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 <kmatsui@gcc.gnu.org>
Reviewed-by: Patrick Palka <ppalka@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
// 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 { };
template<typename _Tp>
struct is_const<_Tp const>
: public true_type { };
+#endif
/// is_volatile
template<typename>
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>