Implements the remaining parts of layout_left and layout_right; and all of layout_stride.
The implementation of layout_stride::mapping::is_exhaustive applies the following change to the standard: 4266. layout_stride::mapping should treat empty mappings as exhaustive https://cplusplus.github.io/LWG/issue4266 The preconditions for layout_stride(extents, strides) are not checked. libstdc++-v3/ChangeLog: * include/std/mdspan (layout_stride): New class. * src/c++23/std.cc.in: Add layout_stride. Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com> --- libstdc++-v3/include/std/mdspan | 245 ++++++++++++++++++++++++++++++- libstdc++-v3/src/c++23/std.cc.in | 3 +- 2 files changed, 246 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan index 8e406731568..1250adefc14 100644 --- a/libstdc++-v3/include/std/mdspan +++ b/libstdc++-v3/include/std/mdspan @@ -418,6 +418,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION class mapping; }; + struct layout_stride + { + template<typename _Extents> + class mapping; + }; + namespace __mdspan { template<typename _Tp> @@ -511,7 +517,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Mapping> concept __standardized_mapping = __mapping_of<layout_left, _Mapping> - || __mapping_of<layout_right, _Mapping>; + || __mapping_of<layout_right, _Mapping> + || __mapping_of<layout_stride, _Mapping>; // A tag type to create internal ctors. class __internal_ctor @@ -557,6 +564,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : mapping(__other.extents(), __mdspan::__internal_ctor{}) { } + template<typename _OExtents> + requires is_constructible_v<extents_type, _OExtents> + constexpr explicit(extents_type::rank() > 0) + mapping(const layout_stride::mapping<_OExtents>& __other) + : mapping(__other.extents(), __mdspan::__internal_ctor{}) + { __glibcxx_assert(*this == __other); } + constexpr mapping& operator=(const mapping&) noexcept = default; @@ -687,6 +701,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION : mapping(__other.extents(), __mdspan::__internal_ctor{}) { } + template<class _OExtents> + requires is_constructible_v<extents_type, _OExtents> + constexpr explicit(extents_type::rank() > 0) + mapping(const layout_stride::mapping<_OExtents>& __other) noexcept + : mapping(__other.extents(), __mdspan::__internal_ctor{}) + { __glibcxx_assert(*this == __other); } + constexpr mapping& operator=(const mapping&) noexcept = default; @@ -759,6 +780,228 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION [[no_unique_address]] extents_type _M_extents{}; }; + namespace __mdspan + { + template<typename M> + concept __mapping_alike = requires + { + requires __is_extents<typename M::extents_type>; + { M::is_always_strided() } -> same_as<bool>; + { M::is_always_exhaustive() } -> same_as<bool>; + { M::is_always_unique() } -> same_as<bool>; + bool_constant<M::is_always_strided()>::value; + bool_constant<M::is_always_exhaustive()>::value; + bool_constant<M::is_always_unique()>::value; + }; + + template<typename _Mapping> + constexpr typename _Mapping::index_type + __offset(const _Mapping& __m) noexcept + { + using _IndexType = typename _Mapping::index_type; + constexpr auto __rank = _Mapping::extents_type::rank(); + + if constexpr (__standardized_mapping<_Mapping>) + return 0; + else + { + if (__empty(__m.extents())) + return 0; + + auto __impl = [&__m]<size_t... _Counts>(index_sequence<_Counts...>) + { return __m(((void) _Counts, _IndexType(0))...); }; + return __impl(make_index_sequence<__rank>()); + } + } + + template<typename _Mapping, typename... _Indices> + constexpr typename _Mapping::index_type + __linear_index_strides(const _Mapping& __m, _Indices... __indices) + noexcept + { + using _IndexType = typename _Mapping::index_type; + _IndexType __res = 0; + if constexpr (sizeof...(__indices) > 0) + { + auto __update = [&, __pos = 0u](_IndexType __idx) mutable + { + __res += __idx * __m.stride(__pos++); + }; + (__update(__indices), ...); + } + return __res; + } + } + + template<typename _Extents> + class layout_stride::mapping + { + public: + using extents_type = _Extents; + using index_type = typename extents_type::index_type; + using size_type = typename extents_type::size_type; + using rank_type = typename extents_type::rank_type; + using layout_type = layout_stride; + + static_assert(__mdspan::__representable_size<extents_type, index_type>, + "The size of extents_type must be representable as index_type"); + + constexpr + mapping() noexcept + { + // The precondition is either statically asserted, or automatically + // satisfied because dynamic extents are zero-initialzied. + size_t __stride = 1; + for (size_t __i = extents_type::rank(); __i > 0; --__i) + { + _M_strides[__i - 1] = index_type(__stride); + __stride *= size_t(_M_extents.extent(__i - 1)); + } + } + + constexpr + mapping(const mapping&) noexcept = default; + + template<__mdspan::__valid_index_type<index_type> _OIndexType> + constexpr + mapping(const extents_type& __exts, + span<_OIndexType, extents_type::rank()> __strides) noexcept + : _M_extents(__exts) + { + for (size_t __i = 0; __i < extents_type::rank(); ++__i) + _M_strides[__i] = index_type(as_const(__strides[__i])); + } + + template<__mdspan::__valid_index_type<index_type> _OIndexType> + constexpr + mapping(const extents_type& __exts, + const array<_OIndexType, extents_type::rank()>& __strides) + noexcept + : mapping(__exts, + span<const _OIndexType, extents_type::rank()>(__strides)) + { } + + template<__mdspan::__mapping_alike _StridedMapping> + requires (is_constructible_v<extents_type, + typename _StridedMapping::extents_type> + && _StridedMapping::is_always_unique() + && _StridedMapping::is_always_strided()) + constexpr explicit(!( + is_convertible_v<typename _StridedMapping::extents_type, extents_type> + && __mdspan::__standardized_mapping<_StridedMapping>)) + mapping(const _StridedMapping& __other) noexcept + : _M_extents(__other.extents()) + { + __glibcxx_assert(__mdspan::__offset(__other) == 0); + if constexpr (cmp_greater( + numeric_limits<typename _StridedMapping::index_type>::max(), + numeric_limits<index_type>::max())) + __glibcxx_assert(!cmp_less(numeric_limits<index_type>::max(), + __other.required_span_size()) + && "other.required_span_size() must be representable" + " as index_type"); + if constexpr (extents_type::rank() > 0) + for (size_t __i = 0; __i < extents_type::rank(); ++__i) + _M_strides[__i] = index_type(__other.stride(__i)); + } + + constexpr mapping& + operator=(const mapping&) noexcept = default; + + constexpr const extents_type& + extents() const noexcept { return _M_extents; } + + constexpr array<index_type, extents_type::rank()> + strides() const noexcept + { + array<index_type, extents_type::rank()> __ret; + for (size_t __i = 0; __i < extents_type::rank(); ++__i) + __ret[__i] = _M_strides[__i]; + return __ret; + } + + constexpr index_type + required_span_size() const noexcept + { + if (__mdspan::__empty(_M_extents)) + return 0; + + index_type __ret = 1; + for (size_t __i = 0; __i < extents_type::rank(); ++__i) + __ret += (_M_extents.extent(__i) - 1) * _M_strides[__i]; + return __ret; + } + + template<__mdspan::__valid_index_type<index_type>... _Indices> + requires (sizeof...(_Indices) == extents_type::rank()) + constexpr index_type + operator()(_Indices... __indices) const noexcept + { + return __mdspan::__linear_index_strides(*this, + static_cast<index_type>(__indices)...); + } + + static constexpr bool + is_always_unique() noexcept { return true; } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 4266. layout_stride::mapping should treat empty mappings as exhaustive + static constexpr bool + is_always_exhaustive() noexcept + { + return (_Extents::rank() == 0) || __mdspan::__contains_zero( + __mdspan::__static_extents<extents_type>()); + } + + static constexpr bool + is_always_strided() noexcept { return true; } + + static constexpr bool + is_unique() noexcept { return true; } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 4266. layout_stride::mapping should treat empty mappings as exhaustive + constexpr bool + is_exhaustive() const noexcept + { + if constexpr (!is_always_exhaustive()) + { + constexpr auto __rank = extents_type::rank(); + auto __size = __mdspan::__fwd_prod(_M_extents, __rank); + if(__size > 0) + return __size == required_span_size(); + } + return true; + } + + static constexpr bool + is_strided() noexcept { return true; } + + constexpr index_type + stride(rank_type __r) const noexcept { return _M_strides[__r]; } + + template<__mdspan::__mapping_alike _OMapping> + requires ((extents_type::rank() == _OMapping::extents_type::rank()) + && _OMapping::is_always_strided()) + friend constexpr bool + operator==(const mapping& __self, const _OMapping& __other) noexcept + { + if (__self.extents() != __other.extents()) + return false; + if constexpr (extents_type::rank() > 0) + for (size_t __i = 0; __i < extents_type::rank(); ++__i) + if (!cmp_equal(__self.stride(__i), __other.stride(__i))) + return false; + return __mdspan::__offset(__other) == 0; + } + + private: + using _S_strides_t = typename __array_traits<index_type, + extents_type::rank()>::_Type; + [[no_unique_address]] extents_type _M_extents; + [[no_unique_address]] _S_strides_t _M_strides; + }; + _GLIBCXX_END_NAMESPACE_VERSION } #endif diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in index fe1407d71da..9a52a7e7728 100644 --- a/libstdc++-v3/src/c++23/std.cc.in +++ b/libstdc++-v3/src/c++23/std.cc.in @@ -1846,7 +1846,8 @@ export namespace std using std::extents; using std::layout_left; using std::layout_right; - // FIXME layout_*, default_accessor and mdspan + using std::layout_stride; + // FIXME layout_left_padded, layout_right_padded, default_accessor and mdspan } #endif -- 2.49.0
