C++ StructType::getContext方法代码示例

// RemoveDeadStuffFromFunction - Remove any arguments and return values from F
// that are not in LiveValues. Transform the function and all of the callees of
// the function to not have these arguments and return values.
//
bool DAE::RemoveDeadStuffFromFunction(Function *F) {
  // Don't modify fully live functions
  if (LiveFunctions.count(F))
    return false;

  // Start by computing a new prototype for the function, which is the same as
  // the old function, but has fewer arguments and a different return type.
  FunctionType *FTy = F->getFunctionType();
  std::vector<Type*> Params;

  // Set up to build a new list of parameter attributes.
  SmallVector<AttributeWithIndex, 8> AttributesVec;
  const AttributeSet &PAL = F->getAttributes();

  // Find out the new return value.
  Type *RetTy = FTy->getReturnType();
  Type *NRetTy = NULL;
  unsigned RetCount = NumRetVals(F);

  // -1 means unused, other numbers are the new index
  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
  std::vector<Type*> RetTypes;
  if (RetTy->isVoidTy()) {
    NRetTy = RetTy;
  } else {
    StructType *STy = dyn_cast<StructType>(RetTy);
    if (STy)
      // Look at each of the original return values individually.
      for (unsigned i = 0; i != RetCount; ++i) {
        RetOrArg Ret = CreateRet(F, i);
        if (LiveValues.erase(Ret)) {
          RetTypes.push_back(STy->getElementType(i));
          NewRetIdxs[i] = RetTypes.size() - 1;
        } else {
          ++NumRetValsEliminated;
          DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
                << F->getName() << "\n");
        }
      }
    else
      // We used to return a single value.
      if (LiveValues.erase(CreateRet(F, 0))) {
        RetTypes.push_back(RetTy);
        NewRetIdxs[0] = 0;
      } else {
        DEBUG(dbgs() << "DAE - Removing return value from " << F->getName()
              << "\n");
        ++NumRetValsEliminated;
      }
    if (RetTypes.size() > 1)
      // More than one return type? Return a struct with them. Also, if we used
      // to return a struct and didn't change the number of return values,
      // return a struct again. This prevents changing {something} into
      // something and {} into void.
      // Make the new struct packed if we used to return a packed struct
      // already.
      NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
    else if (RetTypes.size() == 1)
      // One return type? Just a simple value then, but only if we didn't use to
      // return a struct with that simple value before.
      NRetTy = RetTypes.front();
    else if (RetTypes.size() == 0)
      // No return types? Make it void, but only if we didn't use to return {}.
      NRetTy = Type::getVoidTy(F->getContext());
  }

  assert(NRetTy && "No new return type found?");

  // The existing function return attributes.
  AttributeSet RAttrs = PAL.getRetAttributes();

  // Remove any incompatible attributes, but only if we removed all return
  // values. Otherwise, ensure that we don't have any conflicting attributes
  // here. Currently, this should not be possible, but special handling might be
  // required when new return value attributes are added.
  if (NRetTy->isVoidTy())
    RAttrs =
      AttributeSet::get(NRetTy->getContext(), AttributeSet::ReturnIndex,
                        AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
                    removeAttributes(AttributeFuncs::typeIncompatible(NRetTy)));
  else
    assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
             hasAttributes(AttributeFuncs::typeIncompatible(NRetTy)) &&
           "Return attributes no longer compatible?");

  if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
    AttributesVec.push_back(AttributeWithIndex::get(NRetTy->getContext(),
                                                    AttributeSet::ReturnIndex,
                                                    RAttrs));

  // Remember which arguments are still alive.
  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
  // Construct the new parameter list from non-dead arguments. Also construct
  // a new set of parameter attributes to correspond. Skip the first parameter
  // attribute, since that belongs to the return value.
  unsigned i = 0;
//.........这里部分代码省略.........

