[libc++][PSTL] Implement std::copy{,_n}

Reviewed By: ldionne, #libc

Spies: jloser, libcxx-commits

Differential Revision: https://reviews.llvm.org/D149706

7 files changed, 265 insertions, 44 deletions

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 3e210323e51d..04293ba4bad6 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -79,6 +79,7 @@ set(files
   __algorithm/pstl_backends/cpu_backends/for_each.h
   __algorithm/pstl_backends/cpu_backends/serial.h
   __algorithm/pstl_backends/cpu_backends/transform.h
+  __algorithm/pstl_copy.h
   __algorithm/pstl_fill.h
   __algorithm/pstl_find.h
   __algorithm/pstl_for_each.h
diff --git a/libcxx/include/__algorithm/pstl_copy.h b/libcxx/include/__algorithm/pstl_copy.h
new file mode 100644
index 000000000000..2d331d29a5d1
--- /dev/null
+++ b/libcxx/include/__algorithm/pstl_copy.h
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_transform.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__iterator/iterator_traits.h>
+#include <__type_traits/is_constant_evaluated.h>
+#include <__type_traits/is_execution_policy.h>
+#include <__type_traits/is_trivially_copyable.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
+
+// TODO: Use the std::copy/move shenanigans to forward to std::memmove
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
+copy(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _ForwardOutIterator __result) {
+  return std::transform(__policy, __first, __last, __result, __identity());
+}
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _ForwardOutIterator,
+          class _Size,
+          enable_if_t<is_execution_policy_v<__remove_cvref_t<_ExecutionPolicy>>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI _ForwardOutIterator
+copy_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _ForwardOutIterator __result) {
+  if constexpr (__is_cpp17_random_access_iterator<_ForwardIterator>::value)
+    return std::copy(__policy, __first, __first + __n, __result);
+  else
+    return std::copy_n(__first, __n, __result);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+#endif // _LIBCPP___ALGORITHM_PSTL_COPY_H
diff --git a/libcxx/include/__pstl/internal/glue_algorithm_defs.h b/libcxx/include/__pstl/internal/glue_algorithm_defs.h
index de4501e56b2c..00458d5ffbbd 100644
--- a/libcxx/include/__pstl/internal/glue_algorithm_defs.h
+++ b/libcxx/include/__pstl/internal/glue_algorithm_defs.h
@@ -112,14 +112,6 @@ __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardItera
 
 // [alg.copy]
 
-template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
-copy(_ExecutionPolicy&& __exec, _ForwardIterator1 __first, _ForwardIterator1 __last, _ForwardIterator2 __result);
-
-template <class _ExecutionPolicy, class _ForwardIterator1, class _Size, class _ForwardIterator2>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
-copy_n(_ExecutionPolicy&& __exec, _ForwardIterator1 __first, _Size __n, _ForwardIterator2 __result);
-
 template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2, class _Predicate>
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
 copy_if(_ExecutionPolicy&& __exec,
diff --git a/libcxx/include/__pstl/internal/glue_algorithm_impl.h b/libcxx/include/__pstl/internal/glue_algorithm_impl.h
index bae5efa7d057..942ea0dea50b 100644
--- a/libcxx/include/__pstl/internal/glue_algorithm_impl.h
+++ b/libcxx/include/__pstl/internal/glue_algorithm_impl.h
@@ -178,42 +178,6 @@ __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardItera
 
 // [alg.copy]
 
