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

/// computeTypeMapping - Loop over all of the linked values to compute type
/// mappings.  For example, if we link "extern Foo *x" and "Foo *x = NULL", then
/// we have two struct types 'Foo' but one got renamed when the module was
/// loaded into the same LLVMContext.
void ModuleLinker::computeTypeMapping() {
  // Incorporate globals.
  for (Module::global_iterator I = SrcM->global_begin(),
       E = SrcM->global_end(); I != E; ++I) {
    GlobalValue *DGV = getLinkedToGlobal(I);
    if (DGV == 0) continue;
    
    if (!DGV->hasAppendingLinkage() || !I->hasAppendingLinkage()) {
      TypeMap.addTypeMapping(DGV->getType(), I->getType());
      continue;      
    }
    
    // Unify the element type of appending arrays.
    ArrayType *DAT = cast<ArrayType>(DGV->getType()->getElementType());
    ArrayType *SAT = cast<ArrayType>(I->getType()->getElementType());
    TypeMap.addTypeMapping(DAT->getElementType(), SAT->getElementType());
  }
  
  // Incorporate functions.
  for (Module::iterator I = SrcM->begin(), E = SrcM->end(); I != E; ++I) {
    if (GlobalValue *DGV = getLinkedToGlobal(I))
      TypeMap.addTypeMapping(DGV->getType(), I->getType());
  }

  // Incorporate types by name, scanning all the types in the source module.
  // At this point, the destination module may have a type "%foo = { i32 }" for
  // example.  When the source module got loaded into the same LLVMContext, if
  // it had the same type, it would have been renamed to "%foo.42 = { i32 }".
  // Though it isn't required for correctness, attempt to link these up to clean
  // up the IR.
  std::vector<StructType*> SrcStructTypes;
  SrcM->findUsedStructTypes(SrcStructTypes);
  
  SmallPtrSet<StructType*, 32> SrcStructTypesSet(SrcStructTypes.begin(),
                                                 SrcStructTypes.end());
  
  for (unsigned i = 0, e = SrcStructTypes.size(); i != e; ++i) {
    StructType *ST = SrcStructTypes[i];
    if (!ST->hasName()) continue;
    
    // Check to see if there is a dot in the name followed by a digit.
    size_t DotPos = ST->getName().rfind('.');
    if (DotPos == 0 || DotPos == StringRef::npos ||
        ST->getName().back() == '.' || !isdigit(ST->getName()[DotPos+1]))
      continue;
    
    // Check to see if the destination module has a struct with the prefix name.
    if (StructType *DST = DstM->getTypeByName(ST->getName().substr(0, DotPos)))
      // Don't use it if this actually came from the source module.  They're in
      // the same LLVMContext after all.
      if (!SrcStructTypesSet.count(DST))
        TypeMap.addTypeMapping(DST, ST);
  }

  // Don't bother incorporating aliases, they aren't generally typed well.
  
  // Now that we have discovered all of the type equivalences, get a body for
  // any 'opaque' types in the dest module that are now resolved. 
  TypeMap.linkDefinedTypeBodies();
}

/* 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;
}