fcaccf817d
This patch adds std::extents. extents is one of the core classes used by std::mdspan. It describes a multi-dimensional index space with a mix of compile time and runtime sizes. Furthermore, it is templated on the index type used to describe the multi-dimensional index space. The class is designed to be highly optimizable in performance critical code sections, and is fully useable in constant expressions contexts. Testing of this class tends to be somewhat combinatorical, due to the large number of possible corner cases involved in situations where we have both runtime and compile time extents. To add to this, the class is designed to be interoperable (in particular constructible) from arguments which only need to be convertible to the index_type, but are otherwise arbitrary user types. For a larger discussion on the design of this class refer to: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p0009r18.html Co-authored-by: Damien L-G <dalg24@gmail.com> Reviewed By: ldionne, #libc Spies: libcxx-commits, H-G-Hristov, tschuett, philnik, arichardson, Mordante, crtrott Differential Revision: https://reviews.llvm.org/D148067
70 lines
2.4 KiB
Plaintext
70 lines
2.4 KiB
Plaintext
// -*-C++ - *-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===---------------------------------------------------------------------===//
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/*
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extents synopsis
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namespace std {
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template<class _IndexType, size_t... _Extents>
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class extents {
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public:
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using index_type = _IndexType;
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using size_type = make_unsigned_t<index_type>;
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using rank_type = size_t;
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// [mdspan.extents.obs], observers of the multidimensional index space
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static constexpr rank_type rank() noexcept { return sizeof...(_Extents); }
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static constexpr rank_type rank_dynamic() noexcept { return dynamic-index(rank()); }
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static constexpr size_t static_extent(rank_type) noexcept;
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constexpr index_type extent(rank_type) const noexcept;
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// [mdspan.extents.cons], constructors
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constexpr extents() noexcept = default;
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template<class _OtherIndexType, size_t... _OtherExtents>
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constexpr explicit(see below)
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extents(const extents<_OtherIndexType, _OtherExtents...>&) noexcept;
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template<class... _OtherIndexTypes>
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constexpr explicit extents(_OtherIndexTypes...) noexcept;
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template<class _OtherIndexType, size_t N>
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constexpr explicit(N != rank_dynamic())
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extents(span<_OtherIndexType, N>) noexcept;
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template<class _OtherIndexType, size_t N>
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constexpr explicit(N != rank_dynamic())
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extents(const array<_OtherIndexType, N>&) noexcept;
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// [mdspan.extents.cmp], comparison operators
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template<class _OtherIndexType, size_t... _OtherExtents>
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friend constexpr bool operator==(const extents&,
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const extents<_OtherIndexType, _OtherExtents...>&) noexcept;
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private:
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// libcxx note: we do not use an array here, but we need to preserve the as-if behavior
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// for example the default constructor must zero initialize dynamic extents
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array<index_type, rank_dynamic()> dynamic-extents{}; // exposition only
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};
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template<class... Integrals>
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explicit extents(Integrals...)
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-> see below;
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}
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*/
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#ifndef _LIBCPP_MDSPAN
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#define _LIBCPP_MDSPAN
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#include <__config>
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#include <__mdspan/extents.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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#endif // _LIBCPP_MDSPAN
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