lib: establish Zircon libc++ and KTL foundation

13 files changed, 1123 insertions, 0 deletions

diff --git a/third_party/libcxx/include/c++/v1/__compare/common_comparison_category.h b/third_party/libcxx/include/c++/v1/__compare/common_comparison_category.h
new file mode 100644
index 0000000..eae2ef0
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/common_comparison_category.h
@@ -0,0 +1,86 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COMMON_COMPARISON_CATEGORY_H
+#define _LIBCPP___COMPARE_COMMON_COMPARISON_CATEGORY_H
+
+#include <__compare/ordering.h>
+#include <__config>
+#include <__cstddef/size_t.h>
+#include <__type_traits/is_same.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+namespace __comp_detail {
+
+enum _ClassifyCompCategory : unsigned { _None, _PartialOrd, _WeakOrd, _StrongOrd, _CCC_Size };
+
+template <class _Tp>
+_LIBCPP_HIDE_FROM_ABI constexpr _ClassifyCompCategory __type_to_enum() noexcept {
+  if (is_same_v<_Tp, partial_ordering>)
+    return _PartialOrd;
+  if (is_same_v<_Tp, weak_ordering>)
+    return _WeakOrd;
+  if (is_same_v<_Tp, strong_ordering>)
+    return _StrongOrd;
+  return _None;
+}
+
+template <size_t _Size>
+_LIBCPP_HIDE_FROM_ABI constexpr _ClassifyCompCategory
+__compute_comp_type(const _ClassifyCompCategory (&__types)[_Size]) {
+  int __seen[_CCC_Size] = {};
+  for (auto __type : __types)
+    ++__seen[__type];
+  if (__seen[_None])
+    return _None;
+  if (__seen[_PartialOrd])
+    return _PartialOrd;
+  if (__seen[_WeakOrd])
+    return _WeakOrd;
+  return _StrongOrd;
+}
+
+template <class... _Ts, bool _False = false>
+_LIBCPP_HIDE_FROM_ABI constexpr auto __get_comp_type() {
+  using _CCC                    = _ClassifyCompCategory;
+  constexpr _CCC __type_kinds[] = {_StrongOrd, __comp_detail::__type_to_enum<_Ts>()...};
+  constexpr _CCC __cat          = __comp_detail::__compute_comp_type(__type_kinds);
+  if constexpr (__cat == _None)
+    return void();
+  else if constexpr (__cat == _PartialOrd)
+    return partial_ordering::equivalent;
+  else if constexpr (__cat == _WeakOrd)
+    return weak_ordering::equivalent;
+  else if constexpr (__cat == _StrongOrd)
+    return strong_ordering::equivalent;
+  else
+    static_assert(_False, "unhandled case");
+}
+} // namespace __comp_detail
+
+// [cmp.common], common comparison category type
+template <class... _Ts>
+struct common_comparison_category {
+  using type _LIBCPP_NODEBUG = decltype(__comp_detail::__get_comp_type<_Ts...>());
+};
+
+template <class... _Ts>
+using common_comparison_category_t = typename common_comparison_category<_Ts...>::type;
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMMON_COMPARISON_CATEGORY_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/compare_partial_order_fallback.h b/third_party/libcxx/include/c++/v1/__compare/compare_partial_order_fallback.h
new file mode 100644
index 0000000..80f2aca
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/compare_partial_order_fallback.h
@@ -0,0 +1,75 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COMPARE_PARTIAL_ORDER_FALLBACK
+#define _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
+
+#include <__compare/ordering.h>
+#include <__compare/partial_order.h>
+#include <__concepts/boolean_testable.h>
+#include <__config>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [cmp.alg]
+namespace __compare_partial_order_fallback {
+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<1>) noexcept(
+      noexcept(std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
+      -> decltype(std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
+    return std::partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
+  }
+
+  template <class _Tp, class _Up>
+    requires is_same_v<decay_t<_Tp>, decay_t<_Up>> && requires(_Tp&& __t, _Up&& __u) {
+      { std::forward<_Tp>(__t) == std::forward<_Up>(__u) } -> __boolean_testable;
+      { std::forward<_Tp>(__t) < std::forward<_Up>(__u) } -> __boolean_testable;
+      { std::forward<_Up>(__u) < std::forward<_Tp>(__t) } -> __boolean_testable;
+    }
+  _LIBCPP_HIDE_FROM_ABI static constexpr partial_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(
+      noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)  ? partial_ordering::equivalent
+               : std::forward<_Tp>(__t) < std::forward<_Up>(__u) ? partial_ordering::less
+               : std::forward<_Up>(__u) < std::forward<_Tp>(__t) ? partial_ordering::greater
+                                                                 : partial_ordering::unordered)) {
+    return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? partial_ordering::equivalent
+         : std::forward<_Tp>(__t) < std::forward<_Up>(__u)  ? partial_ordering::less
