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#include "ieee754dp.h"
  24
  25s64 ieee754sp_tlong(union ieee754sp x)
  26{
  27        u32 residue;
  28        int round;
  29        int sticky;
  30        int odd;
  31
  32        COMPXDP;                /* <-- need 64-bit mantissa tmp */
  33
  34        ieee754_clearcx();
  35
  36        EXPLODEXSP;
  37        FLUSHXSP;
  38
  39        switch (xc) {
  40        case IEEE754_CLASS_SNAN:
  41        case IEEE754_CLASS_QNAN:
  42        case IEEE754_CLASS_INF:
  43                ieee754_setcx(IEEE754_INVALID_OPERATION);
  44                return ieee754di_indef();
  45
  46        case IEEE754_CLASS_ZERO:
  47                return 0;
  48
  49        case IEEE754_CLASS_DNORM:
  50        case IEEE754_CLASS_NORM:
  51                break;
  52        }
  53        if (xe >= 63) {
  54                /* look for valid corner case */
  55                if (xe == 63 && xs && xm == SP_HIDDEN_BIT)
  56                        return -0x8000000000000000LL;
  57                /* Set invalid. We will only use overflow for floating
  58                   point overflow */
  59                ieee754_setcx(IEEE754_INVALID_OPERATION);
  60                return ieee754di_indef();
  61        }
  62        /* oh gawd */
  63        if (xe > SP_FBITS) {
  64                xm <<= xe - SP_FBITS;
  65        } else if (xe < SP_FBITS) {
  66                if (xe < -1) {
  67                        residue = xm;
  68                        round = 0;
  69                        sticky = residue != 0;
  70                        xm = 0;
  71                } else {
  72                        residue = xm << (32 - SP_FBITS + xe);
  73                        round = (residue >> 31) != 0;
  74                        sticky = (residue << 1) != 0;
  75                        xm >>= SP_FBITS - xe;
  76                }
  77                odd = (xm & 0x1) != 0x0;
  78                switch (ieee754_csr.rm) {
  79                case FPU_CSR_RN:
  80                        if (round && (sticky || odd))
  81                                xm++;
  82                        break;
  83                case FPU_CSR_RZ:
  84                        break;
  85                case FPU_CSR_RU:        /* toward +Infinity */
  86                        if ((round || sticky) && !xs)
  87                                xm++;
  88                        break;
  89                case FPU_CSR_RD:        /* toward -Infinity */
  90                        if ((round || sticky) && xs)
  91                                xm++;
  92                        break;
  93                }
  94                if ((xm >> 63) != 0) {
  95                        /* This can happen after rounding */
  96                        ieee754_setcx(IEEE754_INVALID_OPERATION);
  97                        return ieee754di_indef();
  98                }
  99                if (round || sticky)
 100                        ieee754_setcx(IEEE754_INEXACT);
 101        }
 102        if (xs)
 103                return -xm;
 104        else
 105                return xm;
 106}
 107