libstdc++: Add comparison operators to types from Numerics clause

Some more C++20 changes from P1614R2, "The Mothership has Landed".

	* include/bits/slice_array.h (operator==(const slice&, const slice&)):
	Define for C++20.
	* include/std/complex (operator==(const T&, const complex<T>&))
	(operator!=(const complex<T>&, const complex<T>&))
	(operator!=(const complex<T>&, const T&))
	(operator!=(const T&, const complex<T>&)): Do not declare for C++20.
	* testsuite/26_numerics/slice/compare.cc: New test.

4 files changed, 63 insertions, 0 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index fddba57d548..37ffbcf7b95 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,13 @@
 2020-04-08  Jonathan Wakely  <jwakely@redhat.com>
 
+	* include/bits/slice_array.h (operator==(const slice&, const slice&)):
+	Define for C++20.
+	* include/std/complex (operator==(const T&, const complex<T>&))
+	(operator!=(const complex<T>&, const complex<T>&))
+	(operator!=(const complex<T>&, const T&))
+	(operator!=(const T&, const complex<T>&)): Do not declare for C++20.
+	* testsuite/26_numerics/slice/compare.cc: New test.
+
 	* include/std/charconv (to_chars_result, from_chars_result): Add
 	defaulted equality comparisons for C++20.
 	* testsuite/20_util/from_chars/compare.cc: New test.
diff --git a/libstdc++-v3/include/bits/slice_array.h b/libstdc++-v3/include/bits/slice_array.h
index 32ba802c007..de33342e252 100644
--- a/libstdc++-v3/include/bits/slice_array.h
+++ b/libstdc++-v3/include/bits/slice_array.h
@@ -78,6 +78,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     ///  Return array stride of slice.
     size_t stride() const;
 
+#if __cpp_impl_three_way_comparison >= 201907L
+    /// Equality comparison
+    friend bool operator==(const slice&, const slice&) = default;
+#endif
+
   private:
     size_t _M_off;                      // offset
     size_t _M_sz;			// size
diff --git a/libstdc++-v3/include/std/complex b/libstdc++-v3/include/std/complex
index 4f170dc524a..f2917b8c368 100644
--- a/libstdc++-v3/include/std/complex
+++ b/libstdc++-v3/include/std/complex
@@ -468,6 +468,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     operator==(const complex<_Tp>& __x, const _Tp& __y)
     { return __x.real() == __y && __x.imag() == _Tp(); }
 
+#if !(__cpp_impl_three_way_comparison >= 201907L)
   template<typename _Tp>
     inline _GLIBCXX_CONSTEXPR bool
     operator==(const _Tp& __x, const complex<_Tp>& __y)
@@ -490,6 +491,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline _GLIBCXX_CONSTEXPR bool
     operator!=(const _Tp& __x, const complex<_Tp>& __y)
     { return __x != __y.real() || _Tp() != __y.imag(); }
+#endif
   //@}
 
   ///  Extraction operator for complex values.
diff --git a/libstdc++-v3/testsuite/26_numerics/slice/compare.cc b/libstdc++-v3/testsuite/26_numerics/slice/compare.cc
new file mode 100644
index 00000000000..4459cf22eb6
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/slice/compare.cc
@@ -0,0 +1,48 @@
+// 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 <valarray>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  std::slice s1(1, 2, 3);
+  VERIFY( s1 == s1 );
+  VERIFY( !(s1 != s1) );
+  std::slice s2(1, 2, 3);
+  VERIFY( s2 == s1 );
+  VERIFY( !(s2 != s1) );
+  std::slice s3(3, 2, 3);
+  VERIFY( s3 != s1 );
+  VERIFY( !(s3 == s1) );
+  std::slice s4(1, 3, 3);
+  VERIFY( s4 != s1 );
+  VERIFY( !(s4 == s1) );
+  std::slice s5(1, 2, 4);
+  VERIFY( s5 != s1 );
+  VERIFY( !(s5 == s1) );
+}
+
+int
+main()
+{
+  test01();
+}