[libc++][ranges] Implement ranges::rotate.

Also fix `ranges::stable_sort` and `ranges::inplace_merge` to support
proxy iterators now that their internal implementations can correctly
dispatch `rotate`.

Differential Revision: https://reviews.llvm.org/D130758

Author: var-const

libcxx/docs/Status/RangesAlgorithms.csv

@@ -68,7 +68,7 @@ Merge,set_union,Hui Xie,`D129657 <https://llvm.org/D129657>`_,✅
 Permutation,remove,Nikolas Klauser,`D128618 <https://llvm.org/D128618>`_,✅
 Permutation,remove_if,Nikolas Klauser,`D128618 <https://llvm.org/D128618>`_,✅
 Permutation,reverse,Nikolas Klauser,`D125752 <https://llvm.org/D125752>`_,✅
-Permutation,rotate,Nikolas Klauser,`D124122 <https://llvm.org/D124122>`_,Under review
+Permutation,rotate,Konstantin Varlamov and Nikolas Klauser,`D130758 <https://llvm.org/D130758>`_,✅
 Permutation,shuffle,Konstantin Varlamov,`D130321 <https://llvm.org/D130321>`_,✅
 Permutation,unique,Hui Xie,`D130404 <https://llvm.org/D130404>`_,✅
 Permutation,partition,Konstantin Varlamov,`D129624 <https://llvm.org/D129624>`_,✅

libcxx/include/CMakeLists.txt

@@ -1,6 +1,5 @@
 set(files
   __algorithm/adjacent_find.h
-  __algorithm/algorithm_family.h
   __algorithm/all_of.h
   __algorithm/any_of.h
   __algorithm/binary_search.h
@@ -134,6 +133,7 @@ set(files
   __algorithm/ranges_replace_if.h
   __algorithm/ranges_reverse.h
   __algorithm/ranges_reverse_copy.h
+  __algorithm/ranges_rotate.h
   __algorithm/ranges_rotate_copy.h
   __algorithm/ranges_sample.h
   __algorithm/ranges_search.h

libcxx/include/__algorithm/algorithm_family.h

@@ -9,7 +9,6 @@
 #ifndef _LIBCPP___ALGORITHM_INPLACE_MERGE_H
 #define _LIBCPP___ALGORITHM_INPLACE_MERGE_H
 
-#include <__algorithm/algorithm_family.h>
 #include <__algorithm/comp.h>
 #include <__algorithm/comp_ref_type.h>
 #include <__algorithm/iterator_operations.h>
@@ -65,7 +64,7 @@ void __half_inplace_merge(_InputIterator1 __first1, _Sent1 __last1,
     {
         if (__first2 == __last2)
         {
-            _AlgFamily<_AlgPolicy>::__move(__first1, __last1, __result);
+            std::__move<_AlgPolicy>(__first1, __last1, __result);
             return;
         }
 
@@ -185,8 +184,7 @@ void __inplace_merge(
         difference_type __len22 = __len2 - __len21;  // distance(__m2, __last)
         // [__first, __m1) [__m1, __middle) [__middle, __m2) [__m2, __last)
         // swap middle two partitions
-        // TODO(alg-policy): pass `_AlgPolicy` once it's supported by `rotate`.
-        __middle = _VSTD::rotate(__m1, __middle, __m2);
+        __middle = std::__rotate<_AlgPolicy>(__m1, __middle, __m2).first;
         // __len12 and __len21 now have swapped meanings
         // merge smaller range with recursive call and larger with tail recursion elimination
         if (__len11 + __len21 < __len12 + __len22)

libcxx/include/__algorithm/inplace_merge.h

@@ -19,6 +19,7 @@
 #include <__iterator/iter_swap.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
+#include <__iterator/prev.h>
 #include <__iterator/readable_traits.h>
 #include <__utility/declval.h>
 #include <__utility/forward.h>
@@ -53,6 +54,7 @@ struct _IterOps<_RangeAlgPolicy> {
   static constexpr auto __iter_move = ranges::iter_move;
   static constexpr auto iter_swap = ranges::iter_swap;
   static constexpr auto next = ranges::next;
+  static constexpr auto prev = ranges::prev;
   static constexpr auto __advance_to = ranges::advance;
 };
 
@@ -146,10 +148,18 @@ struct _IterOps<_ClassicAlgPolicy> {
   template <class _Iter>
   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_AFTER_CXX11
   __uncvref_t<_Iter> next(_Iter&& __it,
-                          typename iterator_traits<__uncvref_t<_Iter> >::difference_type __n = 1){
+                          typename iterator_traits<__uncvref_t<_Iter> >::difference_type __n = 1) {
     return std::next(std::forward<_Iter>(__it), __n);
   }
 
