[libcxx-commits] [libcxx] [libc++][pstl] Merge all frontend functions for the PSTL (PR #89219)

Louis Dionne via libcxx-commits libcxx-commits at lists.llvm.org
Thu Apr 18 05:21:09 PDT 2024


https://github.com/ldionne updated https://github.com/llvm/llvm-project/pull/89219

>From c637c6711b51efc2d04ac0d448fa35d834a55737 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Wed, 17 Apr 2024 12:13:36 -0400
Subject: [PATCH 1/2] [libc++][pstl] Merge all frontend functions for the PSTL

This is an intermediate step towards the PSTL dispatching mechanism
rework. It will make it a lot easier to track the upcoming front-end
changes. After the rework, there are basically no implementation details
in the front-end, so the definition of each algorithm will become much
simpler. Otherwise, it wouldn't make sense to define all the algorithms
in the same header.
---
 libcxx/include/CMakeLists.txt                 |   20 +-
 libcxx/include/__algorithm/pstl.h             | 1353 +++++++++++++++++
 .../__algorithm/pstl_any_all_none_of.h        |  152 --
 libcxx/include/__algorithm/pstl_copy.h        |  134 --
 libcxx/include/__algorithm/pstl_count.h       |  126 --
 libcxx/include/__algorithm/pstl_equal.h       |  184 ---
 libcxx/include/__algorithm/pstl_fill.h        |  114 --
 libcxx/include/__algorithm/pstl_find.h        |  141 --
 libcxx/include/__algorithm/pstl_for_each.h    |  108 --
 libcxx/include/__algorithm/pstl_generate.h    |  113 --
 .../include/__algorithm/pstl_is_partitioned.h |   79 -
 libcxx/include/__algorithm/pstl_merge.h       |   97 --
 libcxx/include/__algorithm/pstl_move.h        |   89 --
 libcxx/include/__algorithm/pstl_replace.h     |  260 ----
 libcxx/include/__algorithm/pstl_rotate_copy.h |   90 --
 libcxx/include/__algorithm/pstl_sort.h        |   85 --
 libcxx/include/__algorithm/pstl_stable_sort.h |   63 -
 libcxx/include/__algorithm/pstl_transform.h   |  122 --
 .../{pstl_transform_reduce.h => pstl.h}       |   84 +-
 libcxx/include/__numeric/pstl_reduce.h        |  112 --
 libcxx/include/module.modulemap               |   30 +-
 21 files changed, 1440 insertions(+), 2116 deletions(-)
 create mode 100644 libcxx/include/__algorithm/pstl.h
 delete mode 100644 libcxx/include/__algorithm/pstl_any_all_none_of.h
 delete mode 100644 libcxx/include/__algorithm/pstl_copy.h
 delete mode 100644 libcxx/include/__algorithm/pstl_count.h
 delete mode 100644 libcxx/include/__algorithm/pstl_equal.h
 delete mode 100644 libcxx/include/__algorithm/pstl_fill.h
 delete mode 100644 libcxx/include/__algorithm/pstl_find.h
 delete mode 100644 libcxx/include/__algorithm/pstl_for_each.h
 delete mode 100644 libcxx/include/__algorithm/pstl_generate.h
 delete mode 100644 libcxx/include/__algorithm/pstl_is_partitioned.h
 delete mode 100644 libcxx/include/__algorithm/pstl_merge.h
 delete mode 100644 libcxx/include/__algorithm/pstl_move.h
 delete mode 100644 libcxx/include/__algorithm/pstl_replace.h
 delete mode 100644 libcxx/include/__algorithm/pstl_rotate_copy.h
 delete mode 100644 libcxx/include/__algorithm/pstl_sort.h
 delete mode 100644 libcxx/include/__algorithm/pstl_stable_sort.h
 delete mode 100644 libcxx/include/__algorithm/pstl_transform.h
 rename libcxx/include/__numeric/{pstl_transform_reduce.h => pstl.h} (61%)
 delete mode 100644 libcxx/include/__numeric/pstl_reduce.h

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index dc364cc8d0a226..2278290617bd14 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -72,23 +72,8 @@ set(files
   __algorithm/partition_point.h
   __algorithm/pop_heap.h
   __algorithm/prev_permutation.h
-  __algorithm/pstl_any_all_none_of.h
-  __algorithm/pstl_copy.h
-  __algorithm/pstl_count.h
-  __algorithm/pstl_equal.h
-  __algorithm/pstl_fill.h
-  __algorithm/pstl_find.h
-  __algorithm/pstl_for_each.h
   __algorithm/pstl_frontend_dispatch.h
-  __algorithm/pstl_generate.h
-  __algorithm/pstl_is_partitioned.h
-  __algorithm/pstl_merge.h
-  __algorithm/pstl_move.h
-  __algorithm/pstl_replace.h
-  __algorithm/pstl_rotate_copy.h
-  __algorithm/pstl_sort.h
-  __algorithm/pstl_stable_sort.h
-  __algorithm/pstl_transform.h
+  __algorithm/pstl.h
   __algorithm/push_heap.h
   __algorithm/ranges_adjacent_find.h
   __algorithm/ranges_all_of.h
@@ -573,8 +558,7 @@ set(files
   __numeric/iota.h
   __numeric/midpoint.h
   __numeric/partial_sum.h
-  __numeric/pstl_reduce.h
-  __numeric/pstl_transform_reduce.h
+  __numeric/pstl.h
   __numeric/reduce.h
   __numeric/saturation_arithmetic.h
   __numeric/transform_exclusive_scan.h
diff --git a/libcxx/include/__algorithm/pstl.h b/libcxx/include/__algorithm/pstl.h
new file mode 100644
index 00000000000000..748237def0dbc4
--- /dev/null
+++ b/libcxx/include/__algorithm/pstl.h
@@ -0,0 +1,1353 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_H
+#define _LIBCPP___ALGORITHM_PSTL_H
+
+#include <__algorithm/copy_n.h>
+#include <__algorithm/count.h>
+#include <__algorithm/for_each.h>
+#include <__algorithm/pstl_find.h>
+#include <__algorithm/pstl_for_each.h>
+#include <__algorithm/pstl_frontend_dispatch.h>
+#include <__algorithm/pstl_transform.h>
+#include <__atomic/atomic.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/operations.h>
+#include <__iterator/concepts.h>
+#include <__iterator/cpp17_iterator_concepts.h>
+#include <__iterator/iterator_traits.h>
+#include <__numeric/pstl_transform_reduce.h>
+#include <__pstl/configuration.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_constant_evaluated.h>
+#include <__type_traits/is_execution_policy.h>
+#include <__type_traits/is_trivially_copyable.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
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class>
+void __pstl_any_of(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool> __any_of(
+    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_any_of, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) -> optional<bool> {
+        auto __res = std::__find_if(__policy, __g_first, __g_last, __g_pred);
+        if (!__res)
+          return nullopt;
+        return *__res != __g_last;
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
+any_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "any_of requires a ForwardIterator");
+  auto __res = std::__any_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_all_of(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__all_of(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_all_of, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Pred __g_pred) -> optional<bool> {
+        auto __res = std::__any_of(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __value) {
+          return !__g_pred(__value);
+        });
+        if (!__res)
+          return nullopt;
+        return !*__res;
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
+all_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "all_of requires a ForwardIterator");
+  auto __res = std::__all_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_none_of(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__none_of(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_none_of, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Pred __g_pred) -> optional<bool> {
+        auto __res = std::__any_of(__policy, __g_first, __g_last, __g_pred);
+        if (!__res)
+          return nullopt;
+        return !*__res;
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
+none_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "none_of requires a ForwardIterator");
+  auto __res = std::__none_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+// TODO: Use the std::copy/move shenanigans to forward to std::memmove
+
+template <class>
+void __pstl_copy();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
+__copy(_ExecutionPolicy&& __policy,
+       _ForwardIterator&& __first,
+       _ForwardIterator&& __last,
+       _ForwardOutIterator&& __result) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_copy, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _ForwardOutIterator __g_result) {
+        return std::__transform(__policy, __g_first, __g_last, __g_result, __identity());
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__result));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
+copy(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _ForwardOutIterator __result) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardIterator, "copy(first, last, result) requires [first, last) to be ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardOutIterator, "copy(first, last, result) requires result to be a ForwardIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(*__first), "copy(first, last, result) requires result to be an OutputIterator");
+  auto __res = std::__copy(__policy, std::move(__first), std::move(__last), std::move(__result));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_copy_n();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Size,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> __copy_n(
+    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __n, _ForwardOutIterator&& __result) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_copy_n, _RawPolicy),
+      [&__policy](
+          _ForwardIterator __g_first, _Size __g_n, _ForwardOutIterator __g_result) -> optional<_ForwardIterator> {
+        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value)
+          return std::__copy(__policy, std::move(__g_first), std::move(__g_first + __g_n), std::move(__g_result));
+        else
+          return std::copy_n(__g_first, __g_n, __g_result);
+      },
+      std::move(__first),
+      std::move(__n),
+      std::move(__result));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Size,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
+copy_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _ForwardOutIterator __result) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardIterator, "copy_n(first, n, result) requires first to be a ForwardIterator");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardOutIterator, "copy_n(first, n, result) requires result to be a ForwardIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(*__first), "copy_n(first, n, result) requires result to be an OutputIterator");
+  auto __res = std::__copy_n(__policy, std::move(__first), std::move(__n), std::move(__result));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_count_if(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_diff_t<_ForwardIterator>> __count_if(
+    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
+  using __diff_t = __iter_diff_t<_ForwardIterator>;
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_count_if, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) -> optional<__diff_t> {
+        return std::__transform_reduce(
+            __policy,
+            std::move(__g_first),
+            std::move(__g_last),
+            __diff_t(),
+            std::plus{},
+            [&](__iter_reference<_ForwardIterator> __element) -> bool { return __g_pred(__element); });
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI __iter_diff_t<_ForwardIterator>
+count_if(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardIterator, "count_if(first, last, pred) requires [first, last) to be ForwardIterators");
+  auto __res = std::__count_if(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_count(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_diff_t<_ForwardIterator>>
+__count(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_count, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value)
+          -> optional<__iter_diff_t<_ForwardIterator>> {
+        return std::count_if(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __v) {
+          return __v == __g_value;
+        });
+      },
+      std::move(__first),
+      std::move(__last),
+      __value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI __iter_diff_t<_ForwardIterator>
+count(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
+      _ForwardIterator, "count(first, last, val) requires [first, last) to be ForwardIterators");
+  auto __res = std::__count(__policy, std::move(__first), std::move(__last), __value);
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class>
+void __pstl_equal();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__equal(_ExecutionPolicy&& __policy,
+        _ForwardIterator1&& __first1,
+        _ForwardIterator1&& __last1,
