diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index f2f1ec50d5b75..db918a16e9a61 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -911,6 +911,7 @@ set(files
   __utility/cmp.h
   __utility/convert_to_integral.h
   __utility/declval.h
+  __utility/default_three_way_comparator.h
   __utility/element_count.h
   __utility/empty.h
   __utility/exception_guard.h
@@ -921,6 +922,7 @@ set(files
   __utility/integer_sequence.h
   __utility/is_pointer_in_range.h
   __utility/is_valid_range.h
+  __utility/lazy_synth_three_way_comparator.h
   __utility/move.h
   __utility/no_destroy.h
   __utility/pair.h
diff --git a/libcxx/include/__config b/libcxx/include/__config
index c197851f1c8fe..23b9123fa6917 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -1156,6 +1156,13 @@ typedef __char32_t char32_t;
 #    define _LIBCPP_LIFETIMEBOUND
 #  endif
 
+// This is to work around https://llvm.org/PR156809
+#  ifndef _LIBCPP_CXX03_LANG
+#    define _LIBCPP_CTOR_LIFETIMEBOUND _LIBCPP_LIFETIMEBOUND
+#  else
+#    define _LIBCPP_CTOR_LIFETIMEBOUND
+#  endif
+
 #  if __has_cpp_attribute(_Clang::__noescape__)
 #    define _LIBCPP_NOESCAPE [[_Clang::__noescape__]]
 #  else
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index c5f52f404eff3..8b4bda8c7a3ee 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -34,6 +34,7 @@
 #include <__type_traits/is_swappable.h>
 #include <__type_traits/remove_const.h>
 #include <__utility/forward.h>
+#include <__utility/lazy_synth_three_way_comparator.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
@@ -1749,14 +1750,18 @@ __tree<_Tp, _Compare, _Allocator>::__find_equal(const _Key& __v) {
   }
 
   __node_base_pointer* __node_ptr = __root_ptr();
+  auto __comp                     = __lazy_synth_three_way_comparator<_Compare, _Key, value_type>(value_comp());
+
   while (true) {
-    if (value_comp()(__v, __nd->__get_value())) {
+    auto __comp_res = __comp(__v, __nd->__get_value());
+
+    if (__comp_res.__less()) {
       if (__nd->__left_ == nullptr)
         return _Pair(static_cast<__end_node_pointer>(__nd), __nd->__left_);
 
       __node_ptr = std::addressof(__nd->__left_);
       __nd       = static_cast<__node_pointer>(__nd->__left_);
-    } else if (value_comp()(__nd->__get_value(), __v)) {
+    } else if (__comp_res.__greater()) {
       if (__nd->__right_ == nullptr)
         return _Pair(static_cast<__end_node_pointer>(__nd), __nd->__right_);
 
