1*37c9f0a6Schristos/* $NetBSD: bzero.S,v 1.1 2005/12/20 19:28:49 christos Exp $ */ 2*37c9f0a6Schristos 3*37c9f0a6Schristos/* 4*37c9f0a6Schristos * Copyright (c) 1995 Carnegie-Mellon University. 5*37c9f0a6Schristos * All rights reserved. 6*37c9f0a6Schristos * 7*37c9f0a6Schristos * Author: Trevor Blackwell 8*37c9f0a6Schristos * 9*37c9f0a6Schristos * Permission to use, copy, modify and distribute this software and 10*37c9f0a6Schristos * its documentation is hereby granted, provided that both the copyright 11*37c9f0a6Schristos * notice and this permission notice appear in all copies of the 12*37c9f0a6Schristos * software, derivative works or modified versions, and any portions 13*37c9f0a6Schristos * thereof, and that both notices appear in supporting documentation. 14*37c9f0a6Schristos * 15*37c9f0a6Schristos * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 16*37c9f0a6Schristos * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 17*37c9f0a6Schristos * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 18*37c9f0a6Schristos * 19*37c9f0a6Schristos * Carnegie Mellon requests users of this software to return to 20*37c9f0a6Schristos * 21*37c9f0a6Schristos * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 22*37c9f0a6Schristos * School of Computer Science 23*37c9f0a6Schristos * Carnegie Mellon University 24*37c9f0a6Schristos * Pittsburgh PA 15213-3890 25*37c9f0a6Schristos * 26*37c9f0a6Schristos * any improvements or extensions that they make and grant Carnegie the 27*37c9f0a6Schristos * rights to redistribute these changes. 28*37c9f0a6Schristos */ 29*37c9f0a6Schristos 30*37c9f0a6Schristos#include <machine/asm.h> 31*37c9f0a6Schristos 32*37c9f0a6SchristosLEAF(bzero,2) 33*37c9f0a6Schristos ble a1,bzero_done 34*37c9f0a6Schristos bic a1,63,t3 /* t3 is # bytes to do 64 bytes at a time */ 35*37c9f0a6Schristos 36*37c9f0a6Schristos /* If nothing in first word, ignore it */ 37*37c9f0a6Schristos subq zero,a0,t0 38*37c9f0a6Schristos and t0,7,t0 /* t0 = (0-size)%8 */ 39*37c9f0a6Schristos beq t0,bzero_nostart1 40*37c9f0a6Schristos 41*37c9f0a6Schristos cmpult a1,t0,t1 /* if size > size%8 goto noshort */ 42*37c9f0a6Schristos beq t1,bzero_noshort 43*37c9f0a6Schristos 44*37c9f0a6Schristos /* 45*37c9f0a6Schristos * The whole thing is less than a word. 46*37c9f0a6Schristos * Mask off 1..7 bytes, and finish. 47*37c9f0a6Schristos */ 48*37c9f0a6Schristos ldq_u t2,0(a0) 49*37c9f0a6Schristos lda t0,-1(zero) /* t0=-1 */ 50*37c9f0a6Schristos mskql t0,a1,t0 /* Get ff in bytes (a0%8)..((a0+a1-1)%8) */ 51*37c9f0a6Schristos insql t0,a0,t0 52*37c9f0a6Schristos bic t2,t0,t2 /* zero those bytes in word */ 53*37c9f0a6Schristos stq_u t2,0(a0) 54*37c9f0a6Schristos RET 55*37c9f0a6Schristos 56*37c9f0a6Schristosbzero_noshort: 57*37c9f0a6Schristos /* Handle the first partial word */ 58*37c9f0a6Schristos ldq_u t2,0(a0) 59*37c9f0a6Schristos subq a1,t0,a1 60*37c9f0a6Schristos mskql t2,a0,t2 /* zero bytes (a0%8)..7 in word */ 61*37c9f0a6Schristos stq_u t2,0(a0) 62*37c9f0a6Schristos 63*37c9f0a6Schristos addq a0,t0,a0 /* round a0 up to next word */ 64*37c9f0a6Schristos bic a1,63,t3 /* recalc t3 (# bytes to do 64 bytes at a 65*37c9f0a6Schristos time) */ 66*37c9f0a6Schristos 67*37c9f0a6Schristosbzero_nostart1: 68*37c9f0a6Schristos /* 69*37c9f0a6Schristos * Loop, zeroing 64 bytes at a time 70*37c9f0a6Schristos */ 71*37c9f0a6Schristos beq t3,bzero_lp_done 72*37c9f0a6Schristosbzero_lp: 73*37c9f0a6Schristos stq zero,0(a0) 74*37c9f0a6Schristos stq zero,8(a0) 75*37c9f0a6Schristos stq zero,16(a0) 76*37c9f0a6Schristos stq zero,24(a0) 77*37c9f0a6Schristos subq t3,64,t3 78*37c9f0a6Schristos stq zero,32(a0) 79*37c9f0a6Schristos stq zero,40(a0) 80*37c9f0a6Schristos stq zero,48(a0) 81*37c9f0a6Schristos stq zero,56(a0) 82*37c9f0a6Schristos addq a0,64,a0 83*37c9f0a6Schristos bne t3,bzero_lp 84*37c9f0a6Schristos 85*37c9f0a6Schristosbzero_lp_done: 86*37c9f0a6Schristos /* 87*37c9f0a6Schristos * Handle the last 0..7 words. 88*37c9f0a6Schristos * We mask off the low bits, so we don't need an extra 89*37c9f0a6Schristos * compare instruction for the loop (just a bne. heh-heh) 90*37c9f0a6Schristos */ 91*37c9f0a6Schristos and a1,0x38,t4 92*37c9f0a6Schristos beq t4,bzero_finish_lp_done 93*37c9f0a6Schristosbzero_finish_lp: 94*37c9f0a6Schristos stq zero,0(a0) 95*37c9f0a6Schristos subq t4,8,t4 96*37c9f0a6Schristos addq a0,8,a0 97*37c9f0a6Schristos bne t4,bzero_finish_lp 98*37c9f0a6Schristos 99*37c9f0a6Schristos /* Do the last partial word */ 100*37c9f0a6Schristosbzero_finish_lp_done: 101*37c9f0a6Schristos and a1,7,t5 /* 0..7 bytes left */ 102*37c9f0a6Schristos beq t5,bzero_done /* mskqh won't change t0 if t5==0, but I 103*37c9f0a6Schristos don't want to touch, say, a new VM page */ 104*37c9f0a6Schristos ldq t0,0(a0) 105*37c9f0a6Schristos mskqh t0,t5,t0 106*37c9f0a6Schristos stq t0,0(a0) 107*37c9f0a6Schristosbzero_done: 108*37c9f0a6Schristos RET 109*37c9f0a6Schristos 110*37c9f0a6Schristos END(bzero) 111