xref: /linux/arch/arm/lib/findbit.S (revision 7ae9fb1b7ecbb5d85d07857943f677fd1a559b18)
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/lib/findbit.S
4 *
5 *  Copyright (C) 1995-2000 Russell King
6 *
7 * 16th March 2001 - John Ripley <jripley@sonicblue.com>
8 *   Fixed so that "size" is an exclusive not an inclusive quantity.
9 *   All users of these functions expect exclusive sizes, and may
10 *   also call with zero size.
11 * Reworked by rmk.
12 */
13#include <linux/linkage.h>
14#include <asm/assembler.h>
15#include <asm/unwind.h>
16                .text
17
18#ifdef __ARMEB__
19#define SWAB_ENDIAN le
20#else
21#define SWAB_ENDIAN be
22#endif
23
24		.macro	find_first, endian, set, name
25ENTRY(_find_first_\name\()bit_\endian)
26	UNWIND(	.fnstart)
27		teq	r1, #0
28		beq	3f
29		mov	r2, #0
301:		ldr	r3, [r0], #4
31		.ifeq \set
32		mvns	r3, r3			@ invert/test bits
33		.else
34		movs	r3, r3			@ test bits
35		.endif
36		.ifc \endian, SWAB_ENDIAN
37		bne	.L_found_swab
38		.else
39		bne	.L_found		@ found the bit?
40		.endif
41		add	r2, r2, #32		@ next index
422:		cmp	r2, r1			@ any more?
43		blo	1b
443:		mov	r0, r1			@ no more bits
45		ret	lr
46	UNWIND(	.fnend)
47ENDPROC(_find_first_\name\()bit_\endian)
48		.endm
49
50		.macro	find_next, endian, set, name
51ENTRY(_find_next_\name\()bit_\endian)
52	UNWIND(	.fnstart)
53		cmp	r2, r1
54		bhs	3b
55		mov	ip, r2, lsr #5		@ word index
56		add	r0, r0, ip, lsl #2
57		ands	ip, r2, #31		@ bit position
58		beq	1b
59		ldr	r3, [r0], #4
60		.ifeq \set
61		mvn	r3, r3			@ invert bits
62		.endif
63		.ifc \endian, SWAB_ENDIAN
64		rev_l	r3, ip
65		.if	.Lrev_l_uses_tmp
66		@ we need to recompute ip because rev_l will have overwritten
67		@ it.
68		and	ip, r2, #31		@ bit position
69		.endif
70		.endif
71		movs	r3, r3, lsr ip		@ shift off unused bits
72		bne	.L_found
73		orr	r2, r2, #31		@ no zero bits
74		add	r2, r2, #1		@ align bit pointer
75		b	2b			@ loop for next bit
76	UNWIND(	.fnend)
77ENDPROC(_find_next_\name\()bit_\endian)
78		.endm
79
80		.macro	find_bit, endian, set, name
81		find_first \endian, \set, \name
82		find_next  \endian, \set, \name
83		.endm
84
85/* _find_first_zero_bit_le and _find_next_zero_bit_le */
86		find_bit le, 0, zero_
87
88/* _find_first_bit_le and _find_next_bit_le */
89		find_bit le, 1
90
91#ifdef __ARMEB__
92
93/* _find_first_zero_bit_be and _find_next_zero_bit_be */
94		find_bit be, 0, zero_
95
96/* _find_first_bit_be and _find_next_bit_be */
97		find_bit be, 1
98
99#endif
100
101/*
102 * One or more bits in the LSB of r3 are assumed to be set.
103 */
104.L_found_swab:
105	UNWIND(	.fnstart)
106		rev_l	r3, ip
107.L_found:
108#if __LINUX_ARM_ARCH__ >= 7
109		rbit	r3, r3			@ reverse bits
110		clz	r3, r3			@ count high zero bits
111		add	r0, r2, r3		@ add offset of first set bit
112#elif __LINUX_ARM_ARCH__ >= 5
113		rsb	r0, r3, #0
114		and	r3, r3, r0		@ mask out lowest bit set
115		clz	r3, r3			@ count high zero bits
116		rsb	r3, r3, #31		@ offset of first set bit
117		add	r0, r2, r3		@ add offset of first set bit
118#else
119		mov	ip, #~0
120		tst	r3, ip, lsr #16		@ test bits 0-15
121		addeq	r2, r2, #16
122		moveq	r3, r3, lsr #16
123		tst	r3, #0x00ff
124		addeq	r2, r2, #8
125		moveq	r3, r3, lsr #8
126		tst	r3, #0x000f
127		addeq	r2, r2, #4
128		moveq	r3, r3, lsr #4
129		tst	r3, #0x0003
130		addeq	r2, r2, #2
131		moveq	r3, r3, lsr #2
132		tst	r3, #0x0001
133		addeq	r2, r2, #1
134		mov	r0, r2
135#endif
136		cmp	r1, r0			@ Clamp to maxbit
137		movlo	r0, r1
138		ret	lr
139	UNWIND(	.fnend)
140