Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 247 insertions, 92 deletions

diff --git a/contrib/libc++/include/utility b/contrib/libc++/include/utility
index a151640..cc0646c 100644
--- a/contrib/libc++/include/utility
+++ b/contrib/libc++/include/utility
@@ -171,6 +171,25 @@ template<class... T>
 
 template<class T, class U=T>
     T exchange(T& obj, U&& new_value);
+
+// 20.2.7, in-place construction // C++17
+struct in_place_t {
+  explicit in_place_t() = default;
+};
+inline constexpr in_place_t in_place{};
+template <class T>
+  struct in_place_type_t {
+    explicit in_place_type_t() = default;
+  };
+template <class T>
+  inline constexpr in_place_type_t<T> in_place_type{};
+template <size_t I>
+  struct in_place_index_t {
+    explicit in_place_index_t() = default;
+  };
+template <size_t I>
+  inline constexpr in_place_index_t<I> in_place_index{};
+
 }  // std
 
 */
@@ -179,6 +198,7 @@ template<class T, class U=T>
 #include <__tuple>
 #include <type_traits>
 #include <initializer_list>
+#include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -269,7 +289,7 @@ template <class _Tp> constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { r
 template <class _Tp>                        void as_const(const _Tp&&) = delete;
 #endif
 
-struct _LIBCPP_TYPE_VIS_ONLY piecewise_construct_t { };
+struct _LIBCPP_TEMPLATE_VIS piecewise_construct_t { };
 #if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_UTILITY)
 extern const piecewise_construct_t piecewise_construct;// = piecewise_construct_t();
 #else
@@ -286,7 +306,7 @@ struct __non_trivially_copyable_base {
 #endif
 
 template <class _T1, class _T2>
-struct _LIBCPP_TYPE_VIS_ONLY pair
+struct _LIBCPP_TEMPLATE_VIS pair
 #if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
 : private __non_trivially_copyable_base
 #endif
@@ -297,28 +317,6 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
     _T1 first;
     _T2 second;
 
-#ifndef _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
-    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>
-#endif
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR pair() : first(), second() {}
-
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    pair(const _T1& __x, const _T2& __y)
-        : first(__x), second(__y) {}
-
-    template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(const pair<_U1, _U2>& __p
-#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
-                 ,typename enable_if<is_convertible<const _U1&, _T1>::value &&
-                                    is_convertible<const _U2&, _T2>::value>::type* = 0
-#endif
-                                      )
-            : first(__p.first), second(__p.second) {}
-
 #if !defined(_LIBCPP_CXX03_LANG)
     pair(pair const&) = default;
     pair(pair&&) = default;
@@ -326,8 +324,172 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
   // Use the implicitly declared copy constructor in C++03
 #endif
 
