package flow_graph;

import util.List;
import temp.Temp;
import graph.Node;

/**
 * A control flow graph is a directed graph in which each edge
 * indicates a possible flow of control.  Also, each node in
 * the graph defines a set of temporaries; each node uses a set of
 * temporaries; and each node is, or is not, a <strong>move</strong>
 * instruction.
 *
 * @see AssemFlowGraph
 */

public abstract class FlowGraph extends graph.Graph
{
    /**
     * The set of temporaries defined by this instruction or block 
     */
    public abstract List<Temp> def(Node node);

    /**
     * The set of temporaries used by this instruction or block 
     */
    public abstract List<Temp> use(Node node);

    /**
     * True if this node represents a <strong>move</strong> instruction,
     * i.e. one that can be deleted if def=use. 
     */
    public abstract boolean isMove(Node node);

    /**
     * Print a human-readable dump for debugging.
     */
    public void show(java.io.PrintStream out)
    {
        for (List<Node>p=nodes(); p!=null; p=p.tail)
        {
            Node n = p.head;
            out.print(n.toString());
            out.print(": ");
            for(List<Temp> q=def(n); q!=null; q=q.tail)
            {
                out.print(q.head.toString());
                out.print(" ");
            }
            out.print(isMove(n) ? "<= " : "<- ");
            for(List<Temp> q=use(n); q!=null; q=q.tail)
            {
                out.print(q.head.toString());
                out.print(" ");
            }
            out.print("; goto ");
            for(List<Node> q=n.succ(); q!=null; q=q.tail)
            {
                out.print(q.head.toString());
                out.print(" ");
            }
            out.println();
        }
    }
}