+         : std::forward<_Up>(__u) < std::forward<_Tp>(__t)
+             ? partial_ordering::greater
+             : partial_ordering::unordered;
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
+    return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
+  }
+};
+} // namespace __compare_partial_order_fallback
+
+inline namespace __cpo {
+inline constexpr auto compare_partial_order_fallback = __compare_partial_order_fallback::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMPARE_PARTIAL_ORDER_FALLBACK
diff --git a/third_party/libcxx/include/c++/v1/__compare/compare_strong_order_fallback.h b/third_party/libcxx/include/c++/v1/__compare/compare_strong_order_fallback.h
new file mode 100644
index 0000000..c41a90c
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/compare_strong_order_fallback.h
@@ -0,0 +1,72 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COMPARE_STRONG_ORDER_FALLBACK
+#define _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
+
+#include <__compare/ordering.h>
+#include <__compare/strong_order.h>
+#include <__concepts/boolean_testable.h>
+#include <__config>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [cmp.alg]
+namespace __compare_strong_order_fallback {
+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<1>) noexcept(
+      noexcept(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
+      -> decltype(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
+    return std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
+  }
+
+  template <class _Tp, class _Up>
+    requires is_same_v<decay_t<_Tp>, decay_t<_Up>> && requires(_Tp&& __t, _Up&& __u) {
+      { std::forward<_Tp>(__t) == std::forward<_Up>(__u) } -> __boolean_testable;
+      { std::forward<_Tp>(__t) < std::forward<_Up>(__u) } -> __boolean_testable;
+    }
+  _LIBCPP_HIDE_FROM_ABI static constexpr strong_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(
+      noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u)  ? strong_ordering::equal
+               : std::forward<_Tp>(__t) < std::forward<_Up>(__u) ? strong_ordering::less
+                                                                 : strong_ordering::greater)) {
+    return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
+         : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
+             ? strong_ordering::less
+             : strong_ordering::greater;
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
+    return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
+  }
+};
+} // namespace __compare_strong_order_fallback
+
+inline namespace __cpo {
+inline constexpr auto compare_strong_order_fallback = __compare_strong_order_fallback::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
diff --git a/third_party/libcxx/include/c++/v1/__compare/compare_three_way.h b/third_party/libcxx/include/c++/v1/__compare/compare_three_way.h
new file mode 100644
index 0000000..852c587
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/compare_three_way.h
@@ -0,0 +1,40 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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_COMPARE_THREE_WAY_H
+#define _LIBCPP___COMPARE_COMPARE_THREE_WAY_H
+
+#include <__compare/three_way_comparable.h>
+#include <__config>
+#include <__utility/forward.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+struct compare_three_way {
+  template <class _T1, class _T2>
+    requires three_way_comparable_with<_T1, _T2>
+  constexpr _LIBCPP_HIDE_FROM_ABI auto operator()(_T1&& __t, _T2&& __u) const
+      noexcept(noexcept(std::forward<_T1>(__t) <=> std::forward<_T2>(__u))) {
+    return std::forward<_T1>(__t) <=> std::forward<_T2>(__u);
+  }
+
+  using is_transparent = void;
+};
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/compare_three_way_result.h b/third_party/libcxx/include/c++/v1/__compare/compare_three_way_result.h
new file mode 100644
index 0000000..264a4d6
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/compare_three_way_result.h
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COMPARE_THREE_WAY_RESULT_H
+#define _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
+
+#include <__config>
+#include <__type_traits/make_const_lvalue_ref.h>
+#include <__utility/declval.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+template <class, class, class>
+struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result {};
+
+template <class _Tp, class _Up>
+struct _LIBCPP_HIDE_FROM_ABI __compare_three_way_result<
+    _Tp,
+    _Up,
+    decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>(), void())> {
+  using type _LIBCPP_NODEBUG =
+      decltype(std::declval<__make_const_lvalue_ref<_Tp>>() <=> std::declval<__make_const_lvalue_ref<_Up>>());
