[libc++] Split __compressed_pair out of <memory>

Differential Revision: https://reviews.llvm.org/D100318

GitOrigin-RevId: 9b0a3388eb36e43120495f3e9063dfae898fc9ac
diff --git a/include/memory b/include/memory
index aabbfdc..fcfc10b 100644
--- a/include/memory
+++ b/include/memory
@@ -683,6 +683,7 @@
 #include <__memory/allocator_traits.h>
 #include <__memory/auto_ptr.h>
 #include <__memory/base.h>
+#include <__memory/compressed_pair.h>
 #include <__memory/pointer_traits.h>
 #include <__memory/temporary_buffer.h>
 #include <__memory/utilities.h>
@@ -839,175 +840,6 @@
 #endif
 };
 
-// Tag used to default initialize one or both of the pair's elements.
-struct __default_init_tag {};
-struct __value_init_tag {};
-
-template <class _Tp, int _Idx,
-          bool _CanBeEmptyBase =
-              is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
-struct __compressed_pair_elem {
-  typedef _Tp _ParamT;
-  typedef _Tp& reference;
-  typedef const _Tp& const_reference;
-
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  __compressed_pair_elem(__default_init_tag) {}
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  __compressed_pair_elem(__value_init_tag) : __value_() {}
-
-  template <class _Up, class = typename enable_if<
-      !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
-  >::type>
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR explicit
-  __compressed_pair_elem(_Up&& __u)
-      : __value_(_VSTD::forward<_Up>(__u))
-    {
-    }
-
-
-#ifndef _LIBCPP_CXX03_LANG
-  template <class... _Args, size_t... _Indexes>
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
-                         __tuple_indices<_Indexes...>)
-      : __value_(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
-#endif
-
-
-  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return __value_; }
-  _LIBCPP_INLINE_VISIBILITY
-  const_reference __get() const _NOEXCEPT { return __value_; }
-
-private:
-  _Tp __value_;
-};
-
-template <class _Tp, int _Idx>
-struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
-  typedef _Tp _ParamT;
-  typedef _Tp& reference;
-  typedef const _Tp& const_reference;
-  typedef _Tp __value_type;
-
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __compressed_pair_elem() = default;
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  __compressed_pair_elem(__default_init_tag) {}
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  __compressed_pair_elem(__value_init_tag) : __value_type() {}
-
-  template <class _Up, class = typename enable_if<
-        !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
-  >::type>
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR explicit
-  __compressed_pair_elem(_Up&& __u)
-      : __value_type(_VSTD::forward<_Up>(__u))
-  {}
-
-#ifndef _LIBCPP_CXX03_LANG
-  template <class... _Args, size_t... _Indexes>
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
-                         __tuple_indices<_Indexes...>)
-      : __value_type(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
-#endif
-
-  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return *this; }
-  _LIBCPP_INLINE_VISIBILITY
-  const_reference __get() const _NOEXCEPT { return *this; }
-};
-
-template <class _T1, class _T2>
-class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
-                          private __compressed_pair_elem<_T2, 1> {
-public:
-  // NOTE: This static assert should never fire because __compressed_pair
-  // is *almost never* used in a scenario where it's possible for T1 == T2.
-  // (The exception is std::function where it is possible that the function
-  //  object and the allocator have the same type).
-  static_assert((!is_same<_T1, _T2>::value),
-    "__compressed_pair cannot be instantiated when T1 and T2 are the same type; "
-    "The current implementation is NOT ABI-compatible with the previous "
-    "implementation for this configuration");
-
-    typedef _LIBCPP_NODEBUG_TYPE __compressed_pair_elem<_T1, 0> _Base1;
-    typedef _LIBCPP_NODEBUG_TYPE __compressed_pair_elem<_T2, 1> _Base2;
-
-    template <bool _Dummy = true,
-      class = typename enable_if<
-          __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
-          __dependent_type<is_default_constructible<_T2>, _Dummy>::value
-      >::type
-  >
-  _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR __compressed_pair() : _Base1(__value_init_tag()), _Base2(__value_init_tag()) {}
-
-  template <class _U1, class _U2>
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  __compressed_pair(_U1&& __t1, _U2&& __t2)
-      : _Base1(_VSTD::forward<_U1>(__t1)), _Base2(_VSTD::forward<_U2>(__t2)) {}
-
-#ifndef _LIBCPP_CXX03_LANG
-  template <class... _Args1, class... _Args2>
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
-  __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
-                    tuple<_Args2...> __second_args)
-      : _Base1(__pc, _VSTD::move(__first_args),
-               typename __make_tuple_indices<sizeof...(_Args1)>::type()),
-        _Base2(__pc, _VSTD::move(__second_args),
-               typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
-#endif
-
-  _LIBCPP_INLINE_VISIBILITY
-  typename _Base1::reference first() _NOEXCEPT {
-    return static_cast<_Base1&>(*this).__get();
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  typename _Base1::const_reference first() const _NOEXCEPT {
-    return static_cast<_Base1 const&>(*this).__get();
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  typename _Base2::reference second() _NOEXCEPT {
-    return static_cast<_Base2&>(*this).__get();
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  typename _Base2::const_reference second() const _NOEXCEPT {
-    return static_cast<_Base2 const&>(*this).__get();
-  }
-
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  static _Base1* __get_first_base(__compressed_pair* __pair) _NOEXCEPT {
-    return static_cast<_Base1*>(__pair);
-  }
-  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-  static _Base2* __get_second_base(__compressed_pair* __pair) _NOEXCEPT {
-    return static_cast<_Base2*>(__pair);
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  void swap(__compressed_pair& __x)
-    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-               __is_nothrow_swappable<_T2>::value)
-  {
-    using _VSTD::swap;
-    swap(first(), __x.first());
-    swap(second(), __x.second());
-  }
-};
-
-template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
-void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
-    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-               __is_nothrow_swappable<_T2>::value) {
-  __x.swap(__y);
-}
-
 // default_delete
 
 template <class _Tp>