| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | /* bzero -- set a block of memory to zero. For Intel 80x86, x>=3. |
| 2 | This file is part of the GNU C Library. |
| 3 | Copyright (C) 1991-2015 Free Software Foundation, Inc. |
| 4 | Contributed by Torbjorn Granlund (tege@sics.se). |
| 5 | |
| 6 | The GNU C Library is free software; you can redistribute it and/or |
| 7 | modify it under the terms of the GNU Lesser General Public |
| 8 | License as published by the Free Software Foundation; either |
| 9 | version 2.1 of the License, or (at your option) any later version. |
| 10 | |
| 11 | The GNU C Library is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | Lesser General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU Lesser General Public |
| 17 | License along with the GNU C Library; if not, see |
| 18 | <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | #include <string.h> |
| 21 | #include <memcopy.h> |
| 22 | |
| 23 | #undef bzero |
| 24 | #undef __bzero |
| 25 | |
| 26 | #ifdef __GNUC__ |
| 27 | |
| 28 | void |
| 29 | __bzero (dstpp, len) |
| 30 | void *dstpp; |
| 31 | size_t len; |
| 32 | { |
| 33 | /* N.B.: This code is almost verbatim from memset.c. */ |
| 34 | int d0; |
| 35 | unsigned long int dstp = (unsigned long int) dstpp; |
| 36 | |
| 37 | /* This explicit register allocation |
| 38 | improves code very much indeed. */ |
| 39 | register op_t x asm ("ax"); |
| 40 | |
| 41 | x = 0; |
| 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 | { |
| 49 | /* Adjust LEN for the bytes handled in the first loop. */ |
| 50 | len -= (-dstp) % OPSIZ; |
| 51 | |
| 52 | /* There are at least some bytes to set. |
| 53 | No need to test for LEN == 0 in this alignment loop. */ |
| 54 | |
| 55 | /* Fill bytes until DSTP is aligned on a longword boundary. */ |
| 56 | asm volatile ("rep\n" |
| 57 | "stosb" /* %0, %2, %3 */ : |
| 58 | "=D" (dstp), "=c" (d0) : |
| 59 | "0" (dstp), "1" ((-dstp) % OPSIZ), "a" (x) : |
| 60 | "memory"); |
| 61 | |
| 62 | /* Fill longwords. */ |
| 63 | asm volatile ("rep\n" |
| 64 | "stosl" /* %0, %2, %3 */ : |
| 65 | "=D" (dstp), "=c" (d0) : |
| 66 | "0" (dstp), "1" (len / OPSIZ), "a" (x) : |
| 67 | "memory"); |
| 68 | len %= OPSIZ; |
| 69 | } |
| 70 | |
| 71 | /* Write the last few bytes. */ |
| 72 | asm volatile ("rep\n" |
| 73 | "stosb" /* %0, %2, %3 */ : |
| 74 | "=D" (dstp), "=c" (d0) : |
| 75 | "0" (dstp), "c" (len), "a" (x) : |
| 76 | "memory"); |
| 77 | } |
| 78 | weak_alias (__bzero, bzero) |
| 79 | |
| 80 | #else |
| 81 | #include <string/bzero.c> |
| 82 | #endif |