[libc++] Use uninitialized algorithms for vector

Reviewed By: ldionne, #libc

Spies: libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D128146

13 files changed, 212 insertions, 124 deletions

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 71c30e73b5ba..29b693b45509 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -384,6 +384,7 @@ set(files
   __memory/ranges_uninitialized_algorithms.h
   __memory/raw_storage_iterator.h
   __memory/shared_ptr.h
+  __memory/swap_allocator.h
   __memory/temporary_buffer.h
   __memory/uninitialized_algorithms.h
   __memory/unique_ptr.h
diff --git a/libcxx/include/__hash_table b/libcxx/include/__hash_table
index 6123a310ad63..959ef7fe7d83 100644
--- a/libcxx/include/__hash_table
+++ b/libcxx/include/__hash_table
@@ -18,6 +18,7 @@
 #include <__debug>
 #include <__functional/hash.h>
 #include <__iterator/iterator_traits.h>
+#include <__memory/swap_allocator.h>
 #include <__utility/swap.h>
 #include <cmath>
 #include <initializer_list>
diff --git a/libcxx/include/__memory/swap_allocator.h b/libcxx/include/__memory/swap_allocator.h
new file mode 100644
index 000000000000..64970fa9e2f4
--- /dev/null
+++ b/libcxx/include/__memory/swap_allocator.h
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___MEMORY_SWAP_ALLOCATOR_H
+#define _LIBCPP___MEMORY_SWAP_ALLOCATOR_H
+
+#include <__config>
+#include <__memory/allocator_traits.h>
+#include <__type_traits/integral_constant.h>
+#include <__utility/swap.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <typename _Alloc>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11 void __swap_allocator(_Alloc& __a1, _Alloc& __a2, true_type)
+#if _LIBCPP_STD_VER > 11
+    _NOEXCEPT
+#else
+    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
+#endif
+{
+  using _VSTD::swap;
+  swap(__a1, __a2);
+}
+
+template <typename _Alloc>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11 void
+__swap_allocator(_Alloc&, _Alloc&, false_type) _NOEXCEPT {}
+
+template <typename _Alloc>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11 void __swap_allocator(_Alloc& __a1, _Alloc& __a2)
+#if _LIBCPP_STD_VER > 11
+    _NOEXCEPT
+#else
+    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
+#endif
+{
+  _VSTD::__swap_allocator(
+      __a1, __a2, integral_constant<bool, allocator_traits<_Alloc>::propagate_on_container_swap::value>());
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___MEMORY_SWAP_ALLOCATOR_H
diff --git a/libcxx/include/__memory/uninitialized_algorithms.h b/libcxx/include/__memory/uninitialized_algorithms.h
index 3a8560f080c6..8b8fef1aa597 100644
--- a/libcxx/include/__memory/uninitialized_algorithms.h
+++ b/libcxx/include/__memory/uninitialized_algorithms.h
@@ -10,12 +10,17 @@
 #ifndef _LIBCPP___MEMORY_UNINITIALIZED_ALGORITHMS_H
 #define _LIBCPP___MEMORY_UNINITIALIZED_ALGORITHMS_H
 
+#include <__algorithm/copy.h>
+#include <__algorithm/move.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
+#include <__iterator/reverse_iterator.h>
 #include <__memory/addressof.h>
 #include <__memory/allocator_traits.h>
 #include <__memory/construct_at.h>
+#include <__memory/pointer_traits.h>
 #include <__memory/voidify.h>
+#include <__type_traits/is_constant_evaluated.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/transaction.h>
@@ -347,6 +352,7 @@ uninitialized_move_n(_InputIterator __ifirst, _Size __n, _ForwardIterator __ofir
                                                    __unreachable_sentinel(), __iter_move);
 }
 
+// TODO: Rewrite this to iterate left to right and use reverse_iterators when calling
 // Destroys every element in the range [first, last) FROM RIGHT TO LEFT using allocator
 // destruction. If elements are themselves C-style arrays, they are recursively destroyed
 // in the same manner.
@@ -492,6 +498,133 @@ constexpr void __uninitialized_allocator_value_construct_n(_Alloc& __alloc, _Bid
 