+#ifdef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    pair() : first(), second() {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    pair(_T1 const& __t1, _T2 const& __t2) : first(__t1), second(__t2) {}
+
+    template <class _U1, class _U2>
     _LIBCPP_INLINE_VISIBILITY
-    pair& operator=(const pair& __p)
+    pair(const pair<_U1, _U2>& __p) : first(__p.first), second(__p.second) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(pair const& __p) {
+        first = __p.first;
+        second = __p.second;
+        return *this;
+    }
+#else
+    template <bool _Val>
+    using _EnableB = typename enable_if<_Val, bool>::type;
+
+    struct _CheckArgs {
+      template <class _U1, class _U2>
+      static constexpr bool __enable_default() {
+          return is_default_constructible<_U1>::value
+              && is_default_constructible<_U2>::value;
+      }
+
+      template <class _U1, class _U2>
+      static constexpr bool __enable_explicit() {
+          return is_constructible<first_type, _U1>::value
+              && is_constructible<second_type, _U2>::value
+              && (!is_convertible<_U1, first_type>::value
+                  || !is_convertible<_U2, second_type>::value);
+      }
+
+      template <class _U1, class _U2>
+      static constexpr bool __enable_implicit() {
+          return is_constructible<first_type, _U1>::value
+              && is_constructible<second_type, _U2>::value
+              && is_convertible<_U1, first_type>::value
+              && is_convertible<_U2, second_type>::value;
+      }
+    };
+
+    template <bool _MaybeEnable>
+    using _CheckArgsDep = typename conditional<
+      _MaybeEnable, _CheckArgs, __check_tuple_constructor_fail>::type;
+
+    struct _CheckTupleLikeConstructor {
+        template <class _Tuple>
+        static constexpr bool __enable_implicit() {
+            return __tuple_convertible<_Tuple, pair>::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_explicit() {
+            return __tuple_constructible<_Tuple, pair>::value
+               && !__tuple_convertible<_Tuple, pair>::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_assign() {
+            return __tuple_assignable<_Tuple, pair>::value;
+        }
+    };
+
+    template <class _Tuple>
+    using _CheckTLC = typename conditional<
+        __tuple_like_with_size<_Tuple, 2>::value
+            && !is_same<typename decay<_Tuple>::type, pair>::value,
+        _CheckTupleLikeConstructor,
+        __check_tuple_constructor_fail
+    >::type;
+
+    template<bool _Dummy = true, _EnableB<
+            _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    pair() : first(), second() {}
+
+    template <bool _Dummy = true, _EnableB<
+             _CheckArgsDep<_Dummy>::template __enable_explicit<_T1 const&, _T2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_T1 const& __t1, _T2 const& __t2)
+        : first(__t1), second(__t2) {}
+
+    template<bool _Dummy = true, _EnableB<
+            _CheckArgsDep<_Dummy>::template __enable_implicit<_T1 const&, _T2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_T1 const& __t1, _T2 const& __t2)
+        : first(__t1), second(__t2) {}
+
+    template<class _U1, class _U2, _EnableB<
+             _CheckArgs::template __enable_explicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_U1&& __u1, _U2&& __u2)
+        : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_U1&& __u1, _U2&& __u2)
+        : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_explicit<_U1 const&, _U2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(pair<_U1, _U2> const& __p)
+        : first(__p.first), second(__p.second) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1 const&, _U2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(pair<_U1, _U2> const& __p)
+        : first(__p.first), second(__p.second) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_explicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(pair<_U1, _U2>&&__p)
+        : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(pair<_U1, _U2>&& __p)
+        : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
+
+    template<class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_explicit<_Tuple>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_Tuple&& __p)
+        : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
+          second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
+
+    template<class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_implicit<_Tuple>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_Tuple&& __p)
+        : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
+          second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
+
+    template <class... _Args1, class... _Args2>
+    _LIBCPP_INLINE_VISIBILITY
+    pair(piecewise_construct_t __pc,
+         tuple<_Args1...> __first_args, tuple<_Args2...> __second_args)
+        : pair(__pc, __first_args, __second_args,
+                typename __make_tuple_indices<sizeof...(_Args1)>::type(),
+                typename __make_tuple_indices<sizeof...(_Args2) >::type()) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(typename conditional<
+                        is_copy_assignable<first_type>::value &&
+                        is_copy_assignable<second_type>::value,
+                    pair, __nat>::type const& __p)
         _NOEXCEPT_(is_nothrow_copy_assignable<first_type>::value &&
                    is_nothrow_copy_assignable<second_type>::value)
     {
@@ -336,75 +498,30 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
         return *this;
     }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    template <class _U1, class _U2,
-              class = typename enable_if<is_convertible<_U1, first_type>::value &&
-                                         is_convertible<_U2, second_type>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(_U1&& __u1, _U2&& __u2)
-            : first(_VSTD::forward<_U1>(__u1)),
-              second(_VSTD::forward<_U2>(__u2))
-            {}
-
-    template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(pair<_U1, _U2>&& __p,
-                 typename enable_if<is_convertible<_U1, _T1>::value &&
-                                    is_convertible<_U2, _T2>::value>::type* = 0)
-            : first(_VSTD::forward<_U1>(__p.first)),
-              second(_VSTD::forward<_U2>(__p.second)) {}
-
     _LIBCPP_INLINE_VISIBILITY
-    pair&
-    operator=(pair&& __p) _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
-                                     is_nothrow_move_assignable<second_type>::value)
+    pair& operator=(typename conditional<
+                        is_move_assignable<first_type>::value &&
+                        is_move_assignable<second_type>::value,
+                    pair, __nat>::type&& __p)
+        _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
+                   is_nothrow_move_assignable<second_type>::value)
     {
         first = _VSTD::forward<first_type>(__p.first);
         second = _VSTD::forward<second_type>(__p.second);
         return *this;
     }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-    template<class _Tuple,
-             class = typename enable_if<__tuple_convertible<_Tuple, pair>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(_Tuple&& __p)
-            : first(_VSTD::forward<typename tuple_element<0,
-                                  typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<0>(__p))),
-              second(_VSTD::forward<typename tuple_element<1,
-                                   typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<1>(__p)))
-            {}
-
-
-
-    template <class... _Args1, class... _Args2>
-        _LIBCPP_INLINE_VISIBILITY
-        pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
-                                    tuple<_Args2...> __second_args)
-            : pair(__pc, __first_args, __second_args,
-                   typename __make_tuple_indices<sizeof...(_Args1)>::type(),
-                   typename __make_tuple_indices<sizeof...(_Args2) >::type())
-            {}
-
-    template <class _Tuple,
-              class = typename enable_if<__tuple_assignable<_Tuple, pair>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY
-        pair&
-        operator=(_Tuple&& __p)
-        {
-            typedef typename __make_tuple_types<_Tuple>::type _TupleRef;
-            typedef typename tuple_element<0, _TupleRef>::type _U0;
-            typedef typename tuple_element<1, _TupleRef>::type _U1;
-            first  = _VSTD::forward<_U0>(_VSTD::get<0>(__p));
-            second = _VSTD::forward<_U1>(_VSTD::get<1>(__p));
-            return *this;
-        }
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+    template <class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_assign<_Tuple>()
+     > = false>
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(_Tuple&& __p) {
+        first = _VSTD::get<0>(_VSTD::forward<_Tuple>(__p));
+        second = _VSTD::get<1>(_VSTD::forward<_Tuple>(__p));
+        return *this;
+    }
+#endif
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     void
     swap(pair& __p) _NOEXCEPT_(__is_nothrow_swappable<first_type>::value &&
@@ -416,13 +533,13 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
     }
 private:
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
         _LIBCPP_INLINE_VISIBILITY
         pair(piecewise_construct_t,
              tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
              __tuple_indices<_I1...>, __tuple_indices<_I2...>);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif
 };
 
