Revert "[libc++][PSTL] Implement std::transform"

This reverts commit cbd9e5454741ebe6b39521fe1a8ed4eed5c2c801.

The wrong patch was landed.

8 files changed, 44 insertions, 290 deletions

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index f304b5dafef8..4dd363de4d17 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -82,7 +82,6 @@ set(files
   __algorithm/pstl_find.h
   __algorithm/pstl_for_each.h
   __algorithm/pstl_frontend_dispatch.h
-  __algorithm/pstl_transform.h
   __algorithm/push_heap.h
   __algorithm/ranges_adjacent_find.h
   __algorithm/ranges_all_of.h
diff --git a/libcxx/include/__algorithm/pstl_transform.h b/libcxx/include/__algorithm/pstl_transform.h
deleted file mode 100644
index 74a869583f51..000000000000
--- a/libcxx/include/__algorithm/pstl_transform.h
+++ /dev/null
@@ -1,129 +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 <__algorithm/transform.h>
-#include <__config>
-#include <__iterator/iterator_traits.h>
-#include <__pstl/internal/parallel_backend.h>
-#include <__pstl/internal/unseq_backend_simd.h>
-#include <__type_traits/is_execution_policy.h>
-#include <__utility/terminate_on_exception.h>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator,
-          class _ForwardOutIterator,
-          class _UnaryOperation,
-          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator __first,
-    _ForwardIterator __last,
-    _ForwardOutIterator __result,
-    _UnaryOperation __op) {
-  if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
-                __is_cpp17_random_access_iterator<_ForwardIterator>::value &&
-                __is_cpp17_random_access_iterator<_ForwardOutIterator>::value) {
-    std::__terminate_on_exception([&] {
-      __pstl::__par_backend::__parallel_for(
-          __pstl::__internal::__par_backend_tag{},
-          __policy,
-          __first,
-          __last,
-          [&__policy, __op, __first, __result](_ForwardIterator __brick_first, _ForwardIterator __brick_last) {
-            return std::transform(
-                std::__remove_parallel_policy(__policy),
-                __brick_first,
-                __brick_last,
-                __result + (__brick_first - __first),
-                __op);
-          });
-    });
-    return __result + (__last - __first);
-  } else if constexpr (__is_unsequenced_execution_policy_v<_ExecutionPolicy> &&
-                       __is_cpp17_random_access_iterator<_ForwardIterator>::value &&
-                       __is_cpp17_random_access_iterator<_ForwardOutIterator>::value) {
-    return __pstl::__unseq_backend::__simd_walk_2(
-        __first,
-        __last - __first,
-        __result,
-        [&](__iter_reference<_ForwardIterator> __in_value, __iter_reference<_ForwardOutIterator> __out_value) {
-          __out_value = __op(__in_value);
-        });
-  } else {
-    return std::transform(__first, __last, __result, __op);
-  }
-}
-
-template <class _ExecutionPolicy,
-          class _ForwardIterator1,
-          class _ForwardIterator2,
-          class _ForwardOutIterator,
-          class _BinaryOperation,
-          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
-_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator transform(
-    _ExecutionPolicy&& __policy,
-    _ForwardIterator1 __first1,
-    _ForwardIterator1 __last1,
-    _ForwardIterator2 __first2,
-    _ForwardOutIterator __result,
-    _BinaryOperation __op) {
-  if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
-                __is_cpp17_random_access_iterator<_ForwardIterator1>::value &&
-                __is_cpp17_random_access_iterator<_ForwardIterator2>::value &&
-                __is_cpp17_random_access_iterator<_ForwardOutIterator>::value) {
-    std::__terminate_on_exception([&] {
-      __pstl::__par_backend::__parallel_for(
-          __pstl::__internal::__par_backend_tag{},
-          __policy,
-          __first1,
-          __last1,
-          [&__policy, __op, __first1, __first2, __result](
-              _ForwardIterator1 __brick_first, _ForwardIterator1 __brick_last) {
-            return std::transform(
-                std::__remove_parallel_policy(__policy),
-                __brick_first,
-                __brick_last,
-                __first2 + (__brick_first - __first1),
-                __result + (__brick_first - __first1),
-                __op);
-          });
-    });
-    return __result + (__last1 - __first1);
-  } else if constexpr (__is_unsequenced_execution_policy_v<_ExecutionPolicy> &&
-                       __is_cpp17_random_access_iterator<_ForwardIterator1>::value &&
-                       __is_cpp17_random_access_iterator<_ForwardIterator2>::value &&
-                       __is_cpp17_random_access_iterator<_ForwardOutIterator>::value) {
-    return __pstl::__unseq_backend::__simd_walk_3(
-        __first1,
-        __last1 - __first1,
-        __first2,
-        __result,
-        [&](__iter_reference<_ForwardIterator1> __in1,
-            __iter_reference<_ForwardIterator2> __in2,
-            __iter_reference<_ForwardOutIterator> __out) { __out = __op(__in1, __in2); });
-  } else {
-    return std::transform(__first1, __last1, __first2, __result, __op);
-  }
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
-
-#endif // _LIBCPP___ALGORITHM_PSTL_TRANSFORM_H
diff --git a/libcxx/include/__pstl/internal/glue_algorithm_defs.h b/libcxx/include/__pstl/internal/glue_algorithm_defs.h
index de4501e56b2c..82bb3f508d5a 100644
--- a/libcxx/include/__pstl/internal/glue_algorithm_defs.h
+++ b/libcxx/include/__pstl/internal/glue_algorithm_defs.h
@@ -134,6 +134,29 @@ template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterato
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2> swap_ranges(
     _ExecutionPolicy&& __exec, _ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2);
 
