src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/util/GraphUtil.java
changeset 47216 71c04702a3d5
parent 46640 70bdce04c59b
child 47798 9fe9292f5931
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/util/GraphUtil.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,1025 @@
+/*
+ * Copyright (c) 2011, 2017, 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.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.function.BiFunction;
+
+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.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.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.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.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 org.graalvm.util.EconomicMap;
+import org.graalvm.util.EconomicSet;
+import org.graalvm.util.Equivalence;
+import org.graalvm.util.MapCursor;
+
+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();
+            if (Graph.Options.VerifyGraalGraphEdges.getValue(options)) {
+                unsafeNodes = collectUnsafeNodes(node.graph());
+            }
+            if (GraphUtil.Options.VerifyKillCFGUnusedNodes.getValue(options)) {
+                EconomicSet<Node> collectedUnusedNodes = unusedNodes = EconomicSet.create(Equivalence.IDENTITY);
+                nodeEventScope = node.graph().trackNodeEvents(new Graph.NodeEventListener() {
+                    @Override
+                    public void event(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 (Graph.Options.VerifyGraalGraphEdges.getValue(options)) {
+                EconomicSet<Node> newUnsafeNodes = collectUnsafeNodes(node.graph());
+                newUnsafeNodes.removeAll(unsafeNodes);
+                assert newUnsafeNodes.isEmpty() : "New unsafe nodes: " + newUnsafeNodes;
+            }
+            if (GraphUtil.Options.VerifyKillCFGUnusedNodes.getValue(options)) {
+                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.
+            return approxSourceStackTraceElement(position);
+        }
+        ArrayList<StackTraceElement> elements = new ArrayList<>();
+        Node n = node;
+        while (n != null) {
+            if (n instanceof MethodCallTargetNode) {
+                elements.add(((MethodCallTargetNode) n).targetMethod().asStackTraceElement(-1));
+                n = ((MethodCallTargetNode) n).invoke().asNode();
+            }
+
+            if (n instanceof StateSplit) {
+                FrameState state = ((StateSplit) n).stateAfter();
+                elements.addAll(Arrays.asList(approxSourceStackTraceElement(state)));
+                break;
+            }
+            n = n.predecessor();
+        }
+        return elements.toArray(new StackTraceElement[elements.size()]);
+    }
+
+    /**
+     * Gets an approximate source code location for frame state.
+     *
+     * @return the StackTraceElements if an approximate source location is found, null otherwise
+     */
+    public static StackTraceElement[] approxSourceStackTraceElement(FrameState frameState) {
+        ArrayList<StackTraceElement> elements = new ArrayList<>();
+        FrameState state = frameState;
+        while (state != null) {
+            Bytecode code = state.getCode();
+            if (code != null) {
+                elements.add(code.asStackTraceElement(state.bci - 1));
+            }
+            state = state.outerFrameState();
+        }
+        return elements.toArray(new StackTraceElement[0]);
+    }
+
+    /**
+     * Gets approximate stack trace elements for a bytecode position.
+     */
+    public static StackTraceElement[] approxSourceStackTraceElement(BytecodePosition bytecodePosition) {
+        ArrayList<StackTraceElement> elements = new ArrayList<>();
+        BytecodePosition position = bytecodePosition;
+        while (position != null) {
+            ResolvedJavaMethod method = position.getMethod();
+            if (method != null) {
+                elements.add(method.asStackTraceElement(position.getBCI()));
+            }
+            position = position.getCaller();
+        }
+        return elements.toArray(new StackTraceElement[0]);
+    }
+
+    /**
+     * Gets an approximate source code location for a node, encoded as an exception, if possible.
+     *
+     * @return the exception with the location
+     */
+    public static RuntimeException approxSourceException(Node node, Throwable cause) {
+        final StackTraceElement[] elements = approxSourceStackTraceElement(node);
+        return createBailoutException(cause == null ? "" : cause.getMessage(), cause, elements);
+    }
+
+    /**
+     * Creates a bailout exception with the given stack trace elements and message.
