diff --git a/docs/Status/Cxx20Issues.csv b/docs/Status/Cxx20Issues.csv
index c7ba72c..82ead0d 100644
--- a/docs/Status/Cxx20Issues.csv
+++ b/docs/Status/Cxx20Issues.csv
@@ -244,7 +244,7 @@
 "`3320 <https://wg21.link/LWG3320>`__","``span::cbegin/cend``\  methods produce different results than ``std::[ranges::]cbegin/cend``\ ","Prague","|Complete|",""
 "`3321 <https://wg21.link/LWG3321>`__","``uninitialized_construct_using_allocator``\  should use ``construct_at``\ ","Prague","",""
 "`3323 <https://wg21.link/LWG3323>`__","``*has-tuple-element*``\  helper concept needs ``convertible_to``\ ","Prague","","","|ranges|"
-"`3324 <https://wg21.link/LWG3324>`__","Special-case ``std::strong/weak/partial_order``\  for pointers","Prague","","","|spaceship|"
+"`3324 <https://wg21.link/LWG3324>`__","Special-case ``std::strong/weak/partial_order``\  for pointers","Prague","|Complete|","14.0","|spaceship|"
 "`3325 <https://wg21.link/LWG3325>`__","Constrain return type of transformation function for ``transform_view``\ ","Prague","","","|ranges|"
 "`3326 <https://wg21.link/LWG3326>`__","``enable_view``\  has false positives","Prague","|In progress|","","|ranges|"
 "`3327 <https://wg21.link/LWG3327>`__","Format alignment specifiers vs. text direction","Prague","|Nothing To Do|","","|format|"
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index ac6038b..4693229 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -107,8 +107,11 @@
   __compare/compare_three_way_result.h
   __compare/is_eq.h
   __compare/ordering.h
+  __compare/partial_order.h
+  __compare/strong_order.h
   __compare/synth_three_way.h
   __compare/three_way_comparable.h
+  __compare/weak_order.h
   __concepts/arithmetic.h
   __concepts/assignable.h
   __concepts/boolean_testable.h
@@ -334,6 +337,7 @@
   __utility/move.h
   __utility/pair.h
   __utility/piecewise_construct.h
+  __utility/priority_tag.h
   __utility/rel_ops.h
   __utility/swap.h
   __utility/to_underlying.h
diff --git a/include/__compare/partial_order.h b/include/__compare/partial_order.h
new file mode 100644
index 0000000..ac8b405
--- /dev/null
+++ b/include/__compare/partial_order.h
@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___COMPARE_PARTIAL_ORDER
+#define _LIBCPP___COMPARE_PARTIAL_ORDER
+
+#include <__compare/compare_three_way.h>
+#include <__compare/ordering.h>
+#include <__compare/weak_order.h>
+#include <__config>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+#include <type_traits>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [cmp.alg]
+namespace __partial_order {
+    struct __fn {
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<2>)
+            noexcept(noexcept(partial_ordering(partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      partial_ordering(partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          partial_ordering(partial_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<1>)
+            noexcept(noexcept(partial_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      partial_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          partial_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<0>)
+            noexcept(noexcept(partial_ordering(_VSTD::weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      partial_ordering(_VSTD::weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          partial_ordering(_VSTD::weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+        _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+            noexcept(noexcept(__go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>())))
+            -> decltype(      __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()))
+            { return          __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()); }
+    };
+} // namespace __partial_order
+
+inline namespace __cpo {
+    inline constexpr auto partial_order = __partial_order::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_PARTIAL_ORDER
diff --git a/include/__compare/strong_order.h b/include/__compare/strong_order.h
new file mode 100644
index 0000000..e49b2d4
--- /dev/null
+++ b/include/__compare/strong_order.h
@@ -0,0 +1,136 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___COMPARE_STRONG_ORDER
+#define _LIBCPP___COMPARE_STRONG_ORDER
+
+#include <__bit/bit_cast.h>
+#include <__compare/compare_three_way.h>
+#include <__compare/ordering.h>
+#include <__config>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+#include <cmath>
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [cmp.alg]
+namespace __strong_order {
+    struct __fn {
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<2>)
+            noexcept(noexcept(strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          strong_ordering(strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up, class _Dp = decay_t<_Tp>>
+            requires is_same_v<_Dp, decay_t<_Up>> && is_floating_point_v<_Dp>
+        _LIBCPP_HIDE_FROM_ABI static constexpr strong_ordering
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept
+        {
+            if constexpr (numeric_limits<_Dp>::is_iec559 && sizeof(_Dp) == sizeof(int32_t)) {
+                int32_t __rx = _VSTD::bit_cast<int32_t>(__t);
+                int32_t __ry = _VSTD::bit_cast<int32_t>(__u);
+                __rx = (__rx < 0) ? (numeric_limits<int32_t>::min() - __rx - 1) : __rx;
+                __ry = (__ry < 0) ? (numeric_limits<int32_t>::min() - __ry - 1) : __ry;
+                return (__rx <=> __ry);
+            } else if constexpr (numeric_limits<_Dp>::is_iec559 && sizeof(_Dp) == sizeof(int64_t)) {
+                int64_t __rx = _VSTD::bit_cast<int64_t>(__t);
+                int64_t __ry = _VSTD::bit_cast<int64_t>(__u);
+                __rx = (__rx < 0) ? (numeric_limits<int64_t>::min() - __rx - 1) : __rx;
+                __ry = (__ry < 0) ? (numeric_limits<int64_t>::min() - __ry - 1) : __ry;
+                return (__rx <=> __ry);
+            } else if (__t < __u) {
+                return strong_ordering::less;
+            } else if (__t > __u) {
+                return strong_ordering::greater;
+            } else if (__t == __u) {
+                if constexpr (numeric_limits<_Dp>::radix == 2) {
+                    return _VSTD::signbit(__u) <=> _VSTD::signbit(__t);
+                } else {
+                    // This is bullet 3 of the IEEE754 algorithm, relevant
+                    // only for decimal floating-point;
+                    // see https://stackoverflow.com/questions/69068075/
+                    if (__t == 0 || _VSTD::isinf(__t)) {
+                        return _VSTD::signbit(__u) <=> _VSTD::signbit(__t);
+                    } else {
+                        int __texp, __uexp;
+                        (void)_VSTD::frexp(__t, &__texp);
+                        (void)_VSTD::frexp(__u, &__uexp);
+                        return (__t < 0) ? (__texp <=> __uexp) : (__uexp <=> __texp);
+                    }
+                }
+            } else {
+                // They're unordered, so one of them must be a NAN.
+                // The order is -QNAN, -SNAN, numbers, +SNAN, +QNAN.
