a pointer!");

    unsigned AddressSpace = PT->getAddressSpace();

    // Ignore fancy-aligned globals for now.
    unsigned Alignment = DL->getPreferredAlignment(I);
    Type *Ty = I->getType()->getElementType();
    if (Alignment > DL->getABITypeAlignment(Ty))
      continue;

    // Ignore all 'special' globals.
    if (I->getName().startswith("llvm.") ||
        I->getName().startswith(".llvm."))
      continue;

    // Ignore all "required" globals:
    if (isMustKeepGlobalVariable(I))
      continue;

    if (DL->getTypeAllocSize(Ty) < MaxOffset) {
      if (TargetLoweringObjectFile::getKindForGlobal(I, TLI->getTargetMachine())
          .isBSSLocal())
        BSSGlobals[AddressSpace].push_back(I);
      else if (I->isConstant())
        ConstGlobals[AddressSpace].push_back(I);
      else
        Globals[AddressSpace].push_back(I);
    }
  }

  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
       I = Globals.begin(), E = Globals.end(); I != E; ++I)
    if (I->second.size() > 1)
      Changed |= doMerge(I->second, M, false, I->first);

  for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
       I = BSSGlobals.begin(), E = BSSGlobals.end(); I != E; ++I)
    if (I->second.size() > 1)
      Changed |= doMerge(I->second, M, false, I->first);

  if (EnableGlobalMergeOnConst)
    for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
         I = ConstGlobals.begin(), E = ConstGlobals.end(); I != E; ++I)
      if (I->second.size() > 1)
        Changed |= doMerge(I->second, M, true, I->first);

  return Changed;
}

bool InternalizePass::runOnModule(Module &M) {
  CallGraph *CG = getAnalysisIfAvailable<CallGraph>();
  CallGraphNode *ExternalNode = CG ? CG->getExternalCallingNode() : 0;
  bool Changed = false;

  // Never internalize functions which code-gen might insert.
  // FIXME: We should probably add this (and the __stack_chk_guard) via some
  // type of call-back in CodeGen.
  ExternalNames.insert("__stack_chk_fail");

  // Mark all functions not in the api as internal.
  // FIXME: maybe use private linkage?
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    if (!I->isDeclaration() &&         // Function must be defined here
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !I->hasLocalLinkage() &&  // Can't already have internal linkage
        !ExternalNames.count(I->getName())) {// Not marked to keep external?
      I->setLinkage(GlobalValue::InternalLinkage);
      // Remove a callgraph edge from the external node to this function.
      if (ExternalNode) ExternalNode->removeOneAbstractEdgeTo((*CG)[I]);
      Changed = true;
      ++NumFunctions;
      DEBUG(dbgs() << "Internalizing func " << I->getName() << "\n");
    }

  // Never internalize the llvm.used symbol.  It is used to implement
  // attribute((used)).
  // FIXME: Shouldn't this just filter on llvm.metadata section??
  ExternalNames.insert("llvm.used");
  ExternalNames.insert("llvm.compiler.used");

  // Never internalize anchors used by the machine module info, else the info
  // won't find them.  (see MachineModuleInfo.)
  ExternalNames.insert("llvm.global_ctors");
  ExternalNames.insert("llvm.global_dtors");
  ExternalNames.insert("llvm.global.annotations");

  // Never internalize symbols code-gen inserts.
  ExternalNames.insert("__stack_chk_guard");

  // Mark all global variables with initializers that are not in the api as
  // internal as well.
  // FIXME: maybe use private linkage?
  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I)
    if (!I->isDeclaration() && !I->hasLocalLinkage() &&
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !ExternalNames.count(I->getName())) {
      I->setLinkage(GlobalValue::InternalLinkage);
      Changed = true;
      ++NumGlobals;
      DEBUG(dbgs() << "Internalized gvar " << I->getName() << "\n");
    }

