1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 // Kokkos v. 4.0 9 // Copyright (2022) National Technology & Engineering 10 // Solutions of Sandia, LLC (NTESS). 11 // 12 // Under the terms of Contract DE-NA0003525 with NTESS, 13 // the U.S. Government retains certain rights in this software. 14 // 15 //===---------------------------------------------------------------------===// 16 17 #ifndef _LIBCPP___MDSPAN_LAYOUT_RIGHT_H 18 #define _LIBCPP___MDSPAN_LAYOUT_RIGHT_H 19 20 #include <__assert> 21 #include <__config> 22 #include <__fwd/mdspan.h> 23 #include <__mdspan/extents.h> 24 #include <__type_traits/is_constructible.h> 25 #include <__type_traits/is_convertible.h> 26 #include <__type_traits/is_nothrow_constructible.h> 27 #include <__utility/integer_sequence.h> 28 #include <cinttypes> 29 #include <cstddef> 30 #include <limits> 31 32 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 33 # pragma GCC system_header 34 #endif 35 36 _LIBCPP_PUSH_MACROS 37 #include <__undef_macros> 38 39 _LIBCPP_BEGIN_NAMESPACE_STD 40 41 #if _LIBCPP_STD_VER >= 23 42 43 template <class _Extents> 44 class layout_right::mapping { 45 public: 46 static_assert(__mdspan_detail::__is_extents<_Extents>::value, 47 "layout_right::mapping template argument must be a specialization of extents."); 48 49 using extents_type = _Extents; 50 using index_type = typename extents_type::index_type; 51 using size_type = typename extents_type::size_type; 52 using rank_type = typename extents_type::rank_type; 53 using layout_type = layout_right; 54 55 private: 56 _LIBCPP_HIDE_FROM_ABI static constexpr bool __required_span_size_is_representable(const extents_type& __ext) { 57 if constexpr (extents_type::rank() == 0) 58 return true; 59 60 index_type __prod = __ext.extent(0); 61 for (rank_type __r = 1; __r < extents_type::rank(); __r++) { 62 bool __overflowed = __builtin_mul_overflow(__prod, __ext.extent(__r), &__prod); 63 if (__overflowed) 64 return false; 65 } 66 return true; 67 } 68 69 static_assert((extents_type::rank_dynamic() > 0) || __required_span_size_is_representable(extents_type()), 70 "layout_right::mapping product of static extents must be representable as index_type."); 71 72 public: 73 // [mdspan.layout.right.cons], constructors 74 _LIBCPP_HIDE_FROM_ABI constexpr mapping() noexcept = default; 75 _LIBCPP_HIDE_FROM_ABI constexpr mapping(const mapping&) noexcept = default; 76 _LIBCPP_HIDE_FROM_ABI constexpr mapping(const extents_type& __ext) noexcept : __extents_(__ext) { 77 // not catching this could lead to out-of-bounds access later when used inside mdspan 78 // mapping<dextents<char, 2>> map(dextents<char, 2>(40,40)); map(3, 10) == -126 79 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 80 __required_span_size_is_representable(__ext), 81 "layout_right::mapping extents ctor: product of extents must be representable as index_type."); 82 } 83 84 template <class _OtherExtents> 85 requires(is_constructible_v<extents_type, _OtherExtents>) 86 _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>) 87 mapping(const mapping<_OtherExtents>& __other) noexcept 88 : __extents_(__other.extents()) { 89 // not catching this could lead to out-of-bounds access later when used inside mdspan 90 // mapping<dextents<char, 2>> map(mapping<dextents<int, 2>>(dextents<int, 2>(40,40))); map(3, 10) == -126 91 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 92 __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()), 93 "layout_right::mapping converting ctor: other.required_span_size() must be representable as index_type."); 94 } 95 96 template <class _OtherExtents> 97 requires(is_constructible_v<extents_type, _OtherExtents> && _OtherExtents::rank() <= 1) 98 _LIBCPP_HIDE_FROM_ABI constexpr explicit(!is_convertible_v<_OtherExtents, extents_type>) 99 mapping(const layout_left::mapping<_OtherExtents>& __other) noexcept 100 : __extents_(__other.extents()) { 101 // not catching this could lead to out-of-bounds access later when used inside mdspan 102 // Note: since this is constraint to rank 1, extents itself would catch the invalid conversion first 