/*
 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.graal.phases.common;

import java.util.*;
import java.util.concurrent.*;

import com.oracle.graal.api.code.*;
import com.oracle.graal.api.meta.*;
import com.oracle.graal.debug.*;
import com.oracle.graal.graph.*;
import com.oracle.graal.graph.Graph.InputChangedListener;
import com.oracle.graal.nodes.*;
import com.oracle.graal.nodes.calc.*;
import com.oracle.graal.nodes.spi.*;
import com.oracle.graal.nodes.type.*;
import com.oracle.graal.nodes.util.*;
import com.oracle.graal.phases.*;

public class CanonicalizerPhase extends Phase {

    private static final int MAX_ITERATION_PER_NODE = 10;
    private static final DebugMetric METRIC_CANONICALIZED_NODES = Debug.metric("CanonicalizedNodes");
    private static final DebugMetric METRIC_CANONICALIZATION_CONSIDERED_NODES = Debug.metric("CanonicalizationConsideredNodes");
    private static final DebugMetric METRIC_INFER_STAMP_CALLED = Debug.metric("InferStampCalled");
    private static final DebugMetric METRIC_STAMP_CHANGED = Debug.metric("StampChanged");
    private static final DebugMetric METRIC_SIMPLIFICATION_CONSIDERED_NODES = Debug.metric("SimplificationConsideredNodes");
    public static final DebugMetric METRIC_GLOBAL_VALUE_NUMBERING_HITS = Debug.metric("GlobalValueNumberingHits");

    private final int newNodesMark;
    private final TargetDescription target;
    private final Assumptions assumptions;
    private final MetaAccessProvider runtime;
    private final CustomCanonicalizer customCanonicalizer;
    private final Iterable<Node> initWorkingSet;

    private NodeWorkList workList;
    private Tool tool;
    private List<Node> snapshotTemp;

    public interface CustomCanonicalizer {

        ValueNode canonicalize(Node node);
    }

    public CanonicalizerPhase(TargetDescription target, MetaAccessProvider runtime, Assumptions assumptions) {
        this(target, runtime, assumptions, null, 0, null);
    }

    /**
     * @param target
     * @param runtime
     * @param assumptions
     * @param workingSet the initial working set of nodes on which the canonicalizer works, should
     *            be an auto-grow node bitmap
     * @param customCanonicalizer
     */
    public CanonicalizerPhase(TargetDescription target, MetaAccessProvider runtime, Assumptions assumptions, Iterable<Node> workingSet, CustomCanonicalizer customCanonicalizer) {
        this(target, runtime, assumptions, workingSet, 0, customCanonicalizer);
    }

    /**
     * @param newNodesMark only the {@linkplain Graph#getNewNodes(int) new nodes} specified by this
     *            mark are processed otherwise all nodes in the graph are processed
     */
    public CanonicalizerPhase(TargetDescription target, MetaAccessProvider runtime, Assumptions assumptions, int newNodesMark, CustomCanonicalizer customCanonicalizer) {
        this(target, runtime, assumptions, null, newNodesMark, customCanonicalizer);
    }

    public CanonicalizerPhase(TargetDescription target, MetaAccessProvider runtime, Assumptions assumptions, Iterable<Node> workingSet, int newNodesMark, CustomCanonicalizer customCanonicalizer) {
        this.newNodesMark = newNodesMark;
        this.target = target;
        this.assumptions = assumptions;
        this.runtime = runtime;
        this.customCanonicalizer = customCanonicalizer;
        this.initWorkingSet = workingSet;
        this.snapshotTemp = new ArrayList<>();
    }

    @Override
    protected void run(StructuredGraph graph) {
        if (initWorkingSet == null) {
            workList = graph.createNodeWorkList(newNodesMark == 0, MAX_ITERATION_PER_NODE);
        } else {
            workList = graph.createNodeWorkList(false, MAX_ITERATION_PER_NODE);
            workList.addAll(initWorkingSet);
        }
        if (newNodesMark > 0) {
            workList.addAll(graph.getNewNodes(newNodesMark));
        }
        tool = new Tool(workList, runtime, target, assumptions);
        processWorkSet(graph);
    }

    private void processWorkSet(StructuredGraph graph) {
        graph.trackInputChange(new InputChangedListener() {

