1 /* 2 * Copyright (C) 1991,1992,1993,1997,1998,2003, 2005 Free Software Foundation, Inc. 3 * This file is part of the GNU C Library. 4 * Copyright (c) 2011 The Chromium OS Authors. 5 * 6 * See file CREDITS for list of people who contributed to this 7 * project. 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License as 11 * published by the Free Software Foundation; either version 2 of 12 * the License, or (at your option) any later version. 13 * 14 * This program is distributed in the hope that it will be useful, 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17 * GNU General Public License for more details. 18 * 19 * You should have received a copy of the GNU General Public License 20 * along with this program; if not, write to the Free Software 21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, 22 * MA 02111-1307 USA 23 */ 24 25 /* From glibc-2.14, sysdeps/i386/memset.c */ 26 27 #include <compiler.h> 28 #include <asm/string.h> 29 #include <linux/types.h> 30 31 typedef uint32_t op_t; 32 33 void *memset(void *dstpp, int c, size_t len) 34 { 35 int d0; 36 unsigned long int dstp = (unsigned long int) dstpp; 37 38 /* This explicit register allocation improves code very much indeed. */ 39 register op_t x asm("ax"); 40 41 x = (unsigned char) c; 42 43 /* Clear the direction flag, so filling will move forward. */ 44 asm volatile("cld"); 45 46 /* This threshold value is optimal. */ 47 if (len >= 12) { 48 /* Fill X with four copies of the char we want to fill with. */ 49 x |= (x << 8); 50 x |= (x << 16); 51 52 /* Adjust LEN for the bytes handled in the first loop. */ 53 len -= (-dstp) % sizeof(op_t); 54 55 /* 56 * There are at least some bytes to set. No need to test for 57 * LEN == 0 in this alignment loop. 58 */ 59 60 /* Fill bytes until DSTP is aligned on a longword boundary. */ 61 asm volatile( 62 "rep\n" 63 "stosb" /* %0, %2, %3 */ : 64 "=D" (dstp), "=c" (d0) : 65 "0" (dstp), "1" ((-dstp) % sizeof(op_t)), "a" (x) : 66 "memory"); 67 68 /* Fill longwords. */ 69 asm volatile( 70 "rep\n" 71 "stosl" /* %0, %2, %3 */ : 72 "=D" (dstp), "=c" (d0) : 73 "0" (dstp), "1" (len / sizeof(op_t)), "a" (x) : 74 "memory"); 75 len %= sizeof(op_t); 76 } 77 78 /* Write the last few bytes. */ 79 asm volatile( 80 "rep\n" 81 "stosb" /* %0, %2, %3 */ : 82 "=D" (dstp), "=c" (d0) : 83 "0" (dstp), "1" (len), "a" (x) : 84 "memory"); 85 86 return dstpp; 87 } 88