1*080852e7Smrg/* $NetBSD: ffs.S,v 1.3 2011/07/04 12:18:05 mrg Exp $ */ 237c9f0a6Schristos 337c9f0a6Schristos/*- 437c9f0a6Schristos * Copyright (c) 2002 The NetBSD Foundation, Inc. 537c9f0a6Schristos * All rights reserved. 637c9f0a6Schristos * 737c9f0a6Schristos * This code is derived from software contributed to The NetBSD Foundation 837c9f0a6Schristos * by ITOH Yasufumi. 937c9f0a6Schristos * 1037c9f0a6Schristos * Redistribution and use in source and binary forms, with or without 1137c9f0a6Schristos * modification, are permitted provided that the following conditions 1237c9f0a6Schristos * are met: 1337c9f0a6Schristos * 1. Redistributions of source code must retain the above copyright 1437c9f0a6Schristos * notice, this list of conditions and the following disclaimer. 1537c9f0a6Schristos * 2. Redistributions in binary form must reproduce the above copyright 1637c9f0a6Schristos * notice, this list of conditions and the following disclaimer in the 1737c9f0a6Schristos * documentation and/or other materials provided with the distribution. 1837c9f0a6Schristos * 1937c9f0a6Schristos * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 2037c9f0a6Schristos * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 2137c9f0a6Schristos * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 2237c9f0a6Schristos * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 2337c9f0a6Schristos * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 2437c9f0a6Schristos * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 2537c9f0a6Schristos * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 2637c9f0a6Schristos * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 2737c9f0a6Schristos * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 2837c9f0a6Schristos * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 2937c9f0a6Schristos * POSSIBILITY OF SUCH DAMAGE. 3037c9f0a6Schristos */ 3137c9f0a6Schristos 3237c9f0a6Schristos#include <machine/asm.h> 3337c9f0a6Schristos 3437c9f0a6Schristos#if defined(LIBC_SCCS) && !defined(lint) 35*080852e7Smrg RCSID("$NetBSD: ffs.S,v 1.3 2011/07/04 12:18:05 mrg Exp $") 3637c9f0a6Schristos#endif 3737c9f0a6Schristos 3837c9f0a6Schristos/* 3937c9f0a6Schristos * ffs - find first bit set 4037c9f0a6Schristos * 4137c9f0a6Schristos * This code makes use of ``test 8bit'' and ``shift 8bit'' instructions. 4237c9f0a6Schristos * The remaining 8bit is tested in every 2bit. 4337c9f0a6Schristos */ 4437c9f0a6Schristos 45*080852e7SmrgWEAK_ALIAS(__ffssi2,ffs) 4637c9f0a6SchristosENTRY(ffs) 4737c9f0a6Schristos mov r4,r0 ! using r0 specific instructions 4837c9f0a6Schristos tst #0xff,r0 4937c9f0a6Schristos bf/s L8bit 5037c9f0a6Schristos mov #0+1,r1 ! ret = 1..8 5137c9f0a6Schristos 5237c9f0a6Schristos tst r0,r0 ! ffs(0) is 0 5337c9f0a6Schristos bt Lzero ! testing here to accelerate ret=1..8 cases 5437c9f0a6Schristos 5537c9f0a6Schristos shlr8 r0 5637c9f0a6Schristos tst #0xff,r0 5737c9f0a6Schristos bf/s L8bit 5837c9f0a6Schristos mov #8+1,r1 ! ret = 9..16 5937c9f0a6Schristos 6037c9f0a6Schristos shlr8 r0 6137c9f0a6Schristos tst #0xff,r0 6237c9f0a6Schristos bf/s L8bit 6337c9f0a6Schristos mov #16+1,r1 ! ret = 17..24 6437c9f0a6Schristos 6537c9f0a6Schristos shlr8 r0 6637c9f0a6Schristos mov #24+1,r1 ! ret = 25..32 6737c9f0a6Schristos 6837c9f0a6SchristosL8bit: 6937c9f0a6Schristos tst #0x0f,r0 7037c9f0a6Schristos bt 4f 7137c9f0a6Schristos 7237c9f0a6Schristos tst #0x03,r0 7337c9f0a6Schristos bt 2f 7437c9f0a6Schristos tst #0x01,r0 ! not bit 0 -> T 7537c9f0a6Schristos mov #0,r0 7637c9f0a6Schristos rts 7737c9f0a6Schristos addc r1,r0 ! 0 + r1 + T -> r0 7837c9f0a6Schristos 7937c9f0a6Schristos2: tst #0x04,r0 8037c9f0a6Schristos mov #2,r0 8137c9f0a6Schristos rts 8237c9f0a6Schristos addc r1,r0 8337c9f0a6Schristos 8437c9f0a6Schristos4: tst #0x30,r0 8537c9f0a6Schristos bt 6f 8637c9f0a6Schristos tst #0x10,r0 8737c9f0a6Schristos mov #4,r0 8837c9f0a6Schristos rts 8937c9f0a6Schristos addc r1,r0 9037c9f0a6Schristos 9137c9f0a6Schristos6: tst #0x40,r0 9237c9f0a6Schristos mov #6,r0 9337c9f0a6Schristos rts 9437c9f0a6Schristos addc r1,r0 9537c9f0a6Schristos 9637c9f0a6SchristosLzero: rts 9737c9f0a6Schristos nop 98