+  // prev
+  template <class _Iter>
+  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_AFTER_CXX11
+  __uncvref_t<_Iter> prev(_Iter&& __iter,
+                 typename iterator_traits<__uncvref_t<_Iter> >::difference_type __n = 1) {
+    return std::prev(std::forward<_Iter>(__iter), __n);
+  }
+
   template <class _Iter>
   _LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR_AFTER_CXX11
   void __advance_to(_Iter& __first, _Iter __last) {

libcxx/include/__algorithm/iterator_operations.h

@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___ALGORITHM_MOVE_H
 #define _LIBCPP___ALGORITHM_MOVE_H
 
+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/unwrap_iter.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
@@ -26,18 +27,19 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 // move
 
-template <class _InIter, class _Sent, class _OutIter>
+template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 pair<_InIter, _OutIter> __move_impl(_InIter __first, _Sent __last, _OutIter __result) {
   while (__first != __last) {
-    *__result = std::move(*__first);
+    *__result = _IterOps<_AlgPolicy>::__iter_move(__first);
     ++__first;
     ++__result;
   }
   return std::make_pair(std::move(__first), std::move(__result));
 }
 
-template <class _InType,
+template <class _AlgPolicy,
+          class _InType,
           class _OutType,
           class = __enable_if_t<is_same<typename remove_const<_InType>::type, _OutType>::value
                              && is_trivially_move_assignable<_OutType>::value> >
@@ -49,7 +51,7 @@ pair<_InType*, _OutType*> __move_impl(_InType* __first, _InType* __last, _OutTyp
    && !is_trivially_copyable<_InType>::value
 #endif
      )
-    return std::__move_impl<_InType*, _InType*, _OutType*>(__first, __last, __result);
+    return std::__move_impl<_AlgPolicy, _InType*, _InType*, _OutType*>(__first, __last, __result);
   const size_t __n = static_cast<size_t>(__last - __first);
   ::__builtin_memmove(__result, __first, __n * sizeof(_OutType));
   return std::make_pair(__first + __n, __result + __n);
@@ -65,7 +67,8 @@ template <class _Iter>
 struct __is_trivially_move_assignable_unwrapped
     : __is_trivially_move_assignable_unwrapped_impl<decltype(std::__unwrap_iter<_Iter>(std::declval<_Iter>()))> {};
 
-template <class _InIter,
+template <class _AlgPolicy,
+          class _InIter,
           class _OutIter,
           __enable_if_t<is_same<typename remove_const<typename iterator_traits<_InIter>::value_type>::type,
                                 typename iterator_traits<_OutIter>::value_type>::value
@@ -81,33 +84,34 @@ __move_impl(reverse_iterator<_InIter> __first,
   auto __last_base = std::__unwrap_iter(__last.base());
   auto __result_base = std::__unwrap_iter(__result.base());
   auto __result_first = __result_base - (__first_base - __last_base);
-  std::__move_impl(__last_base, __first_base, __result_first);
+  std::__move_impl<_AlgPolicy>(__last_base, __first_base, __result_first);
   return std::make_pair(__last, reverse_iterator<_OutIter>(std::__rewrap_iter(__result.base(), __result_first)));
 }
 
-template <class _InIter, class _Sent, class _OutIter>
+template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
 __enable_if_t<is_copy_constructible<_InIter>::value
            && is_copy_constructible<_Sent>::value
            && is_copy_constructible<_OutIter>::value, pair<_InIter, _OutIter> >
 __move(_InIter __first, _Sent __last, _OutIter __result) {
-  auto __ret = std::__move_impl(std::__unwrap_iter(__first), std::__unwrap_iter(__last), std::__unwrap_iter(__result));
+  auto __ret = std::__move_impl<_AlgPolicy>(
+      std::__unwrap_iter(__first), std::__unwrap_iter(__last), std::__unwrap_iter(__result));
   return std::make_pair(std::__rewrap_iter(__first, __ret.first), std::__rewrap_iter(__result, __ret.second));
 }
 
-template <class _InIter, class _Sent, class _OutIter>
+template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
 __enable_if_t<!is_copy_constructible<_InIter>::value
            || !is_copy_constructible<_Sent>::value
            || !is_copy_constructible<_OutIter>::value, pair<_InIter, _OutIter> >
 __move(_InIter __first, _Sent __last, _OutIter __result) {
-  return std::__move_impl(std::move(__first), std::move(__last), std::move(__result));
+  return std::__move_impl<_AlgPolicy>(std::move(__first), std::move(__last), std::move(__result));
 }
 
 template <class _InputIterator, class _OutputIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator move(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
-  return std::__move(__first, __last, __result).second;
+  return std::__move<_ClassicAlgPolicy>(__first, __last, __result).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/include/__algorithm/move.h

