diff --git a/libcxx/include/vector b/libcxx/include/vector
--- a/libcxx/include/vector
+++ b/libcxx/include/vector
@@ -839,15 +839,15 @@
 #ifndef _LIBCPP_CXX03_LANG
     template <class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    inline void __push_back_slow_path(_Up&& __x);
+    inline pointer __push_back_slow_path(_Up&& __x);
 
     template <class... _Args>
     _LIBCPP_INLINE_VISIBILITY
-    inline void __emplace_back_slow_path(_Args&&... __args);
+    inline pointer __emplace_back_slow_path(_Args&&... __args);
 #else
     template <class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    inline void __push_back_slow_path(_Up& __x);
+    inline pointer __push_back_slow_path(_Up& __x);
 #endif
 
     // The following functions are no-ops outside of AddressSanitizer mode.
@@ -919,6 +919,39 @@
     _ConstructTransaction& operator=(_ConstructTransaction const&) = delete;
   };
 
+#if defined(_LIBCPP_HAS_NO_ASAN)
+  struct _AsanTransaction {
+    explicit _AsanTransaction(vector&, size_type) {}
+    void __commit(size_type) {}
+  };
+#elif defined(_LIBCPP_NO_EXCEPTIONS)
+  struct _AsanTransaction {
+    explicit _AsanTransaction(vector &, size_type __n) {
+      __v_.__annotate_increase(__n);
+    }
+    void __commit(size_type) {}
+  };
+#else  // _LIBCPP_NO_EXCEPTIONS
+  struct _AsanTransaction {
+    _AsanTransaction(vector& __v, size_type __n) : __v_(__v), __n(__n) {
+      __v_.__annotate_increase(__n);
+    }
+    ~_AsanTransaction() { __v_.__annotate_shrink(__n_); }
+    void __commit(size_type __n) { __n_ -= __n; }
+    vector& __v_;
+    size_t __n_;
+  };
+#endif // _LIBCPP_NO_EXCEPTIONS
+
+  template <class... _Args>
+  _LIBCPP_INLINE_VISIBILITY void __construct_one_at(pointer __pos,
+                                                    _Args&&... __args) {
+    _AsanTransaction tx(*this, 1);
+    __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__pos),
+                              _VSTD::forward<_Args>(__args)...);
+    tx.__commit(1);
+  }
+
   template <class ..._Args>
   _LIBCPP_INLINE_VISIBILITY
   void __construct_one_at_end(_Args&& ...__args) {
@@ -1614,7 +1647,7 @@
 
 template <class _Tp, class _Allocator>
 template <class _Up>
-void
+typename vector<_Tp, _Allocator>::pointer
 #ifndef _LIBCPP_CXX03_LANG
 vector<_Tp, _Allocator>::__push_back_slow_path(_Up&& __x)
 #else
@@ -1627,6 +1660,7 @@
     __alloc_traits::construct(__a, _VSTD::__to_address(__v.__end_), _VSTD::forward<_Up>(__x));
     __v.__end_++;
     __swap_out_circular_buffer(__v);
+    return this->__end_;
 }
 
 template <class _Tp, class _Allocator>
@@ -1634,12 +1668,15 @@
 void
 vector<_Tp, _Allocator>::push_back(const_reference __x)
 {
-    if (this->__end_ != this->__end_cap())
+    pointer __end = this->__end_;
+    if (__end != this->__end_cap())
     {
-        __construct_one_at_end(__x);
+        __construct_one_at(__end, __x);
     }
-    else
-        __push_back_slow_path(__x);
+    else {
+        __end = __push_back_slow_path(__x) - 1;
+    }
+    this->__end_ = __end + 1;
 }
 
 #ifndef _LIBCPP_CXX03_LANG
@@ -1649,17 +1686,20 @@
 void
 vector<_Tp, _Allocator>::push_back(value_type&& __x)
 {
-    if (this->__end_ < this->__end_cap())
+    pointer __end = this->__end_;
+    if (__end != this->__end_cap())
     {
-        __construct_one_at_end(_VSTD::move(__x));
+        __construct_one_at(__end, _VSTD::move(__x));
     }
-    else
-        __push_back_slow_path(_VSTD::move(__x));
+    else {
+        __end = __push_back_slow_path(std::move(__x)) - 1;
+    }
+    this->__end_ = __end + 1;
 }
 
 template <class _Tp, class _Allocator>
 template <class... _Args>
-void
+typename vector<_Tp, _Allocator>::pointer
 vector<_Tp, _Allocator>::__emplace_back_slow_path(_Args&&... __args)
 {
     allocator_type& __a = this->__alloc();
@@ -1668,6 +1708,7 @@
     __alloc_traits::construct(__a, _VSTD::__to_address(__v.__end_), _VSTD::forward<_Args>(__args)...);
     __v.__end_++;
     __swap_out_circular_buffer(__v);
+    return this->__end_;
 }
 
 template <class _Tp, class _Allocator>
@@ -1680,14 +1721,16 @@
 #endif
 vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
-    if (this->__end_ < this->__end_cap())
+    pointer __pos = this->__end_;
+    if (__pos < this->__end_cap())
     {
-        __construct_one_at_end(_VSTD::forward<_Args>(__args)...);
+        __construct_one_at(__pos, _VSTD::forward<_Args>(__args)...);
+    } else {
+      __pos = __emplace_back_slow_path(_VSTD::forward<_Args>(__args)...) - 1;
     }
-    else
-        __emplace_back_slow_path(_VSTD::forward<_Args>(__args)...);
+    this->__end_ = __pos + 1;
 #if _LIBCPP_STD_VER > 14
-    return this->back();
+    return *__pos;
 #endif
 }