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Annotation of sys/lib/libkern/arch/mips64/bzero.S, Revision 1.1

1.1     ! nbrk        1: /*     $OpenBSD: bzero.S,v 1.6 2004/10/08 14:42:09 pefo Exp $  */
        !             2: /*-
        !             3:  * Copyright (c) 1991, 1993
        !             4:  *      The Regents of the University of California.  All rights reserved.
        !             5:  *
        !             6:  * This code is derived from software contributed to Berkeley by
        !             7:  * Ralph Campbell.
        !             8:  *
        !             9:  * Redistribution and use in source and binary forms, with or without
        !            10:  * modification, are permitted provided that the following conditions
        !            11:  * are met:
        !            12:  * 1. Redistributions of source code must retain the above copyright
        !            13:  *    notice, this list of conditions and the following disclaimer.
        !            14:  * 2. Redistributions in binary form must reproduce the above copyright
        !            15:  *    notice, this list of conditions and the following disclaimer in the
        !            16:  *    documentation and/or other materials provided with the distribution.
        !            17:  * 3. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  */
        !            33:
        !            34:
        !            35: #include "DEFS.h"
        !            36:
        !            37: /*
        !            38:  * bzero(void *p, size_t len)
        !            39:  */
        !            40: LEAF(bzero, 0)
        !            41: ALEAF(blkclr)
        !            42:        .set    noreorder
        !            43: #ifdef _STANDALONE
        !            44:        blt     a1, 12, smallclr        # small amount to clear?
        !            45:        PTR_SUBU a3, zero, a0           # compute # bytes to word align address
        !            46:        and     a3, a3, 3
        !            47:        beq     a3, zero, 1f            # skip if word aligned
        !            48:        PTR_SUBU a1, a1, a3             # subtract from remaining count
        !            49:        SWHI    zero, 0(a0)             # clear 1, 2, or 3 bytes to align
        !            50:        PTR_ADDU a0, a0, a3
        !            51: 1:
        !            52:        and     v0, a1, 3               # compute number of words left
        !            53:        PTR_SUBU a3, a1, v0
        !            54:        move    a1, v0
        !            55:        PTR_ADDU a3, a3, a0             # compute ending address
        !            56: 2:
        !            57:        PTR_ADDU a0, a0, 4              # clear words
        !            58:        bne     a0, a3, 2b              #  unrolling loop does not help
        !            59:        sw      zero, -4(a0)            #  since we are limited by memory speed
        !            60: #else
        !            61:        blt     a1, 24, smallclr        # small amount to clear?
        !            62:        PTR_SUBU a3, zero, a0           # compute # bytes to word align address
        !            63:        and     a3, a3, 7
        !            64:        beq     a3, zero, 1f            # skip if word aligned
        !            65:        PTR_SUBU a1, a1, a3             # subtract from remaining count
        !            66:        SDHI    zero, 0(a0)             # clear 1, 2, or 3 bytes to align
        !            67:        PTR_ADDU a0, a0, a3
        !            68: 1:
        !            69:        and     v0, a1, 7               # compute number of words left
        !            70:        PTR_SUBU a3, a1, v0
        !            71:        move    a1, v0
        !            72:        PTR_ADDU a3, a3, a0             # compute ending address
        !            73: 2:
        !            74:        PTR_ADDU a0, a0, 8              # clear words
        !            75:        bne     a0, a3, 2b              #  unrolling loop does not help
        !            76:        sd      zero, -8(a0)            #  since we are limited by memory speed
        !            77: #endif
        !            78: smallclr:
        !            79:        ble     a1, zero, 2f
        !            80:        PTR_ADDU a3, a1, a0             # compute ending address
        !            81: 1:
        !            82:        PTR_ADDU a0, a0, 1              # clear bytes
        !            83:        bne     a0, a3, 1b
        !            84:        sb      zero, -1(a0)
        !            85: 2:
        !            86:        j       ra
        !            87:        nop
        !            88: END(bzero)