On Wed, Jul 12, 2023 at 3:01 AM Jonathan Wakely <jwak...@redhat.com> wrote: > > On Mon, 10 Jul 2023 at 06:51, Ken Matsui via Libstdc++ > <libstd...@gcc.gnu.org> wrote: > > > > Hi, > > > > Here is the benchmark result for is_pointer: > > > > https://github.com/ken-matsui/gcc-benches/blob/main/is_pointer.md#sun-jul--9-103948-pm-pdt-2023 > > > > Time: -62.1344% > > Peak Memory Usage: -52.4281% > > Total Memory Usage: -53.5889% > > Wow! > > Although maybe we could have improved our std::is_pointer_v anyway, like so: > > template <typename _Tp> > 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; > > I'm not sure why I didn't already do that. > > Could you please benchmark that? And if it is better than the current > impl using is_pointer<_Tp>::value then we should do this in the > library: > > #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 = 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
Hi François and Jonathan, Thank you for your reviews! I will rename the four underscores to the appropriate name and take a benchmark once I get home. If I apply your change on is_pointer_v, is it better to add the `Co-authored-by:` line in the commit?