+};
+
+template <class _Tp, class _Up = _Tp>
+struct _LIBCPP_NO_SPECIALIZATIONS compare_three_way_result : __compare_three_way_result<_Tp, _Up, void> {};
+
+template <class _Tp, class _Up = _Tp>
+using compare_three_way_result_t = typename compare_three_way_result<_Tp, _Up>::type;
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMPARE_THREE_WAY_RESULT_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/compare_weak_order_fallback.h b/third_party/libcxx/include/c++/v1/__compare/compare_weak_order_fallback.h
new file mode 100644
index 0000000..26689fb
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/compare_weak_order_fallback.h
@@ -0,0 +1,73 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_COMPARE_WEAK_ORDER_FALLBACK
+#define _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK
+
+#include <__compare/ordering.h>
+#include <__compare/weak_order.h>
+#include <__concepts/boolean_testable.h>
+#include <__config>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [cmp.alg]
+namespace __compare_weak_order_fallback {
+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<1>) noexcept(
+      noexcept(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
+      -> decltype(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
+    return std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
+  }
+
+  template <class _Tp, class _Up>
+    requires is_same_v<decay_t<_Tp>, decay_t<_Up>> && requires(_Tp&& __t, _Up&& __u) {
+      { std::forward<_Tp>(__t) == std::forward<_Up>(__u) } -> __boolean_testable;
+      { std::forward<_Tp>(__t) < std::forward<_Up>(__u) } -> __boolean_testable;
+    }
+  _LIBCPP_HIDE_FROM_ABI static constexpr weak_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(noexcept(
+      std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? weak_ordering::equivalent
+      : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
+          ? weak_ordering::less
+          : weak_ordering::greater)) {
+    return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? weak_ordering::equivalent
+         : std::forward<_Tp>(__t) < std::forward<_Up>(__u)
+             ? weak_ordering::less
+             : weak_ordering::greater;
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
+    return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
+  }
+};
+} // namespace __compare_weak_order_fallback
+
+inline namespace __cpo {
+inline constexpr auto compare_weak_order_fallback = __compare_weak_order_fallback::__fn{};
+} // namespace __cpo
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_COMPARE_WEAK_ORDER_FALLBACK
diff --git a/third_party/libcxx/include/c++/v1/__compare/is_eq.h b/third_party/libcxx/include/c++/v1/__compare/is_eq.h
new file mode 100644
index 0000000..ee4d11b
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/is_eq.h
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_IS_EQ_H
+#define _LIBCPP___COMPARE_IS_EQ_H
+
+#include <__compare/ordering.h>
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_eq(partial_ordering __c) noexcept { return __c == 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_neq(partial_ordering __c) noexcept { return __c != 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lt(partial_ordering __c) noexcept { return __c < 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_lteq(partial_ordering __c) noexcept { return __c <= 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gt(partial_ordering __c) noexcept { return __c > 0; }
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline constexpr bool is_gteq(partial_ordering __c) noexcept { return __c >= 0; }
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_IS_EQ_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/ordering.h b/third_party/libcxx/include/c++/v1/__compare/ordering.h
new file mode 100644
index 0000000..902ef53
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/ordering.h
@@ -0,0 +1,282 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_ORDERING_H
+#define _LIBCPP___COMPARE_ORDERING_H
+
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_same.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// exposition only
+enum class _OrdResult : signed char { __less = -1, __equiv = 0, __greater = 1 };
+
+enum class _PartialOrdResult : signed char {
+  __less      = static_cast<signed char>(_OrdResult::__less),
+  __equiv     = static_cast<signed char>(_OrdResult::__equiv),
+  __greater   = static_cast<signed char>(_OrdResult::__greater),
+  __unordered = -127,
+};
+
+class partial_ordering;
+class weak_ordering;
+class strong_ordering;
+
+struct _CmpUnspecifiedParam {
+  // If anything other than a literal 0 is provided, the behavior is undefined by the Standard.
