[v2,3/3] libstdc++: Optimize is_fundamental performance by __is_arithmetic built-in

Message ID 20230715045519.50684-3-kmatsui@gcc.gnu.org
State Accepted
Headers
Series [v2,1/3] c++, libstdc++: Implement __is_arithmetic built-in trait |

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Context Check Description
snail/gcc-patch-check success Github commit url

Commit Message

Ken Matsui July 15, 2023, 4:55 a.m. UTC
  This patch optimizes the performance of the is_fundamental trait by
dispatching to the new __is_arithmetic built-in trait.

libstdc++-v3/ChangeLog:

	* include/std/type_traits (is_fundamental_v): Use __is_arithmetic
	built-in trait.
	(is_fundamental): Likewise. Optimize the original implementation.

Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
---
 libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)
  

Comments

Ken Matsui July 15, 2023, 5:07 a.m. UTC | #1
Hi,

Here are the benchmarks for this change:

* is_fundamental

https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental.md#fri-jul-14-091146-pm-pdt-2023

Time: -37.1619%
Peak Memory Usage: -29.4294%
Total Memory Usage: -29.4783%

* is_fundamental_v

https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental_v.md#fri-jul-14-091757-pm-pdt-2023

Time: -35.5446%
Peak Memory Usage: -30.0096%
Total Memory Usage: -30.6021%

* is_fundamental with bool_constant (on trunk
[18dac101678b8c0aed4bd995351e47f26cd54dec])

https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-bool_constant.md#fri-jul-14-094237-pm-pdt-2023

Time: -28.3908%
Peak Memory Usage: -18.5403%
Total Memory Usage: -19.9045%

---

It appears using bool_constant is better than disjunction. If my
understanding is correct, disjunction can avoid later instantiations
when short-circuiting, but might the evaluation of disjunction be more
expensive than evaluating is_void and is_null_pointer? Or my benchmark
might be just incorrect.

Sincerely,
Ken Matsui

On Fri, Jul 14, 2023 at 9:57 PM Ken Matsui <kmatsui@gcc.gnu.org> wrote:
>
> This patch optimizes the performance of the is_fundamental trait by
> dispatching to the new __is_arithmetic built-in trait.
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
>         built-in trait.
>         (is_fundamental): Likewise. Optimize the original implementation.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>  libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 7ebbe04c77b..cf24de2fcac 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #endif
>
>    /// is_fundamental
> +#if __has_builtin(__is_arithmetic)
> +  template<typename _Tp>
> +    struct is_fundamental
> +    : public __bool_constant<__is_arithmetic(_Tp)
> +                             || is_void<_Tp>::value
> +                             || is_null_pointer<_Tp>::value>
> +    { };
> +#else
>    template<typename _Tp>
>      struct is_fundamental
> -    : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
> -                  is_null_pointer<_Tp>>::type
> +    : public __bool_constant<is_arithmetic<_Tp>::value
> +                             || is_void<_Tp>::value
> +                             || is_null_pointer<_Tp>::value>
>      { };
> +#endif
>
>    /// is_object
>    template<typename _Tp>
> @@ -3209,13 +3219,16 @@ template <typename _Tp>
>  #if __has_builtin(__is_arithmetic)
>  template <typename _Tp>
>    inline constexpr bool is_arithmetic_v = __is_arithmetic(_Tp);
> +template <typename _Tp>
> +  inline constexpr bool is_fundamental_v
> +    = __is_arithmetic(_Tp) || is_void_v<_Tp> || is_null_pointer_v<_Tp>;
>  #else
>  template <typename _Tp>
>    inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
> -#endif
> -
>  template <typename _Tp>
>    inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
> +#endif
> +
>  template <typename _Tp>
>    inline constexpr bool is_object_v = is_object<_Tp>::value;
>  template <typename _Tp>
> --
> 2.41.0
>
  
François Dumont July 16, 2023, 12:41 p.m. UTC | #2
On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> This patch optimizes the performance of the is_fundamental trait by
> dispatching to the new __is_arithmetic built-in trait.
>
> libstdc++-v3/ChangeLog:
>
> 	* include/std/type_traits (is_fundamental_v): Use __is_arithmetic
> 	built-in trait.
> 	(is_fundamental): Likewise. Optimize the original implementation.
>
> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> ---
>   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
>   1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> index 7ebbe04c77b..cf24de2fcac 100644
> --- a/libstdc++-v3/include/std/type_traits
> +++ b/libstdc++-v3/include/std/type_traits
> @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>   #endif
>   
>     /// is_fundamental
> +#if __has_builtin(__is_arithmetic)
> +  template<typename _Tp>
> +    struct is_fundamental
> +    : public __bool_constant<__is_arithmetic(_Tp)
> +                             || is_void<_Tp>::value
> +                             || is_null_pointer<_Tp>::value>
> +    { };

