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/>. */
21 #include "string-endian.h"
24 __memchr (const void *s
, int c
, size_t n
)
26 const uint64_t *last_word_ptr
;
28 const char *last_byte_ptr
;
30 uint64_t goal
, before_mask
, v
, bits
;
33 if (__builtin_expect (n
== 0, 0))
35 /* Don't dereference any memory if the array is empty. */
39 /* Get an aligned pointer. */
40 s_int
= (uintptr_t) s
;
41 p
= (const uint64_t *) (s_int
& -8);
43 /* Create eight copies of the byte for which we are looking. */
44 goal
= 0x0101010101010101ULL
* (uint8_t) c
;
46 /* Read the first word, but munge it so that bytes before the array
47 will not match goal. */
48 before_mask
= MASK (s_int
);
49 v
= (*p
| before_mask
) ^ (goal
& before_mask
);
51 /* Compute the address of the last byte. */
52 last_byte_ptr
= (const char *) s
+ n
- 1;
54 /* Compute the address of the word containing the last byte. */
55 last_word_ptr
= (const uint64_t *) ((uintptr_t) last_byte_ptr
& -8);
57 while ((bits
= __insn_v1cmpeq (v
, goal
)) == 0)
59 if (__builtin_expect (p
== last_word_ptr
, 0))
61 /* We already read the last word in the array, so give up. */
67 /* We found a match, but it might be in a byte past the end
69 ret
= ((char *) p
) + (CFZ (bits
) >> 3);
70 return (ret
<= last_byte_ptr
) ? ret
: NULL
;
72 weak_alias (__memchr
, memchr
)
73 libc_hidden_builtin_def (memchr
)