VariantImplDetail.h

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//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//============================================================================
// **** DO NOT EDIT THIS FILE!!! ****
// This file is automatically generated by VariantDetail.h.in
 
#if !defined(VTK_M_DEVICE) || !defined(VTK_M_NAMESPACE)
#error VarianImplDetail.h must be included from VariantImpl.h
// Some defines to make my IDE happy.
#define VTK_M_DEVICE
#define VTK_M_NAMESPACE tmp
#endif
 
#include <vtkm/List.h>
#include <vtkm/Types.h>
 
#include <vtkm/internal/Assume.h>
 
#include <vtkmstd/is_trivial.h>
 
#include <algorithm>
#include <cstddef>
#include <type_traits>
 
 
 
namespace vtkm
{
namespace VTK_M_NAMESPACE
{
namespace detail
{
 
// --------------------------------------------------------------------------------
// Helper classes to determine if all Variant types are trivial.
template <typename... Ts>
using AllTriviallyCopyable = vtkm::ListAll<vtkm::List<Ts...>, vtkmstd::is_trivially_copyable>;
 
// Single argument version of is_trivially_constructible
template <typename T>
using Constructible = vtkmstd::is_trivially_constructible<T>;
 
template <typename... Ts>
using AllTriviallyConstructible = vtkm::ListAll<vtkm::List<Ts...>, Constructible>;
 
template <typename... Ts>
using AllTriviallyDestructible =
  vtkm::ListAll<vtkm::List<Ts...>, vtkmstd::is_trivially_destructible>;
 
// --------------------------------------------------------------------------------
// Helper functions to determine the maximum type size.
#if defined(VTKM_GCC) && (__GNUC__ == 5)
// GCC5 gives an error with `sizeof(Ts)...` for an unexpanded parameter pack.
template <typename T0>
constexpr std::size_t MaxSizeOf()
{
  return sizeof(T0);
}
template <typename T0, typename T1, typename... Ts>
constexpr std::size_t MaxSizeOf()
{
  return std::max(sizeof(T0), MaxSizeOf<T1, Ts...>());
}
#else
template <typename... Ts>
constexpr std::size_t MaxSizeOf()
{
  return std::max({ sizeof(Ts)... });
}
#endif
 
// --------------------------------------------------------------------------------
// Helper functions to determine the maximum alignment size.
template <typename... Ts>
constexpr std::size_t MaxAlignmentOf()
{
  return std::max({ std::alignment_of<Ts>::value... });
}
 
// --------------------------------------------------------------------------------
// Placeholder for a fully used structure of the given type.
// This placeholder is used for compilers that do not correctly copy `struct`s
// in `union`s where some of the `struct`s have padding. This is added to the
// front of the `union` for the compiler to pick up and use.
//
// It is normally sufficient to have a full `struct`, but we have also encountered
// compilers that only use it if the alignment is at least as large. But we
// don't want the alignment too large because it can add unwanted padding
// elsewhere. Also, adding `alignas` did not work to resolve this problem for
// the compiler.
 
template <std::size_t Alignment>
struct TypeForAlignmentImpl;
template <>
struct TypeForAlignmentImpl<8>
{
  using type = vtkm::Int64;
};
template <>
struct TypeForAlignmentImpl<4>
{
  using type = vtkm::Int32;
};
template <>
struct TypeForAlignmentImpl<2>
{
  using type = vtkm::Int16;
};
template <>
struct TypeForAlignmentImpl<1>
{
  using type = vtkm::Int8;
};
template <std::size_t Alignment>
using TypeForAlignment = typename TypeForAlignmentImpl<Alignment>::type;
 
template <std::size_t Size, typename Word, bool = (Size >= 4)>
struct SizedPlaceholderImpl;
 
template <std::size_t Size, typename Word>
struct SizedPlaceholderImpl<Size, Word, true>
{
  Word A;
  Word B;
  Word C;
  Word D;
  SizedPlaceholderImpl<Size - 4, Word> E;
};
template <typename Word>
struct SizedPlaceholderImpl<4, Word, true>
{
  Word A;
  Word B;
  Word C;
  Word D;
};
 