+     *
+     * @param message the message of the exception
+     * @param elements the stack trace elements
+     * @return the exception
+     */
+    public static BailoutException createBailoutException(String message, Throwable cause, StackTraceElement[] elements) {
+        return SourceStackTraceBailoutException.create(cause, message, elements);
+    }
+
+    /**
+     * Gets an approximate source code location for a node if possible.
+     *
+     * @return a file name and source line number in stack trace format (e.g. "String.java:32") if
+     *         an approximate source location is found, null otherwise
+     */
+    public static String approxSourceLocation(Node node) {
+        StackTraceElement[] stackTraceElements = approxSourceStackTraceElement(node);
+        if (stackTraceElements != null && stackTraceElements.length > 0) {
+            StackTraceElement top = stackTraceElements[0];
+            if (top.getFileName() != null && top.getLineNumber() >= 0) {
+                return top.getFileName() + ":" + top.getLineNumber();
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Returns a string representation of the given collection of objects.
+     *
+     * @param objects The {@link Iterable} that will be used to iterate over the objects.
+     * @return A string of the format "[a, b, ...]".
+     */
+    public static String toString(Iterable<?> objects) {
+        StringBuilder str = new StringBuilder();
+        str.append("[");
+        for (Object o : objects) {
+            str.append(o).append(", ");
+        }
+        if (str.length() > 1) {
+            str.setLength(str.length() - 2);
+        }
+        str.append("]");
+        return str.toString();
+    }
+
+    /**
+     * Gets the original value by iterating through all {@link ValueProxy ValueProxies}.
+     *
+     * @param value the start value.
+     * @return the first non-proxy value encountered
+     */
+    public static ValueNode unproxify(ValueNode value) {
+        if (value instanceof ValueProxy) {
+            return unproxify((ValueProxy) value);
+        } else {
+            return value;
+        }
+    }
+
+    /**
+     * Gets the original value by iterating through all {@link ValueProxy ValueProxies}.
+     *
+     * @param value the start value proxy.
+     * @return the first non-proxy value encountered
+     */
+    public static ValueNode unproxify(ValueProxy value) {
+        if (value != null) {
+            ValueNode result = value.getOriginalNode();
+            while (result instanceof ValueProxy) {
+                result = ((ValueProxy) result).getOriginalNode();
+            }
+            return result;
+        } else {
+            return null;
+        }
+    }
+
+    public static ValueNode skipPi(ValueNode node) {
+        ValueNode n = node;
+        while (n instanceof PiNode) {
+            PiNode piNode = (PiNode) n;
+            n = piNode.getOriginalNode();
+        }
+        return n;
+    }
+
+    public static ValueNode skipPiWhileNonNull(ValueNode node) {
+        ValueNode n = node;
+        while (n instanceof PiNode) {
+            PiNode piNode = (PiNode) n;
+            ObjectStamp originalStamp = (ObjectStamp) piNode.getOriginalNode().stamp();
+            if (originalStamp.nonNull()) {
+                n = piNode.getOriginalNode();
+            } else {
+                break;
+            }
+        }
+        return n;
+    }
+
+    /**
+     * Looks for an {@link ArrayLengthProvider} while iterating through all {@link ValueProxy
+     * ValueProxies}.
+     *
+     * @param value The start value.
+     * @return The array length if one was found, or null otherwise.
+     */
+    public static ValueNode arrayLength(ValueNode value) {
+        ValueNode current = value;
+        do {
+            if (current instanceof ArrayLengthProvider) {
+                ValueNode length = ((ArrayLengthProvider) current).length();
+                if (length != null) {
+                    return length;
+                }
+            }
+            if (current instanceof ValueProxy) {
+                current = ((ValueProxy) current).getOriginalNode();
+            } else {
+                break;
+            }
+        } while (true);
+        return null;
+    }
+
+    /**
+     * Tries to find an original value of the given node by traversing through proxies and
+     * unambiguous phis. Note that this method will perform an exhaustive search through phis. It is
+     * intended to be used during graph building, when phi nodes aren't yet canonicalized.
