LXR linux/arch/mips/math-emu/sp

   1/* IEEE754 floating point arithmetic
   2 * single precision
   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 "ieee754sp.h"
  23
  24int ieee754sp_tint(union ieee754sp x)
  25{
  26        u32 residue;
  27        int round;
  28        int sticky;
  29        int odd;
  30
  31        COMPXSP;
  32
  33        ieee754_clearcx();
  34
  35        EXPLODEXSP;
  36        FLUSHXSP;
  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                /* look for valid corner case */
  57                if (xe == 31 && xs && xm == SP_HIDDEN_BIT)
  58                        return -0x80000000;
  59                /* Set invalid. We will only use overflow for floating
  60                   point overflow */
  61                ieee754_setcx(IEEE754_INVALID_OPERATION);
  62                return ieee754si_overflow(xs);
  63        }
  64        /* oh gawd */
  65        if (xe > SP_FBITS) {
  66                xm <<= xe - SP_FBITS;
  67        } else {
  68                if (xe < -1) {
  69                        residue = xm;
  70                        round = 0;
  71                        sticky = residue != 0;
  72                        xm = 0;
  73                } else {
  74                        /* Shifting a u32 32 times does not work,
  75                        * so we do it in two steps. Be aware that xe
  76                        * may be -1 */
  77                        residue = xm << (xe + 1);
  78                        residue <<= 31 - SP_FBITS;
  79                        round = (residue >> 31) != 0;
  80                        sticky = (residue << 1) != 0;
  81                        xm >>= SP_FBITS - xe;
  82                }
  83                odd = (xm & 0x1) != 0x0;
  84                switch (ieee754_csr.rm) {
  85                case FPU_CSR_RN:
  86                        if (round && (sticky || odd))
  87                                xm++;
  88                        break;
  89                case FPU_CSR_RZ:
  90                        break;
  91                case FPU_CSR_RU:        /* toward +Infinity */
  92                        if ((round || sticky) && !xs)
  93                                xm++;
  94                        break;
  95                case FPU_CSR_RD:        /* toward -Infinity */
  96                        if ((round || sticky) && xs)
  97                                xm++;
  98                        break;
  99                }
 100                if ((xm >> 31) != 0) {
 101                        /* This can happen after rounding */
 102                        ieee754_setcx(IEEE754_INVALID_OPERATION);
 103                        return ieee754si_overflow(xs);
 104                }
 105                if (round || sticky)
 106                        ieee754_setcx(IEEE754_INEXACT);
 107        }
 108        if (xs)
 109                return -xm;
 110        else
 111                return xm;
 112}
 113