  // Mark all aliases that are not in the api as internal as well.
  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
       I != E; ++I)
    if (!I->isDeclaration() && !I->hasInternalLinkage() &&
        // Available externally is really just a "declaration with a body".
        !I->hasAvailableExternallyLinkage() &&
        !ExternalNames.count(I->getName())) {
      I->setLinkage(GlobalValue::InternalLinkage);
      Changed = true;
      ++NumAliases;
      DEBUG(dbgs() << "Internalized alias " << I->getName() << "\n");
    }

  return Changed;
}

/// Based on GetAllUndefinedSymbols() from LLVM3.2
///
/// GetAllUndefinedSymbols - calculates the set of undefined symbols that still
/// exist in an LLVM module. This is a bit tricky because there may be two
/// symbols with the same name but different LLVM types that will be resolved to
/// each other but aren't currently (thus we need to treat it as resolved).
///
/// Inputs:
///  M - The module in which to find undefined symbols.
///
/// Outputs:
///  UndefinedSymbols - A set of C++ strings containing the name of all
///                     undefined symbols.
///
static void
GetAllUndefinedSymbols(Module *M, std::set<std::string> &UndefinedSymbols) {
    static const std::string llvmIntrinsicPrefix="llvm.";
    std::set<std::string> DefinedSymbols;
    UndefinedSymbols.clear();
    KLEE_DEBUG_WITH_TYPE("klee_linker",
                         dbgs() << "*** Computing undefined symbols ***\n");

    for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
        if (I->hasName()) {
            if (I->isDeclaration())
                UndefinedSymbols.insert(I->getName());
            else if (!I->hasLocalLinkage()) {
#if LLVM_VERSION_CODE < LLVM_VERSION(3, 5)
                assert(!I->hasDLLImportLinkage() && "Found dllimported non-external symbol!");
#else
                assert(!I->hasDLLImportStorageClass() && "Found dllimported non-external symbol!");
#endif
                DefinedSymbols.insert(I->getName());
            }
        }

    for (Module::global_iterator I = M->global_begin(), E = M->global_end();
            I != E; ++I)
        if (I->hasName()) {
            if (I->isDeclaration())
                UndefinedSymbols.insert(I->getName());
            else if (!I->hasLocalLinkage()) {
#if LLVM_VERSION_CODE < LLVM_VERSION(3, 5)
                assert(!I->hasDLLImportLinkage() && "Found dllimported non-external symbol!");
#else
                assert(!I->hasDLLImportStorageClass() && "Found dllimported non-external symbol!");
#endif
                DefinedSymbols.insert(I->getName());
            }
        }

    for (Module::alias_iterator I = M->alias_begin(), E = M->alias_end();
            I != E; ++I)
        if (I->hasName())
            DefinedSymbols.insert(I->getName());


    // Prune out any defined symbols from the undefined symbols set
    // and other symbols we don't want to treat as an undefined symbol
    std::vector<std::string> SymbolsToRemove;
    for (std::set<std::string>::iterator I = UndefinedSymbols.begin();
            I != UndefinedSymbols.end(); ++I )
    {
        if (DefinedSymbols.count(*I))
        {
            SymbolsToRemove.push_back(*I);
            continue;
        }

        // Strip out llvm intrinsics
        if ( (I->size() >= llvmIntrinsicPrefix.size() ) &&
                (I->compare(0, llvmIntrinsicPrefix.size(), llvmIntrinsicPrefix) == 0) )
        {
            KLEE_DEBUG_WITH_TYPE("klee_linker", dbgs() << "LLVM intrinsic " << *I <<
                                 " has will be removed from undefined symbols"<< "\n");
            SymbolsToRemove.push_back(*I);
            continue;
        }

        // Symbol really is undefined
        KLEE_DEBUG_WITH_TYPE("klee_linker",
                             dbgs() << "Symbol " << *I << " is undefined.\n");
    }

    // Remove KLEE intrinsics from set of undefined symbols
    for (SpecialFunctionHandler::const_iterator sf = SpecialFunctionHandler::begin(),
            se = SpecialFunctionHandler::end(); sf != se; ++sf)
    {
        if (UndefinedSymbols.find(sf->name) == UndefinedSymbols.end())
            continue;

        SymbolsToRemove.push_back(sf->name);
        KLEE_DEBUG_WITH_TYPE("klee_linker",
                             dbgs() << "KLEE intrinsic " << sf->name <<
                             " has will be removed from undefined symbols"<< "\n");
    }

    // Now remove the symbols from undefined set.
    for (size_t i = 0, j = SymbolsToRemove.size(); i < j; ++i )
        UndefinedSymbols.erase(SymbolsToRemove[i]);
//.........这里部分代码省略.........