projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 6aac00e2 AS |
1 | /* |
| 2 | * Copyright (c) 1993 Winning Strategies, Inc. | |
| 3 | * All rights reserved. | |
| 4 | * | |
| 5 | * Redistribution and use in source and binary forms, with or without | |
| 6 | * modification, are permitted provided that the following conditions | |
| 7 | * are met: | |
| 8 | * 1. Redistributions of source code must retain the above copyright | |
| 9 | * notice, this list of conditions and the following disclaimer. | |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright | |
| 11 | * notice, this list of conditions and the following disclaimer in the | |
| 12 | * documentation and/or other materials provided with the distribution. | |
| 13 | * 3. All advertising materials mentioning features or use of this software | |
| 14 | * must display the following acknowledgement: | |
| 15 | * This product includes software developed by Winning Strategies, Inc. | |
| 16 | * 4. The name of the author may not be used to endorse or promote products | |
| 17 | * derived from this software withough specific prior written permission | |
| 18 | * | |
| 19 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
| 20 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
| 21 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
| 22 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
| 23 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
| 24 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 25 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| 26 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| 27 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
| 28 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 29 | * | |
| 30 | * $Id: ffs.s,v 1.1 1993/08/16 18:40:28 jtc Exp $ | |
| 31 | */ | |
| 32 | ||
| 33 | #if defined(LIBC_RCS) && !defined(lint) | |
| 34 | .asciz "$Id: ffs.s,v 1.1 1993/08/16 18:40:28 jtc Exp $" | |
| 35 | #endif /* LIBC_RCS and not lint */ | |
| 36 | ||
| 37 | #include "DEFS.h" | |
| 38 | ||
| 39 | /* | |
| 40 | * ffs(value) | |
| 41 | * finds the first bit set in value and returns the index of | |
| 42 | * that bit. Bits are numbered starting from 1, starting at the | |
| 43 | * rightmost bit. A return value of 0 means that the argument | |
| 44 | * was zero. | |
| 45 | * | |
| 46 | * Written by: | |
| 47 | * J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc. | |
| 48 | */ | |
| 49 | ||
| 50 | ENTRY(ffs) | |
| 51 | bsfl 4(%esp),%eax | |
| 52 | jz L1 /* ZF is set if all bits are 0 */ | |
| 53 | incl %eax /* bits numbered from 1, not 0 */ | |
| 54 | ret | |
| 55 | ||
| 56 | .align 2 | |
| 57 | L1: xorl %eax,%eax /* clear result */ | |
| 58 | ret |