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Annotation of sys/lib/libkern/arch/alpha/byte_swap_4.S, Revision 1.1

1.1     ! nbrk        1: /*     $OpenBSD: byte_swap_4.S,v 1.2 1996/10/31 00:43:15 niklas Exp $  */
        !             2: /*     $NetBSD: byte_swap_4.S,v 1.2 1996/10/17 04:26:22 cgd Exp $      */
        !             3:
        !             4: /*
        !             5:  * Copyright (c) 1996 Carnegie-Mellon University.
        !             6:  * All rights reserved.
        !             7:  *
        !             8:  * Author: Chris G. Demetriou
        !             9:  *
        !            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.
        !            15:  *
        !            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.
        !            19:  *
        !            20:  * Carnegie Mellon requests users of this software to return to
        !            21:  *
        !            22:  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
        !            23:  *  School of Computer Science
        !            24:  *  Carnegie Mellon University
        !            25:  *  Pittsburgh PA 15213-3890
        !            26:  *
        !            27:  * any improvements or extensions that they make and grant Carnegie the
        !            28:  * rights to redistribute these changes.
        !            29:  */
        !            30:
        !            31: #include <machine/asm.h>
        !            32:
        !            33: #ifndef NAME
        !            34: #define        NAME byte_swap_4
        !            35: #endif
        !            36:
        !            37: /*
        !            38:  * Byte-swap a 4-byte quantity.  (Convert 0x01234567 to 0x67452301.)
        !            39:  *
        !            40:  * Argument is an unsigned 4-byte integer (u_int32_t).
        !            41:  */
        !            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 */
        !            53:        RET
        !            54: END(NAME)