kernel/arch/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         case IEEE754_CLASS_INF:
  42                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  43                 return ieee754si_indef();
  44
  45         case IEEE754_CLASS_ZERO:
  46                 return 0;
  47
  48         case IEEE754_CLASS_DNORM:
  49         case IEEE754_CLASS_NORM:
  50                 break;
  51         }
  52         if (xe > 31) {
  53                 /* Set invalid. We will only use overflow for floating
  54                    point overflow */
  55                 ieee754_setcx(IEEE754_INVALID_OPERATION);
  56                 return ieee754si_indef();
  57         }
  58         /* oh gawd */
  59         if (xe > DP_FBITS) {
  60                 xm <<= xe - DP_FBITS;
  61         } else if (xe < DP_FBITS) {
  62                 if (xe < -1) {
  63                         residue = xm;
  64                         round = 0;
  65                         sticky = residue != 0;
  66                         xm = 0;
  67                 } else {
  68                         residue = xm << (64 - DP_FBITS + xe);
  69                         round = (residue >> 63) != 0;
  70                         sticky = (residue << 1) != 0;
  71                         xm >>= DP_FBITS - xe;
  72                 }
  73                 /* Note: At this point upper 32 bits of xm are guaranteed
  74                    to be zero */
  75                 odd = (xm & 0x1) != 0x0;
  76                 switch (ieee754_csr.rm) {
  77                 case FPU_CSR_RN:
  78                         if (round && (sticky || odd))
  79                                 xm++;
  80                         break;
  81                 case FPU_CSR_RZ:
  82                         break;
  83                 case FPU_CSR_RU:        /* toward +Infinity */
  84                         if ((round || sticky) && !xs)
  85                                 xm++;
  86                         break;
  87                 case FPU_CSR_RD:        /* toward -Infinity */
  88                         if ((round || sticky) && xs)
  89                                 xm++;
  90                         break;
  91                 }
  92                 /* look for valid corner case 0x80000000 */
  93                 if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
  94                         /* This can happen after rounding */
  95                         ieee754_setcx(IEEE754_INVALID_OPERATION);
  96                         return ieee754si_indef();
  97                 }
  98                 if (round || sticky)
  99                         ieee754_setcx(IEEE754_INEXACT);
 100         }
 101         if (xs)
 102                 return -xm;
 103         else
 104                 return xm;
 105 }