 #endif // _LIBCPP_STD_VER > 14
 
+// Destroy all elements in [__first, __last) from left to right using allocator destruction.
+template <class _Alloc, class _Iter, class _Sent>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 void
+__allocator_destroy(_Alloc& __alloc, _Iter __first, _Sent __last) {
+  for (; __first != __last; ++__first)
+    allocator_traits<_Alloc>::destroy(__alloc, std::__to_address(__first));
+}
+
+template <class _Alloc, class _Iter>
+class _AllocatorDestroyRangeReverse {
+public:
+  _AllocatorDestroyRangeReverse(_Alloc& __alloc, _Iter& __first, _Iter& __last)
+      : __alloc_(__alloc), __first_(__first), __last_(__last) {}
+
+  _LIBCPP_CONSTEXPR_AFTER_CXX11 void operator()() const {
+    std::__allocator_destroy(__alloc_, std::reverse_iterator<_Iter>(__last_), std::reverse_iterator<_Iter>(__first_));
+  }
+
+private:
+  _Alloc& __alloc_;
+  _Iter& __first_;
+  _Iter& __last_;
+};
+
+// Copy-construct [__first1, __last1) in [__first2, __first2 + N), where N is distance(__first1, __last1).
+//
+// The caller has to ensure that __first2 can hold at least N uninitialized elements. If an exception is thrown the
+// already copied elements are destroyed in reverse order of their construction.
+template <class _Alloc, class _Iter1, class _Sent1, class _Iter2>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Iter2
+__uninitialized_allocator_copy(_Alloc& __alloc, _Iter1 __first1, _Sent1 __last1, _Iter2 __first2) {
+  auto __destruct_first = __first2;
+  auto __guard =
+      std::__make_transaction(_AllocatorDestroyRangeReverse<_Alloc, _Iter2>(__alloc, __destruct_first, __first2));
+  while (__first1 != __last1) {
+    allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__first2), *__first1);
+    ++__first1;
+    ++__first2;
+  }
+  __guard.__complete();
+  return __first2;
+}
+
+template <class _Alloc, class _Type>
+struct __allocator_has_trivial_copy_construct : _Not<__has_construct<_Alloc, _Type*, const _Type&> > {};
+
+template <class _Type>
+struct __allocator_has_trivial_copy_construct<allocator<_Type>, _Type> : true_type {};
+
+template <class _Alloc,
+          class _Type,
+          class _RawType = typename remove_const<_Type>::type,
+          __enable_if_t<
+              // using _RawType because of the allocator<T const> extension
+              is_trivially_copy_constructible<_RawType>::value && is_trivially_copy_assignable<_RawType>::value &&
+              __allocator_has_trivial_copy_construct<_Alloc, _RawType>::value>* = nullptr>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Type*
+__uninitialized_allocator_copy(_Alloc&, const _Type* __first1, const _Type* __last1, _Type* __first2) {
+  // TODO: Remove the const_cast once we drop support for std::allocator<T const>
+  if (__libcpp_is_constant_evaluated()) {
+    while (__first1 != __last1) {
+      std::__construct_at(std::__to_address(__first2), *__first1);
+      ++__first1;
+      ++__first2;
+    }
+    return __first2;
+  } else {
+    return std::copy(__first1, __last1, const_cast<_RawType*>(__first2));
+  }
+}
+
+// Move-construct the elements [__first1, __last1) into [__first2, __first2 + N)
+// if the move constructor is noexcept, where N is distance(__first1, __last1).
+//
+// Otherwise try to copy all elements. If an exception is thrown the already copied
