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1/*
2 * A fast checksum routine using movem
3 * Copyright (c) 1998-2001 Axis Communications AB
4 *
5 * csum_partial(const unsigned char * buff, int len, unsigned int sum)
6 */
7
8 .globl csum_partial
9csum_partial:
10
11 ;; r10 - src
12 ;; r11 - length
13 ;; r12 - checksum
14
15 ;; check for breakeven length between movem and normal word looping versions
16 ;; we also do _NOT_ want to compute a checksum over more than the
17 ;; actual length when length < 40
18
19 cmpu.w 80,$r11
20 blo _word_loop
21 nop
22
23 ;; need to save the registers we use below in the movem loop
24 ;; this overhead is why we have a check above for breakeven length
25 ;; only r0 - r8 have to be saved, the other ones are clobber-able
26 ;; according to the ABI
27
28 subq 9*4,$sp
29 movem $r8,[$sp]
30
31 ;; do a movem checksum
32
33 subq 10*4,$r11 ; update length for the first loop
34
35_mloop: movem [$r10+],$r9 ; read 10 longwords
36
37 ;; perform dword checksumming on the 10 longwords
38
39 add.d $r0,$r12
40 ax
41 add.d $r1,$r12
42 ax
43 add.d $r2,$r12
44 ax
45 add.d $r3,$r12
46 ax
47 add.d $r4,$r12
48 ax
49 add.d $r5,$r12
50 ax
51 add.d $r6,$r12
52 ax
53 add.d $r7,$r12
54 ax
55 add.d $r8,$r12
56 ax
57 add.d $r9,$r12
58
59 ;; fold the carry into the checksum, to avoid having to loop the carry
60 ;; back into the top
61
62 ax
63 addq 0,$r12
64
65 subq 10*4,$r11
66 bge _mloop
67 nop
68
69 addq 10*4,$r11 ; compensate for last loop underflowing length
70
71 movem [$sp+],$r8 ; restore regs
72
73_word_loop:
74 ;; only fold if there is anything to fold.
75
76 cmpq 0,$r12
77 beq _no_fold
78
79 ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below.
80 ;; r9 and r13 can be used as temporaries.
81
82 moveq -1,$r9 ; put 0xffff in r9, faster than move.d 0xffff,r9
83 lsrq 16,$r9
84
85 move.d $r12,$r13
86 lsrq 16,$r13 ; r13 = checksum >> 16
87 and.d $r9,$r12 ; checksum = checksum & 0xffff
88 add.d $r13,$r12 ; checksum += r13
89
90_no_fold:
91 cmpq 2,$r11
92 blt _no_words
93 nop
94
95 ;; checksum the rest of the words
96
97 subq 2,$r11
98
99_wloop: subq 2,$r11
100 bge _wloop
101 addu.w [$r10+],$r12
102
103 addq 2,$r11
104
105_no_words:
106 ;; see if we have one odd byte more
107 cmpq 1,$r11
108 beq _do_byte
109 nop
110 ret
111 move.d $r12, $r10
112
113_do_byte:
114 ;; copy and checksum the last byte
115 addu.b [$r10],$r12
116 ret
117 move.d $r12, $r10
118
1/*
2 * A fast checksum routine using movem
3 * Copyright (c) 1998-2001 Axis Communications AB
4 *
5 * csum_partial(const unsigned char * buff, int len, unsigned int sum)
6 */
7
8 .globl csum_partial
9csum_partial:
10
11 ;; r10 - src
12 ;; r11 - length
13 ;; r12 - checksum
14
15 ;; check for breakeven length between movem and normal word looping versions
16 ;; we also do _NOT_ want to compute a checksum over more than the
17 ;; actual length when length < 40
18
19 cmpu.w 80,$r11
20 blo _word_loop
21 nop
22
23 ;; need to save the registers we use below in the movem loop
24 ;; this overhead is why we have a check above for breakeven length
25 ;; only r0 - r8 have to be saved, the other ones are clobber-able
26 ;; according to the ABI
27
28 subq 9*4,$sp
29 movem $r8,[$sp]
30
31 ;; do a movem checksum
32
33 subq 10*4,$r11 ; update length for the first loop
34
35_mloop: movem [$r10+],$r9 ; read 10 longwords
36
37 ;; perform dword checksumming on the 10 longwords
38
39 add.d $r0,$r12
40 ax
41 add.d $r1,$r12
42 ax
43 add.d $r2,$r12
44 ax
45 add.d $r3,$r12
46 ax
47 add.d $r4,$r12
48 ax
49 add.d $r5,$r12
50 ax
51 add.d $r6,$r12
52 ax
53 add.d $r7,$r12
54 ax
55 add.d $r8,$r12
56 ax
57 add.d $r9,$r12
58
59 ;; fold the carry into the checksum, to avoid having to loop the carry
60 ;; back into the top
61
62 ax
63 addq 0,$r12
64
65 subq 10*4,$r11
66 bge _mloop
67 nop
68
69 addq 10*4,$r11 ; compensate for last loop underflowing length
70
71 movem [$sp+],$r8 ; restore regs
72
73_word_loop:
74 ;; only fold if there is anything to fold.
75
76 cmpq 0,$r12
77 beq _no_fold
78
79 ;; fold 32-bit checksum into a 16-bit checksum, to avoid carries below.
80 ;; r9 and r13 can be used as temporaries.
81
82 moveq -1,$r9 ; put 0xffff in r9, faster than move.d 0xffff,r9
83 lsrq 16,$r9
84
85 move.d $r12,$r13
86 lsrq 16,$r13 ; r13 = checksum >> 16
87 and.d $r9,$r12 ; checksum = checksum & 0xffff
88 add.d $r13,$r12 ; checksum += r13
89
90_no_fold:
91 cmpq 2,$r11
92 blt _no_words
93 nop
94
95 ;; checksum the rest of the words
96
97 subq 2,$r11
98
99_wloop: subq 2,$r11
100 bge _wloop
101 addu.w [$r10+],$r12
102
103 addq 2,$r11
104
105_no_words:
106 ;; see if we have one odd byte more
107 cmpq 1,$r11
108 beq _do_byte
109 nop
110 ret
111 move.d $r12, $r10
112
113_do_byte:
114 ;; copy and checksum the last byte
115 addu.b [$r10],$r12
116 ret
117 move.d $r12, $r10
118