+// [alg.transform]
+
+template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2, class _UnaryOperation>
+__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
+transform(_ExecutionPolicy&& __exec,
+          _ForwardIterator1 __first,
+          _ForwardIterator1 __last,
+          _ForwardIterator2 __result,
+          _UnaryOperation __op);
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator1,
+          class _ForwardIterator2,
+          class _ForwardIterator,
+          class _BinaryOperation>
+__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator>
+transform(_ExecutionPolicy&& __exec,
+          _ForwardIterator1 __first1,
+          _ForwardIterator1 __last1,
+          _ForwardIterator2 __first2,
+          _ForwardIterator __result,
+          _BinaryOperation __op);
+
 // [alg.replace]
 
 template <class _ExecutionPolicy, class _ForwardIterator, class _UnaryPredicate, class _Tp>
diff --git a/libcxx/include/__pstl/internal/glue_algorithm_impl.h b/libcxx/include/__pstl/internal/glue_algorithm_impl.h
index bae5efa7d057..db62705233b9 100644
--- a/libcxx/include/__pstl/internal/glue_algorithm_impl.h
+++ b/libcxx/include/__pstl/internal/glue_algorithm_impl.h
@@ -251,6 +251,27 @@ __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardItera
 
 // [alg.transform]
 
+template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2, class _UnaryOperation>
+__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
+transform(_ExecutionPolicy&& __exec,
+          _ForwardIterator1 __first,
+          _ForwardIterator1 __last,
+          _ForwardIterator2 __result,
+          _UnaryOperation __op) {
+  typedef typename iterator_traits<_ForwardIterator1>::reference _InputType;
+  typedef typename iterator_traits<_ForwardIterator2>::reference _OutputType;
+
+  auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first, __result);
+
+  return __pstl::__internal::__pattern_walk2(
+      __dispatch_tag,
+      std::forward<_ExecutionPolicy>(__exec),
+      __first,
+      __last,
+      __result,
+      [__op](_InputType __x, _OutputType __y) mutable { __y = __op(__x); });
+}
+
 template <class _ExecutionPolicy,
           class _ForwardIterator1,
           class _ForwardIterator2,
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 18a89eb1a4dc..469bf1706628 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -1792,7 +1792,6 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/pstl_fill.h>
 #include <__algorithm/pstl_find.h>
 #include <__algorithm/pstl_for_each.h>
-#include <__algorithm/pstl_transform.h>
 #include <__algorithm/push_heap.h>
 #include <__algorithm/ranges_adjacent_find.h>
 #include <__algorithm/ranges_all_of.h>
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.binary.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.binary.pass.cpp
deleted file mode 100644
index 1076a1548ee3..000000000000
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.binary.pass.cpp
+++ /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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14
-
-// UNSUPPORTED: libcpp-has-no-incomplete-pstl
-
-// <algorithm>
-
-// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
-//          class ForwardIterator, class BinaryOperation>
-//   ForwardIterator
-//     transform(ExecutionPolicy&& exec,
-//               ForwardIterator1 first1, ForwardIterator1 last1,
-//               ForwardIterator2 first2, ForwardIterator result,
-//               BinaryOperation binary_op);
-
-#include <algorithm>
-#include <vector>
-
-#include "test_macros.h"
-#include "test_execution_policies.h"
-#include "test_iterators.h"
-
-EXECUTION_POLICY_SFINAE_TEST(transform);
-
-static_assert(sfinae_test_transform<int, int*, int*, int*, int*, bool (*)(int)>);
-static_assert(!sfinae_test_transform<std::execution::parallel_policy, int*, int*, int*, int*, int (*)(int, int)>);
-
-template <class Iter1, class Iter2, class Iter3>
-struct Test {
-  template <class Policy>
-  void operator()(Policy&& policy) {
-    // simple test
-    for (const int size : {0, 1, 2, 100, 350}) {
-      std::vector<int> a(size);
-      std::vector<int> b(size);
