sim/erc32/float.c

   1 /*
   2  * This file is part of SIS.
   3  *
   4  * SIS, SPARC instruction simulator. Copyright (C) 1995 Jiri Gaisler, European
   5  * Space Agency
   6  *
   7  * This program is free software; you can redistribute it and/or modify it under
   8  * the terms of the GNU General Public License as published by the Free
   9  * Software Foundation; either version 3 of the License, or (at your option)
  10  * any later version.
  11  *
  12  * This program is distributed in the hope that 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 for
  15  * more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along with
  18  * this program; if not, see <http://www.gnu.org/licenses/>.
  19  *
  20  *
  21  * This file implements the interface between the host and the simulated
  22  * FPU. IEEE trap handling is done as follows:
  23  * 1. In the host, all IEEE traps are masked
  24  * 2. After each simulated FPU instruction, check if any exception occured
  25  *    by reading the exception bits from the host FPU status register
  26  *    (get_accex()).
  27  * 3. Propagate any exceptions to the simulated FSR.
  28  * 4. Clear host exception bits
  29  *
  30  *
  31  */
  32
  33 #include "config.h"
  34 #include "sis.h"
  35 #include <fenv.h>
  36
  37 /* This routine should return the accrued exceptions */
  38 int
  39 get_accex()
  40 {
  41     int fexc, accx;
  42
  43     fexc = fetestexcept (FE_ALL_EXCEPT);
  44     accx = 0;
  45     if (fexc & FE_INEXACT)
  46         accx |= 1;
  47     if (fexc & FE_DIVBYZERO)
  48         accx |= 2;
  49     if (fexc & FE_UNDERFLOW)
  50         accx |= 4;
  51     if (fexc & FE_OVERFLOW)
  52         accx |= 8;
  53     if (fexc & FE_INVALID)
  54         accx |= 0x10;
  55     return(accx);
  56 }
  57
  58 /* How to clear the accrued exceptions */
  59 void
  60 clear_accex()
  61 {
  62     feclearexcept (FE_ALL_EXCEPT);
  63 }
  64
  65 /* How to map SPARC FSR onto the host */
  66 void
  67 set_fsr(fsr)
  68 uint32 fsr;
  69 {
  70     int fround;
  71
  72     fsr >>= 30;
  73     switch (fsr) {
  74         case 0:
  75             fround = FE_TONEAREST;
  76             break;
  77         case 1:
  78             fround = FE_TOWARDZERO;
  79             break;
  80         case 2:
  81             fround = FE_UPWARD;
  82             break;
  83         case 3:
  84             fround = FE_DOWNWARD;
  85             break;
  86      }
  87      fesetround (fround);
  88 }