+     *
+     * @param value The node whose original value should be determined.
+     * @return The original value (which might be the input value itself).
+     */
+    public static ValueNode originalValue(ValueNode value) {
+        ValueNode result = originalValueSimple(value);
+        assert result != null;
+        return result;
+    }
+
+    private static ValueNode originalValueSimple(ValueNode value) {
+        /* The very simple case: look through proxies. */
+        ValueNode cur = originalValueForProxy(value);
+
+        while (cur instanceof PhiNode) {
+            /*
+             * We found a phi function. Check if we can analyze it without allocating temporary data
+             * structures.
+             */
+            PhiNode phi = (PhiNode) cur;
+
+            ValueNode phiSingleValue = null;
+            int count = phi.valueCount();
+            for (int i = 0; i < count; ++i) {
+                ValueNode phiCurValue = originalValueForProxy(phi.valueAt(i));
+                if (phiCurValue == phi) {
+                    /* Simple cycle, we can ignore the input value. */
+                } else if (phiSingleValue == null) {
+                    /* The first input. */
+                    phiSingleValue = phiCurValue;
+                } else if (phiSingleValue != phiCurValue) {
+                    /* Another input that is different from the first input. */
+
+                    if (phiSingleValue instanceof PhiNode || phiCurValue instanceof PhiNode) {
+                        /*
+                         * We have two different input values for the phi function, and at least one
+                         * of the inputs is another phi function. We need to do a complicated
+                         * exhaustive check.
+                         */
+                        return originalValueForComplicatedPhi(phi, new NodeBitMap(value.graph()));
+                    } else {
+                        /*
+                         * We have two different input values for the phi function, but none of them
+                         * is another phi function. This phi function cannot be reduce any further,
+                         * so the phi function is the original value.
+                         */
+                        return phi;
+                    }
+                }
+            }
+
+            /*
+             * Successfully reduced the phi function to a single input value. The single input value
+             * can itself be a phi function again, so we might take another loop iteration.
+             */
+            assert phiSingleValue != null;
+            cur = phiSingleValue;
+        }
+
+        /* We reached a "normal" node, which is the original value. */
+        assert !(cur instanceof LimitedValueProxy) && !(cur instanceof PhiNode);
+        return cur;
+    }
+
+    private static ValueNode originalValueForProxy(ValueNode value) {
+        ValueNode cur = value;
+        while (cur instanceof LimitedValueProxy) {
+            cur = ((LimitedValueProxy) cur).getOriginalNode();
+        }
+        return cur;
+    }
+
+    /**
+     * Handling for complicated nestings of phi functions. We need to reduce phi functions
+     * recursively, and need a temporary map of visited nodes to avoid endless recursion of cycles.
+     */
+    private static ValueNode originalValueForComplicatedPhi(PhiNode phi, NodeBitMap visited) {
+        if (visited.isMarked(phi)) {
+            /*
+             * Found a phi function that was already seen. Either a cycle, or just a second phi
+             * input to a path we have already processed.
+             */
+            return null;
+        }
+        visited.mark(phi);
+
+        ValueNode phiSingleValue = null;
+        int count = phi.valueCount();
+        for (int i = 0; i < count; ++i) {
+            ValueNode phiCurValue = originalValueForProxy(phi.valueAt(i));
+            if (phiCurValue instanceof PhiNode) {
+                /* Recursively process a phi function input. */
+                phiCurValue = originalValueForComplicatedPhi((PhiNode) phiCurValue, visited);
+            }
+
+            if (phiCurValue == null) {
+                /* Cycle to a phi function that was already seen. We can ignore this input. */
+            } else if (phiSingleValue == null) {
+                /* The first input. */
+                phiSingleValue = phiCurValue;
+            } else if (phiCurValue != phiSingleValue) {
+                /*
+                 * Another input that is different from the first input. Since we already
+                 * recursively looked through other phi functions, we now know that this phi
+                 * function cannot be reduce any further, so the phi function is the original value.