@@ -2065,10 +2070,12 @@ template <class _Key>
 typename __tree<_Tp, _Compare, _Allocator>::size_type
 __tree<_Tp, _Compare, _Allocator>::__count_unique(const _Key& __k) const {
   __node_pointer __rt = __root();
+  auto __comp         = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __rt = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return 1;
@@ -2082,11 +2089,13 @@ typename __tree<_Tp, _Compare, _Allocator>::size_type
 __tree<_Tp, _Compare, _Allocator>::__count_multi(const _Key& __k) const {
   __end_node_pointer __result = __end_node();
   __node_pointer __rt         = __root();
+  auto __comp                 = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __result = static_cast<__end_node_pointer>(__rt);
       __rt     = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return std::distance(
@@ -2159,11 +2168,13 @@ __tree<_Tp, _Compare, _Allocator>::__equal_range_unique(const _Key& __k) {
   using _Pp                   = pair<iterator, iterator>;
   __end_node_pointer __result = __end_node();
   __node_pointer __rt         = __root();
+  auto __comp                 = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __result = static_cast<__end_node_pointer>(__rt);
       __rt     = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return _Pp(iterator(__rt),
@@ -2181,11 +2192,13 @@ __tree<_Tp, _Compare, _Allocator>::__equal_range_unique(const _Key& __k) const {
   using _Pp                   = pair<const_iterator, const_iterator>;
   __end_node_pointer __result = __end_node();
   __node_pointer __rt         = __root();
+  auto __comp                 = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __result = static_cast<__end_node_pointer>(__rt);
       __rt     = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return _Pp(
@@ -2202,12 +2215,14 @@ pair<typename __tree<_Tp, _Compare, _Allocator>::iterator, typename __tree<_Tp,
 __tree<_Tp, _Compare, _Allocator>::__equal_range_multi(const _Key& __k) {
   using _Pp                   = pair<iterator, iterator>;
   __end_node_pointer __result = __end_node();
-  __node_pointer __rt     = __root();
+  __node_pointer __rt         = __root();
+  auto __comp                 = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __result = static_cast<__end_node_pointer>(__rt);
       __rt     = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return _Pp(__lower_bound(__k, static_cast<__node_pointer>(__rt->__left_), static_cast<__end_node_pointer>(__rt)),
@@ -2223,12 +2238,14 @@ pair<typename __tree<_Tp, _Compare, _Allocator>::const_iterator,
 __tree<_Tp, _Compare, _Allocator>::__equal_range_multi(const _Key& __k) const {
   using _Pp                   = pair<const_iterator, const_iterator>;
   __end_node_pointer __result = __end_node();
-  __node_pointer __rt     = __root();
+  __node_pointer __rt         = __root();
+  auto __comp                 = __lazy_synth_three_way_comparator<value_compare, _Key, value_type>(value_comp());
   while (__rt != nullptr) {
-    if (value_comp()(__k, __rt->__get_value())) {
+    auto __comp_res = __comp(__k, __rt->__get_value());
+    if (__comp_res.__less()) {
       __result = static_cast<__end_node_pointer>(__rt);
       __rt     = static_cast<__node_pointer>(__rt->__left_);
-    } else if (value_comp()(__rt->__get_value(), __k))
+    } else if (__comp_res.__greater())
       __rt = static_cast<__node_pointer>(__rt->__right_);
     else
       return _Pp(__lower_bound(__k, static_cast<__node_pointer>(__rt->__left_), static_cast<__end_node_pointer>(__rt)),
diff --git a/libcxx/include/__utility/default_three_way_comparator.h b/libcxx/include/__utility/default_three_way_comparator.h
new file mode 100644
index 0000000000000..ce423c6ce98e4
--- /dev/null
+++ b/libcxx/include/__utility/default_three_way_comparator.h
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H
+#define _LIBCPP___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H
+
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_arithmetic.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// This struct can be specialized to provide a three way comparator between _LHS and _RHS.
+// The return value should be
+// - less than zero if (lhs_val < rhs_val)
+// - greater than zero if (rhs_val < lhs_val)
+// - zero otherwise
+template <class _LHS, class _RHS, class = void>
+struct __default_three_way_comparator;
+
+template <class _Tp>
+struct __default_three_way_comparator<_Tp, _Tp, __enable_if_t<is_arithmetic<_Tp>::value> > {
+  _LIBCPP_HIDE_FROM_ABI static int operator()(_Tp __lhs, _Tp __rhs) {
+    if (__lhs < __rhs)
+      return -1;
+    if (__lhs > __rhs)
+      return 1;
+    return 0;
+  }
+};
+
+template <class _LHS, class _RHS, bool = true>
+inline const bool __has_default_three_way_comparator_v = false;
+
+template <class _LHS, class _RHS>
+inline const bool
+    __has_default_three_way_comparator_v< _LHS, _RHS, sizeof(__default_three_way_comparator<_LHS, _RHS>) >= 0> = true;
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_DEFAULT_THREE_WAY_COMPARATOR_H
diff --git a/libcxx/include/__utility/lazy_synth_three_way_comparator.h b/libcxx/include/__utility/lazy_synth_three_way_comparator.h
new file mode 100644
index 0000000000000..ca98845f04191
--- /dev/null
+++ b/libcxx/include/__utility/lazy_synth_three_way_comparator.h
@@ -0,0 +1,90 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H
+#define _LIBCPP___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H
+
+#include <__config>
+#include <__type_traits/desugars_to.h>
+#include <__type_traits/enable_if.h>
+#include <__utility/default_three_way_comparator.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+// This file implements a __lazy_synth_three_way_comparator, which tries to build an efficient three way comparison from
+// a binary comparator. That is done in multiple steps:
+// 1) Check whether the comparator desugars to a less-than operator
+//    If that is the case, check whether there exists a specialization of `__default_three_way_comparator`, which
+//    can be specialized to implement a three way comparator for the specific types.
+// 2) Fall back to doing a lazy less than/greater than comparison
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Comparator, class _LHS, class _RHS>
+struct __lazy_compare_result {
+  const _Comparator& __comp_;
+  const _LHS& __lhs_;
+  const _RHS& __rhs_;
+
+  _LIBCPP_HIDE_FROM_ABI
+  __lazy_compare_result(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator& __comp,
+                        _LIBCPP_CTOR_LIFETIMEBOUND const _LHS& __lhs,
+                        _LIBCPP_CTOR_LIFETIMEBOUND const _RHS& __rhs)
+      : __comp_(__comp), __lhs_(__lhs), __rhs_(__rhs) {}
+
+  _LIBCPP_HIDE_FROM_ABI bool __less() const { return __comp_(__lhs_, __rhs_); }
+  _LIBCPP_HIDE_FROM_ABI bool __greater() const { return __comp_(__rhs_, __lhs_); }
+};
+
+// This class provides three way comparison between _LHS and _RHS as efficiently as possible. This can be specialized if
+// a comparator only compares part of the object, potentially allowing an efficient three way comparison between the
+// subobjects. The specialization should use the __lazy_synth_three_way_comparator for the subobjects to achieve this.
+template <class _Comparator, class _LHS, class _RHS, class = void>
+struct __lazy_synth_three_way_comparator {
+  const _Comparator& __comp_;
+
+  _LIBCPP_HIDE_FROM_ABI __lazy_synth_three_way_comparator(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator& __comp)
+      : __comp_(__comp) {}
+
+  _LIBCPP_HIDE_FROM_ABI __lazy_compare_result<_Comparator, _LHS, _RHS>
+  operator()(_LIBCPP_LIFETIMEBOUND const _LHS& __lhs, _LIBCPP_LIFETIMEBOUND const _RHS& __rhs) const {
+    return __lazy_compare_result<_Comparator, _LHS, _RHS>(__comp_, __lhs, __rhs);
+  }
+};
+
+struct __eager_compare_result {
+  int __res_;
+
+  _LIBCPP_HIDE_FROM_ABI explicit __eager_compare_result(int __res) : __res_(__res) {}
+
+  _LIBCPP_HIDE_FROM_ABI bool __less() const { return __res_ < 0; }
+  _LIBCPP_HIDE_FROM_ABI bool __greater() const { return __res_ > 0; }
+};
+
+template <class _Comparator, class _LHS, class _RHS>
+struct __lazy_synth_three_way_comparator<_Comparator,
+                                         _LHS,
+                                         _RHS,
+                                         __enable_if_t<__desugars_to_v<__less_tag, _Comparator, _LHS, _RHS> &&
+                                                       __has_default_three_way_comparator_v<_LHS, _RHS> > > {
+  // This lifetimebound annotation is technically incorrect, but other specializations actually capture the lifetime of
+  // the comparator.
+  _LIBCPP_HIDE_FROM_ABI __lazy_synth_three_way_comparator(_LIBCPP_CTOR_LIFETIMEBOUND const _Comparator&) {}
+
+  // Same comment as above.
+  _LIBCPP_HIDE_FROM_ABI static __eager_compare_result
+  operator()(_LIBCPP_LIFETIMEBOUND const _LHS& __lhs, _LIBCPP_LIFETIMEBOUND const _RHS& __rhs) {
+    return __eager_compare_result(__default_three_way_comparator<_LHS, _RHS>()(__lhs, __rhs));
+  }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_LAZY_SYNTH_THREE_WAY_COMPARATOR_H
diff --git a/libcxx/include/map b/libcxx/include/map
index a734df671fd6f..f428c781e5036 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -603,6 +603,7 @@ erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
 #  include <__type_traits/remove_const.h>
 #  include <__type_traits/type_identity.h>
 #  include <__utility/forward.h>
+#  include <__utility/lazy_synth_three_way_comparator.h>
 #  include <__utility/pair.h>
 #  include <__utility/piecewise_construct.h>
 #  include <__utility/swap.h>
@@ -702,6 +703,50 @@ public:
 #  endif
 };
 