+// elements are destroyed in reverse order of their construction.
+template <class _Alloc, class _Iter1, class _Sent1, class _Iter2>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Iter2 __uninitialized_allocator_move_if_noexcept(
+    _Alloc& __alloc, _Iter1 __first1, _Sent1 __last1, _Iter2 __first2) {
+  static_assert(__is_cpp17_move_insertable<_Alloc>::value,
+                "The specified type does not meet the requirements of Cpp17MoveInsertable");
+  auto __destruct_first = __first2;
+  auto __guard =
+      std::__make_transaction(_AllocatorDestroyRangeReverse<_Alloc, _Iter2>(__alloc, __destruct_first, __first2));
+
+  while (__first1 != __last1) {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__first2), std::move_if_noexcept(*__first1));
+#else
+    allocator_traits<_Alloc>::construct(__alloc, std::__to_address(__first2), std::move(*__first1));
+#endif
+    ++__first1;
+    ++__first2;
+  }
+  __guard.__complete();
+  return __first2;
+}
+
+template <class _Alloc, class _Type>
+struct __allocator_has_trivial_move_construct : _Not<__has_construct<_Alloc, _Type*, _Type&&> > {};
+
+template <class _Type>
+struct __allocator_has_trivial_move_construct<allocator<_Type>, _Type> : true_type {};
+
+#ifndef _LIBCPP_COMPILER_GCC
+template <
+    class _Alloc,
+    class _Iter1,
+    class _Iter2,
+    class _Type = typename iterator_traits<_Iter1>::value_type,
+    class = __enable_if_t<is_trivially_move_constructible<_Type>::value && is_trivially_move_assignable<_Type>::value &&
+                          __allocator_has_trivial_move_construct<_Alloc, _Type>::value> >
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX17 _Iter1
+__uninitialized_allocator_move_if_noexcept(_Alloc&, _Iter1 __first1, _Iter1 __last1, _Iter2 __first2) {
+  if (__libcpp_is_constant_evaluated()) {
+    while (__first1 != __last1) {
+      std::__construct_at(std::__to_address(__first2), std::move(*__first1));
+      ++__first1;
+      ++__first2;
+    }
+    return __first2;
+  } else {
+    return std::move(__first1, __last1, __first2);
+  }
+}
+#endif // _LIBCPP_COMPILER_GCC
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___MEMORY_UNINITIALIZED_ALGORITHMS_H
diff --git a/libcxx/include/__split_buffer b/libcxx/include/__split_buffer
index 7409b51b1f96..f78167466217 100644
--- a/libcxx/include/__split_buffer
+++ b/libcxx/include/__split_buffer
@@ -19,6 +19,7 @@
 #include <__iterator/move_iterator.h>
 #include <__memory/allocator.h>
 #include <__memory/compressed_pair.h>
+#include <__memory/swap_allocator.h>
 #include <__utility/forward.h>
 #include <memory>
 #include <type_traits>
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index 8d8449706871..59525a03047a 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -17,6 +17,7 @@
 #include <__iterator/distance.h>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/next.h>
+#include <__memory/swap_allocator.h>
 #include <__utility/forward.h>
 #include <__utility/swap.h>
 #include <limits>
diff --git a/libcxx/include/__utility/transaction.h b/libcxx/include/__utility/transaction.h
index 87e51c0b198e..e2cc43820845 100644
--- a/libcxx/include/__utility/transaction.h
+++ b/libcxx/include/__utility/transaction.h
@@ -86,6 +86,11 @@ private:
     bool __completed_;
 };
 
