On Tue, Jun 10, 2025 at 8:40 AM Luc Grosheintz <luc.groshei...@gmail.com>
wrote:
> If not committed yet, there's a style error, see below.
>
Will be included in my fixup commit.
>
> On 6/4/25 16:58, Luc Grosheintz wrote:
> > Implement the parts of layout_left that depend on layout_right; and the
> > parts of layout_right that don't depend on layout_stride.
> >
> > libstdc++-v3/ChangeLog:
> >
> > * include/std/mdspan (layout_right): New class.
> > * src/c++23/std.cc.in: Add layout_right.
> >
> > Signed-off-by: Luc Grosheintz <luc.groshei...@gmail.com>
> > ---
> > libstdc++-v3/include/std/mdspan | 153 ++++++++++++++++++++++++++++++-
> > libstdc++-v3/src/c++23/std.cc.in | 1 +
> > 2 files changed, 153 insertions(+), 1 deletion(-)
> >
> > diff --git a/libstdc++-v3/include/std/mdspan
> b/libstdc++-v3/include/std/mdspan
> > index 4c80438dbd6..8ab7a1a52fb 100644
> > --- a/libstdc++-v3/include/std/mdspan
> > +++ b/libstdc++-v3/include/std/mdspan
> > @@ -409,6 +409,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > class mapping;
> > };
> >
> > + struct layout_right
> > + {
> > + template<typename _Extents>
> > + class mapping;
> > + };
> > +
> > namespace __mdspan
> > {
> > template<typename _Tp>
> > @@ -501,7 +507,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > _Mapping>;
> >
> > template<typename _Mapping>
> > - concept __standardized_mapping = __mapping_of<layout_left,
> _Mapping>;
> > + concept __standardized_mapping = __mapping_of<layout_left,
> _Mapping>
> > + || __mapping_of<layout_right,
> _Mapping>;
> >
> > // A tag type to create internal ctors.
> > class __internal_ctor
> > @@ -539,6 +546,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > : mapping(__other.extents(), __mdspan::__internal_ctor{})
> > { }
> >
> > + template<typename _OExtents>
> > + requires (extents_type::rank() <= 1)
> > + && is_constructible_v<extents_type, _OExtents>
> > + constexpr explicit(!is_convertible_v<_OExtents, extents_type>)
> > + mapping(const layout_right::mapping<_OExtents>& __other) noexcept
> > + : mapping(__other.extents(), __mdspan::__internal_ctor{})
> > + { }
> > +
> > constexpr mapping&
> > operator=(const mapping&) noexcept = default;
> >
> > @@ -605,6 +620,142 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > [[no_unique_address]] extents_type _M_extents{};
> > };
> >
> > + namespace __mdspan
> > + {
> > + template<typename _Extents, typename... _Indices>
> > + constexpr typename _Extents::index_type
> > + __linear_index_right(const _Extents& __exts, _Indices...
> __indices)
> > + noexcept
> > + {
> > + using _IndexType = typename _Extents::index_type;
> > + array<_IndexType, sizeof...(__indices)> __ind_arr{__indices...};
> > + _IndexType __res = 0;
> > + if constexpr (sizeof...(__indices) > 0)
> > + {
> > + _IndexType __mult = 1;
> > + auto __update = [&, __pos = __exts.rank()](_IndexType) mutable
> > + {
> > + --__pos;
> > + __res += __ind_arr[__pos] * __mult;
> > + __mult *= __exts.extent(__pos);
> > + };
> > + (__update(__indices), ...);
> > + }
> > + return __res;
> > + }
> > + }
> > +
> > + template<typename _Extents>
> > + class layout_right::mapping
> > + {
> > + public:
> > + 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;
> > +
> > + static_assert(__mdspan::__representable_size<extents_type,
> index_type>,
> > + "The size of extents_type must be representable as index_type");
> > +
> > + constexpr
> > + mapping() noexcept = default;
> > +
> > + constexpr
> > + mapping(const mapping&) noexcept = default;
> > +
> > + constexpr
> > + mapping(const extents_type& __extents) noexcept
> > + : _M_extents(__extents)
> > + {
> __glibcxx_assert(__mdspan::__is_representable_extents(_M_extents)); }
> > +
> > + template<typename _OExtents>
> > + requires is_constructible_v<extents_type, _OExtents>
> > + constexpr explicit(!is_convertible_v<_OExtents, extents_type>)
> > + mapping(const mapping<_OExtents>& __other) noexcept
> > + : mapping(__other.extents(), __mdspan::__internal_ctor{})
> > + { }
> > +
> > + template<class _OExtents>
>
> s/template<class/template<typename/
>
> > + requires (extents_type::rank() <= 1)
> > + && is_constructible_v<extents_type, _OExtents>
> > + constexpr explicit(!is_convertible_v<_OExtents, extents_type>)
> > + mapping(const layout_left::mapping<_OExtents>& __other) noexcept
> > + : mapping(__other.extents(), __mdspan::__internal_ctor{})
> > + { }
> > +
> > + constexpr mapping&
> > + operator=(const mapping&) noexcept = default;
> > +
> > + constexpr const extents_type&
> > + extents() const noexcept { return _M_extents; }
> > +
> > + constexpr index_type
> > + required_span_size() const noexcept
> > + { return __mdspan::__fwd_prod(_M_extents, extents_type::rank()); }
> > +
> > + template<__mdspan::__valid_index_type<index_type>... _Indices>
> > + requires (sizeof...(_Indices) == extents_type::rank())
> > + constexpr index_type
> > + operator()(_Indices... __indices) const noexcept
> > + {
> > + return __mdspan::__linear_index_right(
> > + _M_extents, static_cast<index_type>(__indices)...);
> > + }
> > +
> > + static constexpr bool
> > + is_always_unique() noexcept
> > + { return true; }
> > +
> > + static constexpr bool
> > + is_always_exhaustive() noexcept
> > + { return true; }
> > +
> > + static constexpr bool
> > + is_always_strided() noexcept
> > + { return true; }
> > +
> > + static constexpr bool
> > + is_unique() noexcept
> > + { return true; }
> > +
> > + static constexpr bool
> > + is_exhaustive() noexcept
> > + { return true; }
> > +
> > + static constexpr bool
> > + is_strided() noexcept
> > + { return true; }
> > +
> > + constexpr index_type
> > + stride(rank_type __i) const noexcept
> > + requires (extents_type::rank() > 0)
> > + {
> > + __glibcxx_assert(__i < extents_type::rank());
> > + return __mdspan::__rev_prod(_M_extents, __i);
> > + }
> > +
> > + template<typename _OExtents>
> > + requires (extents_type::rank() == _OExtents::rank())
> > + friend constexpr bool
> > + operator==(const mapping& __self, const mapping<_OExtents>&
> __other)
> > + noexcept
> > + { return __self.extents() == __other.extents(); }
> > +
> > + private:
> > + 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));
> > + }
> > +
> > + [[no_unique_address]] extents_type _M_extents{};
> > + };
> > +
> > _GLIBCXX_END_NAMESPACE_VERSION
> > }
> > #endif
> > diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/
> std.cc.in
> > index 8ea57132a2a..fe1407d71da 100644
> > --- a/libstdc++-v3/src/c++23/std.cc.in
> > +++ b/libstdc++-v3/src/c++23/std.cc.in
> > @@ -1845,6 +1845,7 @@ export namespace std
> > {
> > using std::extents;
> > using std::layout_left;
> > + using std::layout_right;
> > // FIXME layout_*, default_accessor and mdspan
> > }
> > #endif
>
>
