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1/*
2 * A fast checksum+copy routine using movem
3 * Copyright (c) 1998-2007 Axis Communications AB
4 *
5 * Authors:	Bjorn Wesen
6 *
7 * csum_partial_copy_nocheck(const char *src, char *dst,
8 *		             int len, unsigned int sum)
9 */
10
11	.globl	csum_partial_copy_nocheck
12	.type   csum_partial_copy_nocheck,@function
13csum_partial_copy_nocheck:
14
15	;; r10 - src
16	;; r11 - dst
17	;; r12 - length
18	;; r13 - checksum
19
20	;; Optimized for large packets
21	subq	10*4, $r12
22	blt	_word_loop
23	move.d	$r12, $acr
24
25	subq	9*4,$sp
26	clearf	c
27	movem	$r8,[$sp]
28
29	;; do a movem copy and checksum
301:	;; A failing userspace access (the read) will have this as PC.
31_mloop:	movem	[$r10+],$r9	; read 10 longwords
32	addoq	-10*4, $acr, $acr ; loop counter in latency cycle
33	movem	$r9,[$r11+]	; write 10 longwords
34
35	;; perform dword checksumming on the 10 longwords
36	addc	$r0,$r13
37	addc	$r1,$r13
38	addc	$r2,$r13
39	addc	$r3,$r13
40	addc	$r4,$r13
41	addc	$r5,$r13
42	addc	$r6,$r13
43	addc	$r7,$r13
44	addc	$r8,$r13
45	addc	$r9,$r13
46
47	;; test $acr, without trashing carry.
48	move.d	$acr, $acr
49	bpl	_mloop
50	;; r12 <= acr  is needed after mloop and in the exception handlers.
51	move.d	$acr, $r12
52
53	;; fold the last carry into r13
54	addc	0, $r13
55	movem	[$sp+],$r8	; restore regs
56
57_word_loop:
58	addq	10*4,$r12	; compensate for last loop underflowing length
59
60	;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below
61	;; r9 can be used as temporary.
62	move.d	$r13,$r9
63	lsrq	16,$r9		; r0 = checksum >> 16
64	and.d	0xffff,$r13	; checksum = checksum & 0xffff
65
66	subq	2, $r12
67	blt	_no_words
68	add.d	$r9,$r13	; checksum += r0
69
70	;; copy and checksum the rest of the words
712:	;; A failing userspace access for the read below will have this as PC.
72_wloop:	move.w	[$r10+],$r9
73	addu.w	$r9,$r13
74	subq	2,$r12
75	bge	_wloop
76	move.w	$r9,[$r11+]
77
78_no_words:
79	addq	2,$r12
80	bne	_do_byte
81	nop
82	ret
83	move.d	$r13,$r10
84
85_do_byte:
86	;; copy and checksum the last byte
873:	;; A failing userspace access for the read below will have this as PC.
88	move.b	[$r10],$r9
89	addu.b	$r9,$r13
90	move.b	$r9,[$r11]
91	ret
92	move.d	$r13,$r10
93
94	.size   csum_partial_copy_nocheck, . - csum_partial_copy_nocheck
95