| /* SPDX-License-Identifier: GPL-2.0-or-later */ |
| /* This file is part of the coreboot project. */ |
| |
| /* 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; |
| } |