treeif.java

用Java实现的编译器。把源代码编译成SPARC汇编程序

// $Id: TreeIf.java,v 1.4 1999/09/27 20:01:29 deberg Exp $

package java6035.tools.IR;

/**
 * TreeIf represents an if construct. There are three components to this, a
 * conditional, a true block, and a false block.
 */

public class TreeIf extends TreeNode 
{
    protected TreeBlock true_block;
    protected TreeBlock false_block;
    protected TreeBlock conditions;


    /**
     * Constructs a TreeIf object with the arguments given. If either the
     * true or false block is null, it is initialized to be empty. 
     */ 
    public TreeIf(Expression cond, TreeBlock tb, TreeBlock fb)
    {
	if (cond == null)
	    throw new IRException("TreeIf: constructor: cond null");

	TreeBlock conditions = new TreeBlock("if_cond");
	conditions.appendNode(new SimpleInstr(cond));

	init(conditions, tb, fb);
    }

    /**
     * Constructs a TreeIf object with the arguments given.  If either the
     * true or false block is null, it is initialized to be empty. 
     */ 
    public TreeIf(TreeBlock cond, TreeBlock tb, TreeBlock fb)
    {
	init(cond, tb, fb);
    }


    private void init(TreeBlock cond, TreeBlock tb, TreeBlock fb)
    {
	this.conditions = cond;
	this.true_block = tb;
	this.false_block = fb;

	if (this.conditions == null)
	    throw new IRException("TreeIf: constructor: cond null");
        this.conditions.setParent(this);
	
	if (this.true_block == null)
	    this.true_block = new TreeBlock("if_true_blk");
        this.true_block.setParent(this);

	if (this.false_block == null)
	    this.false_block = new TreeBlock("if_false_blk");
        this.false_block.setParent(this);
    }

    protected int tnkind()
    {
	return TREE_IF;
    }

    /**
     * Returns the true block of this TreeIf object.
     */
    public TreeBlock getTrueBlock() {
        return this.true_block;
    }

    /**
     * Returns the false block of this TreeIf object.
     */
    public TreeBlock getFalseBlock() {
        return this.false_block;
    }

    /**
     * Return the conditional expression for this block. If the block already
     * flattened, behavior is not specified. If conditional block passed in is
     * null, behavior not specified.
     */
    public Rhs getCondition()
    {
	/* The conditional expression is assumed to be the expression on the
	 * rhs of the first node of the block. */

	if (conditions.size() > 0)
	{
	    TreeNode tn = conditions.getNodeAt(0);
	    if (tn.isSimpleInstr())
	    {
		return ((SimpleInstr)tn).getRhs();
	    }
	}
	return null;
    }


    /**
     * Returns the conditions of this TreeIf object.  You may find having
     * a TreeBlock for your conditional when you have to flatten it.
     */
    public TreeBlock getConditions() {
        return this.conditions;
    }


    /**
     * Walkable: returns the name of the node.
     */
    public String getNodeName()
    {
        return "IF";
    }

    /**
     * Walkable: returns the number of neighbors.
     */
    public int getNeighborCount()
    {
        return 3;
    }

    /**
     * Walkable: returns the requested neighbor: 0, conditions; 1, true block;
     * 2, false block.
     */
    public Object getNeighbor(int i)
    {
	if (i == 0)
	    return conditions;
	else if (i == 1)
	    return true_block;
	else if (i == 2)
	    return false_block;
	else 
	    return null;
    }


    public String PPrint(int indent, boolean recursive)
    {
        String output = new String();
        for(int i=0;i<indent;i++) output += " ";
        output += "(IF /* conditions, true_branch, false_branch */\n";
        indent += 2;

        output += conditions.PPrint(indent,true);
        if (recursive) {
            output += true_block.PPrint(indent,recursive);
        } else {
            for(int i=0;i<indent;i++) output += " ";
            output += true_block.getNodeName() + "\n";
        }
        if (recursive) {
            output += false_block.PPrint(indent,recursive);
        } else {
            for(int i=0;i<indent;i++) output += " ";
            output += false_block.getNodeName() + "\n";
        }

        indent -= 2;
        for(int i=0;i<indent;i++) output += " ";
        output += ") /* IF */ \n";
        return output;
    }

}