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Diffstat (limited to 'arch/mn10300/lib/do_csum.S')
| -rw-r--r-- | arch/mn10300/lib/do_csum.S | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/arch/mn10300/lib/do_csum.S b/arch/mn10300/lib/do_csum.S new file mode 100644 index 000000000..1d27bba0c --- /dev/null +++ b/arch/mn10300/lib/do_csum.S @@ -0,0 +1,157 @@ +/* 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 |