+        _ForwardIterator2&& __first2,
+        _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
+      [&__policy](
+          _ForwardIterator1 __g_first1, _ForwardIterator1 __g_last1, _ForwardIterator2 __g_first2, _Pred __g_pred) {
+        return std::__transform_reduce(
+            __policy,
+            std::move(__g_first1),
+            std::move(__g_last1),
+            std::move(__g_first2),
+            true,
+            std::logical_and{},
+            std::move(__g_pred));
+      },
+      std::move(__first1),
+      std::move(__last1),
+      std::move(__first2),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _Pred __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
+  auto __res = std::__equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
+  return std::equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::equal_to{});
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
+__equal(_ExecutionPolicy&& __policy,
+        _ForwardIterator1&& __first1,
+        _ForwardIterator1&& __last1,
+        _ForwardIterator2&& __first2,
+        _ForwardIterator2&& __last2,
+        _Pred&& __pred) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
+      [&__policy](_ForwardIterator1 __g_first1,
+                  _ForwardIterator1 __g_last1,
+                  _ForwardIterator2 __g_first2,
+                  _ForwardIterator2 __g_last2,
+                  _Pred __g_pred) -> optional<bool> {
+        if constexpr (__has_random_access_iterator_category<_ForwardIterator1>::value &&
+                      __has_random_access_iterator_category<_ForwardIterator2>::value) {
+          if (__g_last1 - __g_first1 != __g_last2 - __g_first2)
+            return false;
+          return std::__equal(
+              __policy, std::move(__g_first1), std::move(__g_last1), std::move(__g_first2), std::move(__g_pred));
+        } else {
+          (void)__policy; // Avoid unused lambda capture warning
+          return std::equal(
+              std::move(__g_first1),
+              std::move(__g_last1),
+              std::move(__g_first2),
+              std::move(__g_last2),
+              std::move(__g_pred));
+        }
+      },
+      std::move(__first1),
+      std::move(__last1),
+      std::move(__first2),
+      std::move(__last2),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _Pred,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _ForwardIterator2 __last2,
+      _Pred __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
+  auto __res = std::__equal(
+      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI bool
+equal(_ExecutionPolicy&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _ForwardIterator2 __last2) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
+  return std::equal(
+      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::equal_to{});
+}
+
+template <class>
+void __pstl_fill(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI optional<__empty>
+__fill(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_fill, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value) {
+        return std::__for_each(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __element) {
+          __element = __g_value;
+        });
+      },
+      std::move(__first),
+      std::move(__last),
+      __value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+fill(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "fill requires ForwardIterators");
+  if (!std::__fill(__policy, std::move(__first), std::move(__last), __value))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_fill_n(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _SizeT,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__fill_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _SizeT&& __n, const _Tp& __value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_fill_n, _RawPolicy),
+      [&](_ForwardIterator __g_first, _SizeT __g_n, const _Tp& __g_value) {
+        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value)
+          std::fill(__policy, __g_first, __g_first + __g_n, __g_value);
+        else
+          std::fill_n(__g_first, __g_n, __g_value);
+        return optional<__empty>{__empty{}};
+      },
+      std::move(__first),
+      std::move(__n),
+      __value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _SizeT,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+fill_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _SizeT __n, const _Tp& __value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "fill_n requires ForwardIterators");
+  if (!std::__fill_n(__policy, std::move(__first), std::move(__n), __value))
+    std::__throw_bad_alloc();
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
+__find_if(_ExecutionPolicy&&, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_find_if<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardIterator
+find_if(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find_if requires ForwardIterators");
+  auto __res = std::__find_if(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_find_if_not();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
+__find_if_not(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_find_if_not, _RawPolicy),
+      [&](_ForwardIterator&& __g_first, _ForwardIterator&& __g_last, _Predicate&& __g_pred)
+          -> optional<__remove_cvref_t<_ForwardIterator>> {
+        return std::__find_if(
+            __policy, __g_first, __g_last, [&](__iter_reference<__remove_cvref_t<_ForwardIterator>> __value) {
+              return !__g_pred(__value);
+            });
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardIterator
+find_if_not(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find_if_not requires ForwardIterators");
+  auto __res = std::__find_if_not(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class>
+void __pstl_find();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
+__find(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_find, _RawPolicy),
+      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value) -> optional<_ForwardIterator> {
+        return std::find_if(
+            __policy, __g_first, __g_last, [&](__iter_reference<__remove_cvref_t<_ForwardIterator>> __element) {
+              return __element == __g_value;
+            });
+      },
+      std::move(__first),
+      std::move(__last),
+      __value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardIterator
+find(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find requires ForwardIterators");
+  auto __res = std::__find(__policy, std::move(__first), std::move(__last), __value);
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Function,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__for_each(_ExecutionPolicy&&, _ForwardIterator&& __first, _ForwardIterator&& __last, _Function&& __func) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_for_each<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__func));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Function,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+for_each(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Function __func) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "for_each requires ForwardIterators");
+  if (!std::__for_each(__policy, std::move(__first), std::move(__last), std::move(__func)))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_for_each_n(); // declaration needed for the frontend dispatch below
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Function,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__for_each_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __size, _Function&& __func) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_for_each_n, _RawPolicy),
+      [&](_ForwardIterator __g_first, _Size __g_size, _Function __g_func) -> optional<__empty> {
+        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
+          std::for_each(__policy, std::move(__g_first), __g_first + __g_size, std::move(__g_func));
+          return __empty{};
+        } else {
+          std::for_each_n(std::move(__g_first), __g_size, std::move(__g_func));
+          return __empty{};
+        }
+      },
+      std::move(__first),
+      std::move(__size),
+      std::move(__func));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Function,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+for_each_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __size, _Function __func) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "for_each_n requires a ForwardIterator");
+  auto __res = std::__for_each_n(__policy, std::move(__first), std::move(__size), std::move(__func));
+  if (!__res)
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_generate();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__generate(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Generator&& __gen) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Generator __g_gen) {
+        return std::__for_each(
+            __policy, std::move(__g_first), std::move(__g_last), [&](__iter_reference<_ForwardIterator> __element) {
+              __element = __g_gen();
+            });
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__gen));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+generate(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Generator __gen) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "generate requires ForwardIterators");
+  if (!std::__generate(__policy, std::move(__first), std::move(__last), std::move(__gen)))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_generate_n();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__generate_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __n, _Generator&& __gen) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate_n, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _Size __g_n, _Generator __g_gen) {
+        return std::__for_each_n(
+            __policy, std::move(__g_first), std::move(__g_n), [&](__iter_reference<_ForwardIterator> __element) {
+              __element = __g_gen();
+            });
+      },
+      std::move(__first),
+      __n,
+      std::move(__gen));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+generate_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _Generator __gen) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "generate_n requires a ForwardIterator");
+  if (!std::__generate_n(__policy, std::move(__first), std::move(__n), std::move(__gen)))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_is_partitioned();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool> __is_partitioned(
+    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_is_partitioned, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) {
+        __g_first = std::find_if_not(__policy, __g_first, __g_last, __g_pred);
+        if (__g_first == __g_last)
+          return true;
+        ++__g_first;
+        return std::none_of(__policy, __g_first, __g_last, __g_pred);
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Predicate,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
+is_partitioned(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "is_partitioned requires ForwardIterators");
+  auto __res = std::__is_partitioned(__policy, std::move(__first), std::move(__last), std::move(__pred));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+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>
+[[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&& __policy,
+      _ForwardIterator1 __first1,
+      _ForwardIterator1 __last1,
+      _ForwardIterator2 __first2,
+      _ForwardIterator2 __last2,
+      _ForwardOutIterator __result,
+      _Comp __comp = {}) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "merge requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "merge requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first1), "merge requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first2), "merge requires an OutputIterator");
+  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);
+}
+
+// TODO: Use the std::copy/move shenanigans to forward to std::memmove
+//       Investigate whether we want to still forward to std::transform(policy)
+//       in that case for the execution::par part, or whether we actually want
+//       to run everything serially in that case.
