4e76e4c301
This is all code only run on ARMv4 and ARMv5. Support for these have been dropped from FreeBSD. Differential Revision: https://reviews.freebsd.org/D28314
58 lines
2.2 KiB
ArmAsm
58 lines
2.2 KiB
ArmAsm
/* $NetBSD: ffs.S,v 1.5 2003/04/05 23:08:52 bjh21 Exp $ */
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/*
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* Copyright (c) 2001 Christopher Gilbert
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* All rights reserved.
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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. The name of the company nor the name of the author may be used to
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* endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* 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 <machine/asm.h>
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__FBSDID("$FreeBSD$");
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.syntax unified
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/*
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* ffs - find first set bit, this algorithm isolates the first set
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* bit, then multiplies the number by 0x0450fbaf which leaves the top
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* 6 bits as an index into the table. This algorithm should be a win
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* over the checking each bit in turn as per the C compiled version.
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*
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* This is the ffs algorithm devised by d.seal and posted to comp.sys.arm on
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* 16 Feb 1994.
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*/
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ENTRY(ffs)
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/* Standard trick to isolate bottom bit in r0 or 0 if r0 = 0 on entry */
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rsb r1, r0, #0
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ands r0, r0, r1
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itt ne
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clzne r0, r0
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rsbne r0, r0, #32
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RET
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END(ffs)
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.section .note.GNU-stack,"",%progbits
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