https://gcc.gnu.org/g:eea62ce6fbcffb8acc227e5dbed74d2b627ce84d
commit r15-1245-geea62ce6fbcffb8acc227e5dbed74d2b627ce84d
Author: Ken Matsui <kmat...@gcc.gnu.org>
Date: Tue Mar 21 17:09:34 2023 -0700
libstdc++: Optimize std::is_const compilation performance
This patch optimizes the compilation performance of std::is_const
by dispatching to the new __is_const built-in trait.
libstdc++-v3/ChangeLog:
* include/std/type_traits (is_const): Use __is_const built-in
trait.
(is_const_v): Likewise.
Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
Reviewed-by: Patrick Palka <ppa...@redhat.com>
Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Diff:
---
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 b441bf9908f7..8df0cf3ac3b8 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>
