1 /* $OpenBSD: memset.S,v 1.4 2015年06月08日 14:22:05 jsg Exp $ */ 2 /* $NetBSD: memset.S,v 1.1 2000年12月29日 20:51:57 bjh21 Exp $ */ 3 4 /* 5 * Copyright (c) 1995 Mark Brinicombe. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by Mark Brinicombe. 19 * 4. The name of the company nor the name of the author may be used to 20 * endorse or promote products derived from this software without specific 21 * prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED 24 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 25 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 26 * IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36#include <machine/asm.h> 37 38 /* 39 * Sets a block of memory to the specified value 40 * 41 * On entry: 42 * r0 - dest address 43 * r1 - byte to write 44 * r2 - number of bytes to write 45 * 46 * On exit: 47 * r0 - dest address 48 */ 49 50.syntax unified 51 52 ENTRY(memset) 53 stmfd sp!, {r0} /* Remember address for return value */ 54 and r1, r1, #0x000000ff /* We write bytes */ 55 56 cmp r2, #0x00000004 /* Do we have less than 4 bytes */ 57 blt Lmemset_lessthanfour 58 59 /* Ok first we will word align the address */ 60 61 ands r3, r0, #0x00000003 /* Get the bottom two bits */ 62 beq Lmemset_addraligned /* The address is word aligned */ 63 64 rsb r3, r3, #0x00000004 65 sub r2, r2, r3 66 cmp r3, #0x00000002 67 strb r1, [r0], #0x0001 /* Set 1 byte */ 68 strbge r1, [r0], #0x0001 /* Set another byte */ 69 strbgt r1, [r0], #0x0001 /* and a third */ 70 71 cmp r2, #0x00000004 72 blt Lmemset_lessthanfour 73 74 /* Now we must be word aligned */ 75 76 Lmemset_addraligned: 77 78 orr r3, r1, r1, lsl #8 /* Repeat the byte into a word */ 79 orr r3, r3, r3, lsl #16 80 81 /* We know we have at least 4 bytes ... */ 82 83 cmp r2, #0x00000020 /* If less than 32 then use words */ 84 blt Lmemset_lessthan32 85 86 /* We have at least 32 so lets use quad words */ 87 88 stmfd sp!, {r4-r6} /* Store registers */ 89 mov r4, r3 /* Duplicate data */ 90 mov r5, r3 91 mov r6, r3 92 93 Lmemset_loop16: 94 stmia r0!, {r3-r6} /* Store 16 bytes */ 95 sub r2, r2, #0x00000010 /* Adjust count */ 96 cmp r2, #0x00000010 /* Still got at least 16 bytes ? */ 97 bgt Lmemset_loop16 98 99 ldmfd sp!, {r4-r6} /* Restore registers */ 100 101 /* Do we need to set some words as well ? */ 102 103 cmp r2, #0x00000004 104 blt Lmemset_lessthanfour 105 106 /* Have either less than 16 or less than 32 depending on route taken */ 107 108 Lmemset_lessthan32: 109 110 /* We have at least 4 bytes so copy as words */ 111 112 Lmemset_loop4: 113 str r3, [r0], #0x0004 114 sub r2, r2, #0x0004 115 cmp r2, #0x00000004 116 bge Lmemset_loop4 117 118 Lmemset_lessthanfour: 119 cmp r2, #0x00000000 120 ldmfdeq sp!, {r0} 121 moveq pc, lr /* Zero length so exit */ 122 123 cmp r2, #0x00000002 124 strb r1, [r0], #0x0001 /* Set 1 byte */ 125 strbge r1, [r0], #0x0001 /* Set another byte */ 126 strbgt r1, [r0], #0x0001 /* and a third */ 127 128 ldmfd sp!, {r0} 129 mov pc, lr /* Exit */ 130