1/* $NetBSD: bzero.S,v 1.1 2005/12/20 19:28:49 christos Exp $ */ 2 3/* 4 * Copyright (c) 1995 Carnegie-Mellon University. 5 * All rights reserved. 6 * 7 * Author: Trevor Blackwell 8 * 9 * Permission to use, copy, modify and distribute this software and 10 * its documentation is hereby granted, provided that both the copyright 11 * notice and this permission notice appear in all copies of the 12 * software, derivative works or modified versions, and any portions 13 * thereof, and that both notices appear in supporting documentation. 14 * 15 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 16 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 17 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 18 * 19 * Carnegie Mellon requests users of this software to return to 20 * 21 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 22 * School of Computer Science 23 * Carnegie Mellon University 24 * Pittsburgh PA 15213-3890 25 * 26 * any improvements or extensions that they make and grant Carnegie the 27 * rights to redistribute these changes. 28 */ 29 30#include <machine/asm.h> 31 32LEAF(bzero,2) 33 ble a1,bzero_done 34 bic a1,63,t3 /* t3 is # bytes to do 64 bytes at a time */ 35 36 /* If nothing in first word, ignore it */ 37 subq zero,a0,t0 38 and t0,7,t0 /* t0 = (0-size)%8 */ 39 beq t0,bzero_nostart1 40 41 cmpult a1,t0,t1 /* if size > size%8 goto noshort */ 42 beq t1,bzero_noshort 43 44 /* 45 * The whole thing is less than a word. 46 * Mask off 1..7 bytes, and finish. 47 */ 48 ldq_u t2,0(a0) 49 lda t0,-1(zero) /* t0=-1 */ 50 mskql t0,a1,t0 /* Get ff in bytes (a0%8)..((a0+a1-1)%8) */ 51 insql t0,a0,t0 52 bic t2,t0,t2 /* zero those bytes in word */ 53 stq_u t2,0(a0) 54 RET 55 56bzero_noshort: 57 /* Handle the first partial word */ 58 ldq_u t2,0(a0) 59 subq a1,t0,a1 60 mskql t2,a0,t2 /* zero bytes (a0%8)..7 in word */ 61 stq_u t2,0(a0) 62 63 addq a0,t0,a0 /* round a0 up to next word */ 64 bic a1,63,t3 /* recalc t3 (# bytes to do 64 bytes at a 65 time) */ 66 67bzero_nostart1: 68 /* 69 * Loop, zeroing 64 bytes at a time 70 */ 71 beq t3,bzero_lp_done 72bzero_lp: 73 stq zero,0(a0) 74 stq zero,8(a0) 75 stq zero,16(a0) 76 stq zero,24(a0) 77 subq t3,64,t3 78 stq zero,32(a0) 79 stq zero,40(a0) 80 stq zero,48(a0) 81 stq zero,56(a0) 82 addq a0,64,a0 83 bne t3,bzero_lp 84 85bzero_lp_done: 86 /* 87 * Handle the last 0..7 words. 88 * We mask off the low bits, so we don't need an extra 89 * compare instruction for the loop (just a bne. heh-heh) 90 */ 91 and a1,0x38,t4 92 beq t4,bzero_finish_lp_done 93bzero_finish_lp: 94 stq zero,0(a0) 95 subq t4,8,t4 96 addq a0,8,a0 97 bne t4,bzero_finish_lp 98 99 /* Do the last partial word */ 100bzero_finish_lp_done: 101 and a1,7,t5 /* 0..7 bytes left */ 102 beq t5,bzero_done /* mskqh won't change t0 if t5==0, but I 103 don't want to touch, say, a new VM page */ 104 ldq t0,0(a0) 105 mskqh t0,t5,t0 106 stq t0,0(a0) 107bzero_done: 108 RET 109 110 END(bzero) 111