diff mbox series

[v4,5/5] libstdc++: Implement submdspan_mapping for layout_right_padded. [PR110352]

Message ID 20251204212846.248887-6-luc.grosheintz@gmail.com
State New
Headers
Series libstdc++: submdspan (part 2) |

Commit Message

Luc Grosheintz Dec. 4, 2025, 9:28 p.m. UTC 
  Implements submdspan for layout_right_padded as described in P3663.

	PR libstdc++/110352

libstdc++-v3/ChangeLog:

	* include/std/mdspan (layout_right_padded::submdspan_mapping):
	New friend method.
	* testsuite/23_containers/mdspan/submdspan/submdspan.cc:
	Instantiate test for layout_right_padded.
	* testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc:
	Ditto.

Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
---
 libstdc++-v3/include/std/mdspan               | 45 +++++++++++++++++++
 .../mdspan/submdspan/submdspan.cc             |  7 ++-
 .../mdspan/submdspan/submdspan_mapping.cc     |  4 ++
 3 files changed, 54 insertions(+), 2 deletions(-)

Comments

Tomasz Kamiński Dec. 5, 2025, 1:42 p.m. UTC | #1 
On Thu, Dec 4, 2025 at 10:35 PM Luc Grosheintz <luc.grosheintz@gmail.com>
wrote:

> Implements submdspan for layout_right_padded as described in P3663.
>
>         PR libstdc++/110352
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/mdspan (layout_right_padded::submdspan_mapping):
>         New friend method.
>         * testsuite/23_containers/mdspan/submdspan/submdspan.cc:
>         Instantiate test for layout_right_padded.
>         * testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc:
>         Ditto.
>
> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
> ---
>
Same comments as for previous patch.

>  libstdc++-v3/include/std/mdspan               | 45 +++++++++++++++++++
>  .../mdspan/submdspan/submdspan.cc             |  7 ++-
>  .../mdspan/submdspan/submdspan_mapping.cc     |  4 ++
>  3 files changed, 54 insertions(+), 2 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> index 21dbe6def22..269522f4a5a 100644
> --- a/libstdc++-v3/include/std/mdspan
> +++ b/libstdc++-v3/include/std/mdspan
> @@ -1353,40 +1353,76 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>             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 _SubRank, size_t _Nm>
>           static consteval bool
>           _S_is_unpadded_submdspan(span<const _SliceKind, _Nm>
> __slice_kinds)
>           {
>             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<_SubRank>(span(__rev_slice_kinds));
>           }
>        };
>
> +    template<>
> +      struct _SubMdspanMapping<_LayoutSide::__right, true>
> +      {
> +       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 - 1);
> +           constexpr auto __sta_padstride
> +             = __mdspan::__get_static_stride<_Mapping>();
> +           if constexpr (__sta_padstride == dynamic_extent
> +                         || !__mdspan::__all_static(__sta_exts))
> +             return dynamic_extent;
> +           else
> +             return __sta_padstride * __mdspan::__fwd_prod(__sta_exts);
> +         }
> +
> +       template<size_t _SubRank, size_t _Nm>
> +         static consteval bool
> +         _S_is_unpadded_submdspan(span<const _SliceKind, _Nm>
> __slice_kinds)
> +         {
> +           if constexpr (_SubRank == 1)
>
Again, would peffer expressing this as in previous patch.

> +             return __slice_kinds[_Nm - 1] ==
> _SliceKind::__unit_strided_slice
> +               || __slice_kinds[_Nm - 1] == _SliceKind::__full;
> +           else
> +             return false;
> +         }
> +      };
> +
> +
>      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)
>        {
>         constexpr auto __side = __mdspan::__mapping_side<_Mapping>();
>         using _Trait = _SubMdspanMapping<__side,
> __is_padded_mapping<_Mapping>>;
>
>         constexpr auto __slice_kinds =
> __mdspan::__make_slice_kind_array<_Slices...>();
>         auto __offset = __mdspan::__suboffset(__mapping, __slices...);
>         auto __sub_exts = __mdspan::__subextents(__mapping.extents(),
> __slices...);
>         using _SubExts = decltype(__sub_exts);
>         constexpr auto __sub_rank = _SubExts::rank();
>         if constexpr (__sub_rank == 0)
>           return submdspan_mapping_result{
> @@ -2748,40 +2784,49 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>           if constexpr (_S_rank <= 1)
>             return 1;
>           else if (__r == _S_rank - 1)
>             return 1;
>           else if (__r == _S_rank - 2)
>             return _M_padstride();
>           else
>             return static_cast<index_type>(
>               static_cast<size_t>(_M_padstride()) *
>               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._M_storage._M_equal(__other); }
> +
> +#if __glibcxx_submdspan
> +      private:
> +       template<__mdspan::__acceptable_slice_type<index_type>... _Slices>
>
Will be in static_assert.