+  //
+  // The alternative to the `__enable_if__` attribute would be to use the fact that a pointer
+  // can be constructed from literal 0, but this conflicts with `-Wzero-as-null-pointer-constant`.
+  template <class _Tp, class = __enable_if_t<is_same_v<_Tp, int> > >
+  _LIBCPP_HIDE_FROM_ABI consteval _CmpUnspecifiedParam(_Tp __zero) noexcept
+#  if __has_attribute(__enable_if__)
+      __attribute__((__enable_if__(
+          __zero == 0, "Only literal 0 is allowed as the operand of a comparison with one of the ordering types")))
+#  endif
+  {
+    (void)__zero;
+  }
+};
+
+class partial_ordering {
+  _LIBCPP_HIDE_FROM_ABI explicit constexpr partial_ordering(_PartialOrdResult __v) noexcept : __value_(__v) {}
+
+public:
+  // valid values
+  static const partial_ordering less;
+  static const partial_ordering equivalent;
+  static const partial_ordering greater;
+  static const partial_ordering unordered;
+
+  // comparisons
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(partial_ordering, partial_ordering) noexcept = default;
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == _PartialOrdResult::__equiv;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == _PartialOrdResult::__less;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == _PartialOrdResult::__equiv || __v.__value_ == _PartialOrdResult::__less;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == _PartialOrdResult::__greater;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == _PartialOrdResult::__equiv || __v.__value_ == _PartialOrdResult::__greater;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(_CmpUnspecifiedParam, partial_ordering __v) noexcept {
+    return __v.__value_ == _PartialOrdResult::__greater;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(_CmpUnspecifiedParam, partial_ordering __v) noexcept {
+    return __v.__value_ == _PartialOrdResult::__equiv || __v.__value_ == _PartialOrdResult::__greater;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(_CmpUnspecifiedParam, partial_ordering __v) noexcept {
+    return __v.__value_ == _PartialOrdResult::__less;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(_CmpUnspecifiedParam, partial_ordering __v) noexcept {
+    return __v.__value_ == _PartialOrdResult::__equiv || __v.__value_ == _PartialOrdResult::__less;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr partial_ordering
+  operator<=>(partial_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr partial_ordering
+  operator<=>(_CmpUnspecifiedParam, partial_ordering __v) noexcept {
+    return __v < 0 ? partial_ordering::greater : (__v > 0 ? partial_ordering::less : __v);
+  }
+
+private:
+  _PartialOrdResult __value_;
+};
+
+inline constexpr partial_ordering partial_ordering::less(_PartialOrdResult::__less);
+inline constexpr partial_ordering partial_ordering::equivalent(_PartialOrdResult::__equiv);
+inline constexpr partial_ordering partial_ordering::greater(_PartialOrdResult::__greater);
+inline constexpr partial_ordering partial_ordering::unordered(_PartialOrdResult::__unordered);
+
+class weak_ordering {
+  using _ValueT _LIBCPP_NODEBUG = signed char;
+
+  _LIBCPP_HIDE_FROM_ABI explicit constexpr weak_ordering(_OrdResult __v) noexcept : __value_(_ValueT(__v)) {}
+
+public:
+  static const weak_ordering less;
+  static const weak_ordering equivalent;
+  static const weak_ordering greater;
+
+  _LIBCPP_HIDE_FROM_ABI constexpr operator partial_ordering() const noexcept {
+    return __value_ == 0 ? partial_ordering::equivalent
+                         : (__value_ < 0 ? partial_ordering::less : partial_ordering::greater);
+  }
+
+  // comparisons
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(weak_ordering, weak_ordering) noexcept = default;