+                bool __t_is_nan = _VSTD::isnan(__t);
+                bool __u_is_nan = _VSTD::isnan(__u);
+                bool __t_is_negative = _VSTD::signbit(__t);
+                bool __u_is_negative = _VSTD::signbit(__u);
+                using _IntType = std::conditional_t<
+                    sizeof(__t) == sizeof(int32_t), int32_t, std::conditional_t<
+                    sizeof(__t) == sizeof(int64_t), int64_t, void>
+                >;
+                if constexpr (std::is_same_v<_IntType, void>) {
+                    static_assert(sizeof(_Dp) == 0, "std::strong_order is unimplemented for this floating-point type");
+                } else if (__t_is_nan && __u_is_nan) {
+                    // Order by sign bit, then by "payload bits" (we'll just use bit_cast).
+                    if (__t_is_negative != __u_is_negative) {
+                        return (__u_is_negative <=> __t_is_negative);
+                    } else {
+                        return _VSTD::bit_cast<_IntType>(__t) <=> _VSTD::bit_cast<_IntType>(__u);
+                    }
+                } else if (__t_is_nan) {
+                    return __t_is_negative ? strong_ordering::less : strong_ordering::greater;
+                } else {
+                    return __u_is_negative ? strong_ordering::greater : strong_ordering::less;
+                }
+            }
+        }
+
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<0>)
+            noexcept(noexcept(strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          strong_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+        _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+            noexcept(noexcept(__go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>())))
+            -> decltype(      __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()))
+            { return          __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<2>()); }
+    };
+} // namespace __strong_order
+
+inline namespace __cpo {
+    inline constexpr auto strong_order = __strong_order::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___COMPARE_STRONG_ORDER
diff --git a/include/__compare/weak_order.h b/include/__compare/weak_order.h
new file mode 100644
index 0000000..f67416e
--- /dev/null
+++ b/include/__compare/weak_order.h
@@ -0,0 +1,100 @@
+//===----------------------------------------------------------------------===//
+//
+// 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___COMPARE_WEAK_ORDER
+#define _LIBCPP___COMPARE_WEAK_ORDER
+
+#include <__compare/compare_three_way.h>
+#include <__compare/ordering.h>
+#include <__compare/strong_order.h>
+#include <__config>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+#include <cmath>
+#include <type_traits>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+// [cmp.alg]
+namespace __weak_order {
+    struct __fn {
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<3>)
+            noexcept(noexcept(weak_ordering(weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      weak_ordering(weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          weak_ordering(weak_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up, class _Dp = decay_t<_Tp>>
+            requires is_same_v<_Dp, decay_t<_Up>> && is_floating_point_v<_Dp>
+        _LIBCPP_HIDE_FROM_ABI static constexpr weak_ordering
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<2>) noexcept
+        {
+            std::partial_ordering __po = (__t <=> __u);
+            if (__po == std::partial_ordering::less) {
+                return std::weak_ordering::less;
+            } else if (__po == std::partial_ordering::equivalent) {
+                return std::weak_ordering::equivalent;
+            } else if (__po == std::partial_ordering::greater) {
+                return std::weak_ordering::greater;
+            } else {
+                // Otherwise, at least one of them is a NaN.
+                bool __t_is_nan = _VSTD::isnan(__t);
+                bool __u_is_nan = _VSTD::isnan(__u);
+                bool __t_is_negative = _VSTD::signbit(__t);
+                bool __u_is_negative = _VSTD::signbit(__u);
+                if (__t_is_nan && __u_is_nan) {
+                    return (__u_is_negative <=> __t_is_negative);
+                } else if (__t_is_nan) {
+                    return __t_is_negative ? weak_ordering::less : weak_ordering::greater;
+                } else {
+                    return __u_is_negative ? weak_ordering::greater : weak_ordering::less;
+                }
+            }
+        }
+
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<1>)
+            noexcept(noexcept(weak_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      weak_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          weak_ordering(compare_three_way()(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+            requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
+        _LIBCPP_HIDE_FROM_ABI static constexpr auto
+        __go(_Tp&& __t, _Up&& __u, __priority_tag<0>)
+            noexcept(noexcept(weak_ordering(_VSTD::strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u)))))
+            -> decltype(      weak_ordering(_VSTD::strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
+            { return          weak_ordering(_VSTD::strong_order(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))); }
+
+        template<class _Tp, class _Up>
+        _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+            noexcept(noexcept(__go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<3>())))
+            -> decltype(      __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<3>()))
+            { return          __go(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u), __priority_tag<3>()); }
+    };
+} // namespace __weak_order
+
+inline namespace __cpo {
+    inline constexpr auto weak_order = __weak_order::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_WEAK_ORDER
diff --git a/include/__utility/priority_tag.h b/include/__utility/priority_tag.h
new file mode 100644
index 0000000..45d9e5e
--- /dev/null
+++ b/include/__utility/priority_tag.h
@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_PRIORITY_TAG_H
+#define _LIBCPP___UTILITY_PRIORITY_TAG_H
+
+#include <__config>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template<size_t _Ip> struct __priority_tag : __priority_tag<_Ip - 1> {};
+template<> struct __priority_tag<0> {};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_PRIORITY_TAG_H
diff --git a/include/compare b/include/compare
index 8a2a829..5c4578d 100644
--- a/include/compare
+++ b/include/compare
@@ -140,25 +140,10 @@
 #include <__compare/compare_three_way_result.h>
 #include <__compare/is_eq.h>
 #include <__compare/ordering.h>
+#include <__compare/partial_order.h>
+#include <__compare/strong_order.h>
 #include <__compare/three_way_comparable.h>
+#include <__compare/weak_order.h>
 #include <__config>
 
-#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
-#pragma GCC system_header
-#endif
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-#if _LIBCPP_STD_VER > 17
-
-// [cmp.alg], comparison algorithms
-// TODO: unimplemented
-template<class _Tp> constexpr strong_ordering strong_order(const _Tp& __lhs, const _Tp& __rhs);
-template<class _Tp> constexpr weak_ordering weak_order(const _Tp& __lhs, const _Tp& __rhs);
