1 /* $NetBSD: fpu_explode.c,v 1.7 2005/12/11 12:17:52 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 * All advertising materials mentioning features or use of this software 12 * must display the following acknowledgement: 13 * This product includes software developed by the University of 14 * California, Lawrence Berkeley Laboratory. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 3. Neither the name of the University nor the names of its contributors 25 * may be used to endorse or promote products derived from this software 26 * without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 38 * SUCH DAMAGE. 39 * 40 * @(#)fpu_explode.c 8.1 (Berkeley) 6/11/93 41 */ 42 43 /* 44 * FPU subroutines: `explode' the machine's `packed binary' format numbers 45 * into our internal format. 46 */ 47 48 #include <sys/cdefs.h> 49 __KERNEL_RCSID(0, "$NetBSD: fpu_explode.c,v 1.7 2005/12/11 12:17:52 christos Exp $"); 50 51 #include <sys/types.h> 52 #include <sys/systm.h> 53 54 #include <machine/ieee.h> 55 #include <machine/reg.h> 56 57 #include "fpu_arith.h" 58 #include "fpu_emulate.h" 59 60 61 /* Conversion to internal format -- note asymmetry. */ 62 static int fpu_itof __P((struct fpn *fp, u_int i)); 63 static int fpu_stof __P((struct fpn *fp, u_int i)); 64 static int fpu_dtof __P((struct fpn *fp, u_int i, u_int j)); 65 static int fpu_xtof __P((struct fpn *fp, u_int i, u_int j, u_int k)); 66 67 /* 68 * N.B.: in all of the following, we assume the FP format is 69 * 70 * --------------------------- 71 * | s | exponent | fraction | 72 * --------------------------- 73 * 74 * (which represents -1**s * 1.fraction * 2**exponent), so that the 75 * sign bit is way at the top (bit 31), the exponent is next, and 76 * then the remaining bits mark the fraction. A zero exponent means 77 * zero or denormalized (0.fraction rather than 1.fraction), and the 78 * maximum possible exponent, 2bias+1, signals inf (fraction==0) or NaN. 79 * 80 * Since the sign bit is always the topmost bit---this holds even for 81 * integers---we set that outside all the *tof functions. Each function 82 * returns the class code for the new number (but note that we use 83 * FPC_QNAN for all NaNs; fpu_explode will fix this if appropriate). 84 */ 85 86 /* 87 * int -> fpn. 88 */ 89 static int 90 fpu_itof(fp, i) 91 register struct fpn *fp; 92 register u_int i; 93 { 94 95 if (i == 0) 96 return (FPC_ZERO); 97 /* 98 * The value FP_1 represents 2^FP_LG, so set the exponent 99 * there and let normalization fix it up. Convert negative 100 * numbers to sign-and-magnitude. Note that this relies on 101 * fpu_norm()'s handling of `supernormals'; see fpu_subr.c. 102 */ 103 fp->fp_exp = FP_LG; 104 fp->fp_mant[0] = (int)i < 0 ? -i : i; 105 fp->fp_mant[1] = 0; 106 fp->fp_mant[2] = 0; 107 fpu_norm(fp); 108 return (FPC_NUM); 109 } 110 111 #define mask(nbits) ((1 << (nbits)) - 1) 112 113 /* 114 * All external floating formats convert to internal in the same manner, 115 * as defined here. Note that only normals get an implied 1.0 inserted. 116 */ 117 #define FP_TOF(exp, expbias, allfrac, f0, f1, f2, f3) \ 118 if (exp == 0) { \ 119 if (allfrac == 0) \ 120 return (FPC_ZERO); \ 121 fp->fp_exp = 1 - expbias; \ 122 fp->fp_mant[0] = f0; \ 123 fp->fp_mant[1] = f1; \ 124 fp->fp_mant[2] = f2; \ 125 fpu_norm(fp); \ 126 return (FPC_NUM); \ 127 } \ 128 if (exp == (2 * expbias + 1)) { \ 129 if (allfrac == 0) \ 130 return (FPC_INF); \ 131 fp->fp_mant[0] = f0; \ 132 fp->fp_mant[1] = f1; \ 133 fp->fp_mant[2] = f2; \ 134 return (FPC_QNAN); \ 135 } \ 136 fp->fp_exp = exp - expbias; \ 137 fp->fp_mant[0] = FP_1 | f0; \ 138 fp->fp_mant[1] = f1; \ 139 fp->fp_mant[2] = f2; \ 140 return (FPC_NUM) 141 142 /* 143 * 32-bit single precision -> fpn. 144 * We assume a single occupies at most (64-FP_LG) bits in the internal 145 * format: i.e., needs at most fp_mant[0] and fp_mant[1]. 