+
+template <class>
+void __pstl_move();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
+__move(_ExecutionPolicy&& __policy,
+       _ForwardIterator&& __first,
+       _ForwardIterator&& __last,
+       _ForwardOutIterator&& __result) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_move, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _ForwardOutIterator __g_result) {
+        return std::__transform(__policy, __g_first, __g_last, __g_result, [](auto&& __v) { return std::move(__v); });
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__result));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
+move(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _ForwardOutIterator __result) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "move requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "move requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(std::move(*__first)), "move requires an OutputIterator");
+  auto __res = std::__move(__policy, std::move(__first), std::move(__last), std::move(__result));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class>
+void __pstl_replace_if();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__replace_if(_ExecutionPolicy&& __policy,
+             _ForwardIterator&& __first,
+             _ForwardIterator&& __last,
+             _Pred&& __pred,
+             const _Tp& __new_value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_if, _RawPolicy),
+      [&__policy](
+          _ForwardIterator&& __g_first, _ForwardIterator&& __g_last, _Pred&& __g_pred, const _Tp& __g_new_value) {
+        std::for_each(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __element) {
+          if (__g_pred(__element))
+            __element = __g_new_value;
+        });
+        return optional<__empty>{__empty{}};
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__pred),
+      __new_value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Pred,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+replace_if(_ExecutionPolicy&& __policy,
+           _ForwardIterator __first,
+           _ForwardIterator __last,
+           _Pred __pred,
+           const _Tp& __new_value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_if requires ForwardIterators");
+  auto __res = std::__replace_if(__policy, std::move(__first), std::move(__last), std::move(__pred), __new_value);
+  if (!__res)
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_replace();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
+__replace(_ExecutionPolicy&& __policy,
+          _ForwardIterator __first,
+          _ForwardIterator __last,
+          const _Tp& __old_value,
+          const _Tp& __new_value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace, _RawPolicy),
+      [&__policy](
+          _ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_old_value, const _Tp& __g_new_value) {
+        return std::__replace_if(
+            __policy,
+            std::move(__g_first),
+            std::move(__g_last),
+            [&](__iter_reference<_ForwardIterator> __element) { return __element == __g_old_value; },
+            __g_new_value);
+      },
+      std::move(__first),
+      std::move(__last),
+      __old_value,
+      __new_value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+replace(_ExecutionPolicy&& __policy,
+        _ForwardIterator __first,
+        _ForwardIterator __last,
+        const _Tp& __old_value,
+        const _Tp& __new_value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace requires ForwardIterators");
+  if (!std::__replace(__policy, std::move(__first), std::move(__last), __old_value, __new_value))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_replace_copy_if();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Pred,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __replace_copy_if(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator&& __first,
+    _ForwardIterator&& __last,
+    _ForwardOutIterator&& __result,
+    _Pred&& __pred,
+    const _Tp& __new_value) {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_copy_if, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first,
+                  _ForwardIterator __g_last,
+                  _ForwardOutIterator __g_result,
+                  _Pred __g_pred,
+                  const _Tp& __g_new_value) -> optional<__empty> {
+        if (!std::__transform(
+                __policy, __g_first, __g_last, __g_result, [&](__iter_reference<_ForwardIterator> __element) {
+                  return __g_pred(__element) ? __g_new_value : __element;
+                }))
+          return nullopt;
+        return __empty{};
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__result),
+      std::move(__pred),
+      __new_value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Pred,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void replace_copy_if(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator __first,
+    _ForwardIterator __last,
+    _ForwardOutIterator __result,
+    _Pred __pred,
+    const _Tp& __new_value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_copy_if requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "replace_copy_if requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(*__first), "replace_copy_if requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, const _Tp&, "replace_copy requires an OutputIterator");
+  if (!std::__replace_copy_if(
+          __policy, std::move(__first), std::move(__last), std::move(__result), std::move(__pred), __new_value))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_replace_copy();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __replace_copy(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator&& __first,
+    _ForwardIterator&& __last,
+    _ForwardOutIterator&& __result,
+    const _Tp& __old_value,
+    const _Tp& __new_value) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_copy, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first,
+                  _ForwardIterator __g_last,
+                  _ForwardOutIterator __g_result,
+                  const _Tp& __g_old_value,
+                  const _Tp& __g_new_value) {
+        return std::__replace_copy_if(
+            __policy,
+            std::move(__g_first),
+            std::move(__g_last),
+            std::move(__g_result),
+            [&](__iter_reference<_ForwardIterator> __element) { return __element == __g_old_value; },
+            __g_new_value);
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__result),
+      __old_value,
+      __new_value);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Tp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void replace_copy(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator __first,
+    _ForwardIterator __last,
+    _ForwardOutIterator __result,
+    const _Tp& __old_value,
+    const _Tp& __new_value) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_copy requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "replace_copy requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(*__first), "replace_copy requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, const _Tp&, "replace_copy requires an OutputIterator");
+  if (!std::__replace_copy(
+          __policy, std::move(__first), std::move(__last), std::move(__result), __old_value, __new_value))
+    std::__throw_bad_alloc();
+}
+
+template <class>
+void __pstl_rotate_copy();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
+__rotate_copy(_ExecutionPolicy&& __policy,
+              _ForwardIterator&& __first,
+              _ForwardIterator&& __middle,
+              _ForwardIterator&& __last,
+              _ForwardOutIterator&& __result) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_rotate_copy, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first,
+                  _ForwardIterator __g_middle,
+                  _ForwardIterator __g_last,
+                  _ForwardOutIterator __g_result) -> optional<_ForwardOutIterator> {
+        auto __result_mid =
+            std::__copy(__policy, _ForwardIterator(__g_middle), std::move(__g_last), std::move(__g_result));
+        if (!__result_mid)
+          return nullopt;
+        return std::__copy(__policy, std::move(__g_first), std::move(__g_middle), *std::move(__result_mid));
+      },
+      std::move(__first),
+      std::move(__middle),
+      std::move(__last),
+      std::move(__result));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator rotate_copy(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator __first,
+    _ForwardIterator __middle,
+    _ForwardIterator __last,
+    _ForwardOutIterator __result) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "rotate_copy requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "rotate_copy requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(*__first), "rotate_copy requires an OutputIterator");
+  auto __res =
+      std::__rotate_copy(__policy, std::move(__first), std::move(__middle), std::move(__last), std::move(__result));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *__res;
+}
+
+template <class>
+void __pstl_sort();
+
+template <class _ExecutionPolicy,
+          class _RandomAccessIterator,
+          class _Comp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __sort(
+    _ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_sort, _RawPolicy),
+      [&__policy](_RandomAccessIterator __g_first, _RandomAccessIterator __g_last, _Comp __g_comp) {
+        std::stable_sort(__policy, std::move(__g_first), std::move(__g_last), std::move(__g_comp));
+        return optional<__empty>{__empty{}};
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__comp));
+}
+
+template <class _ExecutionPolicy,
+          class _RandomAccessIterator,
+          class _Comp,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+sort(_ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) {
+  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "sort requires RandomAccessIterators");
+  if (!std::__sort(__policy, std::move(__first), std::move(__last), std::move(__comp)))
+    std::__throw_bad_alloc();
+}
+
+template <class _ExecutionPolicy,
+          class _RandomAccessIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+sort(_ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last) {
+  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "sort requires RandomAccessIterators");
+  std::sort(std::forward<_ExecutionPolicy>(__policy), std::move(__first), std::move(__last), less{});
+}
+
+template <class _ExecutionPolicy,
+          class _RandomAccessIterator,
+          class _Comp                                         = less<>,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __stable_sort(
+    _ExecutionPolicy&&, _RandomAccessIterator&& __first, _RandomAccessIterator&& __last, _Comp&& __comp = {}) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_stable_sort<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__comp));
+}
+
+template <class _ExecutionPolicy,
+          class _RandomAccessIterator,
+          class _Comp                                         = less<>,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void stable_sort(
+    _ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp = {}) {
+  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "stable_sort requires RandomAccessIterators");
+  if (!std::__stable_sort(__policy, std::move(__first), std::move(__last), std::move(__comp)))
+    std::__throw_bad_alloc();
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _UnaryOperation,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardOutIterator>>
+__transform(_ExecutionPolicy&&,
+            _ForwardIterator&& __first,
+            _ForwardIterator&& __last,
+            _ForwardOutIterator&& __result,
+            _UnaryOperation&& __op) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_transform<_RawPolicy>(
+      _Backend{}, std::move(__first), std::move(__last), std::move(__result), std::move(__op));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _UnaryOperation,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator __first,
+    _ForwardIterator __last,
+    _ForwardOutIterator __result,
+    _UnaryOperation __op) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "transform requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "transform requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(__op(*__first)), "transform requires an OutputIterator");
+  auto __res = std::__transform(__policy, std::move(__first), std::move(__last), std::move(__result), std::move(__op));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _ForwardOutIterator,
+          class _BinaryOperation,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardOutIterator>>
+__transform(_ExecutionPolicy&&,
+            _ForwardIterator1&& __first1,
+            _ForwardIterator1&& __last1,
+            _ForwardIterator2&& __first2,
+            _ForwardOutIterator&& __result,
+            _BinaryOperation&& __op) noexcept {
+  using _Backend = typename __select_backend<_RawPolicy>::type;
+  return std::__pstl_transform<_RawPolicy>(
+      _Backend{}, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__result), std::move(__op));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _ForwardOutIterator,
+          class _BinaryOperation,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
+    _ExecutionPolicy&& __policy,
+    _ForwardIterator1 __first1,
+    _ForwardIterator1 __last1,
+    _ForwardIterator2 __first2,
+    _ForwardOutIterator __result,
+    _BinaryOperation __op) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "transform requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "transform requires ForwardIterators");
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "transform requires an OutputIterator");
+  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
