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/*
* A fast checksum+copy routine using movem
* Copyright (c) 1998-2007 Axis Communications AB
*
* Authors: Bjorn Wesen
*
* csum_partial_copy_nocheck(const char *src, char *dst,
* int len, unsigned int sum)
*/
.globl csum_partial_copy_nocheck
csum_partial_copy_nocheck:
;; r10 - src
;; r11 - dst
;; r12 - length
;; r13 - checksum
;; Optimized for large packets
subq 10*4, $r12
blt _word_loop
move.d $r12, $acr
subq 9*4,$sp
clearf c
movem $r8,[$sp]
;; do a movem copy and checksum
1: ;; A failing userspace access (the read) will have this as PC.
_mloop: movem [$r10+],$r9 ; read 10 longwords
addoq -10*4, $acr, $acr ; loop counter in latency cycle
movem $r9,[$r11+] ; write 10 longwords
;; perform dword checksumming on the 10 longwords
addc $r0,$r13
addc $r1,$r13
addc $r2,$r13
addc $r3,$r13
addc $r4,$r13
addc $r5,$r13
addc $r6,$r13
addc $r7,$r13
addc $r8,$r13
addc $r9,$r13
;; test $acr, without trashing carry.
move.d $acr, $acr
bpl _mloop
;; r12 <= acr is needed after mloop and in the exception handlers.
move.d $acr, $r12
;; fold the last carry into r13
addc 0, $r13
movem [$sp+],$r8 ; restore regs
_word_loop:
addq 10*4,$r12 ; compensate for last loop underflowing length
;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below
;; r9 can be used as temporary.
move.d $r13,$r9
lsrq 16,$r9 ; r0 = checksum >> 16
and.d 0xffff,$r13 ; checksum = checksum & 0xffff
subq 2, $r12
blt _no_words
add.d $r9,$r13 ; checksum += r0
;; copy and checksum the rest of the words
2: ;; A failing userspace access for the read below will have this as PC.
_wloop: move.w [$r10+],$r9
addu.w $r9,$r13
subq 2,$r12
bge _wloop
move.w $r9,[$r11+]
_no_words:
addq 2,$r12
bne _do_byte
nop
ret
move.d $r13,$r10
_do_byte:
;; copy and checksum the last byte
3: ;; A failing userspace access for the read below will have this as PC.
move.b [$r10],$r9
addu.b $r9,$r13
move.b $r9,[$r11]
ret
move.d $r13,$r10
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