| Gabe Black | dbaef6e | 2011-11-14 14:47:18 +0000 | [diff] [blame] | 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 | } |