/*      $OpenBSD: bcopy.S,v 1.5 2015/08/31 02:53:56 guenther 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 "SYS.h"

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


LEAF(bcopy, 0)
        .set    noreorder
        daddu   t0, a0, a2              # t0 = end of s1 region
        sltu    t1, a1, t0
        sltu    t2, a0, a1
        and     t1, t1, t2              # t1 = true if from < to < (from+len)
        beq     t1, zero, forward       # non overlapping, do forward copy
        slt     t2, a2, 12              # check for small copy

        ble     a2, zero, 2f
        daddu   t1, a1, a2              # t1 = end of to region
1:
        lb      v0, -1(t0)              # copy bytes backwards,
        dsubu   t0, t0, 1               #  does not happen often so do slow way
        dsubu   t1, t1, 1
        bne     t0, a0, 1b
        sb      v0, 0(t1)
2:
        j       ra
        nop
forward:
        bne     t2, zero, smallcpy      # do a small bcopy
        xor     v0, a0, a1              # compare low two bits of addresses
        and     v0, v0, 3
        dsubu   a3, zero, a1            # compute # bytes to word align address
        beq     v0, zero, aligned       # addresses can be word aligned
        and     a3, a3, 3

        beq     a3, zero, 1f
        dsubu   a2, a2, a3              # subtract from remaining count
        LWHI    v0, 0(a0)               # get next 4 bytes (unaligned)
        LWLO    v0, 3(a0)
        daddu   a0, a0, a3
        SWHI    v0, 0(a1)               # store 1, 2, or 3 bytes to align a1
        daddu   a1, a1, a3
1:
        and     v0, a2, 3               # compute number of words left
        dsubu   a3, a2, v0
        move    a2, v0
        daddu   a3, a3, a0              # compute ending address
2:
        LWHI    v0, 0(a0)               # copy words a0 unaligned, a1 aligned
        LWLO    v0, 3(a0)
        daddu   a0, a0, 4
        daddu   a1, a1, 4
        bne     a0, a3, 2b
        sw      v0, -4(a1)
        b       smallcpy
        nop
aligned:
        beq     a3, zero, 1f
        dsubu   a2, a2, a3              # subtract from remaining count
        LWHI    v0, 0(a0)               # copy 1, 2, or 3 bytes to align
        daddu   a0, a0, a3
        SWHI    v0, 0(a1)
        daddu   a1, a1, a3
1:
        and     v0, a2, 3               # compute number of whole words left
        dsubu   a3, a2, v0
        move    a2, v0
        daddu   a3, a3, a0              # compute ending address
2:
        lw      v0, 0(a0)               # copy words
        daddu   a0, a0, 4
        daddu   a1, a1, 4
        bne     a0, a3, 2b
        sw      v0, -4(a1)
smallcpy:
        ble     a2, zero, 2f
        daddu   a3, a2, a0              # compute ending address
1:
        lbu     v0, 0(a0)               # copy bytes
        daddu   a0, a0, 1
        daddu   a1, a1, 1
        bne     a0, a3, 1b
        sb      v0, -1(a1)
2:
        j       ra
        nop
        .set    reorder
END_WEAK(bcopy)