1 files changed, 33 insertions, 4 deletions

diff --git a/contrib/llvm-project/libcxx/include/__algorithm/pstl_merge.h b/contrib/llvm-project/libcxx/include/__algorithm/pstl_merge.h
index f10ac7674282..ed8014510863 100644
--- a/contrib/llvm-project/libcxx/include/__algorithm/pstl_merge.h
+++ b/contrib/llvm-project/libcxx/include/__algorithm/pstl_merge.h
@@ -16,6 +16,7 @@
 #include <__type_traits/is_execution_policy.h>
 #include <__type_traits/remove_cvref.h>
 #include <__utility/move.h>
+#include <optional>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -32,23 +33,51 @@ template <class _ExecutionPolicy,
           class _Comp                                         = std::less<>,
           class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
           enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
+__merge(_ExecutionPolicy&&,
+        _ForwardIterator1 __first1,
+        _ForwardIterator1 __last1,
+        _ForwardIterator2 __first2,
+        _ForwardIterator2 __last2,
+        _ForwardOutIterator __result,
+        _Comp __comp = {}) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_merge<_RawPolicy>(
+      _Backend{},
+      std::move(__first1),
+      std::move(__last1),
+      std::move(__first2),
+      std::move(__last2),
+      std::move(__result),
+      std::move(__comp));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _ForwardOutIterator,
+          class _Comp                                         = std::less<>,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
 _LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
-merge(_ExecutionPolicy&&,
+merge(_ExecutionPolicy&& __policy,
       _ForwardIterator1 __first1,
       _ForwardIterator1 __last1,
       _ForwardIterator2 __first2,
       _ForwardIterator2 __last2,
       _ForwardOutIterator __result,
       _Comp __comp = {}) {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_merge<_RawPolicy>(
-      _Backend{},
+  auto __res = std::__merge(
+      __policy,
       std::move(__first1),
       std::move(__last1),
       std::move(__first2),
       std::move(__last2),
       std::move(__result),
       std::move(__comp));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
 }
 
 _LIBCPP_END_NAMESPACE_STD