[libcxx-commits] [libcxx] [libc++] Implement P2897R7 aligned_accessor: An mdspan accessor expressing pointer over-alignment (PR #122603)

[Damien L-G via libcxx-commits]

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@@ -0,0 +1,68 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <mdspan>
+
+// constexpr reference access(data_handle_type p, size_t i) const noexcept;
+//
+// Effects: Equivalent to: return assume_aligned<byte_alignment>(p)[i];
+
+#include <mdspan>
+#include <cassert>
+#include <cstdint>
+#include <concepts>
+#include <type_traits>
+
+#include "test_macros.h"
+
+#include "../MinimalElementType.h"
+
+template <class T, size_t N>
+constexpr void test_access() {
+  ElementPool<std::remove_const_t<T>, 10 + N> data;
+  T* ptr = data.get_ptr();
+  // align ptr
+  for (size_t i = 0; i < N; ++i) {
+    if (reinterpret_cast<std::uintptr_t>(ptr + i) % N == 0) {
+      ptr += i;
+      break;
+    }
+  }
+  std::aligned_accessor<T, N> acc;
+  for (size_t i = 0; i < 10; ++i) {
+    std::same_as<typename std::aligned_accessor<T, N>::reference> decltype(auto) x = acc.access(ptr, i);
+    ASSERT_NOEXCEPT(acc.access(ptr, i));
+    assert(&x == ptr + i);
+  }
+}
+
+template <class T>
+constexpr void test_it() {
+  constexpr size_t N = alignof(T);
+  test_access<T, N>();
+  test_access<T, 2 * N>();
+  test_access<T, 4 * N>();
+  test_access<T, 8 * N>();
+  test_access<T, 16 * N>();
+}
+
+constexpr bool test() {
+  test_it<int>();
+  test_it<const int>();
+  test_it<MinimalElementType>();
+  test_it<const MinimalElementType>();
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  //static_assert(test());
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dalg24 wrote:

Fixed.

https://github.com/llvm/llvm-project/pull/122603