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 * Copyright (c) 2011, 2019, 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

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package org.graalvm.compiler.nodes.util;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collection;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.Objects;

import java.util.function.BiFunction;

import jdk.internal.vm.compiler.collections.EconomicMap;

import jdk.internal.vm.compiler.collections.EconomicSet;

import jdk.internal.vm.compiler.collections.Equivalence;

import jdk.internal.vm.compiler.collections.MapCursor;

import org.graalvm.compiler.bytecode.Bytecode;

import org.graalvm.compiler.code.SourceStackTraceBailoutException;

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

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

import org.graalvm.compiler.debug.DebugContext;

import org.graalvm.compiler.graph.Graph;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeBitMap;

import org.graalvm.compiler.graph.NodeSourcePosition;

import org.graalvm.compiler.graph.NodeStack;

import org.graalvm.compiler.graph.Position;

import org.graalvm.compiler.graph.iterators.NodeIterable;

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

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.AbstractEndNode;

import org.graalvm.compiler.nodes.AbstractMergeNode;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.ControlSplitNode;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.FixedWithNextNode;

import org.graalvm.compiler.nodes.FrameState;

import org.graalvm.compiler.nodes.GuardNode;

import org.graalvm.compiler.nodes.LoopBeginNode;

import org.graalvm.compiler.nodes.LoopEndNode;

import org.graalvm.compiler.nodes.LoopExitNode;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.PhiNode;

import org.graalvm.compiler.nodes.PiNode;

import org.graalvm.compiler.nodes.ProxyNode;

import org.graalvm.compiler.nodes.StateSplit;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.ValuePhiNode;

import org.graalvm.compiler.nodes.ValueProxyNode;

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

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

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

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

import org.graalvm.compiler.nodes.spi.ArrayLengthProvider.FindLengthMode;

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

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

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

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

import org.graalvm.compiler.nodes.type.StampTool;

import org.graalvm.compiler.nodes.virtual.VirtualArrayNode;

import org.graalvm.compiler.nodes.virtual.VirtualObjectNode;

import org.graalvm.compiler.options.Option;

import org.graalvm.compiler.options.OptionKey;

import org.graalvm.compiler.options.OptionType;

import org.graalvm.compiler.options.OptionValues;

import jdk.vm.ci.code.BailoutException;

import jdk.vm.ci.code.BytecodePosition;

import jdk.vm.ci.meta.Assumptions;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaMethod;

import jdk.vm.ci.meta.ResolvedJavaType;

public class GraphUtil {

    public static class Options {

        @Option(help = "Verify that there are no new unused nodes when performing killCFG", type = OptionType.Debug)//

        public static final OptionKey<Boolean> VerifyKillCFGUnusedNodes = new OptionKey<>(false);

    }

    private static void killCFGInner(FixedNode node) {

        EconomicSet<Node> markedNodes = EconomicSet.create();

        EconomicMap<AbstractMergeNode, List<AbstractEndNode>> unmarkedMerges = EconomicMap.create();

        // Detach this node from CFG

        node.replaceAtPredecessor(null);

        markFixedNodes(node, markedNodes, unmarkedMerges);

        fixSurvivingAffectedMerges(markedNodes, unmarkedMerges);

        DebugContext debug = node.getDebug();

        debug.dump(DebugContext.DETAILED_LEVEL, node.graph(), "After fixing merges (killCFG %s)", node);

        // Mark non-fixed nodes

        markUsages(markedNodes);

        // Detach marked nodes from non-marked nodes

        for (Node marked : markedNodes) {

            for (Node input : marked.inputs()) {

                if (!markedNodes.contains(input)) {

                    marked.replaceFirstInput(input, null);

                    tryKillUnused(input);

                }

            }

        }

        debug.dump(DebugContext.VERY_DETAILED_LEVEL, node.graph(), "After disconnecting non-marked inputs (killCFG %s)", node);

        // Kill marked nodes

        for (Node marked : markedNodes) {

            if (marked.isAlive()) {

                marked.markDeleted();

            }

        }

    }

    private static void markFixedNodes(FixedNode node, EconomicSet<Node> markedNodes, EconomicMap<AbstractMergeNode, List<AbstractEndNode>> unmarkedMerges) {

        NodeStack workStack = new NodeStack();

        workStack.push(node);

        while (!workStack.isEmpty()) {

            Node fixedNode = workStack.pop();

            markedNodes.add(fixedNode);

            if (fixedNode instanceof AbstractMergeNode) {

                unmarkedMerges.removeKey((AbstractMergeNode) fixedNode);

