ANDI.java

/*
 * ANDI.java
 *
 * 8th may 2006
 * Instruction ANDI of the MIPS64 Instruction Set
 * (c) 2006 EduMips64 project - Trubia Massimo, Russo Daniele
 *
 * This file is part of the EduMIPS64 project, and is released under the GNU
 * General Public License.
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package org.edumips64.core.is;
import org.edumips64.core.*;
import org.edumips64.utils.*;


/** <pre>
 *        Syntax: ANDI rt, rs, immediate
 *   Description: rt = rs AND immediate
 *                Does a bitwise logical AND with a constant
 *                The 16-bit immediate is zero-extended to the left and combined
 *                with the contents of GPR rs in a bitwise logical AND
 *                operation. The result is placed into GPR rt.
 *</pre>
  * @author Trubia Massimo, Russo Daniele
 */
class ANDI extends ALU_IType {
  final String OPCODE_VALUE = "001100";

  ANDI() {
    super.OPCODE_VALUE = OPCODE_VALUE;
    this.name = "ANDI";
  }
  //since this operation is carried out with zero padding of immediate, against sign_extend(immediate) methodology
  //of all others instructions in the same category, is necessary the overriding of ID method
  public void ID() throws RAWException, IrregularWriteOperationException, IrregularStringOfBitsException {
    //if the source register is valid passing its own values into a temporary register
    Register rs = cpu.getRegister(params.get(RS_FIELD));

    if (rs.getWriteSemaphore() > 0) {
      throw new RAWException();
    }

    TR[RS_FIELD] = rs;
    //locking the target register
    Register rt = cpu.getRegister(params.get(RT_FIELD));
    rt.incrWriteSemaphore();
    //writing the immediate value of "params" on a temporary register
    TR[IMM_FIELD].writeHalf(params.get(IMM_FIELD));
    //forcing zero-padding in the same temporary register
    StringBuffer sb = new StringBuffer();

    for (int i = 0; i < 48; i++) {
      sb.append('0');
    }

    sb.append(TR[IMM_FIELD].getBinString().substring(48, 64));
    TR[IMM_FIELD].setBits(sb.substring(0), 0);

  }
  public void EX() throws IrregularStringOfBitsException {
    //getting values from temporary registers
    String imm = TR[IMM_FIELD].getBinString();
    String rs = TR[RS_FIELD].getBinString();
    StringBuffer sb = new StringBuffer();
    boolean immbit, rsbit, resbit;

    //performing bitwise OR between immediate and rs register
    for (int i = 0; i < 64; i++) {
      rsbit = rs.charAt(i) == '1' ? true : false;
      immbit = imm.charAt(i) == '1' ? true : false;
      resbit = rsbit && immbit;
      sb.append(resbit ? '1' : '0');
    }

    TR[RT_FIELD].setBits(sb.substring(0), 0);

    if (cpu.isEnableForwarding()) {
      doWB();
    }

  }

}