1/* $NetBSD: ffs.S,v 1.4 2011/07/04 11:35:26 mrg Exp $ */ 2 3/*- 4 * Copyright (c) 2010 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Matt Thomas of 3am Software Foundry. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32#include <mips/asm.h> 33 34RCSID("$NetBSD: ffs.S,v 1.4 2011/07/04 11:35:26 mrg Exp $") 35 36/* bit = ffs(value) */ 37 38 .text 39 .set noreorder 40 41WEAK_ALIAS(__ffssi2,ffs) 42#if __mips == 64 || __mips == 32 43LEAF(ffs) 44#ifndef _LP64 45XLEAF(ffsl) 46#endif 47 .set push 48 .set mips32 49 li v1, 32 50#if __mips == 64 51 sll a0, a0, 0 52#endif 53 negu a1, a0 54 and a0, a1 55 clz v0, a0 56 j ra 57 subu v0, v1, v0 58 .set pop 59END(ffs) 60#if defined(_LP64) && __mips == 64 61LEAF(ffsl) 62 li v1, 64 63 negu a1, a0 64 and a0, a1 65 dclz v0, a0 66 j ra 67 subu v0, v1, v0 68END(ffsl) 69#endif 70#else /* __mips != 64 && __mips != 32 */ 71 72#ifdef _LP64 73XLEAF(ffsl) 74 beqz a0, 6f # fast escape if 0 75 li v0, 0 76 77 li v0, 1 78 li a3, 0xffffffff # initial mask 79 b 1f 80 li a2, 32 # bit count of mask 81#endif /* _LP64 */ 82LEAF(ffs) 83#ifndef _LP64 84XLEAF(ffsl) 85#endif /* !_LP64 */ 86 beqz a0, 6f 87 li v0, 0 88 89 li v0, 1 90 li a3, 0xffff # initial mask 91 li a2, 16 # bit count of mask 921: 93 and v1, a0, a3 # focus no lower half of bits left 94 bnez v1, 2f # any of the lower half set? 95 nop 96 addu v0, a2 # nope, then bit is in the upper half 97#ifdef _LP64 98 dsrlv a0, a0, a2 # discard low bits 99#else 100 srlv a0, a0, a2 # discard low bits 101#endif 1022: 103 srl a2, 1 # divide bit count by 2 104 bnez a2, 1b # still bits left to text? 105 srlv a3, a3, a2 # shrink mask in half 1066: 107 j ra 108 nop 109END(ffs) 110#endif /* __mips == 64 || __mips == 32 */ 111