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Annotation of kernel/machdep/ppc/libc/bcmp.s, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
        !            26:  *
        !            27:  *      File:  machdep/ppc/libc/bcmp.s
        !            28:  *
        !            29:  *     int bcmp(const void *b1, const void *b2, size_t len)
        !            30:  *
        !            31:  *     DESCRIPTION
        !            32:  *             The bcmp() function compares byte string b1 against byte string
        !            33:  *             b2, returning zero if they are identical, non-zero otherwise.
        !            34:  *             Both strings are assumed to be len bytes long.
        !            35:  *             Zero-length strings are always identical.
        !            36:  *
        !            37:  *             The strings may overlap.
        !            38:  *
        !            39:  * HISTORY
        !            40:  *     23-Sep-1998     Umesh Vaishampayan      ([email protected])
        !            41:  *             Created.
        !            42:  */
        !            43: 
        !            44: .text
        !            45: .align 4
        !            46: .globl _bcmp
        !            47: _bcmp:
        !            48: /* Optimized the 6 byte case to improve the networking performance */
        !            49:        cmpwi   r5, 6
        !            50:        bne-    L_not_six
        !            51:        lwz     r6, 0(r3)
        !            52:        lwz     r7, 0(r4)
        !            53:        lhz     r8, 4(r3)
        !            54:        xor     r10, r6, r7
        !            55:        lhz     r9, 4(r4)
        !            56:        xor     r11, r8, r9
        !            57:        or      r3, r10, r11
        !            58:        blr
        !            59:        nop                                             ; To align L_not_six on 4 word boundary
        !            60:        nop                                             ; To align L_not_six on 4 word boundary
        !            61: 
        !            62: L_not_six:
        !            63:        mr.     r5,r5
        !            64:        beq-    L_len_zero
        !            65: L_len_not_zero:
        !            66:        lbz     r0,0(r3)
        !            67:        lbz     r9,0(r4)
        !            68:        addi    r4,r4,1
        !            69:        cmpw    cr1,r0,r9
        !            70:        bne-    cr1,L_done
        !            71:        subi    r5, r5, 1               ; addic.  r5,r5,-1 touches xer
        !            72:        addi    r3,r3,1
        !            73:        mr.             r5, r5
        !            74:        bne     L_len_not_zero
        !            75: L_done:
        !            76:        mr      r3,r5
        !            77:        blr
        !            78: 
        !            79: L_len_zero:
        !            80:        li      r3,0                    ; Zero-length strings are always identical.
        !            81:        blr

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