template <std::size_t Size, typename Word>
struct SizedPlaceholderImpl<Size, Word, false>
{
  Word A;
  SizedPlaceholderImpl<Size - 1, Word> B;
};
template <typename Word>
struct SizedPlaceholderImpl<1, Word, false>
{
  Word A;
};
 
template <typename... Ts>
struct SizedPlaceholder
  : SizedPlaceholderImpl<(MaxSizeOf<Ts...>() / MaxAlignmentOf<Ts...>()),
                         TypeForAlignment<MaxAlignmentOf<Ts...>()>>
{
};
 
// clang-format off
 
// --------------------------------------------------------------------------------
// Union type used inside of Variant
//
// You may be asking yourself, why not just use an std::aligned_union rather than a real union
// type? That was our first implementation, but the problem is that the std::aligned_union
// reference needs to be recast to the actual type. Typically you would do that with
// reinterpret_cast. However, doing that leads to undefined behavior. The C++ compiler assumes that
// 2 pointers of different types point to different memory (even if it is clear that they are set
// to the same address). That means optimizers can remove code because it "knows" that data in one
// type cannot affect data in another type. (See Shafik Yaghmour's excellent writeup at
// https://gist.github.com/shafik/848ae25ee209f698763cffee272a58f8 for more details.) To safely
// change the type of an std::aligned_union, you really have to do an std::memcpy. This is
// problematic for types that cannot be trivially copied. Another problem is that we found that
// device compilers do not optimize the memcpy as well as most CPU compilers. Likely, memcpy is
// used much less frequently on GPU devices.
//
// Part of the trickiness of the union implementation is trying to preserve when the type is
// trivially constructible and copyable. The trick is that if members of the union are not trivial,
// then the default constructors are deleted. To get around that, a non-default constructor is
// added, which we can use to construct the union for non-trivial types. Working with types with
// non-trivial destructors are particularly tricky. Again, if any member of the union has a
// non-trivial destructor, the destructor is deleted. Unlike a constructor, you cannot just say to
// use a different destructor. Thus, we have to define our own destructor for the union.
// Technically, the destructor here does not do anything, but the actual destruction should be
// handled by the Variant class that contains this VariantUnion. We actually need two separate
// implementations of our union, one that defines a destructor and one that use the default
// destructor. If you define your own destructor, you can lose the trivial constructor and trivial
// copy properties.
//
 
// TD = trivially deconstructible
template <typename T0, typename... Ts>
union VariantUnionTD;
 
// NTD = non-trivially deconstructible
template <typename T0, typename... Ts>
union VariantUnionNTD;
 
template <typename T0>
union VariantUnionTD<T0>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0> Placeholder;
 
  T0 V0;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0>
union VariantUnionNTD<T0>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0> Placeholder;
 
  T0 V0;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1>
union VariantUnionTD<T0, T1>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1> Placeholder;
 
  T0 V0;
  T1 V1;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1>
union VariantUnionNTD<T0, T1>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1> Placeholder;
 
  T0 V0;
  T1 V1;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2>
union VariantUnionTD<T0, T1, T2>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2>
union VariantUnionNTD<T0, T1, T2>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2, typename T3>
union VariantUnionTD<T0, T1, T2, T3>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2, typename T3>
union VariantUnionNTD<T0, T1, T2, T3>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2, typename T3, typename T4>
union VariantUnionTD<T0, T1, T2, T3, T4>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2, typename T3, typename T4>
union VariantUnionNTD<T0, T1, T2, T3, T4>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5>
union VariantUnionTD<T0, T1, T2, T3, T4, T5>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5>
union VariantUnionNTD<T0, T1, T2, T3, T4, T5>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
union VariantUnionTD<T0, T1, T2, T3, T4, T5, T6>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6>
union VariantUnionNTD<T0, T1, T2, T3, T4, T5, T6>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7>
union VariantUnionTD<T0, T1, T2, T3, T4, T5, T6, T7>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6, T7> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  T7 V7;
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7>
union VariantUnionNTD<T0, T1, T2, T3, T4, T5, T6, T7>
{
  // Work around issue where some compilers miss initializing some struct members if another entry
  // in the varient has a struct with padding. Place an item that requires everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6, T7> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  T7 V7;
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
 
