LXR linux/arch/parisc/math-emu/sfmpy.c

   1/*
   2 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
   3 *
   4 * Floating-point emulation code
   5 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
   6 *
   7 *    This program is free software; you can redistribute it and/or modify
   8 *    it under the terms of the GNU General Public License as published by
   9 *    the Free Software Foundation; either version 2, or (at your option)
  10 *    any later version.
  11 *
  12 *    This program is distributed in the hope that it will be useful,
  13 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 *    GNU General Public License for more details.
  16 *
  17 *    You should have received a copy of the GNU General Public License
  18 *    along with this program; if not, write to the Free Software
  19 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20 */
  21/*
  22 * BEGIN_DESC
  23 *
  24 *  File:
  25 *      @(#)    pa/spmath/sfmpy.c               $Revision: 1.1 $
  26 *
  27 *  Purpose:
  28 *      Single Precision Floating-point Multiply
  29 *
  30 *  External Interfaces:
  31 *      sgl_fmpy(srcptr1,srcptr2,dstptr,status)
  32 *
  33 *  Internal Interfaces:
  34 *
  35 *  Theory:
  36 *      <<please update with a overview of the operation of this file>>
  37 *
  38 * END_DESC
  39*/
  40
  41
  42#include "float.h"
  43#include "sgl_float.h"
  44
  45/*
  46 *  Single Precision Floating-point Multiply
  47 */
  48
  49int
  50sgl_fmpy(
  51    sgl_floating_point *srcptr1,
  52    sgl_floating_point *srcptr2,
  53    sgl_floating_point *dstptr,
  54    unsigned int *status)
  55{
  56        register unsigned int opnd1, opnd2, opnd3, result;
  57        register int dest_exponent, count;
  58        register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
  59        boolean is_tiny;
  60
  61        opnd1 = *srcptr1;
  62        opnd2 = *srcptr2;
  63        /* 
  64         * set sign bit of result 
  65         */
  66        if (Sgl_sign(opnd1) ^ Sgl_sign(opnd2)) Sgl_setnegativezero(result);  
  67        else Sgl_setzero(result);
  68        /*
  69         * check first operand for NaN's or infinity
  70         */
  71        if (Sgl_isinfinity_exponent(opnd1)) {
  72                if (Sgl_iszero_mantissa(opnd1)) {
  73                        if (Sgl_isnotnan(opnd2)) {
  74                                if (Sgl_iszero_exponentmantissa(opnd2)) {
  75                                        /* 
  76                                         * invalid since operands are infinity 
  77                                         * and zero 
  78                                         */
  79                                        if (Is_invalidtrap_enabled()) 
  80                                                return(INVALIDEXCEPTION);
  81                                        Set_invalidflag();
  82                                        Sgl_makequietnan(result);
  83                                        *dstptr = result;
  84                                        return(NOEXCEPTION);
  85                                }
  86                                /*
  87                                 * return infinity
  88                                 */
  89                                Sgl_setinfinity_exponentmantissa(result);
  90                                *dstptr = result;
  91                                return(NOEXCEPTION);
  92                        }
  93                }
  94                else {
  95                        /*
  96                         * is NaN; signaling or quiet?
  97                         */
  98                        if (Sgl_isone_signaling(opnd1)) {
  99                                /* trap if INVALIDTRAP enabled */
 100                                if (Is_invalidtrap_enabled()) 
 101                                        return(INVALIDEXCEPTION);
 102                                /* make NaN quiet */
 103                                Set_invalidflag();
 104                                Sgl_set_quiet(opnd1);
 105                        }
 106                        /* 
 107                         * is second operand a signaling NaN? 
 108                         */
 109                        else if (Sgl_is_signalingnan(opnd2)) {
 110                                /* trap if INVALIDTRAP enabled */
 111                                if (Is_invalidtrap_enabled()) 
 112                                        return(INVALIDEXCEPTION);
 113                                /* make NaN quiet */
 114                                Set_invalidflag();
 115                                Sgl_set_quiet(opnd2);
 116                                *dstptr = opnd2;
 117                                return(NOEXCEPTION);
 118                        }
 119                        /*
 120                         * return quiet NaN
 121                         */
 122                        *dstptr = opnd1;
 123                        return(NOEXCEPTION);
 124                }
 125        }
 126        /*
 127         * check second operand for NaN's or infinity
 128         */
 129        if (Sgl_isinfinity_exponent(opnd2)) {
 130                if (Sgl_iszero_mantissa(opnd2)) {
 131                        if (Sgl_iszero_exponentmantissa(opnd1)) {
 132                                /* invalid since operands are zero & infinity */
 133                                if (Is_invalidtrap_enabled()) 
 134                                        return(INVALIDEXCEPTION);
 135                                Set_invalidflag();
 136                                Sgl_makequietnan(opnd2);
 137                                *dstptr = opnd2;
 138                                return(NOEXCEPTION);
 139                        }
 140                        /*
 141                         * return infinity
 142                         */
 143                        Sgl_setinfinity_exponentmantissa(result);
 144                        *dstptr = result;
 145                        return(NOEXCEPTION);
 146                }
 147                /*
 148                 * is NaN; signaling or quiet?
