bcmp.s

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    1 /*
    2  * Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
    3  *
    4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
    5  * 
    6  * This file contains Original Code and/or Modifications of Original Code
    7  * as defined in and that are subject to the Apple Public Source License
    8  * Version 2.0 (the 'License'). You may not use this file except in
    9  * compliance with the License. The rights granted to you under the License
   10  * may not be used to create, or enable the creation or redistribution of,
   11  * unlawful or unlicensed copies of an Apple operating system, or to
   12  * circumvent, violate, or enable the circumvention or violation of, any
   13  * terms of an Apple operating system software license agreement.
   14  * 
   15  * Please obtain a copy of the License at
   16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
   17  * 
   18  * The Original Code and all software distributed under the License are
   19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
   20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
   21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
   22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
   23  * Please see the License for the specific language governing rights and
   24  * limitations under the License.
   25  * 
   26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
   27  */
   28 ;
   29 #include <ppc/asm.h>
   30 #include <ppc/proc_reg.h>
   31 ;
   32 ; int   bcmp(const void *LHS, const void *RHS, size_t len);
   33 ;
   34 ; Because bcmp returns zero if equal and nonzero otherwise, it is slightly
   35 ; faster than memcmp, which returns the difference between the first different
   36 ; bytes.
   37 ;       r3 - LHS
   38 ;       r4 - RHS
   39 ;       r5 - len
   40 
   41         .align  5
   42         .globl  EXT(bcmp)
   43 LEXT(bcmp)
   44 
   45         cmpwi   cr1,r5,6                ; six chars long?
   46         mr      r6,r3                   ; copy LHS ptr so we can use r3 as result
   47         mr.     r3,r5                   ; test length and move to r3
   48         bgt     cr1,Llong               ; more than 6 chars long
   49         blt     cr1,Lshort              ; less than 6
   50 
   51         ; most common operand length is 6 chars (enet addrs)
   52 
   53         lwz     r8,0(r6)                ; first 4 bytes of LHS
   54         lwz     r7,0(r4)                ; and RHS
   55         lhz     r9,4(r6)                ; next 2 of LHS
   56         sub.    r3,r8,r7                ; compare first 4
   57         bnelr                           ; first 4 differed (r3!=0)
   58         lhz     r10,4(r4)               ; next 2 of RHS
   59         sub     r3,r9,r10               ; compare last 2
   60         blr                             ; done, result in r3
   61 
   62         ; handle long strings
   63 Llong:
   64         srwi    r0,r5,2                 ; r0 = word len
   65         mtctr   r0                      ; set up for loop
   66 Llongloop:
   67         lwz     r8,0(r6)                ; next 4 bytes from LHS
   68         addi    r6,r6,4
   69         lwz     r7,0(r4)                ; next 4 from RHS
   70         addi    r4,r4,4
   71         sub.    r3,r8,r7                ; compare next 4 bytes
   72         bdnzt+  eq,Llongloop            ; loop if ctr!=0 and cr0_eq
   73         bnelr                           ; done if not equal (r3!=0)
   74 
   75         andi.   r5,r5,3                 ; more to go?
   76 
   77         ; compare short strings (0-5 bytes long)
   78         ;       r5 = length remaining
   79         ;       cr0= set on length
   80         ;       r3 = zero if length is zero
   81 Lshort:
   82         beqlr                           ; done (r3=0)
   83         mtctr   r5
   84 Lshortloop:
   85         lbz     r8,0(r6)                ; get next byte from LHS
   86         addi    r6,r6,1
   87         lbz     r7,0(r4)                ; and next byte from RHS
   88         addi    r4,r4,1
   89         sub.    r3,r8,r7                ; compare
   90         bdnzt+  eq,Lshortloop           ; loop if ctr!=0 and cr0_eq
   91         blr                             ; done, r3 set correctly by the subtract
   92

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FreeBSD/Linux Kernel Cross Reference sys/libkern/ppc/bcmp.s

FreeBSD/Linux Kernel Cross Reference
sys/libkern/ppc/bcmp.s