--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libstdc++-v3/testsuite/23_containers/vector/cmp_c++20.cc	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,161 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do run { target c++2a } }
+
+#include <vector>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::vector<int> c1{ 1, 2, 3 }, c2{ 1, 2, 3, 4 }, c3{ 1, 2, 4 };
+  VERIFY( c1 == c1 );
+  VERIFY( std::is_eq(c1 <=> c1) );
+  VERIFY( c1 < c2 );
+  VERIFY( std::is_lt(c1 <=> c2) );
+  VERIFY( c1 < c3 );
+  VERIFY( std::is_lt(c1 <=> c3) );
+  VERIFY( c2 < c3 );
+  VERIFY( std::is_lt(c2 <=> c3) );
+
+  static_assert( std::totally_ordered<std::vector<int>> );
+
+  static_assert( std::three_way_comparable<std::vector<int>,
+					   std::strong_ordering> );
+  static_assert( ! std::three_way_comparable<std::vector<float>,
+					     std::strong_ordering> );
+  static_assert( ! std::three_way_comparable<std::vector<float>,
+					     std::weak_ordering> );
+  static_assert( std::three_way_comparable<std::vector<float>,
+					   std::partial_ordering> );
+
+  struct E
+  {
+    bool operator==(E) { return true; }
+  };
+  static_assert( ! std::totally_ordered<std::vector<E>> );
+  static_assert( ! std::three_way_comparable<E> );
+  static_assert( ! std::three_way_comparable<std::vector<E>> );
+}
+
+void
+test02()
+{
+  struct W
+  {
+    int value = 0;
+
+    bool operator==(W rhs) const noexcept
+    { return (value | 1) == (rhs.value | 1); }
+
+    std::weak_ordering
+    operator<=>(W rhs) const noexcept
+    { return (value | 1) <=> (rhs.value | 1); }
+  };
+
+  static_assert( std::totally_ordered<std::vector<W>> );
+
+  std::vector<W> c1{ {1}, {2}, {3} }, c2{ {0}, {3}, {3} };
+  static_assert( std::same_as<decltype(c1 <=> c1), std::weak_ordering> );
+  VERIFY( c1 == c2 );
+  VERIFY( std::is_eq(c1 <=> c2) );
+}
+
+void
+test03()
+{
+  struct P
+  {
+    int value = 0;
+
+    bool operator==(P rhs) const noexcept
+    {
+      if (value < 0 || rhs.value < 0)
+	return false;
+      return value == rhs.value;
+    }
+
+    std::partial_ordering
+    operator<=>(P rhs) const noexcept
+    {
+      if (value < 0 || rhs.value < 0)
+	return std::partial_ordering::unordered;
+      return value <=> rhs.value;
+    }
+  };
+
+  static_assert( std::totally_ordered<std::vector<P>> );
+
+  std::vector<P> c{ {1}, {2}, {-3} };
+  static_assert( std::three_way_comparable<P> );
+  static_assert( std::same_as<decltype(c <=> c), std::partial_ordering> );
+  VERIFY( (c <=> c) == std::partial_ordering::unordered );
+}
+
+void
+test04()
+{
+  struct L
+  {
+    int value = 0;
+
+    bool operator<(L rhs) const noexcept { return value < rhs.value; }
+  };
+
+  static_assert( std::totally_ordered<std::vector<L>> );
+
+  std::vector<L> c{ {1}, {2}, {3} }, d{ {1}, {2}, {3}, {4} };
+  static_assert( std::same_as<decltype(c <=> c), std::weak_ordering> );
+  VERIFY( std::is_lt(c <=> d) );
+}
+
+void
+test05()
+{
+  // vector iterators are random access, so should support <=>
+
+  std::vector<int> c{ 1, 2, 3 };
+  VERIFY( c.begin() == c.cbegin() );
+  VERIFY( std::is_eq(c.begin() <=> c.cbegin()) );
+
+  VERIFY( c.begin() < c.end() );
+  VERIFY( std::is_lt(c.begin() <=> c.end()) );
+
+  VERIFY( c.begin() < c.cend() );
+  VERIFY( std::is_lt(c.begin() <=> c.cend()) );
+
+  VERIFY( c.crbegin() == c.rbegin() );
+  VERIFY( std::is_eq(c.crbegin() <=> c.rbegin()) );
+
+  VERIFY( c.rend() > c.rbegin() );
+  VERIFY( std::is_gt(c.rend() <=> c.rbegin()) );
+
+  static_assert( std::same_as<decltype(c.begin() <=> c.begin()),
+			      std::strong_ordering> );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+  test05();
+}