Tested powerpc64le-linux, pushed to trunk. -- >8 --
We only use the __is_referenceable helper in three places now: add_pointer, add_lvalue_reference, and add_rvalue_reference. But lots of other traits depend on add_[lr]value_reference, and decay depends on add_pointer, so removing the instantiation of __is_referenceable helps compile all those other traits slightly faster. We can just use void_t<T&> to check for a referenceable type in the add_[lr]value_reference traits. Then we can specialize add_pointer for reference types, so that we don't need to use remove_reference, and then use void_t<T*> for all non-reference types to detect when we can form a pointer to the type. libstdc++-v3/ChangeLog: * include/std/type_traits (__is_referenceable): Remove. (__add_lvalue_reference_helper, __add_rvalue_reference_helper): Use __void_t instead of __is_referenceable. (__add_pointer_helper): Likewise. (add_pointer): Add partial specializations for reference types. --- libstdc++-v3/include/std/type_traits | 37 ++++++++++++---------------- 1 file changed, 16 insertions(+), 21 deletions(-) diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 3041ac3c941..8b11f31741b 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -712,18 +712,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // __void_t (std::void_t for C++11) template<typename...> using __void_t = void; - - // Utility to detect referenceable types ([defns.referenceable]). - - template<typename _Tp, typename = void> - struct __is_referenceable - : public false_type - { }; - - template<typename _Tp> - struct __is_referenceable<_Tp, __void_t<_Tp&>> - : public true_type - { }; /// @endcond // Type properties. @@ -1024,12 +1012,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION }; /// @cond undocumented - template<typename _Tp, bool = __is_referenceable<_Tp>::value> + template<typename _Tp, typename = void> struct __add_lvalue_reference_helper { using type = _Tp; }; template<typename _Tp> - struct __add_lvalue_reference_helper<_Tp, true> + struct __add_lvalue_reference_helper<_Tp, __void_t<_Tp&>> { using type = _Tp&; }; template<typename _Tp> @@ -1046,12 +1034,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION }; /// @cond undocumented - template<typename _Tp, bool = __is_referenceable<_Tp>::value> + template<typename _Tp, typename = void> struct __add_rvalue_reference_helper { using type = _Tp; }; template<typename _Tp> - struct __add_rvalue_reference_helper<_Tp, true> + struct __add_rvalue_reference_helper<_Tp, __void_t<_Tp&&>> { using type = _Tp&&; }; template<typename _Tp> @@ -1971,14 +1959,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : public __remove_pointer_helper<_Tp, __remove_cv_t<_Tp>> { }; - template<typename _Tp, bool = __or_<__is_referenceable<_Tp>, - is_void<_Tp>>::value> + template<typename _Tp, typename = void> struct __add_pointer_helper - { typedef _Tp type; }; + { using type = _Tp; }; template<typename _Tp> - struct __add_pointer_helper<_Tp, true> - { typedef typename remove_reference<_Tp>::type* type; }; + struct __add_pointer_helper<_Tp, __void_t<_Tp*>> + { using type = _Tp*; }; /// add_pointer template<typename _Tp> @@ -1986,6 +1973,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : public __add_pointer_helper<_Tp> { }; + template<typename _Tp> + struct add_pointer<_Tp&> + { using type = _Tp*; }; + + template<typename _Tp> + struct add_pointer<_Tp&&> + { using type = _Tp*; }; + #if __cplusplus > 201103L /// Alias template for remove_pointer template<typename _Tp> -- 2.37.2