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[libc++] mdspan - implement layout_stride (llvm#69650)
This implements layout_stride for C++23 and with that completes the implementation of the C++23 mdspan header. The feature test macro is added, and the status pages updated. Co-authored-by: Damien L-G <[email protected]> Differential Revision: https://reviews.llvm.org/D157171
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‎libcxx/docs/FeatureTestMacroTable.rst

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@@ -332,7 +332,7 @@ Status
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--------------------------------------------------- -----------------
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``__cpp_lib_is_scoped_enum`` ``202011L``
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--------------------------------------------------- -----------------
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``__cpp_lib_mdspan`` *unimplemented*
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``__cpp_lib_mdspan`` ``202207L``
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--------------------------------------------------- -----------------
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``__cpp_lib_move_only_function`` *unimplemented*
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--------------------------------------------------- -----------------

‎libcxx/docs/Status/Cxx23.rst

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@@ -40,7 +40,6 @@ Paper Status
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.. note::
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.. [#note-P0009R18] P0009R18: ``extents``, ``dextents``, ``layout_left``, ``layout_right``, and ``default_accessor`` are implemented.
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.. [#note-P0533R9] P0533R9: ``isfinite``, ``isinf``, ``isnan`` and ``isnormal`` are implemented.
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.. [#note-P1413R3] P1413R3: ``std::aligned_storage_t`` and ``std::aligned_union_t`` are marked deprecated, but
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clang doesn't issue a diagnostic for deprecated using template declarations.

‎libcxx/docs/Status/Cxx23Papers.csv

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@@ -51,7 +51,7 @@
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"`P2442R1 <https://wg21.link/P2442R1>`__","LWG","Windowing range adaptors: ``views::chunk`` and ``views::slide``","February 2022","","","|ranges|"
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"`P2443R1 <https://wg21.link/P2443R1>`__","LWG","``views::chunk_by``","February 2022","|Complete|","18.0","|ranges|"
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"","","","","","",""
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"`P0009R18 <https://wg21.link/P0009R18>`__","LWG","mdspan: A Non-Owning Multidimensional Array Reference","July 2022","|In progress| [#note-P0009R18]_",""
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"`P0009R18 <https://wg21.link/P0009R18>`__","LWG","mdspan: A Non-Owning Multidimensional Array Reference","July 2022","|Complete|","18.0"
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"`P0429R9 <https://wg21.link/P0429R9>`__","LWG","A Standard ``flat_map``","July 2022","",""
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"`P1169R4 <https://wg21.link/P1169R4>`__","LWG","``static operator()``","July 2022","|Complete|","16.0"
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"`P1222R4 <https://wg21.link/P1222R4>`__","LWG","A Standard ``flat_set``","July 2022","",""
@@ -89,9 +89,9 @@
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"`P2549R1 <https://wg21.link/P2549R1>`__","LWG","``std::unexpected`` should have ``error()`` as member accessor","July 2022","|Complete|","16.0"
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"`P2585R0 <https://wg21.link/P2585R0>`__","LWG","Improving default container formatting","July 2022","|Complete|","17.0"
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"`P2590R2 <https://wg21.link/P2590R2>`__","LWG","Explicit lifetime management","July 2022","",""
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"`P2599R2 <https://wg21.link/P2599R2>`__","LWG","``mdspan::size_type`` should be ``index_type``","July 2022","",""
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"`P2604R0 <https://wg21.link/P2604R0>`__","LWG","mdspan: rename pointer and contiguous","July 2022","",""
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"`P2613R1 <https://wg21.link/P2613R1>`__","LWG","Add the missing ``empty`` to ``mdspan``","July 2022","",""
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"`P2599R2 <https://wg21.link/P2599R2>`__","LWG","``mdspan::size_type`` should be ``index_type``","July 2022","|Complete|","18.0"
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"`P2604R0 <https://wg21.link/P2604R0>`__","LWG","mdspan: rename pointer and contiguous","July 2022","|Complete|","18.0"
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"`P2613R1 <https://wg21.link/P2613R1>`__","LWG","Add the missing ``empty`` to ``mdspan``","July 2022","|Complete|","18.0"
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"","","","","","",""
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"`P1202R5 <https://wg21.link/P1202R5>`__","LWG", "Asymmetric Fences", "November 2022","","","|concurrency TS|"
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"`P1264R2 <https://wg21.link/P1264R2>`__","LWG", "Revising the wording of ``stream`` input operations", "November 2022","|Complete|","9.0",""