+template <class _Rollback>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR __transaction<_Rollback> __make_transaction(_Rollback __rollback) {
+  return __transaction<_Rollback>(std::move(__rollback));
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___UTILITY_TRANSACTION_H
diff --git a/libcxx/include/forward_list b/libcxx/include/forward_list
index aab3b8715d01..ee90aaa4771f 100644
--- a/libcxx/include/forward_list
+++ b/libcxx/include/forward_list
@@ -188,6 +188,7 @@ template <class T, class Allocator, class Predicate>
 #include <__iterator/iterator_traits.h>
 #include <__iterator/move_iterator.h>
 #include <__iterator/next.h>
+#include <__memory/swap_allocator.h>
 #include <__utility/forward.h>
 #include <limits>
 #include <memory>
diff --git a/libcxx/include/list b/libcxx/include/list
index 1db29d14b842..5fcbd67c6703 100644
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -194,6 +194,7 @@ template <class T, class Allocator, class Predicate>
 #include <__iterator/next.h>
 #include <__iterator/prev.h>
 #include <__iterator/reverse_iterator.h>
+#include <__memory/swap_allocator.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
diff --git a/libcxx/include/memory b/libcxx/include/memory
index ec9f5773929f..56f8159fbd44 100644
--- a/libcxx/include/memory
+++ b/libcxx/include/memory
@@ -885,93 +885,6 @@ template<size_t N, class T>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Alloc, class _Ptr>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_forward_with_exception_guarantees(_Alloc& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2) {
-    static_assert(__is_cpp17_move_insertable<_Alloc>::value,
-        "The specified type does not meet the requirements of Cpp17MoveInsertable");
-    typedef allocator_traits<_Alloc> _Traits;
-    for (; __begin1 != __end1; ++__begin1, (void)++__begin2) {
-        _Traits::construct(__a, _VSTD::__to_address(__begin2),
-#ifdef _LIBCPP_NO_EXCEPTIONS
-            _VSTD::move(*__begin1)
-#else
-            _VSTD::move_if_noexcept(*__begin1)
-#endif
-        );
-    }
-}
-
-template <class _Alloc, class _Tp, typename enable_if<
-    (__is_default_allocator<_Alloc>::value || !__has_construct<_Alloc, _Tp*, _Tp>::value) &&
-    is_trivially_move_constructible<_Tp>::value
->::type>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_forward_with_exception_guarantees(_Alloc&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2) {
-    ptrdiff_t _Np = __end1 - __begin1;
-    if (_Np > 0) {
-        _VSTD::memcpy(__begin2, __begin1, _Np * sizeof(_Tp));
-        __begin2 += _Np;
-    }
-}
-
-template <class _Alloc, class _Iter, class _Ptr>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_range_forward(_Alloc& __a, _Iter __begin1, _Iter __end1, _Ptr& __begin2) {
-    typedef allocator_traits<_Alloc> _Traits;
-    for (; __begin1 != __end1; ++__begin1, (void) ++__begin2) {
-        _Traits::construct(__a, _VSTD::__to_address(__begin2), *__begin1);
-    }
-}
-
-template <class _Alloc, class _Source, class _Dest,
-          class _RawSource = typename remove_const<_Source>::type,
-          class _RawDest = typename remove_const<_Dest>::type,
-          class =
-    typename enable_if<
-        is_trivially_copy_constructible<_Dest>::value &&
-        is_same<_RawSource, _RawDest>::value &&
-        (__is_default_allocator<_Alloc>::value || !__has_construct<_Alloc, _Dest*, _Source&>::value)
-    >::type>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_range_forward(_Alloc&, _Source* __begin1, _Source* __end1, _Dest*& __begin2) {
-    ptrdiff_t _Np = __end1 - __begin1;
-    if (_Np > 0) {
-        _VSTD::memcpy(const_cast<_RawDest*>(__begin2), __begin1, _Np * sizeof(_Dest));
-        __begin2 += _Np;
-    }
-}
-
-template <class _Alloc, class _Ptr>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_backward_with_exception_guarantees(_Alloc& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2) {
-    static_assert(__is_cpp17_move_insertable<_Alloc>::value,
-        "The specified type does not meet the requirements of Cpp17MoveInsertable");
-    typedef allocator_traits<_Alloc> _Traits;
-    while (__end1 != __begin1) {
-        _Traits::construct(__a, _VSTD::__to_address(__end2 - 1),
-#ifdef _LIBCPP_NO_EXCEPTIONS
-            _VSTD::move(*--__end1)
-#else
-            _VSTD::move_if_noexcept(*--__end1)
-#endif
-        );
-        --__end2;
-    }
-}
-
-template <class _Alloc, class _Tp, class = typename enable_if<
-    (__is_default_allocator<_Alloc>::value || !__has_construct<_Alloc, _Tp*, _Tp>::value) &&
-    is_trivially_move_constructible<_Tp>::value
->::type>
-_LIBCPP_INLINE_VISIBILITY
-void __construct_backward_with_exception_guarantees(_Alloc&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2) {
-    ptrdiff_t _Np = __end1 - __begin1;
-    __end2 -= _Np;
-    if (_Np > 0)
-        _VSTD::memcpy(static_cast<void*>(__end2), static_cast<void const*>(__begin1), _Np * sizeof(_Tp));
-}
-
 struct __destruct_n
 {
 private:
@@ -1013,37 +926,6 @@ public:
 
