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byte_swap_4.S revision 1.1 
      1 /* $NetBSD: byte_swap_4.S,v 1.1 2005/12/20 19:28:49 christos Exp $ */
      2 
      3 /*
      4  * Copyright (c) 1996 Carnegie-Mellon University.
      5  * All rights reserved.
      6  *
      7  * Author: Chris G. Demetriou
      8  *
      9  * Permission to use, copy, modify and distribute this software and
     10  * its documentation is hereby granted, provided that both the copyright
     11  * notice and this permission notice appear in all copies of the
     12  * software, derivative works or modified versions, and any portions
     13  * thereof, and that both notices appear in supporting documentation.
     14  *
     15  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     16  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     17  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     18  *
     19  * Carnegie Mellon requests users of this software to return to
     20  *
     21  *  Software Distribution Coordinator  or  Software.Distribution (at) CS.CMU.EDU
     22  *  School of Computer Science
     23  *  Carnegie Mellon University
     24  *  Pittsburgh PA 15213-3890
     25  *
     26  * any improvements or extensions that they make and grant Carnegie the
     27  * rights to redistribute these changes.
     28  */
     29 
     30 #include <machine/asm.h>
     31 
     32 /*
     33  * Byte-swap a 4-byte quantity.  (Convert 0x01234567 to 0x67452301.)
     34  *
     35  * Argument is an unsigned 4-byte integer (u_int32_t).
     36  */
     37 LEAF(__bswap32, 1)		/* a0 contains 0x01234567 */
     38 XLEAF(htonl, 1)
     39 XLEAF(ntohl, 1)
     40 	insbl	a0, 3, t0	/* t0 = 0x67       */
     41 	extbl	a0, 1, t1	/* t1 = 0x      45 */
     42 	extbl	a0, 2, t2	/* t2 = 0x      23 */
     43 	extbl	a0, 3, t3	/* t3 = 0x      01 */
     44 	sll	t1, 16, t1	/* t1 = 0x  45     */
     45 	sll	t2, 8, t2	/* t2 = 0x    23   */
     46 	or	t3, t0, v0	/* v0 = 0x67    01 */
     47 	or	t1, t2, t1	/* t1 = 0x  4523   */
     48 	or	t1, v0, v0	/* v0 = 0x67452301 */
     49 	RET
     50 END(__bswap32)
     51