/*

 * Copyright (c) 2015, 2016, 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 org.graalvm.compiler.nodes;

import static org.graalvm.compiler.nodeinfo.InputType.Guard;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_IGNORED;

import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_IGNORED;

import java.util.List;

import org.graalvm.compiler.core.common.spi.ConstantFieldProvider;

import org.graalvm.compiler.core.common.type.Stamp;

import org.graalvm.compiler.debug.DebugCloseable;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.spi.Canonicalizable;

import org.graalvm.compiler.graph.spi.CanonicalizerTool;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.calc.FloatingNode;

import org.graalvm.compiler.nodes.extended.GuardingNode;

import org.graalvm.compiler.nodes.extended.IntegerSwitchNode;

import org.graalvm.compiler.nodes.java.ArrayLengthNode;

import org.graalvm.compiler.nodes.java.LoadFieldNode;

import org.graalvm.compiler.nodes.java.LoadIndexedNode;

import org.graalvm.compiler.nodes.spi.StampProvider;

import org.graalvm.compiler.nodes.util.GraphUtil;

import org.graalvm.compiler.options.OptionValues;

import jdk.vm.ci.code.Architecture;

import jdk.vm.ci.meta.Assumptions;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.MetaAccessProvider;

/**

 * Graph decoder that simplifies nodes during decoding. The standard

 * {@link Canonicalizable#canonical node canonicalization} interface is used to canonicalize nodes

 * during decoding. Additionally, {@link IfNode branches} and {@link IntegerSwitchNode switches}

 * with constant conditions are simplified.

 */

public class SimplifyingGraphDecoder extends GraphDecoder {

    protected final MetaAccessProvider metaAccess;

    protected final ConstantReflectionProvider constantReflection;

    protected final ConstantFieldProvider constantFieldProvider;

    protected final StampProvider stampProvider;

    protected final boolean canonicalizeReads;

    protected final CanonicalizerTool canonicalizerTool;

    protected class PECanonicalizerTool implements CanonicalizerTool {

        private final Assumptions assumptions;

        private final OptionValues options;

        public PECanonicalizerTool(Assumptions assumptions, OptionValues options) {

            this.assumptions = assumptions;

            this.options = options;

        }

        @Override

        public OptionValues getOptions() {

            return options;

        }

        @Override

        public MetaAccessProvider getMetaAccess() {

            return metaAccess;

        }

        @Override

        public ConstantReflectionProvider getConstantReflection() {

            return constantReflection;

        }

        @Override

        public ConstantFieldProvider getConstantFieldProvider() {

            return constantFieldProvider;

        }

        @Override

        public boolean canonicalizeReads() {

            return canonicalizeReads;

        }

        @Override

        public boolean allUsagesAvailable() {

            return false;

        }

        @Override

        public Assumptions getAssumptions() {

            return assumptions;

        }

        @Override

        public Integer smallestCompareWidth() {

            // to be safe, just report null here

            // there will be more opportunities for this optimization later

            return null;

        }

    }

    @NodeInfo(cycles = CYCLES_IGNORED, size = SIZE_IGNORED, allowedUsageTypes = {Guard})

    static class CanonicalizeToNullNode extends FloatingNode implements Canonicalizable, GuardingNode {

        public static final NodeClass<CanonicalizeToNullNode> TYPE = NodeClass.create(CanonicalizeToNullNode.class);

        protected CanonicalizeToNullNode(Stamp stamp) {

            super(TYPE, stamp);

        }

        @Override

        public Node canonical(CanonicalizerTool tool) {

            return null;

        }

    }

    public SimplifyingGraphDecoder(Architecture architecture, StructuredGraph graph, MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection,

                    ConstantFieldProvider constantFieldProvider, StampProvider stampProvider,

                    boolean canonicalizeReads) {

        super(architecture, graph);

        this.metaAccess = metaAccess;

        this.constantReflection = constantReflection;

        this.constantFieldProvider = constantFieldProvider;

        this.stampProvider = stampProvider;

        this.canonicalizeReads = canonicalizeReads;

        this.canonicalizerTool = new PECanonicalizerTool(graph.getAssumptions(), graph.getOptions());

