bzero.S revision 1.1.94.2
1 /* $NetBSD: bzero.S,v 1.1.94.2 2020/04/21 19:37:47 martin Exp $ */ 2 3 /* 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This software was developed by the Computer Systems Engineering group 8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 9 * contributed to Berkeley. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR 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 * from: Header: bzero.s,v 1.1 92/06/25 12:52:46 torek Exp 36 */ 37 38 #include <machine/asm.h> 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 .asciz "@(#)bzero.s 8.1 (Berkeley) 6/4/93" 42 #else 43 RCSID("$NetBSD: bzero.S,v 1.1.94.2 2020/04/21 19:37:47 martin Exp $") 44 #endif 45 #endif /* LIBC_SCCS and not lint */ 46 47 /* 48 * We should unroll the loop, but at the moment this would 49 * gain nothing since the `std' instructions are what limits us. 50 */ 51 52 #ifdef MEMSET 53 /* 54 * void * 55 * memset(void *addr, int pattern, size_t len) 56 */ 57 ENTRY(memset) 58 ! %o0 = addr, %o1 = pattern, %o2 = len 59 /* 60 * Expand the byte pattern to fill 64 bits in an even-aligned 61 * register pair; shuffle arguments to match those of bzero. 62 */ 63 and %o1, 0xff, %o3 64 mov %o2, %o1 ! shuffle argument 65 sll %o3, 8, %o2 66 or %o2, %o3, %o2 67 mov %o0, %g1 ! save original pointer 68 sll %o2, 16, %o3 69 or %o2, %o3, %o2 70 ! Optimize a common case: addr and len are both multiples of 8. 71 or %o0, %o1, %o5 72 btst 7, %o5 ! ((addr | len) & 7) != 0? 73 bnz 1f ! if so, cannot optimize 74 mov %o2, %o3 ! in any case, complete pat expansion 75 #else 76 /* 77 * void 78 * bzero(void *addr, size_t len) 79 */ 80 ENTRY(bzero) 81 ! %o0 = addr, %o1 = len 82 83 clr %o2 84 ! Optimize a common case: addr and len are both multiples of 8. 85 or %o0, %o1, %o5 86 btst 7, %o5 ! ((addr | len) & 7) != 0? 87 bnz 1f ! if so, cannot optimize 88 clr %o3 ! in any case, we want o3=0 89 #endif 90 91 /* `Good' operands, can just store doubles. */ 92 0: 93 deccc 8, %o1 ! while ((len -= 8) >= 0) 94 bge,a 0b 95 std %o2, [%o0 + %o1] ! *(quad *)(addr + len) = 0; 96 retl 97 nop 98 99 /* 100 * Either the address is unaligned, or the count is not a 101 * multiple of 8, or both. We will have to align the address 102 * in order to use anything `better' than stb. 103 */ 104 1: 105 cmp %o1, 15 ! len >= 15? 106 bge,a Lstd ! yes, use std 107 btst 1, %o0 ! (but first check alignment) 108 109 ! not enough to bother: do byte-at-a-time loop. 110 2: 111 deccc %o1 ! while (--len >= 0) 112 bge,a 2b 113 stb %o2, [%o0 + %o1] ! addr[len] = 0; 114 retl 115 nop 116 117 Lstd: 118 /* 119 * There are at least 15 bytes to zero. 120 * We may have to zero some initial stuff to align 121 * the address. 122 */ 123 bz,a 1f ! if (addr & 1) { 124 btst 2, %o0 125 stb %o2, [%o0] ! *addr = 0; 126 inc %o0 ! addr++; 127 dec %o1 ! len--; 128 btst 2, %o0 ! } 129 1: 130 bz,a 1f ! if (addr & 2) { 131 btst 4, %o0 132 sth %o2, [%o0] ! *(short *)addr = 0; 133 inc 2, %o0 ! addr += 2; 134 dec 2, %o1 ! len -= 2; 135 btst 4, %o0 ! } 136 1: 137 bz 1f ! if (addr & 4) { 138 dec 8, %o1 139 st %o2, [%o0] ! *(int *)addr = 0; 140 inc 4, %o0 ! addr += 4; 141 dec 4, %o1 ! len -= 4; 142 ! } 143 /* 144 * Address is double word aligned; len is 8 less than 145 * the number of bytes remaining (i.e., len is 0 if 146 * the remaining count is 8, 1 if it is 9, etc.). 147 */ 148 1: 149 std %o2, [%o0] ! do { 150 2: ! *(quad *)addr = 0; 151 inc 8, %o0 ! addr += 8; 152 deccc 8, %o1 ! } while ((len -= 8) >= 0); 153 bge,a 2b 154 std %o2, [%o0] 155 156 /* 157 * Len is in [-8..-1] where -8 => done, -7 => 1 byte to zero, 158 * -6 => two bytes, etc. Mop up this remainder, if any. 159 */ 160 btst 4, %o1 161 bz 1f ! if (len & 4) { 162 btst 2, %o1 163 st %o2, [%o0] ! *(int *)addr = 0; 164 inc 4, %o0 ! addr += 4; 165 1: 166 bz 1f ! if (len & 2) { 167 btst 1, %o1 168 sth %o2, [%o0] ! *(short *)addr = 0; 169 inc 2, %o0 ! addr += 2; 170 1: 171 bnz,a 1f ! if (len & 1) 172 stb %o2, [%o0] ! *addr = 0; 173 1: 174 retl 175 #ifdef MEMSET 176 mov %g1, %o0 ! restore original pointer 177 #else 178 nop 179 #endif 180
Indexes created Sat Sep 20 22:09:52 GMT 2025