 149                 */
 150                if (Sgl_isone_signaling(opnd2)) {
 151                        /* trap if INVALIDTRAP enabled */
 152                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
 153
 154                        /* make NaN quiet */
 155                        Set_invalidflag();
 156                        Sgl_set_quiet(opnd2);
 157                }
 158                /*
 159                 * return quiet NaN
 160                 */
 161                *dstptr = opnd2;
 162                return(NOEXCEPTION);
 163        }
 164        /*
 165         * Generate exponent 
 166         */
 167        dest_exponent = Sgl_exponent(opnd1) + Sgl_exponent(opnd2) - SGL_BIAS;
 168
 169        /*
 170         * Generate mantissa
 171         */
 172        if (Sgl_isnotzero_exponent(opnd1)) {
 173                /* set hidden bit */
 174                Sgl_clear_signexponent_set_hidden(opnd1);
 175        }
 176        else {
 177                /* check for zero */
 178                if (Sgl_iszero_mantissa(opnd1)) {
 179                        Sgl_setzero_exponentmantissa(result);
 180                        *dstptr = result;
 181                        return(NOEXCEPTION);
 182                }
 183                /* is denormalized, adjust exponent */
 184                Sgl_clear_signexponent(opnd1);
 185                Sgl_leftshiftby1(opnd1);
 186                Sgl_normalize(opnd1,dest_exponent);
 187        }
 188        /* opnd2 needs to have hidden bit set with msb in hidden bit */
 189        if (Sgl_isnotzero_exponent(opnd2)) {
 190                Sgl_clear_signexponent_set_hidden(opnd2);
 191        }
 192        else {
 193                /* check for zero */
 194                if (Sgl_iszero_mantissa(opnd2)) {
 195                        Sgl_setzero_exponentmantissa(result);
 196                        *dstptr = result;
 197                        return(NOEXCEPTION);
 198                }
 199                /* is denormalized; want to normalize */
 200                Sgl_clear_signexponent(opnd2);
 201                Sgl_leftshiftby1(opnd2);
 202                Sgl_normalize(opnd2,dest_exponent);
 203        }
 204
 205        /* Multiply two source mantissas together */
 206
 207        Sgl_leftshiftby4(opnd2);     /* make room for guard bits */
 208        Sgl_setzero(opnd3);
 209        /*
 210         * Four bits at a time are inspected in each loop, and a
 211         * simple shift and add multiply algorithm is used.
 212         */
 213        for (count=1;count<SGL_P;count+=4) {
 214                stickybit |= Slow4(opnd3);
 215                Sgl_rightshiftby4(opnd3);
 216                if (Sbit28(opnd1)) Sall(opnd3) += (Sall(opnd2) << 3);
 217                if (Sbit29(opnd1)) Sall(opnd3) += (Sall(opnd2) << 2);
 218                if (Sbit30(opnd1)) Sall(opnd3) += (Sall(opnd2) << 1);
 219                if (Sbit31(opnd1)) Sall(opnd3) += Sall(opnd2);
 220                Sgl_rightshiftby4(opnd1);
 221        }
 222        /* make sure result is left-justified */
 223        if (Sgl_iszero_sign(opnd3)) {
 224                Sgl_leftshiftby1(opnd3);
 225        }
 226        else {
 227                /* result mantissa >= 2. */
 228                dest_exponent++;
 229        }
 230        /* check for denormalized result */
 231        while (Sgl_iszero_sign(opnd3)) {
 232                Sgl_leftshiftby1(opnd3);
 233                dest_exponent--;
 234        }
 235        /*
 236         * check for guard, sticky and inexact bits
 237         */
 238        stickybit |= Sgl_all(opnd3) << (SGL_BITLENGTH - SGL_EXP_LENGTH + 1);
 239        guardbit = Sbit24(opnd3);
 240        inexact = guardbit | stickybit;
 241
 242        /* re-align mantissa */
 243        Sgl_rightshiftby8(opnd3);
 244
 245        /* 
 246         * round result 
 247         */
 248        if (inexact && (dest_exponent>0 || Is_underflowtrap_enabled())) {
 249                Sgl_clear_signexponent(opnd3);
 250                switch (Rounding_mode()) {
 251                        case ROUNDPLUS: 
 252                                if (Sgl_iszero_sign(result)) 
 253                                        Sgl_increment(opnd3);
 254                                break;
 255                        case ROUNDMINUS: 
 256                                if (Sgl_isone_sign(result)) 
 257                                        Sgl_increment(opnd3);
 258                                break;
 259                        case ROUNDNEAREST:
 260                                if (guardbit) {
 261                                if (stickybit || Sgl_isone_lowmantissa(opnd3))
 262                                Sgl_increment(opnd3);
 263                                }
 264                }
 265                if (Sgl_isone_hidden(opnd3)) dest_exponent++;
 266        }
 267        Sgl_set_mantissa(result,opnd3);
 268
 269        /* 
 270         * Test for overflow
 271         */
 272        if (dest_exponent >= SGL_INFINITY_EXPONENT) {
 273                /* trap if OVERFLOWTRAP enabled */
