Tested powerpc64le-linux, pushed to trunk. -- >8 --
We can replace some class template helpers with alias templates, which are cheaper to instantiate. For example, replace the __is_copy_constructible_impl class template with an alias template that uses just evaluates the __is_constructible built-in, using add_lvalue_reference<const T> to get the argument type in a way that works for non-referenceable types. For a given specialization of is_copy_constructible this results in the same number of class templates being instantiated (for the common case of non-void, non-function types), but the add_lvalue_reference instantiations are not specific to the is_copy_constructible specialization and so can be reused by other traits. Previously __is_copy_constructible_impl was a distinct class template and its specializations were never used for anything except is_copy_constructible. With the new definitions of these traits that don't depend on helper classes, it becomes more practical to optimize the is_xxx_constructible_v variable templates to avoid instantiations. Previously doing so would have meant two entirely separate implementation strategies for these traits. libstdc++-v3/ChangeLog: * include/std/type_traits (__is_constructible_impl): Replace class template with alias template. (is_default_constructible, is_nothrow_constructible) (is_nothrow_constructible): Simplify base-specifier. (__is_copy_constructible_impl, __is_move_constructible_impl) (__is_nothrow_copy_constructible_impl) (__is_nothrow_move_constructible_impl): Remove class templates. (is_copy_constructible, is_move_constructible) (is_nothrow_constructible, is_nothrow_default_constructible) (is_nothrow_copy_constructible, is_nothrow_move_constructible): Adjust base-specifiers to use __is_constructible_impl. (__is_copy_assignable_impl, __is_move_assignable_impl) (__is_nt_copy_assignable_impl, __is_nt_move_assignable_impl): Remove class templates. (__is_assignable_impl): New alias template. (is_assignable, is_copy_assignable, is_move_assignable): Adjust base-specifiers to use new alias template. (is_nothrow_copy_assignable, is_nothrow_move_assignable): Adjust base-specifiers to use existing alias template. (__is_trivially_constructible_impl): New alias template. (is_trivially_constructible, is_trivially_default_constructible) (is_trivially_copy_constructible) (is_trivially_move_constructible): Adjust base-specifiers to use new alias template. (__is_trivially_assignable_impl): New alias template. (is_trivially_assignable, is_trivially_copy_assignable) (is_trivially_move_assignable): Adjust base-specifier to use new alias template. (__add_lval_ref_t, __add_rval_ref_t): New alias templates. (add_lvalue_reference, add_rvalue_reference): Use new alias templates. --- libstdc++-v3/include/std/type_traits | 249 +++++++-------------------- 1 file changed, 62 insertions(+), 187 deletions(-) diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 639c351df8a..3041ac3c941 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -1001,9 +1001,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// @cond undocumented template<typename _Tp, typename... _Args> - struct __is_constructible_impl - : public __bool_constant<__is_constructible(_Tp, _Args...)> - { }; + using __is_constructible_impl + = __bool_constant<__is_constructible(_Tp, _Args...)>; /// @endcond /// is_constructible @@ -1018,7 +1017,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// is_default_constructible template<typename _Tp> struct is_default_constructible - : public __is_constructible_impl<_Tp>::type + : public __is_constructible_impl<_Tp> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1026,22 +1025,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// @cond undocumented template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_copy_constructible_impl; + struct __add_lvalue_reference_helper + { using type = _Tp; }; template<typename _Tp> - struct __is_copy_constructible_impl<_Tp, false> - : public false_type { }; + struct __add_lvalue_reference_helper<_Tp, true> + { using type = _Tp&; }; template<typename _Tp> - struct __is_copy_constructible_impl<_Tp, true> - : public __is_constructible_impl<_Tp, const _Tp&> - { }; + using __add_lval_ref_t = typename __add_lvalue_reference_helper<_Tp>::type; /// @endcond /// is_copy_constructible template<typename _Tp> struct is_copy_constructible - : public __is_copy_constructible_impl<_Tp> + : public __is_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1049,22 +1047,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// @cond undocumented template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_move_constructible_impl; + struct __add_rvalue_reference_helper + { using type = _Tp; }; template<typename _Tp> - struct __is_move_constructible_impl<_Tp, false> - : public false_type { }; + struct __add_rvalue_reference_helper<_Tp, true> + { using type = _Tp&&; }; template<typename _Tp> - struct __is_move_constructible_impl<_Tp, true> - : public __is_constructible_impl<_Tp, _Tp&&> - { }; + using __add_rval_ref_t = typename __add_rvalue_reference_helper<_Tp>::type; /// @endcond /// is_move_constructible template<typename _Tp> struct is_move_constructible - : public __is_move_constructible_impl<_Tp> + : public __is_constructible_impl<_Tp, __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1079,7 +1076,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// is_nothrow_constructible template<typename _Tp, typename... _Args> struct is_nothrow_constructible - : public __is_nothrow_constructible_impl<_Tp, _Args...