What about doing this ?

   template<typename _Tp>
     struct is_fundamental
     : public __bool_constant<__is_arithmetic(_Tp)
                              || __or_<is_void<_Tp>,
				      is_null_pointer<_Tp>>::value>
     { };

Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
  
Ken Matsui July 17, 2023, 4:49 a.m. UTC | #3
On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
>
>
> On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> > This patch optimizes the performance of the is_fundamental trait by
> > dispatching to the new __is_arithmetic built-in trait.
> >
> > libstdc++-v3/ChangeLog:
> >
> >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
> >       built-in trait.
> >       (is_fundamental): Likewise. Optimize the original implementation.
> >
> > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > ---
> >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> >   1 file changed, 17 insertions(+), 4 deletions(-)
> >
> > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> > index 7ebbe04c77b..cf24de2fcac 100644
> > --- a/libstdc++-v3/include/std/type_traits
> > +++ b/libstdc++-v3/include/std/type_traits
> > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >   #endif
> >
> >     /// is_fundamental
> > +#if __has_builtin(__is_arithmetic)
> > +  template<typename _Tp>
> > +    struct is_fundamental
> > +    : public __bool_constant<__is_arithmetic(_Tp)
> > +                             || is_void<_Tp>::value
> > +                             || is_null_pointer<_Tp>::value>
> > +    { };
>
> What about doing this ?
>
>    template<typename _Tp>
>      struct is_fundamental
>      : public __bool_constant<__is_arithmetic(_Tp)
>                               || __or_<is_void<_Tp>,
>                                       is_null_pointer<_Tp>>::value>
>      { };
>
> Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
>
Let me take a benchmark for this later.
  
Ken Matsui July 18, 2023, 6:24 a.m. UTC | #4
Hi,

I took a benchmark for this.

https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023

template<typename _Tp>
struct is_fundamental
: public std::bool_constant<__is_arithmetic(_Tp)
                            || std::is_void<_Tp>::value
                            || std::is_null_pointer<_Tp>::value>
{ };

is faster than:

template<typename _Tp>
struct is_fundamental
: public std::bool_constant<__is_arithmetic(_Tp)
                            || std::disjunction<std::is_void<_Tp>,
                                                std::is_null_pointer<_Tp>
                                                >::value>
{ };

Time: -32.2871%
Peak Memory: -18.5071%
Total Memory: -20.1991%

Sincerely,
Ken Matsui

On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
> >
> >
> > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> > > This patch optimizes the performance of the is_fundamental trait by
> > > dispatching to the new __is_arithmetic built-in trait.
> > >
> > > libstdc++-v3/ChangeLog:
> > >
> > >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
> > >       built-in trait.
> > >       (is_fundamental): Likewise. Optimize the original implementation.
> > >
> > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > > ---
> > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> > >   1 file changed, 17 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> > > index 7ebbe04c77b..cf24de2fcac 100644
> > > --- a/libstdc++-v3/include/std/type_traits
> > > +++ b/libstdc++-v3/include/std/type_traits
> > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > >   #endif
> > >
> > >     /// is_fundamental
> > > +#if __has_builtin(__is_arithmetic)
> > > +  template<typename _Tp>
> > > +    struct is_fundamental
> > > +    : public __bool_constant<__is_arithmetic(_Tp)
> > > +                             || is_void<_Tp>::value
> > > +                             || is_null_pointer<_Tp>::value>
> > > +    { };
> >
> > What about doing this ?
> >
> >    template<typename _Tp>
> >      struct is_fundamental
> >      : public __bool_constant<__is_arithmetic(_Tp)
> >                               || __or_<is_void<_Tp>,
> >                                       is_null_pointer<_Tp>>::value>
> >      { };
> >
> > Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
> >
> Let me take a benchmark for this later.
  
Ken Matsui July 18, 2023, 6:26 a.m. UTC | #5
I will eventually work on disjunction to somehow optimize, but in the
meantime, this might be a better implementation. Of course, my
benchmark could be wrong.

