1 /* Copyright (C) 2011 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
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.
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.
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 <http://www.gnu.org/licenses/>. */
23 strlen (const char *s
)
25 /* Get an aligned pointer. */
26 const uintptr_t s_int
= (uintptr_t) s
;
27 const uint32_t *p
= (const uint32_t *) (s_int
& -4);
29 /* Read the first word, but force bytes before the string to be nonzero.
30 This expression works because we know shift counts are taken mod 32. */
31 uint32_t v
= *p
| ((1 << (s_int
<< 3)) - 1);
34 while ((bits
= __insn_seqb (v
, 0)) == 0)
37 return ((const char *) p
) + (__insn_ctz (bits
) >> 3) - s
;
39 libc_hidden_builtin_def (strlen
)