optabs.c (expand_atomic_load): Do not assume compare_and_swap will succeed for…

optabs.c (expand_atomic_load): Do not assume compare_and_swap will succeed for larger than word integers.


	* optabs.c (expand_atomic_load): Do not assume compare_and_swap will
	succeed for larger than word integers.

From-SVN: r184009

gcc/ChangeLog

+2012-02-08  Andrew MacLeod  <amacleod@redhat.com>
+
+	* optabs.c (expand_atomic_load): Do not assume compare_and_swap will
+	always succeed for integers larger than a native word.
+
 2012-02-08  Richard Guenther  <rguenther@suse.de>
 
 	PR rtl-optimization/52170

gcc/optabs.c

@@ -7665,9 +7665,12 @@ expand_atomic_load (rtx target, rtx mem, enum memmodel model)
       /* Issue val = compare_and_swap (mem, 0, 0).
 	 This may cause the occasional harmless store of 0 when the value is
 	 already 0, but it seems to be OK according to the standards guys.  */
-      expand_atomic_compare_and_swap (NULL, &target, mem, const0_rtx,
-				      const0_rtx, false, model, model);
-      return target;
+      if (expand_atomic_compare_and_swap (NULL, &target, mem, const0_rtx,
+					  const0_rtx, false, model, model))
+	return target;
+      else
+      /* Otherwise there is no atomic load, leave the library call.  */
+        return NULL_RTX;
     }
 
   /* Otherwise assume loads are atomic, and emit the proper barriers.  */