fcomp_ST0_ST1.java

/*
    JPC: An x86 PC Hardware Emulator for a pure Java Virtual Machine

    Copyright (C) 2012-2013 Ian Preston

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License version 2 as published by
    the Free Software Foundation.

    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, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
    Details (including contact information) can be found at: 

    jpc.sourceforge.net
    or the developer website
    sourceforge.net/projects/jpc/

    End of licence header
*/

package org.jpc.emulator.execution.opcodes.pm;

import org.jpc.emulator.execution.*;
import org.jpc.emulator.execution.decoder.*;
import org.jpc.emulator.processor.*;
import org.jpc.emulator.processor.fpu64.*;
import static org.jpc.emulator.processor.Processor.*;

public class fcomp_ST0_ST1 extends Executable
{

    public fcomp_ST0_ST1(int blockStart, int eip, int prefices, PeekableInputStream input)
    {
        super(blockStart, eip);
        int modrm = input.readU8();
    }

    public Branch execute(Processor cpu)
    {
                            int newcode = 0xd;
        double freg0 = cpu.fpu.ST(0);
        double freg1 = cpu.fpu.ST(1);
        if (Double.isNaN(freg0) || Double.isNaN(freg1))
            cpu.fpu.setInvalidOperation();
        else {
            if (freg0 > freg1) newcode = 0;
            else if (freg0 < freg1) newcode = 1;
            else newcode = 8;
        }
        cpu.fpu.conditionCode &= 2;
        cpu.fpu.conditionCode |= newcode;
        cpu.fpu.pop();
        return Branch.None;
    }

    public boolean isBranch()
    {
        return false;
    }

    public String toString()
    {
        return this.getClass().getName();
    }
}