On Tue, Sep 23, 2025 at 3:41 PM Luc Grosheintz <[email protected]> wrote:
> This commit adds the right padded layout as described in N5014, with > LWG4372 (dynamic padding value) and LWG4314 (move in operator()). > > libstdc++-v3/ChangeLog: > > * include/std/mdspan (_RightPaddedIndices): New class. > (layout_right_padded): New class. > * src/c++23/std.cc.in (layout_right_padded): Add. > * testsuite/23_containers/mdspan/layouts/ctors.cc: Update > test for right padded layout. > * testsuite/23_containers/mdspan/layouts/empty.cc: Ditto. > * testsuite/23_containers/mdspan/layouts/mapping.cc: Ditto. > * testsuite/23_containers/mdspan/layouts/padded.cc: Ditto. > * testsuite/23_containers/mdspan/layouts/padded_neg.cc: Ditto. > * testsuite/23_containers/mdspan/layouts/padded_traits.h: Ditto. > > Signed-off-by: Luc Grosheintz <[email protected]> > --- > Suggestions here: * Add _PaddingStride::_M_equal for opearator== and use _M_stride to implement it * Fix spaces, and cast index_type as in layout_left * Suggestion for LWG issue for both * Explanation that we can use existing member names for internal classes, and suggestion to use it for _PaddingStorage. With that ready for v4 > libstdc++-v3/include/std/mdspan | 263 ++++++++++++++++++ > libstdc++-v3/src/c++23/std.cc.in | 5 +- > .../23_containers/mdspan/layouts/ctors.cc | 3 +- > .../23_containers/mdspan/layouts/empty.cc | 1 + > .../23_containers/mdspan/layouts/mapping.cc | 6 +- > .../23_containers/mdspan/layouts/padded.cc | 4 + > .../mdspan/layouts/padded_neg.cc | 28 ++ > .../mdspan/layouts/padded_traits.h | 135 ++++++++- > 8 files changed, 437 insertions(+), 8 deletions(-) > > diff --git a/libstdc++-v3/include/std/mdspan > b/libstdc++-v3/include/std/mdspan > index 18782bf0a06..f61931ab8e6 100644 > --- a/libstdc++-v3/include/std/mdspan > +++ b/libstdc++-v3/include/std/mdspan > @@ -954,6 +954,32 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > : mapping(__other.extents(), __mdspan::__internal_ctor{}) > { __glibcxx_assert(*this == __other); } > > +#if __glibcxx_padded_layouts > + template<class _RightPaddedMapping> > + requires __mdspan::__is_right_padded_mapping<_RightPaddedMapping> > + && is_constructible_v<extents_type, > + typename > _RightPaddedMapping::extents_type> > Tabs instead of spaces, here and the rest of the file. > + constexpr > + explicit(!is_convertible_v<typename > _RightPaddedMapping::extents_type, > + extents_type>) > We should report bug against standard, because this constructor should be explicit, for Ranks > 1 and extent(0) or _S_padded_stride are dynamic, as we have precondition then. I think it should also be constrained, on what is now mandated, about satic_stride matching. We should match stride_mismatch, the same way as static extent mismatch is handled here. Same for layot_left. > + mapping(const _RightPaddedMapping& __other) noexcept > + : mapping(__other.extents(), __mdspan::__internal_ctor{}) > + { > + constexpr size_t __rank = extents_type::rank(); > + constexpr size_t __ostride_sta = __mdspan::__get_static_stride< > + _RightPaddedMapping>(); > + > + if constexpr (__rank > 1 > + && extents_type::static_extent(__rank - 1) != dynamic_extent > + && __ostride_sta != dynamic_extent) > + static_assert(extents_type::static_extent(__rank - 1) == > __ostride_sta); > + > + if constexpr (__rank > 1) > + __glibcxx_assert(__other.stride(__rank - 2) > + == __other.extents().extent(__rank - 1)); > + } > +#endif > + > constexpr mapping& > operator=(const mapping&) noexcept = default; > > @@ -1350,6 +1376,37 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > return __res; > } > > + template<typename _Extents, typename _Stride, typename... _Indices> > + constexpr typename _Extents::index_type > + __linear_index_rightpad(const _Extents& __exts, _Stride __stride, > + _Indices... __indices) > + { > + // i[n-1] + stride*(i[n-2] + extents.extent(n-2])*...) > + using _IndexType = typename _Extents::index_type; > + _IndexType __res = 0; > + if constexpr (sizeof...(__indices) > 0) > + { > + _IndexType __mult = 1; > + array<_IndexType, sizeof...(__indices)> > __ind_arr{__indices...