+      _ForwardOutIterator, decltype(__op(*__first1, *__first2)), "transform requires an OutputIterator");
+  auto __res = std::__transform(
+      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__result), std::move(__op));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___ALGORITHM_PSTL_H
diff --git a/libcxx/include/__algorithm/pstl_any_all_none_of.h b/libcxx/include/__algorithm/pstl_any_all_none_of.h
deleted file mode 100644
index 911a7e42b3fa3f..00000000000000
--- a/libcxx/include/__algorithm/pstl_any_all_none_of.h
+++ /dev/null
@@ -1,152 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_ANY_ALL_NONE_OF_H
-#define _LIBCPP___ALGORITHM_PSTL_ANY_ALL_NONE_OF_H
-
-#include <__algorithm/pstl_find.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_any_of(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool> __any_of(
-    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_any_of, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) -> optional<bool> {
-        auto __res = std::__find_if(__policy, __g_first, __g_last, __g_pred);
-        if (!__res)
-          return nullopt;
-        return *__res != __g_last;
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
-any_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "any_of requires a ForwardIterator");
-  auto __res = std::__any_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_all_of(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
-__all_of(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Pred&& __pred) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_all_of, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Pred __g_pred) -> optional<bool> {
-        auto __res = std::__any_of(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __value) {
-          return !__g_pred(__value);
-        });
-        if (!__res)
-          return nullopt;
-        return !*__res;
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
-all_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "all_of requires a ForwardIterator");
-  auto __res = std::__all_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_none_of(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
-__none_of(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Pred&& __pred) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_none_of, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Pred __g_pred) -> optional<bool> {
-        auto __res = std::__any_of(__policy, __g_first, __g_last, __g_pred);
-        if (!__res)
-          return nullopt;
-        return !*__res;
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
-none_of(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Pred __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "none_of requires a ForwardIterator");
-  auto __res = std::__none_of(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_ANY_ALL_NONE_OF_H
diff --git a/libcxx/include/__algorithm/pstl_copy.h b/libcxx/include/__algorithm/pstl_copy.h
deleted file mode 100644
index 0fcea33c3919f0..00000000000000
--- a/libcxx/include/__algorithm/pstl_copy.h
+++ /dev/null
@@ -1,134 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_COPY_H
-#define _LIBCPP___ALGORITHM_PSTL_COPY_H
-
-#include <__algorithm/copy_n.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__algorithm/pstl_transform.h>
-#include <__config>
-#include <__functional/identity.h>
-#include <__iterator/concepts.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#include <__type_traits/is_constant_evaluated.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__type_traits/is_trivially_copyable.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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-// TODO: Use the std::copy/move shenanigans to forward to std::memmove
-
-template <class>
-void __pstl_copy();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
-__copy(_ExecutionPolicy&& __policy,
-       _ForwardIterator&& __first,
-       _ForwardIterator&& __last,
-       _ForwardOutIterator&& __result) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_copy, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _ForwardOutIterator __g_result) {
-        return std::__transform(__policy, __g_first, __g_last, __g_result, __identity());
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__result));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
-copy(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _ForwardOutIterator __result) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardIterator, "copy(first, last, result) requires [first, last) to be ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardOutIterator, "copy(first, last, result) requires result to be a ForwardIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(*__first), "copy(first, last, result) requires result to be an OutputIterator");
-  auto __res = std::__copy(__policy, std::move(__first), std::move(__last), std::move(__result));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_copy_n();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Size,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> __copy_n(
-    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __n, _ForwardOutIterator&& __result) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_copy_n, _RawPolicy),
-      [&__policy](
-          _ForwardIterator __g_first, _Size __g_n, _ForwardOutIterator __g_result) -> optional<_ForwardIterator> {
-        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value)
-          return std::__copy(__policy, std::move(__g_first), std::move(__g_first + __g_n), std::move(__g_result));
-        else
-          return std::copy_n(__g_first, __g_n, __g_result);
-      },
-      std::move(__first),
-      std::move(__n),
-      std::move(__result));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Size,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
-copy_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _ForwardOutIterator __result) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardIterator, "copy_n(first, n, result) requires first to be a ForwardIterator");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardOutIterator, "copy_n(first, n, result) requires result to be a ForwardIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(*__first), "copy_n(first, n, result) requires result to be an OutputIterator");
-  auto __res = std::__copy_n(__policy, std::move(__first), std::move(__n), std::move(__result));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_COPY_H
diff --git a/libcxx/include/__algorithm/pstl_count.h b/libcxx/include/__algorithm/pstl_count.h
deleted file mode 100644
index 64c84d855e4f61..00000000000000
--- a/libcxx/include/__algorithm/pstl_count.h
+++ /dev/null
@@ -1,126 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_COUNT_H
-#define _LIBCPP___ALGORITHM_PSTL_COUNT_H
-
-#include <__algorithm/count.h>
-#include <__algorithm/for_each.h>
-#include <__algorithm/pstl_for_each.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__atomic/atomic.h>
-#include <__config>
-#include <__functional/operations.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__numeric/pstl_transform_reduce.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_count_if(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_diff_t<_ForwardIterator>> __count_if(
-    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
-  using __diff_t = __iter_diff_t<_ForwardIterator>;
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_count_if, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) -> optional<__diff_t> {
-        return std::__transform_reduce(
-            __policy,
-            std::move(__g_first),
-            std::move(__g_last),
-            __diff_t(),
-            std::plus{},
-            [&](__iter_reference<_ForwardIterator> __element) -> bool { return __g_pred(__element); });
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iter_diff_t<_ForwardIterator>
-count_if(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardIterator, "count_if(first, last, pred) requires [first, last) to be ForwardIterators");
-  auto __res = std::__count_if(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_count(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_diff_t<_ForwardIterator>>
-__count(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_count, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value)
-          -> optional<__iter_diff_t<_ForwardIterator>> {
-        return std::count_if(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __v) {
-          return __v == __g_value;
-        });
-      },
-      std::move(__first),
-      std::move(__last),
-      __value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iter_diff_t<_ForwardIterator>
-count(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(
-      _ForwardIterator, "count(first, last, val) requires [first, last) to be ForwardIterators");
-  auto __res = std::__count(__policy, std::move(__first), std::move(__last), __value);
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *__res;
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_COUNT_H
diff --git a/libcxx/include/__algorithm/pstl_equal.h b/libcxx/include/__algorithm/pstl_equal.h
deleted file mode 100644
index 0b38197d7f63df..00000000000000
--- a/libcxx/include/__algorithm/pstl_equal.h
+++ /dev/null
@@ -1,184 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_EQUAL_H
-#define _LIBCPP___ALGORITHM_PSTL_EQUAL_H
-
-#include <__algorithm/equal.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__functional/operations.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__numeric/pstl_transform_reduce.h>
-#include <__utility/move.h>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_equal();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
-__equal(_ExecutionPolicy&& __policy,
-        _ForwardIterator1&& __first1,
-        _ForwardIterator1&& __last1,
-        _ForwardIterator2&& __first2,
-        _Pred&& __pred) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
-      [&__policy](
-          _ForwardIterator1 __g_first1, _ForwardIterator1 __g_last1, _ForwardIterator2 __g_first2, _Pred __g_pred) {
-        return std::__transform_reduce(
-            __policy,
-            std::move(__g_first1),
-            std::move(__g_last1),
-            std::move(__g_first2),
-            true,
-            std::logical_and{},
-            std::move(__g_pred));
-      },
-      std::move(__first1),
-      std::move(__last1),
-      std::move(__first2),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI bool
-equal(_ExecutionPolicy&& __policy,
-      _ForwardIterator1 __first1,
-      _ForwardIterator1 __last1,
-      _ForwardIterator2 __first2,
-      _Pred __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
-  auto __res = std::__equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *__res;
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI bool
-equal(_ExecutionPolicy&& __policy, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
-  return std::equal(__policy, std::move(__first1), std::move(__last1), std::move(__first2), std::equal_to{});
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool>
-__equal(_ExecutionPolicy&& __policy,
-        _ForwardIterator1&& __first1,
-        _ForwardIterator1&& __last1,
-        _ForwardIterator2&& __first2,
-        _ForwardIterator2&& __last2,
-        _Pred&& __pred) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_equal, _RawPolicy),
-      [&__policy](_ForwardIterator1 __g_first1,
-                  _ForwardIterator1 __g_last1,
-                  _ForwardIterator2 __g_first2,
-                  _ForwardIterator2 __g_last2,
-                  _Pred __g_pred) -> optional<bool> {
-        if constexpr (__has_random_access_iterator_category<_ForwardIterator1>::value &&
-                      __has_random_access_iterator_category<_ForwardIterator2>::value) {
-          if (__g_last1 - __g_first1 != __g_last2 - __g_first2)
-            return false;
-          return std::__equal(
-              __policy, std::move(__g_first1), std::move(__g_last1), std::move(__g_first2), std::move(__g_pred));
-        } else {
-          (void)__policy; // Avoid unused lambda capture warning
-          return std::equal(
-              std::move(__g_first1),
-              std::move(__g_last1),
-              std::move(__g_first2),
-              std::move(__g_last2),
-              std::move(__g_pred));
-        }
-      },
-      std::move(__first1),
-      std::move(__last1),
-      std::move(__first2),
-      std::move(__last2),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _Pred,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI bool
-equal(_ExecutionPolicy&& __policy,
-      _ForwardIterator1 __first1,
-      _ForwardIterator1 __last1,
-      _ForwardIterator2 __first2,
-      _ForwardIterator2 __last2,
-      _Pred __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
-  auto __res = std::__equal(
-      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *__res;
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI bool
-equal(_ExecutionPolicy&& __policy,
-      _ForwardIterator1 __first1,
-      _ForwardIterator1 __last1,
-      _ForwardIterator2 __first2,
-      _ForwardIterator2 __last2) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "equal requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "equal requires ForwardIterators");
-  return std::equal(
-      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__last2), std::equal_to{});
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_EQUAL_H
diff --git a/libcxx/include/__algorithm/pstl_fill.h b/libcxx/include/__algorithm/pstl_fill.h
deleted file mode 100644
index fd248506bc4b96..00000000000000
--- a/libcxx/include/__algorithm/pstl_fill.h
+++ /dev/null
@@ -1,114 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_FILL_H
