text: //===--- CodeGenTypes.cpp - Type translation for LLVM CodeGen -------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This is the code that handles AST -> LLVM type lowering.
  //
  //===----------------------------------------------------------------------===//
  
  #include "CodeGenTypes.h"
  #include "CGCXXABI.h"
  #include "CGCall.h"
  #include "CGOpenCLRuntime.h"
  #include "CGRecordLayout.h"
  #include "TargetInfo.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/DeclObjC.h"
  #include "clang/AST/Expr.h"
  #include "clang/AST/RecordLayout.h"
  #include "clang/CodeGen/CGFunctionInfo.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Module.h"
  using namespace clang;
  using namespace CodeGen;
  
  CodeGenTypes::CodeGenTypes(CodeGenModule &cgm)
    : CGM(cgm), Context(cgm.getContext()), TheModule(cgm.getModule()),
      Target(cgm.getTarget()), TheCXXABI(cgm.getCXXABI()),
      TheABIInfo(cgm.getTargetCodeGenInfo().getABIInfo()) {
    SkippedLayout = false;
  }
  
  CodeGenTypes::~CodeGenTypes() {
    llvm::DeleteContainerSeconds(CGRecordLayouts);
  
    for (llvm::FoldingSet<CGFunctionInfo>::iterator
         I = FunctionInfos.begin(), E = FunctionInfos.end(); I != E; )
      delete &*I++;
  }
  
  const CodeGenOptions &CodeGenTypes::getCodeGenOpts() const {
    return CGM.getCodeGenOpts();
  }
  
  void CodeGenTypes::addRecordTypeName(const RecordDecl *RD,
                                       llvm::StructType *Ty,
                                       StringRef suffix) {
    SmallString<256> TypeName;
    llvm::raw_svector_ostream OS(TypeName);
    OS << RD->getKindName() << '.';
    
    // Name the codegen type after the typedef name
    // if there is no tag type name available
    if (RD->getIdentifier()) {
      // FIXME: We should not have to check for a null decl context here.
      // Right now we do it because the implicit Obj-C decls don't have one.
      if (RD->getDeclContext())
        RD->printQualifiedName(OS);
      else
        RD->printName(OS);
    } else if (const TypedefNameDecl *TDD = RD->getTypedefNameForAnonDecl()) {
      // FIXME: We should not have to check for a null decl context here.
      // Right now we do it because the implicit Obj-C decls don't have one.
      if (TDD->getDeclContext())
        TDD->printQualifiedName(OS);
      else
        TDD->printName(OS);
    } else
      OS << "anon";
  
    if (!suffix.empty())
      OS << suffix;
  
    Ty->setName(OS.str());
  }
  
  /// ConvertTypeForMem - Convert type T into a llvm::Type.  This differs from
  /// ConvertType in that it is used to convert to the memory representation for
  /// a type.  For example, the scalar representation for _Bool is i1, but the
  /// memory representation is usually i8 or i32, depending on the target.
  llvm::Type *CodeGenTypes::ConvertTypeForMem(QualType T) {
    llvm::Type *R = ConvertType(T);
  
    // If this is a non-bool type, don't map it.
    if (!R->isIntegerTy(1))
      return R;
  
    // Otherwise, return an integer of the target-specified size.
    return llvm::IntegerType::get(getLLVMContext(),
                                  (unsigned)Context.getTypeSize(T));
  }
  
  
  /// isRecordLayoutComplete - Return true if the specified type is already
  /// completely laid out.
  bool CodeGenTypes::isRecordLayoutComplete(const Type *Ty) const {
    llvm::DenseMap<const Type*, llvm::StructType *>::const_iterator I = 
    RecordDeclTypes.find(Ty);
    return I != RecordDeclTypes.end() && !I->second->isOpaque();
  }
  
  static bool
  isSafeToConvert(QualType T, CodeGenTypes &CGT,
                  llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked);
  
  
  /// isSafeToConvert - Return true if it is safe to convert the specified record
  /// decl to IR and lay it out, false if doing so would cause us to get into a
  /// recursive compilation mess.
  static bool 
  isSafeToConvert(const RecordDecl *RD, CodeGenTypes &CGT,
                  llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked) {
    // If we have already checked this type (maybe the same type is used by-value
    // multiple times in multiple structure fields, don't check again.
    if (!AlreadyChecked.insert(RD).second)
      return true;
  
    const Type *Key = CGT.getContext().getTagDeclType(RD).getTypePtr();
    
