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libstdc++: Implement submdspan_mapping for layout_right. [PR110352] 

Adds submdspan_mapping for layout_right as described in P3663.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan
	(__mdspan::_SubMdspanMapping<_LayoutSide::__right>): Define.
	(layout_right::mapping::submdspan_mapping): New friend function.
	* testsuite/23_containers/mdspan/submdspan/selections/right.cc:
	Instantiate tests for layout_right.
	* testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc:
	Ditto.
	* testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc:
	Ditto.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
This commit is contained in:
Luc Grosheintz 2025-12-08 21:23:42 +01:00 committed by Tomasz Kamiński
parent ead579d3c5
commit c1c5ada671
4 changed files with 64 additions and 0 deletions
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40
libstdc++-v3/include/std/mdspan
View File

@ -1303,6 +1303,38 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return __mdspan::__is_block(__slice_kinds, __sub_rank); }
};
template<>
struct _SubMdspanMapping<_LayoutSide::__right>
{
using _Layout = layout_right;
template<size_t _Pad> using _PaddedLayout = layout_right_padded<_Pad>;
template<typename _Mapping, size_t _Us>
static consteval size_t
_S_pad()
{
using _Extents = typename _Mapping::extents_type;
constexpr auto __rank = _Extents::rank();
constexpr auto __sta_exts
= __mdspan::__static_extents<_Extents>(_Us + 1, __rank);
if constexpr (!__mdspan::__all_static(__sta_exts))
return dynamic_extent;
else
return __fwd_prod(__sta_exts);
}
template<size_t _Nm>
static consteval bool
_S_is_unpadded_submdspan(span<const _SliceKind, _Nm> __slice_kinds,
size_t __sub_rank)
{
auto __rev_slice_kinds = array<_SliceKind, _Nm>{};
for(size_t __i = 0; __i < _Nm; ++__i)
__rev_slice_kinds[__i] = __slice_kinds[_Nm - 1 - __i];
return __mdspan::__is_block(span(__rev_slice_kinds), __sub_rank);
}
};
template<typename _Mapping>
constexpr auto
__submdspan_mapping_impl(const _Mapping& __mapping)
@ -1678,6 +1710,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__glibcxx_assert(__mdspan::__is_representable_extents(_M_extents));
}
#if __glibcxx_submdspan
template<typename... _Slices>
requires (extents_type::rank() == sizeof...(_Slices))
friend constexpr auto
submdspan_mapping(const mapping& __mapping, _Slices... __slices)
{ return __mdspan::__submdspan_mapping_impl(__mapping, __slices...); }
#endif // __glibcxx_submdspan
[[no_unique_address]] extents_type _M_extents{};
};

9
libstdc++-v3/testsuite/23_containers/mdspan/submdspan/selections/right.cc Normal file
View File

@ -0,0 +1,9 @@
// { dg-do run { target c++26 } }
#include "testcases.h"
int
main()
{
test_all<std::layout_right>();
return 0;
}

6
libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
View File

@ -129,8 +129,14 @@ main()
test_layout_unpadded_return_types<std::layout_left>();
static_assert(test_layout_unpadded_return_types<std::layout_left>());
test_layout_unpadded_return_types<std::layout_right>();
static_assert(test_layout_unpadded_return_types<std::layout_right>());
test_layout_unpadded_padding_value<std::layout_left>();
static_assert(test_layout_unpadded_padding_value<std::layout_left>());
test_layout_unpadded_padding_value<std::layout_right>();
static_assert(test_layout_unpadded_padding_value<std::layout_right>());
return 0;
}

9
libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc
View File

@ -24,6 +24,7 @@ template<typename Layout>
return true;
}
static_assert(test_int_under<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_int_under<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -33,6 +34,7 @@ template<typename Layout>
return true;
}
static_assert(test_int_over<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_int_over<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -42,6 +44,7 @@ template<typename Layout>
return true;
}
static_assert(test_tuple_under<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_tuple_under<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -51,6 +54,7 @@ template<typename Layout>
return true;
}
static_assert(test_tuple_reversed<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_tuple_reversed<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -60,6 +64,7 @@ template<typename Layout>
return true;
}
static_assert(test_tuple_over<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_tuple_over<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -69,6 +74,7 @@ template<typename Layout>
return true;
}
static_assert(test_strided_slice_zero<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_strided_slice_zero<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -78,6 +84,7 @@ template<typename Layout>
return true;
}
static_assert(test_strided_slice_offset_under<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_strided_slice_offset_under<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -87,6 +94,7 @@ template<typename Layout>
return true;
}
static_assert(test_strided_slice_offset_over<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_strided_slice_offset_over<std::layout_right>()); // { dg-error "expansion of" }
template<typename Layout>
constexpr bool
@ -96,6 +104,7 @@ template<typename Layout>
return true;
}
static_assert(test_strided_slice_extent_over<std::layout_left>()); // { dg-error "expansion of" }
static_assert(test_strided_slice_extent_over<std::layout_right>()); // { dg-error "expansion of" }
// { dg-prune-output "static assertion failed" }
// { dg-prune-output "__glibcxx_assert_fail" }