On Mon, Jul 17, 2023 at 11:24 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> Hi,
>
> I took a benchmark for this.
>
> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                             || std::is_void<_Tp>::value
>                             || std::is_null_pointer<_Tp>::value>
> { };
>
> is faster than:
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                             || std::disjunction<std::is_void<_Tp>,
>                                                 std::is_null_pointer<_Tp>
>                                                 >::value>
> { };
>
> Time: -32.2871%
> Peak Memory: -18.5071%
> Total Memory: -20.1991%
>
> Sincerely,
> Ken Matsui
>
> On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
> >
> > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
> > >
> > >
> > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> > > > This patch optimizes the performance of the is_fundamental trait by
> > > > dispatching to the new __is_arithmetic built-in trait.
> > > >
> > > > libstdc++-v3/ChangeLog:
> > > >
> > > >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
> > > >       built-in trait.
> > > >       (is_fundamental): Likewise. Optimize the original implementation.
> > > >
> > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > > > ---
> > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> > > >   1 file changed, 17 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> > > > index 7ebbe04c77b..cf24de2fcac 100644
> > > > --- a/libstdc++-v3/include/std/type_traits
> > > > +++ b/libstdc++-v3/include/std/type_traits
> > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > > >   #endif
> > > >
> > > >     /// is_fundamental
> > > > +#if __has_builtin(__is_arithmetic)
> > > > +  template<typename _Tp>
> > > > +    struct is_fundamental
> > > > +    : public __bool_constant<__is_arithmetic(_Tp)
> > > > +                             || is_void<_Tp>::value
> > > > +                             || is_null_pointer<_Tp>::value>
> > > > +    { };
> > >
> > > What about doing this ?
> > >
> > >    template<typename _Tp>
> > >      struct is_fundamental
> > >      : public __bool_constant<__is_arithmetic(_Tp)
> > >                               || __or_<is_void<_Tp>,
> > >                                       is_null_pointer<_Tp>>::value>
> > >      { };
> > >
> > > Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
> > >
> > Let me take a benchmark for this later.
  
François Dumont July 22, 2023, 1:45 p.m. UTC | #6
It seems rather logical cause std::disjunction is supposed to avoid 
instantiations but in case of:

std::disjunction<std::is_void<_Tp>, std::is_null_pointer<_Tp>>

you'll avoid std::is_null_pointer instantiation only for 'void' type and 
at the price of instantiating std::disjunction so 2 instantiations at 
best but most of the time 3, clearly useless here.

On 18/07/2023 08:24, Ken Matsui wrote:
> Hi,
>
> I took a benchmark for this.
>
> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                              || std::is_void<_Tp>::value
>                              || std::is_null_pointer<_Tp>::value>
> { };
>
> is faster than:
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                              || std::disjunction<std::is_void<_Tp>,
>                                                  std::is_null_pointer<_Tp>
>                                                  >::value>
> { };
>
> Time: -32.2871%
> Peak Memory: -18.5071%
> Total Memory: -20.1991%
>
> Sincerely,
> Ken Matsui
>
> On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>> On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
>>>
>>> On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
>>>> This patch optimizes the performance of the is_fundamental trait by
>>>> dispatching to the new __is_arithmetic built-in trait.
>>>>
>>>> libstdc++-v3/ChangeLog:
>>>>
>>>>        * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
>>>>        built-in trait.
>>>>        (is_fundamental): Likewise. Optimize the original implementation.
>>>>
>>>> Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
>>>> ---
>>>>    libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
>>>>    1 file changed, 17 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
>>>> index 7ebbe04c77b..cf24de2fcac 100644
>>>> --- a/libstdc++-v3/include/std/type_traits
>>>> +++ b/libstdc++-v3/include/std/type_traits
>>>> @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>>>>    #endif
>>>>
>>>>      /// is_fundamental
>>>> +#if __has_builtin(__is_arithmetic)
>>>> +  template<typename _Tp>
>>>> +    struct is_fundamental
>>>> +    : public __bool_constant<__is_arithmetic(_Tp)
>>>> +                             || is_void<_Tp>::value
>>>> +                             || is_null_pointer<_Tp>::value>
>>>> +    { };
>>> What about doing this ?
>>>
>>>     template<typename _Tp>
>>>       struct is_fundamental
>>>       : public __bool_constant<__is_arithmetic(_Tp)
>>>                                || __or_<is_void<_Tp>,
>>>                                        is_null_pointer<_Tp>>::value>
>>>       { };
>>>
>>> Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
>>>
>> Let me take a benchmark for this later.
  
