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