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ffs.S revision 1.1.16.2 
      1 /*	$NetBSD: ffs.S,v 1.1.16.2 2020/04/21 19:37:43 martin Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1995 Christopher G. Demetriou
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *      This product includes software developed by Christopher G. Demetriou
     18  *	for the NetBSD Project.
     19  * 4. The name of the author may not be used to endorse or promote products
     20  *    derived from this software without specific prior written permission
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     32  *
     33  * __FBSDID("$FreeBSD: releng/10.1/lib/libc/ia64/string/ffs.S 111777 2003-03-03 01:09:46Z obrien $");
     34  *
     35  */
     36 
     37 #include <machine/asm.h>
     38 /*
     39 
     40 /*
     41  * int
     42  * ffs(int value);
     43  */
     44 ENTRY(ffs, 1)
     45 	sxt4	r14=in0 ;;
     46 	cmp.eq	p6,p0=r14,r0
     47 (p6)	br.dpnt.few Lallzero
     48 
     49 	/*
     50 	 * Initialize return value (ret0), and set up r15 so that it
     51 	 * contains the mask with only the lowest bit set.
     52 	 */
     53 	sub	r15=r0,r14
     54 	mov	ret0=1 ;;
     55 	and	r15=r14,r15 ;;
     56 
     57 	extr.u	r16=r15,0,8 ;;
     58 	cmp.ne	p6,p0=r0,r16
     59 (p6)	br.dptk.few Ldo8
     60 
     61 	/*
     62 	 * If lower 16 bits empty, add 16 to result and use upper 16.
     63 	 */
     64 	extr.u	r16=r15,0,16 ;;
     65 	cmp.ne	p6,p0=r0,r16
     66 (p6)	br.dptk.few Ldo16
     67 	extr.u	r15=r15,16,16
     68 	add	ret0=16,ret0 ;;
     69 
     70 Ldo16:
     71 	/*
     72 	 * If lower 8 bits empty, add 8 to result and use upper 8.
     73 	 */
     74 	extr.u	r16=r15,0,8 ;;
     75 	cmp.ne	p6,p0=r0,r16
     76 (p6)	br.dptk.few Ldo8
     77 	extr.u	r15=r15,8,24
     78 	add	ret0=8,ret0 ;;
     79 
     80 Ldo8:
     81 	and	r16=0x0f,r15		/* lower 4 of 8 empty? */
     82 	and	r17=0x33,r15		/* lower 2 of each 4 empty? */
     83 	and	r18=0x55,r15 ;;		/* lower 1 of each 2 empty? */
     84 	cmp.ne	p6,p0=r16,r0
     85 	cmp.ne	p7,p0=r17,r0
     86 	cmp.ne	p8,p0=r18,r0
     87 
     88 	/* If lower 4 bits empty, add 4 to result. */
     89 (p6)	br.dptk.few Ldo4
     90 	add	ret0=4,ret0 ;;
     91 
     92 Ldo4:	/* If lower 2 bits of each 4 empty, add 2 to result. */
     93 (p7)	br.dptk.few Ldo2
     94 	add	ret0=2,ret0 ;;
     95 
     96 Ldo2:	/* If lower bit of each 2 empty, add 1 to result. */
     97 (p8)	br.dptk.few Ldone
     98 	add	ret0=1,ret0
     99 
    100 Ldone:
    101 	br.ret.sptk.few rp
    102 
    103 Lallzero:
    104 	mov	ret0=0
    105 	br.ret.sptk.few rp
    106 END(ffs)
    107