cuda_toolkit/include/__mdspan/maybe_static_value.h

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#ifndef _LIBCUDACXX___MDSPAN_MAYBE_STATIC_VALUE_HPP
#define _LIBCUDACXX___MDSPAN_MAYBE_STATIC_VALUE_HPP

#ifndef __cuda_std__
#include <__config>
#endif // __cuda_std__

#include "../__mdspan/dynamic_extent.h"
#include "../__mdspan/macros.h"
#ifdef _LIBCUDACXX_HAS_NO_ATTRIBUTE_NO_UNIQUE_ADDRESS
#include "../__mdspan/no_unique_address.h"
#endif

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header

// This is only needed for the non-standard-layout version of partially
// static array.
// Needs to be after the includes above to work with the single header generator
#if !__MDSPAN_PRESERVE_STANDARD_LAYOUT

_LIBCUDACXX_BEGIN_NAMESPACE_STD

#if _LIBCUDACXX_STD_VER > 11

//==============================================================================

namespace __detail {

// static case
template <class _dynamic_t, class _static_t, _static_t __v,
          _static_t __is_dynamic_sentinal = dynamic_extent,
          size_t __array_entry_index = 0>
struct __maybe_static_value {
  static constexpr _static_t __static_value = __v;
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr _dynamic_t __value() const noexcept {
    return static_cast<_dynamic_t>(__v);
  }
  template <class _Up>
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr
  __mdspan_enable_fold_comma
  __set_value(_Up&& /*__rhs*/) noexcept {
    // Should we assert that the value matches the static value here?
    return {};
  }

  //--------------------------------------------------------------------------

  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  constexpr __maybe_static_value() noexcept = default;
  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  constexpr __maybe_static_value(__maybe_static_value const&) noexcept = default;
  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  constexpr __maybe_static_value(__maybe_static_value&&) noexcept = default;
  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  __MDSPAN_CONSTEXPR_14_DEFAULTED __maybe_static_value& operator=(__maybe_static_value const&) noexcept = default;
  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  __MDSPAN_CONSTEXPR_14_DEFAULTED __maybe_static_value& operator=(__maybe_static_value&&) noexcept = default;
  __MDSPAN_INLINE_FUNCTION_DEFAULTED
  ~__maybe_static_value() noexcept = default;

  __MDSPAN_INLINE_FUNCTION
  constexpr explicit __maybe_static_value(_dynamic_t const&) noexcept {
    // Should we assert that the value matches the static value here?
  }

  //--------------------------------------------------------------------------

};

// dynamic case
template <class _dynamic_t, class _static_t, _static_t __is_dynamic_sentinal, size_t __array_entry_index>
struct __maybe_static_value<_dynamic_t, _static_t, __is_dynamic_sentinal, __is_dynamic_sentinal,
                            __array_entry_index>
#ifdef _LIBCUDACXX_HAS_NO_ATTRIBUTE_NO_UNIQUE_ADDRESS
    : __no_unique_address_emulation<_Tp>
#endif
{
  static constexpr _static_t __static_value = __is_dynamic_sentinal;
#ifndef _LIBCUDACXX_HAS_NO_ATTRIBUTE_NO_UNIQUE_ADDRESS
  _LIBCUDACXX_NO_UNIQUE_ADDRESS _dynamic_t __v = {};
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr _dynamic_t __value() const noexcept {
    return __v;
  }
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr _dynamic_t &__ref() noexcept {
    return __v;
  }
  template <class _Up>
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr
  __mdspan_enable_fold_comma
  __set_value(_Up&& __rhs) noexcept {
    __v = (_Up &&)rhs;
    return {};
  }
#else
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr _dynamic_t __value() const noexcept {
    return this->__no_unique_address_emulation<_dynamic_t>::__ref();
  }
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr _dynamic_t &__ref() noexcept {
    return this->__no_unique_address_emulation<_dynamic_t>::__ref();
  }
  template <class _Up>
  __MDSPAN_FORCE_INLINE_FUNCTION constexpr
  __mdspan_enable_fold_comma
  __set_value(_Up&& __rhs) noexcept {
    this->__no_unique_address_emulation<_dynamic_t>::__ref() = (_Up &&)__rhs;
    return {};
  }
#endif
};

} // namespace __detail

//==============================================================================


#endif // _LIBCUDACXX_STD_VER > 11

_LIBCUDACXX_END_NAMESPACE_STD

#endif // !__MDSPAN_PRESERVE_STANDARD_LAYOUT

#endif // _LIBCUDACXX___MDSPAN_MAYBE_STATIC_VALUE_HPP