labeldescriptor.java

来自「用Java实现的编译器。把源代码编译成SPARC汇编程序」· Java 代码 · 共 72 行

// $Id: LabelDescriptor.java,v 1.2 1999/09/27 20:01:28 deberg Exp $

package java6035.tools.IR;

/**
 * LabelDescriptor
 *
 * represents a label in the low level IR tree, such as procedure and
 * block entry point. Calling the constructor will generate a unique 
 * label with the given suffix. LabelDescriptor has a reference count
 * that can help to determine the usage of a label.
 */

public class LabelDescriptor extends Descriptor 
{
    private static int counter = 0;
    private LabelInstr lab;
    private int ref_count = 0;


    /**
     * Creates a low IR label with "_Lxxx" as prefix, where xxx is a
     * unique number throughout the program.
     *
     * @param suffix   Suffix of the label.
     */
    public LabelDescriptor(String suffix, LabelInstr lab)
    {
        super("_L"+getCounter()+suffix);
	this.lab = lab;
	this.ref_count = 0;
    }


    public void ref()
    {
	ref_count++;
    }


    public void unref()
    {
	ref_count--;
    }


    public int getRef()
    {
	return ref_count;
    }


    /**
     * Returns the instruction that defines this label.
     */
    public LabelInstr getLabelInstr()
    {
	return this.lab;
    }


    /**
     * return a counter, increment the counter to get the next one.
     */
    public static int getCounter()
    {
        counter++;
        return counter-1;
    }
}