1/* $NetBSD: fpu_rem.c,v 1.10 2011/07/18 07:44:30 isaki Exp $ */ 2 3/* 4 * Copyright (c) 1995 Ken Nakata 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. Neither the name of the author nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)fpu_rem.c 10/24/95 32 */ 33 34#include <sys/cdefs.h> 35__KERNEL_RCSID(0, "$NetBSD: fpu_rem.c,v 1.10 2011/07/18 07:44:30 isaki Exp $"); 36 37#include <sys/types.h> 38#include <sys/signal.h> 39#include <machine/frame.h> 40 41#include "fpu_emulate.h" 42 43/* 44 * ALGORITHM 45 * 46 * Step 1. Save and strip signs of X and Y: signX := sign(X), 47 * signY := sign(Y), X := *X*, Y := *Y*, 48 * signQ := signX EOR signY. Record whether MOD or REM 49 * is requested. 50 * 51 * Step 2. Set L := expo(X)-expo(Y), k := 0, Q := 0. 52 * If (L < 0) then 53 * R := X, go to Step 4. 54 * else 55 * R := 2^(-L)X, j := L. 56 * endif 57 * 58 * Step 3. Perform MOD(X,Y) 59 * 3.1 If R = Y, go to Step 9. 60 * 3.2 If R > Y, then { R := R - Y, Q := Q + 1} 61 * 3.3 If j = 0, go to Step 4. 62 * 3.4 k := k + 1, j := j - 1, Q := 2Q, R := 2R. Go to 63 * Step 3.1. 64 * 65 * Step 4. At this point, R = X - QY = MOD(X,Y). Set 66 * Last_Subtract := false (used in Step 7 below). If 67 * MOD is requested, go to Step 6. 68 * 69 * Step 5. R = MOD(X,Y), but REM(X,Y) is requested. 70 * 5.1 If R < Y/2, then R = MOD(X,Y) = REM(X,Y). Go to 71 * Step 6. 72 * 5.2 If R > Y/2, then { set Last_Subtract := true, 73 * Q := Q + 1, Y := signY*Y }. Go to Step 6. 74 * 5.3 This is the tricky case of R = Y/2. If Q is odd, 75 * then { Q := Q + 1, signX := -signX }. 76 * 77 * Step 6. R := signX*R. 78 * 79 * Step 7. If Last_Subtract = true, R := R - Y. 80 * 81 * Step 8. Return signQ, last 7 bits of Q, and R as required. 82 * 83 * Step 9. At this point, R = 2^(-j)*X - Q Y = Y. Thus, 84 * X = 2^(j)*(Q+1)Y. set Q := 2^(j)*(Q+1), 85 * R := 0. Return signQ, last 7 bits of Q, and R. 86 */ 87 88static struct fpn * __fpu_modrem(struct fpemu *fe, int modrem); 89 90static struct fpn * 91__fpu_modrem(struct fpemu *fe, int modrem) 92{ 93 static struct fpn X, Y; 94 struct fpn *x, *y, *r; 95 u_int signX, signY, signQ; 96 int j, k, l, q; 97 int Last_Subtract; 98 99 CPYFPN(&X, &fe->fe_f1); 100 CPYFPN(&Y, &fe->fe_f2); 101 x = &X; 102 y = &Y; 103 r = &fe->fe_f2; 104 105 /* 106 * Step 1 107 */ 108 signX = x->fp_sign; 109 signY = y->fp_sign; 110 signQ = (signX ^ signY); 111 x->fp_sign = y->fp_sign = 0; 112 113 /* 114 * Step 2 115 */ 116 l = x->fp_exp - y->fp_exp; 117 k = 0; 118 q = 0; 119 if (l >= 0) { 120 CPYFPN(r, x); 121 r->fp_exp -= l; 122 j = l; 123 124 /* 125 * Step 3 126 */ 127 while (y->fp_exp != r->fp_exp || 128 y->fp_mant[0] != r->fp_mant[0] || 129 y->fp_mant[1] != r->fp_mant[1] || 130 y->fp_mant[2] != r->fp_mant[2]) { 131 132 /* Step 3.2 */ 133 if (y->fp_exp < r->fp_exp || 134 y->fp_mant[0] < r->fp_mant[0] || 135 y->fp_mant[1] < r->fp_mant[1] || 136 y->fp_mant[2] < r->fp_mant[2]) { 137 CPYFPN(&fe->fe_f1, r); 138 CPYFPN(&fe->fe_f2, y); 139 fe->fe_f2.fp_sign = 1; 140 r = fpu_add(fe); 141 q++; 142 } 143 144 /* Step 3.3 */ 145 if (j == 0) 146 goto Step4; 147 148 /* Step 3.4 */ 149 k++; 150 j--; 151 q += q; 152 r->fp_exp++; 153 } 154 /* Step 9 */ 155 goto Step9; 156 } 157 Step4: 158 Last_Subtract = 0; 159 if (modrem == 0) 160 goto Step6; 161 162 /* 163 * Step 5 164 */ 165 /* Step 5.1 */ 166 if (r->fp_exp + 1 < y->fp_exp || 167 (r->fp_exp + 1 == y->fp_exp && 168 (r->fp_mant[0] < y->fp_mant[0] || 169 r->fp_mant[1] < y->fp_mant[1] || 170 r->fp_mant[2] < y->fp_mant[2]))) { 171 /* if r < y/2 */ 172 goto Step6; 173 } 174 /* Step 5.2 */ 175 if (r->fp_exp + 1 != y->fp_exp || 176 r->fp_mant[0] != y->fp_mant[0] || 177 r->fp_mant[1] != y->fp_mant[1] || 178 r->fp_mant[2] != y->fp_mant[2]) { 179 /* if (!(r < y/2) && !(r == y/2)) */ 180 Last_Subtract = 1; 181 q++; 182 y->fp_sign = signY; 183 } else { 184 /* Step 5.3 */ 185 /* r == y/2 */ 186 if (q % 2) { 187 q++; 188 signX = !signX; 189 } 190 } 191 192 Step6: 193 r->fp_sign = signX; 194 195 /* 196 * Step 7 197 */ 198 if (Last_Subtract) { 199 CPYFPN(&fe->fe_f1, r); 200 CPYFPN(&fe->fe_f2, y); 201 fe->fe_f2.fp_sign = !y->fp_sign; 202 r = fpu_add(fe); 203 } 204 /* 205 * Step 8 206 */ 207 q &= 0x7f; 208 q |= (signQ << 7); 209 fe->fe_fpframe->fpf_fpsr = 210 fe->fe_fpsr = 211 (fe->fe_fpsr & ~FPSR_QTT) | (q << 16); 212 return r; 213 214 Step9: 215 fe->fe_f1.fp_class = FPC_ZERO; 216 q++; 217 q &= 0x7f; 218 q |= (signQ << 7); 219 fe->fe_fpframe->fpf_fpsr = 220 fe->fe_fpsr = 221 (fe->fe_fpsr & ~FPSR_QTT) | (q << 16); 222 return &fe->fe_f1; 223} 224 225struct fpn * 226fpu_rem(struct fpemu *fe) 227{ 228 return __fpu_modrem(fe, 1); 229} 230 231struct fpn * 232fpu_mod(struct fpemu *fe) 233{ 234 return __fpu_modrem(fe, 0); 235} 236