Index: libcxx/include/string
===================================================================
--- libcxx/include/string
+++ libcxx/include/string
@@ -356,64 +356,71 @@
 
 template<class charT, class traits, class Allocator>
 bool operator==(const basic_string<charT, traits, Allocator>& lhs,
-                const basic_string<charT, traits, Allocator>& rhs) noexcept;
+                          const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
 template<class charT, class traits, class Allocator>
-bool operator==(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
+bool operator==(const basic_string<charT,traits,Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator==(const basic_string<charT,traits,Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator!=(const basic_string<charT,traits,Allocator>& lhs,
                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator!=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator!=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator< (const basic_string<charT, traits, Allocator>& lhs,
                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator< (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator< (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator> (const basic_string<charT, traits, Allocator>& lhs,
                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator> (const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator> (const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator<=(const basic_string<charT, traits, Allocator>& lhs,
                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator<=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator<=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator>=(const basic_string<charT, traits, Allocator>& lhs,
                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator>=(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
 
-template<class charT, class traits, class Allocator>
+template<class charT, class traits, class Allocator> (Until C++17)
 bool operator>=(const charT* lhs, const basic_string<charT, traits, Allocator>& rhs) noexcept;
 
+template<class charT, class traits, class Allocator> (Since C++20)
+bool operator<=>(const basic_string<charT, traits, Allocator>& lhs,
+                 const basic_string<charT, traits, Allocator>& rhs) noexcept;
+
+template<class charT, class traits, class Allocator> (Since C++20)
+operator<=>(const basic_string<charT, traits, Allocator>& lhs, const charT* rhs) noexcept;
+
 template<class charT, class traits, class Allocator>
 void swap(basic_string<charT, traits, Allocator>& lhs,
           basic_string<charT, traits, Allocator>& rhs)
@@ -3935,19 +3942,6 @@
 }
 
 // operator==
-
-template<class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
-bool
-operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
-           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
-{
-    size_t __lhs_sz = __lhs.size();
-    return __lhs_sz == __rhs.size() && _Traits::compare(__lhs.data(),
-                                                        __rhs.data(),
-                                                        __lhs_sz) == 0;
-}
-
 template<class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -3967,6 +3961,58 @@
     return true;
 }
 
+#if !defined(_LIBCPP_HAS_NO_SPACESHIP_OPERATOR)
+// operator==
+template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
+{
+    return basic_string_view<_CharT, _Traits>(__lhs) == basic_string_view<_CharT, _Traits>(__rhs);
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+           const _CharT* __rhs) _NOEXCEPT
+{
+    return basic_string_view<_CharT, _Traits>(__lhs) == basic_string_view<_CharT, _Traits>(__rhs);
+}
+
+// operator<=>
+template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_INLINE_VISIBILITY
+auto
+operator<=>(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+            const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
+{
+    return basic_string_view<_CharT, _Traits>(__lhs) <=> basic_string_view<_CharT, _Traits>(__rhs);
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+_LIBCPP_INLINE_VISIBILITY
+auto
+operator<=>(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+            const _CharT* __rhs) _NOEXCEPT
+{
+    return basic_string_view<_CharT, _Traits>(__lhs) <=> basic_string_view<_CharT, _Traits>(__rhs);
+}
+#else
+// operator==
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const basic_string<_CharT, _Traits, _Allocator>& __lhs,
+           const basic_string<_CharT, _Traits, _Allocator>& __rhs) _NOEXCEPT
+{
+    size_t __lhs_sz = __lhs.size();
+    return __lhs_sz == __rhs.size() && _Traits::compare(__lhs.data(),
+                                                        __rhs.data(),
+                                                        __lhs_sz) == 0;
+}
+
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -4135,6 +4181,7 @@
 {
     return !(__lhs < __rhs);
 }
+#endif // _LIBCPP_HAS_NO_SPACESHIP_OPERATOR
 
