1/* $NetBSD: bzero.S,v 1.10 2009/12/14 02:53:52 matt Exp $ */ 2 3/*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Ralph Campbell. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35#include <machine/asm.h> 36__FBSDID("$FreeBSD$"); 37 38#if defined(LIBC_SCCS) && !defined(lint) 39#if 0 40 ASMSTR("from: @(#)bzero.s 8.1 (Berkeley) 6/4/93") 41#else 42 ASMSTR("$NetBSD: bzero.S,v 1.10 2009/12/14 02:53:52 matt Exp $") 43#endif 44#endif /* LIBC_SCCS and not lint */ 45 46#define _LOCORE /* XXX not really, just assembly-code source */ 47#include <machine/endian.h> 48 49#ifdef __ABICALLS__ 50 .abicalls 51#endif 52 53/* bzero(s1, n) */ 54 55LEAF(bzero) 56 .set noreorder 57 blt a1, 3*SZREG, smallclr # small amount to clear? 58 PTR_SUBU a3, zero, a0 # compute # bytes to word align address 59 and a3, a3, SZREG-1 60 beq a3, zero, 1f # skip if word aligned 61#if SZREG == 4 62 PTR_SUBU a1, a1, a3 # subtract from remaining count 63 SWHI zero, 0(a0) # clear 1, 2, or 3 bytes to align 64 PTR_ADDU a0, a0, a3 65#endif 66#if SZREG == 8 67 PTR_SUBU a1, a1, a3 # subtract from remaining count 68 PTR_ADDU a0, a0, a3 # align dst to next word 69 sll a3, a3, 3 # bits to bytes 70 li a2, -1 # make a mask 71#if _BYTE_ORDER == _BIG_ENDIAN 72 REG_SRLV a2, a2, a3 # we want to keep the MSB bytes 73#endif 74#if _BYTE_ORDER == _LITTLE_ENDIAN 75 REG_SLLV a2, a2, a3 # we want to keep the LSB bytes 76#endif 77 nor a2, zero, a2 # complement the mask 78 REG_L v0, -SZREG(a0) # load the word to partially clear 79 and v0, v0, a2 # clear the bytes 80 REG_S v0, -SZREG(a0) # store it back 81#endif 821: 83 and v0, a1, SZREG-1 # compute number of words left 84 PTR_SUBU a3, a1, v0 85 move a1, v0 86 PTR_ADDU a3, a3, a0 # compute ending address 872: 88 PTR_ADDU a0, a0, SZREG # clear words 89 bne a0, a3, 2b # unrolling loop doesnt help 90 REG_S zero, -SZREG(a0) # since we are limited by memory speed 91smallclr: 92 ble a1, zero, 2f 93 PTR_ADDU a3, a1, a0 # compute ending address 941: 95 PTR_ADDU a0, a0, 1 # clear bytes 96 bne a0, a3, 1b 97 sb zero, -1(a0) 982: 99 j ra 100 nop 101END(bzero) 102