summary refs log tree commit diff
path: root/sysdeps/arm/armv6t2/strlen.S
blob: 6988183ea63501f050beaaf0201db2a2439b5c8c (plain) (blame)
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
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
/* Copyright (C) 2010-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <http://www.gnu.org/licenses/>.  */

/*
   Assumes:
   ARMv6T2, AArch32

 */

#include <arm-features.h>               /* This might #define NO_THUMB.  */
#include <sysdep.h>

#ifdef __ARMEB__
#define S2LO		lsl
#define S2HI		lsr
#else
#define S2LO		lsr
#define S2HI		lsl
#endif

#ifndef NO_THUMB
/* This code is best on Thumb.  */
	.thumb
#else
/* Using bne.w explicitly is desirable in Thumb mode because it helps
   align the following label without a nop.  In ARM mode there is no
   such difference.  */
.macro bne.w label
	bne \label
.endm

/* This clobbers the condition codes, which the real Thumb cbnz instruction
   does not do.  But it doesn't matter for any of the uses here.  */
.macro cbnz reg, label
	cmp \reg, #0
	bne \label
.endm
#endif

/* Parameters and result.  */
#define srcin		r0
#define result		r0

/* Internal variables.  */
#define src		r1
#define data1a		r2
#define data1b		r3
#define const_m1	r12
#define const_0		r4
#define tmp1		r4		/* Overlaps const_0  */
#define tmp2		r5

	.text
	.p2align 6
ENTRY(strlen)
	pld	[srcin, #0]
	strd	r4, r5, [sp, #-8]!
	cfi_adjust_cfa_offset (8)
	cfi_rel_offset (r4, 0)
	cfi_rel_offset (r5, 4)
	cfi_remember_state
	bic	src, srcin, #7
	mvn	const_m1, #0
	ands	tmp1, srcin, #7		/* (8 - bytes) to alignment.  */
	pld	[src, #32]
	bne.w	.Lmisaligned8
	mov	const_0, #0
	mov	result, #-8
.Lloop_aligned:
	/* Bytes 0-7.  */
	ldrd	data1a, data1b, [src]
	pld	[src, #64]
	add	result, result, #8
.Lstart_realigned:
	uadd8	data1a, data1a, const_m1	/* Saturating GE<0:3> set.  */
	sel	data1a, const_0, const_m1	/* Select based on GE<0:3>.  */
	uadd8	data1b, data1b, const_m1
	sel	data1b, data1a, const_m1	/* Only used if d1a == 0.  */
	cbnz	data1b, .Lnull_found

	/* Bytes 8-15.  */
	ldrd	data1a, data1b, [src, #8]
	uadd8	data1a, data1a, const_m1	/* Saturating GE<0:3> set.  */
	add	result, result, #8
	sel	data1a, const_0, const_m1	/* Select based on GE<0:3>.  */
	uadd8	data1b, data1b, const_m1
	sel	data1b, data1a, const_m1	/* Only used if d1a == 0.  */
	cbnz	data1b, .Lnull_found

	/* Bytes 16-23.  */
	ldrd	data1a, data1b, [src, #16]
	uadd8	data1a, data1a, const_m1	/* Saturating GE<0:3> set.  */
	add	result, result, #8
	sel	data1a, const_0, const_m1	/* Select based on GE<0:3>.  */
	uadd8	data1b, data1b, const_m1
	sel	data1b, data1a, const_m1	/* Only used if d1a == 0.  */
	cbnz	data1b, .Lnull_found

	/* Bytes 24-31.  */
	ldrd	data1a, data1b, [src, #24]
	add	src, src, #32
	uadd8	data1a, data1a, const_m1	/* Saturating GE<0:3> set.  */
	add	result, result, #8
	sel	data1a, const_0, const_m1	/* Select based on GE<0:3>.  */
	uadd8	data1b, data1b, const_m1
	sel	data1b, data1a, const_m1	/* Only used if d1a == 0.  */
	cmp	data1b, #0
	beq	.Lloop_aligned

.Lnull_found:
	cmp	data1a, #0
	itt	eq
	addeq	result, result, #4
	moveq	data1a, data1b
#ifndef __ARMEB__
	rev	data1a, data1a
#endif
	clz	data1a, data1a
	ldrd	r4, r5, [sp], #8
	cfi_adjust_cfa_offset (-8)
	cfi_restore (r4)
	cfi_restore (r5)
	add	result, result, data1a, lsr #3	/* Bits -> Bytes.  */
	DO_RET(lr)

.Lmisaligned8:
	cfi_restore_state
	ldrd	data1a, data1b, [src]
	and	tmp2, tmp1, #3
	rsb	result, tmp1, #0
	lsl	tmp2, tmp2, #3			/* Bytes -> bits.  */
	tst	tmp1, #4
	pld	[src, #64]
	S2HI	tmp2, const_m1, tmp2
#ifdef NO_THUMB
	mvn	tmp1, tmp2
	orr	data1a, data1a, tmp1
	itt	ne
	orrne	data1b, data1b, tmp1
#else
	orn	data1a, data1a, tmp2
	itt	ne
	ornne	data1b, data1b, tmp2
#endif
	movne	data1a, const_m1
	mov	const_0, #0
	b	.Lstart_realigned

END(strlen)
libc_hidden_builtin_def (strlen)