    // If this type is already laid out, converting it is a noop.
    if (CGT.isRecordLayoutComplete(Key)) return true;
    
    // If this type is currently being laid out, we can't recursively compile it.
    if (CGT.isRecordBeingLaidOut(Key))
      return false;
    
    // If this type would require laying out bases that are currently being laid
    // out, don't do it.  This includes virtual base classes which get laid out
    // when a class is translated, even though they aren't embedded by-value into
    // the class.
    if (const CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(RD)) {
      for (const auto &I : CRD->bases())
        if (!isSafeToConvert(I.getType()->getAs<RecordType>()->getDecl(),
                             CGT, AlreadyChecked))
          return false;
    }
    
    // If this type would require laying out members that are currently being laid
    // out, don't do it.
    for (const auto *I : RD->fields())
      if (!isSafeToConvert(I->getType(), CGT, AlreadyChecked))
        return false;
    
    // If there are no problems, lets do it.
    return true;
  }
  
  /// isSafeToConvert - Return true if it is safe to convert this field type,
  /// which requires the structure elements contained by-value to all be
  /// recursively safe to convert.
  static bool
  isSafeToConvert(QualType T, CodeGenTypes &CGT,
                  llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked) {
    // Strip off atomic type sugar.
    if (const auto *AT = T->getAs<AtomicType>())
      T = AT->getValueType();
  
    // If this is a record, check it.
    if (const auto *RT = T->getAs<RecordType>())
      return isSafeToConvert(RT->getDecl(), CGT, AlreadyChecked);
  
    // If this is an array, check the elements, which are embedded inline.
    if (const auto *AT = CGT.getContext().getAsArrayType(T))
      return isSafeToConvert(AT->getElementType(), CGT, AlreadyChecked);
  
    // Otherwise, there is no concern about transforming this.  We only care about
    // things that are contained by-value in a structure that can have another 
    // structure as a member.
    return true;
  }
  
  
  /// isSafeToConvert - Return true if it is safe to convert the specified record
  /// decl to IR and lay it out, false if doing so would cause us to get into a
  /// recursive compilation mess.
  static bool isSafeToConvert(const RecordDecl *RD, CodeGenTypes &CGT) {
    // If no structs are being laid out, we can certainly do this one.
    if (CGT.noRecordsBeingLaidOut()) return true;
    
    llvm::SmallPtrSet<const RecordDecl*, 16> AlreadyChecked;
    return isSafeToConvert(RD, CGT, AlreadyChecked);
  }
  
  /// isFuncParamTypeConvertible - Return true if the specified type in a
  /// function parameter or result position can be converted to an IR type at this
  /// point.  This boils down to being whether it is complete, as well as whether
  /// we've temporarily deferred expanding the type because we're in a recursive
  /// context.
  bool CodeGenTypes::isFuncParamTypeConvertible(QualType Ty) {
    // Some ABIs cannot have their member pointers represented in IR unless
    // certain circumstances have been reached.
    if (const auto *MPT = Ty->getAs<MemberPointerType>())
      return getCXXABI().isMemberPointerConvertible(MPT);
  
    // If this isn't a tagged type, we can convert it!
    const TagType *TT = Ty->getAs<TagType>();
    if (!TT) return true;
  
    // Incomplete types cannot be converted.
    if (TT->isIncompleteType())
      return false;
  
    // If this is an enum, then it is always safe to convert.
    const RecordType *RT = dyn_cast<RecordType>(TT);
    if (!RT) return true;
  
    // Otherwise, we have to be careful.  If it is a struct that we're in the
    // process of expanding, then we can't convert the function type.  That's ok
    // though because we must be in a pointer context under the struct, so we can
    // just convert it to a dummy type.
    //
    // We decide this by checking whether ConvertRecordDeclType returns us an
    // opaque type for a struct that we know is defined.
    return isSafeToConvert(RT->getDecl(), *this);
  }
  
