[PATCH v2 05/10] libstdc++: Implement submdspan_mapping for layout_right. [PR110352]
Luc Grosheintz
luc.grosheintz@gmail.com
Tue Nov 18 14:24:56 GMT 2025
Adds submdspan_mapping for layout_right as described in P3663.
PR libstdc++/110352
libstdc++-v3/ChangeLog:
* include/std/mdspan (layout_right::mapping::submdspan_mapping): New
friend function.
* testsuite/23_containers/mdspan/submdspan/submdspan.cc:
Instantiate tests for layout_right.
* testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc:
Ditto.
* testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc:
Ditto.
Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
---
libstdc++-v3/include/std/mdspan | 56 +++++++++++++++++++
.../mdspan/submdspan/submdspan.cc | 1 +
.../mdspan/submdspan/submdspan_mapping.cc | 6 ++
.../mdspan/submdspan/submdspan_neg.cc | 9 +++
4 files changed, 72 insertions(+)
diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 712826ea7e7..594a92640a4 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -1317,20 +1317,34 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
template<_LayoutSide _Side, typename _IndexType, size_t _SubRank,
typename... _Slices>
static consteval size_t
__padded_block_begin()
{
if constexpr (_Side == _LayoutSide::__left)
return __padded_block_begin_generic<_IndexType, _SubRank,
_Slices...>();
+ else
+ {
+ constexpr auto __rank = sizeof...(_Slices);
+ auto __impl = [&]<size_t... _Is>(index_sequence<_Is...>)
+ {
+ auto __u = __padded_block_begin_generic<
+ _IndexType, _SubRank, _Slices...[__rank - 1 - _Is]...>();
+ if (__u == dynamic_extent)
+ return dynamic_extent;
+ else
+ return __rank - 1 - __u;
+ };
+ return __impl(make_index_sequence<__rank>());
+ }
}
template<_LayoutSide _Side>
struct _SubMdspanMapping;
template<>
struct _SubMdspanMapping<_LayoutSide::__left>
{
using _Layout = layout_left;
template<size_t _Pad> using _PaddedLayout = layout_left_padded<_Pad>;
@@ -1346,20 +1360,54 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
else
return __fwd_prod(__sta_exts);
}
template<typename _IndexType, size_t _SubRank, typename... _Slices>
static consteval bool
_S_is_unpadded_submdspan()
{ return __is_compact_block<_IndexType, _SubRank, _Slices...>(); }
};
+ 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
+ = __static_extents<_Extents>(_Us + 1, __rank);
+ if constexpr (!__all_static(__sta_exts))
+ return dynamic_extent;
+ else
+ return __fwd_prod(__sta_exts);
+ }
+
+ template<typename _IndexType, size_t _SubRank, typename... _Slices>
+ static consteval bool
+ _S_is_unpadded_submdspan()
+ {
+ constexpr auto __rank = sizeof...(_Slices);
+ auto __impl = [&]<size_t... _Is>(index_sequence<_Is...>)
+ {
+ return __is_compact_block<
+ _IndexType, _SubRank, _Slices...[__rank - 1 - _Is]...>();
+ };
+ return __impl(make_index_sequence<__rank>());
+ }
+ };
+
template<typename _Mapping>
constexpr auto
__submdspan_mapping_impl(const _Mapping& __mapping)
{ return submdspan_mapping_result{__mapping, 0}; }
template<typename _Mapping, typename... _Slices>
requires (sizeof...(_Slices) > 0)
constexpr auto
__submdspan_mapping_impl(const _Mapping& __mapping, _Slices... __slices)
{
@@ -1716,20 +1764,28 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _OExtents>
constexpr explicit
mapping(const _OExtents& __oexts, __mdspan::__internal_ctor) noexcept
: _M_extents(__oexts)
{
static_assert(__mdspan::__representable_size<_OExtents, index_type>,
"The size of OtherExtents must be representable as index_type");
__glibcxx_assert(__mdspan::__is_representable_extents(_M_extents));
}
+#if __glibcxx_padded_layouts
+ template<__mdspan::__valid_canonical_slice_type<index_type>... _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{};
};
namespace __mdspan
{
template<typename _Mp>
concept __mapping_alike = requires
{
requires __is_extents<typename _Mp::extents_type>;
{ _Mp::is_always_strided() } -> same_as<bool>;
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
index 53e91407a9c..cd6e9454b17 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
@@ -358,12 +358,13 @@ template<typename Layout>
{
test_all_cheap<Layout>();
test_all_expensive<Layout>();
return true;
}
int
main()
{
test_all<std::layout_left>();
+ test_all<std::layout_right>();
return 0;
}
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
index a37d3cd588f..cc832cdb415 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
@@ -122,15 +122,21 @@ template<typename Layout>
check(std::extents(3, 5, 7, 11, 13), dyn);
return true;
}
int
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;
}
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc
index 4f9aad81cb7..3d6b0191e17 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_neg.cc
@@ -17,86 +17,95 @@ template<typename Layout, typename... Slices>
}
template<typename Layout>
constexpr bool
test_int_under()
{
check_slice_range<Layout>(1, -1, 2); // { dg-error "expansion of" }
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
test_int_over()
{
check_slice_range<Layout>(1, 5, 2); // { dg-error "expansion of" }
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
test_tuple_under()
{
check_slice_range<Layout>(1, std::tuple{-1, 2}, 2); // { dg-error "expansion of" }
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
test_tuple_reversed()
{
check_slice_range<Layout>(1, std::tuple{3, 2}, 2); // { dg-error "expansion of" }
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
test_tuple_over()
{
check_slice_range<Layout>(1, std::tuple{0, 6}, 2); // { dg-error "expansion of" }
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
test_strided_slice_zero()
{
check_slice_range<Layout>(1, std::strided_slice{1, 1, 0}, 2); // { dg-error "expansion of" }
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
test_strided_slice_offset_under()
{
check_slice_range<Layout>(1, std::strided_slice{-1, 1, 1}, 2); // { dg-error "expansion of" }
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
test_strided_slice_offset_over()
{
check_slice_range<Layout>(1, std::strided_slice{6, 0, 1}, 2); // { dg-error "expansion of" }
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
test_strided_slice_extent_over()
{
check_slice_range<Layout>(1, std::strided_slice{1, 5, 1}, 2); // { dg-error "expansion of" }
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" }
// { dg-prune-output "non-constant condition" }
--
2.51.2
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