mirror of
https://github.com/torvalds/linux.git
synced 2024-12-14 15:13:52 +00:00
ab244c1a08
Optimise do_csum() to gang up the loads so they're less likely to get interruptions between. Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com> Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com> Signed-off-by: David Howells <dhowells@redhat.com>
158 lines
2.8 KiB
ArmAsm
158 lines
2.8 KiB
ArmAsm
/* 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
|