+#  if _LIBCPP_STD_VER >= 14
+template <class _MapValueT, class _Key, class _Compare>
+struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _Compare>, _MapValueT, _MapValueT> {
+  __lazy_synth_three_way_comparator<_Compare, _Key, _Key> __comp_;
+
+  __lazy_synth_three_way_comparator(
+      _LIBCPP_CTOR_LIFETIMEBOUND const __map_value_compare<_Key, _MapValueT, _Compare>& __comp)
+      : __comp_(__comp.key_comp()) {}
+
+  _LIBCPP_HIDE_FROM_ABI auto
+  operator()(_LIBCPP_LIFETIMEBOUND const _MapValueT& __lhs, _LIBCPP_LIFETIMEBOUND const _MapValueT& __rhs) const {
+    return __comp_(__lhs.first, __rhs.first);
+  }
+};
+
+template <class _MapValueT, class _Key, class _TransparentKey, class _Compare>
+struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _Compare>, _TransparentKey, _MapValueT> {
+  __lazy_synth_three_way_comparator<_Compare, _TransparentKey, _Key> __comp_;
+
+  __lazy_synth_three_way_comparator(
+      _LIBCPP_CTOR_LIFETIMEBOUND const __map_value_compare<_Key, _MapValueT, _Compare>& __comp)
+      : __comp_(__comp.key_comp()) {}
+
+  _LIBCPP_HIDE_FROM_ABI auto
+  operator()(_LIBCPP_LIFETIMEBOUND const _TransparentKey& __lhs, _LIBCPP_LIFETIMEBOUND const _MapValueT& __rhs) const {
+    return __comp_(__lhs, __rhs.first);
+  }
+};
+
+template <class _MapValueT, class _Key, class _TransparentKey, class _Compare>
+struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _Compare>, _MapValueT, _TransparentKey> {
+  __lazy_synth_three_way_comparator<_Compare, _Key, _TransparentKey> __comp_;
+
+  __lazy_synth_three_way_comparator(
+      _LIBCPP_CTOR_LIFETIMEBOUND const __map_value_compare<_Key, _MapValueT, _Compare>& __comp)
+      : __comp_(__comp.key_comp()) {}
+
+  _LIBCPP_HIDE_FROM_ABI auto
+  operator()(_LIBCPP_LIFETIMEBOUND const _MapValueT& __lhs, _LIBCPP_LIFETIMEBOUND const _TransparentKey& __rhs) const {
+    return __comp_(__lhs.first, __rhs);
+  }
+};
+#  endif // _LIBCPP_STD_VER >= 14
+
 template <class _Key, class _CP, class _Compare, bool __b>
 inline _LIBCPP_HIDE_FROM_ABI void
 swap(__map_value_compare<_Key, _CP, _Compare, __b>& __x, __map_value_compare<_Key, _CP, _Compare, __b>& __y)
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index 7ac7b510f826a..63cf8e847751f 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -2144,41 +2144,43 @@ module std [system] {
   }
 