>::type + : public __is_nothrow_constructible_impl<_Tp, _Args...> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1088,112 +1085,68 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// is_nothrow_default_constructible template<typename _Tp> struct is_nothrow_default_constructible - : public __bool_constant<__is_nothrow_constructible(_Tp)> + : public __is_nothrow_constructible_impl<_Tp> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - /// @cond undocumented - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_nothrow_copy_constructible_impl; - - template<typename _Tp> - struct __is_nothrow_copy_constructible_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_nothrow_copy_constructible_impl<_Tp, true> - : public __is_nothrow_constructible_impl<_Tp, const _Tp&> - { }; - /// @endcond - /// is_nothrow_copy_constructible template<typename _Tp> struct is_nothrow_copy_constructible - : public __is_nothrow_copy_constructible_impl<_Tp>::type + : public __is_nothrow_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>> + { + static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), + "template argument must be a complete class or an unbounded array"); + }; + + /// is_nothrow_move_constructible + template<typename _Tp> + struct is_nothrow_move_constructible + : public __is_nothrow_constructible_impl<_Tp, __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; /// @cond undocumented - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_nothrow_move_constructible_impl; - - template<typename _Tp> - struct __is_nothrow_move_constructible_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_nothrow_move_constructible_impl<_Tp, true> - : public __is_nothrow_constructible_impl<_Tp, _Tp&&> - { }; + template<typename _Tp, typename _Up> + using __is_assignable_impl = __bool_constant<__is_assignable(_Tp, _Up)>; /// @endcond - /// is_nothrow_move_constructible - template<typename _Tp> - struct is_nothrow_move_constructible - : public __is_nothrow_move_constructible_impl<_Tp>::type - { - static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), - "template argument must be a complete class or an unbounded array"); - }; - /// is_assignable template<typename _Tp, typename _Up> struct is_assignable - : public __bool_constant<__is_assignable(_Tp, _Up)> + : public __is_assignable_impl<_Tp, _Up> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_copy_assignable_impl; - - template<typename _Tp> - struct __is_copy_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_copy_assignable_impl<_Tp, true> - : public __bool_constant<__is_assignable(_Tp&, const _Tp&)> - { }; - /// is_copy_assignable template<typename _Tp> struct is_copy_assignable - : public __is_copy_assignable_impl<_Tp>::type + : public __is_assignable_impl<__add_lval_ref_t<_Tp>, + __add_lval_ref_t<const _Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_move_assignable_impl; - - template<typename _Tp> - struct __is_move_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_move_assignable_impl<_Tp, true> - : public __bool_constant<__is_assignable(_Tp&, _Tp&&)> - { }; - /// is_move_assignable template<typename _Tp> struct is_move_assignable - : public __is_move_assignable_impl<_Tp>::type + : public __is_assignable_impl<__add_lval_ref_t<_Tp>, __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; + /// @cond undocumented template<typename _Tp, typename _Up> using __is_nothrow_assignable_impl = __bool_constant<__is_nothrow_assignable(_Tp, _Up)>; + /// @endcond /// is_nothrow_assignable template<typename _Tp, typename _Up> @@ -1204,52 +1157,36 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_nt_copy_assignable_impl; - - template<typename _Tp> - struct __is_nt_copy_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_nt_copy_assignable_impl<_Tp, true> - : public __is_nothrow_assignable_impl<_Tp&, const _Tp&> - { }; - /// is_nothrow_copy_assignable template<typename _Tp> struct is_nothrow_copy_assignable - : public __is_nt_copy_assignable_impl<_Tp> + : public __is_nothrow_assignable_impl<__add_lval_ref_t<_Tp>, + __add_lval_ref_t<const _Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_nt_move_assignable_impl; - - template<typename _Tp> - struct __is_nt_move_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_nt_move_assignable_impl<_Tp, true> - : public __is_nothrow_assignable_impl<_Tp&, _Tp&&> - { }; - /// is_nothrow_move_assignable template<typename _Tp> struct is_nothrow_move_assignable - : public __is_nt_move_assignable_impl<_Tp> + : public __is_nothrow_assignable_impl<__add_lval_ref_t<_Tp>, + __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; + /// @cond undocumented + template<typename _Tp, typename... _Args> + using __is_trivially_constructible_impl + = __bool_constant<__is_trivially_constructible(_Tp, _Args...)