> +         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
>        };
>  #endif // __glibcxx_padded_layouts
>
>    template<typename _ElementType>
>      struct default_accessor
>      {
>        static_assert(!is_array_v<_ElementType>,
>         "ElementType must not be an array type");
>        static_assert(!is_abstract_v<_ElementType>,
>         "ElementType must not be an abstract class type");
>
>        using offset_policy = default_accessor;
>        using element_type = _ElementType;
>        using reference = element_type&;
>        using data_handle_type = element_type*;
>
>        constexpr
>        default_accessor() noexcept = default;
>
>        template<typename _OElementType>
> diff --git
> a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
> b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
> index 927b5d06c6b..f8382847fe3 100644
> --- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
> +++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
> @@ -348,27 +348,30 @@ template<typename Layout>
>      };
>
>      run(std::extents(3, 5, 7));
>      run(std::extents<int, 3, 5, 7>{});
>      return true;
>    }
>
>  template<typename Layout>
>    constexpr bool
>    test_all()
>    {
>      test_all_cheap<Layout>();
>      test_all_expensive<Layout>();
>      return true;
>    }
>
>  int
>  main()
>  {
>    test_all<std::layout_left>();
> +  test_all<std::layout_right>();
> +  test_all<std::layout_stride>();
>    test_all<std::layout_left_padded<1>>();
>    test_all<std::layout_left_padded<8>>();
>    test_all<std::layout_left_padded<dyn>>();
> -  test_all<std::layout_right>();
> -  test_all<std::layout_stride>();
> +  test_all<std::layout_right_padded<1>>();
> +  test_all<std::layout_right_padded<8>>();
> +  test_all<std::layout_right_padded<dyn>>();
>    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 50836968a06..efd71d10f9d 100644
> ---
> a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
> +++
> b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
> @@ -273,25 +273,29 @@ template<typename Layout>
>      static_assert(test_layout_common_return_types<Layout>());
>
>      test_layout_padded_return_types<Layout>();
>      static_assert(test_layout_padded_return_types<Layout>());
>
>      test_layout_padded_padding_value<Layout>();
>      static_assert(test_layout_padded_padding_value<Layout>());
>      return true;
>    }
>
>  int
>  main()
>  {
>    test_return_types_unpadded_all<std::layout_left>();
>    test_return_types_unpadded_all<std::layout_right>();
>
>    test_return_types_padded_all<std::layout_left_padded<1>>();
>    test_return_types_padded_all<std::layout_left_padded<2>>();
>    test_return_types_padded_all<std::layout_left_padded<dyn>>();
>
> +  test_return_types_padded_all<std::layout_right_padded<1>>();
> +  test_return_types_padded_all<std::layout_right_padded<2>>();
> +  test_return_types_padded_all<std::layout_right_padded<dyn>>();
>
And to seprate cc files.

> +
>    test_layout_stride_return_types();
>    static_assert(test_layout_stride_return_types());
>    return 0;
>  }
>
> --
> 2.52.0
>
>
diff mbox series

Patch

diff --git a/libstdc++-v3/include/std/mdspan b/libstdc++-v3/include/std/mdspan
index 21dbe6def22..269522f4a5a 100644
--- a/libstdc++-v3/include/std/mdspan
+++ b/libstdc++-v3/include/std/mdspan
@@ -1353,40 +1353,76 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    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 _SubRank, size_t _Nm>
 	  static consteval bool
 	  _S_is_unpadded_submdspan(span<const _SliceKind, _Nm> __slice_kinds)
 	  {
 	    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<_SubRank>(span(__rev_slice_kinds));
 	  }
       };
 
