ports/sysdeps/tile/tilepro/strlen.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 size_t
  23 strlen (const char *s)
  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   /* 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);
  32
  33   uint32_t bits;
  34   while ((bits = __insn_seqb (v, 0)) == 0)
  35     v = *++p;
  36
  37   return ((const char *) p) + (__insn_ctz (bits) >> 3) - s;
  38 }
  39 libc_hidden_builtin_def (strlen)