1 /* $FreeBSD: src/sys/libkern/alpha/byte_swap_4.S,v 1.1.6.1 2000/08/03 01:03:45 peter Exp $ */
2 /* $NetBSD: byte_swap_4.S,v 1.2 1996/10/17 03:08:09 cgd Exp $ */
5 * Copyright (c) 1996 Carnegie-Mellon University.
8 * Author: Chris G. Demetriou
10 * Permission to use, copy, modify and distribute this software and
11 * its documentation is hereby granted, provided that both the copyright
12 * notice and this permission notice appear in all copies of the
13 * software, derivative works or modified versions, and any portions
14 * thereof, and that both notices appear in supporting documentation.
16 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
17 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
18 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
20 * Carnegie Mellon requests users of this software to return to
22 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
23 * School of Computer Science
24 * Carnegie Mellon University
25 * Pittsburgh PA 15213-3890
27 * any improvements or extensions that they make and grant Carnegie the
28 * rights to redistribute these changes.
31 #include <machine/asm.h>
34 #define NAME byte_swap_4
38 * Byte-swap a 4-byte quantity. (Convert 0x01234567 to 0x67452301.)
40 * Argument is an unsigned 4-byte integer (u_int32_t).
42 LEAF(NAME, 1) /* a0 contains 0x01234567 */
43 extbl a0, 0, t0 /* t0 = 0x 67 */
44 extbl a0, 1, t1 /* t1 = 0x 45 */
45 extbl a0, 2, t2 /* t2 = 0x 23 */
46 extbl a0, 3, t3 /* t3 = 0x 01 */
47 sll t0, 24, t0 /* t0 = 0x67 */
48 sll t1, 16, t1 /* t1 = 0x 45 */
49 sll t2, 8, t2 /* t2 = 0x 23 */
50 or t3, t0, v0 /* v0 = 0x67 01 */
51 or t1, t2, t1 /* t1 = 0x 4523 */
52 or t1, v0, v0 /* v0 = 0x67452301 */