[src/trunk]: src/sys/arch/sparc/dev document arithmetics instructions

[macallan <macallan%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/cf306b767a7f
branches:  trunk
changeset: 787362:cf306b767a7f
user:      macallan <macallan%NetBSD.org@localhost>
date:      Wed Jun 12 20:43:21 2013 +0000

description:
document arithmetics instructions

diffstat:

 sys/arch/sparc/dev/sxreg.h |  19 ++++++++++---------
 1 files changed, 10 insertions(+), 9 deletions(-)

diffs (33 lines):

diff -r 2effbe1fdc96 -r cf306b767a7f sys/arch/sparc/dev/sxreg.h
--- a/sys/arch/sparc/dev/sxreg.h        Wed Jun 12 20:36:53 2013 +0000
+++ b/sys/arch/sparc/dev/sxreg.h        Wed Jun 12 20:43:21 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sxreg.h,v 1.8 2013/06/12 04:23:46 macallan Exp $       */
+/*     $NetBSD: sxreg.h,v 1.9 2013/06/12 20:43:21 macallan Exp $       */
 
 /*-
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -253,14 +253,15 @@
                ((sa) << 14) | ((d) << 7) | (sb))
 
 /* arithmetic group */
-#define SX_ADD_V       (0x00 << 21)
-#define SX_ADD_S       (0x01 << 21)
-#define SX_ADD_I       (0x02 << 21)
-#define SX_SUM         (0x03 << 21)
-#define SX_SUB_V       (0x04 << 21)
-#define SX_SUB_S       (0x05 << 21)
-#define SX_SUB_I       (0x06 << 21)
-#define SX_ABS         (0x07 << 21)
+#define SX_ADD_V       (0x00 << 21)    /* vector + vector */
+#define SX_ADD_S       (0x01 << 21)    /* vector + scalar */
+#define SX_ADD_I       (0x02 << 21)    /* vector + immediate */
+#define SX_SUM         (0x03 << 21)    /* sum of vector and scalar */
+#define SX_SUB_V       (0x04 << 21)    /* vector - veector */
+#define SX_SUB_S       (0x05 << 21)    /* vector - scalar */
+#define SX_SUB_I       (0x06 << 21)    /* vector - immediate */
+#define SX_ABS         (0x07 << 21)    /* abs(sb) with sa=R0 */
+/* hardware does sa - sb for sb < 0 and sa + sb if sb > 0 */
 
 #define SX_ADDV(sa, sb, d, cnt) (0xa0000000 | ((cnt) << 24) | SX_ADD_V | \
                ((sa) << 14) | ((d) << 7) | (sb))