103 // and thus this assertion should never be triggered, but keeping it here for consistency 104 // layout_right::mapping<dextents<char, 1>> map( 105 // layout_left::mapping<dextents<unsigned, 1>>(dextents<unsigned, 1>(200))); map.extents().extent(0) == 106 // -56 107 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 108 __mdspan_detail::__is_representable_as<index_type>(__other.required_span_size()), 109 "layout_right::mapping converting ctor: other.required_span_size() must be representable as index_type."); 110 } 111 112 // FIXME: add when we add other layouts 113 # if 0 114 template<class _OtherExtents> 115 constexpr explicit(extents_type::rank() > 0) 116 mapping(const layout_stride::mapping_<OtherExtents>&) noexcept; 117 # endif 118 119 _LIBCPP_HIDE_FROM_ABI constexpr mapping& operator=(const mapping&) noexcept = default; 120 121 // [mdspan.layout.right.obs], observers 122 _LIBCPP_HIDE_FROM_ABI constexpr const extents_type& extents() const noexcept { return __extents_; } 123 124 _LIBCPP_HIDE_FROM_ABI constexpr index_type required_span_size() const noexcept { 125 index_type __size = 1; 126 for (size_t __r = 0; __r < extents_type::rank(); __r++) 127 __size *= __extents_.extent(__r); 128 return __size; 129 } 130 131 template <class... _Indices> 132 requires((sizeof...(_Indices) == extents_type::rank()) && (is_convertible_v<_Indices, index_type> && ...) && 133 (is_nothrow_constructible_v<index_type, _Indices> && ...)) 134 _LIBCPP_HIDE_FROM_ABI constexpr index_type operator()(_Indices... __idx) const noexcept { 135 // Mappings are generally meant to be used for accessing allocations and are meant to guarantee to never 136 // return a value exceeding required_span_size(), which is used to know how large an allocation one needs 137 // Thus, this is a canonical point in multi-dimensional data structures to make invalid element access checks 138 // However, mdspan does check this on its own, so for now we avoid double checking in hardened mode 139 _LIBCPP_ASSERT(__mdspan_detail::__is_multidimensional_index_in(__extents_, __idx...), 140 "layout_right::mapping: out of bounds indexing"); 141 return [&]<size_t... _Pos>(index_sequence<_Pos...>) { 142 index_type __res = 0; 143 ((__res = static_cast<index_type>(__idx) + __extents_.extent(_Pos) * __res), ...); 144 return __res; 145 }(make_index_sequence<sizeof...(_Indices)>()); 146 } 147 148 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_always_unique() noexcept { return true; } 149 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_always_exhaustive() noexcept { return true; } 150 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_always_strided() noexcept { return true; } 151 152 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_unique() noexcept { return true; } 153 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_exhaustive() noexcept { return true; } 154 _LIBCPP_HIDE_FROM_ABI static constexpr bool is_strided() noexcept { return true; } 155 156 _LIBCPP_HIDE_FROM_ABI constexpr index_type stride(rank_type __r) const noexcept 157 requires(extents_type::rank() > 0) 158 { 159 // While it would be caught by extents itself too, using a too large __r 160 // is functionally an out of bounds access on the stored information needed to compute strides 161 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 162 __r < extents_type::rank(), "layout_right::mapping::stride(): invalid rank index"); 163 index_type __s = 1; 164 for (rank_type __i = extents_type::rank() - 1; __i > __r; __i--) 165 __s *= __extents_.extent(__i); 166 return __s; 167 } 168 169 template <class _OtherExtents> 170 requires(_OtherExtents::rank() == extents_type::rank()) 171 _LIBCPP_HIDE_FROM_ABI friend constexpr bool 172 operator==(const mapping& __lhs, const mapping<_OtherExtents>& __rhs) noexcept { 173 return __lhs.extents() == __rhs.extents(); 174 } 175 176 private: 177 _LIBCPP_NO_UNIQUE_ADDRESS extents_type __extents_{}; 178 }; 179 180 #endif // _LIBCPP_STD_VER >= 23 181 182 _LIBCPP_END_NAMESPACE_STD 183 184 _LIBCPP_POP_MACROS 185 186 #endif // _LIBCPP___MDSPAN_LAYOUT_RIGHT_H 187