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

[Jonathan Wakely]

On 11/05/24 02:01 -0700, Ken Matsui wrote:
>This patch optimizes the compilation performance of std::is_const
>by dispatching to the new __is_const built-in trait.

OK, thanks.

>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
>