1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
/* $OpenBSD: ffs.S,v 1.4 2018/01/18 08:23:44 guenther Exp $ */
/* $NetBSD: ffs.S,v 1.3 1996/10/17 03:08:13 cgd Exp $ */
/*
* Copyright (c) 1995 Christopher G. Demetriou
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Christopher G. Demetriou
* for the NetBSD Project.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "SYS.h"
LEAF(ffs, 1)
addl a0, 0, t0
beq t0, Lallzero
/*
* Initialize return value (v0), and set up t1 so that it
* contains the mask with only the lowest bit set.
*/
subl zero, t0, t1
ldil v0, 1
and t0, t1, t1
and t1, 0xff, t2
bne t2, Ldo8
/*
* If lower 16 bits empty, add 16 to result and use upper 16.
*/
zapnot t1, 0x03, t3
bne t3, Ldo16
sra t1, 16, t1
addl v0, 16, v0
Ldo16:
/*
* If lower 8 bits empty, add 8 to result and use upper 8.
*/
and t1, 0xff, t4
bne t4, Ldo8
sra t1, 8, t1
addl v0, 8, v0
Ldo8:
and t1, 0x0f, t5 /* lower 4 of 8 empty? */
and t1, 0x33, t6 /* lower 2 of each 4 empty? */
and t1, 0x55, t7 /* lower 1 of each 2 empty? */
/* If lower 4 bits empty, add 4 to result. */
bne t5, Ldo4
addl v0, 4, v0
Ldo4: /* If lower 2 bits of each 4 empty, add 2 to result. */
bne t6, Ldo2
addl v0, 2, v0
Ldo2: /* If lower bit of each 2 empty, add 1 to result. */
bne t7, Ldone
addl v0, 1, v0
Ldone:
RET
Lallzero:
bis zero, zero, v0
RET
END(ffs)
.protected ffs
|