/// getImpl - This is the recursive version of get().
Type *TypeMapTy::getImpl(Type *Ty) {
  // If we already have an entry for this type, return it.
  Type **Entry = &MappedTypes[Ty];
  if (*Entry) return *Entry;
  
  // If this is not a named struct type, then just map all of the elements and
  // then rebuild the type from inside out.
  if (!isa<StructType>(Ty) || cast<StructType>(Ty)->isLiteral()) {
    // If there are no element types to map, then the type is itself.  This is
    // true for the anonymous {} struct, things like 'float', integers, etc.
    if (Ty->getNumContainedTypes() == 0)
      return *Entry = Ty;
    
    // Remap all of the elements, keeping track of whether any of them change.
    bool AnyChange = false;
    SmallVector<Type*, 4> ElementTypes;
    ElementTypes.resize(Ty->getNumContainedTypes());
    for (unsigned i = 0, e = Ty->getNumContainedTypes(); i != e; ++i) {
      ElementTypes[i] = getImpl(Ty->getContainedType(i));
      AnyChange |= ElementTypes[i] != Ty->getContainedType(i);
    }
    
    // If we found our type while recursively processing stuff, just use it.
    Entry = &MappedTypes[Ty];
    if (*Entry) return *Entry;
    
    // If all of the element types mapped directly over, then the type is usable
    // as-is.
    if (!AnyChange)
      return *Entry = Ty;
    
    // Otherwise, rebuild a modified type.
    switch (Ty->getTypeID()) {
    default: llvm_unreachable("unknown derived type to remap");
    case Type::ArrayTyID:
      return *Entry = ArrayType::get(ElementTypes[0],
                                     cast<ArrayType>(Ty)->getNumElements());
    case Type::VectorTyID: 
      return *Entry = VectorType::get(ElementTypes[0],
                                      cast<VectorType>(Ty)->getNumElements());
    case Type::PointerTyID:
      return *Entry = PointerType::get(ElementTypes[0],
                                      cast<PointerType>(Ty)->getAddressSpace());
    case Type::FunctionTyID:
      return *Entry = FunctionType::get(ElementTypes[0],
                                        makeArrayRef(ElementTypes).slice(1),
                                        cast<FunctionType>(Ty)->isVarArg());
    case Type::StructTyID:
      // Note that this is only reached for anonymous structs.
      return *Entry = StructType::get(Ty->getContext(), ElementTypes,
                                      cast<StructType>(Ty)->isPacked());
    }
  }

  // Otherwise, this is an unmapped named struct.  If the struct can be directly
  // mapped over, just use it as-is.  This happens in a case when the linked-in
  // module has something like:
  //   %T = type {%T*, i32}
  //   @GV = global %T* null
  // where T does not exist at all in the destination module.
  //
  // The other case we watch for is when the type is not in the destination
  // module, but that it has to be rebuilt because it refers to something that
  // is already mapped.  For example, if the destination module has:
  //  %A = type { i32 }
  // and the source module has something like
  //  %A' = type { i32 }
  //  %B = type { %A'* }
  //  @GV = global %B* null
  // then we want to create a new type: "%B = type { %A*}" and have it take the
  // pristine "%B" name from the source module.
  //
  // To determine which case this is, we have to recursively walk the type graph
  // speculating that we'll be able to reuse it unmodified.  Only if this is
  // safe would we map the entire thing over.  Because this is an optimization,
  // and is not required for the prettiness of the linked module, we just skip
  // it and always rebuild a type here.
  StructType *STy = cast<StructType>(Ty);
  
  // If the type is opaque, we can just use it directly.
  if (STy->isOpaque())
    return *Entry = STy;
  
  // Otherwise we create a new type and resolve its body later.  This will be
  // resolved by the top level of get().
  SrcDefinitionsToResolve.push_back(STy);
  StructType *DTy = StructType::create(STy->getContext());
  DstResolvedOpaqueTypes.insert(DTy);
  return *Entry = DTy;
}