Jonathan Wakely Aug. 8, 2023, 8:14 p.m. UTC | #7
On Tue, 18 Jul 2023 at 07:28, Ken Matsui via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> I will eventually work on disjunction to somehow optimize, but in the
> meantime, this might be a better implementation. Of course, my
> benchmark could be wrong.
>

You should use __or_ internally in libstdc++ code, not std::disjunction.

Patrick already optimized both of those, and __or_ is slightly faster
(because it doesn't have to conform to the full requirements of
std::disjunction).

A compiler built-in for __or_ / __disjunction might perform better. But
eventually if we're going to have built-ins for all of __is_arithmetic,
__is_void, and __is_null_pointer, then we would want simply:

__is_arithmetic(T) || __is_void(T) || __is_null_pointer(T)

and so we wouldn't need to avoid instantiating any class templates at all.



>
> On Mon, Jul 17, 2023 at 11:24 PM Ken Matsui <kmatsui@cs.washington.edu>
> wrote:
> >
> > Hi,
> >
> > I took a benchmark for this.
> >
> >
> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
> >
> > template<typename _Tp>
> > struct is_fundamental
> > : public std::bool_constant<__is_arithmetic(_Tp)
> >                             || std::is_void<_Tp>::value
> >                             || std::is_null_pointer<_Tp>::value>
> > { };
> >
> > is faster than:
> >
> > template<typename _Tp>
> > struct is_fundamental
> > : public std::bool_constant<__is_arithmetic(_Tp)
> >                             || std::disjunction<std::is_void<_Tp>,
> >                                                 std::is_null_pointer<_Tp>
> >                                                 >::value>
> > { };
> >
> > Time: -32.2871%
> > Peak Memory: -18.5071%
> > Total Memory: -20.1991%
> >
> > Sincerely,
> > Ken Matsui
> >
> > On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu>
> wrote:
> > >
> > > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com>
> wrote:
> > > >
> > > >
> > > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> > > > > This patch optimizes the performance of the is_fundamental trait by
> > > > > dispatching to the new __is_arithmetic built-in trait.
> > > > >
> > > > > libstdc++-v3/ChangeLog:
> > > > >
> > > > >       * include/std/type_traits (is_fundamental_v): Use
> __is_arithmetic
> > > > >       built-in trait.
> > > > >       (is_fundamental): Likewise. Optimize the original
> implementation.
> > > > >
> > > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > > > > ---
> > > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> > > > >   1 file changed, 17 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> > > > > index 7ebbe04c77b..cf24de2fcac 100644
> > > > > --- a/libstdc++-v3/include/std/type_traits
> > > > > +++ b/libstdc++-v3/include/std/type_traits
> > > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > > > >   #endif
> > > > >
> > > > >     /// is_fundamental
> > > > > +#if __has_builtin(__is_arithmetic)
> > > > > +  template<typename _Tp>
> > > > > +    struct is_fundamental
> > > > > +    : public __bool_constant<__is_arithmetic(_Tp)
> > > > > +                             || is_void<_Tp>::value
> > > > > +                             || is_null_pointer<_Tp>::value>
> > > > > +    { };
> > > >
> > > > What about doing this ?
> > > >
> > > >    template<typename _Tp>
> > > >      struct is_fundamental
> > > >      : public __bool_constant<__is_arithmetic(_Tp)
> > > >                               || __or_<is_void<_Tp>,
> > > >                                       is_null_pointer<_Tp>>::value>
> > > >      { };
> > > >
> > > > Based on your benches it seems that builtin __is_arithmetic is much
> better that std::is_arithmetic. But __or_ could still avoid instantiation
> of is_null_pointer.
> > > >
> > > Let me take a benchmark for this later.
>
>
  
Jonathan Wakely Aug. 8, 2023, 8:18 p.m. UTC | #8
On Tue, 18 Jul 2023 at 07:25, Ken Matsui via Libstdc++ <
libstdc++@gcc.gnu.org> wrote:

> Hi,
>
> I took a benchmark for this.
>
>
> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                             || std::is_void<_Tp>::value
>                             || std::is_null_pointer<_Tp>::value>
> { };
>
> is faster than:
>
> template<typename _Tp>
> struct is_fundamental
> : public std::bool_constant<__is_arithmetic(_Tp)
>                             || std::disjunction<std::is_void<_Tp>,
>                                                 std::is_null_pointer<_Tp>
>                                                 >::value>
> { };
>
> Time: -32.2871%
> Peak Memory: -18.5071%
> Total Memory: -20.1991%
>

But what about the fallback implementation of is_fundamental where we don't
have the __is_arithmetic built-in?

