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/* $NetBSD: bzero.S,v 1.1 1995/10/20 01:16:02 cgd Exp $ */
/*
* Copyright (c) 1995 Carnegie-Mellon University.
* All rights reserved.
*
* Author: Trevor Blackwell
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
#include "DEFS.h"
LEAF(bzero,2)
ble a1,bzero_done
bic a1,63,t3 /* t3 is # bytes to do 64 bytes at a time */
/* If nothing in first word, ignore it */
subq zero,a0,t0
and t0,7,t0 /* t0 = (0-size)%8 */
beq t0,bzero_nostart1
cmpult a1,t0,t1 /* if size > size%8 goto noshort */
beq t1,bzero_noshort
/*
* The whole thing is less than a word.
* Mask off 1..7 bytes, and finish.
*/
ldq_u t2,0(a0)
lda t0,-1(zero) /* t0=-1 */
mskql t0,a1,t0 /* Get ff in bytes (a0%8)..((a0+a1-1)%8) */
insql t0,a0,t0
bic t2,t0,t2 /* zero those bytes in word */
stq_u t2,0(a0)
RET
bzero_noshort:
/* Handle the first partial word */
ldq_u t2,0(a0)
subq a1,t0,a1
mskql t2,a0,t2 /* zero bytes (a0%8)..7 in word */
stq_u t2,0(a0)
addq a0,t0,a0 /* round a0 up to next word */
bic a1,63,t3 /* recalc t3 (# bytes to do 64 bytes at a
time) */
bzero_nostart1:
/*
* Loop, zeroing 64 bytes at a time
*/
beq t3,bzero_lp_done
bzero_lp:
stq zero,0(a0)
stq zero,8(a0)
stq zero,16(a0)
stq zero,24(a0)
subq t3,64,t3
stq zero,32(a0)
stq zero,40(a0)
stq zero,48(a0)
stq zero,56(a0)
addq a0,64,a0
bne t3,bzero_lp
bzero_lp_done:
/*
* Handle the last 0..7 words.
* We mask off the low bits, so we don't need an extra
* compare instruction for the loop (just a bne. heh-heh)
*/
and a1,0x38,t4
beq t4,bzero_finish_lp_done
bzero_finish_lp:
stq zero,0(a0)
subq t4,8,t4
addq a0,8,a0
bne t4,bzero_finish_lp
/* Do the last partial word */
bzero_finish_lp_done:
and a1,7,t5 /* 0..7 bytes left */
beq t5,bzero_done /* mskqh won't change t0 if t5==0, but I
don't want to touch, say, a new VM page */
ldq t0,0(a0)
mskqh t0,t5,t0
stq t0,0(a0)
bzero_done:
RET
END(bzero)
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