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ < 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ <= 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ > 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ >= 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(_CmpUnspecifiedParam, weak_ordering __v) noexcept {
+    return 0 < __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(_CmpUnspecifiedParam, weak_ordering __v) noexcept {
+    return 0 <= __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(_CmpUnspecifiedParam, weak_ordering __v) noexcept {
+    return 0 > __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(_CmpUnspecifiedParam, weak_ordering __v) noexcept {
+    return 0 >= __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr weak_ordering operator<=>(weak_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr weak_ordering operator<=>(_CmpUnspecifiedParam, weak_ordering __v) noexcept {
+    return __v < 0 ? weak_ordering::greater : (__v > 0 ? weak_ordering::less : __v);
+  }
+
+private:
+  _ValueT __value_;
+};
+
+inline constexpr weak_ordering weak_ordering::less(_OrdResult::__less);
+inline constexpr weak_ordering weak_ordering::equivalent(_OrdResult::__equiv);
+inline constexpr weak_ordering weak_ordering::greater(_OrdResult::__greater);
+
+class strong_ordering {
+  using _ValueT _LIBCPP_NODEBUG = signed char;
+
+  _LIBCPP_HIDE_FROM_ABI explicit constexpr strong_ordering(_OrdResult __v) noexcept : __value_(_ValueT(__v)) {}
+
+public:
+  static const strong_ordering less;
+  static const strong_ordering equal;
+  static const strong_ordering equivalent;
+  static const strong_ordering greater;
+
+  // conversions
+  _LIBCPP_HIDE_FROM_ABI constexpr operator partial_ordering() const noexcept {
+    return __value_ == 0 ? partial_ordering::equivalent
+                         : (__value_ < 0 ? partial_ordering::less : partial_ordering::greater);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI constexpr operator weak_ordering() const noexcept {
+    return __value_ == 0 ? weak_ordering::equivalent : (__value_ < 0 ? weak_ordering::less : weak_ordering::greater);
+  }
+
+  // comparisons
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(strong_ordering, strong_ordering) noexcept = default;
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ == 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ < 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ <= 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ > 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v.__value_ >= 0;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<(_CmpUnspecifiedParam, strong_ordering __v) noexcept {
+    return 0 < __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator<=(_CmpUnspecifiedParam, strong_ordering __v) noexcept {
+    return 0 <= __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>(_CmpUnspecifiedParam, strong_ordering __v) noexcept {
+    return 0 > __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator>=(_CmpUnspecifiedParam, strong_ordering __v) noexcept {
+    return 0 >= __v.__value_;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
+  operator<=>(strong_ordering __v, _CmpUnspecifiedParam) noexcept {
+    return __v;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI friend constexpr strong_ordering
+  operator<=>(_CmpUnspecifiedParam, strong_ordering __v) noexcept {
+    return __v < 0 ? strong_ordering::greater : (__v > 0 ? strong_ordering::less : __v);
+  }
+
+private:
+  _ValueT __value_;
+};
+
+inline constexpr strong_ordering strong_ordering::less(_OrdResult::__less);
+inline constexpr strong_ordering strong_ordering::equal(_OrdResult::__equiv);
+inline constexpr strong_ordering strong_ordering::equivalent(_OrdResult::__equiv);
+inline constexpr strong_ordering strong_ordering::greater(_OrdResult::__greater);
+
+/// [cmp.categories.pre]/1
+/// The types partial_ordering, weak_ordering, and strong_ordering are
+/// collectively termed the comparison category types.