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8, typename... Ts>
union VariantUnionTD<T0, T1, T2, T3, T4, T5, T6, T7, T8, Ts...>
{
  // Work around issue where CUDA sometimes seems to miss initializing some struct members
  // if another entry in the varient has a struct with padding. Place an item that requires
  // everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6, T7, T8, Ts...> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  T7 V7;
  VariantUnionTD<T8, Ts...> Remaining;
 
  VTK_M_DEVICE VariantUnionTD(vtkm::internal::NullType) { }
  VariantUnionTD() = default;
};
 
template <typename T0, typename T1, typename T2, typename T3, typename T4, typename T5, typename T6, typename T7, typename T8, typename... Ts>
union VariantUnionNTD<T0, T1, T2, T3, T4, T5, T6, T7, T8, Ts...>
{
  // Work around issue where CUDA sometimes seems to miss initializing some struct members
  // if another entry in the varient has a struct with padding. Place an item that requires
  // everthing to be copied.
  SizedPlaceholder<T0, T1, T2, T3, T4, T5, T6, T7, T8, Ts...> Placeholder;
 
  T0 V0;
  T1 V1;
  T2 V2;
  T3 V3;
  T4 V4;
  T5 V5;
  T6 V6;
  T7 V7;
  VariantUnionNTD<T8, Ts...> Remaining;
 
  VTK_M_DEVICE VariantUnionNTD(vtkm::internal::NullType) { }
  VariantUnionNTD() = default;
  VTK_M_DEVICE ~VariantUnionNTD() { }
};
 
//clang-format on
 
template <bool TrivialConstructor, typename... Ts>
struct VariantUnionFinder;
 
template <typename... Ts>
struct VariantUnionFinder<true, Ts...>
{
  using type = VariantUnionTD<Ts...>;
};
template <typename... Ts>
struct VariantUnionFinder<false, Ts...>
{
  using type = VariantUnionNTD<Ts...>;
};
 
template <typename... Ts>
using VariantUnion =
  typename VariantUnionFinder<AllTriviallyDestructible<Ts...>::value, Ts...>::type;
 
// --------------------------------------------------------------------------------
// Methods to get values out of the variant union
template <vtkm::IdComponent I, typename UnionType>
struct VariantUnionGetImpl;
 
template <typename UnionType>
struct VariantUnionGetImpl<0, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V0);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V0;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V0;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<1, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V1);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V1;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V1;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<2, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V2);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V2;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V2;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<3, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V3);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V3;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V3;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<4, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V4);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V4;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V4;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<5, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V5);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V5;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V5;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<6, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V6);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V6;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V6;
  }
};
 
template <typename UnionType>
struct VariantUnionGetImpl<7, UnionType>
{
  using ReturnType = decltype(std::declval<UnionType>().V7);
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return storage.V7;
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return storage.V7;
  }
};
 
 
template <vtkm::IdComponent I, typename UnionType>
struct VariantUnionGetImpl
{
  VTKM_STATIC_ASSERT(I >= 8);
  using RecursiveGet = VariantUnionGetImpl<I - 8, decltype(std::declval<UnionType&>().Remaining)>;
  using ReturnType = typename RecursiveGet::ReturnType;
  VTK_M_DEVICE static ReturnType& Get(UnionType& storage) noexcept
  {
    return RecursiveGet::Get(storage.Remaining);
  }
  VTK_M_DEVICE static const ReturnType& Get(const UnionType& storage) noexcept
  {
    return RecursiveGet::Get(storage.Remaining);
  }
};
 
template <vtkm::IdComponent I, typename UnionType>
VTK_M_DEVICE auto VariantUnionGet(UnionType& storage) noexcept
  -> decltype(VariantUnionGetImpl<I, typename std::decay<UnionType>::type>::Get(storage))&
{
  return VariantUnionGetImpl<I, typename std::decay<UnionType>::type>::Get(storage);
}
 