-    : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
-                  is_null_pointer<_Tp>>::type
+    : public __bool_constant<is_arithmetic<_Tp>::value
+                             || is_void<_Tp>::value
+                             || is_null_pointer<_Tp>::value>

Here the use of __or_ means that for is_fundamental<int> we don't
instantiate is_void<int> and is_null_pointer<int>. Isn't that still
worthwhile?





>
> Sincerely,
> Ken Matsui
>
> On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu>
> wrote:
> >
> > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com>
> wrote:
> > >
> > >
> > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> > > > This patch optimizes the performance of the is_fundamental trait by
> > > > dispatching to the new __is_arithmetic built-in trait.
> > > >
> > > > libstdc++-v3/ChangeLog:
> > > >
> > > >       * include/std/type_traits (is_fundamental_v): Use
> __is_arithmetic
> > > >       built-in trait.
> > > >       (is_fundamental): Likewise. Optimize the original
> implementation.
> > > >
> > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > > > ---
> > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> > > >   1 file changed, 17 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/libstdc++-v3/include/std/type_traits
> b/libstdc++-v3/include/std/type_traits
> > > > index 7ebbe04c77b..cf24de2fcac 100644
> > > > --- a/libstdc++-v3/include/std/type_traits
> > > > +++ b/libstdc++-v3/include/std/type_traits
> > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > > >   #endif
> > > >
> > > >     /// is_fundamental
> > > > +#if __has_builtin(__is_arithmetic)
> > > > +  template<typename _Tp>
> > > > +    struct is_fundamental
> > > > +    : public __bool_constant<__is_arithmetic(_Tp)
> > > > +                             || is_void<_Tp>::value
> > > > +                             || is_null_pointer<_Tp>::value>
> > > > +    { };
> > >
> > > What about doing this ?
> > >
> > >    template<typename _Tp>
> > >      struct is_fundamental
> > >      : public __bool_constant<__is_arithmetic(_Tp)
> > >                               || __or_<is_void<_Tp>,
> > >                                       is_null_pointer<_Tp>>::value>
> > >      { };
> > >
> > > Based on your benches it seems that builtin __is_arithmetic is much
> better that std::is_arithmetic. But __or_ could still avoid instantiation
> of is_null_pointer.
> > >
> > Let me take a benchmark for this later.
>
>
  
Ken Matsui Aug. 31, 2023, 1:47 p.m. UTC | #9
On Tue, Aug 8, 2023 at 1:14 PM Jonathan Wakely <jwakely@redhat.com> wrote:
>
>
>
> On Tue, 18 Jul 2023 at 07:28, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
>>
>> I will eventually work on disjunction to somehow optimize, but in the
>> meantime, this might be a better implementation. Of course, my
>> benchmark could be wrong.
>
>
> You should use __or_ internally in libstdc++ code, not std::disjunction.
>
> Patrick already optimized both of those, and __or_ is slightly faster (because it doesn't have to conform to the full requirements of std::disjunction).
>
I will! Thank you!

> A compiler built-in for __or_ / __disjunction might perform better. But eventually if we're going to have built-ins for all of __is_arithmetic, __is_void, and __is_null_pointer, then we would want simply:
>
> __is_arithmetic(T) || __is_void(T) || __is_null_pointer(T)
>
> and so we wouldn't need to avoid instantiating any class templates at all.
>
I think we are not going to define built-ins for is_void and
is_null_pointer as their type trait implementations are already
optimal.