-template<class _Tp> constexpr partial_ordering partial_order(const _Tp& __lhs, const _Tp& __rhs);
-
-#endif // _LIBCPP_STD_VER > 17
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif // _LIBCPP_COMPARE
diff --git a/include/module.modulemap b/include/module.modulemap
index 1775527..71acf7a 100644
--- a/include/module.modulemap
+++ b/include/module.modulemap
@@ -377,8 +377,11 @@
       module compare_three_way_result   { private header "__compare/compare_three_way_result.h"   }
       module is_eq                      { private header "__compare/is_eq.h"                      }
       module ordering                   { private header "__compare/ordering.h"                   }
+      module partial_order              { private header "__compare/partial_order.h"              }
+      module strong_order               { private header "__compare/strong_order.h"               }
       module synth_three_way            { private header "__compare/synth_three_way.h"            }
       module three_way_comparable       { private header "__compare/three_way_comparable.h"       }
+      module weak_order                 { private header "__compare/weak_order.h"                 }
     }
   }
   module complex {
@@ -883,6 +886,7 @@
       module move                { private header "__utility/move.h"                }
       module pair                { private header "__utility/pair.h"                }
       module piecewise_construct { private header "__utility/piecewise_construct.h" }
+      module priority_tag        { private header "__utility/priority_tag.h"        }
       module rel_ops             { private header "__utility/rel_ops.h"             }
       module swap                { private header "__utility/swap.h"                }
       module to_underlying       { private header "__utility/to_underlying.h"       }
diff --git a/include/utility b/include/utility
index 2b3c4df..4fa9028 100644
--- a/include/utility
+++ b/include/utility
@@ -227,6 +227,7 @@
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/piecewise_construct.h>
+#include <__utility/priority_tag.h>
 #include <__utility/rel_ops.h>
 #include <__utility/swap.h>
 #include <__utility/to_underlying.h>
diff --git a/test/libcxx/diagnostics/detail.headers/compare/partial_order.module.verify.cpp b/test/libcxx/diagnostics/detail.headers/compare/partial_order.module.verify.cpp
new file mode 100644
index 0000000..28b84a6
--- /dev/null
+++ b/test/libcxx/diagnostics/detail.headers/compare/partial_order.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__compare/partial_order.h'}}
+#include <__compare/partial_order.h>
diff --git a/test/libcxx/diagnostics/detail.headers/compare/strong_order.module.verify.cpp b/test/libcxx/diagnostics/detail.headers/compare/strong_order.module.verify.cpp
new file mode 100644
index 0000000..6514138
--- /dev/null
+++ b/test/libcxx/diagnostics/detail.headers/compare/strong_order.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__compare/strong_order.h'}}
+#include <__compare/strong_order.h>
diff --git a/test/libcxx/diagnostics/detail.headers/compare/weak_order.module.verify.cpp b/test/libcxx/diagnostics/detail.headers/compare/weak_order.module.verify.cpp
new file mode 100644
index 0000000..b488173
--- /dev/null
+++ b/test/libcxx/diagnostics/detail.headers/compare/weak_order.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__compare/weak_order.h'}}
+#include <__compare/weak_order.h>
diff --git a/test/libcxx/diagnostics/detail.headers/utility/priority_tag.module.verify.cpp b/test/libcxx/diagnostics/detail.headers/utility/priority_tag.module.verify.cpp
new file mode 100644
index 0000000..485fca0
--- /dev/null
+++ b/test/libcxx/diagnostics/detail.headers/utility/priority_tag.module.verify.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: modules-build
+
+// WARNING: This test was generated by 'generate_private_header_tests.py'
+// and should not be edited manually.
+
+// expected-error@*:* {{use of private header from outside its module: '__utility/priority_tag.h'}}
+#include <__utility/priority_tag.h>
diff --git a/test/std/language.support/cmp/cmp.alg/partial_order.pass.cpp b/test/std/language.support/cmp/cmp.alg/partial_order.pass.cpp
new file mode 100644
index 0000000..7ed1222
--- /dev/null
+++ b/test/std/language.support/cmp/cmp.alg/partial_order.pass.cpp
@@ -0,0 +1,255 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// <compare>
+
+// template<class T> constexpr partial_ordering partial_order(const T& a, const T& b);
+
+#include <compare>
+
+#include <cassert>
+#include <cmath>
+#include <iterator> // std::size
+#include <limits>
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+
+template<class T, class U>
+constexpr auto has_partial_order(T&& t, U&& u)
+    -> decltype(std::partial_order(static_cast<T&&>(t), static_cast<U&&>(u)), true)
+{
+    return true;
+}
+
+constexpr bool has_partial_order(...) {
+    return false;
+}
+
+namespace N11 {
+    struct A {};
+    struct B {};
+    std::strong_ordering partial_order(const A&, const A&) { return std::strong_ordering::less; }
+    std::strong_ordering partial_order(const A&, const B&);
+}
+
+void test_1_1()
+{
+    // If the decayed types of E and F differ, partial_order(E, F) is ill-formed.
+
+    static_assert( has_partial_order(1, 2));
+    static_assert(!has_partial_order(1, (short)2));
+    static_assert(!has_partial_order(1, 2.0));
+    static_assert(!has_partial_order(1.0f, 2.0));
+
+    static_assert( has_partial_order((int*)nullptr, (int*)nullptr));
+    static_assert(!has_partial_order((int*)nullptr, (const int*)nullptr));
+    static_assert(!has_partial_order((const int*)nullptr, (int*)nullptr));
+    static_assert( has_partial_order((const int*)nullptr, (const int*)nullptr));
+
+    N11::A a;
+    N11::B b;
+    static_assert( has_partial_order(a, a));
+    static_assert(!has_partial_order(a, b));
+}
+
+namespace N12 {
+    struct A {};
+    std::strong_ordering partial_order(A&, A&&) { return std::strong_ordering::less; }
+    std::weak_ordering partial_order(A&&, A&&) { return std::weak_ordering::equivalent; }
+    std::strong_ordering partial_order(const A&, const A&);
+
+    struct B {
+        friend int partial_order(B, B);
+    };
+
+    struct PartialOrder {
+        explicit operator std::partial_ordering() const { return std::partial_ordering::less; }
+    };
+    struct C {
+        bool touched = false;
+        friend PartialOrder partial_order(C& lhs, C&) { lhs.touched = true; return PartialOrder(); }
+    };
+}
+
+void test_1_2()
+{
+    // Otherwise, partial_ordering(partial_order(E, F))
+    // if it is a well-formed expression with overload resolution performed
+    // in a context that does not include a declaration of std::partial_order.
+
+    // Test that partial_order does not const-qualify the forwarded arguments.
+    N12::A a;
+    assert(std::partial_order(a, std::move(a)) == std::partial_ordering::less);
+    assert(std::partial_order(std::move(a), std::move(a)) == std::partial_ordering::equivalent);
+
+    // The type of partial_order(e,f) must be explicitly convertible to partial_ordering.
+    N12::B b;
+    static_assert(!has_partial_order(b, b));
+
+    N12::C c1, c2;
+    ASSERT_SAME_TYPE(decltype(std::partial_order(c1, c2)), std::partial_ordering);
+    assert(std::partial_order(c1, c2) == std::partial_ordering::less);
+    assert(c1.touched);
+    assert(!c2.touched);
+}
+
+namespace N13 {
+    // Compare to N12::A.
