/*      $NetBSD: bcmp.S,v 1.9 2009/12/14 01:07:42 matt Exp $    */

/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Ralph Campbell.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <mips/asm.h>
#define _LOCORE         /* XXX not really, just assembly-code source */
#include <machine/endian.h>     /* LWLO/LWHI, SWLO/SWHI */

#if defined(LIBC_SCCS) && !defined(lint)
#if 0
        RCSID("from: @(#)bcmp.s 8.1 (Berkeley) 6/4/93")
#else
        RCSID("$NetBSD: bcmp.S,v 1.9 2009/12/14 01:07:42 matt Exp $")
#endif
#endif /* LIBC_SCCS and not lint */

/* bcmp(s1, s2, n) */


LEAF(bcmp)
        .set    noreorder
        blt             a2, 16, small   # is it worth any trouble?
        xor             v0, a0, a1      # compare low two bits of addresses
        and             v0, v0, 3
        PTR_SUBU        a3, zero, a1    # compute # bytes to word align address
        bne             v0, zero, unaligned # not possible to align addresses
        and             a3, a3, 3

        beq             a3, zero, 1f
        PTR_SUBU        a2, a2, a3      # subtract from remaining count
        move            v0, v1          # init v0,v1 so unmodified bytes match
        LWHI            v0, 0(a0)       # read 1, 2, or 3 bytes
        LWHI            v1, 0(a1)
        PTR_ADDU        a1, a1, a3
        bne             v0, v1, nomatch
        PTR_ADDU        a0, a0, a3
1:
        and             a3, a2, ~3      # compute number of whole words left
        PTR_SUBU        a2, a2, a3      #   which has to be >= (16-3) & ~3
        PTR_ADDU        a3, a3, a0      # compute ending address
2:
        lw              v0, 0(a0)       # compare words
        lw              v1, 0(a1)
        PTR_ADDU        a0, a0, 4
        bne             v0, v1, nomatch
        PTR_ADDU        a1, a1, 4
        bne             a0, a3, 2b
        nop
        b               small           # finish remainder
        nop
unaligned:
        beq             a3, zero, 2f
        PTR_SUBU        a2, a2, a3      # subtract from remaining count
        PTR_ADDU        a3, a3, a0      # compute ending address
1:
        lbu             v0, 0(a0)       # compare bytes until a1 word aligned
        lbu             v1, 0(a1)
        PTR_ADDU        a0, a0, 1
        bne             v0, v1, nomatch
        PTR_ADDU        a1, a1, 1
        bne             a0, a3, 1b
        nop
2:
        and             a3, a2, ~3      # compute number of whole words left
        PTR_SUBU        a2, a2, a3      #   which has to be >= (16-3) & ~3
        PTR_ADDU        a3, a3, a0      # compute ending address
3:
        LWHI            v0, 0(a0)       # compare words a0 unaligned, a1 aligned
        LWLO            v0, 3(a0)
        lw              v1, 0(a1)
        PTR_ADDU        a0, a0, 4
        bne             v0, v1, nomatch
        PTR_ADDU        a1, a1, 4
        bne             a0, a3, 3b
        nop
small:
        ble             a2, zero, match
        PTR_ADDU        a3, a2, a0              # compute ending address
1:
        lbu             v0, 0(a0)
        lbu             v1, 0(a1)
        PTR_ADDU        a0, a0, 1
        bne             v0, v1, nomatch
        PTR_ADDU        a1, a1, 1
        bne             a0, a3, 1b
        nop
match:
        j               ra
        move            v0, zero
nomatch:
        j               ra
        li              v0, 1
        .set    reorder
END(bcmp)