| Shin-ichiro KAWASAKI | 1009327 | 2009-09-28 16:11:39 +0900 | [diff] [blame] | 1 | /* $NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2002 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by ITOH Yasufumi. |
| 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 | * 3. All advertising materials mentioning features or use of this software |
| 19 | * must display the following acknowledgement: |
| 20 | * This product includes software developed by the NetBSD |
| 21 | * Foundation, Inc. and its contributors. |
| 22 | * 4. Neither the name of The NetBSD Foundation nor the names of its |
| 23 | * contributors may be used to endorse or promote products derived |
| 24 | * from this software without specific prior written permission. |
| 25 | * |
| 26 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 27 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 28 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 29 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 30 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 31 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 32 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 33 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 34 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 35 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 36 | * POSSIBILITY OF SUCH DAMAGE. |
| 37 | */ |
| 38 | |
| 39 | #include <machine/asm.h> |
| 40 | |
| 41 | #if defined(LIBC_SCCS) && !defined(lint) |
| 42 | RCSID("$NetBSD: ffs.S,v 1.1 2005/12/20 19:28:50 christos Exp $") |
| 43 | #endif |
| 44 | |
| 45 | /* |
| 46 | * ffs - find first bit set |
| 47 | * |
| 48 | * This code makes use of ``test 8bit'' and ``shift 8bit'' instructions. |
| 49 | * The remaining 8bit is tested in every 2bit. |
| 50 | */ |
| 51 | |
| 52 | ENTRY(ffs) |
| 53 | mov r4,r0 ! using r0 specific instructions |
| 54 | tst #0xff,r0 |
| 55 | bf/s L8bit |
| 56 | mov #0+1,r1 ! ret = 1..8 |
| 57 | |
| 58 | tst r0,r0 ! ffs(0) is 0 |
| 59 | bt Lzero ! testing here to accelerate ret=1..8 cases |
| 60 | |
| 61 | shlr8 r0 |
| 62 | tst #0xff,r0 |
| 63 | bf/s L8bit |
| 64 | mov #8+1,r1 ! ret = 9..16 |
| 65 | |
| 66 | shlr8 r0 |
| 67 | tst #0xff,r0 |
| 68 | bf/s L8bit |
| 69 | mov #16+1,r1 ! ret = 17..24 |
| 70 | |
| 71 | shlr8 r0 |
| 72 | mov #24+1,r1 ! ret = 25..32 |
| 73 | |
| 74 | L8bit: |
| 75 | tst #0x0f,r0 |
| 76 | bt 4f |
| 77 | |
| 78 | tst #0x03,r0 |
| 79 | bt 2f |
| 80 | tst #0x01,r0 ! not bit 0 -> T |
| 81 | mov #0,r0 |
| 82 | rts |
| 83 | addc r1,r0 ! 0 + r1 + T -> r0 |
| 84 | |
| 85 | 2: tst #0x04,r0 |
| 86 | mov #2,r0 |
| 87 | rts |
| 88 | addc r1,r0 |
| 89 | |
| 90 | 4: tst #0x30,r0 |
| 91 | bt 6f |
| 92 | tst #0x10,r0 |
| 93 | mov #4,r0 |
| 94 | rts |
| 95 | addc r1,r0 |
| 96 | |
| 97 | 6: tst #0x40,r0 |
| 98 | mov #6,r0 |
| 99 | rts |
| 100 | addc r1,r0 |
| 101 | |
| 102 | Lzero: rts |
| 103 | nop |