 // operator +
 
Index: libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/pointer_string.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/pointer_string.pass.cpp
@@ -0,0 +1,74 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+// template<class charT, class traits, class Allocator>
+//   bool operator<=>(const charT* lhs, const basic_string<charT,traits,Allocator>& rhs);
+
+#include <string>
+#include <compare>
+#include <cassert>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class S>
+void
+test(const typename S::value_type* lhs, const S& rhs, std::weak_ordering x)
+{
+    assert((lhs <=> rhs) == x);
+}
+
+
+int main(int, char**)
+{
+    {
+    typedef std::string S;
+    test("", S(""), std::strong_ordering::equal);
+    test("", S("abcde"), std::strong_ordering::less);
+    test("", S("abcdefghij"), std::strong_ordering::less);
+    test("", S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test("abcde", S(""), std::strong_ordering::greater);
+    test("abcde", S("abcde"), std::strong_ordering::equal);
+    test("abcde", S("abcdefghij"), std::strong_ordering::less);
+    test("abcde", S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test("abcdefghij", S(""), std::strong_ordering::greater);
+    test("abcdefghij", S("abcde"), std::strong_ordering::greater);
+    test("abcdefghij", S("abcdefghij"), std::strong_ordering::equal);
+    test("abcdefghij", S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test("abcdefghijklmnopqrst", S(""), std::strong_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcde"), std::strong_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcdefghij"), std::strong_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcdefghijklmnopqrst"), std::strong_ordering::equal);
+    }
+
+    {
+    typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
+    test("", S(""), std::weak_ordering::equivalent);
+    test("", S("abcde"), std::weak_ordering::less);
+    test("", S("abcdefghij"), std::weak_ordering::less);
+    test("", S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test("abcde", S(""), std::weak_ordering::greater);
+    test("abcde", S("abcde"), std::weak_ordering::equivalent);
+    test("abcde", S("abcdefghij"), std::weak_ordering::less);
+    test("abcde", S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test("abcdefghij", S(""), std::weak_ordering::greater);
+    test("abcdefghij", S("abcde"), std::weak_ordering::greater);
+    test("abcdefghij", S("abcdefghij"), std::weak_ordering::equivalent);
+    test("abcdefghij", S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test("abcdefghijklmnopqrst", S(""), std::weak_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcde"), std::weak_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcdefghij"), std::weak_ordering::greater);
+    test("abcdefghijklmnopqrst", S("abcdefghijklmnopqrst"), std::weak_ordering::equivalent);
+    }
+
+  return 0;
+}
Index: libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_pointer.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_pointer.pass.cpp
@@ -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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+// template<class charT, class traits, class Allocator>
+//   bool operator>(const basic_string<charT,traits,Allocator>& lhs, const charT* rhs);
+
+#include <string>
+#include <compare>
+#include <cassert>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class S>
+void
+test(const S& lhs, const typename S::value_type* rhs, std::weak_ordering x)
+{
+    assert((lhs <=> rhs) == x);
+}
+
+int main(int, char**)
+{
+    {
+    typedef std::string S;
+    test(S(""), "", std::strong_ordering::equal);
+    test(S(""), "abcde", std::strong_ordering::less);
+    test(S(""), "abcdefghij", std::strong_ordering::less);
+    test(S(""), "abcdefghijklmnopqrst", std::strong_ordering::less);
+    test(S("abcde"), "", std::strong_ordering::greater);
+    test(S("abcde"), "abcde", std::strong_ordering::equal);
+    test(S("abcde"), "abcdefghij", std::strong_ordering::less);
+    test(S("abcde"), "abcdefghijklmnopqrst", std::strong_ordering::less);
+    test(S("abcdefghij"), "", std::strong_ordering::greater);
+    test(S("abcdefghij"), "abcde", std::strong_ordering::greater);
+    test(S("abcdefghij"), "abcdefghij", std::strong_ordering::equal);
+    test(S("abcdefghij"), "abcdefghijklmnopqrst", std::strong_ordering::less);
+    test(S("abcdefghijklmnopqrst"), "", std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcde", std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcdefghij", std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcdefghijklmnopqrst", std::strong_ordering::equal);
+    }
+
+    {
+    typedef std::basic_string<char, std::char_traits<char>, min_allocator<char>> S;
+    test(S(""), "", std::weak_ordering::equivalent);
+    test(S(""), "abcde", std::weak_ordering::less);
+    test(S(""), "abcdefghij", std::weak_ordering::less);
