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      1 /* $NetBSD: mulsi3.S,v 1.1 2014/09/03 19:34:25 matt Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2014 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Matt Thomas of 3am Software Foundry.
      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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <machine/asm.h>
     33 
     34 __RCSID("$NetBSD: mulsi3.S,v 1.1 2014/09/03 19:34:25 matt Exp $")
     35 
     36 ENTRY(__mulsi3)
     37 	l.movhi	r11, 0
     38 
     39 	l.sfeqi	r3, 0
     40 	l.bf	.Lret
     41 	l.nop
     42 
     43 	l.sfeqi	r4, 0
     44 	l.bf	.Lret
     45 	l.nop
     46 
     47 	l.sfleu	r3, r4		# is r3 < r4 (unsigned)
     48 #if 0
     49 	l.ori	r6, r3, 0	# move r3 to r6
     50 	l.bf	.Lloop		#   yes, r6 already has smaller value,
     51 	l.nop
     52 	l.ori	r6, r4, 0	# move r4 to r6 because it's smaller than r3
     53 #else
     54 	l.cmov	r6, r3, r4	# choose lesser of r3 or r4
     55 #endif
     56 
     57 .Lloop:
     58 	l.andi	r5, r6, 1	# get LSB
     59 	l.sub	r8, r0, r5	# 0 -> 0, 1 -> 0xffffffff
     60 	l.and	r8, r8, r4	# r8 = r6 & 1 ? r4 : 0
     61 	l.add	r11, r11, r8	# add to result
     62 	l.srli	r4, r4, 1	# discard LSB
     63 	l.slli	r6, r6, 1	# multiply by 2
     64 .Lentry:
     65 	l.sfeqi	r4, 0		# only 0 left?
     66 	l.bf	.Lret		#   yes, we're done
     67 	l.nop
     68 	l.sfeqi	r6, 0		# only 0 left?
     69 	l.bnf	.Lloop		#   no, another round of long multiplication.
     70 	l.nop
     71 
     72 .Lret:	l.jr	lr
     73 	l.nop
     74 END(__mulsi3)
     75