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
|
/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2009 by Maurus Cuelenaere
* based on ffs-arm.S by Michael Sevakis
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#include "config.h"
#include "mips.h"
/****************************************************************************
* int find_first_set_bit(uint32_t val);
*
* Find the index of the least significant set bit in the 32-bit word.
*
* return values:
* 0 - bit 0 is set
* 1 - bit 1 is set
* ...
* 31 - bit 31 is set
* 32 - no bits set
****************************************************************************/
.align 2
.global find_first_set_bit
.type find_first_set_bit, %function
.set noreorder
.set noat
find_first_set_bit:
beqz a0, l # if(a0 == 0) goto l
nop #
negu t0, a0 # t0 = -a0
and t0, a0, t0 # t0 = a0 & t0
clz v0, t0 # get lead 0's count
li t0, 31 # t0 = 31
jr ra #
subu v0, t0, v0 # v0 = t0 - v0
l:
jr ra #
li v0, 32 # v0 = 32
.set reorder
.set at
|