-template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
-copy(_ExecutionPolicy&& __exec, _ForwardIterator1 __first, _ForwardIterator1 __last, _ForwardIterator2 __result) {
-  auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first, __result);
-
-  using __is_vector = typename decltype(__dispatch_tag)::__is_vector;
-
-  return __pstl::__internal::__pattern_walk2_brick(
-      __dispatch_tag,
-      std::forward<_ExecutionPolicy>(__exec),
-      __first,
-      __last,
-      __result,
-      [](_ForwardIterator1 __begin, _ForwardIterator1 __end, _ForwardIterator2 __res) {
-        return __pstl::__internal::__brick_copy(__begin, __end, __res, __is_vector{});
-      });
-}
-
-template <class _ExecutionPolicy, class _ForwardIterator1, class _Size, class _ForwardIterator2>
-__pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
-copy_n(_ExecutionPolicy&& __exec, _ForwardIterator1 __first, _Size __n, _ForwardIterator2 __result) {
-  auto __dispatch_tag = __pstl::__internal::__select_backend(__exec, __first, __result);
-
-  using __is_vector = typename decltype(__dispatch_tag)::__is_vector;
-
-  return __pstl::__internal::__pattern_walk2_brick_n(
-      __dispatch_tag,
-      std::forward<_ExecutionPolicy>(__exec),
-      __first,
-      __n,
-      __result,
-      [](_ForwardIterator1 __begin, _Size __sz, _ForwardIterator2 __res) {
-        return __pstl::__internal::__brick_copy_n(__begin, __sz, __res, __is_vector{});
-      });
-}
-
 template <class _ExecutionPolicy, class _ForwardIterator1, class _ForwardIterator2, class _Predicate>
 __pstl::__internal::__enable_if_execution_policy<_ExecutionPolicy, _ForwardIterator2>
 copy_if(_ExecutionPolicy&& __exec,
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 280333e5b33d..190214021df7 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -1801,6 +1801,7 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/pop_heap.h>
 #include <__algorithm/prev_permutation.h>
 #include <__algorithm/pstl_any_all_none_of.h>
+#include <__algorithm/pstl_copy.h>
 #include <__algorithm/pstl_fill.h>
 #include <__algorithm/pstl_find.h>
 #include <__algorithm/pstl_for_each.h>
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy.pass.cpp
new file mode 100644
index 000000000000..bee1ef9bcec3
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy.pass.cpp
@@ -0,0 +1,104 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// REQUIRES: with-pstl
+
+// <algorithm>
+
+// template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
+//   ForwardIterator2 copy(ExecutionPolicy&& policy,
+//                         ForwardIterator1 first, ForwardIterator1 last,
+//                         ForwardIterator2 result);
+
+#include <algorithm>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+
+EXECUTION_POLICY_SFINAE_TEST(copy);
+
+static_assert(sfinae_test_copy<int, int*, int*, bool (*)(int)>);
+static_assert(!sfinae_test_copy<std::execution::parallel_policy, int*, int*, int>);
+
+template <class Iter1, class Iter2>
+struct TestInt {
+  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::copy(policy, Iter1(std::data(a)), Iter1(std::data(a) + std::size(a)), Iter2(std::data(out)));
+      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 + 1);
+    }
+  }
+};
+
+struct CopiedToTester {
+  bool copied_to   = false;
+  CopiedToTester() = default;
+  CopiedToTester(const CopiedToTester&) {}
+  CopiedToTester& operator=(const CopiedToTester&) {
+    assert(!copied_to);
+    copied_to = true;
+    return *this;
+  }
+  ~CopiedToTester() = default;
+};
+
+template <class Iter1, class Iter2>
+struct TestNonTrivial {
+  template <class Policy>
+  void operator()(Policy&& policy) {
+    // simple test
+    for (const int size : {0, 1, 2, 100, 350}) {
+      std::vector<CopiedToTester> a(size);
+
+      std::vector<CopiedToTester> out(std::size(a));
+      auto ret = std::copy(policy, Iter1(std::data(a)), Iter1(std::data(a) + std::size(a)), Iter2(std::data(out)));
+      assert(base(ret) == std::data(out) + std::size(out));