+    struct A {};
+    bool operator==(const A&, const A&);
+    constexpr std::partial_ordering operator<=>(A&, A&&) { return std::partial_ordering::less; }
+    constexpr std::partial_ordering operator<=>(A&&, A&&) { return std::partial_ordering::equivalent; }
+    std::partial_ordering operator<=>(const A&, const A&);
+    static_assert(std::three_way_comparable<A>);
+
+    struct B {
+        std::partial_ordering operator<=>(const B&) const;  // lacks operator==
+    };
+    static_assert(!std::three_way_comparable<B>);
+
+    struct C {
+        bool *touched;
+        bool operator==(const C&) const;
+        constexpr std::partial_ordering operator<=>(const C& rhs) const {
+            *rhs.touched = true;
+            return std::partial_ordering::equivalent;
+        }
+    };
+    static_assert(std::three_way_comparable<C>);
+}
+
+constexpr bool test_1_3()
+{
+    // Otherwise, partial_ordering(compare_three_way()(E, F)) if it is a well-formed expression.
+
+    // Test neither partial_order nor compare_three_way const-qualify the forwarded arguments.
+    N13::A a;
+    assert(std::partial_order(a, std::move(a)) == std::partial_ordering::less);
+    assert(std::partial_order(std::move(a), std::move(a)) == std::partial_ordering::equivalent);
+
+    N13::B b;
+    static_assert(!has_partial_order(b, b));
+
+    // Test that the arguments are passed to <=> in the correct order.
+    bool c1_touched = false;
+    bool c2_touched = false;
+    N13::C c1 = {&c1_touched};
+    N13::C c2 = {&c2_touched};
+    assert(std::partial_order(c1, c2) == std::partial_ordering::equivalent);
+    assert(!c1_touched);
+    assert(c2_touched);
+
+    // For partial_order, this bullet point takes care of floating-point types;
+    // they receive their natural partial order.
+    {
+        using F = float;
+        F nan = std::numeric_limits<F>::quiet_NaN();
+        assert(std::partial_order(F(1), F(2)) == std::partial_ordering::less);
+        assert(std::partial_order(F(0), -F(0)) == std::partial_ordering::equivalent);
+#ifndef TEST_COMPILER_GCC  // GCC can't compare NaN to non-NaN in a constant-expression
+        assert(std::partial_order(nan, F(1)) == std::partial_ordering::unordered);
+#endif
+        assert(std::partial_order(nan, nan) == std::partial_ordering::unordered);
+    }
+    {
+        using F = double;
+        F nan = std::numeric_limits<F>::quiet_NaN();
+        assert(std::partial_order(F(1), F(2)) == std::partial_ordering::less);
+        assert(std::partial_order(F(0), -F(0)) == std::partial_ordering::equivalent);
+#ifndef TEST_COMPILER_GCC
+        assert(std::partial_order(nan, F(1)) == std::partial_ordering::unordered);
+#endif
+        assert(std::partial_order(nan, nan) == std::partial_ordering::unordered);
+    }
+    {
+        using F = long double;
+        F nan = std::numeric_limits<F>::quiet_NaN();
+        assert(std::partial_order(F(1), F(2)) == std::partial_ordering::less);
+        assert(std::partial_order(F(0), -F(0)) == std::partial_ordering::equivalent);
+#ifndef TEST_COMPILER_GCC
+        assert(std::partial_order(nan, F(1)) == std::partial_ordering::unordered);
+#endif
+        assert(std::partial_order(nan, nan) == std::partial_ordering::unordered);
+    }
+
+    return true;
+}
+
+namespace N14 {
+    struct A {};
+    constexpr std::strong_ordering weak_order(A&, A&&) { return std::strong_ordering::less; }
+    constexpr std::strong_ordering weak_order(A&&, A&&) { return std::strong_ordering::equal; }
+    std::strong_ordering weak_order(const A&, const A&);
+
+    struct B {
+        friend std::partial_ordering weak_order(B, B);
+    };
+
+    struct StrongOrder {
+        operator std::strong_ordering() const { return std::strong_ordering::less; }
+    };
+    struct C {
+        friend StrongOrder weak_order(C& lhs, C&);
+    };
+
+    struct WeakOrder {
+        constexpr explicit operator std::weak_ordering() const { return std::weak_ordering::less; }
+        operator std::partial_ordering() const = delete;
+    };
+    struct D {
+        bool touched = false;
+        friend constexpr WeakOrder weak_order(D& lhs, D&) { lhs.touched = true; return WeakOrder(); }
+    };
+}
+
+constexpr bool test_1_4()
+{
+    // Otherwise, partial_ordering(weak_order(E, F)) [that is, std::weak_order]
+    // if it is a well-formed expression.
+
+    // Test that partial_order and weak_order do not const-qualify the forwarded arguments.
+    N14::A a;
+    assert(std::partial_order(a, std::move(a)) == std::partial_ordering::less);
+    assert(std::partial_order(std::move(a), std::move(a)) == std::partial_ordering::equivalent);
+
+    // The type of ADL weak_order(e,f) must be explicitly convertible to weak_ordering
+    // (not just to partial_ordering), or else std::weak_order(e,f) won't exist.
+    N14::B b;
+    static_assert(!has_partial_order(b, b));
+
+    // The type of ADL weak_order(e,f) must be explicitly convertible to weak_ordering
+    // (not just to strong_ordering), or else std::weak_order(e,f) won't exist.
+    N14::C c;
+    static_assert(!has_partial_order(c, c));
+
+    N14::D d1, d2;
+    ASSERT_SAME_TYPE(decltype(std::partial_order(d1, d2)), std::partial_ordering);
+    assert(std::partial_order(d1, d2) == std::partial_ordering::less);
+    assert(d1.touched);
+    assert(!d2.touched);
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test_1_1();
+    test_1_2();
+    test_1_3();
+    test_1_4();
+
+    static_assert(test_1_3());
+    static_assert(test_1_4());
+
+    return 0;
+}
diff --git a/test/std/language.support/cmp/cmp.alg/strong_order.pass.cpp b/test/std/language.support/cmp/cmp.alg/strong_order.pass.cpp
new file mode 100644
index 0000000..9845746
--- /dev/null
+++ b/test/std/language.support/cmp/cmp.alg/strong_order.pass.cpp
@@ -0,0 +1,467 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// <compare>
+
+// template<class T> constexpr strong_ordering strong_order(const T& a, const T& b);
+
+#include <compare>
+
+#include <cassert>
+#include <cmath>
+#include <iterator> // std::size
+#include <limits>
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+
+#if defined(__i386__)
+ #define TEST_BUGGY_SIGNALING_NAN
+#endif
+
+template<class T, class U>
+constexpr auto has_strong_order(T&& t, U&& u)
+    -> decltype(std::strong_order(static_cast<T&&>(t), static_cast<U&&>(u)), true)
+{
+    return true;
+}
+
+constexpr bool has_strong_order(...) {
+    return false;
+}
+
+namespace N11 {
+    struct A {};
+    struct B {};
+    std::strong_ordering strong_order(const A&, const A&) { return std::strong_ordering::less; }
+    std::strong_ordering strong_order(const A&, const B&);
+}
+
+void test_1_1()
+{
+    // If the decayed types of E and F differ, strong_order(E, F) is ill-formed.
