diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -156,6 +156,11 @@
 // The implementation moved to the header, but we still export the symbols from
 // the dylib for backwards compatibility.
 #    define _LIBCPP_ABI_DO_NOT_EXPORT_TO_CHARS_BASE_10
+
+// Defines exactly one std::default_delete<T> for the whole program, as opposed
+// to one per std::unique_ptr<T> (only relevant to std::unique_ptr: other instances
+// can still exist).
+#    define _LIBCPP_EXACTLY_ONE_DEFAULT_DELETE_PER_TYPE
 #  elif _LIBCPP_ABI_VERSION == 1
 #    if !(defined(_LIBCPP_OBJECT_FORMAT_COFF) || defined(_LIBCPP_OBJECT_FORMAT_XCOFF))
 // Enable compiling copies of now inline methods into the dylib to support
diff --git a/libcxx/include/__memory/unique_ptr.h b/libcxx/include/__memory/unique_ptr.h
--- a/libcxx/include/__memory/unique_ptr.h
+++ b/libcxx/include/__memory/unique_ptr.h
@@ -35,7 +35,9 @@
 #include <__type_traits/is_swappable.h>
 #include <__type_traits/is_void.h>
 #include <__type_traits/remove_extent.h>
+#include <__type_traits/remove_pointer.h>
 #include <__type_traits/type_identity.h>
+#include <__utility/exchange.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <cstddef>
@@ -131,7 +133,8 @@
                 "the specified deleter type cannot be an rvalue reference");
 
 private:
-  __compressed_pair<pointer, deleter_type> __ptr_;
+  _LIBCPP_NO_UNIQUE_ADDRESS pointer __ptr_;
+  _LIBCPP_NO_UNIQUE_ADDRESS deleter_type __deleter_;
 
   struct __nat { int __for_bool_; };
 
@@ -177,27 +180,27 @@
     >::type;
 
 public:
-  template <bool _Dummy = true,
-            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(__value_init_tag(), __value_init_tag()) {}
+  template <bool _Dummy = true, class = _EnableIfDeleterDefaultConstructible<_Dummy> >
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(), __deleter_() {}
 
-  template <bool _Dummy = true,
-            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(__value_init_tag(), __value_init_tag()) {}
+  template <bool _Dummy = true, class = _EnableIfDeleterDefaultConstructible<_Dummy> >
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : unique_ptr() {}
 
   template <bool _Dummy = true, class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 explicit unique_ptr(pointer __p) _NOEXCEPT
-      : __ptr_(__p, __value_init_tag()) {}
+      : __ptr_(__p),
+        __deleter_() {}
 
   template <bool _Dummy = true, class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> > >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(pointer __p, _LValRefType<_Dummy> __d) _NOEXCEPT
-      : __ptr_(__p, __d) {}
+      : __ptr_(__p),
+        __deleter_(__d) {}
 
   template <bool _Dummy = true, class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> > >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23
-  unique_ptr(pointer __p, _GoodRValRefType<_Dummy> __d) _NOEXCEPT : __ptr_(__p, _VSTD::move(__d)) {
+  unique_ptr(pointer __p, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
+      : __ptr_(__p),
+        __deleter_(_VSTD::move(__d)) {
     static_assert(!is_reference<deleter_type>::value,
                   "rvalue deleter bound to reference");
   }
@@ -208,28 +211,30 @@
   unique_ptr(pointer __p, _BadRValRefType<_Dummy> __d) = delete;
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(unique_ptr&& __u) _NOEXCEPT
-      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {}
+      : __ptr_(__u.release()),
+        __deleter_(_VSTD::forward<deleter_type>(__u.get_deleter())) {}
 
   template <class _Up,
             class _Ep,
             class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
             class = _EnableIfDeleterConvertible<_Ep> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
-      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}
+      : __ptr_(__u.release()),
+        __deleter_(_VSTD::forward<_Ep>(__u.get_deleter())) {}
 
 #if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
   template <class _Up>
-  _LIBCPP_INLINE_VISIBILITY
-  unique_ptr(auto_ptr<_Up>&& __p,
-             typename enable_if<is_convertible<_Up*, _Tp*>::value &&
-                                    is_same<_Dp, default_delete<_Tp> >::value,
-                                __nat>::type = __nat()) _NOEXCEPT
-      : __ptr_(__p.release(), __value_init_tag()) {}
+  _LIBCPP_INLINE_VISIBILITY unique_ptr(
+      auto_ptr<_Up>&& __p,
+      typename enable_if<is_convertible<_Up*, _Tp*>::value && is_same<_Dp, default_delete<_Tp> >::value, __nat>::type =
+          __nat()) _NOEXCEPT
+      : __ptr_(__p.release()),
+        __deleter_() {}
 #endif
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
     reset(__u.release());
-    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
+    __deleter_ = _VSTD::forward<deleter_type>(__u.get_deleter());
     return *this;
   }
 
