string/memset.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <memcopy.h>
  20
  21 #undef memset
  22
  23 void *
  24 inhibit_loop_to_libcall
  25 memset (void *dstpp, int c, size_t len)
  26 {
  27   long int dstp = (long int) dstpp;
  28
  29   if (len >= 8)
  30     {
  31       size_t xlen;
  32       op_t cccc;
  33
  34       cccc = (unsigned char) c;
  35       cccc |= cccc << 8;
  36       cccc |= cccc << 16;
  37       if (OPSIZ > 4)
  38         /* Do the shift in two steps to avoid warning if long has 32 bits.  */
  39         cccc |= (cccc << 16) << 16;
  40
  41       /* There are at least some bytes to set.
  42          No need to test for LEN == 0 in this alignment loop.  */
  43       while (dstp % OPSIZ != 0)
  44         {
  45           ((byte *) dstp)[0] = c;
  46           dstp += 1;
  47           len -= 1;
  48         }
  49
  50       /* Write 8 `op_t' per iteration until less than 8 `op_t' remain.  */
  51       xlen = len / (OPSIZ * 8);
  52       while (xlen > 0)
  53         {
  54           ((op_t *) dstp)[0] = cccc;
  55           ((op_t *) dstp)[1] = cccc;
  56           ((op_t *) dstp)[2] = cccc;
  57           ((op_t *) dstp)[3] = cccc;
  58           ((op_t *) dstp)[4] = cccc;
  59           ((op_t *) dstp)[5] = cccc;
  60           ((op_t *) dstp)[6] = cccc;
  61           ((op_t *) dstp)[7] = cccc;
  62           dstp += 8 * OPSIZ;
  63           xlen -= 1;
  64         }
  65       len %= OPSIZ * 8;
  66
  67       /* Write 1 `op_t' per iteration until less than OPSIZ bytes remain.  */
  68       xlen = len / OPSIZ;
  69       while (xlen > 0)
  70         {
  71           ((op_t *) dstp)[0] = cccc;
  72           dstp += OPSIZ;
  73           xlen -= 1;
  74         }
  75       len %= OPSIZ;
  76     }
  77
  78   /* Write the last few bytes.  */
  79   while (len > 0)
  80     {
  81       ((byte *) dstp)[0] = c;
  82       dstp += 1;
  83       len -= 1;
  84     }
  85
  86   return dstpp;
  87 }
  88 libc_hidden_builtin_def (memset)