            @Override
            public void inputChanged(Node node) {
                workList.addAgain(node);
            }
        });

        for (Node n : workList) {
            processNode(n, graph);
        }

        graph.stopTrackingInputChange();
    }

    private void processNode(Node node, StructuredGraph graph) {
        if (node.isAlive()) {
            METRIC_PROCESSED_NODES.increment();

            if (tryGlobalValueNumbering(node, graph)) {
                return;
            }
            int mark = graph.getMark();
            if (!tryKillUnused(node)) {
                node.inputs().filter(GraphUtil.isFloatingNode()).snapshotTo(snapshotTemp);
                if (!tryCanonicalize(node, graph)) {
                    tryInferStamp(node, graph);
                } else {
                    for (Node in : snapshotTemp) {
                        if (in.isAlive() && in.usages().isEmpty()) {
                            GraphUtil.killWithUnusedFloatingInputs(in);
                        }
                    }
                }
                snapshotTemp.clear();
            }

            for (Node newNode : graph.getNewNodes(mark)) {
                workList.add(newNode);
            }
        }
    }

    private static boolean tryKillUnused(Node node) {
        if (node.isAlive() && GraphUtil.isFloatingNode().apply(node) && node.usages().isEmpty()) {
            GraphUtil.killWithUnusedFloatingInputs(node);
            return true;
        }
        return false;
    }

    public static boolean tryGlobalValueNumbering(Node node, StructuredGraph graph) {
        if (node.getNodeClass().valueNumberable()) {
            Node newNode = graph.findDuplicate(node);
            if (newNode != null) {
                assert !(node instanceof FixedNode || newNode instanceof FixedNode);
                node.replaceAtUsages(newNode);
                node.safeDelete();
                METRIC_GLOBAL_VALUE_NUMBERING_HITS.increment();
                Debug.log("GVN applied and new node is %1s", newNode);
                return true;
            }
        }
        return false;
    }

    public boolean tryCanonicalize(final Node node, final StructuredGraph graph) {
        boolean result = baseTryCanonicalize(node, graph);
        if (!result && customCanonicalizer != null) {
            ValueNode canonical = customCanonicalizer.canonicalize(node);
            if (canonical == node && customCanonicalizer != null) {
                canonical = customCanonicalizer.canonicalize(node);
            }
            result = performReplacement(node, graph, canonical);
        }
        return result;
    }

    public boolean baseTryCanonicalize(final Node node, final StructuredGraph graph) {
        if (node instanceof Canonicalizable) {
            assert !(node instanceof Simplifiable);
            METRIC_CANONICALIZATION_CONSIDERED_NODES.increment();
            return Debug.scope("CanonicalizeNode", node, new Callable<Boolean>() {

                public Boolean call() {
                    ValueNode canonical = ((Canonicalizable) node).canonical(tool);
// @formatter:off
//     cases:                                           original node:
//                                         |Floating|Fixed-unconnected|Fixed-connected|
//                                         --------------------------------------------
//                                     null|   1    |        X        |       3       |
//                                         --------------------------------------------
//                                 Floating|   2    |        X        |       4       |
//       canonical node:                   --------------------------------------------
//                        Fixed-unconnected|   X    |        X        |       5       |
//                                         --------------------------------------------
//                          Fixed-connected|   2    |        X        |       6       |
//                                         --------------------------------------------
//       X: must not happen (checked with assertions)
// @formatter:on

                    return performReplacement(node, graph, canonical);
                }
            });
        } else if (node instanceof Simplifiable) {
            Debug.log("Canonicalizer: simplifying %s", node);
            METRIC_SIMPLIFICATION_CONSIDERED_NODES.increment();
            Debug.scope("SimplifyNode", node, new Runnable() {

                public void run() {
                    ((Simplifiable) node).simplify(tool);
                }
            });
        }
        return node.isDeleted();
    }

