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

/* Change linkages of global values, in order to
 * improve alias analysis.
 */
bool DeadStoreEliminationPass::changeLinkageTypes(Module &M) {
  DEBUG(errs() << "Changing linkages to private...\n");
  for (Module::global_iterator git = M.global_begin(), gitE = M.global_end();
        git != gitE; ++git) {
    DEBUG(errs() << "  " << *git << "\n");
    if (!git->hasExternalLinkage() && !git->hasAppendingLinkage()) git->setLinkage(GlobalValue::PrivateLinkage);
  }
  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
    if (!F->isDeclaration()) {
     if (!F->hasExternalLinkage() && !F->hasAppendingLinkage()) F->setLinkage(GlobalValue::PrivateLinkage);
      DEBUG(errs() << "  " << F->getName() << "\n");
    }
  }
  DEBUG(errs() << "\n");
  return true;
}

/// doInitialization - Perform Module level initializations here.
/// One task that we do here is to sectionize all global variables.
/// The MemSelOptimizer pass depends on the sectionizing.
///
bool PIC16AsmPrinter::doInitialization(Module &M) {
  bool Result = AsmPrinter::doInitialization(M);

  // Every asmbly contains these std headers. 
  O << "\n#include p16f1xxx.inc";
  O << "\n#include stdmacros.inc";

  // Set the section names for all globals.
  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E; ++I) {

    // Record External Var Decls.
    if (I->isDeclaration()) {
      ExternalVarDecls.push_back(I);
      continue;
    }

    // Record Exteranl Var Defs.
    if (I->hasExternalLinkage() || I->hasCommonLinkage()) {
      ExternalVarDefs.push_back(I);
    }

    // Sectionify actual data.
    if (!I->hasAvailableExternallyLinkage()) {
      const MCSection *S = getObjFileLowering().SectionForGlobal(I, Mang, TM);
      
      I->setSection(((const PIC16Section *)S)->getName());
    }
  }

  DbgInfo.BeginModule(M);
  EmitFunctionDecls(M);
  EmitUndefinedVars(M);
  EmitDefinedVars(M);
  EmitIData(M);
  EmitUData(M);
  EmitRomData(M);
  EmitSharedUdata(M);
  EmitUserSections(M);
  return Result;
}

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

  auto &DL = M.getDataLayout();
  DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
                                                        BSSGlobals;
  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 or external globals only
    if (I->isDeclaration() || I->isThreadLocal() || I->hasSection())
      continue;

    if (!(EnableGlobalMergeOnExternal && I->hasExternalLinkage()) &&
        !I->hasInternalLinkage())
      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, *TM).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;
}