>
>>
>>
>> On Mon, Jul 17, 2023 at 11:24 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>> >
>> > Hi,
>> >
>> > I took a benchmark for this.
>> >
>> > https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
>> >
>> > template<typename _Tp>
>> > struct is_fundamental
>> > : public std::bool_constant<__is_arithmetic(_Tp)
>> >                             || std::is_void<_Tp>::value
>> >                             || std::is_null_pointer<_Tp>::value>
>> > { };
>> >
>> > is faster than:
>> >
>> > template<typename _Tp>
>> > struct is_fundamental
>> > : public std::bool_constant<__is_arithmetic(_Tp)
>> >                             || std::disjunction<std::is_void<_Tp>,
>> >                                                 std::is_null_pointer<_Tp>
>> >                                                 >::value>
>> > { };
>> >
>> > Time: -32.2871%
>> > Peak Memory: -18.5071%
>> > Total Memory: -20.1991%
>> >
>> > Sincerely,
>> > Ken Matsui
>> >
>> > On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>> > >
>> > > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
>> > > >
>> > > >
>> > > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
>> > > > > This patch optimizes the performance of the is_fundamental trait by
>> > > > > dispatching to the new __is_arithmetic built-in trait.
>> > > > >
>> > > > > libstdc++-v3/ChangeLog:
>> > > > >
>> > > > >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
>> > > > >       built-in trait.
>> > > > >       (is_fundamental): Likewise. Optimize the original implementation.
>> > > > >
>> > > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
>> > > > > ---
>> > > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
>> > > > >   1 file changed, 17 insertions(+), 4 deletions(-)
>> > > > >
>> > > > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
>> > > > > index 7ebbe04c77b..cf24de2fcac 100644
>> > > > > --- a/libstdc++-v3/include/std/type_traits
>> > > > > +++ b/libstdc++-v3/include/std/type_traits
>> > > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> > > > >   #endif
>> > > > >
>> > > > >     /// is_fundamental
>> > > > > +#if __has_builtin(__is_arithmetic)
>> > > > > +  template<typename _Tp>
>> > > > > +    struct is_fundamental
>> > > > > +    : public __bool_constant<__is_arithmetic(_Tp)
>> > > > > +                             || is_void<_Tp>::value
>> > > > > +                             || is_null_pointer<_Tp>::value>
>> > > > > +    { };
>> > > >
>> > > > What about doing this ?
>> > > >
>> > > >    template<typename _Tp>
>> > > >      struct is_fundamental
>> > > >      : public __bool_constant<__is_arithmetic(_Tp)
>> > > >                               || __or_<is_void<_Tp>,
>> > > >                                       is_null_pointer<_Tp>>::value>
>> > > >      { };
>> > > >
>> > > > Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
>> > > >
>> > > Let me take a benchmark for this later.
>>
  
Ken Matsui Aug. 31, 2023, 1:57 p.m. UTC | #10
On Tue, Aug 8, 2023 at 1:19 PM Jonathan Wakely <jwakely@redhat.com> wrote:
>
>
>
> On Tue, 18 Jul 2023 at 07:25, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
>>
>> Hi,
>>
>> I took a benchmark for this.
>>
>> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
>>
>> template<typename _Tp>
>> struct is_fundamental
>> : public std::bool_constant<__is_arithmetic(_Tp)
>>                             || std::is_void<_Tp>::value
>>                             || std::is_null_pointer<_Tp>::value>
>> { };
>>
>> is faster than:
>>
>> template<typename _Tp>
>> struct is_fundamental
>> : public std::bool_constant<__is_arithmetic(_Tp)
>>                             || std::disjunction<std::is_void<_Tp>,
>>                                                 std::is_null_pointer<_Tp>
>>                                                 >::value>
>> { };
>>
>> Time: -32.2871%
>> Peak Memory: -18.5071%
>> Total Memory: -20.1991%
>
>
> But what about the fallback implementation of is_fundamental where we don't have the __is_arithmetic built-in?

That fallback implementation would be this:
https://github.com/ken-matsui/gsoc23/blob/967e20770599f2a8925c9794669111faef11beb7/is_fundamental.cc#L11-L15.

The is_fundamental-disjunction.cc benchmark used the USE_BUILTIN
macro, but in this benchmark, I used it to just switch two different
implementations that use the __is_arithmetic built-in.

> -    : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
> -                  is_null_pointer<_Tp>>::type
> +    : public __bool_constant<is_arithmetic<_Tp>::value
> +                             || is_void<_Tp>::value
> +                             || is_null_pointer<_Tp>::value>
>
> Here the use of __or_ means that for is_fundamental<int> we don't instantiate is_void<int> and is_null_pointer<int>. Isn't that still worthwhile?
>
Let me take a benchmark with __or_ later! We may see a difference.