>; + /// @endcond + /// is_trivially_constructible template<typename _Tp, typename... _Args> struct is_trivially_constructible - : public __bool_constant<__is_trivially_constructible(_Tp, _Args...)> + : public __is_trivially_constructible_impl<_Tp, _Args...> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1258,7 +1195,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// is_trivially_default_constructible template<typename _Tp> struct is_trivially_default_constructible - : public __bool_constant<__is_trivially_constructible(_Tp)> + : public __is_trivially_constructible_impl<_Tp> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1294,98 +1231,54 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __is_implicitly_default_constructible_safe<_Tp>> { }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_trivially_copy_constructible_impl; - - template<typename _Tp> - struct __is_trivially_copy_constructible_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_trivially_copy_constructible_impl<_Tp, true> - : public __and_<__is_copy_constructible_impl<_Tp>, - integral_constant<bool, - __is_trivially_constructible(_Tp, const _Tp&)>> - { }; - /// is_trivially_copy_constructible template<typename _Tp> struct is_trivially_copy_constructible - : public __is_trivially_copy_constructible_impl<_Tp> + : public __is_trivially_constructible_impl<_Tp, __add_lval_ref_t<const _Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_trivially_move_constructible_impl; - - template<typename _Tp> - struct __is_trivially_move_constructible_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_trivially_move_constructible_impl<_Tp, true> - : public __and_<__is_move_constructible_impl<_Tp>, - integral_constant<bool, - __is_trivially_constructible(_Tp, _Tp&&)>> - { }; - /// is_trivially_move_constructible template<typename _Tp> struct is_trivially_move_constructible - : public __is_trivially_move_constructible_impl<_Tp> + : public __is_trivially_constructible_impl<_Tp, __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; + /// @cond undocumented + template<typename _Tp, typename _Up> + using __is_trivially_assignable_impl + = __bool_constant<__is_trivially_assignable(_Tp, _Up)>; + /// @endcond + /// is_trivially_assignable template<typename _Tp, typename _Up> struct is_trivially_assignable - : public __bool_constant<__is_trivially_assignable(_Tp, _Up)> + : public __is_trivially_assignable_impl<_Tp, _Up> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_trivially_copy_assignable_impl; - - template<typename _Tp> - struct __is_trivially_copy_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_trivially_copy_assignable_impl<_Tp, true> - : public __bool_constant<__is_trivially_assignable(_Tp&, const _Tp&)> - { }; - /// is_trivially_copy_assignable template<typename _Tp> struct is_trivially_copy_assignable - : public __is_trivially_copy_assignable_impl<_Tp> + : public __is_trivially_assignable_impl<__add_lval_ref_t<_Tp>, + __add_lval_ref_t<const _Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __is_trivially_move_assignable_impl; - - template<typename _Tp> - struct __is_trivially_move_assignable_impl<_Tp, false> - : public false_type { }; - - template<typename _Tp> - struct __is_trivially_move_assignable_impl<_Tp, true> - : public __bool_constant<__is_trivially_assignable(_Tp&, _Tp&&)> - { }; - /// is_trivially_move_assignable template<typename _Tp> struct is_trivially_move_assignable - : public __is_trivially_move_assignable_impl<_Tp> + : public __is_trivially_assignable_impl<__add_lval_ref_t<_Tp>, + __add_rval_ref_t<_Tp>> { static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}), "template argument must be a complete class or an unbounded array"); @@ -1669,33 +1562,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct remove_reference<_Tp&&> { typedef _Tp type; }; - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __add_lvalue_reference_helper - { typedef _Tp type; }; - - template<typename _Tp> - struct __add_lvalue_reference_helper<_Tp, true> - { typedef _Tp& type; }; - /// add_lvalue_reference template<typename _Tp> struct add_lvalue_reference - : public __add_lvalue_reference_helper<_Tp> - { }; - - template<typename _Tp, bool = __is_referenceable<_Tp>::value> - struct __add_rvalue_reference_helper - { typedef _Tp type; }; - - template<typename _Tp> - struct __add_rvalue_reference_helper<_Tp, true> - { typedef _Tp&& type; }; + { using type = __add_lval_ref_t<_Tp>; }; /// add_rvalue_reference template<typename _Tp> struct add_rvalue_reference - : public __add_rvalue_reference_helper<_Tp> - { }; + { using type = __add_rval_ref_t<_Tp>; }; #if __cplusplus > 201103L /// Alias template for remove_reference -- 2.37.2