string/memset.c

   1 /* Copyright (C) 1991-2024 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    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <string.h>
  19 #include <memcopy.h>
  20
  21 #ifndef MEMSET
  22 # define MEMSET memset
  23 #endif
  24
  25 void *
  26 inhibit_loop_to_libcall
  27 MEMSET (void *dstpp, int c, size_t len)
  28 {
  29   long int dstp = (long int) dstpp;
  30
  31   if (len >= 8)
  32     {
  33       size_t xlen;
  34       op_t cccc;
  35
  36       cccc = (unsigned char) c;
  37       cccc |= cccc << 8;
  38       cccc |= cccc << 16;
  39       if (OPSIZ > 4)
  40         /* Do the shift in two steps to avoid warning if long has 32 bits.  */
  41         cccc |= (cccc << 16) << 16;
  42
  43       /* There are at least some bytes to set.
  44          No need to test for LEN == 0 in this alignment loop.  */
  45       while (dstp % OPSIZ != 0)
  46         {
  47           ((byte *) dstp)[0] = c;
  48           dstp += 1;
  49           len -= 1;
  50         }
  51
  52       /* Write 8 `op_t' per iteration until less than 8 `op_t' remain.  */
  53       xlen = len / (OPSIZ * 8);
  54       while (xlen > 0)
  55         {
  56           ((op_t *) dstp)[0] = cccc;
  57           ((op_t *) dstp)[1] = cccc;
  58           ((op_t *) dstp)[2] = cccc;
  59           ((op_t *) dstp)[3] = cccc;
  60           ((op_t *) dstp)[4] = cccc;
  61           ((op_t *) dstp)[5] = cccc;
  62           ((op_t *) dstp)[6] = cccc;
  63           ((op_t *) dstp)[7] = cccc;
  64           dstp += 8 * OPSIZ;
  65           xlen -= 1;
  66         }
  67       len %= OPSIZ * 8;
  68
  69       /* Write 1 `op_t' per iteration until less than OPSIZ bytes remain.  */
  70       xlen = len / OPSIZ;
  71       while (xlen > 0)
  72         {
  73           ((op_t *) dstp)[0] = cccc;
  74           dstp += OPSIZ;
  75           xlen -= 1;
  76         }
  77       len %= OPSIZ;
  78     }
  79
  80   /* Write the last few bytes.  */
  81   while (len > 0)
  82     {
  83       ((byte *) dstp)[0] = c;
  84       dstp += 1;
  85       len -= 1;
  86     }
  87
  88   return dstpp;
  89 }
  90 libc_hidden_builtin_def (MEMSET)