+
+    static_assert( has_strong_order(1, 2));
+    static_assert(!has_strong_order(1, (short)2));
+    static_assert(!has_strong_order(1, 2.0));
+    static_assert(!has_strong_order(1.0f, 2.0));
+
+    static_assert( has_strong_order((int*)nullptr, (int*)nullptr));
+    static_assert(!has_strong_order((int*)nullptr, (const int*)nullptr));
+    static_assert(!has_strong_order((const int*)nullptr, (int*)nullptr));
+    static_assert( has_strong_order((const int*)nullptr, (const int*)nullptr));
+
+    N11::A a;
+    N11::B b;
+    static_assert( has_strong_order(a, a));
+    static_assert(!has_strong_order(a, b));
+}
+
+namespace N12 {
+    struct A {};
+    std::strong_ordering strong_order(A&, A&&) { return std::strong_ordering::less; }
+    std::strong_ordering strong_order(A&&, A&&) { return std::strong_ordering::equal; }
+    std::strong_ordering strong_order(const A&, const A&);
+
+    struct B {
+        friend std::weak_ordering strong_order(B&, B&);
+    };
+
+    struct StrongOrder {
+        explicit operator std::strong_ordering() const { return std::strong_ordering::less; }
+    };
+    struct C {
+        bool touched = false;
+        friend StrongOrder strong_order(C& lhs, C&) { lhs.touched = true; return StrongOrder(); }
+    };
+}
+
+void test_1_2()
+{
+    // Otherwise, strong_ordering(strong_order(E, F))
+    // if it is a well-formed expression with overload resolution performed
+    // in a context that does not include a declaration of std::strong_order.
+
+    // Test that strong_order does not const-qualify the forwarded arguments.
+    N12::A a;
+    assert(std::strong_order(a, std::move(a)) == std::strong_ordering::less);
+    assert(std::strong_order(std::move(a), std::move(a)) == std::strong_ordering::equal);
+
+    // The type of strong_order(e,f) must be explicitly convertible to strong_ordering.
+    N12::B b;
+    static_assert(!has_strong_order(b, b));
+
+    N12::C c1, c2;
+    ASSERT_SAME_TYPE(decltype(std::strong_order(c1, c2)), std::strong_ordering);
+    assert(std::strong_order(c1, c2) == std::strong_ordering::less);
+    assert(c1.touched);
+    assert(!c2.touched);
+}
+
+template<class F>
+constexpr bool test_1_3()
+{
+    // Otherwise, if the decayed type T of E is a floating-point type,
+    // yields a value of type strong_ordering that is consistent with
+    // the ordering observed by T's comparison operators,
+    // and if numeric_limits<T>::is_iec559 is true, is additionally consistent with
+    // the totalOrder operation as specified in ISO/IEC/IEEE 60559.
+
+    static_assert(std::numeric_limits<F>::is_iec559);
+
+    ASSERT_SAME_TYPE(decltype(std::strong_order(F(0), F(0))), std::strong_ordering);
+
+    F v[] = {
+        -std::numeric_limits<F>::infinity(),
+        std::numeric_limits<F>::lowest(),  // largest (finite) negative number
+        F(-1.0), F(-0.1),
+        -std::numeric_limits<F>::min(),    // smallest (normal) negative number
+        F(-0.0),                           // negative zero
+        F(0.0),
+        std::numeric_limits<F>::min(),     // smallest (normal) positive number
+        F(0.1), F(1.0), F(2.0), F(3.14),
+        std::numeric_limits<F>::max(),     // largest (finite) positive number
+        std::numeric_limits<F>::infinity(),
+    };
+
+    static_assert(std::size(v) == 14);
+
+    // Sanity-check that array 'v' is indeed in the right order.
+    for (int i=0; i < 14; ++i) {
+        for (int j=0; j < 14; ++j) {
+            auto naturalOrder = (v[i] <=> v[j]);
+            if (v[i] == 0 && v[j] == 0) {
+                assert(naturalOrder == std::partial_ordering::equivalent);
+            } else {
+                assert(naturalOrder == std::partial_ordering::unordered || naturalOrder == (i <=> j));
+            }
+        }
+    }
+
+    assert(std::strong_order(v[0], v[0]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[0], v[1]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[2]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[3]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[4]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[5]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[0], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[1], v[1]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[1], v[2]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[3]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[4]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[5]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[1], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[2], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[2], v[2]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[2], v[3]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[4]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[5]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[2], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[3], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[3], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[3], v[3]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[3], v[4]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[5]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[3], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[4], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[4], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[4], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[4], v[4]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[4], v[5]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[4], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[5], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[5], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[5], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[5], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[5], v[5]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[5], v[6]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[5], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[6], v[6]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[6], v[7]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[6], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[7], v[7]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[7], v[8]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[7], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[8], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[8], v[8]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[8], v[9]) == std::strong_ordering::less);
+    assert(std::strong_order(v[8], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[8], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[8], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[8], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[9], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[8]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[9], v[9]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[9], v[10]) == std::strong_ordering::less);
+    assert(std::strong_order(v[9], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[9], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[9], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[10], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[8]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[9]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[10], v[10]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[10], v[11]) == std::strong_ordering::less);
+    assert(std::strong_order(v[10], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[10], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[11], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[8]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[9]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[10]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[11], v[11]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[11], v[12]) == std::strong_ordering::less);
+    assert(std::strong_order(v[11], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[12], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[8]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[9]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[10]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[11]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[12], v[12]) == std::strong_ordering::equal);
+    assert(std::strong_order(v[12], v[13]) == std::strong_ordering::less);
+    assert(std::strong_order(v[13], v[0]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[1]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[2]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[3]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[4]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[5]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[6]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[7]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[8]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[9]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[10]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[11]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[12]) == std::strong_ordering::greater);
+    assert(std::strong_order(v[13], v[13]) == std::strong_ordering::equal);
+
+
+    // There's no way to produce a specifically positive or negative NAN
+    // at compile-time, so the NAN-related tests must be runtime-only.
+    // Also, x86-32 (x87 floating point) cannot handle signaling NANs;
+    // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57484 for context.