>
>
>
>>
>>
>> Sincerely,
>> Ken Matsui
>>
>> On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>> >
>> > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
>> > >
>> > >
>> > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
>> > > > This patch optimizes the performance of the is_fundamental trait by
>> > > > dispatching to the new __is_arithmetic built-in trait.
>> > > >
>> > > > libstdc++-v3/ChangeLog:
>> > > >
>> > > >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
>> > > >       built-in trait.
>> > > >       (is_fundamental): Likewise. Optimize the original implementation.
>> > > >
>> > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
>> > > > ---
>> > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
>> > > >   1 file changed, 17 insertions(+), 4 deletions(-)
>> > > >
>> > > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
>> > > > index 7ebbe04c77b..cf24de2fcac 100644
>> > > > --- a/libstdc++-v3/include/std/type_traits
>> > > > +++ b/libstdc++-v3/include/std/type_traits
>> > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> > > >   #endif
>> > > >
>> > > >     /// is_fundamental
>> > > > +#if __has_builtin(__is_arithmetic)
>> > > > +  template<typename _Tp>
>> > > > +    struct is_fundamental
>> > > > +    : public __bool_constant<__is_arithmetic(_Tp)
>> > > > +                             || is_void<_Tp>::value
>> > > > +                             || is_null_pointer<_Tp>::value>
>> > > > +    { };
>> > >
>> > > What about doing this ?
>> > >
>> > >    template<typename _Tp>
>> > >      struct is_fundamental
>> > >      : public __bool_constant<__is_arithmetic(_Tp)
>> > >                               || __or_<is_void<_Tp>,
>> > >                                       is_null_pointer<_Tp>>::value>
>> > >      { };
>> > >
>> > > Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
>> > >
>> > Let me take a benchmark for this later.
>>
  
Ken Matsui Aug. 31, 2023, 3:01 p.m. UTC | #11
On Thu, Aug 31, 2023 at 6:57 AM Ken Matsui <kmatsui@cs.washington.edu> wrote:
>
> On Tue, Aug 8, 2023 at 1:19 PM Jonathan Wakely <jwakely@redhat.com> wrote:
> >
> >
> >
> > On Tue, 18 Jul 2023 at 07:25, Ken Matsui via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
> >>
> >> Hi,
> >>
> >> I took a benchmark for this.
> >>
> >> https://github.com/ken-matsui/gcc-benches/blob/main/is_fundamental-disjunction.md#mon-jul-17-105937-pm-pdt-2023
> >>
> >> template<typename _Tp>
> >> struct is_fundamental
> >> : public std::bool_constant<__is_arithmetic(_Tp)
> >>                             || std::is_void<_Tp>::value
> >>                             || std::is_null_pointer<_Tp>::value>
> >> { };
> >>
> >> is faster than:
> >>
> >> template<typename _Tp>
> >> struct is_fundamental
> >> : public std::bool_constant<__is_arithmetic(_Tp)
> >>                             || std::disjunction<std::is_void<_Tp>,
> >>                                                 std::is_null_pointer<_Tp>
> >>                                                 >::value>
> >> { };
> >>
> >> Time: -32.2871%
> >> Peak Memory: -18.5071%
> >> Total Memory: -20.1991%
> >
> >
> > But what about the fallback implementation of is_fundamental where we don't have the __is_arithmetic built-in?
>
> That fallback implementation would be this:
> https://github.com/ken-matsui/gsoc23/blob/967e20770599f2a8925c9794669111faef11beb7/is_fundamental.cc#L11-L15.
>
> The is_fundamental-disjunction.cc benchmark used the USE_BUILTIN
> macro, but in this benchmark, I used it to just switch two different
> implementations that use the __is_arithmetic built-in.
>
> > -    : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
> > -                  is_null_pointer<_Tp>>::type
> > +    : public __bool_constant<is_arithmetic<_Tp>::value
> > +                             || is_void<_Tp>::value
> > +                             || is_null_pointer<_Tp>::value>
> >
> > Here the use of __or_ means that for is_fundamental<int> we don't instantiate is_void<int> and is_null_pointer<int>. Isn't that still worthwhile?
> >
> Let me take a benchmark with __or_ later! We may see a difference.
>
Here is the benchmark result with __or_:

https://github.com/ken-matsui/gsoc23/blob/main/is_fundamental-disjunction.md#thu-aug-31-075127-am-pdt-2023

Time: -23.3935%
Peak Memory: -10.2915%
Total Memory: -14.4165%

Considering the following was with disjunction, __or_ is faster than
disjunction, but still just || seems much faster.