-      for (int i = 0; i != size; ++i) {
-        a[i] = i + 1;
-        b[i] = i - 3;
-      }
-
-      std::vector<int> out(std::size(a));
-      decltype(auto) ret = std::transform(
-          policy,
-          Iter1(std::data(a)),
-          Iter1(std::data(a) + std::size(a)),
-          Iter2(std::data(b)),
-          Iter3(std::data(out)),
-          [](int i, int j) { return i + j + 3; });
-      static_assert(std::is_same_v<decltype(ret), Iter3>);
-      assert(base(ret) == std::data(out) + std::size(out));
-      for (int i = 0; i != size; ++i) {
-        assert(out[i] == i * 2 + 1);
-      }
-    }
-  }
-};
-
-template <class Iter3>
-struct TestIterators2 {
-  template <class Iter2>
-  void operator()() {
-    types::for_each(types::forward_iterator_list<int*>{},
-                    TestIteratorWithPolicies<types::partial_instantiation<Test, Iter2, Iter3>::template apply>{});
-  }
-};
-
-struct TestIterators1 {
-  template <class Iter3>
-  void operator()() {
-    types::for_each(types::forward_iterator_list<int*>{}, TestIterators2<Iter3>{});
-  }
-};
-
-int main(int, char**) {
-  types::for_each(types::forward_iterator_list<int*>{}, TestIterators1{});
-
-  return 0;
-}
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.unary.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.unary.pass.cpp
deleted file mode 100644
index 31069de4e523..000000000000
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/pstl.transform.unary.pass.cpp
+++ /dev/null
@@ -1,67 +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
-//
-//===----------------------------------------------------------------------===//
-
-// UNSUPPORTED: c++03, c++11, c++14
-
-// UNSUPPORTED: libcpp-has-no-incomplete-pstl
-
-// <algorithm>
-
-// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
-//          class UnaryOperation>
-//   ForwardIterator2
-//     transform(ExecutionPolicy&& exec,
-//               ForwardIterator1 first1, ForwardIterator1 last1,
-//               ForwardIterator2 result, UnaryOperation op);
-
-#include <algorithm>
-#include <vector>
-
-#include "test_macros.h"
-#include "test_execution_policies.h"
-#include "test_iterators.h"
-
-// We can't test the constraint on the execution policy, because that would conflict with the binary
-// transform algorithm that doesn't take an execution policy, which is not constrained at all.
-
-template <class Iter1, class Iter2>
-struct Test {
-  template <class Policy>
-  void operator()(Policy&& policy) {
-    // simple test
-    for (const int size : {0, 1, 2, 100, 350}) {
-      std::vector<int> a(size);
-      for (int i = 0; i != size; ++i)
-        a[i] = i + 1;
-
-      std::vector<int> out(std::size(a));
-      decltype(auto) ret = std::transform(
-          policy, Iter1(std::data(a)), Iter1(std::data(a) + std::size(a)), Iter2(std::data(out)), [](int i) {
-            return i + 3;
-          });
-      static_assert(std::is_same_v<decltype(ret), Iter2>);
-      assert(base(ret) == std::data(out) + std::size(out));
-      for (int i = 0; i != size; ++i)
-        assert(out[i] == i + 4);
-    }
-  }
-};
-
-struct TestIterators {
-  template <class Iter2>
-  void operator()() {
-    types::for_each(types::forward_iterator_list<int*>{},
-                    TestIteratorWithPolicies<types::partial_instantiation<Test, Iter2>::template apply>{});
-  }
-};
-
-int main(int, char**) {
-  types::for_each(types::forward_iterator_list<int*>{}, TestIterators{});
-
-  return 0;
-}
diff --git a/libcxx/test/support/type_algorithms.h b/libcxx/test/support/type_algorithms.h
index ac3ee60b2ccf..95a282b7b0bc 100644
--- a/libcxx/test/support/type_algorithms.h
+++ b/libcxx/test/support/type_algorithms.h
@@ -52,13 +52,6 @@ TEST_CONSTEXPR_CXX14 void for_each(type_list<Types...>, Functor f) {
   swallow((f.template operator()<Types>(), 0)...);
 }
 
-
-template <template <class...> class T, class... Args>
-struct partial_instantiation {
-  template <class Other>
-  using apply = T<Args..., Other>;
-};
-
 // type categories defined in [basic.fundamental] plus extensions (without CV-qualifiers)
 
 using character_types =