On Tue, Oct 24, 2023 at 4:02 AM Jonathan Wakely <jwak...@redhat.com> wrote: > > > > On Tue, 24 Oct 2023 at 03:16, Ken Matsui <kmat...@gcc.gnu.org> wrote: >> >> This patch optimizes the compilation performance of std::is_function >> by dispatching to the new __is_function built-in trait. >> >> libstdc++-v3/ChangeLog: >> >> * include/std/type_traits (is_function): Use __is_function >> built-in trait. >> (is_function_v): Likewise. Optimize its implementation. >> (is_const_v): Move on top of is_function_v as is_function_v now >> depends on is_const_v. > > > I think I'd prefer to keep is_const_v where it is now, adjacent to > is_volatile_v, and move is_function_v after those. > > i.e. like this (but with the additional changes to use the new built-in): > > --- a/libstdc++-v3/include/std/type_traits > +++ b/libstdc++-v3/include/std/type_traits > @@ -3198,8 +3198,8 @@ template <typename _Tp> > inline constexpr bool is_union_v = __is_union(_Tp); > template <typename _Tp> > inline constexpr bool is_class_v = __is_class(_Tp); > -template <typename _Tp> > - inline constexpr bool is_function_v = is_function<_Tp>::value; > +// is_function_v is defined below, after is_const_v. > + > template <typename _Tp> > inline constexpr bool is_reference_v = false; > template <typename _Tp> > @@ -3226,6 +3226,8 @@ template <typename _Tp> > inline constexpr bool is_volatile_v = false; > template <typename _Tp> > inline constexpr bool is_volatile_v<volatile _Tp> = true; > +template <typename _Tp> > + inline constexpr bool is_function_v = is_function<_Tp>::value; > > template <typename _Tp> > inline constexpr bool is_trivial_v = __is_trivial(_Tp); > > The variable templates are currently defined in the order shown in the > standard, in te [meta.type.synop] synopsis, and in the [meta.unary.cat] > table. So let's move _is_function_v later and add a comment saying why it's > not in the expected place. > >
Sorry for missing this. Thank you for your review! That totally makes sense, and I will update my patches accordingly.
