--- ./src/include/port/atomics/arch-ppc.h.ORIGIN	2018-02-27 18:25:50 -0600
+++ ./src/include/port/atomics/arch-ppc.h	2018-02-27 18:31:25 -0600
@@ -13,7 +13,15 @@
  *-------------------------------------------------------------------------
  */
 
-#if defined(__GNUC__)
+// On AIX & with XLC, without the patch "|| defined(__xlc__)",
+//   pg_memory_barrier_impl is defined in port/atomics/fallback.h as:
+//		#define pg_memory_barrier_impl pg_spinlock_barrier
+//   where pg_spinlock_barrier issues a kill(0) to effect the barrier.
+// Not so good for performance !!!
+
+//  On AIX & with GCC (__GNUC__), it is OK: the following definitions are used
+
+#if defined(__GNUC__) || defined(__xlc__)
 
 /*
  * lwsync orders loads with respect to each other, and similarly with stores.