+
+    if (!std::is_constant_evaluated()) {
+        F nq = _VSTD::copysign(std::numeric_limits<F>::quiet_NaN(), F(-1));
+        F ns = _VSTD::copysign(std::numeric_limits<F>::signaling_NaN(), F(-1));
+        F ps = _VSTD::copysign(std::numeric_limits<F>::signaling_NaN(), F(+1));
+        F pq = _VSTD::copysign(std::numeric_limits<F>::quiet_NaN(), F(+1));
+
+        assert(std::strong_order(nq, nq) == std::strong_ordering::equal);
+#ifndef TEST_BUGGY_SIGNALING_NAN
+        assert(std::strong_order(nq, ns) == std::strong_ordering::less);
+#endif
+        for (int i=0; i < 14; ++i) {
+            assert(std::strong_order(nq, v[i]) == std::strong_ordering::less);
+        }
+        assert(std::strong_order(nq, ps) == std::strong_ordering::less);
+        assert(std::strong_order(nq, pq) == std::strong_ordering::less);
+
+#ifndef TEST_BUGGY_SIGNALING_NAN
+        assert(std::strong_order(ns, nq) == std::strong_ordering::greater);
+#endif
+        assert(std::strong_order(ns, ns) == std::strong_ordering::equal);
+        for (int i=0; i < 14; ++i) {
+            assert(std::strong_order(ns, v[i]) == std::strong_ordering::less);
+        }
+        assert(std::strong_order(ns, ps) == std::strong_ordering::less);
+        assert(std::strong_order(ns, pq) == std::strong_ordering::less);
+
+        assert(std::strong_order(ps, nq) == std::strong_ordering::greater);
+        assert(std::strong_order(ps, ns) == std::strong_ordering::greater);
+        for (int i=0; i < 14; ++i) {
+            assert(std::strong_order(ps, v[i]) == std::strong_ordering::greater);
+        }
+        assert(std::strong_order(ps, ps) == std::strong_ordering::equal);
+#ifndef TEST_BUGGY_SIGNALING_NAN
+        assert(std::strong_order(ps, pq) == std::strong_ordering::less);
+#endif
+
+        assert(std::strong_order(pq, nq) == std::strong_ordering::greater);
+        assert(std::strong_order(pq, ns) == std::strong_ordering::greater);
+        for (int i=0; i < 14; ++i) {
+            assert(std::strong_order(pq, v[i]) == std::strong_ordering::greater);
+        }
+#ifndef TEST_BUGGY_SIGNALING_NAN
+        assert(std::strong_order(pq, ps) == std::strong_ordering::greater);
+#endif
+        assert(std::strong_order(pq, pq) == std::strong_ordering::equal);
+    }
+
+    return true;
+}
+
+namespace N14 {
+    // Compare to N12::A.
+    struct A {};
+    bool operator==(const A&, const A&);
+    constexpr std::strong_ordering operator<=>(A&, A&&) { return std::strong_ordering::less; }
+    constexpr std::strong_ordering operator<=>(A&&, A&&) { return std::strong_ordering::equal; }
+    std::strong_ordering operator<=>(const A&, const A&);
+    static_assert(std::three_way_comparable<A>);
+
+    struct B {
+        std::strong_ordering operator<=>(const B&) const;  // lacks operator==
+    };
+    static_assert(!std::three_way_comparable<B>);
+
+    struct C {
+        bool *touched;
+        bool operator==(const C&) const;
+        constexpr std::strong_ordering operator<=>(const C& rhs) const {
+            *rhs.touched = true;
+            return std::strong_ordering::equal;
+        }
+    };
+    static_assert(std::three_way_comparable<C>);
+}
+
+constexpr bool test_1_4()
+{
+    // Otherwise, strong_ordering(compare_three_way()(E, F)) if it is a well-formed expression.
+
+    // Test neither strong_order nor compare_three_way const-qualify the forwarded arguments.
+    N14::A a;
+    assert(std::strong_order(a, std::move(a)) == std::strong_ordering::less);
+    assert(std::strong_order(std::move(a), std::move(a)) == std::strong_ordering::equal);
+
+    N14::B b;
+    static_assert(!has_strong_order(b, b));
+
+    // Test that the arguments are passed to <=> in the correct order.
+    bool c1_touched = false;
+    bool c2_touched = false;
+    N14::C c1 = {&c1_touched};
+    N14::C c2 = {&c2_touched};
+    assert(std::strong_order(c1, c2) == std::strong_ordering::equal);
+    assert(!c1_touched);
+    assert(c2_touched);
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test_1_1();
+    test_1_2();
+    test_1_3<float>();
+    test_1_3<double>();
+    // test_1_3<long double>();  // UNIMPLEMENTED
+    test_1_4();
+
+    static_assert(test_1_3<float>());
+    static_assert(test_1_3<double>());
+    // static_assert(test_1_3<long double>());  // UNIMPLEMENTED
+    static_assert(test_1_4());
+
+    return 0;
+}
diff --git a/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp b/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp
new file mode 100644
index 0000000..74ecac6
--- /dev/null
+++ b/test/std/language.support/cmp/cmp.alg/strong_order_long_double.verify.cpp
@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// The following platforms have sizeof(long double) == sizeof(double), so this test doesn't apply to them.
+// UNSUPPORTED: target={{arm64|armv8|armv7|powerpc|powerpc64}}-{{.+}}
+// UNSUPPORTED: target=x86_64-pc-windows-{{.+}}
+
+// <compare>
+
+// template<class T> constexpr strong_ordering strong_order(const T& a, const T& b);
+
+// libc++ does not support strong_order(long double, long double) quite yet.
+// This test verifies the error message we give for that case.
+// TODO: remove this test once long double is properly supported.
+
+#include <compare>
+
+#include "test_macros.h"
+
+void f() {
+    long double ld = 3.14;
+    (void)std::strong_order(ld, ld);  // expected-error@*:* {{std::strong_order is unimplemented for this floating-point type}}
+}
diff --git a/test/std/language.support/cmp/cmp.alg/weak_order.pass.cpp b/test/std/language.support/cmp/cmp.alg/weak_order.pass.cpp
new file mode 100644
index 0000000..64f257d
--- /dev/null
+++ b/test/std/language.support/cmp/cmp.alg/weak_order.pass.cpp
@@ -0,0 +1,514 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+// UNSUPPORTED: libcpp-no-concepts
+
+// <compare>
+
+// template<class T> constexpr weak_ordering weak_order(const T& a, const T& b);
+
+#include <compare>
+
+#include <cassert>
+#include <cmath>
+#include <iterator> // std::size
+#include <limits>
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+
+template<class T, class U>
+constexpr auto has_weak_order(T&& t, U&& u)
+    -> decltype(std::weak_order(static_cast<T&&>(t), static_cast<U&&>(u)), true)
+{
+    return true;
+}
+
+constexpr bool has_weak_order(...) {
+    return false;
+}
+
+namespace N11 {
+    struct A {};
+    struct B {};
+    std::strong_ordering weak_order(const A&, const A&) { return std::strong_ordering::less; }
+    std::strong_ordering weak_order(const A&, const B&);
+}
+
+void test_1_1()
+{
+    // If the decayed types of E and F differ, weak_order(E, F) is ill-formed.
