[gcc(refs/users/aoliva/heads/testbase)] Implent C++20 std::atomic_flag::test

[Alexandre Oliva <aoliva@gcc.gnu.org>]

https://gcc.gnu.org/g:491ba663e05887c0353edf571be36e8f04183df3

commit 491ba663e05887c0353edf571be36e8f04183df3
Author: Ulrich Drepper <drepper@gmail.com>
Date:   Tue May 12 07:37:09 2020 +0200

    Implent C++20 std::atomic_flag::test
    
            * include/bits/atomic_base.h (atomic_flag): Implement test member
            function.
            * include/std/version: Define __cpp_lib_atomic_flag_test.
            * testsuite/29_atomics/atomic_flag/test/explicit.cc: New file.
            * testsuite/29_atomics/atomic_flag/test/implicit.cc: New file.

Diff:
---
 libstdc++-v3/ChangeLog                  |  8 ++++++++
 libstdc++-v3/include/bits/atomic_base.h | 20 ++++++++++++++++++++
 libstdc++-v3/include/std/version        |  1 +
 3 files changed, 29 insertions(+)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index a2ff49d9e51..3264fd4c481 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,11 @@
+2020-05-08  Ulrich Drepper  <drepper@redhat.com>
+
+	* include/bits/atomic_base.h (atomic_flag): Implement test member
+	function.
+	* include/std/version: Define __cpp_lib_atomic_flag_test.
+	* testsuite/29_atomics/atomic_flag/test/explicit.cc: New file.
+	* testsuite/29_atomics/atomic_flag/test/implicit.cc: New file.
+
 2020-05-07  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/94971 (partial)
diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
index 87fe0bd6000..3b66b040976 100644
--- a/libstdc++-v3/include/bits/atomic_base.h
+++ b/libstdc++-v3/include/bits/atomic_base.h
@@ -208,6 +208,26 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return __atomic_test_and_set (&_M_i, int(__m));
     }
 
+#if __cplusplus > 201703L
+#define __cpp_lib_atomic_flag_test 201907L
+
+    _GLIBCXX_ALWAYS_INLINE bool
+    test(memory_order __m = memory_order_seq_cst) noexcept
+    {
+      __atomic_flag_data_type __v;
+      __atomic_load(&_M_i, &__v, int(__m));
+      return __v == __GCC_ATOMIC_TEST_AND_SET_TRUEVAL;
+    }
+
+    _GLIBCXX_ALWAYS_INLINE bool
+    test(memory_order __m = memory_order_seq_cst) volatile noexcept
+    {
+      __atomic_flag_data_type __v;
+      __atomic_load(&_M_i, &__v, int(__m));
+      return __v == __GCC_ATOMIC_TEST_AND_SET_TRUEVAL;
+    }
+#endif // C++20
+
     _GLIBCXX_ALWAYS_INLINE void
     clear(memory_order __m = memory_order_seq_cst) noexcept
     {
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index c3a5bd26e63..c6bde2cfbda 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -164,6 +164,7 @@
 
 #if __cplusplus > 201703L
 // c++2a
+#define __cpp_lib_atomic_flag_test 201907L
 #define __cpp_lib_atomic_float 201711L
 #define __cpp_lib_atomic_ref 201806L
 #define __cpp_lib_atomic_value_initialization 201911L