1/* Copyright (C) 1998-2022 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library.  If not, see
16   <https://www.gnu.org/licenses/>.  */
17
18/* Thumb requires excessive IT insns here.  */
19#define NO_THUMB
20#include <sysdep.h>
21
22/* size_t strlen(const char *S)
23 * entry: r0 -> string
24 * exit: r0 = len
25 */
26
27	.syntax unified
28	.text
29
30ENTRY(strlen)
31	bic     r1, r0, $3              @ addr of word containing first byte
32	ldr     r2, [r1], $4            @ get the first word
33	ands    r3, r0, $3              @ how many bytes are duff?
34	rsb     r0, r3, $0              @ get - that number into counter.
35	beq     Laligned                @ skip into main check routine if no
36					@ more
37#ifdef __ARMEB__
38	orr     r2, r2, $0xff000000     @ set this byte to non-zero
39	subs    r3, r3, $1              @ any more to do?
40	orrgt   r2, r2, $0x00ff0000     @ if so, set this byte
41	subs    r3, r3, $1              @ more?
42	orrgt   r2, r2, $0x0000ff00     @ then set.
43#else
44	orr     r2, r2, $0x000000ff     @ set this byte to non-zero
45	subs    r3, r3, $1              @ any more to do?
46	orrgt   r2, r2, $0x0000ff00     @ if so, set this byte
47	subs    r3, r3, $1              @ more?
48	orrgt   r2, r2, $0x00ff0000     @ then set.
49#endif
50Laligned:				@ here, we have a word in r2.  Does it
51	tst     r2, $0x000000ff         @ contain any zeroes?
52	tstne   r2, $0x0000ff00         @
53	tstne   r2, $0x00ff0000         @
54	tstne   r2, $0xff000000         @
55	addne   r0, r0, $4              @ if not, the string is 4 bytes longer
56	ldrne   r2, [r1], $4            @ and we continue to the next word
57	bne     Laligned                @
58Llastword:				@ drop through to here once we find a
59#ifdef __ARMEB__
60	tst     r2, $0xff000000         @ word that has a zero byte in it
61	addne   r0, r0, $1              @
62	tstne   r2, $0x00ff0000         @ and add up to 3 bytes on to it
63	addne   r0, r0, $1              @
64	tstne   r2, $0x0000ff00         @ (if first three all non-zero, 4th
65	addne   r0, r0, $1              @  must be zero)
66#else
67	tst     r2, $0x000000ff         @ word that has a zero byte in it
68	addne   r0, r0, $1              @
69	tstne   r2, $0x0000ff00         @ and add up to 3 bytes on to it
70	addne   r0, r0, $1              @
71	tstne   r2, $0x00ff0000         @ (if first three all non-zero, 4th
72	addne   r0, r0, $1              @  must be zero)
73#endif
74	DO_RET(lr)
75END(strlen)
76libc_hidden_builtin_def (strlen)
77