   module utility {
-    module as_const                   { header "__utility/as_const.h" }
-    module as_lvalue                  { header "__utility/as_lvalue.h" }
-    module auto_cast                  {
+    module as_const                        { header "__utility/as_const.h" }
+    module as_lvalue                       { header "__utility/as_lvalue.h" }
+    module auto_cast                       {
       header "__utility/auto_cast.h"
       export std_core.type_traits.decay // the macro expansion uses that trait
     }
-    module cmp                        { header "__utility/cmp.h" }
-    module convert_to_integral        { header "__utility/convert_to_integral.h" }
-    module element_count              { header "__utility/element_count.h" }
-    module exception_guard            { header "__utility/exception_guard.h" }
-    module exchange                   { header "__utility/exchange.h" }
-    module forward_like               { header "__utility/forward_like.h" }
-    module in_place {
+    module cmp                             { header "__utility/cmp.h" }
+    module convert_to_integral             { header "__utility/convert_to_integral.h" }
+    module default_three_way_comparator    { header "__utility/default_three_way_comparator.h" }
+    module element_count                   { header "__utility/element_count.h" }
+    module exception_guard                 { header "__utility/exception_guard.h" }
+    module exchange                        { header "__utility/exchange.h" }
+    module forward_like                    { header "__utility/forward_like.h" }
+    module in_place                        {
       header "__utility/in_place.h"
       export std_core.type_traits.integral_constant
     }
-    module integer_sequence           { header "__utility/integer_sequence.h" }
-    module is_pointer_in_range        { header "__utility/is_pointer_in_range.h" }
-    module is_valid_range             { header "__utility/is_valid_range.h" }
-    module move                       { header "__utility/move.h" }
-    module no_destroy                 { header "__utility/no_destroy.h" }
-    module pair                       {
+    module integer_sequence                { header "__utility/integer_sequence.h" }
+    module is_pointer_in_range             { header "__utility/is_pointer_in_range.h" }
+    module is_valid_range                  { header "__utility/is_valid_range.h" }
+    module lazy_synth_three_way_comparator { header "__utility/lazy_synth_three_way_comparator.h" }
+    module move                            { header "__utility/move.h" }
+    module no_destroy                      { header "__utility/no_destroy.h" }
+    module pair                            {
       header "__utility/pair.h"
       export std.utility.piecewise_construct
     }
-    module piecewise_construct        { header "__utility/piecewise_construct.h" }
-    module priority_tag               { header "__utility/priority_tag.h" }
-    module private_constructor_tag    { header "__utility/private_constructor_tag.h" }
-    module rel_ops                    { header "__utility/rel_ops.h" }
-    module scope_guard                { header "__utility/scope_guard.h" }
-    module small_buffer               { header "__utility/small_buffer.h" }
-    module swap                       { header "__utility/swap.h" }
-    module to_underlying              { header "__utility/to_underlying.h" }
-    module try_key_extraction         { header "__utility/try_key_extraction.h" }
-    module unreachable                { header "__utility/unreachable.h" }
+    module piecewise_construct             { header "__utility/piecewise_construct.h" }
+    module priority_tag                    { header "__utility/priority_tag.h" }
+    module private_constructor_tag         { header "__utility/private_constructor_tag.h" }
+    module rel_ops                         { header "__utility/rel_ops.h" }
+    module scope_guard                     { header "__utility/scope_guard.h" }
+    module small_buffer                    { header "__utility/small_buffer.h" }
+    module swap                            { header "__utility/swap.h" }
+    module to_underlying                   { header "__utility/to_underlying.h" }
+    module try_key_extraction              { header "__utility/try_key_extraction.h" }
+    module unreachable                     { header "__utility/unreachable.h" }
 
