--- gcc/config/xm-rs6000.h	2018/04/24 17:51:31	1.1.1.1
+++ gcc/config/xm-rs6000.h	2018/04/24 17:58:28	1.1.1.2
@@ -53,5 +53,11 @@ the Free Software Foundation, 675 Mass A
 #define	ONLY_INT_FIELDS
 #endif
 
-
+/* AIX is a flavor of System V */
 #define	USG
+
+/* This is the only version of nm that collect2 can work with.  */
+#define REAL_NM_FILE_NAME "/usr/ucb/nm"
+
+/* Big buffers improve performance.  */
+#define IO_BUFFER_SIZE (0x8000 - 4096)