old-cross-binutils/sim/erc32/float.c

/*
 * This file is part of SIS.
 *
 * SIS, SPARC instruction simulator. Copyright (C) 1995 Jiri Gaisler, European
 * Space Agency
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 3 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, see <http://www.gnu.org/licenses/>.
 *
 *
 * This file implements the interface between the host and the simulated
 * FPU. IEEE trap handling is done as follows: 
 * 1. In the host, all IEEE traps are masked
 * 2. After each simulated FPU instruction, check if any exception occured 
 *    by reading the exception bits from the host FPU status register 
 *    (get_accex()).
 * 3. Propagate any exceptions to the simulated FSR.
 * 4. Clear host exception bits
 *
 *
 */

#include "config.h"
#include "sis.h"
#include <fenv.h>

/* This routine should return the accrued exceptions */
int
get_accex()
{
    int fexc, accx;

    fexc = fetestexcept (FE_ALL_EXCEPT);
    accx = 0;
    if (fexc & FE_INEXACT)
        accx |= 1;
    if (fexc & FE_DIVBYZERO)
        accx |= 2;
    if (fexc & FE_UNDERFLOW)
        accx |= 4;
    if (fexc & FE_OVERFLOW)
        accx |= 8;
    if (fexc & FE_INVALID)
        accx |= 0x10;
    return accx;
}

/* How to clear the accrued exceptions */
void
clear_accex()
{
    feclearexcept (FE_ALL_EXCEPT);
}

/* How to map SPARC FSR onto the host */
void
set_fsr(fsr)
uint32 fsr;
{
    int fround;

    fsr >>= 30;
    switch (fsr) {
	case 0: 
	    fround = FE_TONEAREST;
	    break;
	case 1:
	    fround = FE_TOWARDZERO;
	    break;
	case 2:
	    fround = FE_UPWARD;
	    break;
	case 3:
	    fround = FE_DOWNWARD;
	    break;
     }
     fesetround (fround);
}