Host/Device accessors for mdspan

libcudacxx/include/cuda/__mdspan/host_device_accessor.h

@@ -0,0 +1,148 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of libcu++, the C++ Standard Library for your entire system,
+// under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+// SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _CUDA___MDSPAN_HOST_DEVICE_ACCESSOR
+#define _CUDA___MDSPAN_HOST_DEVICE_ACCESSOR
+
+#include <cuda/std/detail/__config>
+
+#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
+#  pragma GCC system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
+#  pragma clang system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
+#  pragma system_header
+#endif // no system header
+
+_LIBCUDACXX_BEGIN_NAMESPACE_CUDA
+
+template <typename _Accessor>
+struct host_accessor;
+
+template <typename _Accessor>
+struct device_accessor;
+
+template <typename _Accessor>
+struct managed_accessor;
+
+/***********************************************************************************************************************
+ * Host/Device/Managed Accessor Traits
+ **********************************************************************************************************************/
+
+template <typename T>
+inline constexpr bool is_host_accessor_v = false;
+
+template <typename T>
+inline constexpr bool is_device_accessor_v = false;
+
+template <typename T>
+inline constexpr bool is_managed_accessor_v = false;
+
+template <typename _Accessor>
+inline constexpr bool is_host_accessor_v<host_accessor<_Accessor>> = true;
+
+template <typename _Accessor>
+inline constexpr bool is_device_accessor_v<device_accessor<_Accessor>> = true;
+
+template <typename _Accessor>
+inline constexpr bool is_managed_accessor_v<managed_accessor<_Accessor>> = true;
+
+template <typename T>
+inline constexpr bool is_host_device_managed_accessor_v =
+  is_host_accessor_v<T> || is_device_accessor_v<T> || is_managed_accessor_v<T>;
+
+/***********************************************************************************************************************
+ * Host Accessor
+ **********************************************************************************************************************/
+
+template <typename _Accessor>
+struct host_accessor : public _Accessor
+{
+private:
+  static constexpr bool __is_ctor_noexcept      = noexcept(_Accessor{});
+  static constexpr bool __is_copy_ctor_noexcept = noexcept(_Accessor{});
+
+  static_assert(!is_host_device_managed_accessor_v<_Accessor>, "Host/Device/Managed accessor cannot be nested");
+
+public:
+  using offset_policy = host_accessor;
+
+  constexpr host_accessor() noexcept(__is_ctor_noexcept) = default;
+
+  constexpr host_accessor(const host_accessor&) noexcept(__is_copy_ctor_noexcept) = default;
+};
+
+/***********************************************************************************************************************
+ * Device Accessor
+ **********************************************************************************************************************/
+
+template <typename _Accessor>
+struct device_accessor : public _Accessor
+{
+private:
+  static constexpr bool __is_ctor_noexcept      = noexcept(_Accessor{});
+  static constexpr bool __is_copy_ctor_noexcept = noexcept(_Accessor{});
+
+  static_assert(!is_host_device_managed_accessor_v<_Accessor>, "Host/Device/Managed accessor cannot be nested");
+
+public:
+  using offset_policy = device_accessor;
+
+  constexpr device_accessor() noexcept(__is_ctor_noexcept) = default;
+
+  constexpr device_accessor(const device_accessor&) noexcept(__is_copy_ctor_noexcept) = default;
+};
+
+/***********************************************************************************************************************
+ * Managed Accessor
+ **********************************************************************************************************************/
+
+template <typename _Accessor>
+struct managed_accessor : public _Accessor
+{
+private:
+  static constexpr bool __is_ctor_noexcept      = noexcept(_Accessor{});
+  static constexpr bool __is_copy_ctor_noexcept = noexcept(_Accessor{});
+
+  static_assert(!is_host_device_managed_accessor_v<_Accessor>, "Host/Device/Managed accessor cannot be nested");
+
+public:
+  using offset_policy = managed_accessor;
+
+  constexpr managed_accessor() noexcept(__is_ctor_noexcept) = default;
+
+  constexpr managed_accessor(const managed_accessor&) noexcept(__is_copy_ctor_noexcept) = default;
+};
+
+/***********************************************************************************************************************
+ * Accessibility Traits
+ **********************************************************************************************************************/
+
+template <typename T>
+inline constexpr bool is_host_accessible_v = false;
+
+template <typename T>
+inline constexpr bool is_device_accessible_v = false;
+
+template <typename _Accessor>
+inline constexpr bool is_host_accessible_v<host_accessor<_Accessor>> = true;
+
+template <typename _Accessor>
+inline constexpr bool is_host_accessible_v<managed_accessor<_Accessor>> = true;
+
+template <typename _Accessor>
+inline constexpr bool is_device_accessible_v<device_accessor<_Accessor>> = true;
+
+template <typename _Accessor>
+inline constexpr bool is_device_accessible_v<managed_accessor<_Accessor>> = true;
+
+_LIBCUDACXX_END_NAMESPACE_CUDA
+
+#endif // _CUDA___MDSPAN_HOST_DEVICE_ACCESSOR

libcudacxx/include/cuda/__mdspan/host_device_mdspan.h

@@ -0,0 +1,59 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of libcu++, the C++ Standard Library for your entire system,
+// under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+// SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _CUDA___MDSPAN_HOST_DEVICE_MDSPAN
+#define _CUDA___MDSPAN_HOST_DEVICE_MDSPAN
+
+#include <cuda/std/detail/__config>
+
+#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
+#  pragma GCC system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
+#  pragma clang system_header
+#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
+#  pragma system_header
+#endif // no system header
+
+#include <cuda/__mdspan/host_device_accessor.h>
+#include <cuda/std/mdspan>
+
+_LIBCUDACXX_BEGIN_NAMESPACE_CUDA
+
+template <typename _ElementType,
+          typename _Extents,
+          typename _LayoutPolicy   = _CUDA_VSTD::layout_right,
+          typename _AccessorPolicy = _CUDA_VSTD::default_accessor<_ElementType>>
+using host_mdspan = _CUDA_VSTD::mdspan<_ElementType, _Extents, _LayoutPolicy, host_accessor<_AccessorPolicy>>;
+
+template <typename _ElementType,
+          typename _Extents,
+          typename _LayoutPolicy   = _CUDA_VSTD::layout_right,
+          typename _AccessorPolicy = _CUDA_VSTD::default_accessor<_ElementType>>
+using device_mdspan = _CUDA_VSTD::mdspan<_ElementType, _Extents, _LayoutPolicy, device_accessor<_AccessorPolicy>>;
+
+template <typename _ElementType,
+          typename _Extents,
+          typename _LayoutPolicy   = _CUDA_VSTD::layout_right,
+          typename _AccessorPolicy = _CUDA_VSTD::default_accessor<_ElementType>>
+using managed_mdspan = _CUDA_VSTD::mdspan<_ElementType, _Extents, _LayoutPolicy, managed_accessor<_AccessorPolicy>>;
+
+/***********************************************************************************************************************
+ * Accessibility Traits
+ **********************************************************************************************************************/
+
+template <typename _T, typename _E, typename _L, typename _A>
+inline constexpr bool is_host_accessible_v<_CUDA_VSTD::mdspan<_T, _E, _L, _A>> = is_host_accessible_v<_A>;
+
+template <typename _T, typename _E, typename _L, typename _A>
+inline constexpr bool is_device_accessible_v<_CUDA_VSTD::mdspan<_T, _E, _L, _A>> = is_device_accessible_v<_A>;
+
+_LIBCUDACXX_END_NAMESPACE_CUDA
+
+#endif // _CUDA___MDSPAN_HOST_DEVICE_MDSPAN