[libc++] <experimental/simd> Add ++/-- operators for simd reference

libcxx/docs/Status/ParallelismProjects.csv

@@ -18,6 +18,7 @@ Section,Description,Dependencies,Assignee,Complete
 | `[parallel.simd.reference] <https://wg21.link/N4808>`_, "`Element references operator= <https://github.com/llvm/llvm-project/pull/70020>`_", None, Yin Zhang, |Complete|
 | `[parallel.simd.reference] <https://wg21.link/N4808>`_, "`Element references swap functions <https://github.com/llvm/llvm-project/pull/86478>`_", None, Yin Zhang, |Complete|
 | `[parallel.simd.reference] <https://wg21.link/N4808>`_, "`Element references compound assignment operators <https://github.com/llvm/llvm-project/pull/86761>`_", None, Yin Zhang, |Complete|
+| `[parallel.simd.reference] <https://wg21.link/N4808>`_, "`Element references unary operators ++/-- <https://github.com/llvm/llvm-project/pull/88091>`_", None, Yin Zhang, |Complete|
 | `[parallel.simd.class] <https://wg21.link/N4808>`_, "`Class template simd declaration and alias <https://reviews.llvm.org/D144362>`_", [parallel.simd.abi], Yin Zhang, |Complete|
 | `[parallel.simd.class] <https://wg21.link/N4808>`_, "`simd<>::size() <https://reviews.llvm.org/D144363>`_", [parallel.simd.traits] simd_size[_v], Yin Zhang, |Complete|
 | `[parallel.simd.class] <https://wg21.link/N4808>`_, "`simd default constructor <https://github.com/llvm/llvm-project/pull/70424>`_", None, Yin Zhang, |Complete|

libcxx/include/experimental/__simd/reference.h

@@ -132,6 +132,31 @@ class __simd_reference {
     __set(__get() >> static_cast<value_type>(std::forward<_Up>(__v)));
     return {__s_, __idx_};
   }
+
+  // Note: All legal vectorizable types support operator++/--.
+  // There doesn't seem to be a way to trigger the constraint.
+  // Therefore, no SFINAE check is added here.
+  __simd_reference _LIBCPP_HIDE_FROM_ABI operator++() && noexcept {
+    __set(__get() + 1);
+    return {__s_, __idx_};
+  }
+
+  value_type _LIBCPP_HIDE_FROM_ABI operator++(int) && noexcept {
+    auto __r = __get();
+    __set(__get() + 1);
+    return __r;
+  }
+
+  __simd_reference _LIBCPP_HIDE_FROM_ABI operator--() && noexcept {
+    __set(__get() - 1);
+    return {__s_, __idx_};
+  }
+
+  value_type _LIBCPP_HIDE_FROM_ABI operator--(int) && noexcept {
+    auto __r = __get();
+    __set(__get() - 1);
+    return __r;
+  }
 };
 
 template <class _Tp, class _Storage, class _Vp>

libcxx/test/std/experimental/simd/simd.reference/reference_unary.pass.cpp

@@ -0,0 +1,43 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <experimental/simd>
+//
+// [simd.reference]
+// reference operator++() && noexcept;
+// value_type operator++(int) && noexcept;
+// reference operator--() && noexcept;
+// value_type operator--(int) && noexcept;
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+
+template <class T, std::size_t>
+struct CheckSimdReferenceUnaryOperators {
+  template <class SimdAbi>
+  void operator()() const {
+    ex::simd<T, SimdAbi> origin_simd(static_cast<T>(3));
+    static_assert(noexcept(++origin_simd[0]));
+    assert(((T)(++origin_simd[0]) == static_cast<T>(4)) && ((T)origin_simd[0] == static_cast<T>(4)));
+    static_assert(noexcept(origin_simd[0]++));
+    assert(((T)(origin_simd[0]++) == static_cast<T>(4)) && ((T)origin_simd[0] == static_cast<T>(5)));
+    static_assert(noexcept(--origin_simd[0]));
+    assert(((T)(--origin_simd[0]) == static_cast<T>(4)) && ((T)origin_simd[0] == static_cast<T>(4)));
+    static_assert(noexcept(origin_simd[0]--));
+    assert(((T)(origin_simd[0]--) == static_cast<T>(4)) && ((T)origin_simd[0] == static_cast<T>(3)));
+  }
+};
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdReferenceUnaryOperators>();
+  return 0;
+}