-#define _LIBCPP___ALGORITHM_PSTL_FILL_H
-
-#include <__algorithm/fill_n.h>
-#include <__algorithm/pstl_for_each.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/concepts.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_fill(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI optional<__empty>
-__fill(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_fill, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value) {
-        return std::__for_each(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __element) {
-          __element = __g_value;
-        });
-      },
-      std::move(__first),
-      std::move(__last),
-      __value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-fill(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "fill requires ForwardIterators");
-  if (!std::__fill(__policy, std::move(__first), std::move(__last), __value))
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_fill_n(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _SizeT,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__fill_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _SizeT&& __n, const _Tp& __value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_fill_n, _RawPolicy),
-      [&](_ForwardIterator __g_first, _SizeT __g_n, const _Tp& __g_value) {
-        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value)
-          std::fill(__policy, __g_first, __g_first + __g_n, __g_value);
-        else
-          std::fill_n(__g_first, __g_n, __g_value);
-        return optional<__empty>{__empty{}};
-      },
-      std::move(__first),
-      std::move(__n),
-      __value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _SizeT,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-fill_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _SizeT __n, const _Tp& __value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "fill_n requires ForwardIterators");
-  if (!std::__fill_n(__policy, std::move(__first), std::move(__n), __value))
-    std::__throw_bad_alloc();
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_FILL_H
diff --git a/libcxx/include/__algorithm/pstl_find.h b/libcxx/include/__algorithm/pstl_find.h
deleted file mode 100644
index b4c4dfb2ffb6f6..00000000000000
--- a/libcxx/include/__algorithm/pstl_find.h
+++ /dev/null
@@ -1,141 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_FIND_H
-#define _LIBCPP___ALGORITHM_PSTL_FIND_H
-
-#include <__algorithm/comp.h>
-#include <__algorithm/find.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
-__find_if(_ExecutionPolicy&&, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) noexcept {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_find_if<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardIterator
-find_if(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find_if requires ForwardIterators");
-  auto __res = std::__find_if(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_find_if_not();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
-__find_if_not(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_find_if_not, _RawPolicy),
-      [&](_ForwardIterator&& __g_first, _ForwardIterator&& __g_last, _Predicate&& __g_pred)
-          -> optional<__remove_cvref_t<_ForwardIterator>> {
-        return std::__find_if(
-            __policy, __g_first, __g_last, [&](__iter_reference<__remove_cvref_t<_ForwardIterator>> __value) {
-              return !__g_pred(__value);
-            });
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardIterator
-find_if_not(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find_if_not requires ForwardIterators");
-  auto __res = std::__find_if_not(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class>
-void __pstl_find();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardIterator>>
-__find(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_find, _RawPolicy),
-      [&](_ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_value) -> optional<_ForwardIterator> {
-        return std::find_if(
-            __policy, __g_first, __g_last, [&](__iter_reference<__remove_cvref_t<_ForwardIterator>> __element) {
-              return __element == __g_value;
-            });
-      },
-      std::move(__first),
-      std::move(__last),
-      __value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardIterator
-find(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "find requires ForwardIterators");
-  auto __res = std::__find(__policy, std::move(__first), std::move(__last), __value);
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_FIND_H
diff --git a/libcxx/include/__algorithm/pstl_for_each.h b/libcxx/include/__algorithm/pstl_for_each.h
deleted file mode 100644
index a99eb6d97fd274..00000000000000
--- a/libcxx/include/__algorithm/pstl_for_each.h
+++ /dev/null
@@ -1,108 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_FOR_EACH_H
-#define _LIBCPP___ALGORITHM_PSTL_FOR_EACH_H
-
-#include <__algorithm/for_each.h>
-#include <__algorithm/for_each_n.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/concepts.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__type_traits/remove_cvref.h>
-#include <__type_traits/void_t.h>
-#include <__utility/empty.h>
-#include <__utility/move.h>
-#include <optional>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Function,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__for_each(_ExecutionPolicy&&, _ForwardIterator&& __first, _ForwardIterator&& __last, _Function&& __func) noexcept {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_for_each<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__func));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Function,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-for_each(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Function __func) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "for_each requires ForwardIterators");
-  if (!std::__for_each(__policy, std::move(__first), std::move(__last), std::move(__func)))
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_for_each_n(); // declaration needed for the frontend dispatch below
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Size,
-          class _Function,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__for_each_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __size, _Function&& __func) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_for_each_n, _RawPolicy),
-      [&](_ForwardIterator __g_first, _Size __g_size, _Function __g_func) -> optional<__empty> {
-        if constexpr (__has_random_access_iterator_category_or_concept<_ForwardIterator>::value) {
-          std::for_each(__policy, std::move(__g_first), __g_first + __g_size, std::move(__g_func));
-          return __empty{};
-        } else {
-          std::for_each_n(std::move(__g_first), __g_size, std::move(__g_func));
-          return __empty{};
-        }
-      },
-      std::move(__first),
-      std::move(__size),
-      std::move(__func));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Size,
-          class _Function,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-for_each_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __size, _Function __func) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "for_each_n requires a ForwardIterator");
-  auto __res = std::__for_each_n(__policy, std::move(__first), std::move(__size), std::move(__func));
-  if (!__res)
-    std::__throw_bad_alloc();
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_FOR_EACH_H
diff --git a/libcxx/include/__algorithm/pstl_generate.h b/libcxx/include/__algorithm/pstl_generate.h
deleted file mode 100644
index 350c0e4798be67..00000000000000
--- a/libcxx/include/__algorithm/pstl_generate.h
+++ /dev/null
@@ -1,113 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_GENERATE_H
-#define _LIBCPP___ALGORITHM_PSTL_GENERATE_H
-
-#include <__algorithm/pstl_for_each.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_generate();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Generator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__generate(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Generator&& __gen) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Generator __g_gen) {
-        return std::__for_each(
-            __policy, std::move(__g_first), std::move(__g_last), [&](__iter_reference<_ForwardIterator> __element) {
-              __element = __g_gen();
-            });
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__gen));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Generator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-generate(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Generator __gen) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "generate requires ForwardIterators");
-  if (!std::__generate(__policy, std::move(__first), std::move(__last), std::move(__gen)))
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_generate_n();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Size,
-          class _Generator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__generate_n(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _Size&& __n, _Generator&& __gen) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate_n, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _Size __g_n, _Generator __g_gen) {
-        return std::__for_each_n(
-            __policy, std::move(__g_first), std::move(__g_n), [&](__iter_reference<_ForwardIterator> __element) {
-              __element = __g_gen();
-            });
-      },
-      std::move(__first),
-      __n,
-      std::move(__gen));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Size,
-          class _Generator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-generate_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _Generator __gen) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "generate_n requires a ForwardIterator");
-  if (!std::__generate_n(__policy, std::move(__first), std::move(__n), std::move(__gen)))
-    std::__throw_bad_alloc();
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_GENERATE_H
diff --git a/libcxx/include/__algorithm/pstl_is_partitioned.h b/libcxx/include/__algorithm/pstl_is_partitioned.h
deleted file mode 100644
index c016b388e3784a..00000000000000
--- a/libcxx/include/__algorithm/pstl_is_partitioned.h
+++ /dev/null
@@ -1,79 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_IS_PARITTIONED
-#define _LIBCPP___ALGORITHM_PSTL_IS_PARITTIONED
-
-#include <__algorithm/pstl_any_all_none_of.h>
-#include <__algorithm/pstl_find.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_is_partitioned();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<bool> __is_partitioned(
-    _ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last, _Predicate&& __pred) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_is_partitioned, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Predicate __g_pred) {
-        __g_first = std::find_if_not(__policy, __g_first, __g_last, __g_pred);
-        if (__g_first == __g_last)
-          return true;
-        ++__g_first;
-        return std::none_of(__policy, __g_first, __g_last, __g_pred);
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Predicate,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI bool
-is_partitioned(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Predicate __pred) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "is_partitioned requires ForwardIterators");
-  auto __res = std::__is_partitioned(__policy, std::move(__first), std::move(__last), std::move(__pred));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_IS_PARITTIONED
diff --git a/libcxx/include/__algorithm/pstl_merge.h b/libcxx/include/__algorithm/pstl_merge.h
deleted file mode 100644
index 87f634a67f5889..00000000000000
--- a/libcxx/include/__algorithm/pstl_merge.h
+++ /dev/null
@@ -1,97 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_MERGE_H
-#define _LIBCPP___ALGORITHM_PSTL_MERGE_H
-
-#include <__config>
-#include <__functional/operations.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-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>
-[[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&& __policy,
-      _ForwardIterator1 __first1,
-      _ForwardIterator1 __last1,
-      _ForwardIterator2 __first2,
-      _ForwardIterator2 __last2,
-      _ForwardOutIterator __result,
-      _Comp __comp = {}) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "merge requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "merge requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first1), "merge requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, decltype(*__first2), "merge requires an OutputIterator");
-  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
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_MERGE_H
diff --git a/libcxx/include/__algorithm/pstl_move.h b/libcxx/include/__algorithm/pstl_move.h
deleted file mode 100644
index 3155ddedf91bb6..00000000000000
--- a/libcxx/include/__algorithm/pstl_move.h
+++ /dev/null
@@ -1,89 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_MOVE_H
-#define _LIBCPP___ALGORITHM_PSTL_MOVE_H
-
-#include <__algorithm/copy_n.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__algorithm/pstl_transform.h>
-#include <__config>
-#include <__functional/identity.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#include <__type_traits/is_constant_evaluated.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__type_traits/is_trivially_copyable.h>
-#include <__type_traits/remove_cvref.h>
-#include <optional>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-// TODO: Use the std::copy/move shenanigans to forward to std::memmove
-//       Investigate whether we want to still forward to std::transform(policy)
-//       in that case for the execution::par part, or whether we actually want
-//       to run everything serially in that case.
