Message ID | 20231024020424.699427-26-kmatsui@gcc.gnu.org |
---|---|
State | New |
Headers | show |
Series | Optimize type traits compilation performance | expand |
On Tue, 24 Oct 2023 at 03:16, Ken Matsui <kmatsui@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.
On Tue, Oct 24, 2023 at 4:02 AM Jonathan Wakely <jwakely@redhat.com> wrote: > > > > On Tue, 24 Oct 2023 at 03:16, Ken Matsui <kmatsui@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.
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 36ad9814047..1e561c8ea38 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -637,6 +637,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { }; /// is_function +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function) + template<typename _Tp> + struct is_function + : public __bool_constant<__is_function(_Tp)> + { }; +#else template<typename _Tp> struct is_function : public __bool_constant<!is_const<const _Tp>::value> { }; @@ -648,6 +654,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Tp> struct is_function<_Tp&&> : public false_type { }; +#endif #ifdef __cpp_lib_is_null_pointer // C++ >= 11 /// is_null_pointer (LWG 2247). @@ -3269,8 +3276,28 @@ template <typename _Tp> inline constexpr bool is_union_v = __is_union(_Tp); template <typename _Tp> inline constexpr bool is_class_v = __is_class(_Tp); + +#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_function_v = is_function<_Tp>::value; + inline constexpr bool is_const_v<const _Tp> = true; +#endif + +#if _GLIBCXX_USE_BUILTIN_TRAIT(__is_function) +template <typename _Tp> + inline constexpr bool is_function_v = __is_function(_Tp); +#else +template <typename _Tp> + inline constexpr bool is_function_v = !is_const_v<const _Tp>; +template <typename _Tp> + inline constexpr bool is_function_v<_Tp&> = false; +template <typename _Tp> + inline constexpr bool is_function_v<_Tp&&> = false; +#endif #if _GLIBCXX_USE_BUILTIN_TRAIT(__is_reference) template <typename _Tp> @@ -3303,16 +3330,6 @@ 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_volatile) template <typename _Tp> inline constexpr bool is_volatile_v = __is_volatile(_Tp);
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. Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org> --- libstdc++-v3/include/std/type_traits | 39 ++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 11 deletions(-)