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Annotation of sys/lib/libkern/arch/m68k/memcmp.S, Revision 1.1

1.1     ! nbrk        1: /*     $OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $      */
        !             2:
        !             3: /*-
        !             4:  * Copyright (c) 1990 The Regents of the University of California.
        !             5:  * All rights reserved.
        !             6:  *
        !             7:  * This code is derived from software contributed to Berkeley by
        !             8:  * the Systems Programming Group of the University of Utah Computer
        !             9:  * Science Department.
        !            10:  *
        !            11:  * Redistribution and use in source and binary forms, with or without
        !            12:  * modification, are permitted provided that the following conditions
        !            13:  * are met:
        !            14:  * 1. Redistributions of source code must retain the above copyright
        !            15:  *    notice, this list of conditions and the following disclaimer.
        !            16:  * 2. Redistributions in binary form must reproduce the above copyright
        !            17:  *    notice, this list of conditions and the following disclaimer in the
        !            18:  *    documentation and/or other materials provided with the distribution.
        !            19:  * 3. Neither the name of the University nor the names of its contributors
        !            20:  *    may be used to endorse or promote products derived from this software
        !            21:  *    without specific prior written permission.
        !            22:  *
        !            23:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            24:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            25:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            26:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            27:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            28:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            29:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            30:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            31:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            32:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            33:  * SUCH DAMAGE.
        !            34:  */
        !            35:
        !            36: #include "DEFS.h"
        !            37:
        !            38: #if defined(LIBC_SCCS)
        !            39:        .text
        !            40:        .asciz "$OpenBSD: memcmp.S,v 1.2 2003/06/02 23:28:08 millert Exp $"
        !            41: #endif /* LIBC_SCCS */
        !            42:
        !            43: /* memcmp(s1, s2, n) */
        !            44:
        !            45: /*
        !            46:  * This is probably not the best we can do, but it is still 2-10 times
        !            47:  * faster than the C version in the portable gen directory.
        !            48:  *
        !            49:  * Things that might help:
        !            50:  *     - longword align when possible (only on the 68020)
        !            51:  *     - use nested DBcc instructions or use one and limit size to 64K
        !            52:  */
        !            53: ENTRY(memcmp)
        !            54:        movl    sp@(4),a0               | string 1
        !            55:        movl    sp@(8),a1               | string 2
        !            56:        movl    sp@(12),d0              | length
        !            57:        beq     bcdone                  | if zero, nothing to do
        !            58:        movl    a0,d1
        !            59:        btst    #0,d1                   | string 1 address odd?
        !            60:        beq     bceven                  | no, skip alignment
        !            61:        cmpmb   a0@+,a1@+               | yes, compare a byte
        !            62:        bne     bcnoteq                 | not equal, return non-zero
        !            63:        subql   #1,d0                   | adjust count
        !            64:        beq     bcdone                  | count 0, reutrn zero
        !            65: bceven:
        !            66:        movl    a1,d1
        !            67:        btst    #0,d1                   | string 2 address odd?
        !            68:        bne     bcbloop                 | yes, no hope for alignment, compare bytes
        !            69:        movl    d0,d1                   | no, both even
        !            70:        lsrl    #2,d1                   | convert count to longword count
        !            71:        beq     bcbloop                 | count 0, skip longword loop
        !            72: bclloop:
        !            73:        cmpml   a0@+,a1@+               | compare a longword
        !            74:        bne     bcnoteql                | not equal, return non-zero
        !            75:        subql   #1,d1                   | adjust count
        !            76:        bne     bclloop                 | still more, keep comparing
        !            77:        andl    #3,d0                   | what remains
        !            78:        beq     bcdone                  | nothing, all done
        !            79: bcbloop:
        !            80:        cmpmb   a0@+,a1@+               | compare a byte
        !            81:        bne     bcnoteq                 | not equal, return non-zero
        !            82:        subql   #1,d0                   | adjust count
        !            83:        bne     bcbloop                 | still more, keep going
        !            84:        rts
        !            85: bcnoteql:
        !            86:        subql   #4,a0
        !            87:        subql   #4,a1
        !            88:        movl    #4,d0
        !            89:        jra     bcbloop
        !            90: bcnoteq:
        !            91:        clrl    d0
        !            92:        clrl    d1
        !            93:        movb    a0@-,d0
        !            94:        movb    a1@-,d1
        !            95:        subl    d1,d0
        !            96: bcdone:
        !            97:        rts