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+).



git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@1894621 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 36 insertions, 9 deletions

diff --git a/configure.in b/configure.in
index 5fa318306..3e4be99cc 100644
--- a/configure.in
+++ b/configure.in
@@ -487,7 +487,7 @@ esac
 
 AC_CACHE_CHECK([whether the compiler provides atomic builtins], [ap_cv_atomic_builtins],
 [AC_TRY_RUN([
-int main()
+int main(int argc, const char *const *argv)
 {
     unsigned long val = 1010, tmp, *mem = &val;
 
@@ -495,7 +495,6 @@ int main()
         return 1;
 
     tmp = val;
-
     if (__sync_fetch_and_sub(mem, 1010) != tmp || val != 1010)
         return 1;
 
@@ -503,28 +502,56 @@ int main()
         return 1;
 
     tmp = 3030;
-
     if (__sync_val_compare_and_swap(mem, 0, tmp) != 0 || val != tmp)
         return 1;
 
+    __sync_synchronize();
     if (__sync_lock_test_and_set(&val, 4040) != 3030)
         return 1;
 
-    mem = &tmp;
+    if (__sync_val_compare_and_swap(&mem, &val, &tmp) != &val || mem != &tmp)
+        return 1;
+
+    return 0;
+}], [ap_cv_atomic_builtins=yes], [ap_cv_atomic_builtins=no], [ap_cv_atomic_builtins=no])])
+
+AC_CACHE_CHECK([whether the compiler provides __atomic builtins], [ap_cv__atomic_builtins],
+[AC_TRY_RUN([
+int main(int argc, const char *const *argv)
+{
+    unsigned long val = 1010, tmp, *mem = &val, *ptmp;
 
-    if (__sync_val_compare_and_swap(&mem, &tmp, &val) != &tmp)
+    if (__atomic_fetch_add(&val, 1010, __ATOMIC_SEQ_CST) != 1010 || val != 2020)
         return 1;
 
-    __sync_synchronize();
+    tmp = val;
+    if (__atomic_fetch_sub(mem, 1010, __ATOMIC_SEQ_CST) != tmp || val != 1010)
+        return 1;
+
+    if (__atomic_sub_fetch(&val, 1010, __ATOMIC_SEQ_CST) != 0 || val != 0)
+        return 1;
 
-    if (mem != &val)
+    tmp = val;
+    if (!__atomic_compare_exchange_n(mem, &tmp, 3030, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
+            || tmp != 0)
+        return 1;
+
+    if (__atomic_exchange_n(&val, 4040, __ATOMIC_SEQ_CST) != 3030)
+        return 1;
+
+    ptmp = &val;
+    if (!__atomic_compare_exchange_n(&mem, &ptmp, &tmp, 0, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
+            || ptmp != &val || mem != &tmp)
         return 1;
 
     return 0;
-}], [ap_cv_atomic_builtins=yes], [ap_cv_atomic_builtins=no], [ap_cv_atomic_builtins=no])])
+}], [ap_cv__atomic_builtins=yes], [ap_cv__atomic_builtins=no], [ap_cv__atomic_builtins=no])])
 
-if test "$ap_cv_atomic_builtins" = "yes"; then
+if test "$ap_cv_atomic_builtins" = "yes" -o "$ap_cv__atomic_builtins" = "yes"; then
     AC_DEFINE(HAVE_ATOMIC_BUILTINS, 1, [Define if compiler provides atomic builtins])
+    if test "$ap_cv__atomic_builtins" = "yes"; then
+        AC_DEFINE(HAVE__ATOMIC_BUILTINS, 1, [Define if compiler provides __atomic builtins])
+    fi
 fi
 
 AC_CACHE_CHECK([whether the compiler handles weak symbols], [ap_cv_weak_symbols],