  
  /// Code to verify a given function type is complete, i.e. the return type
  /// and all of the parameter types are complete.  Also check to see if we are in
  /// a RS_StructPointer context, and if so whether any struct types have been
  /// pended.  If so, we don't want to ask the ABI lowering code to handle a type
  /// that cannot be converted to an IR type.
  bool CodeGenTypes::isFuncTypeConvertible(const FunctionType *FT) {
    if (!isFuncParamTypeConvertible(FT->getReturnType()))
      return false;
    
    if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FT))
      for (unsigned i = 0, e = FPT->getNumParams(); i != e; i++)
        if (!isFuncParamTypeConvertible(FPT->getParamType(i)))
          return false;
  
    return true;
  }
  
  /// UpdateCompletedType - When we find the full definition for a TagDecl,
  /// replace the 'opaque' type we previously made for it if applicable.
  void CodeGenTypes::UpdateCompletedType(const TagDecl *TD) {
    // If this is an enum being completed, then we flush all non-struct types from
    // the cache.  This allows function types and other things that may be derived
    // from the enum to be recomputed.
    if (const EnumDecl *ED = dyn_cast<EnumDecl>(TD)) {
      // Only flush the cache if we've actually already converted this type.
      if (TypeCache.count(ED->getTypeForDecl())) {
        // Okay, we formed some types based on this.  We speculated that the enum
        // would be lowered to i32, so we only need to flush the cache if this
        // didn't happen.
        if (!ConvertType(ED->getIntegerType())->isIntegerTy(32))
          TypeCache.clear();
      }
      // If necessary, provide the full definition of a type only used with a
      // declaration so far.
      if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
        DI->completeType(ED);
      return;
    }
    
    // If we completed a RecordDecl that we previously used and converted to an
    // anonymous type, then go ahead and complete it now.
    const RecordDecl *RD = cast<RecordDecl>(TD);
    if (RD->isDependentType()) return;
  
    // Only complete it if we converted it already.  If we haven't converted it
    // yet, we'll just do it lazily.
    if (RecordDeclTypes.count(Context.getTagDeclType(RD).getTypePtr()))
      ConvertRecordDeclType(RD);
  
    // If necessary, provide the full definition of a type only used with a
    // declaration so far.
    if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
      DI->completeType(RD);
  }
  
  void CodeGenTypes::RefreshTypeCacheForClass(const CXXRecordDecl *RD) {
    QualType T = Context.getRecordType(RD);
    T = Context.getCanonicalType(T);
  
    const Type *Ty = T.getTypePtr();
    if (RecordsWithOpaqueMemberPointers.count(Ty)) {
      TypeCache.clear();
      RecordsWithOpaqueMemberPointers.clear();
    }
  }
  
  static llvm::Type *getTypeForFormat(llvm::LLVMContext &VMContext,
                                      const llvm::fltSemantics &format,
                                      bool UseNativeHalf = false) {
    if (&format == &llvm::APFloat::IEEEhalf()) {
      if (UseNativeHalf)
        return llvm::Type::getHalfTy(VMContext);
      else
        return llvm::Type::getInt16Ty(VMContext);
    }
    if (&format == &llvm::APFloat::IEEEsingle())
      return llvm::Type::getFloatTy(VMContext);
    if (&format == &llvm::APFloat::IEEEdouble())
      return llvm::Type::getDoubleTy(VMContext);
    if (&format == &llvm::APFloat::IEEEquad())
      return llvm::Type::getFP128Ty(VMContext);
    if (&format == &llvm::APFloat::PPCDoubleDouble())
      return llvm::Type::getPPC_FP128Ty(VMContext);
    if (&format == &llvm::APFloat::x87DoubleExtended())
      return llvm::Type::getX86_FP80Ty(VMContext);
    llvm_unreachable("Unknown float format!");
  }
  
  llvm::Type *CodeGenTypes::ConvertFunctionType(QualType QFT,
                                                const FunctionDecl *FD) {
    assert(QFT.isCanonical());
    const Type *Ty = QFT.getTypePtr();
    const FunctionType *FT = cast<FunctionType>(QFT.getTypePtr());
    // First, check whether we can build the full function type.  If the
    // function type depends on an incomplete type (e.g. a struct or enum), we
    // cannot lower the function type.
    if (!isFuncTypeConvertible(FT)) {
      // This function's type depends on an incomplete tag type.
  
