[PING][PATCH v6 2/2] libstdc++: Use new built-in trait __is_pointer

[Ken Matsui <kmatsui@cs.washington.edu>]

Ping for the use of __is_pointer built-in.

Sincerely,
Ken Matsui

On Thu, Jul 13, 2023 at 1:49 PM Ken Matsui <kmatsui@gcc.gnu.org> wrote:
>
> This patch lets libstdc++ use new built-in trait __is_pointer.
>
> libstdc++-v3/ChangeLog:
>
>         * include/bits/cpp_type_traits.h (__is_ptr): Use __is_pointer
>         built-in trait.
>         * include/std/type_traits (is_pointer): Likewise. Optimize its
>         implementation.
>         (is_pointer_v): Likewise.
>
> Co-authored-by: Jonathan Wakely <jwakely@redhat.com>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/bits/cpp_type_traits.h |  8 ++++
>  libstdc++-v3/include/std/type_traits        | 44 +++++++++++++++++----
>  2 files changed, 44 insertions(+), 8 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
> index 3711e4be526..4da1e7c407c 100644
> --- a/libstdc++-v3/include/bits/cpp_type_traits.h
> +++ b/libstdc++-v3/include/bits/cpp_type_traits.h
> @@ -363,6 +363,13 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
>    //
>    // Pointer types
>    //
> +#if __has_builtin(__is_pointer)
> +  template<typename _Tp>
> +    struct __is_ptr : __truth_type<__is_pointer(_Tp)>
> +    {
> +      enum { __value = __is_pointer(_Tp) };
> +    };
> +#else
>    template<typename _Tp>
>      struct __is_ptr
>      {
> @@ -376,6 +383,7 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
>        enum { __value = 1 };
>        typedef __true_type __type;
>      };
> +#endif
>
>    //
>    // An arithmetic type is an integer type or a floating point type
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 0e7a9c9c7f3..16b2f6de536 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -515,19 +515,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      struct is_array<_Tp[]>
>      : public true_type { };
>
> -  template<typename>
> -    struct __is_pointer_helper
> +  /// is_pointer
> +#if __has_builtin(__is_pointer)
> +  template<typename _Tp>
> +    struct is_pointer
> +    : public __bool_constant<__is_pointer(_Tp)>
> +    { };
> +#else
> +  template<typename _Tp>
> +    struct is_pointer
>      : public false_type { };
>
>    template<typename _Tp>
> -    struct __is_pointer_helper<_Tp*>
> +    struct is_pointer<_Tp*>
>      : public true_type { };
>
> -  /// is_pointer
>    template<typename _Tp>
> -    struct is_pointer
> -    : public __is_pointer_helper<__remove_cv_t<_Tp>>::type
> -    { };
> +    struct is_pointer<_Tp* const>
> +    : public true_type { };
> +
> +  template<typename _Tp>
> +    struct is_pointer<_Tp* volatile>
> +    : public true_type { };
> +
> +  template<typename _Tp>
> +    struct is_pointer<_Tp* const volatile>
> +    : public true_type { };
> +#endif
>
>    /// is_lvalue_reference
>    template<typename>
> @@ -3168,8 +3182,22 @@ template <typename _Tp>
>  template <typename _Tp, size_t _Num>
>    inline constexpr bool is_array_v<_Tp[_Num]> = true;
>
> +#if __has_builtin(__is_pointer)
> +template <typename _Tp>
> +  inline constexpr bool is_pointer_v = __is_pointer(_Tp);
> +#else
>  template <typename _Tp>
> -  inline constexpr bool is_pointer_v = is_pointer<_Tp>::value;
> +  inline constexpr bool is_pointer_v = false;
> +template <typename _Tp>
> +  inline constexpr bool is_pointer_v<_Tp*> = true;
> +template <typename _Tp>
> +  inline constexpr bool is_pointer_v<_Tp* const> = true;
> +template <typename _Tp>
> +  inline constexpr bool is_pointer_v<_Tp* volatile> = true;
> +template <typename _Tp>
> +  inline constexpr bool is_pointer_v<_Tp* const volatile> = true;
> +#endif
> +
>  template <typename _Tp>
>    inline constexpr bool is_lvalue_reference_v = false;
>  template <typename _Tp>
> --
> 2.41.0
>