arch/parisc/math-emu/sfrem.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/sfrem.c               $Revision: 1.1 $
  26  *
  27  *  Purpose:
  28  *      Single Precision Floating-point Remainder
  29  *
  30  *  External Interfaces:
  31  *      sgl_frem(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
  43 #include "float.h"
  44 #include "sgl_float.h"
  45
  46 /*
  47  *  Single Precision Floating-point Remainder
  48  */
  49
  50 int
  51 sgl_frem (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
  52           sgl_floating_point * dstptr, unsigned int *status)
  53 {
  54         register unsigned int opnd1, opnd2, result;
  55         register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
  56         register boolean roundup = FALSE;
  57
  58         opnd1 = *srcptr1;
  59         opnd2 = *srcptr2;
  60         /*
  61          * check first operand for NaN's or infinity
  62          */
  63         if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
  64                 if (Sgl_iszero_mantissa(opnd1)) {
  65                         if (Sgl_isnotnan(opnd2)) {
  66                                 /* invalid since first operand is infinity */
  67                                 if (Is_invalidtrap_enabled())
  68                                         return(INVALIDEXCEPTION);
  69                                 Set_invalidflag();
  70                                 Sgl_makequietnan(result);
  71                                 *dstptr = result;
  72                                 return(NOEXCEPTION);
  73                         }
  74                 }
  75                 else {
  76                         /*
  77                          * is NaN; signaling or quiet?
  78                          */
  79                         if (Sgl_isone_signaling(opnd1)) {
  80                                 /* trap if INVALIDTRAP enabled */
  81                                 if (Is_invalidtrap_enabled())
  82                                         return(INVALIDEXCEPTION);
  83                                 /* make NaN quiet */
  84                                 Set_invalidflag();
  85                                 Sgl_set_quiet(opnd1);
  86                         }
  87                         /*
  88                          * is second operand a signaling NaN?
  89                          */
  90                         else if (Sgl_is_signalingnan(opnd2)) {
  91                                 /* trap if INVALIDTRAP enabled */
  92                                 if (Is_invalidtrap_enabled())
  93                                         return(INVALIDEXCEPTION);
  94                                 /* make NaN quiet */
  95                                 Set_invalidflag();
  96                                 Sgl_set_quiet(opnd2);
  97                                 *dstptr = opnd2;
  98                                 return(NOEXCEPTION);
  99                         }
 100                         /*
 101                          * return quiet NaN
 102                          */
 103                         *dstptr = opnd1;
 104                         return(NOEXCEPTION);
 105                 }
 106         }
 107         /*
 108          * check second operand for NaN's or infinity
 109          */
 110         if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
 111                 if (Sgl_iszero_mantissa(opnd2)) {
 112                         /*
 113                          * return first operand
 114                          */
 115                         *dstptr = opnd1;
 116                         return(NOEXCEPTION);
 117                 }
 118                 /*
 119                  * is NaN; signaling or quiet?
 120                  */
 121                 if (Sgl_isone_signaling(opnd2)) {
 122                         /* trap if INVALIDTRAP enabled */
 123                         if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
 124                         /* make NaN quiet */
 125                         Set_invalidflag();
 126                         Sgl_set_quiet(opnd2);
 127                 }
 128                 /*
 129                  * return quiet NaN
 130                  */
 131                 *dstptr = opnd2;
 132                 return(NOEXCEPTION);
 133         }
 134         /*
 135          * check second operand for zero
 136          */
 137         if (Sgl_iszero_exponentmantissa(opnd2)) {
 138                 /* invalid since second operand is zero */
 139                 if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
 140                 Set_invalidflag();
 141                 Sgl_makequietnan(result);
 142                 *dstptr = result;
 143                 return(NOEXCEPTION);
 144         }
 145
 146         /*
 147          * get sign of result
 148          */
 149         result = opnd1;
 150
 151         /*
 152          * check for denormalized operands
 153          */
 154         if (opnd1_exponent == 0) {
 155                 /* check for zero */
 156                 if (Sgl_iszero_mantissa(opnd1)) {
 157                         *dstptr = opnd1;
 158                         return(NOEXCEPTION);
 159                 }
