[src/trunk]: src/common/lib/libc/arch/arm/gen Add some comments to illustrate...

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

details:   https://anonhg.NetBSD.org/src/rev/d705a55f2fbc
branches:  trunk
changeset: 784061:d705a55f2fbc
user:      matt <matt%NetBSD.org@localhost>
date:      Wed Jan 16 21:48:56 2013 +0000

description:
Add some comments to illustrate what is actually happening.

diffstat:

 common/lib/libc/arch/arm/gen/byte_swap_4.S |  12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diffs (26 lines):

diff -r 9761155f823f -r d705a55f2fbc common/lib/libc/arch/arm/gen/byte_swap_4.S
--- a/common/lib/libc/arch/arm/gen/byte_swap_4.S        Wed Jan 16 21:11:05 2013 +0000
+++ b/common/lib/libc/arch/arm/gen/byte_swap_4.S        Wed Jan 16 21:48:56 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: byte_swap_4.S,v 1.5 2012/11/27 23:57:07 matt Exp $     */
+/*     $NetBSD: byte_swap_4.S,v 1.6 2013/01/16 21:48:56 matt Exp $     */
 
 /*-
  * Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -42,11 +42,11 @@
 #endif
 _PROF_PROLOGUE
 #ifdef _ARM_ARCH_6
-       rev             r0, r0
+       rev     r0, r0
 #else
-       eor             r1, r0, r0, ror #16
-       bic             r1, r1, #0x00FF0000
-       mov             r0, r0, ror #8
-       eor             r0, r0, r1, lsr #8
+       eor     r1, r0, r0, ror #16     /* 4.3.2.1 -> 42.31.42.31 */
+       bic     r1, r1, #0x00FF0000     /* 42.31.42.31 -> 42.0.42.31 */
+       mov     r0, r0, ror #8          /* 4.3.2.1 -> 1.4.3.2 */
+       eor     r0, r0, r1, lsr #8      /* 1.4.3.2 ^ 0.42.0.42 -> 1.2.3.4 */
 #endif
        RET