sysdeps/tile/tilegx/memchr.c

   1 /* Copyright (C) 2011-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
   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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <stdint.h>
  21 #include "string-endian.h"
  22
  23 void *
  24 __memchr (const void *s, int c, size_t n)
  25 {
  26   const uint64_t *last_word_ptr;
  27   const uint64_t *p;
  28   const char *last_byte_ptr;
  29   uintptr_t s_int;
  30   uint64_t goal, before_mask, v, bits;
  31   char *ret;
  32
  33   if (__builtin_expect (n == 0, 0))
  34     {
  35       /* Don't dereference any memory if the array is empty. */
  36       return NULL;
  37     }
  38
  39   /* Get an aligned pointer. */
  40   s_int = (uintptr_t) s;
  41   p = (const uint64_t *) (s_int & -8);
  42
  43   /* Create eight copies of the byte for which we are looking. */
  44   goal = copy_byte(c);
  45
  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);
  50
  51   /* Compute the address of the last byte. */
  52   last_byte_ptr = (const char *) s + n - 1;
  53
  54   /* Compute the address of the word containing the last byte. */
  55   last_word_ptr = (const uint64_t *) ((uintptr_t) last_byte_ptr & -8);
  56
  57   while ((bits = __insn_v1cmpeq (v, goal)) == 0)
  58     {
  59       if (__builtin_expect (p == last_word_ptr, 0))
  60         {
  61           /* We already read the last word in the array, so give up.  */
  62           return NULL;
  63         }
  64       v = *++p;
  65     }
  66
  67   /* We found a match, but it might be in a byte past the end
  68      of the array.  */
  69   ret = ((char *) p) + (CFZ (bits) >> 3);
  70   return (ret <= last_byte_ptr) ? ret : NULL;
  71 }
  72 weak_alias (__memchr, memchr)
  73 libc_hidden_builtin_def (memchr)