            }

            while (fixedNode instanceof FixedWithNextNode) {

                fixedNode = ((FixedWithNextNode) fixedNode).next();

                if (fixedNode != null) {

                    markedNodes.add(fixedNode);

                }

            }

            if (fixedNode instanceof ControlSplitNode) {

                for (Node successor : fixedNode.successors()) {

                    workStack.push(successor);

                }

            } else if (fixedNode instanceof AbstractEndNode) {

                AbstractEndNode end = (AbstractEndNode) fixedNode;

                AbstractMergeNode merge = end.merge();

                if (merge != null) {

                    assert !markedNodes.contains(merge) || (merge instanceof LoopBeginNode && end instanceof LoopEndNode) : merge;

                    if (merge instanceof LoopBeginNode) {

                        if (end == ((LoopBeginNode) merge).forwardEnd()) {

                            workStack.push(merge);

                            continue;

                        }

                        if (markedNodes.contains(merge)) {

                            continue;

                        }

                    }

                    List<AbstractEndNode> endsSeen = unmarkedMerges.get(merge);

                    if (endsSeen == null) {

                        endsSeen = new ArrayList<>(merge.forwardEndCount());

                        unmarkedMerges.put(merge, endsSeen);

                    }

                    endsSeen.add(end);

                    if (!(end instanceof LoopEndNode) && endsSeen.size() == merge.forwardEndCount()) {

                        assert merge.forwardEnds().filter(n -> !markedNodes.contains(n)).isEmpty();

                        // all this merge's forward ends are marked: it needs to be killed

                        workStack.push(merge);

                    }

                }

            }

        }

    }

    private static void fixSurvivingAffectedMerges(EconomicSet<Node> markedNodes, EconomicMap<AbstractMergeNode, List<AbstractEndNode>> unmarkedMerges) {

        MapCursor<AbstractMergeNode, List<AbstractEndNode>> cursor = unmarkedMerges.getEntries();

        while (cursor.advance()) {

            AbstractMergeNode merge = cursor.getKey();

            for (AbstractEndNode end : cursor.getValue()) {

                merge.removeEnd(end);

            }

            if (merge.phiPredecessorCount() == 1) {

                if (merge instanceof LoopBeginNode) {

                    LoopBeginNode loopBegin = (LoopBeginNode) merge;

                    assert merge.forwardEndCount() == 1;

                    for (LoopExitNode loopExit : loopBegin.loopExits().snapshot()) {

                        if (markedNodes.contains(loopExit)) {

                            /*

                             * disconnect from loop begin so that reduceDegenerateLoopBegin doesn't

                             * transform it into a new beginNode

                             */

                            loopExit.replaceFirstInput(loopBegin, null);

                        }

                    }

                    merge.graph().reduceDegenerateLoopBegin(loopBegin);

                } else {

                    merge.graph().reduceTrivialMerge(merge);

                }

            } else {

                assert merge.phiPredecessorCount() > 1 : merge;

            }

        }

    }

    private static void markUsages(EconomicSet<Node> markedNodes) {

        NodeStack workStack = new NodeStack(markedNodes.size() + 4);

        for (Node marked : markedNodes) {

            workStack.push(marked);

        }

        while (!workStack.isEmpty()) {

            Node marked = workStack.pop();

            for (Node usage : marked.usages()) {

                if (!markedNodes.contains(usage)) {

                    workStack.push(usage);

                    markedNodes.add(usage);

                }

            }

        }

    }

    @SuppressWarnings("try")

    public static void killCFG(FixedNode node) {

        DebugContext debug = node.getDebug();

        try (DebugContext.Scope scope = debug.scope("KillCFG", node)) {

            EconomicSet<Node> unusedNodes = null;

            EconomicSet<Node> unsafeNodes = null;

            Graph.NodeEventScope nodeEventScope = null;

            OptionValues options = node.getOptions();

            boolean verifyGraalGraphEdges = Graph.Options.VerifyGraalGraphEdges.getValue(options);

            boolean verifyKillCFGUnusedNodes = GraphUtil.Options.VerifyKillCFGUnusedNodes.getValue(options);

            if (verifyGraalGraphEdges) {

                unsafeNodes = collectUnsafeNodes(node.graph());

            }

            if (verifyKillCFGUnusedNodes) {

                EconomicSet<Node> collectedUnusedNodes = unusedNodes = EconomicSet.create(Equivalence.IDENTITY);

                nodeEventScope = node.graph().trackNodeEvents(new Graph.NodeEventListener() {

                    @Override

                    public void changed(Graph.NodeEvent e, Node n) {

                        if (e == Graph.NodeEvent.ZERO_USAGES && isFloatingNode(n) && !(n instanceof GuardNode)) {

