85 lines
3.2 KiB
ArmAsm
85 lines
3.2 KiB
ArmAsm
/* $NetBSD: bzero.S,v 1.4 1996/11/30 02:06:29 jtc Exp $ */
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/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* the Systems Programming Group of the University of Utah Computer
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* Science Department.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "DEFS.h"
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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RCSID("from: @(#)bzero.s 5.1 (Berkeley) 5/12/90")
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#else
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RCSID("$NetBSD: bzero.S,v 1.4 1996/11/30 02:06:29 jtc Exp $")
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#endif
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#endif /* LIBC_SCCS and not lint */
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/*
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* This is probably not the best we can do, but it is still much
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* faster than the C version in the portable gen directory.
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*
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* Things that might help:
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* - unroll the longword loop (might not be good for a 68020)
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* - longword, as opposed to word, align when possible (only on the 68020)
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* - use nested DBcc instructions or use one and limit size to 64K
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*/
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ENTRY(bzero)
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movl sp@(4),a0 | destination
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movl sp@(8),d0 | count
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beq Lbzdone | nothing to do
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movl a0,d1
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btst #0,d1 | address odd?
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beq Lbzeven | no, skip alignment
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clrb a0@+ | yes, clear a byte
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subql #1,d0 | adjust count
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beq Lbzdone | if zero, all done
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Lbzeven:
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movl d0,d1
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lsrl #2,d1 | convert to longword count
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beq Lbzbloop | no longwords, skip loop
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Lbzlloop:
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clrl a0@+ | clear a longword
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subql #1,d1 | adjust count
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bne Lbzlloop | still more, keep going
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andl #3,d0 | what remains
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beq Lbzdone | nothing, all done
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Lbzbloop:
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clrb a0@+ | clear a byte
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subql #1,d0 | adjust count
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bne Lbzbloop | still more, keep going
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Lbzdone:
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rts
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