+                 */
+                return phi;
+            }
+        }
+        return phiSingleValue;
+    }
+
+    public static boolean tryKillUnused(Node node) {
+        if (node.isAlive() && isFloatingNode(node) && node.hasNoUsages() && !(node instanceof GuardNode)) {
+            killWithUnusedFloatingInputs(node);
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Returns an iterator that will return the given node followed by all its predecessors, up
+     * until the point where {@link Node#predecessor()} returns null.
+     *
+     * @param start the node at which to start iterating
+     */
+    public static NodeIterable<FixedNode> predecessorIterable(final FixedNode start) {
+        return new NodeIterable<FixedNode>() {
+            @Override
+            public Iterator<FixedNode> iterator() {
+                return new Iterator<FixedNode>() {
+                    public FixedNode current = start;
+
+                    @Override
+                    public boolean hasNext() {
+                        return current != null;
+                    }
+
+                    @Override
+                    public FixedNode next() {
+                        try {
+                            return current;
+                        } finally {
+                            current = (FixedNode) current.predecessor();
+                        }
+                    }
+                };
+            }
+        };
+    }
+
+    private static final class DefaultSimplifierTool implements SimplifierTool {
+        private final MetaAccessProvider metaAccess;
+        private final ConstantReflectionProvider constantReflection;
+        private final ConstantFieldProvider constantFieldProvider;
+        private final boolean canonicalizeReads;
+        private final Assumptions assumptions;
+        private final OptionValues options;
+        private final LoweringProvider loweringProvider;
+
+        DefaultSimplifierTool(MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection, ConstantFieldProvider constantFieldProvider, boolean canonicalizeReads,
+                        Assumptions assumptions, OptionValues options, LoweringProvider loweringProvider) {
+            this.metaAccess = metaAccess;
+            this.constantReflection = constantReflection;
+            this.constantFieldProvider = constantFieldProvider;
+            this.canonicalizeReads = canonicalizeReads;
+            this.assumptions = assumptions;
+            this.options = options;
+            this.loweringProvider = loweringProvider;
+        }
+
+        @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 true;
+        }
+
+        @Override
+        public void deleteBranch(Node branch) {
+            FixedNode fixedBranch = (FixedNode) branch;
+            fixedBranch.predecessor().replaceFirstSuccessor(fixedBranch, null);
+            GraphUtil.killCFG(fixedBranch);
+        }
+
+        @Override
+        public void removeIfUnused(Node node) {
+            GraphUtil.tryKillUnused(node);
+        }
+
+        @Override
+        public void addToWorkList(Node node) {
+        }
+
+        @Override
+        public void addToWorkList(Iterable<? extends Node> nodes) {
+        }
+
+        @Override
+        public Assumptions getAssumptions() {
+            return assumptions;
+        }
+
+        @Override
+        public OptionValues getOptions() {
+            return options;
+        }
+
+        @Override
+        public Integer smallestCompareWidth() {
+            if (loweringProvider != null) {
+                return loweringProvider.smallestCompareWidth();
+            } else {
+                return null;
+            }
+        }
+    }
+
+    public static SimplifierTool getDefaultSimplifier(MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection, ConstantFieldProvider constantFieldProvider,
+                    boolean canonicalizeReads, Assumptions assumptions, OptionValues options) {
+        return getDefaultSimplifier(metaAccess, constantReflection, constantFieldProvider, canonicalizeReads, assumptions, options, null);
+    }
+
+    public static SimplifierTool getDefaultSimplifier(MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection, ConstantFieldProvider constantFieldProvider,
+                    boolean canonicalizeReads, Assumptions assumptions, OptionValues options, LoweringProvider loweringProvider) {
+        return new DefaultSimplifierTool(metaAccess, constantReflection, constantFieldProvider, canonicalizeReads, assumptions, options, loweringProvider);
+    }
+
+    public static Constant foldIfConstantAndRemove(ValueNode node, ValueNode constant) {
+        assert node.inputs().contains(constant);
+        if (constant.isConstant()) {
+            node.replaceFirstInput(constant, null);
+            Constant result = constant.asConstant();
+            tryKillUnused(constant);
+            return result;
+        }
+        return null;
+    }
+
+    /**
+     * Virtualize an array copy.