 274                if (Is_overflowtrap_enabled()) {
 275                        /*
 276                         * Adjust bias of result
 277                         */
 278                        Sgl_setwrapped_exponent(result,dest_exponent,ovfl);
 279                        *dstptr = result;
 280                        if (inexact) 
 281                            if (Is_inexacttrap_enabled())
 282                                return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
 283                            else Set_inexactflag();
 284                        return(OVERFLOWEXCEPTION);
 285                }
 286                inexact = TRUE;
 287                Set_overflowflag();
 288                /* set result to infinity or largest number */
 289                Sgl_setoverflow(result);
 290        }
 291        /* 
 292         * Test for underflow
 293         */
 294        else if (dest_exponent <= 0) {
 295                /* trap if UNDERFLOWTRAP enabled */
 296                if (Is_underflowtrap_enabled()) {
 297                        /*
 298                         * Adjust bias of result
 299                         */
 300                        Sgl_setwrapped_exponent(result,dest_exponent,unfl);
 301                        *dstptr = result;
 302                        if (inexact) 
 303                            if (Is_inexacttrap_enabled())
 304                                return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
 305                            else Set_inexactflag();
 306                        return(UNDERFLOWEXCEPTION);
 307                }
 308
 309                /* Determine if should set underflow flag */
 310                is_tiny = TRUE;
 311                if (dest_exponent == 0 && inexact) {
 312                        switch (Rounding_mode()) {
 313                        case ROUNDPLUS: 
 314                                if (Sgl_iszero_sign(result)) {
 315                                        Sgl_increment(opnd3);
 316                                        if (Sgl_isone_hiddenoverflow(opnd3))
 317                                            is_tiny = FALSE;
 318                                        Sgl_decrement(opnd3);
 319                                }
 320                                break;
 321                        case ROUNDMINUS: 
 322                                if (Sgl_isone_sign(result)) {
 323                                        Sgl_increment(opnd3);
 324                                        if (Sgl_isone_hiddenoverflow(opnd3))
 325                                            is_tiny = FALSE;
 326                                        Sgl_decrement(opnd3);
 327                                }
 328                                break;
 329                        case ROUNDNEAREST:
 330                                if (guardbit && (stickybit || 
 331                                    Sgl_isone_lowmantissa(opnd3))) {
 332                                        Sgl_increment(opnd3);
 333                                        if (Sgl_isone_hiddenoverflow(opnd3))
 334                                            is_tiny = FALSE;
 335                                        Sgl_decrement(opnd3);
 336                                }
 337                                break;
 338                        }
 339                }
 340
 341                /*
 342                 * denormalize result or set to signed zero
 343                 */
 344                stickybit = inexact;
 345                Sgl_denormalize(opnd3,dest_exponent,guardbit,stickybit,inexact);
 346
 347                /* return zero or smallest number */
 348                if (inexact) {
 349                        switch (Rounding_mode()) {
 350                        case ROUNDPLUS: 
 351                                if (Sgl_iszero_sign(result)) {
 352                                        Sgl_increment(opnd3);
 353                                }
 354                                break;
 355                        case ROUNDMINUS: 
 356                                if (Sgl_isone_sign(result)) {
 357                                        Sgl_increment(opnd3);
 358                                }
 359                                break;
 360                        case ROUNDNEAREST:
 361                                if (guardbit && (stickybit || 
 362                                    Sgl_isone_lowmantissa(opnd3))) {
 363                                        Sgl_increment(opnd3);
 364                                }
 365                                break;
 366                        }
 367                if (is_tiny) Set_underflowflag();
 368                }
 369                Sgl_set_exponentmantissa(result,opnd3);
 370        }
 371        else Sgl_set_exponent(result,dest_exponent);
 372        *dstptr = result;
 373
 374        /* check for inexact */
 375        if (inexact) {
 376                if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
 377                else Set_inexactflag();
 378        }
 379        return(NOEXCEPTION);
 380}
 381