-
-template <class>
-void __pstl_move();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
-__move(_ExecutionPolicy&& __policy,
-       _ForwardIterator&& __first,
-       _ForwardIterator&& __last,
-       _ForwardOutIterator&& __result) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_move, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _ForwardOutIterator __g_result) {
-        return std::__transform(__policy, __g_first, __g_last, __g_result, [](auto&& __v) { return std::move(__v); });
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__result));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
-move(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _ForwardOutIterator __result) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "move requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "move requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(std::move(*__first)), "move requires an OutputIterator");
-  auto __res = std::__move(__policy, std::move(__first), std::move(__last), std::move(__result));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *__res;
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_MOVE_H
diff --git a/libcxx/include/__algorithm/pstl_replace.h b/libcxx/include/__algorithm/pstl_replace.h
deleted file mode 100644
index b2ded54dfe25f3..00000000000000
--- a/libcxx/include/__algorithm/pstl_replace.h
+++ /dev/null
@@ -1,260 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_REPLACE_H
-#define _LIBCPP___ALGORITHM_PSTL_REPLACE_H
-
-#include <__algorithm/pstl_for_each.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__algorithm/pstl_transform.h>
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_replace_if();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__replace_if(_ExecutionPolicy&& __policy,
-             _ForwardIterator&& __first,
-             _ForwardIterator&& __last,
-             _Pred&& __pred,
-             const _Tp& __new_value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_if, _RawPolicy),
-      [&__policy](
-          _ForwardIterator&& __g_first, _ForwardIterator&& __g_last, _Pred&& __g_pred, const _Tp& __g_new_value) {
-        std::for_each(__policy, __g_first, __g_last, [&](__iter_reference<_ForwardIterator> __element) {
-          if (__g_pred(__element))
-            __element = __g_new_value;
-        });
-        return optional<__empty>{__empty{}};
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__pred),
-      __new_value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Pred,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-replace_if(_ExecutionPolicy&& __policy,
-           _ForwardIterator __first,
-           _ForwardIterator __last,
-           _Pred __pred,
-           const _Tp& __new_value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_if requires ForwardIterators");
-  auto __res = std::__replace_if(__policy, std::move(__first), std::move(__last), std::move(__pred), __new_value);
-  if (!__res)
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_replace();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty>
-__replace(_ExecutionPolicy&& __policy,
-          _ForwardIterator __first,
-          _ForwardIterator __last,
-          const _Tp& __old_value,
-          const _Tp& __new_value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace, _RawPolicy),
-      [&__policy](
-          _ForwardIterator __g_first, _ForwardIterator __g_last, const _Tp& __g_old_value, const _Tp& __g_new_value) {
-        return std::__replace_if(
-            __policy,
-            std::move(__g_first),
-            std::move(__g_last),
-            [&](__iter_reference<_ForwardIterator> __element) { return __element == __g_old_value; },
-            __g_new_value);
-      },
-      std::move(__first),
-      std::move(__last),
-      __old_value,
-      __new_value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-replace(_ExecutionPolicy&& __policy,
-        _ForwardIterator __first,
-        _ForwardIterator __last,
-        const _Tp& __old_value,
-        const _Tp& __new_value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace requires ForwardIterators");
-  if (!std::__replace(__policy, std::move(__first), std::move(__last), __old_value, __new_value))
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_replace_copy_if();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Pred,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __replace_copy_if(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator&& __first,
-    _ForwardIterator&& __last,
-    _ForwardOutIterator&& __result,
-    _Pred&& __pred,
-    const _Tp& __new_value) {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_copy_if, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first,
-                  _ForwardIterator __g_last,
-                  _ForwardOutIterator __g_result,
-                  _Pred __g_pred,
-                  const _Tp& __g_new_value) -> optional<__empty> {
-        if (!std::__transform(
-                __policy, __g_first, __g_last, __g_result, [&](__iter_reference<_ForwardIterator> __element) {
-                  return __g_pred(__element) ? __g_new_value : __element;
-                }))
-          return nullopt;
-        return __empty{};
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__result),
-      std::move(__pred),
-      __new_value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Pred,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void replace_copy_if(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator __first,
-    _ForwardIterator __last,
-    _ForwardOutIterator __result,
-    _Pred __pred,
-    const _Tp& __new_value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_copy_if requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "replace_copy_if requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(*__first), "replace_copy_if requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, const _Tp&, "replace_copy requires an OutputIterator");
-  if (!std::__replace_copy_if(
-          __policy, std::move(__first), std::move(__last), std::move(__result), std::move(__pred), __new_value))
-    std::__throw_bad_alloc();
-}
-
-template <class>
-void __pstl_replace_copy();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __replace_copy(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator&& __first,
-    _ForwardIterator&& __last,
-    _ForwardOutIterator&& __result,
-    const _Tp& __old_value,
-    const _Tp& __new_value) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_replace_copy, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first,
-                  _ForwardIterator __g_last,
-                  _ForwardOutIterator __g_result,
-                  const _Tp& __g_old_value,
-                  const _Tp& __g_new_value) {
-        return std::__replace_copy_if(
-            __policy,
-            std::move(__g_first),
-            std::move(__g_last),
-            std::move(__g_result),
-            [&](__iter_reference<_ForwardIterator> __element) { return __element == __g_old_value; },
-            __g_new_value);
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__result),
-      __old_value,
-      __new_value);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _Tp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void replace_copy(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator __first,
-    _ForwardIterator __last,
-    _ForwardOutIterator __result,
-    const _Tp& __old_value,
-    const _Tp& __new_value) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "replace_copy requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "replace_copy requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(*__first), "replace_copy requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(_ForwardOutIterator, const _Tp&, "replace_copy requires an OutputIterator");
-  if (!std::__replace_copy(
-          __policy, std::move(__first), std::move(__last), std::move(__result), __old_value, __new_value))
-    std::__throw_bad_alloc();
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_REPLACE_H
diff --git a/libcxx/include/__algorithm/pstl_rotate_copy.h b/libcxx/include/__algorithm/pstl_rotate_copy.h
deleted file mode 100644
index 1a32b710877c16..00000000000000
--- a/libcxx/include/__algorithm/pstl_rotate_copy.h
+++ /dev/null
@@ -1,90 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_ROTATE_COPY_H
-#define _LIBCPP___ALGORITHM_PSTL_ROTATE_COPY_H
-
-#include <__algorithm/pstl_copy.h>
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/is_execution_policy.h>
-#include <optional>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_rotate_copy();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator>
-__rotate_copy(_ExecutionPolicy&& __policy,
-              _ForwardIterator&& __first,
-              _ForwardIterator&& __middle,
-              _ForwardIterator&& __last,
-              _ForwardOutIterator&& __result) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_rotate_copy, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first,
-                  _ForwardIterator __g_middle,
-                  _ForwardIterator __g_last,
-                  _ForwardOutIterator __g_result) -> optional<_ForwardOutIterator> {
-        auto __result_mid =
-            std::__copy(__policy, _ForwardIterator(__g_middle), std::move(__g_last), std::move(__g_result));
-        if (!__result_mid)
-          return nullopt;
-        return std::__copy(__policy, std::move(__g_first), std::move(__g_middle), *std::move(__result_mid));
-      },
-      std::move(__first),
-      std::move(__middle),
-      std::move(__last),
-      std::move(__result));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator rotate_copy(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator __first,
-    _ForwardIterator __middle,
-    _ForwardIterator __last,
-    _ForwardOutIterator __result) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "rotate_copy requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "rotate_copy requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(*__first), "rotate_copy requires an OutputIterator");
-  auto __res =
-      std::__rotate_copy(__policy, std::move(__first), std::move(__middle), std::move(__last), std::move(__result));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *__res;
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_ROTATE_COPY_H
diff --git a/libcxx/include/__algorithm/pstl_sort.h b/libcxx/include/__algorithm/pstl_sort.h
