1/* 2 * Copyright (c) 2020, Arm Limited. All rights reserved. 3 * 4 * SPDX-License-Identifier: BSD-3-Clause 5 */ 6 7#include <asm_macros.S> 8 9 .syntax unified 10 .global memset 11 12/* ----------------------------------------------------------------------- 13 * void memset(void *dst, int val, size_t count) 14 * 15 * Copy the value of 'val' (converted to an unsigned char) into 16 * each of the first 'count' characters of the object pointed to by 'dst'. 17 * 18 * Returns the value of 'dst'. 19 * ----------------------------------------------------------------------- 20 */ 21func memset 22 cmp r2, #0 23 bxeq lr /* return if 'count' = 0 */ 24 mov r12, r0 /* keep r0 */ 25 tst r0, #3 26 beq aligned /* 4-bytes aligned */ 27 28 /* Unaligned 'dst' */ 29unaligned: 30 strb r1, [r12], #1 31 subs r2, r2, #1 32 bxeq lr /* return if 0 */ 33 tst r12, #3 34 bne unaligned /* continue while unaligned */ 35 36 /* 4-bytes aligned */ 37aligned:bfi r1, r1, #8, #8 /* propagate 'val' */ 38 bfi r1, r1, #16, #16 39 40 mov r3, r1 41 42 cmp r2, #16 43 blo less_16 44 45 push {r4, lr} 46 mov r4, r1 47 mov lr, r1 48 49 cmp r2, #32 50 blo less_32 51 52write_32: 53 stmia r12!, {r1, r3, r4, lr} /* write 32 bytes in a loop */ 54 stmia r12!, {r1, r3, r4, lr} 55 subs r2, r2, #32 56 popeq {r4, pc} /* return if 0 */ 57 cmp r2, #32 58 bhs write_32 59 60less_32:cmp r2, #16 61 stmiahs r12!, {r1, r3, r4, lr} /* write 16 bytes */ 62 popeq {r4, pc} /* return if 16 */ 63 pop {r4, lr} 64 65less_16:lsls r2, r2, #29 /* C = r2[3]; N = r2[2]; Z = r2[2:0] */ 66 stmiacs r12!, {r1, r3} /* write 8 bytes */ 67 bxeq lr /* return if 8 */ 68 strmi r1, [r12], #4 /* write 4 bytes */ 69 lsls r2, r2, #1 /* N = r2[1]; Z = r2[0] */ 70 strhmi r1, [r12], #2 /* write 2 bytes */ 71 strbne r1, [r12] /* write 1 byte */ 72 bx lr 73 74endfunc memset 75