[PATCH v26 01/13] libstdc++: Optimize std::is_const compilation performance

[Ken Matsui]

On Thu, May 23, 2024 at 3:15 PM Patrick Palka <ppalka@redhat.com> wrote:
>
> 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

Thank you!

>
> >
> > libstdc++-v3/ChangeLog:
> >
> >       * include/std/type_traits (is_const): Use __is_const built-in
> >       trait.
> >       (is_const_v): Likewise.
> >
> > Signed-off-by: Ken Matsui <kmatsui@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
> >
> >
>