builtins: Implement the functions from stdatomic.h

Talking to John and Doug, we concluded that these functions from
stdatomic really do belong here in compiler-rt rather than in libc,
since the compiler owns stdatomic.h and these need to refer to
clang-specific builtins. Nonetheless, I've only added these on darwin
for now - other platforms should probably do the same unless their
libc does implement these functions.

llvm-svn: 236805

1 files changed, 20 insertions, 0 deletions

diff --git a/compiler-rt/lib/builtins/atomic_flag_test_and_set_explicit.c b/compiler-rt/lib/builtins/atomic_flag_test_and_set_explicit.c
new file mode 100644
index 00000000000..eaa5be08df4
--- /dev/null
+++ b/compiler-rt/lib/builtins/atomic_flag_test_and_set_explicit.c
@@ -0,0 +1,20 @@
+/*===-- atomic_flag_test_and_set_explicit.c ---------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ *===------------------------------------------------------------------------===
+ *
+ * This file implements atomic_flag_test_and_set_explicit from C11's stdatomic.h
+ *
+ *===------------------------------------------------------------------------===
+ */
+
+#include <stdatomic.h>
+#undef atomic_flag_test_and_set_explicit
+_Bool atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
+                                        memory_order order) {
+  return __c11_atomic_exchange(&(object)->_Value, 1, order);
+}