@@ -239,7 +244,7 @@
             class = _EnableIfDeleterAssignable<_Ep> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr& operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT {
     reset(__u.release());
-    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
+    __deleter_ = _VSTD::forward<_Ep>(__u.get_deleter());
     return *this;
   }
 
@@ -268,41 +273,37 @@
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 __add_lvalue_reference_t<_Tp> operator*() const {
-    return *__ptr_.first();
-  }
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer operator->() const _NOEXCEPT {
-    return __ptr_.first();
-  }
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer get() const _NOEXCEPT { return __ptr_.first(); }
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 deleter_type& get_deleter() _NOEXCEPT {
-    return __ptr_.second();
+    return *__ptr_;
   }
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer operator->() const _NOEXCEPT { return __ptr_; }
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer get() const _NOEXCEPT { return __ptr_; }
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 deleter_type& get_deleter() _NOEXCEPT { return __deleter_; }
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 const deleter_type& get_deleter() const _NOEXCEPT {
-    return __ptr_.second();
+    return __deleter_;
   }
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 explicit operator bool() const _NOEXCEPT {
-    return __ptr_.first() != nullptr;
+    return __ptr_ != nullptr;
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer release() _NOEXCEPT {
-    pointer __t = __ptr_.first();
-    __ptr_.first() = pointer();
+    pointer __t = __ptr_;
+    __ptr_      = pointer();
     return __t;
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 void reset(pointer __p = pointer()) _NOEXCEPT {
-    pointer __tmp = __ptr_.first();
-    __ptr_.first() = __p;
+    pointer __tmp = __ptr_;
+    __ptr_        = __p;
     if (__tmp)
-      __ptr_.second()(__tmp);
+      __deleter_(__tmp);
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 void swap(unique_ptr& __u) _NOEXCEPT {
-    __ptr_.swap(__u.__ptr_);
+    std::swap(__ptr_, __u.__ptr_);
+    std::swap(__deleter_, __u.__deleter_);
   }
 };
 
-
 template <class _Tp, class _Dp>
 class _LIBCPP_UNIQUE_PTR_TRIVIAL_ABI _LIBCPP_TEMPLATE_VIS unique_ptr<_Tp[], _Dp> {
 public:
@@ -311,7 +312,8 @@
   typedef typename __pointer<_Tp, deleter_type>::type pointer;
 
 private:
-  __compressed_pair<pointer, deleter_type> __ptr_;
+  _LIBCPP_NO_UNIQUE_ADDRESS pointer __ptr_;
+  _LIBCPP_NO_UNIQUE_ADDRESS deleter_type __deleter_;
 
   template <class _From>
   struct _CheckArrayPointerConversion : is_same<_From, pointer> {};
@@ -375,47 +377,48 @@
     >::type;
 
 public:
-  template <bool _Dummy = true,
-            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(__value_init_tag(), __value_init_tag()) {}
+  template <bool _Dummy = true, class = _EnableIfDeleterDefaultConstructible<_Dummy> >
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(), __deleter_() {}
 
-  template <bool _Dummy = true,
-            class = _EnableIfDeleterDefaultConstructible<_Dummy> >
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(__value_init_tag(), __value_init_tag()) {}
+  template <bool _Dummy = true, class = _EnableIfDeleterDefaultConstructible<_Dummy> >
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : unique_ptr() {}
 
   template <class _Pp,
             bool _Dummy = true,
             class       = _EnableIfDeleterDefaultConstructible<_Dummy>,
             class       = _EnableIfPointerConvertible<_Pp> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 explicit unique_ptr(_Pp __p) _NOEXCEPT
-      : __ptr_(__p, __value_init_tag()) {}
+      : __ptr_(__p),
+        __deleter_() {}
 
   template <class _Pp,
             bool _Dummy = true,
             class       = _EnableIfDeleterConstructible<_LValRefType<_Dummy> >,
             class       = _EnableIfPointerConvertible<_Pp> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(_Pp __p, _LValRefType<_Dummy> __d) _NOEXCEPT
-      : __ptr_(__p, __d) {}
+      : __ptr_(__p),
+        __deleter_(__d) {}
 