146 */ 147 static int 148 fpu_stof(fp, i) 149 register struct fpn *fp; 150 register u_int i; 151 { 152 register int exp; 153 register u_int frac, f0, f1; 154 #define SNG_SHIFT (SNG_FRACBITS - FP_LG) 155 156 exp = (i >> (32 - 1 - SNG_EXPBITS)) & mask(SNG_EXPBITS); 157 frac = i & mask(SNG_FRACBITS); 158 f0 = frac >> SNG_SHIFT; 159 f1 = frac << (32 - SNG_SHIFT); 160 FP_TOF(exp, SNG_EXP_BIAS, frac, f0, f1, 0, 0); 161 } 162 163 /* 164 * 64-bit double -> fpn. 165 * We assume this uses at most (96-FP_LG) bits. 166 */ 167 static int 168 fpu_dtof(fp, i, j) 169 register struct fpn *fp; 170 register u_int i, j; 171 { 172 register int exp; 173 register u_int frac, f0, f1, f2; 174 #define DBL_SHIFT (DBL_FRACBITS - 32 - FP_LG) 175 176 exp = (i >> (32 - 1 - DBL_EXPBITS)) & mask(DBL_EXPBITS); 177 frac = i & mask(DBL_FRACBITS - 32); 178 f0 = frac >> DBL_SHIFT; 179 f1 = (frac << (32 - DBL_SHIFT)) | (j >> DBL_SHIFT); 180 f2 = j << (32 - DBL_SHIFT); 181 frac |= j; 182 FP_TOF(exp, DBL_EXP_BIAS, frac, f0, f1, f2, 0); 183 } 184 185 /* 186 * 96-bit extended -> fpn. 187 */ 188 static int 189 fpu_xtof(fp, i, j, k) 190 register struct fpn *fp; 191 register u_int i, j, k; 192 { 193 register int exp; 194 register u_int frac, f0, f1, f2; 195 #define EXT_SHIFT (EXT_FRACBITS - 1 - 32 - FP_LG) 196 197 exp = (i >> (32 - 1 - EXT_EXPBITS)) & mask(EXT_EXPBITS); 198 f0 = j >> EXT_SHIFT; 199 f1 = (j << (32 - EXT_SHIFT)) | (k >> EXT_SHIFT); 200 f2 = k << (32 - EXT_SHIFT); 201 frac = j | k; 202 203 /* m68k extended does not imply denormal by exp==0 */ 204 if (exp == 0) { 205 if (frac == 0) 206 return (FPC_ZERO); 207 fp->fp_exp = - EXT_EXP_BIAS; 208 fp->fp_mant[0] = f0; 209 fp->fp_mant[1] = f1; 210 fp->fp_mant[2] = f2; 211 fpu_norm(fp); 212 return (FPC_NUM); 213 } 214 if (exp == (2 * EXT_EXP_BIAS + 1)) { 215 if (frac == 0) 216 return (FPC_INF); 217 fp->fp_mant[0] = f0; 218 fp->fp_mant[1] = f1; 219 fp->fp_mant[2] = f2; 220 return (FPC_QNAN); 221 } 222 fp->fp_exp = exp - EXT_EXP_BIAS; 223 fp->fp_mant[0] = FP_1 | f0; 224 fp->fp_mant[1] = f1; 225 fp->fp_mant[2] = f2; 226 return (FPC_NUM); 227 } 228 229 /* 230 * Explode the contents of a memory operand. 231 */ 232 void 233 fpu_explode(fe, fp, type, space) 234 register struct fpemu *fe; 235 register struct fpn *fp; 236 int type; 237 register u_int *space; 238 { 239 register u_int s; 240 241 s = space[0]; 242 fp->fp_sign = s >> 31; 243 fp->fp_sticky = 0; 244 switch (type) { 245 246 case FTYPE_BYT: 247 s >>= 8; 248 case FTYPE_WRD: 249 s >>= 16; 250 case FTYPE_LNG: 251 s = fpu_itof(fp, s); 252 break; 253 254 case FTYPE_SNG: 255 s = fpu_stof(fp, s); 256 break; 257 258 case FTYPE_DBL: 259 s = fpu_dtof(fp, s, space[1]); 260 break; 261 262 case FTYPE_EXT: 263 s = fpu_xtof(fp, s, space[1], space[2]); 264 break; 265 266 default: 267 panic("fpu_explode"); 268 } 269 if (s == FPC_QNAN && (fp->fp_mant[0] & FP_QUIETBIT) == 0) { 270 /* 271 * Input is a signalling NaN. All operations that return 272 * an input NaN operand put it through a ``NaN conversion'', 273 * which basically just means ``turn on the quiet bit''. 274 * We do this here so that all NaNs internally look quiet 275 * (we can tell signalling ones by their class). 276 */ 277 fp->fp_mant[0] |= FP_QUIETBIT; 278 fe->fe_fpsr |= FPSR_SNAN; /* assert SNAN exception */ 279 s = FPC_SNAN; 280 } 281 fp->fp_class = s; 282 } 283