+      assert(std::all_of(std::begin(out), std::end(out), [](CopiedToTester& t) { return t.copied_to; }));
+      assert(std::none_of(std::begin(a), std::end(a), [](CopiedToTester& t) { return t.copied_to; }));
+    }
+  }
+};
+
+struct TestIteratorsNonTrivial {
+  template <class Iter2>
+  void operator()() {}
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, types::apply_type_identity{[](auto v) {
+                    using Iter = typename decltype(v)::type;
+                    types::for_each(
+                        types::forward_iterator_list<int*>{},
+                        TestIteratorWithPolicies< types::partial_instantiation<TestInt, Iter>::template apply>{});
+                  }});
+
+  types::for_each(
+      types::forward_iterator_list<CopiedToTester*>{}, types::apply_type_identity{[](auto v) {
+        using Iter = typename decltype(v)::type;
+        types::for_each(
+            types::forward_iterator_list<CopiedToTester*>{},
+            TestIteratorWithPolicies< types::partial_instantiation<TestNonTrivial, Iter>::template apply>{});
+      }});
+
+  return 0;
+}
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy_n.pass.cpp
new file mode 100644
index 000000000000..128108ac1381
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/pstl.copy_n.pass.cpp
@@ -0,0 +1,102 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// REQUIRES: with-pstl
+
+// <algorithm>
+
+// template<class ExecutionPolicy, class ForwardIterator1, class Size, class ForwardIterator2>
+//   ForwardIterator2 copy_n(ExecutionPolicy&& exec,
+//                           ForwardIterator1 first, Size n,
+//                           ForwardIterator2 result);
+
+#include <algorithm>
+#include <vector>
+
+#include "test_macros.h"
+#include "test_execution_policies.h"
+#include "test_iterators.h"
+
+EXECUTION_POLICY_SFINAE_TEST(copy_n);
+
+static_assert(sfinae_test_copy_n<int, int*, int*, bool (*)(int)>);
+static_assert(!sfinae_test_copy_n<std::execution::parallel_policy, int*, int*, int>);
+
+template <class Iter1, class Iter2>
+struct TestInt {
+  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::copy_n(policy, Iter1(std::data(a)), std::size(a), Iter2(std::data(out)));
+      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 + 1);
+    }
+  }
+};
+
+struct TestIteratorsInt {
+  template <class Iter2>
+  void operator()() {
+    types::for_each(types::forward_iterator_list<int*>{},
+                    TestIteratorWithPolicies<types::partial_instantiation<TestInt, Iter2>::template apply>{});
+  }
+};
+
+struct CopiedToTester {
+  bool copied_to = false;
+  CopiedToTester() = default;
+  CopiedToTester(const CopiedToTester&) {}
+  CopiedToTester& operator=(const CopiedToTester&) {
+    assert(!copied_to);
+    copied_to = true;
+    return *this;
+  }
+  ~CopiedToTester() = default;
+};
+
+template <class Iter1, class Iter2>
+struct TestNonTrivial {
+  template <class Policy>
+  void operator()(Policy&& policy) {
+    // simple test
+    for (const int size : {0, 1, 2, 100, 350}) {
+      std::vector<CopiedToTester> a(size);
+
+      std::vector<CopiedToTester> out(std::size(a));
+      auto ret = std::copy_n(policy, Iter1(std::data(a)), std::size(a), Iter2(std::data(out)));
+      assert(base(ret) == std::data(out) + std::size(out));
+      assert(std::all_of(std::begin(out), std::end(out), [](CopiedToTester& t) { return t.copied_to; }));
+      assert(std::none_of(std::begin(a), std::end(a), [](CopiedToTester& t) { return t.copied_to; }));
+    }
+  }
+};
+
+struct TestIteratorsNonTrivial {
+  template <class Iter2>
+  void operator()() {
+    types::for_each(types::forward_iterator_list<CopiedToTester*>{},
+                    TestIteratorWithPolicies<types::partial_instantiation<TestNonTrivial, Iter2>::template apply>{});
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, TestIteratorsInt{});
+  types::for_each(types::forward_iterator_list<CopiedToTester*>{}, TestIteratorsNonTrivial{});
+
+  return 0;
+}