                            collectedUnusedNodes.add(n);

                        }

                    }

                });

            }

            debug.dump(DebugContext.VERY_DETAILED_LEVEL, node.graph(), "Before killCFG %s", node);

            killCFGInner(node);

            debug.dump(DebugContext.VERY_DETAILED_LEVEL, node.graph(), "After killCFG %s", node);

            if (verifyGraalGraphEdges) {

                EconomicSet<Node> newUnsafeNodes = collectUnsafeNodes(node.graph());

                newUnsafeNodes.removeAll(unsafeNodes);

                assert newUnsafeNodes.isEmpty() : "New unsafe nodes: " + newUnsafeNodes;

            }

            if (verifyKillCFGUnusedNodes) {

                nodeEventScope.close();

                Iterator<Node> iterator = unusedNodes.iterator();

                while (iterator.hasNext()) {

                    Node curNode = iterator.next();

                    if (curNode.isDeleted()) {

                        iterator.remove();

                    }

                }

                assert unusedNodes.isEmpty() : "New unused nodes: " + unusedNodes;

            }

        } catch (Throwable t) {

            throw debug.handle(t);

        }

    }

    /**

     * Collects all node in the graph which have non-optional inputs that are null.

     */

    private static EconomicSet<Node> collectUnsafeNodes(Graph graph) {

        EconomicSet<Node> unsafeNodes = EconomicSet.create(Equivalence.IDENTITY);

        for (Node n : graph.getNodes()) {

            for (Position pos : n.inputPositions()) {

                Node input = pos.get(n);

                if (input == null) {

                    if (!pos.isInputOptional()) {

                        unsafeNodes.add(n);

                    }

                }

            }

        }

        return unsafeNodes;

    }

    public static boolean isFloatingNode(Node n) {

        return !(n instanceof FixedNode);

    }

    private static boolean checkKill(Node node, boolean mayKillGuard) {

        node.assertTrue(mayKillGuard || !(node instanceof GuardNode), "must not be a guard node %s", node);

        node.assertTrue(node.isAlive(), "must be alive");

        node.assertTrue(node.hasNoUsages(), "cannot kill node %s because of usages: %s", node, node.usages());

        node.assertTrue(node.predecessor() == null, "cannot kill node %s because of predecessor: %s", node, node.predecessor());

        return true;

    }

    public static void killWithUnusedFloatingInputs(Node node) {

        killWithUnusedFloatingInputs(node, false);

    }

    public static void killWithUnusedFloatingInputs(Node node, boolean mayKillGuard) {

        assert checkKill(node, mayKillGuard);

        node.markDeleted();

        outer: for (Node in : node.inputs()) {

            if (in.isAlive()) {

                in.removeUsage(node);

                if (in.hasNoUsages()) {

                    node.maybeNotifyZeroUsages(in);

                }

                if (isFloatingNode(in)) {

                    if (in.hasNoUsages()) {

                        if (in instanceof GuardNode) {

                            // Guard nodes are only killed if their anchor dies.

                        } else {

                            killWithUnusedFloatingInputs(in);

                        }

                    } else if (in instanceof PhiNode) {

                        for (Node use : in.usages()) {

                            if (use != in) {

                                continue outer;

                            }

                        }

                        in.replaceAtUsages(null);

                        killWithUnusedFloatingInputs(in);

                    }

                }

            }

        }

    }

    /**

     * Removes all nodes created after the {@code mark}, assuming no "old" nodes point to "new"

     * nodes.

     */

    public static void removeNewNodes(Graph graph, Graph.Mark mark) {

        assert checkNoOldToNewEdges(graph, mark);

        for (Node n : graph.getNewNodes(mark)) {

            n.markDeleted();

            for (Node in : n.inputs()) {

                in.removeUsage(n);

            }

        }

    }

    private static boolean checkNoOldToNewEdges(Graph graph, Graph.Mark mark) {

        for (Node old : graph.getNodes()) {

            if (graph.isNew(mark, old)) {

                break;

            }

            for (Node n : old.successors()) {

                assert !graph.isNew(mark, n) : old + " -> " + n;

            }

            for (Node n : old.inputs()) {

                assert !graph.isNew(mark, n) : old + " -> " + n;

            }

        }

        return true;

    }

    public static void removeFixedWithUnusedInputs(FixedWithNextNode fixed) {

        if (fixed instanceof StateSplit) {

            FrameState stateAfter = ((StateSplit) fixed).stateAfter();

            if (stateAfter != null) {

                ((StateSplit) fixed).setStateAfter(null);

                if (stateAfter.hasNoUsages()) {

                    killWithUnusedFloatingInputs(stateAfter);