    }

    @Override

    protected void cleanupGraph(MethodScope methodScope) {

        GraphUtil.normalizeLoops(graph);

        super.cleanupGraph(methodScope);

        for (Node node : graph.getNewNodes(methodScope.methodStartMark)) {

            if (node instanceof MergeNode) {

                MergeNode mergeNode = (MergeNode) node;

                if (mergeNode.forwardEndCount() == 1) {

                    graph.reduceTrivialMerge(mergeNode);

                }

            } else if (node instanceof BeginNode || node instanceof KillingBeginNode) {

                if (!(node.predecessor() instanceof ControlSplitNode) && node.hasNoUsages()) {

                    GraphUtil.unlinkFixedNode((AbstractBeginNode) node);

                    node.safeDelete();

                }

            }

        }

        for (Node node : graph.getNewNodes(methodScope.methodStartMark)) {

            GraphUtil.tryKillUnused(node);

        }

    }

    @Override

    protected boolean allowLazyPhis() {

        /*

         * We do not need to exactly reproduce the encoded graph, so we want to avoid unnecessary

         * phi functions.

         */

        return true;

    }

    @Override

    protected void handleMergeNode(MergeNode merge) {

        /*

         * All inputs of non-loop phi nodes are known by now. We can infer the stamp for the phi, so

         * that parsing continues with more precise type information.

         */

        for (ValuePhiNode phi : merge.valuePhis()) {

            phi.inferStamp();

        }

    }

    @Override

    protected void handleFixedNode(MethodScope methodScope, LoopScope loopScope, int nodeOrderId, FixedNode node) {

        Node canonical = canonicalizeFixedNode(methodScope, node);

        if (canonical != node) {

            handleCanonicalization(loopScope, nodeOrderId, node, canonical);

        }

    }

    /**

     * Canonicalizes the provided node, which was originally a {@link FixedNode} but can already be

     * canonicalized (and therefore be a non-fixed node).

     *

     * @param methodScope The current method.

     * @param node The node to be canonicalized.

     */

    protected Node canonicalizeFixedNode(MethodScope methodScope, Node node) {

        if (node instanceof LoadFieldNode) {

            LoadFieldNode loadFieldNode = (LoadFieldNode) node;

            return loadFieldNode.canonical(canonicalizerTool);

        } else if (node instanceof FixedGuardNode) {

            FixedGuardNode guard = (FixedGuardNode) node;

            if (guard.getCondition() instanceof LogicConstantNode) {

                LogicConstantNode condition = (LogicConstantNode) guard.getCondition();

                if (condition.getValue() == guard.isNegated()) {

                    DeoptimizeNode deopt = new DeoptimizeNode(guard.getAction(), guard.getReason(), guard.getSpeculation());

                    if (guard.stateBefore() != null) {

                        deopt.setStateBefore(guard.stateBefore());

                    }

                    return deopt;

                } else {

                    return null;

                }

            }

            return node;

        } else if (node instanceof IfNode) {

            IfNode ifNode = (IfNode) node;

            if (ifNode.condition() instanceof LogicNegationNode) {

                ifNode.eliminateNegation();

            }

            if (ifNode.condition() instanceof LogicConstantNode) {

                boolean condition = ((LogicConstantNode) ifNode.condition()).getValue();

                AbstractBeginNode survivingSuccessor = ifNode.getSuccessor(condition);

                AbstractBeginNode deadSuccessor = ifNode.getSuccessor(!condition);

                graph.removeSplit(ifNode, survivingSuccessor);

                assert deadSuccessor.next() == null : "must not be parsed yet";

                deadSuccessor.safeDelete();

            }

            return node;

        } else if (node instanceof LoadIndexedNode) {

            LoadIndexedNode loadIndexedNode = (LoadIndexedNode) node;

            return loadIndexedNode.canonical(canonicalizerTool);

