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   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2010 by Spencer Oliver                                  *
   5  *   spen@spen-soft.co.uk                                                  *
   6  ***************************************************************************/
   7
   8 /*
   9         parameters:
  10         r0 - address in - crc out
  11         r1 - char count
  12 */
  13
  14         .text
  15         .syntax unified
  16         .cpu cortex-m0
  17         .thumb
  18         .thumb_func
  19
  20         .align  2
  21
  22 _start:
  23 main:
  24         mov             r2, r0
  25         movs    r0, #0
  26         mvns    r0, r0
  27         ldr             r6, CRC32XOR
  28         mov             r3, r1
  29         movs    r4, #0
  30         b               ncomp
  31 nbyte:
  32         ldrb    r1, [r2, r4]
  33         lsls    r1, r1, #24
  34         eors    r0, r0, r1
  35         movs    r5, #0
  36 loop:
  37         cmp             r0, #0
  38         bge             notset
  39         lsls    r0, r0, #1
  40         eors    r0, r0, r6
  41         b               cont
  42 notset:
  43         lsls    r0, r0, #1
  44 cont:
  45         adds    r5, r5, #1
  46         cmp             r5, #8
  47         bne             loop
  48         adds    r4, r4, #1
  49 ncomp:
  50         cmp             r4, r3
  51         bne             nbyte
  52         bkpt    #0
  53
  54         .align  2
  55
  56 CRC32XOR:       .word   0x04c11db7
  57
  58         .end