ports/sysdeps/tile/tilepro/rawmemchr.c

   1 /* Copyright (C) 2011-2014 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
  22 void *
  23 __rawmemchr (const void *s, int c)
  24 {
  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);
  28
  29   /* Create four copies of the byte for which we are looking. */
  30   const uint32_t goal = 0x01010101 * (uint8_t) c;
  31
  32   /* Read the first word, but munge it so that bytes before the array
  33      will not match goal.  Note that this shift count expression works
  34      because we know shift counts are taken mod 32.  */
  35   const uint32_t before_mask = (1 << (s_int << 3)) - 1;
  36   uint32_t v = (*p | before_mask) ^ (goal & before_mask);
  37
  38   uint32_t bits;
  39   while ((bits = __insn_seqb (v, goal)) == 0)
  40     v = *++p;
  41
  42   return ((char *) p) + (__insn_ctz (bits) >> 3);
  43 }
  44 libc_hidden_def (__rawmemchr)
  45 weak_alias (__rawmemchr, rawmemchr)