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

1.1     ! nbrk        1: /*     $OpenBSD: bcmp.S,v 1.4 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: #include "DEFS.h"
        !            35:
        !            36:
        !            37: /*
        !            38:  * bcmp(s1, s2, n)
        !            39:  */
        !            40: LEAF(bcmp, 0)
        !            41:        .set    noreorder
        !            42:        blt     a2, 16, smallcmp        # is it worth any trouble?
        !            43:        xor     v0, a0, a1              # compare low two bits of addresses
        !            44:        and     v0, v0, 3
        !            45:        PTR_SUBU a3, zero, a1           # compute # bytes to word align address
        !            46:        bne     v0, zero, unalignedcmp  # not possible to align addresses
        !            47:        and     a3, a3, 3
        !            48:
        !            49:        beq     a3, zero, 1f
        !            50:        PTR_SUBU a2, a2, a3             # subtract from remaining count
        !            51:        move    v0, v1                  # init v0,v1 so unmodified bytes match
        !            52:        LWHI    v0, 0(a0)               # read 1, 2, or 3 bytes
        !            53:        LWHI    v1, 0(a1)
        !            54:        PTR_ADDU a1, a1, a3
        !            55:        bne     v0, v1, nomatch
        !            56:        PTR_ADDU a0, a0, a3
        !            57: 1:
        !            58:        and     a3, a2, ~3              # compute number of whole words left
        !            59:        PTR_SUBU a2, a2, a3             #   which has to be >= (16-3) & ~3
        !            60:        PTR_ADDU a3, a3, a0             # compute ending address
        !            61: 2:
        !            62:        lw      v0, 0(a0)               # compare words
        !            63:        lw      v1, 0(a1)
        !            64:        PTR_ADDU a0, a0, 4
        !            65:        bne     v0, v1, nomatch
        !            66:        PTR_ADDU a1, a1, 4
        !            67:        bne     a0, a3, 2b
        !            68:        nop
        !            69:        b       smallcmp                # finish remainder
        !            70:        nop
        !            71: unalignedcmp:
        !            72:        beq     a3, zero, 2f
        !            73:        PTR_SUBU a2, a2, a3             # subtract from remaining count
        !            74:        PTR_ADDU a3, a3, a0             # compute ending address
        !            75: 1:
        !            76:        lbu     v0, 0(a0)               # compare bytes until a1 word aligned
        !            77:        lbu     v1, 0(a1)
        !            78:        PTR_ADDU a0, a0, 1
        !            79:        bne     v0, v1, nomatch
        !            80:        PTR_ADDU a1, a1, 1
        !            81:        bne     a0, a3, 1b
        !            82:        nop
        !            83: 2:
        !            84:        and     a3, a2, ~3              # compute number of whole words left
        !            85:        PTR_SUBU a2, a2, a3             #   which has to be >= (16-3) & ~3
        !            86:        PTR_ADDU a3, a3, a0             # compute ending address
        !            87: 3:
        !            88:        LWHI    v0, 0(a0)               # compare words a0 unaligned, a1 aligned
        !            89:        LWLO    v0, 3(a0)
        !            90:        lw      v1, 0(a1)
        !            91:        PTR_ADDU a0, a0, 4
        !            92:        bne     v0, v1, nomatch
        !            93:        PTR_ADDU a1, a1, 4
        !            94:        bne     a0, a3, 3b
        !            95:        nop
        !            96: smallcmp:
        !            97:        ble     a2, zero, match
        !            98:        PTR_ADDU a3, a2, a0             # compute ending address
        !            99: 1:
        !           100:        lbu     v0, 0(a0)
        !           101:        lbu     v1, 0(a1)
        !           102:        PTR_ADDU a0, a0, 1
        !           103:        bne     v0, v1, nomatch
        !           104:        PTR_ADDU a1, a1, 1
        !           105:        bne     a0, a3, 1b
        !           106:        nop
        !           107: match:
        !           108:        j       ra
        !           109:        move    v0, zero
        !           110: nomatch:
        !           111:        j       ra
        !           112:        dli     v0, 1
        !           113: END(bcmp)