/*
 * This file is part of JOP, the Java Optimized Processor
 * see <http://www.jopdesign.com/>
 *
 * Copyright (C) 2010, Benedikt Huber (benedikt.huber@gmail.com)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.jopdesign.wcet.analysis.cache;

import com.jopdesign.common.MethodInfo;
import com.jopdesign.common.code.CallGraph.ContextEdge;
import com.jopdesign.common.code.ControlFlowGraph;
import com.jopdesign.common.code.ControlFlowGraph.CFGNode;
import com.jopdesign.common.code.ExecutionContext;
import com.jopdesign.wcet.WCETTool;
import org.jgrapht.traverse.TopologicalOrderIterator;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.logging.Logger;

/**
 * This is a primitive, simple analysis to find blocks which are only executed once
 * in a scope.
 * <p>
 * For this purpose, the nodes of each scope are split into the root method and
 * referenced methods. Those referenced methods which might be called more than once
 * are marked with {@code *}, the others with {@code 1}.
 * </p><p>
 * If we need to know whether a node is executed at most once in a scope, we check
 * whether the containing method is marked with {@code root}, {@code *} or {@code 1}.
 * In the first case, we check whether the containing basic block is part of a loop.
 * </p>
 * TODO: [scope-analysis] More efficient implementation of ExecuteOnceAnalysis. Currently
 * we have 4 nested loops.
 *
 * @author Benedikt Huber <benedikt.huber@gmail.com>
 */
public class ExecuteOnceAnalysis {
    private WCETTool project;
    private Map<ExecutionContext, Set<MethodInfo>> inLoopSet;

    public ExecuteOnceAnalysis(WCETTool p) {
        this.project = p;
        analyze();
    }

    private void analyze() {
        inLoopSet = new HashMap<ExecutionContext, Set<MethodInfo>>();
        /* Top Down the Scope Graph */
        TopologicalOrderIterator<ExecutionContext, ContextEdge> iter =
                project.getCallGraph().topDownIterator();

        while (iter.hasNext()) {
            ExecutionContext scope = iter.next();
            scope = new ExecutionContext(scope.getMethodInfo()); /* Remove call string */
            ControlFlowGraph cfg = project.getFlowGraph(scope.getMethodInfo());
            Set<MethodInfo> inLoop = new HashSet<MethodInfo>();
            for (CFGNode node : cfg.vertexSet()) {
                if (!(node instanceof ControlFlowGraph.InvokeNode)) continue;
                ControlFlowGraph.InvokeNode iNode = (ControlFlowGraph.InvokeNode) node;
                if (!cfg.getLoopColoring().getLoopColor(node).isEmpty()) {
                    for (MethodInfo impl : iNode.getImplementingMethods()) {
                        inLoop.add(impl);
                        inLoop.addAll(project.getCallGraph().getReachableImplementationsSet(impl));
                    }
                }
            }
            inLoopSet.put(scope, inLoop);
        }
    }

    public boolean isExecutedOnce(ExecutionContext scope, CFGNode node) {
        ControlFlowGraph cfg = node.getControlFlowGraph();
        scope = new ExecutionContext(scope.getMethodInfo()); /* Remove call string */
        Set<MethodInfo> inLoopMethods = inLoopSet.get(scope);
        if (inLoopMethods == null) {
            Logger.getLogger("Object Cache Analysis").warning("No loop information for " + scope.getMethodInfo().getFQMethodName());
            return false;
        }
        if (!inLoopMethods.contains(cfg.getMethodInfo())) {
            return cfg.getLoopColoring().getLoopColor(node).size() == 0;
        } else {
            return false;
        }
    }

}