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/*
* This file is part of the GNU C Library.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program 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 General Public License for more details.
*/
/* From glibc-2.14, sysdeps/i386/memset.c */
#include <string.h>
#include <stdint.h>
typedef uint32_t op_t;
void *memset(void *dstpp, int c, size_t len)
{
int d0;
unsigned long int dstp = (unsigned long int) dstpp;
/* This explicit register allocation improves code very much indeed. */
register op_t x asm("ax");
x = (unsigned char) c;
/* Clear the direction flag, so filling will move forward. */
asm volatile("cld");
/* This threshold value is optimal. */
if (len >= 12) {
/* Fill X with four copies of the char we want to fill with. */
x |= (x << 8);
x |= (x << 16);
/* Adjust LEN for the bytes handled in the first loop. */
len -= (-dstp) % sizeof(op_t);
/*
* 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), "=c" (d0) :
"0" (dstp), "1" ((-dstp) % sizeof(op_t)), "a" (x) :
"memory");
/* Fill longwords. */
asm volatile(
"rep\n"
"stosl" /* %0, %2, %3 */ :
"=D" (dstp), "=c" (d0) :
"0" (dstp), "1" (len / sizeof(op_t)), "a" (x) :
"memory");
len %= sizeof(op_t);
}
/* Write the last few bytes. */
asm volatile(
"rep\n"
"stosb" /* %0, %2, %3 */ :
"=D" (dstp), "=c" (d0) :
"0" (dstp), "1" (len), "a" (x) :
"memory");
return dstpp;
}
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