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

configure

@@ -17893,8 +17893,8 @@ fi
 done
 
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler atomic operations" >&5
-$as_echo_n "checking for compiler atomic operations... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler sync operations" >&5
+$as_echo_n "checking for compiler sync operations... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
@@ -17916,6 +17916,33 @@ else
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler atomic operations" >&5
+$as_echo_n "checking for compiler atomic operations... " >&6; }
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+int foo1; int foo2 = __atomic_fetch_add(&foo1, 1, __ATOMIC_RELAXED);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+$as_echo "yes" >&6; }
+
+$as_echo "#define HAVE_C_ATOMICS 1" >>confdefs.h
+
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext

configure.ac

@@ -1070,11 +1070,19 @@ AC_LINK_IFELSE(
 # for FreeBSD thr_self
 AC_CHECK_HEADERS([sys/thr.h])
 
-AC_MSG_CHECKING(for compiler atomic operations)
+AC_MSG_CHECKING(for compiler sync operations)
 AC_LINK_IFELSE(
 [AC_LANG_PROGRAM([], [int foo1; int foo2 = __sync_fetch_and_add(&foo1, 1);])],
 AC_MSG_RESULT(yes)
-AC_DEFINE([HAVE_GCC_ATOMICS], 1, [Define to 1 if your GCC C compiler provides atomic operations.]),
+AC_DEFINE([HAVE_GCC_ATOMICS], 1, [Define to 1 if your GCC C compiler provides __sync atomic operations.]),
+AC_MSG_RESULT(no)
+)
+
+AC_MSG_CHECKING(for compiler atomic operations)
+AC_LINK_IFELSE(
+[AC_LANG_PROGRAM([], [int foo1; int foo2 = __atomic_fetch_add(&foo1, 1, __ATOMIC_RELAXED);])],
+AC_MSG_RESULT(yes)
+AC_DEFINE([HAVE_C_ATOMICS], 1, [Define to 1 if your C compiler provides __atomic operations.]),
 AC_MSG_RESULT(no)
 )
 

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. */

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;