--- gcc/config/rs6000/mach.h	2018/04/24 18:10:26	1.1.1.1
+++ gcc/config/rs6000/mach.h	2018/04/24 18:16:36	1.1.1.2
@@ -24,7 +24,7 @@ the Free Software Foundation, 675 Mass A
 
 /* We don't define AIX under MACH; instead we define `unix'.  */
 #undef CPP_PREDEFINES
-#define CPP_PREDEFINES "-Drios -D_IBMR2 -Dunix"
+#define CPP_PREDEFINES "-Drios -D_IBMR2 -Dunix -Asystem(unix) -Asystem(mach) -Acpu(rs6000) -Amachine(rs6000)"
 
 /* Define different binder options for MACH.  */
 #undef LINK_SPEC