+     *
+     * @param tool the virtualization tool
+     * @param source the source array
+     * @param sourceLength the length of the source array
+     * @param newLength the length of the new array
+     * @param from the start index in the source array
+     * @param newComponentType the component type of the new array
+     * @param elementKind the kind of the new array elements
+     * @param graph the node graph
+     * @param virtualArrayProvider a functional provider that returns a new virtual array given the
+     *            component type and length
+     */
+    public static void virtualizeArrayCopy(VirtualizerTool tool, ValueNode source, ValueNode sourceLength, ValueNode newLength, ValueNode from, ResolvedJavaType newComponentType, JavaKind elementKind,
+                    StructuredGraph graph, BiFunction<ResolvedJavaType, Integer, VirtualArrayNode> virtualArrayProvider) {
+
+        ValueNode sourceAlias = tool.getAlias(source);
+        ValueNode replacedSourceLength = tool.getAlias(sourceLength);
+        ValueNode replacedNewLength = tool.getAlias(newLength);
+        ValueNode replacedFrom = tool.getAlias(from);
+        if (!replacedNewLength.isConstant() || !replacedFrom.isConstant() || !replacedSourceLength.isConstant()) {
+            return;
+        }
+
+        assert newComponentType != null : "An array copy can be virtualized only if the real type of the resulting array is known statically.";
+
+        int fromInt = replacedFrom.asJavaConstant().asInt();
+        int newLengthInt = replacedNewLength.asJavaConstant().asInt();
+        int sourceLengthInt = replacedSourceLength.asJavaConstant().asInt();
+        if (sourceAlias instanceof VirtualObjectNode) {
+            VirtualObjectNode sourceVirtual = (VirtualObjectNode) sourceAlias;
+            assert sourceLengthInt == sourceVirtual.entryCount();
+        }
+
+        if (fromInt < 0 || newLengthInt < 0 || fromInt > sourceLengthInt) {
+            /* Illegal values for either from index, the new length or the source length. */
+            return;
+        }
+
+        if (newLengthInt >= tool.getMaximumEntryCount()) {
+            /* The new array size is higher than maximum allowed size of virtualized objects. */
+            return;
+        }
+
+        ValueNode[] newEntryState = new ValueNode[newLengthInt];
+        int readLength = Math.min(newLengthInt, sourceLengthInt - fromInt);
+
+        if (sourceAlias instanceof VirtualObjectNode) {
+            /* The source array is virtualized, just copy over the values. */
+            VirtualObjectNode sourceVirtual = (VirtualObjectNode) sourceAlias;
+            for (int i = 0; i < readLength; i++) {
+                newEntryState[i] = tool.getEntry(sourceVirtual, fromInt + i);
+            }
+        } else {
+            /* The source array is not virtualized, emit index loads. */
+            for (int i = 0; i < readLength; i++) {
+                LoadIndexedNode load = new LoadIndexedNode(null, sourceAlias, ConstantNode.forInt(i + fromInt, graph), elementKind);
+                tool.addNode(load);
+                newEntryState[i] = load;
+            }
+        }
+        if (readLength < newLengthInt) {
+            /* Pad the copy with the default value of its elment kind. */
+            ValueNode defaultValue = ConstantNode.defaultForKind(elementKind, graph);
+            for (int i = readLength; i < newLengthInt; i++) {
+                newEntryState[i] = defaultValue;
+            }
+        }
+        /* Perform the replacement. */
+        VirtualArrayNode newVirtualArray = virtualArrayProvider.apply(newComponentType, newLengthInt);
+        tool.createVirtualObject(newVirtualArray, newEntryState, Collections.<MonitorIdNode> emptyList(), false);
+        tool.replaceWithVirtual(newVirtualArray);
+    }
+}