deleted file mode 100644
index 769dd81af77e04..00000000000000
--- a/libcxx/include/__algorithm/pstl_sort.h
+++ /dev/null
@@ -1,85 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_SORT_H
-#define _LIBCPP___ALGORITHM_PSTL_SORT_H
-
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__algorithm/pstl_stable_sort.h>
-#include <__config>
-#include <__functional/operations.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__type_traits/remove_cvref.h>
-#include <__utility/empty.h>
-#include <__utility/forward.h>
-#include <__utility/move.h>
-#include <optional>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_sort();
-
-template <class _ExecutionPolicy,
-          class _RandomAccessIterator,
-          class _Comp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __sort(
-    _ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_sort, _RawPolicy),
-      [&__policy](_RandomAccessIterator __g_first, _RandomAccessIterator __g_last, _Comp __g_comp) {
-        std::stable_sort(__policy, std::move(__g_first), std::move(__g_last), std::move(__g_comp));
-        return optional<__empty>{__empty{}};
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__comp));
-}
-
-template <class _ExecutionPolicy,
-          class _RandomAccessIterator,
-          class _Comp,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-sort(_ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp) {
-  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "sort requires RandomAccessIterators");
-  if (!std::__sort(__policy, std::move(__first), std::move(__last), std::move(__comp)))
-    std::__throw_bad_alloc();
-}
-
-template <class _ExecutionPolicy,
-          class _RandomAccessIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void
-sort(_ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last) {
-  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "sort requires RandomAccessIterators");
-  std::sort(std::forward<_ExecutionPolicy>(__policy), std::move(__first), std::move(__last), less{});
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_SORT_H
diff --git a/libcxx/include/__algorithm/pstl_stable_sort.h b/libcxx/include/__algorithm/pstl_stable_sort.h
deleted file mode 100644
index f5e0dd40f72b47..00000000000000
--- a/libcxx/include/__algorithm/pstl_stable_sort.h
+++ /dev/null
@@ -1,63 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_STABLE_SORT_H
-#define _LIBCPP___ALGORITHM_PSTL_STABLE_SORT_H
-
-#include <__config>
-#include <__functional/operations.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__type_traits/remove_cvref.h>
-#include <__utility/empty.h>
-#include <__utility/move.h>
-#include <optional>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _ExecutionPolicy,
-          class _RandomAccessIterator,
-          class _Comp                                         = less<>,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__empty> __stable_sort(
-    _ExecutionPolicy&&, _RandomAccessIterator&& __first, _RandomAccessIterator&& __last, _Comp&& __comp = {}) noexcept {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_stable_sort<_RawPolicy>(_Backend{}, std::move(__first), std::move(__last), std::move(__comp));
-}
-
-template <class _ExecutionPolicy,
-          class _RandomAccessIterator,
-          class _Comp                                         = less<>,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI void stable_sort(
-    _ExecutionPolicy&& __policy, _RandomAccessIterator __first, _RandomAccessIterator __last, _Comp __comp = {}) {
-  _LIBCPP_REQUIRE_CPP17_RANDOM_ACCESS_ITERATOR(_RandomAccessIterator, "stable_sort requires RandomAccessIterators");
-  if (!std::__stable_sort(__policy, std::move(__first), std::move(__last), std::move(__comp)))
-    std::__throw_bad_alloc();
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_STABLE_SORT_H
diff --git a/libcxx/include/__algorithm/pstl_transform.h b/libcxx/include/__algorithm/pstl_transform.h
deleted file mode 100644
index 80e1d6b496f2ea..00000000000000
--- a/libcxx/include/__algorithm/pstl_transform.h
+++ /dev/null
@@ -1,122 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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_TRANSFORM_H
-#define _LIBCPP___ALGORITHM_PSTL_TRANSFORM_H
-
-#include <__config>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__pstl/configuration.h>
-#include <__type_traits/enable_if.h>
-#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
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _UnaryOperation,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardOutIterator>>
-__transform(_ExecutionPolicy&&,
-            _ForwardIterator&& __first,
-            _ForwardIterator&& __last,
-            _ForwardOutIterator&& __result,
-            _UnaryOperation&& __op) noexcept {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_transform<_RawPolicy>(
-      _Backend{}, std::move(__first), std::move(__last), std::move(__result), std::move(__op));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _UnaryOperation,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator __first,
-    _ForwardIterator __last,
-    _ForwardOutIterator __result,
-    _UnaryOperation __op) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "transform requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "transform requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(__op(*__first)), "transform requires an OutputIterator");
-  auto __res = std::__transform(__policy, std::move(__first), std::move(__last), std::move(__result), std::move(__op));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _ForwardOutIterator,
-          class _BinaryOperation,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI optional<__remove_cvref_t<_ForwardOutIterator>>
-__transform(_ExecutionPolicy&&,
-            _ForwardIterator1&& __first1,
-            _ForwardIterator1&& __last1,
-            _ForwardIterator2&& __first2,
-            _ForwardOutIterator&& __result,
-            _BinaryOperation&& __op) noexcept {
-  using _Backend = typename __select_backend<_RawPolicy>::type;
-  return std::__pstl_transform<_RawPolicy>(
-      _Backend{}, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__result), std::move(__op));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _ForwardOutIterator,
-          class _BinaryOperation,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator1 __first1,
-    _ForwardIterator1 __last1,
-    _ForwardIterator2 __first2,
-    _ForwardOutIterator __result,
-    _BinaryOperation __op) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator1, "transform requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator2, "transform requires ForwardIterators");
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardOutIterator, "transform requires an OutputIterator");
-  _LIBCPP_REQUIRE_CPP17_OUTPUT_ITERATOR(
-      _ForwardOutIterator, decltype(__op(*__first1, *__first2)), "transform requires an OutputIterator");
-  auto __res = std::__transform(
-      __policy, std::move(__first1), std::move(__last1), std::move(__first2), std::move(__result), std::move(__op));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___ALGORITHM_PSTL_TRANSFORM_H
diff --git a/libcxx/include/__numeric/pstl_transform_reduce.h b/libcxx/include/__numeric/pstl.h
similarity index 61%
rename from libcxx/include/__numeric/pstl_transform_reduce.h
rename to libcxx/include/__numeric/pstl.h
index fe41b1c86f3b1f..30ad4023488c19 100644
--- a/libcxx/include/__numeric/pstl_transform_reduce.h
+++ b/libcxx/include/__numeric/pstl.h
@@ -6,13 +6,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP___NUMERIC_PSTL_TRANSFORM_REDUCE_H
-#define _LIBCPP___NUMERIC_PSTL_TRANSFORM_REDUCE_H
+#ifndef _LIBCPP___NUMERIC_PSTL_H
+#define _LIBCPP___NUMERIC_PSTL_H
 
 #include <__algorithm/pstl_frontend_dispatch.h>
 #include <__config>
+#include <__functional/identity.h>
 #include <__functional/operations.h>
 #include <__iterator/cpp17_iterator_concepts.h>
+#include <__iterator/iterator_traits.h>
+#include <__numeric/pstl_transform_reduce.h>
 #include <__numeric/transform_reduce.h>
 #include <__pstl/configuration.h>
 #include <__type_traits/is_execution_policy.h>
@@ -153,10 +156,85 @@ _LIBCPP_HIDE_FROM_ABI _Tp transform_reduce(
   return *std::move(__res);
 }
 
+template <class>
+void __pstl_reduce();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _BinaryOperation                              = plus<>,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_Tp>
+__reduce(_ExecutionPolicy&& __policy,
+         _ForwardIterator&& __first,
+         _ForwardIterator&& __last,
+         _Tp&& __init,
+         _BinaryOperation&& __op = {}) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_reduce, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Tp __g_init, _BinaryOperation __g_op) {
+        return std::__transform_reduce(
+            __policy, std::move(__g_first), std::move(__g_last), std::move(__g_init), std::move(__g_op), __identity{});
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__init),
+      std::move(__op));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Tp,
+          class _BinaryOperation                              = plus<>,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Tp
+reduce(_ExecutionPolicy&& __policy,
+       _ForwardIterator __first,
+       _ForwardIterator __last,
+       _Tp __init,
+       _BinaryOperation __op = {}) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "reduce requires ForwardIterators");
+  auto __res = std::__reduce(__policy, std::move(__first), std::move(__last), std::move(__init), std::move(__op));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_value_type<_ForwardIterator>>
+__reduce(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last) noexcept {
+  return std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_reduce, _RawPolicy),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last) {
+        return std::__reduce(
+            __policy, std::move(__g_first), std::move(__g_last), __iter_value_type<_ForwardIterator>());
+      },
+      std::move(__first),
+      std::move(__last));
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI __iter_value_type<_ForwardIterator>
+reduce(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "reduce requires ForwardIterators");
+  auto __res = std::__reduce(__policy, std::move(__first), std::move(__last));
+  if (!__res)
+    std::__throw_bad_alloc();
+  return *std::move(__res);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
 