      // Force conversion of all the relevant record types, to make sure
      // we re-convert the FunctionType when appropriate.
      if (const RecordType *RT = FT->getReturnType()->getAs<RecordType>())
        ConvertRecordDeclType(RT->getDecl());
      if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FT))
        for (unsigned i = 0, e = FPT->getNumParams(); i != e; i++)
          if (const RecordType *RT = FPT->getParamType(i)->getAs<RecordType>())
            ConvertRecordDeclType(RT->getDecl());
  
      SkippedLayout = true;
  
      // Return a placeholder type.
      return llvm::StructType::get(getLLVMContext());
    }
  
    // While we're converting the parameter types for a function, we don't want
    // to recursively convert any pointed-to structs.  Converting directly-used
    // structs is ok though.
    if (!RecordsBeingLaidOut.insert(Ty).second) {
      SkippedLayout = true;
      return llvm::StructType::get(getLLVMContext());
    }
  
    // The function type can be built; call the appropriate routines to
    // build it.
    const CGFunctionInfo *FI;
    if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FT)) {
      FI = &arrangeFreeFunctionType(
          CanQual<FunctionProtoType>::CreateUnsafe(QualType(FPT, 0)), FD);
    } else {
      const FunctionNoProtoType *FNPT = cast<FunctionNoProtoType>(FT);
      FI = &arrangeFreeFunctionType(
          CanQual<FunctionNoProtoType>::CreateUnsafe(QualType(FNPT, 0)));
    }
  
    llvm::Type *ResultType = nullptr;
    // If there is something higher level prodding our CGFunctionInfo, then
    // don't recurse into it again.
    if (FunctionsBeingProcessed.count(FI)) {
  
      ResultType = llvm::StructType::get(getLLVMContext());
      SkippedLayout = true;
    } else {
  
      // Otherwise, we're good to go, go ahead and convert it.
      ResultType = GetFunctionType(*FI);
    }
  
    RecordsBeingLaidOut.erase(Ty);
  
    if (SkippedLayout)
      TypeCache.clear();
  
    if (RecordsBeingLaidOut.empty())
      while (!DeferredRecords.empty())
        ConvertRecordDeclType(DeferredRecords.pop_back_val());
    return ResultType;
  }
  
  /// ConvertType - Convert the specified type to its LLVM form.
  llvm::Type *CodeGenTypes::ConvertType(QualType T) {
    T = Context.getCanonicalType(T);
  
    const Type *Ty = T.getTypePtr();
  
    // RecordTypes are cached and processed specially.
    if (const RecordType *RT = dyn_cast<RecordType>(Ty))
      return ConvertRecordDeclType(RT->getDecl());
    
    // See if type is already cached.
    llvm::DenseMap<const Type *, llvm::Type *>::iterator TCI = TypeCache.find(Ty);
    // If type is found in map then use it. Otherwise, convert type T.
    if (TCI != TypeCache.end())
      return TCI->second;
  
    // If we don't have it in the cache, convert it now.
    llvm::Type *ResultType = nullptr;
    switch (Ty->getTypeClass()) {
    case Type::Record: // Handled above.
  #define TYPE(Class, Base)
  #define ABSTRACT_TYPE(Class, Base)
  #define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
  #define DEPENDENT_TYPE(Class, Base) case Type::Class:
  #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
  #include "clang/AST/TypeNodes.def"
      llvm_unreachable("Non-canonical or dependent types aren't possible.");
  
    case Type::Builtin: {
      switch (cast<BuiltinType>(Ty)->getKind()) {
      case BuiltinType::Void:
      case BuiltinType::ObjCId:
      case BuiltinType::ObjCClass:
      case BuiltinType::ObjCSel:
        // LLVM void type can only be used as the result of a function call.  Just
        // map to the same as char.
        ResultType = llvm::Type::getInt8Ty(getLLVMContext());
        break;
  
      case BuiltinType::Bool:
        // Note that we always return bool as i1 for use as a scalar type.
        ResultType = llvm::Type::getInt1Ty(getLLVMContext());
        break;
  
      case BuiltinType::Char_S:
      case BuiltinType::Char_U:
      case BuiltinType::SChar:
      case BuiltinType::UChar:
      case BuiltinType::Short:
      case BuiltinType::UShort:
      case BuiltinType::Int:
      case BuiltinType::UInt:
      case BuiltinType::Long:
      case BuiltinType::ULong:
      case BuiltinType::LongLong:
      case BuiltinType::ULongLong:
      case BuiltinType::WChar_S:
      case BuiltinType::WChar_U:
      case BuiltinType::Char16:
      case BuiltinType::Char32:
        ResultType = llvm::IntegerType::get(getLLVMContext(),
                                   static_cast<unsigned>(Context.getTypeSize(T)));
        break;
  
