Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/arm/lib/findbit.S
26295 views
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 <[email protected]>

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

25
ENTRY(_find_first_\name\()bit_\endian)

26
	UNWIND(	.fnstart)

27
		teq	r1, #0

28
		beq	3f

29
		mov	r2, #0

30
1:		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

42
2:		cmp	r2, r1			@ any more?

43
		blo	1b

44
3:		mov	r0, r1			@ no more bits

45
		ret	lr

46
	UNWIND(	.fnend)

47
ENDPROC(_find_first_\name\()bit_\endian)

48
		.endm

49


50
		.macro	find_next, endian, set, name

51
ENTRY(_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)

77
ENDPROC(_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


141