+    test(S(""), "abcdefghijklmnopqrst", std::weak_ordering::less);
+    test(S("abcde"), "", std::weak_ordering::greater);
+    test(S("abcde"), "abcde", std::weak_ordering::equivalent);
+    test(S("abcde"), "abcdefghij", std::weak_ordering::less);
+    test(S("abcde"), "abcdefghijklmnopqrst", std::weak_ordering::less);
+    test(S("abcdefghij"), "", std::weak_ordering::greater);
+    test(S("abcdefghij"), "abcde", std::weak_ordering::greater);
+    test(S("abcdefghij"), "abcdefghij", std::weak_ordering::equivalent);
+    test(S("abcdefghij"), "abcdefghijklmnopqrst", std::weak_ordering::less);
+    test(S("abcdefghijklmnopqrst"), "", std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcde", std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcdefghij", std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), "abcdefghijklmnopqrst", std::weak_ordering::equivalent);
+    }
+
+  return 0;
+}
Index: libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_string.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_string.pass.cpp
@@ -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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+// we get this comparison "for free" because the string implicitly converts to the string_view
+
+#include <string>
+#include <compare>
+#include <cassert>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class S>
+void
+test(const S& lhs, const S& rhs, std::weak_ordering x)
+{
+    assert((lhs <=> rhs) == x);
+}
+
+int main(int, char**)
+{
+    {
+    typedef std::string S;
+    test(S(""), S(""), std::strong_ordering::equal);
+    test(S(""), S("abcde"), std::strong_ordering::less);
+    test(S(""), S("abcdefghij"), std::strong_ordering::less);
+    test(S(""), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcde"), S(""), std::strong_ordering::greater);
+    test(S("abcde"), S("abcde"), std::strong_ordering::equal);
+    test(S("abcde"), S("abcdefghij"), std::strong_ordering::less);
+    test(S("abcde"), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcdefghij"), S(""), std::strong_ordering::greater);
+    test(S("abcdefghij"), S("abcde"), std::strong_ordering::greater);
+    test(S("abcdefghij"), S("abcdefghij"), std::strong_ordering::equal);
+    test(S("abcdefghij"), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcdefghijklmnopqrst"), S(""), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcde"), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcdefghij"), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcdefghijklmnopqrst"), std::strong_ordering::equal);
+    }
+
+    {
+    typedef std::basic_string     <char, std::char_traits<char>, min_allocator<char>> S;
+    test(S(""), S(""), std::weak_ordering::equivalent);
+    test(S(""), S("abcde"), std::weak_ordering::less);
+    test(S(""), S("abcdefghij"), std::weak_ordering::less);
+    test(S(""), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcde"), S(""), std::weak_ordering::greater);
+    test(S("abcde"), S("abcde"), std::weak_ordering::equivalent);
+    test(S("abcde"), S("abcdefghij"), std::weak_ordering::less);
+    test(S("abcde"), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcdefghij"), S(""), std::weak_ordering::greater);
+    test(S("abcdefghij"), S("abcde"), std::weak_ordering::greater);
+    test(S("abcdefghij"), S("abcdefghij"), std::weak_ordering::equivalent);
+    test(S("abcdefghij"), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcdefghijklmnopqrst"), S(""), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcde"), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcdefghij"), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), S("abcdefghijklmnopqrst"), std::weak_ordering::equivalent);
+    }
+
+  return 0;
+}
Index: libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_string_view.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_string_view.pass.cpp
@@ -0,0 +1,74 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+// we get this comparison "for free" because the string implicitly converts to the string_view
+
+#include <string>
+#include <compare>
+#include <cassert>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class S, class SV>
+void
+test(const S& lhs, SV rhs, std::weak_ordering x)
+{
+    assert((lhs <=> rhs) == x);
+}
+
+int main(int, char**)
+{
+    {
+    typedef std::string S;
+    typedef std::string_view SV;
+    test(S(""), SV(""), std::strong_ordering::equal);
+    test(S(""), SV("abcde"), std::strong_ordering::less);
+    test(S(""), SV("abcdefghij"), std::strong_ordering::less);
+    test(S(""), SV("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcde"), SV(""), std::strong_ordering::greater);
+    test(S("abcde"), SV("abcde"), std::strong_ordering::equal);
+    test(S("abcde"), SV("abcdefghij"), std::strong_ordering::less);
+    test(S("abcde"), SV("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcdefghij"), SV(""), std::strong_ordering::greater);
+    test(S("abcdefghij"), SV("abcde"), std::strong_ordering::greater);
