mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-13 06:42:56 +00:00
dbaef6ef33
The new implementation is about twice as fast as the old. This is from glibc-2.14, sysdeps/i386/memset.c. Signed-off-by: Gabe Black <gabeblack@chromium.org>
87 lines
2.4 KiB
C
87 lines
2.4 KiB
C
/*
|
|
* Copyright (C) 1991,1992,1993,1997,1998,2003, 2005 Free Software Foundation, Inc.
|
|
* This file is part of the GNU C Library.
|
|
* Copyright (c) 2011 The Chromium OS Authors.
|
|
*
|
|
* See file CREDITS for list of people who contributed to this
|
|
* project.
|
|
*
|
|
* 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.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
|
|
* MA 02111-1307 USA
|
|
*/
|
|
|
|
/* From glibc-2.14, sysdeps/i386/memset.c */
|
|
|
|
#include <compiler.h>
|
|
#include <asm/string.h>
|
|
#include <linux/types.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;
|
|
}
|