[clang] Adding Separate OpenMP Offloading Backend to `libcxx/include/__algorithm/pstl_backends` (PR #66968)

[Louis Dionne via cfe-commits]

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@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_PSTL_BACKENDS_OPENMP_BACKEND_ANY_OF_H
+#define _LIBCPP___ALGORITHM_PSTL_BACKENDS_OPENMP_BACKEND_ANY_OF_H
+
+#include <__algorithm/any_of.h>
+#include <__algorithm/pstl_backends/cpu_backends/backend.h>
+#include <__algorithm/pstl_backends/openmp/backend.h>
+#include <__config>
+#include <__type_traits/is_execution_policy.h>
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _ExecutionPolicy, class _ForwardIterator, class _Predicate>
+_LIBCPP_HIDE_FROM_ABI bool
+__pstl_any_of(__omp_backend_tag, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
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ldionne wrote:

You should look at the updated documentation for backend functions in `libcxx/include/__algorithm/pstl_backend.h`. They now return `optional`.

The `optional`s are used to represent whether the implementation failed to run the algorithm due to a setup issue. For example in the CPU backends we sometimes need to allocate memory and that can fail. When that fails, we return an empty optional and the front-end of the PSTL will then throw `std::bad_alloc` for us.

In your case I think there's nothing that can throw or fail so far, so you should always return an engaged optional.

https://github.com/llvm/llvm-project/pull/66968