/*      $OpenBSD: bcmp.S,v 1.5 2022/01/29 05:47:36 visa 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 "DEFS.h"


/*
 * bcmp(s1, s2, n)
 */
LEAF(bcmp, 0)
        .set    noreorder
        blt     a2, 16, .Lsmallcmp      # 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, .Lunalignedcmp # 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, .Lnomatch
        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, .Lnomatch
        PTR_ADDU a1, a1, 4
        bne     a0, a3, 2b
        nop
        b       .Lsmallcmp              # finish remainder
        nop
.Lunalignedcmp:
        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, .Lnomatch
        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, .Lnomatch
        PTR_ADDU a1, a1, 4
        bne     a0, a3, 3b
        nop
.Lsmallcmp:
        ble     a2, zero, .Lmatch
        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, .Lnomatch
        PTR_ADDU a1, a1, 1
        bne     a0, a3, 1b
        nop
.Lmatch:
        j       ra
        move    v0, zero
.Lnomatch:
        j       ra
        dli     v0, 1
END(bcmp)