simpleinstr.java

用Java实现的编译器。把源代码编译成SPARC汇编程序

// $Id: SimpleInstr.java,v 1.3 1999/09/29 06:20:44 deberg Exp $

package java6035.tools.IR;

/**
 * The SimpleInstr class captures a simple assignment instruction or rhs
 * values without a destination. For example, the following examples can be
 * represented as SimpleInstr objects:
 *
 * "a = b+c;" or "a = foo();" or "a;" or "foo();"
 *
 * A SimpleInstr object contains a Lhs object and a Rhs object. Depends on the
 * structure of the Rhs object, sub-expressions may exist.
 */

public class SimpleInstr extends Instruction
{
    protected Lhs lhs;
    protected Rhs rhs;

    /**
     * Creates a simple instruction with just a rhs value.
     */
    public SimpleInstr(Rhs r)
    {
	this(null,r);
    }

    /**
     * Creates a simple instruction with just a lhs value and a rhs value.
     */
    public SimpleInstr(Lhs l, Rhs r)
    {
	this.lhs = l;
	this.rhs = r;

	if (this.rhs == null)
	    throw new IRException("SimpleInstr: constructor: rhs null");
    }

    /**
     * Returns the rhs value.
     */
    public Rhs getRhs()
    {
	return rhs;
    }

    /**
     * Sets the rhs value.
     */
    public void setRhs(Rhs r)
    {
	this.rhs = r;

	if (this.rhs == null)
	    throw new IRException("SimpleInstr: setRhs: rhs null");
    }

    /**
     * Returns the lhs value.
     */
    public Lhs getLhs()
    {
	return lhs;
    }

    /**
     * Sets the lhs value.
     */
    public void setLhs(Lhs l)
    {
	this.lhs = l;
    }

    /**
     * Returns the type of the instruction.
     */
    protected int tnkind()
    {
	return SIMPLE_INSTR;
    }

    /**
     * Walkable: returns the name of the node.
     */
    public String getNodeName()
    {
	if (lhs != null) 
	    return "assignment";
	else
	    return "expression";
    }


    /**
     * Walkable: returns the number of neighbors from this node.
     */
    public int getNeighborCount()
    {
	if (lhs != null) 
	    return 2;
	return 1;
    }


    /**
     * Walkable: returns a specific neighbor: 0, lhs if there is one;
     * otherwise, rhs.
     */
    public Object getNeighbor(int index)
    {
	if (lhs != null)
	{
	    if (index == 0)
		return lhs;
	    index--;
	}

	if (index == 0)
	    return rhs;
	else 
	    return null;
    }

    public String PPrint(int indent, boolean recursive)
    {
        String output = new String();
        for(int i=0;i<indent;i++) output += " ";

        output += "(simple_instruction\n";
        
        if (recursive) {
            if (lhs != null) {
                // assignment
                output += this.lhs.PPrint(indent+2, true);
                for(int i=0;i<indent+2;i++) output += " ";
                output += " :=\n";
                output += this.rhs.PPrint(indent+4, true);
            } else {
                // no assignment
                output += this.rhs.PPrint(indent+2, true);
            }
        }

        for(int i=0;i<indent;i++) output += " ";
        output += ") /* simple_instruction */\n";

        return output;
    }

}