On Mon, Oct 16, 2023 at 11:04 AM Patrick Palka <ppa...@redhat.com> wrote:
>
> On Sun, 15 Oct 2023, Ken Matsui wrote:
>
> > This patch optimizes the performance of the is_object trait by dispatching
> > to
> > the new __is_function and __is_reference built-in traits.
> >
> > libstdc++-v3/ChangeLog:
> > * include/std/type_traits (is_object): Use __is_function and
> > __is_reference built-in traits.
> > (is_object_v): Likewise.
> >
> > Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
> > ---
> > libstdc++-v3/include/std/type_traits | 18 ++++++++++++++++++
> > 1 file changed, 18 insertions(+)
> >
> > diff --git a/libstdc++-v3/include/std/type_traits
> > b/libstdc++-v3/include/std/type_traits
> > index bd57488824b..674d398c075 100644
> > --- a/libstdc++-v3/include/std/type_traits
> > +++ b/libstdc++-v3/include/std/type_traits
> > @@ -725,11 +725,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > { };
> >
> > /// is_object
> > +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function) \
> > + && _GLIBCXX_USE_BUILTIN_TRAIT(__is_reference)
> > + template<typename _Tp>
> > + struct is_object
> > + : public __bool_constant<!(__is_function(_Tp) || __is_reference(_Tp)
> > + || is_void<_Tp>::value)>
> > + { };
>
> Since is_object is one of the more commonly used traits, we should
> probably just define a built-in for it. (Either way we'd have to
> repeat the logic twice, either once in the frontend and once in
> the library, or twice in the library (is_object and is_object_v),
> so might as well do the more efficient approach).
>
Sure, I'll implement it :) Thank you for your review!
> > +#else
> > template<typename _Tp>
> > struct is_object
> > : public __not_<__or_<is_function<_Tp>, is_reference<_Tp>,
> > is_void<_Tp>>>::type
> > { };
> > +#endif
> >
> > template<typename>
> > struct is_member_pointer;
> > @@ -3305,8 +3314,17 @@ template <typename _Tp>
> > inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
> > template <typename _Tp>
> > inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
> > +
> > +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function) \
> > + && _GLIBCXX_USE_BUILTIN_TRAIT(__is_reference)
> > +template <typename _Tp>
> > + inline constexpr bool is_object_v
> > + = !(__is_function(_Tp) || __is_reference(_Tp) || is_void<_Tp>::value);
> > +#else
> > template <typename _Tp>
> > inline constexpr bool is_object_v = is_object<_Tp>::value;
> > +#endif
> > +
> > template <typename _Tp>
> > inline constexpr bool is_scalar_v = is_scalar<_Tp>::value;
> > template <typename _Tp>
> > --
> > 2.42.0
> >
> >
>