// --------------------------------------------------------------------------------
// Internal implementation of CastAndCall for Variant
template <std::size_t NumCases>
struct VariantCases
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    VTKM_ASSERT((index >= 0) && (index < static_cast<vtkm::IdComponent>(NumCases)));
    switch (index)
    {
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
      case 4:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V4, std::forward<Args>(args)...);
      case 5:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V5, std::forward<Args>(args)...);
      case 6:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V6, std::forward<Args>(args)...);
      case 7:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V7, std::forward<Args>(args)...);
      default:
        return VariantCases<NumCases - 8>::template CastAndCall<>(
          index - 8, std::forward<Functor>(f), storage.Remaining, std::forward<Args>(args)...);
    }
  }
};
 
template<>
struct VariantCases<1>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static inline auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT(index == 0);
    (void)index;
    return f(storage.V0, std::forward<Args>(args)...);
  }
};
 
template<>
struct VariantCases<2>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 2));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<3>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 3));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<4>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 4));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<5>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 5));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
      case 4:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V4, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<6>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 6));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
      case 4:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V4, std::forward<Args>(args)...);
      case 5:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V5, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<7>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 7));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
      case 4:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V4, std::forward<Args>(args)...);
      case 5:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V5, std::forward<Args>(args)...);
      case 6:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V6, std::forward<Args>(args)...);
    }
  }
};
template<>
struct VariantCases<8>
{
  template <typename Functor, typename UnionType, typename... Args>
  VTK_M_DEVICE static
#ifdef VTKM_HIP
  // this is a temporary solution to improve Kokkos/HIP compile times for
  // ConnectivityTracer in Rendering.
  //
  // This function currently gets inlined many times, which dramatically increases
  // both compile time and the size of the resulting code-object
  __attribute__((noinline))
#else
  inline
#endif
  auto CastAndCall(
    vtkm::IdComponent index,
    Functor&& f,
    UnionType& storage,
    Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
    -> decltype(f(storage.V0, args...))
  {
    // Assume index is 0. Saves us some conditionals.
    VTKM_ASSERT((index >= 0) && (index < 8));
    switch (index)
    {
      default:
      case 0:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V0, std::forward<Args>(args)...);
      case 1:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V1, std::forward<Args>(args)...);
      case 2:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V2, std::forward<Args>(args)...);
      case 3:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V3, std::forward<Args>(args)...);
      case 4:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V4, std::forward<Args>(args)...);
      case 5:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V5, std::forward<Args>(args)...);
      case 6:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V6, std::forward<Args>(args)...);
      case 7:
        // If you get a compile error here, it probably means that you have called
        // Variant::CastAndCall with a functor that does not accept one of the types in the
        // Variant. The functor you provide must be callable with all types in the Variant, not
        // just the one that it currently holds.
        return f(storage.V7, std::forward<Args>(args)...);
    }
  }
};
 
 
template <std::size_t UnionSize, typename Functor, typename UnionType, typename... Args>
VTK_M_DEVICE inline auto VariantCastAndCallImpl(
  vtkm::IdComponent index,
  Functor&& f,
  UnionType& storage,
  Args&&... args) noexcept(noexcept(f(storage.V0, args...)))
  -> decltype(f(storage.V0, args...))
{
  return VariantCases<UnionSize>::CastAndCall(
    index, std::forward<Functor>(f), storage, std::forward<Args>(args)...);
}
 
}
}
} // vtkm::VTK_M_NAMESPACE::detail