     header "utility"
     export *
diff --git a/libcxx/include/string b/libcxx/include/string
index 19a538d96e85c..0abdfebcb863f 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -639,13 +639,12 @@ basic_string<char32_t> operator""s( const char32_t *str, size_t len );
 #  include <__type_traits/remove_cvref.h>
 #  include <__type_traits/void_t.h>
 #  include <__utility/auto_cast.h>
-#  include <__utility/declval.h>
+#  include <__utility/default_three_way_comparator.h>
 #  include <__utility/forward.h>
 #  include <__utility/is_pointer_in_range.h>
 #  include <__utility/move.h>
 #  include <__utility/scope_guard.h>
 #  include <__utility/swap.h>
-#  include <__utility/unreachable.h>
 #  include <climits>
 #  include <cstdio> // EOF
 #  include <cstring>
@@ -966,7 +965,7 @@ private:
         std::__wrap_iter<const_pointer>(__get_pointer() + size()));
 #  else
     return const_iterator(__p);
-#  endif // _LIBCPP_ABI_BOUNDED_ITERATORS_IN_STRING
+#  endif                    // _LIBCPP_ABI_BOUNDED_ITERATORS_IN_STRING
   }
 
 public:
@@ -2522,6 +2521,19 @@ _LIBCPP_STRING_V1_EXTERN_TEMPLATE_LIST(_LIBCPP_DECLARE, wchar_t)
 #  endif
 #  undef _LIBCPP_DECLARE
 
