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| /* Optimised simple memory checksum
| *
| * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
| * Written by David Howells (dhowells@redhat.com)
| *
| * This program is free software; you can redistribute it and/or
| * modify it under the terms of the GNU General Public Licence
| * as published by the Free Software Foundation; either version
| * 2 of the Licence, or (at your option) any later version.
| */
| #include <asm/cache.h>
|
| .section .text
| .balign L1_CACHE_BYTES
|
| ###############################################################################
| #
| # unsigned int do_csum(const unsigned char *buff, int len)
| #
| ###############################################################################
| .globl do_csum
| .type do_csum,@function
| do_csum:
| movm [d2,d3],(sp)
| mov d1,d2 # count
| mov d0,a0 # buff
| mov a0,a1
| clr d1 # accumulator
|
| cmp +0,d2
| ble do_csum_done # check for zero length or negative
|
| # 4-byte align the buffer pointer
| btst +3,a0
| beq do_csum_now_4b_aligned
|
| btst +1,a0
| beq do_csum_addr_not_odd
| movbu (a0),d0
| inc a0
| asl +8,d0
| add d0,d1
| add -1,d2
|
| do_csum_addr_not_odd:
| cmp +2,d2
| bcs do_csum_fewer_than_4
| btst +2,a0
| beq do_csum_now_4b_aligned
| movhu (a0+),d0
| add d0,d1
| add -2,d2
| cmp +4,d2
| bcs do_csum_fewer_than_4
|
| do_csum_now_4b_aligned:
| # we want to checksum as much as we can in chunks of 32 bytes
| cmp +31,d2
| bls do_csum_remainder # 4-byte aligned remainder
|
| add -32,d2
| mov +32,d3
|
| do_csum_loop:
| mov (a0+),d0
| mov (a0+),e0
| mov (a0+),e1
| mov (a0+),e3
| add d0,d1
| addc e0,d1
| addc e1,d1
| addc e3,d1
| mov (a0+),d0
| mov (a0+),e0
| mov (a0+),e1
| mov (a0+),e3
| addc d0,d1
| addc e0,d1
| addc e1,d1
| addc e3,d1
| addc +0,d1
|
| sub d3,d2
| bcc do_csum_loop
|
| add d3,d2
| beq do_csum_done
|
| do_csum_remainder:
| # cut 16-31 bytes down to 0-15
| cmp +16,d2
| bcs do_csum_fewer_than_16
| mov (a0+),d0
| mov (a0+),e0
| mov (a0+),e1
| mov (a0+),e3
| add d0,d1
| addc e0,d1
| addc e1,d1
| addc e3,d1
| addc +0,d1
| add -16,d2
| beq do_csum_done
|
| do_csum_fewer_than_16:
| # copy the remaining whole words
| cmp +4,d2
| bcs do_csum_fewer_than_4
| cmp +8,d2
| bcs do_csum_one_word
| cmp +12,d2
| bcs do_csum_two_words
| mov (a0+),d0
| add d0,d1
| addc +0,d1
| do_csum_two_words:
| mov (a0+),d0
| add d0,d1
| addc +0,d1
| do_csum_one_word:
| mov (a0+),d0
| add d0,d1
| addc +0,d1
|
| do_csum_fewer_than_4:
| and +3,d2
| beq do_csum_done
| xor_cmp d0,d0,+2,d2
| bcs do_csum_fewer_than_2
| movhu (a0+),d0
| and +1,d2
| beq do_csum_add_last_bit
| do_csum_fewer_than_2:
| movbu (a0),d3
| add d3,d0
| do_csum_add_last_bit:
| add d0,d1
| addc +0,d1
|
| do_csum_done:
| # compress the checksum down to 16 bits
| mov +0xffff0000,d0
| and d1,d0
| asl +16,d1
| add d1,d0
| addc +0xffff,d0
| lsr +16,d0
|
| # flip the halves of the word result if the buffer was oddly aligned
| and +1,a1
| beq do_csum_not_oddly_aligned
| swaph d0,d0 # exchange bits 15:8 with 7:0
|
| do_csum_not_oddly_aligned:
| ret [d2,d3],8
|
| .size do_csum, .-do_csum
|
|