@@ -9,6 +9,7 @@
 #ifndef _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
 #define _LIBCPP___ALGORITHM_MOVE_BACKWARD_H
 
+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/unwrap_iter.h>
 #include <__config>
 #include <__utility/move.h>
@@ -21,33 +22,33 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _OutputIterator>
+template <class _AlgPolicy, class _InputIterator, class _OutputIterator>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 _OutputIterator
 __move_backward_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
     while (__first != __last)
-        *--__result = _VSTD::move(*--__last);
+        *--__result = _IterOps<_AlgPolicy>::__iter_move(--__last);
     return __result;
 }
 
-template <class _InputIterator, class _OutputIterator>
+template <class _AlgPolicy, class _InputIterator, class _OutputIterator>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 _OutputIterator
-__move_backward(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+__move_backward_impl(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
-    return _VSTD::__move_backward_constexpr(__first, __last, __result);
+    return _VSTD::__move_backward_constexpr<_AlgPolicy>(__first, __last, __result);
 }
 
-template <class _Tp, class _Up>
+template <class _AlgPolicy, class _Tp, class _Up>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename enable_if
 <
     is_same<typename remove_const<_Tp>::type, _Up>::value &&
     is_trivially_move_assignable<_Up>::value,
     _Up*
 >::type
-__move_backward(_Tp* __first, _Tp* __last, _Up* __result)
+__move_backward_impl(_Tp* __first, _Tp* __last, _Up* __result)
 {
     const size_t __n = static_cast<size_t>(__last - __first);
     if (__n > 0)
@@ -58,22 +59,31 @@ __move_backward(_Tp* __first, _Tp* __last, _Up* __result)
     return __result;
 }
 
-template <class _BidirectionalIterator1, class _BidirectionalIterator2>
+template <class _AlgPolicy, class _BidirectionalIterator1, class _BidirectionalIterator2>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _BidirectionalIterator2
-move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
-              _BidirectionalIterator2 __result)
+__move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
+                _BidirectionalIterator2 __result)
 {
     if (__libcpp_is_constant_evaluated()) {
-        return _VSTD::__move_backward_constexpr(__first, __last, __result);
+        return _VSTD::__move_backward_constexpr<_AlgPolicy>(__first, __last, __result);
     } else {
         return _VSTD::__rewrap_iter(__result,
-            _VSTD::__move_backward(_VSTD::__unwrap_iter(__first),
-                                   _VSTD::__unwrap_iter(__last),
-                                   _VSTD::__unwrap_iter(__result)));
+            _VSTD::__move_backward_impl<_AlgPolicy>(_VSTD::__unwrap_iter(__first),
+                                                    _VSTD::__unwrap_iter(__last),
+                                                    _VSTD::__unwrap_iter(__result)));
     }
 }
 
+template <class _BidirectionalIterator1, class _BidirectionalIterator2>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_BidirectionalIterator2
+move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
+              _BidirectionalIterator2 __result)
+{
+  return std::__move_backward<_ClassicAlgPolicy>(std::move(__first), std::move(__last), std::move(__result));
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_MOVE_BACKWARD_H

libcxx/include/__algorithm/move_backward.h

@@ -10,6 +10,7 @@
 #define _LIBCPP___ALGORITHM_RANGES_MOVE_H
 
 #include <__algorithm/in_out_result.h>
+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/move.h>
 #include <__config>
 #include <__iterator/concepts.h>
@@ -36,24 +37,12 @@ namespace __move {
 struct __fn {
 
   template <class _InIter, class _Sent, class _OutIter>
-    requires __iter_move::__move_deref<_InIter> // check that we are allowed to std::move() the value
   _LIBCPP_HIDE_FROM_ABI constexpr static
   move_result<_InIter, _OutIter> __move_impl(_InIter __first, _Sent __last, _OutIter __result) {
-    auto __ret = std::__move(std::move(__first), std::move(__last), std::move(__result));
+    auto __ret = std::__move<_RangeAlgPolicy>(std::move(__first), std::move(__last), std::move(__result));
     return {std::move(__ret.first), std::move(__ret.second)};
   }
 
-  template <class _InIter, class _Sent, class _OutIter>
-  _LIBCPP_HIDE_FROM_ABI constexpr static
-  move_result<_InIter, _OutIter> __move_impl(_InIter __first, _Sent __last, _OutIter __result) {
-    while (__first != __last) {
-      *__result = ranges::iter_move(__first);
-      ++__first;
-      ++__result;
-    }
-    return {std::move(__first), std::move(__result)};
-  }
-
   template <input_iterator _InIter, sentinel_for<_InIter> _Sent, weakly_incrementable _OutIter>
     requires indirectly_movable<_InIter, _OutIter>
   _LIBCPP_HIDE_FROM_ABI constexpr