[PATCH v20 05/40] libstdc++: Optimize is_const trait performance
Ken Matsui
kmatsui@gcc.gnu.org
Mon Oct 16 00:09:49 GMT 2023
This patch optimizes the performance of the is_const trait 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 <kmatsui@gcc.gnu.org>
---
libstdc++-v3/include/std/type_traits | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 677cd934b94..686e38e47c3 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -784,6 +784,12 @@ _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 { };
@@ -791,6 +797,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
struct is_const<_Tp const>
: public true_type { };
+#endif
/// is_volatile
template<typename>
@@ -3218,10 +3225,17 @@ template <typename _Tp>
inline constexpr bool is_compound_v = is_compound<_Tp>::value;
template <typename _Tp>
inline constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
+
+#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
+
template <typename _Tp>
inline constexpr bool is_volatile_v = false;
template <typename _Tp>
--
2.42.0
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