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/* bzero -- set a block of memory to zero.
For Intel 80x86, x>=3.
Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
Contributed by Torbjorn Granlund (tege@sics.se).
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <ansidecl.h>
#include <string.h>
#include <memcopy.h>
#undef bzero
#ifdef __GNUC__
void
DEFUN(bzero, (dstpp, len),
PTR dstpp AND size_t len)
{
/* N.B.: This code is almost verbatim from memset.c. */
unsigned long int dstp = (unsigned long int) dstpp;
/* This explicit register allocation
improves code very much indeed. */
register op_t x asm("ax");
x = 0;
/* Clear the direction flag, so filling will move forward. */
asm volatile("cld");
/* This threshold value is optimal. */
if (len >= 12)
{
/* Adjust LEN for the bytes handled in the first loop. */
len -= (-dstp) % OPSIZ;
/* There are at least some bytes to set.
No need to test for LEN == 0 in this alignment loop. */
/* Fill bytes until DSTP is aligned on a longword boundary. */
asm volatile("rep\n"
"stosb" /* %0, %2, %3 */ :
"=D" (dstp) :
"0" (dstp), "c" ((-dstp) % OPSIZ), "a" (x) :
"cx");
/* Fill longwords. */
asm volatile("rep\n"
"stosl" /* %0, %2, %3 */ :
"=D" (dstp) :
"0" (dstp), "c" (len / OPSIZ), "a" (x) :
"cx");
len %= OPSIZ;
}
/* Write the last few bytes. */
asm volatile("rep\n"
"stosb" /* %0, %2, %3 */ :
"=D" (dstp) :
"0" (dstp), "c" (len), "a" (x) :
"cx");
}
#else
#include <sysdeps/generic/bzero.c>
#endif
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