+template <class _Tp>
+concept __comparison_category =
+    is_same_v<_Tp, partial_ordering> || is_same_v<_Tp, weak_ordering> || is_same_v<_Tp, strong_ordering>;
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_ORDERING_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/partial_order.h b/third_party/libcxx/include/c++/v1/__compare/partial_order.h
new file mode 100644
index 0000000..1d2fae6
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/partial_order.h
@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__type_traits/decay.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [cmp.alg]
+namespace __partial_order {
+void partial_order() = delete;
+
+struct __fn {
+  // NOLINTBEGIN(libcpp-robust-against-adl) partial_order should use ADL, but only here
+  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(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return partial_ordering(partial_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+  // NOLINTEND(libcpp-robust-against-adl)
+
+  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()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return partial_ordering(compare_three_way()(std::forward<_Tp>(__t), std::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(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return partial_ordering(std::weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())) {
+    return __go(std::forward<_Tp>(__t), std::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 >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_PARTIAL_ORDER
diff --git a/third_party/libcxx/include/c++/v1/__compare/strong_order.h b/third_party/libcxx/include/c++/v1/__compare/strong_order.h
new file mode 100644
index 0000000..ba6de44
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/strong_order.h
@@ -0,0 +1,125 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__math/traits.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_floating_point.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+#include <cstdint>
+#include <limits>
+
+#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 >= 20
+
+// [cmp.alg]
+namespace __strong_order {
+void strong_order() = delete;
+
+struct __fn {
+  // NOLINTBEGIN(libcpp-robust-against-adl) strong_order should use ADL, but only here
+  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(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(strong_ordering(strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return strong_ordering(strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+  // NOLINTEND(libcpp-robust-against-adl)
+
+  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) || sizeof(_Dp) == sizeof(int64_t))) {
+      using _IntT = conditional_t<sizeof(_Dp) == sizeof(int32_t), int32_t, int64_t>;
+      _IntT __rx  = std::bit_cast<_IntT>(__t);
+      _IntT __ry  = std::bit_cast<_IntT>(__u);
+      __rx        = (__rx < 0) ? (numeric_limits<_IntT>::min() - __rx - 1) : __rx;
+      __ry        = (__ry < 0) ? (numeric_limits<_IntT>::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) {
+      static_assert(numeric_limits<_Dp>::radix == 2, "floating point type with a radix other than 2?");
+      return __math::signbit(__u) <=> __math::signbit(__t);
+    } else {
+      // They're unordered, so one of them must be a NAN.
+      // The order is -QNAN, -SNAN, numbers, +SNAN, +QNAN.
+      bool __t_is_nan      = __math::isnan(__t);
+      bool __u_is_nan      = __math::isnan(__u);
+      bool __t_is_negative = __math::signbit(__t);
+      bool __u_is_negative = __math::signbit(__u);
+      using _IntType =
+          conditional_t<sizeof(__t) == sizeof(int32_t),
+                        int32_t,
+                        conditional_t<sizeof(__t) == sizeof(int64_t), int64_t, void>>;
+      if constexpr (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 std::bit_cast<_IntType>(__t) <=> std::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()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(strong_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return strong_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<2>())) {
+    return __go(std::forward<_Tp>(__t), std::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 >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___COMPARE_STRONG_ORDER
diff --git a/third_party/libcxx/include/c++/v1/__compare/synth_three_way.h b/third_party/libcxx/include/c++/v1/__compare/synth_three_way.h
new file mode 100644
index 0000000..63bf56d
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/synth_three_way.h
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_SYNTH_THREE_WAY_H
+#define _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
+
+#include <__compare/ordering.h>
+#include <__compare/three_way_comparable.h>
+#include <__concepts/boolean_testable.h>
+#include <__config>
+#include <__utility/declval.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [expos.only.func]
+
+_LIBCPP_HIDE_FROM_ABI inline constexpr auto __synth_three_way = []<class _Tp, class _Up>(const _Tp& __t, const _Up& __u)
+  requires requires {
+    { __t < __u } -> __boolean_testable;
+    { __u < __t } -> __boolean_testable;
