treewhile.java

用Java实现的编译器。把源代码编译成SPARC汇编程序

// $Id: TreeWhile.java,v 1.5 2000/10/21 22:44:33 mdeeds Exp $

package java6035.tools.IR;

/**
 * TreeWhile represents a loop. It has two components: condition for
 * the loop and a body. 
 */

public class TreeWhile extends TreeNode 
{
    protected TreeBlock body;
    protected TreeBlock conditions;

    /**
     * Constructs a TreeWhile object with the arguments given.  If the
     * @param body is null, an empty block is created. <BR> Requires
     * @param cond is not null.
     **/ 
    public TreeWhile(Expression cond, TreeBlock body)
    {
	if (cond == null)
	    throw new IRException("TreeWhile: constructor: cond null");
	TreeBlock conditions = new TreeBlock("while_cond");
	conditions.appendNode(new SimpleInstr(cond));
	init(conditions, body);
    }

    /**
     * Constructs a TreeWhile object with the arguments given. The
     * last entry in @param cond TreeBlock should be an expression
     * with a boolean value.  The Treeblock may contain a single
     * expression, or the flattened instructions for a larger boolean
     * expression.  If @param body is null, an empty block is created.
     **/
    public TreeWhile(TreeBlock cond, TreeBlock body)
    {
	init(cond, body);
    }

    private void init(TreeBlock cond, TreeBlock body)
    {
	this.conditions = cond;
	this.body = body;

	if (this.conditions == null)
	    throw new IRException("TreeWhile: constructor: cond null");
        this.conditions.setParent(this);
	
	if (this.body == null)
	    this.body = new TreeBlock("while_body");
        this.body.setParent(this);
    }

    
    /**
     * Returns the kind of this expression.  (i.e. TREE_WHILE) 
     **/
    protected int tnkind()
    {
	return TREE_WHILE;
    }

    
    /**
     * Returns the body of this TreeWhile object.
     **/
    public TreeBlock getBody() {
        return this.body;
    }


    /**
     * 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 condition block of this TreeWhile object.
     **/
    public TreeBlock getConditions() {
        return this.conditions;
    }


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


    /**
     * Walkable: returns the number of neighbors.
     */
    public int getNeighborCount()
    {
        return 2;
    }


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

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

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

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