apr_atomic: Use __atomic builtins when available.

Unlike Intel's atomic builtins (__sync_*), the more recent __atomic builtins
provide atomic load and store for weakly ordered architectures like ARM32 or
powerpc[64], so use them when available (gcc 4.6.3+).

[Reverted by r1894619]


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@1894618 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 35 insertions, 3 deletions

diff --git a/atomic/unix/builtins64.c b/atomic/unix/builtins64.c
index 4a4b685c7..0ac950c15 100644
--- a/atomic/unix/builtins64.c
+++ b/atomic/unix/builtins64.c
@@ -20,45 +20,77 @@
 
 APR_DECLARE(apr_uint64_t) apr_atomic_read64(volatile apr_uint64_t *mem)
 {
+#if HAVE__ATOMIC_BUILTINS
+    return __atomic_load_n(mem, __ATOMIC_SEQ_CST);
+#else
     return *mem;
+#endif
 }
 
 APR_DECLARE(void) apr_atomic_set64(volatile apr_uint64_t *mem, apr_uint64_t val)
 {
+#if HAVE__ATOMIC_BUILTINS
+    __atomic_store_n(mem, val, __ATOMIC_SEQ_CST);
+#else
     *mem = val;
+#endif
 }
 
 APR_DECLARE(apr_uint64_t) apr_atomic_add64(volatile apr_uint64_t *mem, apr_uint64_t val)
 {
+#if HAVE__ATOMIC_BUILTINS
+    return __atomic_fetch_add(mem, val, __ATOMIC_SEQ_CST);
+#else
     return __sync_fetch_and_add(mem, val);
+#endif
 }
 
 APR_DECLARE(void) apr_atomic_sub64(volatile apr_uint64_t *mem, apr_uint64_t val)
 {
+#if HAVE__ATOMIC_BUILTINS
+    __atomic_fetch_sub(mem, val, __ATOMIC_SEQ_CST);
+#else
     __sync_fetch_and_sub(mem, val);
+#endif
 }
 
 APR_DECLARE(apr_uint64_t) apr_atomic_inc64(volatile apr_uint64_t *mem)
 {
+#if HAVE__ATOMIC_BUILTINS
+    return __atomic_fetch_add(mem, 1, __ATOMIC_SEQ_CST);
+#else
     return __sync_fetch_and_add(mem, 1);
+#endif
 }
 
 APR_DECLARE(int) apr_atomic_dec64(volatile apr_uint64_t *mem)
 {
+#if HAVE__ATOMIC_BUILTINS
+    return __atomic_sub_fetch(mem, 1, __ATOMIC_SEQ_CST);
+#else
     return __sync_sub_and_fetch(mem, 1);
+#endif
 }
 
-APR_DECLARE(apr_uint64_t) apr_atomic_cas64(volatile apr_uint64_t *mem, apr_uint64_t with,
+APR_DECLARE(apr_uint64_t) apr_atomic_cas64(volatile apr_uint64_t *mem, apr_uint64_t val,
                                            apr_uint64_t cmp)
 {
-    return __sync_val_compare_and_swap(mem, cmp, with);
+#if HAVE__ATOMIC_BUILTINS
+    __atomic_compare_exchange_n(mem, &cmp, val, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+    return cmp;
+#else
+    return __sync_val_compare_and_swap(mem, cmp, val);
+#endif
 }
 
 APR_DECLARE(apr_uint64_t) apr_atomic_xchg64(volatile apr_uint64_t *mem, apr_uint64_t val)
 {
+#if HAVE__ATOMIC_BUILTINS
+    return __atomic_exchange_n(mem, val, __ATOMIC_SEQ_CST);
+#else
     __sync_synchronize();
-
     return __sync_lock_test_and_set(mem, val);
+#endif
 }
 
 #endif /* USE_ATOMICS_BUILTINS */