   template <bool _Dummy = true, class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> > >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(nullptr_t, _LValRefType<_Dummy> __d) _NOEXCEPT
-      : __ptr_(nullptr, __d) {}
+      : __ptr_(nullptr),
+        __deleter_(__d) {}
 
   template <class _Pp,
             bool _Dummy = true,
             class       = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> >,
             class       = _EnableIfPointerConvertible<_Pp> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(_Pp __p, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
-      : __ptr_(__p, _VSTD::move(__d)) {
+      : __ptr_(__p),
+        __deleter_(_VSTD::move(__d)) {
     static_assert(!is_reference<deleter_type>::value,
                   "rvalue deleter bound to reference");
   }
 
   template <bool _Dummy = true, class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy> > >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(nullptr_t, _GoodRValRefType<_Dummy> __d) _NOEXCEPT
-      : __ptr_(nullptr, _VSTD::move(__d)) {
+      : __ptr_(nullptr),
+        __deleter_(_VSTD::move(__d)) {
     static_assert(!is_reference<deleter_type>::value,
                   "rvalue deleter bound to reference");
   }
@@ -427,11 +430,12 @@
   unique_ptr(_Pp __p, _BadRValRefType<_Dummy> __d) = delete;
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(unique_ptr&& __u) _NOEXCEPT
-      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {}
+      : __ptr_(__u.release()),
+        __deleter_(_VSTD::forward<deleter_type>(__u.get_deleter())) {}
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
     reset(__u.release());
-    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
+    __deleter_ = _VSTD::forward<deleter_type>(__u.get_deleter());
     return *this;
   }
 
@@ -440,7 +444,8 @@
             class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
             class = _EnableIfDeleterConvertible<_Ep> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
-      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}
+      : __ptr_(__u.release()),
+        __deleter_(_VSTD::forward<_Ep>(__u.get_deleter())) {}
 
   template <class _Up,
             class _Ep,
@@ -448,7 +453,7 @@
             class = _EnableIfDeleterAssignable<_Ep> >
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 unique_ptr& operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT {
     reset(__u.release());
-    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
+    __deleter_ = _VSTD::forward<_Ep>(__u.get_deleter());
     return *this;
   }
 
@@ -466,24 +471,22 @@
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 __add_lvalue_reference_t<_Tp>
   operator[](size_t __i) const {
-    return __ptr_.first()[__i];
+    return __ptr_[__i];
   }
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer get() const _NOEXCEPT { return __ptr_.first(); }
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer get() const _NOEXCEPT { return __ptr_; }
 
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 deleter_type& get_deleter() _NOEXCEPT {
-    return __ptr_.second();
-  }
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 deleter_type& get_deleter() _NOEXCEPT { return __deleter_; }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 const deleter_type& get_deleter() const _NOEXCEPT {
-    return __ptr_.second();
+    return __deleter_;
   }
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 explicit operator bool() const _NOEXCEPT {
-    return __ptr_.first() != nullptr;
+    return __ptr_ != nullptr;
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 pointer release() _NOEXCEPT {
-    pointer __t = __ptr_.first();
-    __ptr_.first() = pointer();
+    pointer __t = __ptr_;
+    __ptr_      = pointer();
     return __t;
   }
 
@@ -491,21 +494,22 @@
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23
       typename enable_if< _CheckArrayPointerConversion<_Pp>::value >::type
       reset(_Pp __p) _NOEXCEPT {
-    pointer __tmp = __ptr_.first();
-    __ptr_.first() = __p;
+    pointer __tmp = __ptr_;
+    __ptr_        = __p;
     if (__tmp)
-      __ptr_.second()(__tmp);
+      __deleter_(__tmp);
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 void reset(nullptr_t = nullptr) _NOEXCEPT {
-    pointer __tmp = __ptr_.first();
-    __ptr_.first() = nullptr;
+    pointer __tmp = __ptr_;
+    __ptr_        = nullptr;
     if (__tmp)
-      __ptr_.second()(__tmp);
+      __deleter_(__tmp);
   }
 
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX23 void swap(unique_ptr& __u) _NOEXCEPT {
-    __ptr_.swap(__u.__ptr_);
+    std::swap(__ptr_, __u.__ptr_);
+    std::swap(__deleter_, __u.__deleter_);
   }
 };