+
+    static_assert( has_weak_order(1, 2));
+    static_assert(!has_weak_order(1, (short)2));
+    static_assert(!has_weak_order(1, 2.0));
+    static_assert(!has_weak_order(1.0f, 2.0));
+
+    static_assert( has_weak_order((int*)nullptr, (int*)nullptr));
+    static_assert(!has_weak_order((int*)nullptr, (const int*)nullptr));
+    static_assert(!has_weak_order((const int*)nullptr, (int*)nullptr));
+    static_assert( has_weak_order((const int*)nullptr, (const int*)nullptr));
+
+    N11::A a;
+    N11::B b;
+    static_assert( has_weak_order(a, a));
+    static_assert(!has_weak_order(a, b));
+}
+
+namespace N12 {
+    struct A {};
+    std::strong_ordering weak_order(A&, A&&) { return std::strong_ordering::less; }
+    std::strong_ordering weak_order(A&&, A&&) { return std::strong_ordering::equal; }
+    std::strong_ordering weak_order(const A&, const A&);
+
+    struct B {
+        friend std::partial_ordering weak_order(B&, B&);
+    };
+
+    struct WeakOrder {
+        explicit operator std::weak_ordering() const { return std::weak_ordering::less; }
+    };
+    struct C {
+        bool touched = false;
+        friend WeakOrder weak_order(C& lhs, C&) { lhs.touched = true; return WeakOrder(); }
+    };
+}
+
+void test_1_2()
+{
+    // Otherwise, weak_ordering(weak_order(E, F))
+    // if it is a well-formed expression with overload resolution performed
+    // in a context that does not include a declaration of std::weak_order.
+
+    // Test that weak_order does not const-qualify the forwarded arguments.
+    N12::A a;
+    assert(std::weak_order(a, std::move(a)) == std::weak_ordering::less);
+    assert(std::weak_order(std::move(a), std::move(a)) == std::weak_ordering::equivalent);
+
+    // The type of weak_order(e,f) must be explicitly convertible to weak_ordering.
+    N12::B b;
+    static_assert(!has_weak_order(b, b));
+
+    N12::C c1, c2;
+    ASSERT_SAME_TYPE(decltype(std::weak_order(c1, c2)), std::weak_ordering);
+    assert(std::weak_order(c1, c2) == std::weak_ordering::less);
+    assert(c1.touched);
+    assert(!c2.touched);
+}
+
+template<class F>
+constexpr bool test_1_3()
+{
+    // Otherwise, if the decayed type T of E is a floating-point type,
+    // yields a value of type weak_ordering that is consistent with
+    // the ordering observed by T's comparison operators and strong_order,
+    // and if numeric_limits<T>::is_iec559 is true, is additionally consistent with
+    // the following equivalence classes...
+
+    // std::numeric_limits<F>::is_iec559 is usually true.
+    // It is false for F=long double on AIX; but this test is still expected
+    // to pass (e.g. std::weak_order(+0, -0) == weak_ordering::equivalent,
+    // even on AIX).
+
+    ASSERT_SAME_TYPE(decltype(std::weak_order(F(0), F(0))), std::weak_ordering);
+
+    F v[] = {
+        -std::numeric_limits<F>::infinity(),
+        std::numeric_limits<F>::lowest(),  // largest (finite) negative number
+        F(-1.0), F(-0.1),
+        -std::numeric_limits<F>::min(),    // smallest (normal) negative number
+        F(-0.0),                           // negative zero
+        F(0.0),
+        std::numeric_limits<F>::min(),     // smallest (normal) positive number
+        F(0.1), F(1.0), F(2.0), F(3.14),
+        std::numeric_limits<F>::max(),     // largest (finite) positive number
+        std::numeric_limits<F>::infinity(),
+    };
+
+    static_assert(std::size(v) == 14);
+
+    // Sanity-check that array 'v' is indeed in the right order.
+    for (int i=0; i < 14; ++i) {
+        for (int j=0; j < 14; ++j) {
+            auto naturalOrder = (v[i] <=> v[j]);
+            if (v[i] == 0 && v[j] == 0) {
+                assert(naturalOrder == std::partial_ordering::equivalent);
+            } else {
+                assert(naturalOrder == std::partial_ordering::unordered || naturalOrder == (i <=> j));
+            }
+        }
+    }
+
+    assert(std::weak_order(v[0], v[0]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[0], v[1]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[2]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[3]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[4]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[5]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[6]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[0], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[1], v[1]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[1], v[2]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[3]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[4]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[5]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[6]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[1], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[2], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[2], v[2]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[2], v[3]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[4]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[5]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[6]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[2], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[3], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[3], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[3], v[3]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[3], v[4]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[5]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[6]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[3], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[4], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[4], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[4], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[4], v[4]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[4], v[5]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[6]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[4], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[5], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[5], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[5], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[5], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[5], v[5]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[5], v[6]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[5], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[5], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[6], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[6], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[6], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[6], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[6], v[5]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[6], v[6]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[6], v[7]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[6], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[7], v[7]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[7], v[8]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[7], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[8], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[8], v[8]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[8], v[9]) == std::weak_ordering::less);
+    assert(std::weak_order(v[8], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[8], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[8], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[8], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[9], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[8]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[9], v[9]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[9], v[10]) == std::weak_ordering::less);
+    assert(std::weak_order(v[9], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[9], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[9], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[10], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[8]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[9]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[10], v[10]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[10], v[11]) == std::weak_ordering::less);
+    assert(std::weak_order(v[10], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[10], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[11], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[8]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[9]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[10]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[11], v[11]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[11], v[12]) == std::weak_ordering::less);
+    assert(std::weak_order(v[11], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[12], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[8]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[9]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[10]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[11]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[12], v[12]) == std::weak_ordering::equivalent);
+    assert(std::weak_order(v[12], v[13]) == std::weak_ordering::less);
+    assert(std::weak_order(v[13], v[0]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[1]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[2]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[3]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[4]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[5]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[6]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[7]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[8]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[9]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[10]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[11]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[12]) == std::weak_ordering::greater);
+    assert(std::weak_order(v[13], v[13]) == std::weak_ordering::equivalent);
+
+
+    // There's no way to produce a specifically positive or negative NAN
+    // at compile-time, so the NAN-related tests must be runtime-only.