                }

            }

        }

        unlinkFixedNode(fixed);

        killWithUnusedFloatingInputs(fixed);

    }

    public static void unlinkFixedNode(FixedWithNextNode fixed) {

        assert fixed.next() != null && fixed.predecessor() != null && fixed.isAlive() : fixed;

        FixedNode next = fixed.next();

        fixed.setNext(null);

        fixed.replaceAtPredecessor(next);

    }

    public static void checkRedundantPhi(PhiNode phiNode) {

        if (phiNode.isDeleted() || phiNode.valueCount() == 1) {

            return;

        }

        ValueNode singleValue = phiNode.singleValueOrThis();

        if (singleValue != phiNode) {

            Collection<PhiNode> phiUsages = phiNode.usages().filter(PhiNode.class).snapshot();

            Collection<ProxyNode> proxyUsages = phiNode.usages().filter(ProxyNode.class).snapshot();

            phiNode.replaceAtUsagesAndDelete(singleValue);

            for (PhiNode phi : phiUsages) {

                checkRedundantPhi(phi);

            }

            for (ProxyNode proxy : proxyUsages) {

                checkRedundantProxy(proxy);

            }

        }

    }

    public static void checkRedundantProxy(ProxyNode vpn) {

        if (vpn.isDeleted()) {

            return;

        }

        AbstractBeginNode proxyPoint = vpn.proxyPoint();

        if (proxyPoint instanceof LoopExitNode) {

            LoopExitNode exit = (LoopExitNode) proxyPoint;

            LoopBeginNode loopBegin = exit.loopBegin();

            Node vpnValue = vpn.value();

            for (ValueNode v : loopBegin.stateAfter().values()) {

                ValueNode v2 = v;

                if (loopBegin.isPhiAtMerge(v2)) {

                    v2 = ((PhiNode) v2).valueAt(loopBegin.forwardEnd());

                }

                if (vpnValue == v2) {

                    Collection<PhiNode> phiUsages = vpn.usages().filter(PhiNode.class).snapshot();

                    Collection<ProxyNode> proxyUsages = vpn.usages().filter(ProxyNode.class).snapshot();

                    vpn.replaceAtUsagesAndDelete(vpnValue);

                    for (PhiNode phi : phiUsages) {

                        checkRedundantPhi(phi);

                    }

                    for (ProxyNode proxy : proxyUsages) {

                        checkRedundantProxy(proxy);

                    }

                    return;

                }

            }

        }

    }

    /**

     * Remove loop header without loop ends. This can happen with degenerated loops like this one:

     *

     * <pre>

     * for (;;) {

     *     try {

     *         break;

     *     } catch (UnresolvedException iioe) {

     *     }

     * }

     * </pre>

     */

    public static void normalizeLoops(StructuredGraph graph) {

        boolean loopRemoved = false;

        for (LoopBeginNode begin : graph.getNodes(LoopBeginNode.TYPE)) {

            if (begin.loopEnds().isEmpty()) {

                assert begin.forwardEndCount() == 1;

                graph.reduceDegenerateLoopBegin(begin);

                loopRemoved = true;

            } else {

                normalizeLoopBegin(begin);

            }

        }

        if (loopRemoved) {

            /*

             * Removing a degenerated loop can make non-loop phi functions unnecessary. Therefore,

             * we re-check all phi functions and remove redundant ones.

             */

            for (Node node : graph.getNodes()) {

                if (node instanceof PhiNode) {

                    checkRedundantPhi((PhiNode) node);

                }

            }

        }

    }

    private static void normalizeLoopBegin(LoopBeginNode begin) {

        // Delete unnecessary loop phi functions, i.e., phi functions where all inputs are either

        // the same or the phi itself.

        for (PhiNode phi : begin.phis().snapshot()) {

            GraphUtil.checkRedundantPhi(phi);

        }

        for (LoopExitNode exit : begin.loopExits()) {

            for (ProxyNode vpn : exit.proxies().snapshot()) {

                GraphUtil.checkRedundantProxy(vpn);

            }

        }

    }

    /**

     * Gets an approximate source code location for a node if possible.

     *

     * @return the StackTraceElements if an approximate source location is found, null otherwise

     */

    public static StackTraceElement[] approxSourceStackTraceElement(Node node) {

        NodeSourcePosition position = node.getNodeSourcePosition();

        if (position != null) {

            // use GraphBuilderConfiguration and enable trackNodeSourcePosition to get better source

            // positions.