On Tue, 12 Sept 2023, 01:21 Ken Matsui via Libstdc++, <libstd...@gcc.gnu.org>
wrote:
> This patch optimizes the performance of the is_scoped_enum trait
> by dispatching to the new __is_scoped_enum built-in trait.
>
OK for trunk (after the built-in is in the front end), thanks.
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_scoped_enum): Use
> __is_scoped_enum built-in trait.
> (is_scoped_enum_v): Likewise.
>
> Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
> ---
> libstdc++-v3/include/std/type_traits | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 677cd934b94..26ae491fa69 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -3585,6 +3585,12 @@ template<typename _Ret, typename _Fn, typename...
> _Args>
> /// True if the type is a scoped enumeration type.
> /// @since C++23
>
> +# if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
> + template<typename _Tp>
> + struct is_scoped_enum
> + : bool_constant<__is_scoped_enum(_Tp)>
> + { };
> +# else
> template<typename _Tp>
> struct is_scoped_enum
> : false_type
> @@ -3596,11 +3602,17 @@ template<typename _Ret, typename _Fn, typename...
> _Args>
> struct is_scoped_enum<_Tp>
> : bool_constant<!requires(_Tp __t, void(*__f)(int)) { __f(__t); }>
> { };
> +# endif
>
> /// @ingroup variable_templates
> /// @since C++23
> +# if _GLIBCXX_USE_BUILTIN_TRAIT(__is_scoped_enum)
> + template<typename _Tp>
> + inline constexpr bool is_scoped_enum_v = __is_scoped_enum(_Tp);
> +# else
> template<typename _Tp>
> inline constexpr bool is_scoped_enum_v = is_scoped_enum<_Tp>::value;
> +# endif
> #endif
>
> #ifdef __cpp_lib_reference_from_temporary // C++ >= 23 &&
> ref_{converts,constructs}_from_temp
> --
> 2.42.0
>
>
