bsd/dev/ppc/ffs.s

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_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. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23 /* Copyright (c) 1992, 1997-1998 Apple Computer, Inc.  All rights reserved.
  24  *
  25  *      File:  machdep/ppc/libc/ffs.s
  26  *
  27  *      int ffs(int value)
  28  *
  29  *      DESCRIPTION
  30  *              The ffs() function finds the first bit set in value and returns the
  31  *              index of that bit.  Bits are numbered starting from 1, starting at
  32  *              the right-most bit. A return value of 0 means that the argument was
  33  *
  34  * HISTORY
  35  *      14-Aug-1998     Umesh Vaishampayan      (umeshv@apple.com)
  36  *              Optimized!
  37  *
  38  *  10-Mar-1998 Matt Watson (mwatson@apple.com)
  39  *      Correctified
  40  *
  41  *  19-Jan-1998 Matt Watson (mwatson@apple.com)
  42  *      Simplified
  43  *
  44  *  24-Jan-1997 Umesh Vaishampayan (umeshv@NeXT.com)
  45  *      Ported to PPC.
  46  */
  47
  48 .text
  49 .align 4
  50 .globl _ffs
  51 _ffs:                                   /* Cycles */
  52         neg             r0,r3           /* 0 */
  53         and             r3,r0,r3        /* 1 */
  54         li              r4, 32          /* 1 */
  55         cntlzw  r3,r3           /* 2 */
  56         subf    r3,r3,r4        /* 3 */
  57         blr
  58
  59         .globl  _abs
  60 _abs:
  61         srawi r0,r3,31
  62         xor r3,r0,r3
  63         subf r3,r0,r3
  64         blr
  65