 template <class _T1, class _T2>
@@ -531,18 +648,18 @@ make_pair(_T1 __x, _T2 __y)
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template <class _T1, class _T2>
-  class _LIBCPP_TYPE_VIS_ONLY tuple_size<pair<_T1, _T2> >
+  class _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> >
     : public integral_constant<size_t, 2> {};
 
 template <class _T1, class _T2>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<0, pair<_T1, _T2> >
+class _LIBCPP_TEMPLATE_VIS tuple_element<0, pair<_T1, _T2> >
 {
 public:
     typedef _T1 type;
 };
 
 template <class _T1, class _T2>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<1, pair<_T1, _T2> >
+class _LIBCPP_TEMPLATE_VIS tuple_element<1, pair<_T1, _T2> >
 {
 public:
     typedef _T2 type;
@@ -712,7 +829,7 @@ constexpr _T1 const && get(pair<_T2, _T1> const&& __p) _NOEXCEPT
 #if _LIBCPP_STD_VER > 11
 
 template<class _Tp, _Tp... _Ip>
-struct _LIBCPP_TYPE_VIS_ONLY integer_sequence
+struct _LIBCPP_TEMPLATE_VIS integer_sequence
 {
     typedef _Tp value_type;
     static_assert( is_integral<_Tp>::value,
@@ -775,6 +892,44 @@ _T1 exchange(_T1& __obj, _T2 && __new_value)
 }
 #endif  // _LIBCPP_STD_VER > 11
 
+#if _LIBCPP_STD_VER > 14
+
+struct _LIBCPP_TYPE_VIS in_place_t {
+    explicit in_place_t() = default;
+};
+#ifndef _LIBCPP_HAS_NO_INLINE_VARIABLES
+inline
+#endif
+constexpr in_place_t in_place{};
+
+template <class _Tp>
+struct _LIBCPP_TYPE_VIS in_place_type_t {
+    explicit in_place_type_t() = default;
+};
+template <class _Tp>
+#ifndef _LIBCPP_HAS_NO_INLINE_VARIABLES
+inline
+#endif
+constexpr in_place_type_t<_Tp> in_place_type{};
+
+template <size_t _Idx>
+struct _LIBCPP_TYPE_VIS in_place_index_t {
+    explicit in_place_index_t() = default;
+};
+template <size_t _Idx>
+#ifndef _LIBCPP_HAS_NO_INLINE_VARIABLES
+inline
+#endif
+constexpr in_place_index_t<_Idx> in_place_index{};
+
+template <class _Tp> struct __is_inplace_type_imp : false_type {};
+template <class _Tp> struct __is_inplace_type_imp<in_place_type_t<_Tp>> : true_type {};
+
+template <class _Tp>
+using __is_inplace_type = __is_inplace_type_imp<__uncvref_t<_Tp>>;
+
+#endif // _LIBCPP_STD_VER > 14
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_UTILITY