 _LIBCPP_POP_MACROS
 
-#endif // _LIBCPP___NUMERIC_PSTL_TRANSFORM_REDUCE_H
+#endif // _LIBCPP___NUMERIC_PSTL_H
diff --git a/libcxx/include/__numeric/pstl_reduce.h b/libcxx/include/__numeric/pstl_reduce.h
deleted file mode 100644
index d678b9480070b0..00000000000000
--- a/libcxx/include/__numeric/pstl_reduce.h
+++ /dev/null
@@ -1,112 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// 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___NUMERIC_PSTL_REDUCE_H
-#define _LIBCPP___NUMERIC_PSTL_REDUCE_H
-
-#include <__algorithm/pstl_frontend_dispatch.h>
-#include <__config>
-#include <__functional/identity.h>
-#include <__iterator/cpp17_iterator_concepts.h>
-#include <__iterator/iterator_traits.h>
-#include <__numeric/pstl_transform_reduce.h>
-#include <__type_traits/is_execution_policy.h>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class>
-void __pstl_reduce();
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _BinaryOperation                              = plus<>,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<_Tp>
-__reduce(_ExecutionPolicy&& __policy,
-         _ForwardIterator&& __first,
-         _ForwardIterator&& __last,
-         _Tp&& __init,
-         _BinaryOperation&& __op = {}) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_reduce, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Tp __g_init, _BinaryOperation __g_op) {
-        return std::__transform_reduce(
-            __policy, std::move(__g_first), std::move(__g_last), std::move(__g_init), std::move(__g_op), __identity{});
-      },
-      std::move(__first),
-      std::move(__last),
-      std::move(__init),
-      std::move(__op));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _Tp,
-          class _BinaryOperation                              = plus<>,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _Tp
-reduce(_ExecutionPolicy&& __policy,
-       _ForwardIterator __first,
-       _ForwardIterator __last,
-       _Tp __init,
-       _BinaryOperation __op = {}) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "reduce requires ForwardIterators");
-  auto __res = std::__reduce(__policy, std::move(__first), std::move(__last), std::move(__init), std::move(__op));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-[[nodiscard]] _LIBCPP_HIDE_FROM_ABI optional<__iter_value_type<_ForwardIterator>>
-__reduce(_ExecutionPolicy&& __policy, _ForwardIterator&& __first, _ForwardIterator&& __last) noexcept {
-  return std::__pstl_frontend_dispatch(
-      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_reduce, _RawPolicy),
-      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last) {
-        return std::__reduce(
-            __policy, std::move(__g_first), std::move(__g_last), __iter_value_type<_ForwardIterator>());
-      },
-      std::move(__first),
-      std::move(__last));
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
-          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI __iter_value_type<_ForwardIterator>
-reduce(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last) {
-  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator, "reduce requires ForwardIterators");
-  auto __res = std::__reduce(__policy, std::move(__first), std::move(__last));
-  if (!__res)
-    std::__throw_bad_alloc();
-  return *std::move(__res);
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___NUMERIC_PSTL_REDUCE_H
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
index 62ac4316647483..5e915f2dec2a38 100644
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -713,35 +713,14 @@ module std_private_algorithm_partition_copy                              [system
 module std_private_algorithm_partition_point                             [system] { header "__algorithm/partition_point.h" }
 module std_private_algorithm_pop_heap                                    [system] { header "__algorithm/pop_heap.h" }
 module std_private_algorithm_prev_permutation                            [system] { header "__algorithm/prev_permutation.h" }
-module std_private_algorithm_pstl_any_all_none_of                        [system] { header "__algorithm/pstl_any_all_none_of.h" }
-module std_private_algorithm_pstl_copy                                   [system] { header "__algorithm/pstl_copy.h" }
-module std_private_algorithm_pstl_count                                  [system] { header "__algorithm/pstl_count.h" }
-module std_private_algorithm_pstl_equal                                  [system] { header "__algorithm/pstl_equal.h" }
-module std_private_algorithm_pstl_fill                                   [system] { header "__algorithm/pstl_fill.h" }
-module std_private_algorithm_pstl_find                                   [system] {
-  header "__algorithm/pstl_find.h"
-  export *
-}
-module std_private_algorithm_pstl_for_each                               [system] {
-  header "__algorithm/pstl_for_each.h"
+module std_private_algorithm_pstl                                        [system] {
+  header "__algorithm/pstl.h"
   export *
 }
 module std_private_algorithm_pstl_frontend_dispatch                      [system] {
   header "__algorithm/pstl_frontend_dispatch.h"
   export std_private_utility_forward
 }
-module std_private_algorithm_pstl_generate                               [system] { header "__algorithm/pstl_generate.h" }
-module std_private_algorithm_pstl_is_partitioned                         [system] { header "__algorithm/pstl_is_partitioned.h" }
-module std_private_algorithm_pstl_merge                                  [system] { header "__algorithm/pstl_merge.h" }
-module std_private_algorithm_pstl_move                                   [system] { header "__algorithm/pstl_move.h" }
-module std_private_algorithm_pstl_replace                                [system] { header "__algorithm/pstl_replace.h" }
-module std_private_algorithm_pstl_rotate_copy                            [system] { header "__algorithm/pstl_rotate_copy.h" }
-module std_private_algorithm_pstl_sort                                   [system] { header "__algorithm/pstl_sort.h" }
-module std_private_algorithm_pstl_stable_sort                            [system] {
-  header "__algorithm/pstl_stable_sort.h"
-  export std_private_functional_operations
-}
-module std_private_algorithm_pstl_transform                              [system] { header "__algorithm/pstl_transform.h" }
 module std_private_algorithm_push_heap                                   [system] { header "__algorithm/push_heap.h" }
 module std_private_algorithm_ranges_adjacent_find                        [system] { header "__algorithm/ranges_adjacent_find.h" }
 module std_private_algorithm_ranges_all_of                               [system] { header "__algorithm/ranges_all_of.h" }
@@ -1576,9 +1555,8 @@ module std_private_numeric_inner_product            [system] { header "__numeric
 module std_private_numeric_iota                     [system] { header "__numeric/iota.h" }
 module std_private_numeric_midpoint                 [system] { header "__numeric/midpoint.h" }
 module std_private_numeric_partial_sum              [system] { header "__numeric/partial_sum.h" }
-module std_private_numeric_pstl_reduce              [system] { header "__numeric/pstl_reduce.h" }
-module std_private_numeric_pstl_transform_reduce    [system] {
-  header "__numeric/pstl_transform_reduce.h"
+module std_private_numeric_pstl                     [system] {
+  header "__numeric/pstl.h"
   export *
 }
 module std_private_numeric_reduce                   [system] { header "__numeric/reduce.h" }

>From 5e2d0db662a84e90c5722f8b34b292fce1a09902 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2 at gmail.com>
Date: Thu, 18 Apr 2024 08:20:58 -0400
Subject: [PATCH 2/2] Generate files

---
 libcxx/include/libcxx.imp | 20 ++------------------
 1 file changed, 2 insertions(+), 18 deletions(-)

diff --git a/libcxx/include/libcxx.imp b/libcxx/include/libcxx.imp
index c224090e72465e..6b0fec65921b72 100644
--- a/libcxx/include/libcxx.imp
+++ b/libcxx/include/libcxx.imp
@@ -72,23 +72,8 @@
   { include: [ "<__algorithm/partition_point.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/pop_heap.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/prev_permutation.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_any_all_none_of.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_copy.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_count.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_equal.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_fill.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_find.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_for_each.h>", "private", "<algorithm>", "public" ] },
+  { include: [ "<__algorithm/pstl.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/pstl_frontend_dispatch.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_generate.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_is_partitioned.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_merge.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_move.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_replace.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_rotate_copy.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_sort.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_stable_sort.h>", "private", "<algorithm>", "public" ] },
-  { include: [ "<__algorithm/pstl_transform.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/push_heap.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/ranges_adjacent_find.h>", "private", "<algorithm>", "public" ] },
   { include: [ "<__algorithm/ranges_all_of.h>", "private", "<algorithm>", "public" ] },
@@ -563,8 +548,7 @@
   { include: [ "<__numeric/iota.h>", "private", "<numeric>", "public" ] },
   { include: [ "<__numeric/midpoint.h>", "private", "<numeric>", "public" ] },
   { include: [ "<__numeric/partial_sum.h>", "private", "<numeric>", "public" ] },
-  { include: [ "<__numeric/pstl_reduce.h>", "private", "<numeric>", "public" ] },
-  { include: [ "<__numeric/pstl_transform_reduce.h>", "private", "<numeric>", "public" ] },
+  { include: [ "<__numeric/pstl.h>", "private", "<numeric>", "public" ] },
   { include: [ "<__numeric/reduce.h>", "private", "<numeric>", "public" ] },
   { include: [ "<__numeric/saturation_arithmetic.h>", "private", "<numeric>", "public" ] },
   { include: [ "<__numeric/transform_exclusive_scan.h>", "private", "<numeric>", "public" ] },



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