      case BuiltinType::Half:
        // Half FP can either be storage-only (lowered to i16) or native.
        ResultType =
            getTypeForFormat(getLLVMContext(), Context.getFloatTypeSemantics(T),
                             Context.getLangOpts().NativeHalfType ||
                                 Context.getLangOpts().HalfArgsAndReturns);
        break;
      case BuiltinType::Float:
      case BuiltinType::Double:
      case BuiltinType::LongDouble:
      case BuiltinType::Float128:
        ResultType = getTypeForFormat(getLLVMContext(),
                                      Context.getFloatTypeSemantics(T),
                                      /* UseNativeHalf = */ false);
        break;
  
      case BuiltinType::NullPtr:
        // Model std::nullptr_t as i8*
        ResultType = llvm::Type::getInt8PtrTy(getLLVMContext());
        break;
          
      case BuiltinType::UInt128:
      case BuiltinType::Int128:
        ResultType = llvm::IntegerType::get(getLLVMContext(), 128);
        break;
  
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
      case BuiltinType::Id:
  #include "clang/Basic/OpenCLImageTypes.def"
      case BuiltinType::OCLSampler:
      case BuiltinType::OCLEvent:
      case BuiltinType::OCLClkEvent:
      case BuiltinType::OCLQueue:
      case BuiltinType::OCLReserveID:
        ResultType = CGM.getOpenCLRuntime().convertOpenCLSpecificType(Ty);
        break;
      
      case BuiltinType::Dependent:
  #define BUILTIN_TYPE(Id, SingletonId)
  #define PLACEHOLDER_TYPE(Id, SingletonId) \
      case BuiltinType::Id:
  #include "clang/AST/BuiltinTypes.def"
        llvm_unreachable("Unexpected placeholder builtin type!");
      }
      break;
    }
    case Type::Auto:
    case Type::DeducedTemplateSpecialization:
      llvm_unreachable("Unexpected undeduced type!");
    case Type::Complex: {
      llvm::Type *EltTy = ConvertType(cast<ComplexType>(Ty)->getElementType());
      ResultType = llvm::StructType::get(EltTy, EltTy);
      break;
    }
    case Type::LValueReference:
    case Type::RValueReference: {
      const ReferenceType *RTy = cast<ReferenceType>(Ty);
      QualType ETy = RTy->getPointeeType();
      llvm::Type *PointeeType = ConvertTypeForMem(ETy);
      unsigned AS = Context.getTargetAddressSpace(ETy);
      ResultType = llvm::PointerType::get(PointeeType, AS);
      break;
    }
    case Type::Pointer: {
      const PointerType *PTy = cast<PointerType>(Ty);
      QualType ETy = PTy->getPointeeType();
      llvm::Type *PointeeType = ConvertTypeForMem(ETy);
      if (PointeeType->isVoidTy())
        PointeeType = llvm::Type::getInt8Ty(getLLVMContext());
      unsigned AS = Context.getTargetAddressSpace(ETy);
      ResultType = llvm::PointerType::get(PointeeType, AS);
      break;
    }
  
    case Type::VariableArray: {
      const VariableArrayType *A = cast<VariableArrayType>(Ty);
      assert(A->getIndexTypeCVRQualifiers() == 0 &&
             "FIXME: We only handle trivial array types so far!");
      // VLAs resolve to the innermost element type; this matches
      // the return of alloca, and there isn't any obviously better choice.
      ResultType = ConvertTypeForMem(A->getElementType());
      break;
    }
    case Type::IncompleteArray: {
      const IncompleteArrayType *A = cast<IncompleteArrayType>(Ty);
      assert(A->getIndexTypeCVRQualifiers() == 0 &&
             "FIXME: We only handle trivial array types so far!");
      // int X[] -> [0 x int], unless the element type is not sized.  If it is
      // unsized (e.g. an incomplete struct) just use [0 x i8].
      ResultType = ConvertTypeForMem(A->getElementType());
      if (!ResultType->isSized()) {
        SkippedLayout = true;
        ResultType = llvm::Type::getInt8Ty(getLLVMContext());
      }
      ResultType = llvm::ArrayType::get(ResultType, 0);
      break;
    }
    case Type::ConstantArray: {
      const ConstantArrayType *A = cast<ConstantArrayType>(Ty);
      llvm::Type *EltTy = ConvertTypeForMem(A->getElementType());
      