}; > + > + auto __update_rest = [&, __pos = __exts.rank()-1](_IndexType) > mutable > + { > + --__pos; > + __res += __ind_arr[__pos] * __mult; > + __mult *= __exts.extent(__pos); > + }; > + > + auto __update = [&](_IndexType, auto... __rest) > + { > + __res += __ind_arr[__exts.rank() - 1]; > + __mult = __stride.extent(0); > + (__update_rest(__rest), ...); > + }; > + __update(__indices...); > + } > + return __res; > + } > + > template<size_t _Rank> > struct _LeftPaddedLayoutTraits > { > @@ -1384,6 +1441,39 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > } > }; > > + template<size_t _Rank> > + struct _RightPaddedLayoutTraits > + { > + using _LayoutSame = layout_right; > + using _LayoutOther = layout_left; > + > + constexpr static size_t _S_ext_idx = _Rank - 1; > + constexpr static size_t _S_stride_idx = _Rank - 2; > + constexpr static size_t _S_unpad_begin = 0; > + constexpr static size_t _S_unpad_end = _Rank - 1; > + > + template<typename _Mapping> > + constexpr static bool _S_is_same_padded_mapping = > + __is_right_padded_mapping<_Mapping>; > + > + template<typename _Mapping> > + constexpr static bool _S_is_other_padded_mapping = > + __is_left_padded_mapping<_Mapping>; > + > + template<typename _IndexType, size_t _StaticStride, > size_t..._Extents> > + constexpr static auto _S_make_padded_extent( > + extents<_IndexType, _StaticStride> __stride, > + const extents<_IndexType, _Extents...>& __exts) > + { > + auto __impl = [&]<size_t... _Is>(integer_sequence<size_t, > _Is...>) > + { > + return extents<_IndexType, (_Extents...[_Is])..., > _StaticStride>{ > + __exts.extent(_Is)..., __stride.extent(0)}; > + }; > + return __impl(make_index_sequence<sizeof...(_Extents) - 1>()); > + } > + }; > + > template<size_t _PaddingValue, typename _Extents, typename > _LayoutTraits> > class _PaddedStorage > { > @@ -1834,6 +1924,179 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > __other.stride(1))); > } > }; > + > + template<size_t _PaddingValue> > + template<typename _Extents> > + class layout_right_padded<_PaddingValue>::mapping { > + public: > + static constexpr size_t padding_value = _PaddingValue; > + 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_right_padded<_PaddingValue>; > + > + private: > + static constexpr size_t _S_rank = extents_type::rank(); > + using _RightPaddedStorage = __mdspan::_PaddedStorage<_PaddingValue, > + _Extents, __mdspan::_RightPaddedLayoutTraits<_S_rank>>; > + [[no_unique_address]] _RightPaddedStorage _M_storage; > + > + static constexpr size_t _S_static_stride = > + _RightPaddedStorage::_S_static_stride; > + > + consteval friend size_t > + __mdspan::__get_static_stride<mapping>(); > + > + constexpr index_type > + _M_extent(size_t __r) const noexcept > + { return _M_storage._M_extents.extent(__r); } > + > + constexpr index_type > + _M_dynamic_padded_stride() const noexcept > + { return _M_storage._M_stride.extent(0); } > + > + public: > + constexpr > + mapping() noexcept > + { } > + > + constexpr > + mapping(const mapping&) noexcept = default; > + > + constexpr > + mapping(const extents_type& __exts) > + : _M_storage(__exts) > + { } > + > + template<__mdspan::__valid_index_type<index_type> _OIndexType> > + constexpr mapping(const extents_type& __exts, _OIndexType __opad) > + : _M_storage(__exts, std::move(__opad)) > Cast to index_type here. > + { } > + > + template<typename _OExtents> > + requires is_constructible_v<extents_type, _OExtents> > + constexpr explicit(!is_convertible_v<_OExtents, extents_type>) > + mapping(const layout_right::mapping<_OExtents>& __other) > + : _M_storage(__other) > + { } > + > + template<typename _OExtents> > + requires is_constructible_v<_OExtents, extents_type> > + constexpr explicit(_OExtents::rank() > 0) > + mapping(const typename layout_stride::mapping<_OExtents>& > __other) > + : _M_storage(__other) > + { __glibcxx_assert(*this == __other); } > + > + template<typename _RightPaddedMapping> > + requires __mdspan::__is_right_padded_mapping<_RightPaddedMapping> > + && is_constructible_v<extents_type, > + typename > _RightPaddedMapping::extents_type> > + constexpr explicit(_S_rank > 1 && (padding_value != > dynamic_extent > + || _RightPaddedMapping::padding_value == dynamic_extent)) > + mapping(const _RightPaddedMapping& __other) > + : _M_storage(__other) > + { } > + > + template<typename _LeftPaddedMapping> > + requires (__mdspan::__is_left_padded_mapping<_LeftPaddedMapping> > + || __mdspan::__mapping_of<layout_left, _LeftPaddedMapping>) > + && (_S_rank <= 1) > + && is_constructible_v<extents_type, > + typename > _LeftPaddedMapping::extents_type> > + constexpr explicit(!is_convertible_v< > + typename _LeftPaddedMapping::extents_type, extents_type>) > + mapping(const _LeftPaddedMapping& __other) noexcept > + : _M_storage(__other) > + { } > + > + constexpr mapping& operator=(const mapping&) noexcept = default; > + > + constexpr const extents_type& > + extents() const noexcept { return _M_storage._M_extents; } > + > + constexpr array<index_type, _S_rank> > + strides() const noexcept > + { > + array<index_type, _S_rank> __ret; > + if constexpr (_S_rank > 0) > + __ret[_S_rank - 1] = 1; > + if constexpr (_S_rank > 1) > + __ret[_S_rank - 2] = _M_dynamic_padded_stride(); > + if constexpr (_S_rank > 2) > + for(size_t __i = _S_rank - 2; __i > 0; --__i) > + __ret[__i - 1] = __ret[__i] * _M_extent(__i); > + return __ret; > + } > + > + constexpr index_type > + required_span_size() const noexcept > + { return _M_storage._M_required_span_size(); } > You can name the matching function in PaddedStorage as "required_span_size()" without the "_M_prefix". We use _M_prefix as the name is reserved for implementation, and people are not allowed to do: #define _M_required_span_size #include <mdspan> Or in other words, if they do, is on them. Similary if the name is used somewhere, like required_span_size, we can use it direclty. I think I would prefer using exactly the same name for function that we just forward to, but I will leave it up to you. > + > + // _GLIBCXX_RESOLVE_LIB_DEFECTS > + // 4314. Missing move in mdspan layout mapping::operator() > + template<__mdspan::__valid_index_type<index_type>... _Indices> > + requires (sizeof...(_Indices) == _S_rank) > + constexpr index_type > + operator()(_Indices... __indices) const noexcept > + { > + return __mdspan::__linear_index_rightpad( > + extents(), _M_storage._M_stride, > + static_cast<index_type>(std::move(__indices))...); > + } > + > + static constexpr bool > + is_always_exhaustive() noexcept > + { return _RightPaddedStorage::_M_is_always_exhaustive(); } > + > + constexpr bool > + is_exhaustive() noexcept > + { return _M_storage._M_is_exhaustive(); } > + > + static constexpr bool > + is_always_unique() noexcept { return true; } > + > + static constexpr bool > + is_always_strided() noexcept { return true; } > + > + static constexpr bool > + is_unique() noexcept { return true; } > + > + static constexpr bool > + is_strided() noexcept { return true; } > + > + constexpr index_type > + stride(rank_type __r) const noexcept > + { > + __glibcxx_assert(__r < _S_rank); > + if constexpr (_S_rank <= 1) > + return 1; > + else > + { > + if (__r == _S_rank - 1) > + return 1; > + else if (__r == _S_rank - 2) > + return _M_dynamic_padded_stride(); > + else > + return static_cast<index_type>( > + static_cast<size_t>(_M_dynamic_padded_stride()) * > + static_cast<size_t>(__mdspan::__fwd_prod( > + extents(), __r + 1, _S_rank - 1))); > + } > + } > + > + template<typename _RightPaddedMapping> > + requires(__mdspan::__is_right_padded_mapping<_RightPaddedMapping> > + && _RightPaddedMapping::extents_type::rank() == _S_rank) > + friend constexpr bool > + operator==(const mapping& __self, const _RightPaddedMapping& > __other) > + noexcept > + { > + return __self.extents() == __other.extents() > + && (_S_rank < 2 || cmp_equal(__self.stride(_S_rank - 2), > + __other.stride(_S_rank - 2))); > + } > This could be just __self.extents() == __other.extents() && __self._M_stride == other._M_stride; I would add _M_equal method to _PaddingStride to handle this, and call it from here. > + }; > #endif > > template<typename _ElementType> > diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/ > std.cc.in > index f10bab59e2c..c1b4e4c88b7 100644 > --- a/libstdc++-v3/src/c++23/std.cc.in > +++ b/libstdc++-v3/src/c++23/std.cc.in > @@ -1871,9 +1871,10 @@ export namespace std > using std::mdspan; > #if __glibcxx_padded_layouts > using std::layout_left_padded; > + using std::layout_right_padded; > #endif > - // FIXME layout_right_padded, strided_slice, submdspan_mapping_result, > - // full_extent_t, full_extent, submdspan_extents, mdsubspan > + // FIXME strided_slice, submdspan_mapping_result, full_extent_t, > full_extent, > + // submdspan_extents, mdsubspan > } > #endif > > diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/ctors.cc > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/ctors.cc > index 891471467e1..73b161f5979 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/ctors.cc > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/ctors.cc > @@ -10,7 +10,7 @@ constexpr size_t dyn = std::dynamic_extent; > #if __glibcxx_padded_layouts > template<typename Layout> > constexpr bool > - is_padded_layout = is_left_padded<Layout>; > + is_padded_layout = is_left_padded<Layout> || is_right_padded<Layout>; > #else > template<typename> > constexpr bool > @@ -479,6 +479,7 @@ main() > test_all<std::layout_right>(); > #ifdef __glibcxx_padded_layouts > test_padded_all<std::layout_left_padded>(); > + test_padded_all<std::layout_right_padded>(); > #endif > > from_left_or_right::test_all<std::layout_left, std::layout_right>(); > diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/empty.cc > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/empty.cc > index 236aca8bc2b..c5519afe34f 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/empty.cc > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/empty.cc > @@ -142,6 +142,7 @@ main() > static_assert(test_all<std::layout_stride>()); > #ifdef __glibcxx_padded_layouts > static_assert(test_padded_all<std::layout_left_padded>()); > + static_assert(test_padded_all<std::layout_right_padded>()); > #endif > return 0; > } > diff --git > a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc > index 5bf6bf65d3a..57560a6aae7 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/mapping.cc > @@ -374,7 +374,7 @@ template<> > > #if __glibcxx_padded_layouts > template<typename Layout> > - requires is_left_padded<Layout> > + requires is_left_padded<Layout> || is_right_padded<Layout> > struct TestStride2D<Layout> > { > static constexpr void > @@ -458,7 +458,7 @@ template<> > > #if __glibcxx_padded_layouts > template<typename Layout> > - requires is_left_padded<Layout> > + requires is_left_padded<Layout> || is_right_padded<Layout> > struct TestStride3D<Layout> > { > static constexpr void > @@ -702,6 +702,7 @@ main() > test_all<std::layout_stride>(); > #ifdef __glibcxx_padded_layouts > test_padded_all<std::layout_left_padded>(); > + test_padded_all<std::layout_right_padded>(); > #endif > > test_has_op_eq<std::layout_right, std::layout_left, false>(); > @@ -709,6 +710,7 @@ main() > test_has_op_eq<std::layout_left, std::layout_stride, true>(); > #ifdef __glibcxx_padded_layouts > test_padded_has_op_eq<std::layout_left_padded>(); > + test_padded_has_op_eq<std::layout_right_padded>(); > #endif > > test_has_op_eq_peculiar(); > diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded.cc > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded.cc > index ea9a8ef3f4b..a607d1ddd02 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded.cc > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded.cc > @@ -670,6 +670,10 @@ main() > test_all<std::layout_left_padded>(); > static_assert(test_all<std::layout_left_padded>()); > > + test_all<std::layout_right_padded>(); > + static_assert(test_all<std::layout_right_padded>()); > + > test_from_pad_all<std::layout_left_padded>(); > + test_from_pad_all<std::layout_right_padded>(); > return 0; > } > diff --git > a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_neg.cc > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_neg.cc > index 29f12aa4de2..d0ac31c2810 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_neg.cc > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_neg.cc > @@ -15,6 +15,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_extens_representable_sta<std::layout_left_padded>()); > // { dg-error "from here" } > +static_assert(test_from_extens_representable_sta<std::layout_right_padded>()); > // { dg-error "from here" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -28,6 +29,7 @@ template<template<size_t> typename Layout> > return true; > } > > static_assert(test_from_extents_representable_padded_size<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_extents_representable_padded_size<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -40,6 +42,7 @@ template<template<size_t> typename Layout> > return true; > } > > static_assert(test_from_extents_representable_stride<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_extents_representable_stride<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -51,6 +54,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_pad_representable_stride<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_pad_representable_stride<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -62,6 +66,7 @@ template<template<size_t> typename Layout> > return true; > } > > static_assert(test_from_pad_representable_padded_size<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_pad_representable_padded_size<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -76,6 +81,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_left<std::layout_left_padded>()); // { dg-error > "required from here" } > +static_assert(test_from_left<std::layout_right_padded>()); // { dg-error > "required from here" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -90,6 +96,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_left_bad_runtime_stride<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_left_bad_runtime_stride<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -103,6 +110,7 @@ template<template<size_t> typename Layout> > return true; > } > > static_assert(test_from_left_representable_extents<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_left_representable_extents<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout, size_t PaddingValue> > constexpr bool > @@ -116,6 +124,8 @@ template<template<size_t> typename Layout, size_t > PaddingValue> > } > static_assert(test_pad_overflow<std::layout_left_padded, 1>()); // { > dg-error "expansion of" } > static_assert(test_pad_overflow<std::layout_left_padded, dyn>()); // { > dg-error "expansion of" } > +static_assert(test_pad_overflow<std::layout_right_padded, 1>()); // { > dg-error "expansion of" } > +static_assert(test_pad_overflow<std::layout_right_padded, dyn>()); // { > dg-error "expansion of" } > > template<template<size_t> typename Layout, size_t PaddingValue> > constexpr bool > @@ -128,6 +138,8 @@ template<template<size_t> typename Layout, size_t > PaddingValue> > } > static_assert(test_from_pad_negative<std::layout_left_padded, 1>()); // > { dg-error "expansion of" } > static_assert(test_from_pad_negative<std::layout_left_padded, dyn>()); // > { dg-error "expansion of" } > +static_assert(test_from_pad_negative<std::layout_right_padded, 1>()); > // { dg-error "expansion of" } > +static_assert(test_from_pad_negative<std::layout_right_padded, dyn>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout, size_t Pad> > constexpr bool > @@ -142,6 +154,8 @@ template<template<size_t> typename Layout, size_t Pad> > } > static_assert(test_static_pad_same<std::layout_left_padded, 1>()); // { > dg-error "expansion of" } > static_assert(test_static_pad_same<std::layout_left_padded, 3>()); // { > dg-error "expansion of" } > +static_assert(test_static_pad_same<std::layout_right_padded, 1>()); // { > dg-error "expansion of" } > +static_assert(test_static_pad_same<std::layout_right_padded, 3>()); // { > dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -156,6 +170,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_stride_wrong_stride0<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_stride_wrong_stride0<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -170,6 +185,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_stride_wrong_stride1<std::layout_left_padded>()); > // { dg-error "expansion of" } > +static_assert(test_from_stride_wrong_stride1<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -184,6 +200,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_stride_wrong_stride2<std::layout_left_padded>()); > +static_assert(test_from_stride_wrong_stride2<std::layout_right_padded>()); > > template<template<size_t> typename Layout> > constexpr bool > @@ -200,6 +217,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_stride_oversized<std::layout_left_padded>()); // > { dg-error "expansion of" } > +static_assert(test_from_stride_oversized<std::layout_right_padded>()); // > { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -213,6 +231,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_samepad_dyn<std::layout_left_padded>()); // { > dg-error "expansion of" } > +static_assert(test_from_samepad_dyn<std::layout_right_padded>()); // { > dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -226,6 +245,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_samepad_sta<std::layout_left_padded>()); // { > dg-error "expansion of" } > +static_assert(test_from_samepad_sta<std::layout_right_padded>()); // { > dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -240,6 +260,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_from_samepad_oversized<std::layout_left_padded>()); // > { dg-error "expansion of" } > +static_assert(test_from_samepad_oversized<std::layout_right_padded>()); > // { dg-error "expansion of" } > > template<template<size_t> typename Layout, size_t RunId> > constexpr bool > @@ -278,6 +299,10 @@ > static_assert(test_to_same_not_exhaustive<std::layout_left_padded, 0>()); > // { d > static_assert(test_to_same_not_exhaustive<std::layout_left_padded, 1>()); > // { dg-error "expansion of" } > static_assert(test_to_same_not_exhaustive<std::layout_left_padded, 2>()); > // { dg-error "expansion of" } > static_assert(test_to_same_not_exhaustive<std::layout_left_padded, 3>()); > // { dg-error "expansion of" } > +static_assert(test_to_same_not_exhaustive<std::layout_right_padded, > 0>()); // { dg-error "expansion of" } > +static_assert(test_to_same_not_exhaustive<std::layout_right_padded, > 1>()); // { dg-error "expansion of" } > +static_assert(test_to_same_not_exhaustive<std::layout_right_padded, > 2>()); // { dg-error "expansion of" } > +static_assert(test_to_same_not_exhaustive<std::layout_right_padded, > 3>()); // { dg-error "expansion of" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -290,6 +315,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_statically_bad_padding_value1<std::layout_left_padded>()); > // { dg-error "required from" } > +static_assert(test_statically_bad_padding_value1<std::layout_right_padded>()); > // { dg-error "required from" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -301,6 +327,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_statically_bad_padding_value2<std::layout_left_padded>()); > // { dg-error "required from" } > +static_assert(test_statically_bad_padding_value2<std::layout_right_padded>()); > // { dg-error "required from" } > > template<template<size_t> typename Layout> > constexpr bool > @@ -312,6 +339,7 @@ template<template<size_t> typename Layout> > return true; > } > static_assert(test_statically_oversized<std::layout_left_padded>()); // { > dg-error "from here" } > +static_assert(test_statically_oversized<std::layout_right_padded>()); // > { dg-error "from here" } > > // { dg-prune-output "padding_value must be representable as index_type" } > // { dg-prune-output "non-constant condition for static assertion" } > diff --git > a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_traits.h > b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_traits.h > index 1f0169d7c02..c267454f467 100644 > --- a/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_traits.h > +++ b/libstdc++-v3/testsuite/23_containers/mdspan/layouts/padded_traits.h > @@ -2,9 +2,86 @@ > #define TEST_MDSPAN_PADDED_TRAITS_H > > #if __glibcxx_padded_layouts > +template<typename Rev, typename Fwd> > + struct reverse_impl; > + > +template<size_t... Ir, size_t I0, size_t... I> > + struct reverse_impl<std::integer_sequence<size_t, Ir...