+template <class _CharT, class _Traits, class _Alloc>
+struct __default_three_way_comparator<basic_string<_CharT, _Traits, _Alloc>, basic_string<_CharT, _Traits, _Alloc> > {
+  using __string_t _LIBCPP_NODEBUG = basic_string<_CharT, _Traits, _Alloc>;
+
+  _LIBCPP_HIDE_FROM_ABI static int operator()(const __string_t& __lhs, const __string_t& __rhs) {
+    auto __min_len = std::min(__lhs.size(), __rhs.size());
+    auto __ret     = _Traits::compare(__lhs.data(), __rhs.data(), __min_len);
+    if (__ret == 0)
+      return __lhs.size() == __rhs.size() ? 0 : __lhs.size() < __rhs.size() ? -1 : 1;
+    return __ret;
+  }
+};
+
 #  if _LIBCPP_STD_VER >= 17
 template <class _InputIterator,
           class _CharT     = __iter_value_type<_InputIterator>,
diff --git a/libcxx/test/std/experimental/utilities/meta/meta.detect/detected_t.pass.cpp b/libcxx/test/std/experimental/utilities/meta/meta.detect/detected_t.pass.cpp
index b64b86f1b05ea..4f9f26cb4587b 100644
--- a/libcxx/test/std/experimental/utilities/meta/meta.detect/detected_t.pass.cpp
+++ b/libcxx/test/std/experimental/utilities/meta/meta.detect/detected_t.pass.cpp
@@ -11,6 +11,7 @@
 
 #include <experimental/type_traits>
 #include <string>
+#include <utility>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected.pass.cpp b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected.pass.cpp
index 4a977917f1ec6..6960c71abb33e 100644
--- a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected.pass.cpp
+++ b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected.pass.cpp
@@ -11,6 +11,7 @@
 
 #include <experimental/type_traits>
 #include <string>
+#include <utility>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_convertible.pass.cpp b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_convertible.pass.cpp
index 6906461f1edcc..de1d223b91897 100644
--- a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_convertible.pass.cpp
+++ b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_convertible.pass.cpp
@@ -11,6 +11,7 @@
 
 #include <experimental/type_traits>
 #include <string>
+#include <utility>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_exact.pass.cpp b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_exact.pass.cpp
index 500187e86dd08..2161c11e7d2c2 100644
--- a/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_exact.pass.cpp
+++ b/libcxx/test/std/experimental/utilities/meta/meta.detect/is_detected_exact.pass.cpp
@@ -11,6 +11,7 @@
 
 #include <experimental/type_traits>
 #include <string>
+#include <utility>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp b/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
index c3d3e0cfc411b..8e2f84fba0def 100644
--- a/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
+++ b/libcxx/test/std/input.output/iostreams.base/fpos/fpos.operations/fpos.pass.cpp
@@ -14,6 +14,7 @@
 #include <cassert>
 #include <ios>
 #include <type_traits>
+#include <utility>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/support/any_helpers.h b/libcxx/test/support/any_helpers.h
index 0e5563142d58a..66f393b108cc5 100644
--- a/libcxx/test/support/any_helpers.h
+++ b/libcxx/test/support/any_helpers.h
@@ -9,9 +9,10 @@
 #ifndef ANY_HELPERS_H
 #define ANY_HELPERS_H
 
+#include <cassert>
 #include <typeinfo>
 #include <type_traits>
-#include <cassert>
+#include <utility>
 
 namespace std { namespace experimental {} }