      // Lower arrays of undefined struct type to arrays of i8 just to have a 
      // concrete type.
      if (!EltTy->isSized()) {
        SkippedLayout = true;
        EltTy = llvm::Type::getInt8Ty(getLLVMContext());
      }
  
      ResultType = llvm::ArrayType::get(EltTy, A->getSize().getZExtValue());
      break;
    }
    case Type::ExtVector:
    case Type::Vector: {
      const VectorType *VT = cast<VectorType>(Ty);
      ResultType = llvm::VectorType::get(ConvertType(VT->getElementType()),
                                         VT->getNumElements());
      break;
    }
    case Type::FunctionNoProto:
    case Type::FunctionProto:
      ResultType = ConvertFunctionType(T);
      break;
    case Type::ObjCObject:
      ResultType = ConvertType(cast<ObjCObjectType>(Ty)->getBaseType());
      break;
  
    case Type::ObjCInterface: {
      // Objective-C interfaces are always opaque (outside of the
      // runtime, which can do whatever it likes); we never refine
      // these.
      llvm::Type *&T = InterfaceTypes[cast<ObjCInterfaceType>(Ty)];
      if (!T)
        T = llvm::StructType::create(getLLVMContext());
      ResultType = T;
      break;
    }
  
    case Type::ObjCObjectPointer: {
      // Protocol qualifications do not influence the LLVM type, we just return a
      // pointer to the underlying interface type. We don't need to worry about
      // recursive conversion.
      llvm::Type *T =
        ConvertTypeForMem(cast<ObjCObjectPointerType>(Ty)->getPointeeType());
      ResultType = T->getPointerTo();
      break;
    }
  
    case Type::Enum: {
      const EnumDecl *ED = cast<EnumType>(Ty)->getDecl();
      if (ED->isCompleteDefinition() || ED->isFixed())
        return ConvertType(ED->getIntegerType());
      // Return a placeholder 'i32' type.  This can be changed later when the
      // type is defined (see UpdateCompletedType), but is likely to be the
      // "right" answer.
      ResultType = llvm::Type::getInt32Ty(getLLVMContext());
      break;
    }
  
    case Type::BlockPointer: {
      const QualType FTy = cast<BlockPointerType>(Ty)->getPointeeType();
      llvm::Type *PointeeType = ConvertTypeForMem(FTy);
      unsigned AS = Context.getTargetAddressSpace(FTy);
      ResultType = llvm::PointerType::get(PointeeType, AS);
      break;
    }
  
    case Type::MemberPointer: {
      auto *MPTy = cast<MemberPointerType>(Ty);
      if (!getCXXABI().isMemberPointerConvertible(MPTy)) {
        RecordsWithOpaqueMemberPointers.insert(MPTy->getClass());
        ResultType = llvm::StructType::create(getLLVMContext());
      } else {
        ResultType = getCXXABI().ConvertMemberPointerType(MPTy);
      }
      break;
    }
  
    case Type::Atomic: {
      QualType valueType = cast<AtomicType>(Ty)->getValueType();
      ResultType = ConvertTypeForMem(valueType);
  
      // Pad out to the inflated size if necessary.
      uint64_t valueSize = Context.getTypeSize(valueType);
      uint64_t atomicSize = Context.getTypeSize(Ty);
      if (valueSize != atomicSize) {
        assert(valueSize < atomicSize);
        llvm::Type *elts[] = {
          ResultType,
          llvm::ArrayType::get(CGM.Int8Ty, (atomicSize - valueSize) / 8)
        };
        ResultType = llvm::StructType::get(getLLVMContext(),
                                           llvm::makeArrayRef(elts));
      }
      break;
    }
    case Type::Pipe: {
      ResultType = CGM.getOpenCLRuntime().getPipeType();
      break;
    }
    }
    
    assert(ResultType && "Didn't convert a type?");
    
    TypeCache[Ty] = ResultType;
    return ResultType;
  }
  
  bool CodeGenModule::isPaddedAtomicType(QualType type) {
    return isPaddedAtomicType(type->castAs<AtomicType>());
  }
  
  bool CodeGenModule::isPaddedAtomicType(const AtomicType *type) {
    return Context.getTypeSize(type) != Context.getTypeSize(type->getValueType());
  }
  