 _LIBCPP_FUNC_VIS void* align(size_t __align, size_t __sz, void*& __ptr, size_t& __space);
 
-// --- Helper for container swap --
-template <typename _Alloc>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __swap_allocator(_Alloc & __a1, _Alloc & __a2, true_type)
-#if _LIBCPP_STD_VER > 11
-    _NOEXCEPT
-#else
-    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
-#endif
-{
-    using _VSTD::swap;
-    swap(__a1, __a2);
-}
-
-template <typename _Alloc>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __swap_allocator(_Alloc &, _Alloc &, false_type) _NOEXCEPT {}
-
-template <typename _Alloc>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
-void __swap_allocator(_Alloc & __a1, _Alloc & __a2)
-#if _LIBCPP_STD_VER > 11
-    _NOEXCEPT
-#else
-    _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
-#endif
-{
-    _VSTD::__swap_allocator(__a1, __a2,
-      integral_constant<bool, allocator_traits<_Alloc>::propagate_on_container_swap::value>());
-}
-
 template <typename _Alloc, typename _Traits=allocator_traits<_Alloc> >
 struct __noexcept_move_assign_container : public integral_constant<bool,
     _Traits::propagate_on_container_move_assignment::value
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index cbf0b4f7f16d..e2a9dae40a50 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -832,6 +832,7 @@ module std [system] {
       module ranges_uninitialized_algorithms { private header "__memory/ranges_uninitialized_algorithms.h" }
       module raw_storage_iterator            { private header "__memory/raw_storage_iterator.h" }
       module shared_ptr                      { private header "__memory/shared_ptr.h" }
+      module swap_allocator                  { private header "__memory/swap_allocator.h" }
       module temporary_buffer                { private header "__memory/temporary_buffer.h" }
       module uninitialized_algorithms        { private header "__memory/uninitialized_algorithms.h" }
       module unique_ptr                      { private header "__memory/unique_ptr.h" }
diff --git a/libcxx/include/string b/libcxx/include/string
index bb169a82c9e7..3723dc8a3938 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -532,6 +532,7 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len );
 #include <__iterator/reverse_iterator.h>
 #include <__iterator/wrap_iter.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/swap_allocator.h>
 #include <__string/char_traits.h>
 #include <__string/extern_template_lists.h>
 #include <__utility/auto_cast.h>
diff --git a/libcxx/include/vector b/libcxx/include/vector
index 14f586c9bfd7..30030f85e43c 100644
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -291,6 +291,8 @@ erase_if(vector<T, Allocator>& c, Predicate pred);    // C++20
 #include <__iterator/reverse_iterator.h>
 #include <__iterator/wrap_iter.h>
 #include <__memory/allocate_at_least.h>
+#include <__memory/pointer_traits.h>
+#include <__memory/swap_allocator.h>
 #include <__split_buffer>
 #include <__utility/forward.h>
 #include <__utility/move.h>
@@ -895,9 +897,11 @@ template <class _Tp, class _Allocator>
 void
 vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v)
 {
-
     __annotate_delete();
-    _VSTD::__construct_backward_with_exception_guarantees(this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
+    using _RevIter = std::reverse_iterator<pointer>;
+    __v.__begin_   = std::__uninitialized_allocator_move_if_noexcept(
+                       __alloc(), _RevIter(__end_), _RevIter(__begin_), _RevIter(__v.__begin_))
+                       .base();
     _VSTD::swap(this->__begin_, __v.__begin_);
     _VSTD::swap(this->__end_, __v.__end_);
     _VSTD::swap(this->__end_cap(), __v.__end_cap());
@@ -912,8 +916,11 @@ vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, a
 {
     __annotate_delete();
     pointer __r = __v.__begin_;
-    _VSTD::__construct_backward_with_exception_guarantees(this->__alloc(), this->__begin_, __p, __v.__begin_);
-    _VSTD::__construct_forward_with_exception_guarantees(this->__alloc(), __p, this->__end_, __v.__end_);
+    using _RevIter = std::reverse_iterator<pointer>;
+    __v.__begin_   = std::__uninitialized_allocator_move_if_noexcept(
+                       __alloc(), _RevIter(__p), _RevIter(__begin_), _RevIter(__v.__begin_))
+                       .base();
+    __v.__end_ = std::__uninitialized_allocator_move_if_noexcept(__alloc(), __p, __end_, __v.__end_);
     _VSTD::swap(this->__begin_, __v.__begin_);
     _VSTD::swap(this->__end_, __v.__end_);
     _VSTD::swap(this->__end_cap(), __v.__end_cap());
@@ -1001,8 +1008,8 @@ typename enable_if
 >::type
 vector<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last, size_type __n)
 {
-    _ConstructTransaction __tx(*this, __n);
-    _VSTD::__construct_range_forward(this->__alloc(), __first, __last, __tx.__pos_);
+  _ConstructTransaction __tx(*this, __n);
+  __tx.__pos_ = std::__uninitialized_allocator_copy(__alloc(), __first, __last, __tx.__pos_);
 }
 
 //  Default constructs __n objects starting at __end_