>, > + std::integer_sequence<size_t, I0, I...>> > + { > + using type = typename reverse_impl<std::index_sequence<I0, Ir...>, > + std::index_sequence<I...>>::type; > + }; > + > +template<size_t... Ir> > + struct reverse_impl<std::integer_sequence<size_t, Ir...>, > + std::integer_sequence<size_t>> > + { > + using type = std::index_sequence<Ir...>; > + }; > + > +template<typename I> > + struct reverse; > + > +template<size_t... Ir> > + struct reverse<std::index_sequence<Ir...>> > + { > + using type = typename reverse_impl<std::integer_sequence<size_t>, > + std::integer_sequence<size_t, > Ir...>>::type; > + }; > + > +template<typename, typename> > + struct sequence_to_extents; > + > +template<typename IndexType, size_t... I> > + struct sequence_to_extents<IndexType, std::index_sequence<I...>> > + { > + using type = std::extents<IndexType, I...>; > + }; > + > +template<typename IndexType, size_t... I> > + struct reverse<std::extents<IndexType, I...>> > + { > + using type = typename sequence_to_extents< > + IndexType, > + typename reverse<std::index_sequence<I...>>::type > + >::type; > + }; > + > +template<typename Extents> > + constexpr auto > + dynamic_extents_array(const Extents& exts) > + { > + std::array<typename Extents::index_type, Extents::rank()> ret; > + for(size_t i = 0; i < Extents::rank(); ++i) > + ret[i] = exts.extent(i); > + return ret; > + } > + > +template<typename T, size_t N> > + constexpr std::array<T, N> > + reversed(const std::array<T, N>& fwd) > + { > + std::array<T, N> rev; > + for(size_t i = 0; i < N; ++i) > + rev[(N-1) - i] = fwd[i]; > + return rev; > + } > + > +template<typename IndexType, size_t... I> > + constexpr auto > + reversed(const std::extents<IndexType, I...>& exts) > + { > + using rev_type = typename reverse<std::extents<IndexType, > I...>>::type; > + return rev_type(reversed(dynamic_extents_array(exts))); > + } > + > +static_assert(std::array{3, 2, 1} == reversed(std::array{1, 2, 3})); > + > enum class PaddingSide > { > - Left > + Left, > + Right > }; > > template<typename Layout> > @@ -13,17 +90,33 @@ template<typename Layout> > template<size_t PaddingValue> > constexpr static bool > is_left_padded<std::layout_left_padded<PaddingValue>> = true; > > +template<typename Layout> > + constexpr static bool is_right_padded = false; > + > +template<size_t PaddingValue> > + constexpr static bool > is_right_padded<std::layout_right_padded<PaddingValue>> = true; > + > struct DeducePaddingSide > { > template<template<size_t> typename Layout> > constexpr static PaddingSide > from_template() > - { return PaddingSide::Left; } > + { > + if constexpr (std::same_as<Layout<0>, std::layout_left_padded<0>>) > + return PaddingSide::Left; > + else > + return PaddingSide::Right; > + } > > template<typename Layout> > constexpr static PaddingSide > from_typename() > - { return PaddingSide::Left; } > + { > + if constexpr (is_left_padded<Layout>) > + return PaddingSide::Left; > + else > + return PaddingSide::Right; > + } > }; > > template<PaddingSide Side> > @@ -59,5 +152,41 @@ template<> > { return exts.extent(0); } > }; > > +template<> > + struct LayoutTraits<PaddingSide::Right> > + { > + using layout_same = std::layout_right; > + using layout_other = std::layout_left; > + > + template<typename Extents> > + using extents_type = typename reverse<Extents>::type; > + > + template<typename Extents> > + constexpr static extents_type<Extents> > + make_extents(const Extents& exts) > + { return reversed(exts); } > + > + template<typename T, size_t N> > + constexpr static std::array<T, N> > + make_expected(const std::array<T, N>& expected) > + { return reversed(expected); } > + > + template<typename Mapping> > + constexpr static auto > + padded_stride(const Mapping& m) > + { > + auto rank = Mapping::extents_type::rank(); > + return m.stride(rank - 2); > + } > + > + template<typename Extents> > + constexpr static auto > + padded_extent(const Extents& exts) > + { > + auto rank = Extents::rank(); > + return exts.extent(rank - 1); > + } > + }; > + > #endif > #endif > -- > 2.50.1 > >
