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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.
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 * 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.
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package org.graalvm.compiler.nodes.extended;

import static org.graalvm.compiler.nodeinfo.InputType.Anchor;
import static org.graalvm.compiler.nodeinfo.InputType.Guard;
import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_0;
import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_0;

import org.graalvm.compiler.core.common.type.StampFactory;
import org.graalvm.compiler.graph.NodeClass;
import org.graalvm.compiler.graph.spi.Simplifiable;
import org.graalvm.compiler.graph.spi.SimplifierTool;
import org.graalvm.compiler.nodeinfo.NodeInfo;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.FixedNode;
import org.graalvm.compiler.nodes.FixedWithNextNode;
import org.graalvm.compiler.nodes.GuardNode;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.calc.IsNullNode;
import org.graalvm.compiler.nodes.memory.FixedAccessNode;
import org.graalvm.compiler.nodes.spi.LIRLowerable;
import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
import org.graalvm.compiler.nodes.spi.Virtualizable;
import org.graalvm.compiler.nodes.spi.VirtualizerTool;
import org.graalvm.compiler.nodes.util.GraphUtil;
import org.graalvm.compiler.nodes.virtual.VirtualObjectNode;

The ValueAnchor instruction keeps non-CFG (floating) nodes above a certain point in the graph.
/** * The ValueAnchor instruction keeps non-CFG (floating) nodes above a certain point in the graph. */
@NodeInfo(allowedUsageTypes = {Anchor, Guard}, cycles = CYCLES_0, size = SIZE_0) public final class ValueAnchorNode extends FixedWithNextNode implements LIRLowerable, Simplifiable, Virtualizable, AnchoringNode, GuardingNode { public static final NodeClass<ValueAnchorNode> TYPE = NodeClass.create(ValueAnchorNode.class); @OptionalInput(Guard) ValueNode anchored; public ValueAnchorNode(ValueNode value) { super(TYPE, StampFactory.forVoid()); this.anchored = value; } @Override public void generate(NodeLIRBuilderTool gen) { // Nothing to emit, since this node is used for structural purposes only. } public ValueNode getAnchoredNode() { return anchored; } @Override public void simplify(SimplifierTool tool) { while (next() instanceof ValueAnchorNode) { ValueAnchorNode nextAnchor = (ValueAnchorNode) next(); if (nextAnchor.anchored == anchored || nextAnchor.anchored == null) { // two anchors for the same anchored -> coalesce // nothing anchored on the next anchor -> coalesce nextAnchor.replaceAtUsages(this); GraphUtil.removeFixedWithUnusedInputs(nextAnchor); } else { break; } } if (tool.allUsagesAvailable() && hasNoUsages() && next() instanceof FixedAccessNode) { FixedAccessNode currentNext = (FixedAccessNode) next(); if (currentNext.getGuard() == anchored) { GraphUtil.removeFixedWithUnusedInputs(this); return; } else if (currentNext.getGuard() == null && anchored instanceof GuardNode && ((GuardNode) anchored).getCondition() instanceof IsNullNode) { // coalesce null check guards into subsequent read/write currentNext.setGuard((GuardingNode) anchored); tool.addToWorkList(next()); return; } } if (anchored != null && (anchored.isConstant() || anchored instanceof FixedNode)) { // anchoring fixed nodes and constants is useless removeAnchoredNode(); } if (anchored == null && hasNoUsages()) { // anchor is not necessary any more => remove. GraphUtil.removeFixedWithUnusedInputs(this); } } @Override public void virtualize(VirtualizerTool tool) { if (anchored == null || anchored instanceof AbstractBeginNode) { tool.delete(); } else { ValueNode alias = tool.getAlias(anchored); if (alias instanceof VirtualObjectNode) { tool.delete(); } } } public void removeAnchoredNode() { this.updateUsages(anchored, null); this.anchored = null; } }