+  }
+{
+  if constexpr (three_way_comparable_with<_Tp, _Up>) {
+    return __t <=> __u;
+  } else {
+    if (__t < __u)
+      return weak_ordering::less;
+    if (__u < __t)
+      return weak_ordering::greater;
+    return weak_ordering::equivalent;
+  }
+};
+
+template <class _Tp, class _Up = _Tp>
+using __synth_three_way_result _LIBCPP_NODEBUG =
+    decltype(std::__synth_three_way(std::declval<_Tp&>(), std::declval<_Up&>()));
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_SYNTH_THREE_WAY_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/three_way_comparable.h b/third_party/libcxx/include/c++/v1/__compare/three_way_comparable.h
new file mode 100644
index 0000000..ad6d05a
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/three_way_comparable.h
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// 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_THREE_WAY_COMPARABLE_H
+#define _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
+
+#include <__compare/common_comparison_category.h>
+#include <__compare/ordering.h>
+#include <__concepts/common_reference_with.h>
+#include <__concepts/comparison_common_type.h>
+#include <__concepts/equality_comparable.h>
+#include <__concepts/same_as.h>
+#include <__concepts/totally_ordered.h>
+#include <__config>
+#include <__type_traits/common_reference.h>
+#include <__type_traits/make_const_lvalue_ref.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Tp, class _Cat>
+concept __compares_as = same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>;
+
+template <class _Tp, class _Cat = partial_ordering>
+concept three_way_comparable =
+    __weakly_equality_comparable_with<_Tp, _Tp> && __partially_ordered_with<_Tp, _Tp> &&
+    requires(__make_const_lvalue_ref<_Tp> __a, __make_const_lvalue_ref<_Tp> __b) {
+      { __a <=> __b } -> __compares_as<_Cat>;
+    };
+
+template <class _Tp, class _Up, class _Cat = partial_ordering>
+concept three_way_comparable_with =
+    three_way_comparable<_Tp, _Cat> && three_way_comparable<_Up, _Cat> && __comparison_common_type_with<_Tp, _Up> &&
+    three_way_comparable<common_reference_t<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>>, _Cat> &&
+    __weakly_equality_comparable_with<_Tp, _Up> && __partially_ordered_with<_Tp, _Up> &&
+    requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
+      { __t <=> __u } -> __compares_as<_Cat>;
+      { __u <=> __t } -> __compares_as<_Cat>;
+    };
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_THREE_WAY_COMPARABLE_H
diff --git a/third_party/libcxx/include/c++/v1/__compare/weak_order.h b/third_party/libcxx/include/c++/v1/__compare/weak_order.h
new file mode 100644
index 0000000..1a3e85f
--- /dev/null
+++ b/third_party/libcxx/include/c++/v1/__compare/weak_order.h
@@ -0,0 +1,105 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 <__math/traits.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_floating_point.h>
+#include <__type_traits/is_same.h>
+#include <__utility/forward.h>
+#include <__utility/priority_tag.h>
+
+#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+// [cmp.alg]
+namespace __weak_order {
+void weak_order() = delete;
+
+struct __fn {
+  // NOLINTBEGIN(libcpp-robust-against-adl) weak_order should use ADL, but only here
+  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(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(weak_ordering(weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return weak_ordering(weak_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+  // NOLINTEND(libcpp-robust-against-adl)
+
+  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 {
+    partial_ordering __po = (__t <=> __u);
+    if (__po == partial_ordering::less) {
+      return weak_ordering::less;
+    } else if (__po == partial_ordering::equivalent) {
+      return weak_ordering::equivalent;
+    } else if (__po == partial_ordering::greater) {
+      return weak_ordering::greater;
+    } else {
+      // Otherwise, at least one of them is a NaN.
+      bool __t_is_nan      = __math::isnan(__t);
+      bool __u_is_nan      = __math::isnan(__u);
+      bool __t_is_negative = __math::signbit(__t);
+      bool __u_is_negative = __math::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()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(weak_ordering(compare_three_way()(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return weak_ordering(compare_three_way()(std::forward<_Tp>(__t), std::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(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))))
+      -> decltype(weak_ordering(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
+    return weak_ordering(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u)));
+  }
+
+  template <class _Tp, class _Up>
+  _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
+      noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<3>())))
+          -> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<3>())) {
+    return __go(std::forward<_Tp>(__t), std::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 >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___COMPARE_WEAK_ORDER