‎libcxx/include/CMakeLists.txt

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@@ -508,6 +508,7 @@ set(files
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__mdspan/extents.h
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__mdspan/layout_left.h
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__mdspan/layout_right.h
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__mdspan/layout_stride.h
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__mdspan/mdspan.h
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__memory/addressof.h
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__memory/align.h

‎libcxx/include/__fwd/mdspan.h

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@@ -42,14 +42,11 @@ struct layout_right {
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class mapping;
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};
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/*
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// Will be implemented with follow on revision
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// Layout policy with a unique mapping where strides are arbitrary
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struct layout_stride {
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template<class Extents>
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class mapping;
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template <class _Extents>
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class mapping;
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};
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*/
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#endif // _LIBCPP_STD_VER >= 23
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‎libcxx/include/__mdspan/layout_left.h

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@@ -110,12 +110,27 @@ class layout_left::mapping {
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"layout_left::mapping converting ctor: other.required_span_size() must be representable as index_type.");
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}
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// FIXME: add when we add other layouts
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# if 0
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template<class _OtherExtents>
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constexpr explicit(extents_type::rank() > 0)
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mapping(const layout_stride::mapping_<OtherExtents>&) noexcept;
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# endif
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template <class _OtherExtents>
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requires(is_constructible_v<extents_type, _OtherExtents>)
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_LIBCPP_HIDE_FROM_ABI constexpr explicit(extents_type::rank() > 0)
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mapping(const layout_stride::mapping<_OtherExtents>& __other) noexcept
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: __extents_(__other.extents()) {
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if constexpr (extents_type::rank() > 0) {
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_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
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([&]() {
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using _CommonType = common_type_t<typename extents_type::index_type, typename _OtherExtents::index_type>;
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for (rank_type __r = 0; __r < extents_type::rank(); __r++)
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if (static_cast<_CommonType>(stride(__r)) != static_cast<_CommonType>(__other.stride(__r)))
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return false;
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return true;
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}()),
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"layout_left::mapping from layout_stride ctor: strides are not compatible with layout_left.");
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_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
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__mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
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"layout_left::mapping from layout_stride ctor: other.required_span_size() must be representable as "
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"index_type.");
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}
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}
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_LIBCPP_HIDE_FROM_ABI constexpr mapping& operator=(const mapping&) noexcept = default;
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‎libcxx/include/__mdspan/layout_right.h

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@@ -109,12 +109,27 @@ class layout_right::mapping {
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"layout_right::mapping converting ctor: other.required_span_size() must be representable as index_type.");
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}
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// FIXME: add when we add other layouts
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# if 0
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template<class _OtherExtents>
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constexpr explicit(extents_type::rank() > 0)
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mapping(const layout_stride::mapping_<OtherExtents>&) noexcept;
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# endif
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template <class _OtherExtents>
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requires(is_constructible_v<extents_type, _OtherExtents>)
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_LIBCPP_HIDE_FROM_ABI constexpr explicit(extents_type::rank() > 0)
115+
mapping(const layout_stride::mapping<_OtherExtents>& __other) noexcept
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: __extents_(__other.extents()) {
117+
if constexpr (extents_type::rank() > 0) {
118+
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
119+
([&]() {
120+
using _CommonType = common_type_t<typename extents_type::index_type, typename _OtherExtents::index_type>;
121+
for (rank_type __r = 0; __r < extents_type::rank(); __r++)
122+
if (static_cast<_CommonType>(stride(__r)) != static_cast<_CommonType>(__other.stride(__r)))
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return false;
124+
return true;
125+
}()),
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"layout_right::mapping from layout_stride ctor: strides are not compatible with layout_right.");
127+
_LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
128+
__mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()),
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"layout_right::mapping from layout_stride ctor: other.required_span_size() must be representable as "
130+
"index_type.");
131+
}
132+
}
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_LIBCPP_HIDE_FROM_ABI constexpr mapping& operator=(const mapping&) noexcept = default;
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