+
+    if (!std::is_constant_evaluated()) {
+        F nq = _VSTD::copysign(std::numeric_limits<F>::quiet_NaN(), F(-1));
+        F ns = _VSTD::copysign(std::numeric_limits<F>::signaling_NaN(), F(-1));
+        F ps = _VSTD::copysign(std::numeric_limits<F>::signaling_NaN(), F(+1));
+        F pq = _VSTD::copysign(std::numeric_limits<F>::quiet_NaN(), F(+1));
+
+        assert(std::weak_order(nq, nq) == std::weak_ordering::equivalent);
+        assert(std::weak_order(nq, ns) == std::weak_ordering::equivalent);
+        for (int i=0; i < 14; ++i) {
+            assert(std::weak_order(nq, v[i]) == std::weak_ordering::less);
+        }
+        assert(std::weak_order(nq, ps) == std::weak_ordering::less);
+        assert(std::weak_order(nq, pq) == std::weak_ordering::less);
+
+        assert(std::weak_order(ns, nq) == std::weak_ordering::equivalent);
+        assert(std::weak_order(ns, ns) == std::weak_ordering::equivalent);
+        for (int i=0; i < 14; ++i) {
+            assert(std::weak_order(ns, v[i]) == std::weak_ordering::less);
+        }
+        assert(std::weak_order(ns, ps) == std::weak_ordering::less);
+        assert(std::weak_order(ns, pq) == std::weak_ordering::less);
+
+        assert(std::weak_order(ps, nq) == std::weak_ordering::greater);
+        assert(std::weak_order(ps, ns) == std::weak_ordering::greater);
+        for (int i=0; i < 14; ++i) {
+            assert(std::weak_order(ps, v[i]) == std::weak_ordering::greater);
+        }
+        assert(std::weak_order(ps, ps) == std::weak_ordering::equivalent);
+        assert(std::weak_order(ps, pq) == std::weak_ordering::equivalent);
+
+        assert(std::weak_order(pq, nq) == std::weak_ordering::greater);
+        assert(std::weak_order(pq, ns) == std::weak_ordering::greater);
+        for (int i=0; i < 14; ++i) {
+            assert(std::weak_order(pq, v[i]) == std::weak_ordering::greater);
+        }
+        assert(std::weak_order(pq, ps) == std::weak_ordering::equivalent);
+        assert(std::weak_order(pq, pq) == std::weak_ordering::equivalent);
+    }
+
+    return true;
+}
+
+namespace N14 {
+    // Compare to N12::A.
+    struct A {};
+    bool operator==(const A&, const A&);
+    constexpr std::weak_ordering operator<=>(A&, A&&) { return std::weak_ordering::less; }
+    constexpr std::weak_ordering operator<=>(A&&, A&&) { return std::weak_ordering::equivalent; }
+    std::weak_ordering operator<=>(const A&, const A&);
+    static_assert(std::three_way_comparable<A>);
+
+    struct B {
+        std::weak_ordering operator<=>(const B&) const;  // lacks operator==
+    };
+    static_assert(!std::three_way_comparable<B>);
+
+    struct C {
+        bool *touched;
+        bool operator==(const C&) const;
+        constexpr std::weak_ordering operator<=>(const C& rhs) const {
+            *rhs.touched = true;
+            return std::weak_ordering::equivalent;
+        }
+    };
+    static_assert(std::three_way_comparable<C>);
+}
+
+constexpr bool test_1_4()
+{
+    // Otherwise, weak_ordering(compare_three_way()(E, F)) if it is a well-formed expression.
+
+    // Test neither weak_order nor compare_three_way const-qualify the forwarded arguments.
+    N14::A a;
+    assert(std::weak_order(a, std::move(a)) == std::weak_ordering::less);
+    assert(std::weak_order(std::move(a), std::move(a)) == std::weak_ordering::equivalent);
+
+    N14::B b;
+    static_assert(!has_weak_order(b, b));
+
+    // Test that the arguments are passed to <=> in the correct order.
+    bool c1_touched = false;
+    bool c2_touched = false;
+    N14::C c1 = {&c1_touched};
+    N14::C c2 = {&c2_touched};
+    assert(std::weak_order(c1, c2) == std::weak_ordering::equivalent);
+    assert(!c1_touched);
+    assert(c2_touched);
+
+    return true;
+}
+
+namespace N15 {
+    struct A {};
+    constexpr std::strong_ordering strong_order(A&, A&&) { return std::strong_ordering::less; }
+    constexpr std::strong_ordering strong_order(A&&, A&&) { return std::strong_ordering::equal; }
+    std::strong_ordering strong_order(const A&, const A&);
+
+    struct B {
+        friend std::weak_ordering strong_order(B&, B&);
+    };
+
+    struct WeakOrder {
+        operator std::weak_ordering() const { return std::weak_ordering::less; }
+    };
+    struct C {
+        friend WeakOrder strong_order(C& lhs, C&);
+    };
+
+    struct StrongOrder {
+        constexpr explicit operator std::strong_ordering() const { return std::strong_ordering::less; }
+        operator std::weak_ordering() const = delete;
+    };
+    struct D {
+        bool touched = false;
+        friend constexpr StrongOrder strong_order(D& lhs, D&) { lhs.touched = true; return StrongOrder(); }
+    };
+}
+
+constexpr bool test_1_5()
+{
+    // Otherwise, weak_ordering(strong_order(E, F)) [that is, std::strong_order]
+    // if it is a well-formed expression.
+
+    // Test that weak_order and strong_order do not const-qualify the forwarded arguments.
+    N15::A a;
+    assert(std::weak_order(a, std::move(a)) == std::weak_ordering::less);
+    assert(std::weak_order(std::move(a), std::move(a)) == std::weak_ordering::equivalent);
+
+    // The type of ADL strong_order(e,f) must be explicitly convertible to strong_ordering
+    // (not just to weak_ordering), or else std::strong_order(e,f) won't exist.
+    N15::B b;
+    static_assert(!has_weak_order(b, b));
+
+    // The type of ADL strong_order(e,f) must be explicitly convertible to strong_ordering
+    // (not just to weak_ordering), or else std::strong_order(e,f) won't exist.
+    N15::C c;
+    static_assert(!has_weak_order(c, c));
+
+    N15::D d1, d2;
+    ASSERT_SAME_TYPE(decltype(std::weak_order(d1, d2)), std::weak_ordering);
+    assert(std::weak_order(d1, d2) == std::weak_ordering::less);
+    assert(d1.touched);
+    assert(!d2.touched);
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test_1_1();
+    test_1_2();
+    test_1_3<float>();
+    test_1_3<double>();
+    test_1_3<long double>();
+    test_1_4();
+    test_1_5();
+
+    static_assert(test_1_3<float>());
+    static_assert(test_1_3<double>());
+    static_assert(test_1_3<long double>());
+    static_assert(test_1_4());
+    static_assert(test_1_5());
+
+    return 0;
+}