mips/math-emu/dp_tint.c

   1 /* IEEE754 floating point arithmetic
   2  * double precision: common utilities
   3  */
   4 /*
   5  * MIPS floating point support
   6  * Copyright (C) 1994-2000 Algorithmics Ltd.
   7  *
   8  *  This program is free software; you can distribute it and/or modify it
   9  *  under the terms of the GNU General Public License (Version 2) as
  10  *  published by the Free Software Foundation.
  11  *
  12  *  This program is distributed in the hope it will be useful, but WITHOUT
  13  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15  *  for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License along
  18  *  with this program; if not, write to the Free Software Foundation, Inc.,
  19  *  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
  20  */
  21
  22 #include "ieee754dp.h"
  23
  24 int ieee754dp_tint(union ieee754dp x)
  25 {
  26         u64 residue;
  27         int round;
  28         int sticky;
  29         int odd;
  30
  31         COMPXDP;
  32
  33         ieee754_clearcx();
  34
  35         EXPLODEXDP;
  36         FLUSHXDP;
  37
  38         switch (xc) {
  39         case IEEE754_CLASS_SNAN:
  40         case IEEE754_CLASS_QNAN:
  41                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  42                 return ieee754si_indef();
  43
  44         case IEEE754_CLASS_INF:
  45                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  46                 return ieee754si_overflow(xs);
  47
  48         case IEEE754_CLASS_ZERO:
  49                 return 0;
  50
  51         case IEEE754_CLASS_DNORM:
  52         case IEEE754_CLASS_NORM:
  53                 break;
  54         }
  55         if (xe > 31) {
  56                 /* Set invalid. We will only use overflow for floating
  57                    point overflow */
  58                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  59                 return ieee754si_overflow(xs);
  60         }
  61         /* oh gawd */
  62         if (xe > DP_FBITS) {
  63                 xm <<= xe - DP_FBITS;
  64         } else if (xe < DP_FBITS) {
  65                 if (xe < -1) {
  66                         residue = xm;
  67                         round = 0;
  68                         sticky = residue != 0;
  69                         xm = 0;
  70                 } else {
  71                         residue = xm << (64 - DP_FBITS + xe);
  72                         round = (residue >> 63) != 0;
  73                         sticky = (residue << 1) != 0;
  74                         xm >>= DP_FBITS - xe;
  75                 }
  76                 /* Note: At this point upper 32 bits of xm are guaranteed
  77                    to be zero */
  78                 odd = (xm & 0x1) != 0x0;
  79                 switch (ieee754_csr.rm) {
  80                 case FPU_CSR_RN:
  81                         if (round && (sticky || odd))
  82                                 xm++;
  83                         break;
  84                 case FPU_CSR_RZ:
  85                         break;
  86                 case FPU_CSR_RU:        /* toward +Infinity */
  87                         if ((round || sticky) && !xs)
  88                                 xm++;
  89                         break;
  90                 case FPU_CSR_RD:        /* toward -Infinity */
  91                         if ((round || sticky) && xs)
  92                                 xm++;
  93                         break;
  94                 }
  95                 /* look for valid corner case 0x80000000 */
  96                 if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
  97                         /* This can happen after rounding */
  98                         ieee754_setcx(IEEE754_INVALID_OPERATION);
  99                         return ieee754si_overflow(xs);
 100                 }
 101                 if (round || sticky)
 102                         ieee754_setcx(IEEE754_INEXACT);
 103         }
 104         if (xs)
 105                 return -xm;
 106         else
 107                 return xm;
 108 }