You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
88 lines
1.7 KiB
88 lines
1.7 KiB
/*
|
|
* A fast checksum routine using movem
|
|
* Copyright (c) 1998-2007 Axis Communications AB
|
|
*
|
|
* csum_partial(const unsigned char * buff, int len, unsigned int sum)
|
|
*/
|
|
|
|
.globl csum_partial
|
|
.type csum_partial,@function
|
|
csum_partial:
|
|
|
|
;; r10 - src
|
|
;; r11 - length
|
|
;; r12 - checksum
|
|
|
|
;; Optimized for large packets
|
|
subq 10*4, $r11
|
|
blt _word_loop
|
|
move.d $r11, $acr
|
|
|
|
subq 9*4,$sp
|
|
clearf c
|
|
movem $r8,[$sp]
|
|
|
|
;; do a movem checksum
|
|
|
|
_mloop: movem [$r10+],$r9 ; read 10 longwords
|
|
;; Loop count without touching the c flag.
|
|
addoq -10*4, $acr, $acr
|
|
;; perform dword checksumming on the 10 longwords
|
|
|
|
addc $r0,$r12
|
|
addc $r1,$r12
|
|
addc $r2,$r12
|
|
addc $r3,$r12
|
|
addc $r4,$r12
|
|
addc $r5,$r12
|
|
addc $r6,$r12
|
|
addc $r7,$r12
|
|
addc $r8,$r12
|
|
addc $r9,$r12
|
|
|
|
;; test $acr without trashing carry.
|
|
move.d $acr, $acr
|
|
bpl _mloop
|
|
;; r11 <= acr is not really needed in the mloop, just using the dslot
|
|
;; to prepare for what is needed after mloop.
|
|
move.d $acr, $r11
|
|
|
|
;; fold the last carry into r13
|
|
addc 0, $r12
|
|
movem [$sp+],$r8 ; restore regs
|
|
|
|
_word_loop:
|
|
addq 10*4,$r11 ; compensate for last loop underflowing length
|
|
|
|
moveq -1,$r9 ; put 0xffff in r9, faster than move.d 0xffff,r9
|
|
lsrq 16,$r9
|
|
|
|
move.d $r12,$r13
|
|
lsrq 16,$r13 ; r13 = checksum >> 16
|
|
and.d $r9,$r12 ; checksum = checksum & 0xffff
|
|
|
|
_no_fold:
|
|
subq 2,$r11
|
|
blt _no_words
|
|
add.d $r13,$r12 ; checksum += r13
|
|
|
|
;; checksum the rest of the words
|
|
_wloop: subq 2,$r11
|
|
bge _wloop
|
|
addu.w [$r10+],$r12
|
|
|
|
_no_words:
|
|
addq 2,$r11
|
|
;; see if we have one odd byte more
|
|
bne _do_byte
|
|
nop
|
|
ret
|
|
move.d $r12,$r10
|
|
|
|
_do_byte:
|
|
;; copy and checksum the last byte
|
|
addu.b [$r10],$r12
|
|
ret
|
|
move.d $r12,$r10
|
|
|
|
.size csum_partial, .-csum_partial
|
|
|