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Annotation of sys/lib/libkern/arch/m68k/bcmp.S, Revision 1.1.1.1

1.1       nbrk        1: /*     $OpenBSD: bcmp.S,v 1.3 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: #if defined(LIBC_SCCS) && !defined(lint)
                     37:        .text
                     38:        /*.asciz "from: @(#)bcmp.s      5.1 (Berkeley) 5/12/90"*/
                     39:        .asciz "$OpenBSD: bcmp.S,v 1.3 2003/06/02 23:28:08 millert Exp $"
                     40: #endif /* LIBC_SCCS and not lint */
                     41:
                     42: /* bcmp(s1, s2, n) */
                     43:
                     44: #include "DEFS.h"
                     45:
                     46: /*
                     47:  * This is probably not the best we can do, but it is still 2-10 times
                     48:  * faster than the C version in the portable gen directory.
                     49:  *
                     50:  * Things that might help:
                     51:  *     - longword align when possible (only on the 68020)
                     52:  *     - use nested DBcc instructions or use one and limit size to 64K
                     53:  */
                     54: ENTRY(bcmp)
                     55:        movl    sp@(4),a0               | string 1
                     56:        movl    sp@(8),a1               | string 2
                     57:        movl    sp@(12),d0              | length
                     58:        beq     bcdone                  | if zero, nothing to do
                     59:        movl    a0,d1
                     60:        btst    #0,d1                   | string 1 address odd?
                     61:        beq     bceven                  | no, skip alignment
                     62:        cmpmb   a0@+,a1@+               | yes, compare a byte
                     63:        bne     bcnoteq                 | not equal, return non-zero
                     64:        subql   #1,d0                   | adjust count
                     65:        beq     bcdone                  | count 0, reutrn zero
                     66: bceven:
                     67:        movl    a1,d1
                     68:        btst    #0,d1                   | string 2 address odd?
                     69:        bne     bcbloop                 | yes, no hope for alignment, compare bytes
                     70:        movl    d0,d1                   | no, both even
                     71:        lsrl    #2,d1                   | convert count to longword count
                     72:        beq     bcbloop                 | count 0, skip longword loop
                     73: bclloop:
                     74:        cmpml   a0@+,a1@+               | compare a longword
                     75:        bne     bcnoteq                 | not equal, return non-zero
                     76:        subql   #1,d1                   | adjust count
                     77:        bne     bclloop                 | still more, keep comparing
                     78:        andl    #3,d0                   | what remains
                     79:        beq     bcdone                  | nothing, all done
                     80: bcbloop:
                     81:        cmpmb   a0@+,a1@+               | compare a byte
                     82:        bne     bcnoteq                 | not equal, return non-zero
                     83:        subql   #1,d0                   | adjust count
                     84:        bne     bcbloop                 | still more, keep going
                     85:        rts
                     86: bcnoteq:
                     87:        moveq   #1,d0
                     88: bcdone:
                     89:        rts