Time: -32.2871%
Peak Memory: -18.5071%
Total Memory: -20.1991%

> >
> >
> >
> >>
> >>
> >> Sincerely,
> >> Ken Matsui
> >>
> >> On Sun, Jul 16, 2023 at 9:49 PM Ken Matsui <kmatsui@cs.washington.edu> wrote:
> >> >
> >> > On Sun, Jul 16, 2023 at 5:41 AM François Dumont <frs.dumont@gmail.com> wrote:
> >> > >
> >> > >
> >> > > On 15/07/2023 06:55, Ken Matsui via Libstdc++ wrote:
> >> > > > This patch optimizes the performance of the is_fundamental trait by
> >> > > > dispatching to the new __is_arithmetic built-in trait.
> >> > > >
> >> > > > libstdc++-v3/ChangeLog:
> >> > > >
> >> > > >       * include/std/type_traits (is_fundamental_v): Use __is_arithmetic
> >> > > >       built-in trait.
> >> > > >       (is_fundamental): Likewise. Optimize the original implementation.
> >> > > >
> >> > > > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> >> > > > ---
> >> > > >   libstdc++-v3/include/std/type_traits | 21 +++++++++++++++++----
> >> > > >   1 file changed, 17 insertions(+), 4 deletions(-)
> >> > > >
> >> > > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
> >> > > > index 7ebbe04c77b..cf24de2fcac 100644
> >> > > > --- a/libstdc++-v3/include/std/type_traits
> >> > > > +++ b/libstdc++-v3/include/std/type_traits
> >> > > > @@ -668,11 +668,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >> > > >   #endif
> >> > > >
> >> > > >     /// is_fundamental
> >> > > > +#if __has_builtin(__is_arithmetic)
> >> > > > +  template<typename _Tp>
> >> > > > +    struct is_fundamental
> >> > > > +    : public __bool_constant<__is_arithmetic(_Tp)
> >> > > > +                             || is_void<_Tp>::value
> >> > > > +                             || is_null_pointer<_Tp>::value>
> >> > > > +    { };
> >> > >
> >> > > What about doing this ?
> >> > >
> >> > >    template<typename _Tp>
> >> > >      struct is_fundamental
> >> > >      : public __bool_constant<__is_arithmetic(_Tp)
> >> > >                               || __or_<is_void<_Tp>,
> >> > >                                       is_null_pointer<_Tp>>::value>
> >> > >      { };
> >> > >
> >> > > Based on your benches it seems that builtin __is_arithmetic is much better that std::is_arithmetic. But __or_ could still avoid instantiation of is_null_pointer.
> >> > >
> >> > Let me take a benchmark for this later.
> >>
  

Patch

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 7ebbe04c77b..cf24de2fcac 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -668,11 +668,21 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 #endif
 
   /// is_fundamental
+#if __has_builtin(__is_arithmetic)
+  template<typename _Tp>
+    struct is_fundamental
+    : public __bool_constant<__is_arithmetic(_Tp)
+                             || is_void<_Tp>::value
+                             || is_null_pointer<_Tp>::value>
+    { };
+#else
   template<typename _Tp>
     struct is_fundamental
-    : public __or_<is_arithmetic<_Tp>, is_void<_Tp>,
-		   is_null_pointer<_Tp>>::type
+    : public __bool_constant<is_arithmetic<_Tp>::value
+                             || is_void<_Tp>::value
+                             || is_null_pointer<_Tp>::value>
     { };
+#endif
 
   /// is_object
   template<typename _Tp>
@@ -3209,13 +3219,16 @@  template <typename _Tp>
 #if __has_builtin(__is_arithmetic)
 template <typename _Tp>
   inline constexpr bool is_arithmetic_v = __is_arithmetic(_Tp);
+template <typename _Tp>
+  inline constexpr bool is_fundamental_v
+    = __is_arithmetic(_Tp) || is_void_v<_Tp> || is_null_pointer_v<_Tp>;
 #else
 template <typename _Tp>
   inline constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
-#endif
-
 template <typename _Tp>
   inline constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
+#endif
+
 template <typename _Tp>
   inline constexpr bool is_object_v = is_object<_Tp>::value;
 template <typename _Tp>