Build System: Add support for __atomic built-in operators.

Add a check to configure.ac for __atomic_fetch_add support.  If found
use the __atomic built-in operators for ast_atomic_dec_and_test and
ast_atomic_fetchadd_int.

ASTERISK~27619

Change-Id: I65b4feb02bae368904ed0fb03f585c05f50a690e

2 files changed, 16 insertions, 3 deletions

diff --git a/include/asterisk/autoconfig.h.in b/include/asterisk/autoconfig.h.in
index f8bd0e376..18f9d4e75 100644
--- a/include/asterisk/autoconfig.h.in
+++ b/include/asterisk/autoconfig.h.in
@@ -188,6 +188,9 @@
 /* Define to 1 if you have the curses library. */
 #undef HAVE_CURSES
 
+/* Define to 1 if your C compiler provides __atomic operations. */
+#undef HAVE_C_ATOMICS
+
 /* Define if your system has the DAHDI headers. */
 #undef HAVE_DAHDI
 
@@ -292,7 +295,7 @@
 /* Define to 1 if you have the `ftruncate' function. */
 #undef HAVE_FTRUNCATE
 
-/* Define to 1 if your GCC C compiler provides atomic operations. */
+/* Define to 1 if your GCC C compiler provides __sync atomic operations. */
 #undef HAVE_GCC_ATOMICS
 
 /* Define to 1 if you have the `getcwd' function. */
diff --git a/include/asterisk/lock.h b/include/asterisk/lock.h
index 58c9a8383..d912b56d3 100644
--- a/include/asterisk/lock.h
+++ b/include/asterisk/lock.h
@@ -640,7 +640,12 @@ int ast_atomic_fetchadd_int_slow(volatile int *p, int v);
  * can be used to generate unique identifiers.
  */
 
-#if defined(HAVE_GCC_ATOMICS)
+#if defined(HAVE_C_ATOMICS)
+AST_INLINE_API(int ast_atomic_fetchadd_int(volatile int *p, int v),
+{
+	return __atomic_fetch_add(p, v, __ATOMIC_RELAXED);
+})
+#elif defined(HAVE_GCC_ATOMICS)
 AST_INLINE_API(int ast_atomic_fetchadd_int(volatile int *p, int v),
 {
 	return __sync_fetch_and_add(p, v);
@@ -687,7 +692,12 @@ AST_INLINE_API(int ast_atomic_fetchadd_int(volatile int *p, int v),
 /*! \brief decrement *p by 1 and return true if the variable has reached 0.
  * Useful e.g. to check if a refcount has reached 0.
  */
-#if defined(HAVE_GCC_ATOMICS)
+#if defined(HAVE_C_ATOMICS)
+AST_INLINE_API(int ast_atomic_dec_and_test(volatile int *p),
+{
+	return __atomic_sub_fetch(p, 1, __ATOMIC_RELAXED) == 0;
+})
+#elif defined(HAVE_GCC_ATOMICS)
 AST_INLINE_API(int ast_atomic_dec_and_test(volatile int *p),
 {
 	return __sync_sub_and_fetch(p, 1) == 0;