1 /* $NetBSD: mul.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */ 2 3 /* 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This software was developed by the Computer Systems Engineering group 8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 9 * contributed to Berkeley. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * from: Header: mul.s,v 1.5 92/06/25 13:24:03 torek Exp 36 */ 37 38 #include <machine/asm.h> 39 #if defined(LIBC_SCCS) && !defined(lint) 40 #if 0 41 .asciz "@(#)mul.s 8.1 (Berkeley) 6/4/93" 42 #else 43 RCSID("$NetBSD: mul.S,v 1.1 2005/12/20 19:28:50 christos Exp $") 44 #endif 45 #endif /* LIBC_SCCS and not lint */ 46 47 /* 48 * Signed multiply, from Appendix E of the Sparc Version 8 49 * Architecture Manual. 50 * 51 * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of 52 * the 64-bit product). 53 * 54 * This code optimizes short (less than 13-bit) multiplies. 55 */ 56 57 FUNC(.mul) 58 mov %o0, %y ! multiplier -> Y 59 andncc %o0, 0xfff, %g0 ! test bits 12..31 60 be Lmul_shortway ! if zero, can do it the short way 61 andcc %g0, %g0, %o4 ! zero the partial product and clear N and V 62 63 /* 64 * Long multiply. 32 steps, followed by a final shift step. 65 */ 66 mulscc %o4, %o1, %o4 ! 1 67 mulscc %o4, %o1, %o4 ! 2 68 mulscc %o4, %o1, %o4 ! 3 69 mulscc %o4, %o1, %o4 ! 4 70 mulscc %o4, %o1, %o4 ! 5 71 mulscc %o4, %o1, %o4 ! 6 72 mulscc %o4, %o1, %o4 ! 7 73 mulscc %o4, %o1, %o4 ! 8 74 mulscc %o4, %o1, %o4 ! 9 75 mulscc %o4, %o1, %o4 ! 10 76 mulscc %o4, %o1, %o4 ! 11 77 mulscc %o4, %o1, %o4 ! 12 78 mulscc %o4, %o1, %o4 ! 13 79 mulscc %o4, %o1, %o4 ! 14 80 mulscc %o4, %o1, %o4 ! 15 81 mulscc %o4, %o1, %o4 ! 16 82 mulscc %o4, %o1, %o4 ! 17 83 mulscc %o4, %o1, %o4 ! 18 84 mulscc %o4, %o1, %o4 ! 19 85 mulscc %o4, %o1, %o4 ! 20 86 mulscc %o4, %o1, %o4 ! 21 87 mulscc %o4, %o1, %o4 ! 22 88 mulscc %o4, %o1, %o4 ! 23 89 mulscc %o4, %o1, %o4 ! 24 90 mulscc %o4, %o1, %o4 ! 25 91 mulscc %o4, %o1, %o4 ! 26 92 mulscc %o4, %o1, %o4 ! 27 93 mulscc %o4, %o1, %o4 ! 28 94 mulscc %o4, %o1, %o4 ! 29 95 mulscc %o4, %o1, %o4 ! 30 96 mulscc %o4, %o1, %o4 ! 31 97 mulscc %o4, %o1, %o4 ! 32 98 mulscc %o4, %g0, %o4 ! final shift 99 100 ! If %o0 was negative, the result is 101 ! (%o0 * %o1) + (%o1 << 32)) 102 ! We fix that here. 103 104 tst %o0 105 bge 1f 106 rd %y, %o0 107 108 ! %o0 was indeed negative; fix upper 32 bits of result by subtracting 109 ! %o1 (i.e., return %o4 - %o1 in %o1). 110 retl 111 sub %o4, %o1, %o1 112 113 1: 114 retl 115 mov %o4, %o1 116 117 Lmul_shortway: 118 /* 119 * Short multiply. 12 steps, followed by a final shift step. 120 * The resulting bits are off by 12 and (32-12) = 20 bit positions, 121 * but there is no problem with %o0 being negative (unlike above). 122 */ 123 mulscc %o4, %o1, %o4 ! 1 124 mulscc %o4, %o1, %o4 ! 2 125 mulscc %o4, %o1, %o4 ! 3 126 mulscc %o4, %o1, %o4 ! 4 127 mulscc %o4, %o1, %o4 ! 5 128 mulscc %o4, %o1, %o4 ! 6 129 mulscc %o4, %o1, %o4 ! 7 130 mulscc %o4, %o1, %o4 ! 8 131 mulscc %o4, %o1, %o4 ! 9 132 mulscc %o4, %o1, %o4 ! 10 133 mulscc %o4, %o1, %o4 ! 11 134 mulscc %o4, %o1, %o4 ! 12 135 mulscc %o4, %g0, %o4 ! final shift 136 137 /* 138 * %o4 has 20 of the bits that should be in the low part of the 139 * result; %y has the bottom 12 (as %y's top 12). That is: 140 * 141 * %o4 %y 142 * +----------------+----------------+ 143 * | -12- | -20- | -12- | -20- | 144 * +------(---------+------)---------+ 145 * --hi-- ----low-part---- 146 * 147 * The upper 12 bits of %o4 should be sign-extended to form the 148 * high part of the product (i.e., highpart = %o4 >> 20). 149 */ 150 151 rd %y, %o5 152 sll %o4, 12, %o0 ! shift middle bits left 12 153 srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left 154 or %o5, %o0, %o0 ! construct low part of result 155 retl 156 sra %o4, 20, %o1 ! ... and extract high part of result 157
Indexes created Sun Sep 21 20:09:37 GMT 2025