On Sat, 11 May 2024, Ken Matsui wrote:
> This patch optimizes the compilation performance of std::is_const
> by dispatching to the new __is_const built-in trait.
This patch series LGTM
>
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_const): Use __is_const built-in
> trait.
> (is_const_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 b441bf9908f..8df0cf3ac3b 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -835,6 +835,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> // Type properties.
>
> /// is_const
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_const)
> + template<typename _Tp>
> + struct is_const
> + : public __bool_constant<__is_const(_Tp)>
> + { };
> +#else
> template<typename>
> struct is_const
> : public false_type { };
> @@ -842,6 +848,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> template<typename _Tp>
> struct is_const<_Tp const>
> : public true_type { };
> +#endif
>
> /// is_volatile
> template<typename>
> @@ -3331,10 +3338,15 @@ template <typename _Tp>
> inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
> #endif
>
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_const)
> +template <typename _Tp>
> + inline constexpr bool is_const_v = __is_const(_Tp);
> +#else
> template <typename _Tp>
> inline constexpr bool is_const_v = false;
> template <typename _Tp>
> inline constexpr bool is_const_v<const _Tp> = true;
> +#endif
>
> #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function)
> template <typename _Tp>
> --
> 2.44.0
>
>