  /// ConvertRecordDeclType - Lay out a tagged decl type like struct or union.
  llvm::StructType *CodeGenTypes::ConvertRecordDeclType(const RecordDecl *RD) {
    // TagDecl's are not necessarily unique, instead use the (clang)
    // type connected to the decl.
    const Type *Key = Context.getTagDeclType(RD).getTypePtr();
  
    llvm::StructType *&Entry = RecordDeclTypes[Key];
  
    // If we don't have a StructType at all yet, create the forward declaration.
    if (!Entry) {
      Entry = llvm::StructType::create(getLLVMContext());
      addRecordTypeName(RD, Entry, "");
    }
    llvm::StructType *Ty = Entry;
  
    // If this is still a forward declaration, or the LLVM type is already
    // complete, there's nothing more to do.
    RD = RD->getDefinition();
    if (!RD || !RD->isCompleteDefinition() || !Ty->isOpaque())
      return Ty;
    
    // If converting this type would cause us to infinitely loop, don't do it!
    if (!isSafeToConvert(RD, *this)) {
      DeferredRecords.push_back(RD);
      return Ty;
    }
  
    // Okay, this is a definition of a type.  Compile the implementation now.
    bool InsertResult = RecordsBeingLaidOut.insert(Key).second;
    (void)InsertResult;
    assert(InsertResult && "Recursively compiling a struct?");
    
    // Force conversion of non-virtual base classes recursively.
    if (const CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(RD)) {
      for (const auto &I : CRD->bases()) {
        if (I.isVirtual()) continue;
        
        ConvertRecordDeclType(I.getType()->getAs<RecordType>()->getDecl());
      }
    }
  
    // Layout fields.
    CGRecordLayout *Layout = ComputeRecordLayout(RD, Ty);
    CGRecordLayouts[Key] = Layout;
  
    // We're done laying out this struct.
    bool EraseResult = RecordsBeingLaidOut.erase(Key); (void)EraseResult;
    assert(EraseResult && "struct not in RecordsBeingLaidOut set?");
     
    // If this struct blocked a FunctionType conversion, then recompute whatever
    // was derived from that.
    // FIXME: This is hugely overconservative.
    if (SkippedLayout)
      TypeCache.clear();
      
    // If we're done converting the outer-most record, then convert any deferred
    // structs as well.
    if (RecordsBeingLaidOut.empty())
      while (!DeferredRecords.empty())
        ConvertRecordDeclType(DeferredRecords.pop_back_val());
  
    return Ty;
  }
  
  /// getCGRecordLayout - Return record layout info for the given record decl.
  const CGRecordLayout &
  CodeGenTypes::getCGRecordLayout(const RecordDecl *RD) {
    const Type *Key = Context.getTagDeclType(RD).getTypePtr();
  
    const CGRecordLayout *Layout = CGRecordLayouts.lookup(Key);
    if (!Layout) {
      // Compute the type information.
      ConvertRecordDeclType(RD);
  
      // Now try again.
      Layout = CGRecordLayouts.lookup(Key);
    }
  
    assert(Layout && "Unable to find record layout information for type");
    return *Layout;
  }
  
  bool CodeGenTypes::isPointerZeroInitializable(QualType T) {
    assert((T->isAnyPointerType() || T->isBlockPointerType()) && "Invalid type");
    return isZeroInitializable(T);
  }
  
  bool CodeGenTypes::isZeroInitializable(QualType T) {
    if (T->getAs<PointerType>())
      return Context.getTargetNullPointerValue(T) == 0;
  
    if (const auto *AT = Context.getAsArrayType(T)) {
      if (isa<IncompleteArrayType>(AT))
        return true;
      if (const auto *CAT = dyn_cast<ConstantArrayType>(AT))
        if (Context.getConstantArrayElementCount(CAT) == 0)
          return true;
      T = Context.getBaseElementType(T);
    }
  
    // Records are non-zero-initializable if they contain any
    // non-zero-initializable subobjects.
    if (const RecordType *RT = T->getAs<RecordType>()) {
      auto RD = cast<RecordDecl>(RT->getDecl());
      return isZeroInitializable(RD);
    }
  
    // We have to ask the ABI about member pointers.
    if (const MemberPointerType *MPT = T->getAs<MemberPointerType>())
      return getCXXABI().isZeroInitializable(MPT);
    
    // Everything else is okay.
    return true;
  }
  
  bool CodeGenTypes::isZeroInitializable(const RecordDecl *RD) {
    return getCGRecordLayout(RD).isZeroInitializable();
  }
  