        } else if (node instanceof ArrayLengthNode) {

            ArrayLengthNode arrayLengthNode = (ArrayLengthNode) node;

            return arrayLengthNode.canonical(canonicalizerTool);

        } else if (node instanceof IntegerSwitchNode && ((IntegerSwitchNode) node).value().isConstant()) {

            IntegerSwitchNode switchNode = (IntegerSwitchNode) node;

            int value = switchNode.value().asJavaConstant().asInt();

            AbstractBeginNode survivingSuccessor = switchNode.successorAtKey(value);

            List<Node> allSuccessors = switchNode.successors().snapshot();

            graph.removeSplit(switchNode, survivingSuccessor);

            for (Node successor : allSuccessors) {

                if (successor != survivingSuccessor) {

                    assert ((AbstractBeginNode) successor).next() == null : "must not be parsed yet";

                    successor.safeDelete();

                }

            }

            return node;

        } else if (node instanceof Canonicalizable) {

            return ((Canonicalizable) node).canonical(canonicalizerTool);

        } else {

            return node;

        }

    }

    private static Node canonicalizeFixedNodeToNull(FixedNode node) {

        /*

         * When a node is unnecessary, we must not remove it right away because there might be nodes

         * that use it as a guard input. Therefore, we replace it with a more lightweight node

         * (which is floating and has no inputs).

         */

        return new CanonicalizeToNullNode(node.stamp);

    }

    @SuppressWarnings("try")

    private void handleCanonicalization(LoopScope loopScope, int nodeOrderId, FixedNode node, Node c) {

        assert c != node : "unnecessary call";

        try (DebugCloseable position = graph.withNodeSourcePosition(node)) {

            Node canonical = c == null ? canonicalizeFixedNodeToNull(node) : c;

            if (!canonical.isAlive()) {

                assert !canonical.isDeleted();

                canonical = graph.addOrUniqueWithInputs(canonical);

                if (canonical instanceof FixedWithNextNode) {

                    graph.addBeforeFixed(node, (FixedWithNextNode) canonical);

                } else if (canonical instanceof ControlSinkNode) {

                    FixedWithNextNode predecessor = (FixedWithNextNode) node.predecessor();

                    predecessor.setNext((ControlSinkNode) canonical);

                    List<Node> successorSnapshot = node.successors().snapshot();

                    node.safeDelete();

                    for (Node successor : successorSnapshot) {

                        successor.safeDelete();

                    }

                } else {

                    assert !(canonical instanceof FixedNode);

                }

            }

            if (!node.isDeleted()) {

                GraphUtil.unlinkFixedNode((FixedWithNextNode) node);

                node.replaceAtUsagesAndDelete(canonical);

            }

            assert lookupNode(loopScope, nodeOrderId) == node;

            registerNode(loopScope, nodeOrderId, canonical, true, false);

        }

    }

    @Override

    @SuppressWarnings("try")

    protected Node handleFloatingNodeBeforeAdd(MethodScope methodScope, LoopScope loopScope, Node node) {

        if (node instanceof ValueNode) {

            ((ValueNode) node).inferStamp();

        }

        if (node instanceof Canonicalizable) {

            try (DebugCloseable context = graph.withNodeSourcePosition(node)) {

                Node canonical = ((Canonicalizable) node).canonical(canonicalizerTool);

                if (canonical == null) {

                    /*

                     * This is a possible return value of canonicalization. However, we might need

                     * to add additional usages later on for which we need a node. Therefore, we

                     * just do nothing and leave the node in place.

                     */

                } else if (canonical != node) {

                    if (!canonical.isAlive()) {

                        assert !canonical.isDeleted();

                        canonical = graph.addOrUniqueWithInputs(canonical);

                    }

                    assert node.hasNoUsages();

                    return canonical;

                }

            }

        }

        return node;

    }

    @Override

    protected Node addFloatingNode(MethodScope methodScope, Node node) {

        /*

         * In contrast to the base class implementation, we do not need to exactly reproduce the

         * encoded graph. Since we do canonicalization, we also want nodes to be unique.

         */

        return graph.addOrUnique(node);

    }

}