bsd/dev/ppc/ffs.s

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /* Copyright (c) 1992, 1997-1998 Apple Computer, Inc.  All rights reserved.
  29  *
  30  *      File:  machdep/ppc/libc/ffs.s
  31  *
  32  *      int ffs(int value)
  33  *
  34  *      DESCRIPTION
  35  *              The ffs() function finds the first bit set in value and returns the
  36  *              index of that bit.  Bits are numbered starting from 1, starting at
  37  *              the right-most bit. A return value of 0 means that the argument was
  38  *
  39  * HISTORY
  40  *      14-Aug-1998     Umesh Vaishampayan      (umeshv@apple.com)
  41  *              Optimized!
  42  *
  43  *  10-Mar-1998 Matt Watson (mwatson@apple.com)
  44  *      Correctified
  45  *
  46  *  19-Jan-1998 Matt Watson (mwatson@apple.com)
  47  *      Simplified
  48  *
  49  *  24-Jan-1997 Umesh Vaishampayan (umeshv@NeXT.com)
  50  *      Ported to PPC.
  51  */
  52
  53 .text
  54 .align 4
  55 .globl _ffs
  56 _ffs:                                   /* Cycles */
  57         neg             r0,r3           /* 0 */
  58         and             r3,r0,r3        /* 1 */
  59         li              r4, 32          /* 1 */
  60         cntlzw  r3,r3           /* 2 */
  61         subf    r3,r3,r4        /* 3 */
  62         blr
  63
  64         .globl  _abs
  65 _abs:
  66         srawi r0,r3,31
  67         xor r3,r0,r3
  68         subf r3,r0,r3
  69         blr
  70