92 lines
2.7 KiB
ArmAsm
92 lines
2.7 KiB
ArmAsm
/* $NetBSD: ffs.S,v 1.3 1996/10/17 03:08:13 cgd Exp $ */
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/*
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* Copyright (c) 1995 Christopher G. Demetriou
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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. 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 Christopher G. Demetriou
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* for the NetBSD Project.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific 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 BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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LEAF(ffs, 1)
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addl a0, 0, t0
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beq t0, Lallzero
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/*
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* Initialize return value (v0), and set up t1 so that it
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* contains the mask with only the lowest bit set.
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*/
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subl zero, t0, t1
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ldil v0, 1
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and t0, t1, t1
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and t1, 0xff, t2
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bne t2, Ldo8
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/*
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* If lower 16 bits empty, add 16 to result and use upper 16.
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*/
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zapnot t1, 0x03, t3
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bne t3, Ldo16
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sra t1, 16, t1
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addl v0, 16, v0
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Ldo16:
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/*
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* If lower 8 bits empty, add 8 to result and use upper 8.
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*/
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and t1, 0xff, t4
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bne t4, Ldo8
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sra t1, 8, t1
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addl v0, 8, v0
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Ldo8:
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and t1, 0x0f, t5 /* lower 4 of 8 empty? */
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and t1, 0x33, t6 /* lower 2 of each 4 empty? */
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and t1, 0x55, t7 /* lower 1 of each 2 empty? */
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/* If lower 4 bits empty, add 4 to result. */
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bne t5, Ldo4
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addl v0, 4, v0
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Ldo4: /* If lower 2 bits of each 4 empty, add 2 to result. */
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bne t6, Ldo2
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addl v0, 2, v0
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Ldo2: /* If lower bit of each 2 empty, add 1 to result. */
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bne t7, Ldone
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addl v0, 1, v0
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Ldone:
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RET
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Lallzero:
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bis zero, zero, v0
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RET
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END(ffs)
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