1/* $OpenBSD: bzero.S,v 1.2 2004/08/13 13:07:24 pefo Exp $ */ 2/*- 3 * Copyright (c) 1991, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * This code is derived from software contributed to Berkeley by 7 * Ralph Campbell. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 35#include "DEFS.h" 36 37 38/* 39 * bzero(s1, n) 40 */ 41LEAF(bzero) 42ALEAF(blkclr) 43 .set noreorder 44 blt a1, 12, smallclr # small amount to clear? 45 subu a3, zero, a0 # compute # bytes to word align address 46 and a3, a3, 3 47 beq a3, zero, 1f # skip if word aligned 48 subu a1, a1, a3 # subtract from remaining count 49 SWHI zero, 0(a0) # clear 1, 2, or 3 bytes to align 50 addu a0, a0, a3 511: 52 and v0, a1, 3 # compute number of words left 53 subu a3, a1, v0 54 move a1, v0 55 addu a3, a3, a0 # compute ending address 562: 57 addu a0, a0, 4 # clear words 58 bne a0, a3, 2b # unrolling loop does not help 59 sw zero, -4(a0) # since we are limited by memory speed 60smallclr: 61 ble a1, zero, 2f 62 addu a3, a1, a0 # compute ending address 631: 64 addu a0, a0, 1 # clear bytes 65 bne a0, a3, 1b 66 sb zero, -1(a0) 672: 68 j ra 69 nop 70END(bzero) 71 72