contrib/loaders/checksum/mips32.s

   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         .global main
   9         .text
  10         .set noreorder
  11
  12 /* params:
  13  * $a0 address in
  14  * $a1 byte count
  15  * vars
  16  * $a0 crc
  17  * $a1 crc data byte
  18  * temps:
  19  * t3 v0 a3 a2 t0 v1
  20  */
  21
  22 .ent main
  23 main:
  24         addiu   $t4, $a0, 0             /* address in */
  25         addiu   $t2, $a1, 0             /* count */
  26
  27         addiu   $a0, $zero, 0xffffffff /* a0 crc - result */
  28
  29         beq             $zero, $zero, ncomp
  30         addiu   $t3, $zero, 0   /* clear bytes read */
  31
  32 nbyte:
  33         lb              $a1, ($t4)              /* load byte from source address */
  34         addi    $t4, $t4, 1             /* inc byte count */
  35
  36 crc:
  37         sll             $a1, $a1, 24
  38         lui             $v0, 0x04c1
  39         xor             $a0, $a0, $a1
  40         ori             $a3, $v0, 0x1db7
  41         addu    $a2, $zero, $zero /* clear bit count */
  42 loop:
  43         sll             $t0, $a0, 1
  44         addiu   $a2, $a2, 1             /* inc bit count */
  45         slti    $a0, $a0, 0
  46         xor             $t1, $t0, $a3
  47         movn    $t0, $t1, $a0
  48         slti    $v1, $a2, 8             /* 8bits processed */
  49         bne             $v1, $zero, loop
  50         addu    $a0, $t0, $zero
  51
  52 ncomp:
  53         bne             $t2, $t3, nbyte /* all bytes processed */
  54         addiu   $t3, $t3, 1
  55
  56 wait:
  57         sdbbp
  58
  59 .end main