 160                 /* normalize, then continue */
 161                 opnd1_exponent = 1;
 162                 Sgl_normalize(opnd1,opnd1_exponent);
 163         }
 164         else {
 165                 Sgl_clear_signexponent_set_hidden(opnd1);
 166         }
 167         if (opnd2_exponent == 0) {
 168                 /* normalize, then continue */
 169                 opnd2_exponent = 1;
 170                 Sgl_normalize(opnd2,opnd2_exponent);
 171         }
 172         else {
 173                 Sgl_clear_signexponent_set_hidden(opnd2);
 174         }
 175
 176         /* find result exponent and divide step loop count */
 177         dest_exponent = opnd2_exponent - 1;
 178         stepcount = opnd1_exponent - opnd2_exponent;
 179
 180         /*
 181          * check for opnd1/opnd2 < 1
 182          */
 183         if (stepcount < 0) {
 184                 /*
 185                  * check for opnd1/opnd2 > 1/2
 186                  *
 187                  * In this case n will round to 1, so
 188                  *    r = opnd1 - opnd2
 189                  */
 190                 if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
 191                         Sgl_all(result) = ~Sgl_all(result);   /* set sign */
 192                         /* align opnd2 with opnd1 */
 193                         Sgl_leftshiftby1(opnd2);
 194                         Sgl_subtract(opnd2,opnd1,opnd2);
 195                         /* now normalize */
 196                         while (Sgl_iszero_hidden(opnd2)) {
 197                                 Sgl_leftshiftby1(opnd2);
 198                                 dest_exponent--;
 199                         }
 200                         Sgl_set_exponentmantissa(result,opnd2);
 201                         goto testforunderflow;
 202                 }
 203                 /*
 204                  * opnd1/opnd2 <= 1/2
 205                  *
 206                  * In this case n will round to zero, so
 207                  *    r = opnd1
 208                  */
 209                 Sgl_set_exponentmantissa(result,opnd1);
 210                 dest_exponent = opnd1_exponent;
 211                 goto testforunderflow;
 212         }
 213
 214         /*
 215          * Generate result
 216          *
 217          * Do iterative subtract until remainder is less than operand 2.
 218          */
 219         while (stepcount-- > 0 && Sgl_all(opnd1)) {
 220                 if (Sgl_isnotlessthan(opnd1,opnd2))
 221                         Sgl_subtract(opnd1,opnd2,opnd1);
 222                 Sgl_leftshiftby1(opnd1);
 223         }
 224         /*
 225          * Do last subtract, then determine which way to round if remainder
 226          * is exactly 1/2 of opnd2
 227          */
 228         if (Sgl_isnotlessthan(opnd1,opnd2)) {
 229                 Sgl_subtract(opnd1,opnd2,opnd1);
 230                 roundup = TRUE;
 231         }
 232         if (stepcount > 0 || Sgl_iszero(opnd1)) {
 233                 /* division is exact, remainder is zero */
 234                 Sgl_setzero_exponentmantissa(result);
 235                 *dstptr = result;
 236                 return(NOEXCEPTION);
 237         }
 238
 239         /*
 240          * Check for cases where opnd1/opnd2 < n
 241          *
 242          * In this case the result's sign will be opposite that of
 243          * opnd1.  The mantissa also needs some correction.
 244          */
 245         Sgl_leftshiftby1(opnd1);
 246         if (Sgl_isgreaterthan(opnd1,opnd2)) {
 247                 Sgl_invert_sign(result);
 248                 Sgl_subtract((opnd2<<1),opnd1,opnd1);
 249         }
 250         /* check for remainder being exactly 1/2 of opnd2 */
 251         else if (Sgl_isequal(opnd1,opnd2) && roundup) {
 252                 Sgl_invert_sign(result);
 253         }
 254
 255         /* normalize result's mantissa */
 256         while (Sgl_iszero_hidden(opnd1)) {
 257                 dest_exponent--;
 258                 Sgl_leftshiftby1(opnd1);
 259         }
 260         Sgl_set_exponentmantissa(result,opnd1);
 261
 262         /*
 263          * Test for underflow
 264          */
 265     testforunderflow:
 266         if (dest_exponent <= 0) {
 267                 /* trap if UNDERFLOWTRAP enabled */
 268                 if (Is_underflowtrap_enabled()) {
 269                         /*
 270                          * Adjust bias of result
 271                          */
 272                         Sgl_setwrapped_exponent(result,dest_exponent,unfl);
 273                         *dstptr = result;
 274                         /* frem is always exact */
 275                         return(UNDERFLOWEXCEPTION);
 276                 }
 277                 /*
 278                  * denormalize result or set to signed zero
 279                  */
 280                 if (dest_exponent >= (1 - SGL_P)) {
 281                         Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
 282                 }
 283                 else {
 284                         Sgl_setzero_exponentmantissa(result);
 285                 }
 286         }
 287         else Sgl_set_exponent(result,dest_exponent);
 288         *dstptr = result;
 289         return(NOEXCEPTION);
 290 }