+    test(S("abcdefghij"), SV("abcdefghij"), std::strong_ordering::equal);
+    test(S("abcdefghij"), SV("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(S("abcdefghijklmnopqrst"), SV(""), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcde"), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcdefghij"), std::strong_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcdefghijklmnopqrst"), std::strong_ordering::equal);
+    }
+
+    {
+    typedef std::basic_string     <char, std::char_traits<char>, min_allocator<char>> S;
+    typedef std::basic_string_view<char, std::char_traits<char>> SV;
+    test(S(""), SV(""), std::weak_ordering::equivalent);
+    test(S(""), SV("abcde"), std::weak_ordering::less);
+    test(S(""), SV("abcdefghij"), std::weak_ordering::less);
+    test(S(""), SV("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcde"), SV(""), std::weak_ordering::greater);
+    test(S("abcde"), SV("abcde"), std::weak_ordering::equivalent);
+    test(S("abcde"), SV("abcdefghij"), std::weak_ordering::less);
+    test(S("abcde"), SV("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcdefghij"), SV(""), std::weak_ordering::greater);
+    test(S("abcdefghij"), SV("abcde"), std::weak_ordering::greater);
+    test(S("abcdefghij"), SV("abcdefghij"), std::weak_ordering::equivalent);
+    test(S("abcdefghij"), SV("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(S("abcdefghijklmnopqrst"), SV(""), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcde"), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcdefghij"), std::weak_ordering::greater);
+    test(S("abcdefghijklmnopqrst"), SV("abcdefghijklmnopqrst"), std::weak_ordering::equivalent);
+    }
+
+  return 0;
+}
Index: libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_view_string.pass.cpp
===================================================================
--- /dev/null
+++ libcxx/test/std/strings/basic.string/string.nonmembers/string_opcmp/string_view_string.pass.cpp
@@ -0,0 +1,74 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++98, c++03, c++11, c++14, c++17
+
+// <string>
+
+// we get this comparison "for free" because the string implicitly converts to the string_view
+
+#include <string>
+#include <compare>
+#include <cassert>
+
+#include "test_macros.h"
+#include "min_allocator.h"
+
+template <class SV, class S>
+void
+test(SV lhs, const S& rhs, std::weak_ordering x)
+{
+    assert((lhs <=> rhs) == x);
+}
+
+int main(int, char**)
+{
+    {
+    typedef std::string S;
+    typedef std::string_view SV;
+    test(SV(""), S(""), std::strong_ordering::equal);
+    test(SV(""), S("abcde"), std::strong_ordering::less);
+    test(SV(""), S("abcdefghij"), std::strong_ordering::less);
+    test(SV(""), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(SV("abcde"), S(""), std::strong_ordering::greater);
+    test(SV("abcde"), S("abcde"), std::strong_ordering::equal);
+    test(SV("abcde"), S("abcdefghij"), std::strong_ordering::less);
+    test(SV("abcde"), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(SV("abcdefghij"), S(""), std::strong_ordering::greater);
+    test(SV("abcdefghij"), S("abcde"), std::strong_ordering::greater);
+    test(SV("abcdefghij"), S("abcdefghij"), std::strong_ordering::equal);
+    test(SV("abcdefghij"), S("abcdefghijklmnopqrst"), std::strong_ordering::less);
+    test(SV("abcdefghijklmnopqrst"), S(""), std::strong_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcde"), std::strong_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcdefghij"), std::strong_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcdefghijklmnopqrst"), std::strong_ordering::equal);
+    }
+
+    {
+    typedef std::basic_string     <char, std::char_traits<char>, min_allocator<char>> S;
+    typedef std::basic_string_view<char, std::char_traits<char>> SV;
+    test(SV(""), S(""), std::weak_ordering::equivalent);
+    test(SV(""), S("abcde"), std::weak_ordering::less);
+    test(SV(""), S("abcdefghij"), std::weak_ordering::less);
+    test(SV(""), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(SV("abcde"), S(""), std::weak_ordering::greater);
+    test(SV("abcde"), S("abcde"), std::weak_ordering::equivalent);
+    test(SV("abcde"), S("abcdefghij"), std::weak_ordering::less);
+    test(SV("abcde"), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(SV("abcdefghij"), S(""), std::weak_ordering::greater);
+    test(SV("abcdefghij"), S("abcde"), std::weak_ordering::greater);
+    test(SV("abcdefghij"), S("abcdefghij"), std::weak_ordering::equivalent);
+    test(SV("abcdefghij"), S("abcdefghijklmnopqrst"), std::weak_ordering::less);
+    test(SV("abcdefghijklmnopqrst"), S(""), std::weak_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcde"), std::weak_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcdefghij"), std::weak_ordering::greater);
+    test(SV("abcdefghijklmnopqrst"), S("abcdefghijklmnopqrst"), std::weak_ordering::equivalent);
+    }
+
+  return 0;
+}