1/* Optimized strlen implementation for PowerPC476.
2   Copyright (C) 2010-2021 Free Software Foundation, Inc.
3   This file is part of the GNU C Library.
4
5   The GNU C Library is free software; you can redistribute it and/or
6   modify it under the terms of the GNU Lesser General Public
7   License as published by the Free Software Foundation; either
8   version 2.1 of the License, or (at your option) any later version.
9
10   The GNU C Library is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   Lesser General Public License for more details.
14
15   You should have received a copy of the GNU Lesser General Public
16   License along with the GNU C Library.  If not, see
17   <https://www.gnu.org/licenses/>.  */
18
19#include <sysdep.h>
20
21/* strlen
22
23       Register Use
24       r3:source address and return length of string
25       r4:byte counter
26
27       Implementation description
28       Load 2 words at a time and count bytes, if we find null we subtract one from
29       the count and return the count value. We need to subtract one because
30       we don't count the null character as a byte. */
31
32EALIGN (strlen,5,0)
33       neg     r7,r3
34       clrlwi. r8,r7,29
35       addi    r4,0,0
36       beq     L(byte_count_loop)
37       mtctr   r8
38
39L(loop):
40       lbz     r5,0(r3)
41       cmpi    cr5,r5,0x0
42       addi    r3,r3,0x1
43       addi    r4,r4,0x1
44       beq     cr5,L(end_strlen)
45       bdnz    L(loop)
46
47L(byte_count_loop):
48       lwz     r5,0(r3)
49       lwz     r6,4(r3)
50       dlmzb.  r12,r5,r6
51       add     r4,r4,r12
52       bne     L(end_strlen)
53       lwz     r5,8(r3)
54       lwz     r6,12(r3)
55       dlmzb.  r12,r5,r6
56       add     r4,r4,r12
57       bne     L(end_strlen)
58       lwz     r5,16(r3)
59       lwz     r6,20(r3)
60       dlmzb.  r12,r5,r6
61       add     r4,r4,r12
62       bne     L(end_strlen)
63       lwz     r5,24(r3)
64       lwz     r6,28(r3)
65       addi    r3,r3,0x20
66       dlmzb.  r12,r5,r6
67       add     r4,r4,r12
68       bne     L(end_strlen)
69       b       L(byte_count_loop)
70
71L(end_strlen):
72       addi    r3,r4,-1
73       blr
74END (strlen)
75libc_hidden_builtin_def (strlen)
76