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  * ########################################################################
   9  *
  10  *  This program is free software; you can distribute it and/or modify it
  11  *  under the terms of the GNU General Public License (Version 2) as
  12  *  published by the Free Software Foundation.
  13  *
  14  *  This program is distributed in the hope it will be useful, but WITHOUT
  15  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  17  *  for more details.
  18  *
  19  *  You should have received a copy of the GNU General Public License along
  20  *  with this program; if not, write to the Free Software Foundation, Inc.,
  21  *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  22  *
  23  * ########################################################################
  24  */
  25
  26
  27 #include <linux/kernel.h>
  28 #include "ieee754dp.h"
  29
  30 int ieee754dp_tint(ieee754dp x)
  31 {
  32         COMPXDP;
  33
  34         CLEARCX;
  35
  36         EXPLODEXDP;
  37         FLUSHXDP;
  38
  39         switch (xc) {
  40         case IEEE754_CLASS_SNAN:
  41         case IEEE754_CLASS_QNAN:
  42         case IEEE754_CLASS_INF:
  43                 SETCX(IEEE754_INVALID_OPERATION);
  44                 return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
  45         case IEEE754_CLASS_ZERO:
  46                 return 0;
  47         case IEEE754_CLASS_DNORM:
  48         case IEEE754_CLASS_NORM:
  49                 break;
  50         }
  51         if (xe > 31) {
  52                 /* Set invalid. We will only use overflow for floating
  53                    point overflow */
  54                 SETCX(IEEE754_INVALID_OPERATION);
  55                 return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
  56         }
  57         /* oh gawd */
  58         if (xe > DP_MBITS) {
  59                 xm <<= xe - DP_MBITS;
  60         } else if (xe < DP_MBITS) {
  61                 u64 residue;
  62                 int round;
  63                 int sticky;
  64                 int odd;
  65
  66                 if (xe < -1) {
  67                         residue = xm;
  68                         round = 0;
  69                         sticky = residue != 0;
  70                         xm = 0;
  71                 } else {
  72                         residue = xm << (64 - DP_MBITS + xe);
  73                         round = (residue >> 63) != 0;
  74                         sticky = (residue << 1) != 0;
  75                         xm >>= DP_MBITS - xe;
  76                 }
  77                 /* Note: At this point upper 32 bits of xm are guaranteed
  78                    to be zero */
  79                 odd = (xm & 0x1) != 0x0;
  80                 switch (ieee754_csr.rm) {
  81                 case IEEE754_RN:
  82                         if (round && (sticky || odd))
  83                                 xm++;
  84                         break;
  85                 case IEEE754_RZ:
  86                         break;
  87                 case IEEE754_RU:        /* toward +Infinity */
  88                         if ((round || sticky) && !xs)
  89                                 xm++;
  90                         break;
  91                 case IEEE754_RD:        /* toward -Infinity */
  92                         if ((round || sticky) && xs)
  93                                 xm++;
  94                         break;
  95                 }
  96                 /* look for valid corner case 0x80000000 */
  97                 if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
  98                         /* This can happen after rounding */
  99                         SETCX(IEEE754_INVALID_OPERATION);
 100                         return ieee754si_xcpt(ieee754si_indef(), "dp_tint", x);
 101                 }
 102                 if (round || sticky)
 103                         SETCX(IEEE754_INEXACT);
 104         }
 105         if (xs)
 106                 return -xm;
 107         else
 108                 return xm;
 109 }
 110
 111
 112 unsigned int ieee754dp_tuns(ieee754dp x)
 113 {
 114         ieee754dp hb = ieee754dp_1e31();
 115
 116         /* what if x < 0 ?? */
 117         if (ieee754dp_lt(x, hb))
 118                 return (unsigned) ieee754dp_tint(x);
 119
 120         return (unsigned) ieee754dp_tint(ieee754dp_sub(x, hb)) |
 121             ((unsigned) 1 << 31);
 122 }