On Wed, 10 Jan 2024 at 19:47, Ken Matsui <kmat...@gcc.gnu.org> wrote:
>
> This patch optimizes the compilation performance of std::is_signed
> by dispatching to the new __is_signed built-in trait.
OK for trunk (if the new built-in is approved).
>
> libstdc++-v3/ChangeLog:
>
> * include/std/type_traits (is_signed): Use __is_signed built-in
> trait.
> (is_signed_v): Likewise.
>
> Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
> ---
> libstdc++-v3/include/std/type_traits | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> index 4bcfb1389e3..b917c743aea 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -968,6 +968,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> : public __bool_constant<__is_abstract(_Tp)>
> { };
>
> + /// is_signed
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_signed)
> + template<typename _Tp>
> + struct is_signed
> + : public __bool_constant<__is_signed(_Tp)>
> + { };
> +#else
> /// @cond undocumented
> template<typename _Tp,
> bool = is_arithmetic<_Tp>::value>
> @@ -980,11 +987,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> { };
> /// @endcond
>
> - /// is_signed
> template<typename _Tp>
> struct is_signed
> : public __is_signed_helper<_Tp>::type
> { };
> +#endif
>
> /// is_unsigned
> #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_unsigned)
> @@ -3418,8 +3425,13 @@ template <typename _Tp>
> template <typename _Tp>
> inline constexpr bool is_final_v = __is_final(_Tp);
>
> +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_signed)
> +template <typename _Tp>
> + inline constexpr bool is_signed_v = __is_signed(_Tp);
> +#else
> template <typename _Tp>
> inline constexpr bool is_signed_v = is_signed<_Tp>::value;
> +#endif
>
> #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_unsigned)
> template <typename _Tp>
> --
> 2.43.0
>