+    template<>
+      struct _SubMdspanMapping<_LayoutSide::__right, true>
+      {
+	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 - 1);
+	    constexpr auto __sta_padstride
+	      = __mdspan::__get_static_stride<_Mapping>();
+	    if constexpr (__sta_padstride == dynamic_extent
+			  || !__mdspan::__all_static(__sta_exts))
+	      return dynamic_extent;
+	    else
+	      return __sta_padstride * __mdspan::__fwd_prod(__sta_exts);
+	  }
+
+	template<size_t _SubRank, size_t _Nm>
+	  static consteval bool
+	  _S_is_unpadded_submdspan(span<const _SliceKind, _Nm> __slice_kinds)
+	  {
+	    if constexpr (_SubRank == 1)
+	      return __slice_kinds[_Nm - 1] == _SliceKind::__unit_strided_slice
+		|| __slice_kinds[_Nm - 1] == _SliceKind::__full;
+	    else
+	      return false;
+	  }
+      };
+
+
     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)
       {
 	constexpr auto __side = __mdspan::__mapping_side<_Mapping>();
 	using _Trait = _SubMdspanMapping<__side, __is_padded_mapping<_Mapping>>;
 
 	constexpr auto __slice_kinds = __mdspan::__make_slice_kind_array<_Slices...>();
 	auto __offset = __mdspan::__suboffset(__mapping, __slices...);
 	auto __sub_exts = __mdspan::__subextents(__mapping.extents(), __slices...);
 	using _SubExts = decltype(__sub_exts);
 	constexpr auto __sub_rank = _SubExts::rank();
 	if constexpr (__sub_rank == 0)
 	  return submdspan_mapping_result{
@@ -2748,40 +2784,49 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  if constexpr (_S_rank <= 1)
 	    return 1;
 	  else if (__r == _S_rank - 1)
 	    return 1;
 	  else if (__r == _S_rank - 2)
 	    return _M_padstride();
 	  else
 	    return static_cast<index_type>(
 	      static_cast<size_t>(_M_padstride()) *
 	      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._M_storage._M_equal(__other); }
+
+#if __glibcxx_submdspan
+      private:
+	template<__mdspan::__acceptable_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
       };
 #endif // __glibcxx_padded_layouts
 
   template<typename _ElementType>
     struct default_accessor
     {
       static_assert(!is_array_v<_ElementType>,
 	"ElementType must not be an array type");
       static_assert(!is_abstract_v<_ElementType>,
 	"ElementType must not be an abstract class type");
 
       using offset_policy = default_accessor;
       using element_type = _ElementType;
       using reference = element_type&;
       using data_handle_type = element_type*;
 
       constexpr
       default_accessor() noexcept = default;
 
       template<typename _OElementType>
diff --git a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
index 927b5d06c6b..f8382847fe3 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan.cc
@@ -348,27 +348,30 @@  template<typename Layout>
     };
 
     run(std::extents(3, 5, 7));
     run(std::extents<int, 3, 5, 7>{});
     return true;
   }
 
 template<typename Layout>
   constexpr bool
   test_all()
   {
     test_all_cheap<Layout>();
     test_all_expensive<Layout>();
     return true;
   }
 
 int
 main()
 {
   test_all<std::layout_left>();
+  test_all<std::layout_right>();
+  test_all<std::layout_stride>();
   test_all<std::layout_left_padded<1>>();
   test_all<std::layout_left_padded<8>>();
   test_all<std::layout_left_padded<dyn>>();
-  test_all<std::layout_right>();
-  test_all<std::layout_stride>();
+  test_all<std::layout_right_padded<1>>();
+  test_all<std::layout_right_padded<8>>();
+  test_all<std::layout_right_padded<dyn>>();
   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 50836968a06..efd71d10f9d 100644
--- a/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
+++ b/libstdc++-v3/testsuite/23_containers/mdspan/submdspan/submdspan_mapping.cc
@@ -273,25 +273,29 @@  template<typename Layout>
     static_assert(test_layout_common_return_types<Layout>());
 
     test_layout_padded_return_types<Layout>();
     static_assert(test_layout_padded_return_types<Layout>());
 
     test_layout_padded_padding_value<Layout>();
     static_assert(test_layout_padded_padding_value<Layout>());
     return true;
   }
 
 int
 main()
 {
   test_return_types_unpadded_all<std::layout_left>();
   test_return_types_unpadded_all<std::layout_right>();
 
   test_return_types_padded_all<std::layout_left_padded<1>>();
   test_return_types_padded_all<std::layout_left_padded<2>>();
   test_return_types_padded_all<std::layout_left_padded<dyn>>();
 
+  test_return_types_padded_all<std::layout_right_padded<1>>();
+  test_return_types_padded_all<std::layout_right_padded<2>>();
+  test_return_types_padded_all<std::layout_right_padded<dyn>>();
+
   test_layout_stride_return_types();
   static_assert(test_layout_stride_return_types());
   return 0;
 }