    private boolean performReplacement(final Node node, final StructuredGraph graph, ValueNode canonical) {
        if (canonical == node) {
            Debug.log("Canonicalizer: work on %s", node);
            return false;
        } else {
            Debug.log("Canonicalizer: replacing %s with %s", node, canonical);
            METRIC_CANONICALIZED_NODES.increment();
            if (node instanceof FloatingNode) {
                if (canonical == null) {
                    // case 1
                    graph.removeFloating((FloatingNode) node);
                } else {
                    // case 2
                    assert !(canonical instanceof FixedNode) || (canonical.predecessor() != null || canonical instanceof StartNode || canonical instanceof MergeNode) : node + " -> " + canonical +
                                    " : replacement should be floating or fixed and connected";
                    graph.replaceFloating((FloatingNode) node, canonical);
                }
            } else {
                assert node instanceof FixedWithNextNode && node.predecessor() != null : node + " -> " + canonical + " : node should be fixed & connected (" + node.predecessor() + ")";
                FixedWithNextNode fixedWithNext = (FixedWithNextNode) node;

                // When removing a fixed node, new canonicalization opportunities for its successor
                // may arise
                assert fixedWithNext.next() != null;
                tool.addToWorkList(fixedWithNext.next());

                if (canonical == null) {
                    // case 3
                    graph.removeFixed(fixedWithNext);
                } else if (canonical instanceof FloatingNode) {
                    // case 4
                    graph.replaceFixedWithFloating(fixedWithNext, (FloatingNode) canonical);
                } else {
                    assert canonical instanceof FixedNode;
                    if (canonical.predecessor() == null) {
                        assert !canonical.cfgSuccessors().iterator().hasNext() : "replacement " + canonical + " shouldn't have successors";
                        // case 5
                        graph.replaceFixedWithFixed(fixedWithNext, (FixedWithNextNode) canonical);
                    } else {
                        assert canonical.cfgSuccessors().iterator().hasNext() : "replacement " + canonical + " should have successors";
                        // case 6
                        node.replaceAtUsages(canonical);
                        graph.removeFixed(fixedWithNext);
                    }
                }
            }
            return true;
        }
    }

    /**
     * Calls {@link ValueNode#inferStamp()} on the node and, if it returns true (which means that
     * the stamp has changed), re-queues the node's usages . If the stamp has changed then this
     * method also checks if the stamp now describes a constant integer value, in which case the
     * node is replaced with a constant.
     */
    private void tryInferStamp(Node node, StructuredGraph graph) {
        if (node.isAlive() && node instanceof ValueNode) {
            ValueNode valueNode = (ValueNode) node;
            METRIC_INFER_STAMP_CALLED.increment();
            if (valueNode.inferStamp()) {
                METRIC_STAMP_CHANGED.increment();
                if (valueNode.stamp() instanceof IntegerStamp && valueNode.integerStamp().lowerBound() == valueNode.integerStamp().upperBound()) {
                    ValueNode replacement = ConstantNode.forIntegerKind(valueNode.kind(), valueNode.integerStamp().lowerBound(), graph);
                    Debug.log("Canonicalizer: replacing %s with %s (inferStamp)", valueNode, replacement);
                    valueNode.replaceAtUsages(replacement);
                } else {
                    for (Node usage : valueNode.usages()) {
                        workList.addAgain(usage);
                    }
                }
            }
        }
    }

    private static final class Tool implements SimplifierTool {

        private final NodeWorkList nodeWorkSet;
        private final MetaAccessProvider runtime;
        private final TargetDescription target;
        private final Assumptions assumptions;

        public Tool(NodeWorkList nodeWorkSet, MetaAccessProvider runtime, TargetDescription target, Assumptions assumptions) {
            this.nodeWorkSet = nodeWorkSet;
            this.runtime = runtime;
            this.target = target;
            this.assumptions = assumptions;
        }

        @Override
        public void deleteBranch(FixedNode branch) {
            branch.predecessor().replaceFirstSuccessor(branch, null);
            GraphUtil.killCFG(branch);
        }

        /**
         * @return the current target or {@code null} if no target is available in the current
         *         context.
         */
        @Override
        public TargetDescription target() {
            return target;
        }

        /**
         * @return an object that can be used for recording assumptions or {@code null} if
         *         assumptions are not allowed in the current context.
         */
        @Override
        public Assumptions assumptions() {
            return assumptions;
        }

        @Override
        public MetaAccessProvider runtime() {
            return runtime;
        }

        @Override
        public void addToWorkList(Node node) {
            nodeWorkSet.addAgain(node);
        }

        @Override
        public void removeIfUnused(Node node) {
            tryKillUnused(node);
        }
    }
}