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/* $NetBSD: bcopy.S,v 1.7 1997/10/18 05:21:44 jonathan Exp $ */
/*
* Mach Operating System
* Copyright (c) 1993 Carnegie Mellon University
* All Rights Reserved.
*
* 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 Mellon
* the rights to redistribute these changes.
*/
/*
* File: mips_bcopy.s
* Author: Chris Maeda
* Date: June 1993
*
* Fast copy routine. Derived from aligned_block_copy.
*/
#include <mips/asm.h>
#define _LOCORE /* XXX not really, just assembly-code source */
#include <machine/endian.h>
#if defined(LIBC_SCCS) && !defined(lint)
ASMSTR("from: @(#)mips_bcopy.s 2.2 CMU 18/06/93")
ASMSTR("$NetBSD: bcopy.S,v 1.7 1997/10/18 05:21:44 jonathan Exp $")
#endif /* LIBC_SCCS and not lint */
#ifdef ABICALLS
.abicalls
#endif
/*
* bcopy(caddr_t src, caddr_t dst, unsigned int len)
*
* a0 src address
* a1 dst address
* a2 length
*/
LEAF(bcopy)
.set noat
.set noreorder
/*
* Make sure we can copy forwards.
*/
sltu t0,a0,a1 # t0 == a0 < a1
addu a3,a0,a2 # a3 == end of source
sltu t1,a1,a3 # t1 == a1 < a0+a2
and t2,t0,t1 # overlap -- copy backwards
bne t2,zero,backcopy
/*
* There are four alignment cases (with frequency)
* (Based on measurements taken with a DECstation 5000/200
* inside a Mach kernel.)
*
* aligned -> aligned (mostly)
* unaligned -> aligned (sometimes)
* aligned,unaligned -> unaligned (almost never)
*
* Note that we could add another case that checks if
* the destination and source are unaligned but the
* copy is alignable. eg if src and dest are both
* on a halfword boundary.
*/
andi t1,a1,3 # get last 3 bits of dest
bne t1,zero,bytecopy
andi t0,a0,3 # get last 3 bits of src
bne t0,zero,destaligned
/*
* Forward aligned->aligned copy, 8*4 bytes at a time.
*/
li AT,-32
and t0,a2,AT /* count truncated to multiple of 32 */
addu a3,a0,t0 /* run fast loop up to this address */
sltu AT,a0,a3 /* any work to do? */
beq AT,zero,wordcopy
subu a2,t0
/*
* loop body
*/
cp:
lw v0,0(a0)
lw v1,4(a0)
lw t0,8(a0)
lw t1,12(a0)
addu a0,32
sw v0,0(a1)
sw v1,4(a1)
sw t0,8(a1)
sw t1,12(a1)
lw t1,-4(a0)
lw t0,-8(a0)
lw v1,-12(a0)
lw v0,-16(a0)
addu a1,32
sw t1,-4(a1)
sw t0,-8(a1)
sw v1,-12(a1)
bne a0,a3,cp
sw v0,-16(a1)
/*
* Copy a word at a time, no loop unrolling.
*/
wordcopy:
andi t2,a2,3 # get byte count / 4
subu t2,a2,t2 # t2 = number of words to copy * 4
beq t2,zero,bytecopy
addu t0,a0,t2 # stop at t0
subu a2,a2,t2
1:
lw v0,0(a0)
addu a0,4
sw v0,0(a1)
bne a0,t0,1b
addu a1,4
bytecopy:
beq a2,zero,copydone # nothing left to do?
nop
2:
lb v0,0(a0)
addu a0,1
sb v0,0(a1)
subu a2,1
bgtz a2,2b
addu a1,1
copydone:
j ra
nop
/*
* Copy from unaligned source to aligned dest.
*/
destaligned:
andi t0,a2,3 # t0 = bytecount mod 4
subu a3,a2,t0 # number of words to transfer
beq a3,zero,bytecopy
nop
move a2,t0 # this many to do after we are done
addu a3,a0,a3 # stop point
3:
LWHI v0,0(a0)
LWLO v0,3(a0)
addi a0,4
sw v0,0(a1)
bne a0,a3,3b
addi a1,4
j bytecopy
nop
/*
* Copy by bytes backwards.
*/
backcopy:
blez a2,copydone # nothing left to do?
addu t0,a0,a2 # end of source
addu t1,a1,a2 # end of destination
4:
lb v0,-1(t0)
subu t0,1
sb v0,-1(t1)
bne t0,a0,4b
subu t1,1
j ra
nop
.set reorder
.set at
END(bcopy)
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