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Thomas Schrott
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Add util class for filler objects
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-38
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3 files changed

+82
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‎substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/FillerObjectUtil.java‎

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/*
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* Copyright (c) 2025, 2025, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.oracle.svm.core.genscavenge;
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import static com.oracle.svm.core.Uninterruptible.CALLED_FROM_UNINTERRUPTIBLE_CODE;
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import static jdk.graal.compiler.replacements.AllocationSnippets.FillContent.WITH_GARBAGE_IF_ASSERTIONS_ENABLED;
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import org.graalvm.word.Pointer;
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import org.graalvm.word.UnsignedWord;
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import com.oracle.svm.core.Uninterruptible;
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import com.oracle.svm.core.config.ConfigurationValues;
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import com.oracle.svm.core.genscavenge.graal.nodes.FormatArrayNode;
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import com.oracle.svm.core.genscavenge.graal.nodes.FormatObjectNode;
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import com.oracle.svm.core.heap.FillerArray;
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import com.oracle.svm.core.heap.FillerObject;
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import com.oracle.svm.core.hub.LayoutEncoding;
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import com.oracle.svm.core.util.UnsignedUtils;
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import jdk.graal.compiler.api.replacements.Fold;
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import jdk.graal.compiler.core.common.NumUtil;
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import jdk.graal.compiler.word.Word;
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import jdk.vm.ci.meta.JavaKind;
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public class FillerObjectUtil {
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private static final Class<?> ARRAY_CLASS = FillerArray.class;
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private static final JavaKind ARRAY_ELEMENT_KIND = JavaKind.Int;
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private static final int ARRAY_ELEMENT_SIZE = ARRAY_ELEMENT_KIND.getByteCount();
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@Fold
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public static UnsignedWord objectMinSize() {
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return Word.unsigned(ConfigurationValues.getObjectLayout().getMinImageHeapObjectSize());
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}
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@Fold
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static int arrayMinSize() {
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return NumUtil.safeToInt(ConfigurationValues.getObjectLayout().getArraySize(ARRAY_ELEMENT_KIND, 0, false));
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}
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@Fold
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static int arrayBaseOffset() {
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return ConfigurationValues.getObjectLayout().getArrayBaseOffset(ARRAY_ELEMENT_KIND);
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}
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@Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)
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public static void writeFillerObjectAt(Pointer p, UnsignedWord size) {
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assert size.aboveThan(0);
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if (size.aboveOrEqual(arrayMinSize())) {
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int length = UnsignedUtils.safeToInt(size.subtract(arrayBaseOffset()).unsignedDivide(ARRAY_ELEMENT_SIZE));
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FormatArrayNode.formatArray(p, ARRAY_CLASS, length, true, false, WITH_GARBAGE_IF_ASSERTIONS_ENABLED, false);
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} else {
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FormatObjectNode.formatObject(p, FillerObject.class, true, WITH_GARBAGE_IF_ASSERTIONS_ENABLED, false);
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}
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assert LayoutEncoding.getSizeFromObjectInGC(p.toObject()).equal(size);
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}
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}

‎substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/compacting/SweepingVisitor.java‎

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*/
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package com.oracle.svm.core.genscavenge.compacting;
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import static jdk.graal.compiler.replacements.AllocationSnippets.FillContent.WITH_GARBAGE_IF_ASSERTIONS_ENABLED;
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import org.graalvm.word.Pointer;
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import org.graalvm.word.UnsignedWord;
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import com.oracle.svm.core.config.ConfigurationValues;
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import com.oracle.svm.core.genscavenge.AlignedHeapChunk;
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import com.oracle.svm.core.genscavenge.FillerObjectUtil;
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import com.oracle.svm.core.genscavenge.HeapChunk;
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import com.oracle.svm.core.genscavenge.graal.nodes.FormatArrayNode;
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import com.oracle.svm.core.genscavenge.graal.nodes.FormatObjectNode;
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import com.oracle.svm.core.heap.FillerArray;
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import com.oracle.svm.core.heap.FillerObject;
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import com.oracle.svm.core.hub.LayoutEncoding;
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import com.oracle.svm.core.util.UnsignedUtils;
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import jdk.graal.compiler.api.replacements.Fold;
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import jdk.graal.compiler.core.common.NumUtil;
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import jdk.vm.ci.meta.JavaKind;
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/**
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* Overwrites dead objects with filler objects so that heap walks or scans that use card tables
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* cannot encounter them (and their broken references).
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*/
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public final class SweepingVisitor implements ObjectMoveInfo.Visitor {
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private static final Class<?> ARRAY_CLASS = FillerArray.class;
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private static final JavaKind ARRAY_ELEMENT_KIND = JavaKind.Int;
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private static final int ARRAY_ELEMENT_SIZE = ARRAY_ELEMENT_KIND.getByteCount();
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@Fold
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static int arrayMinSize() {
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return NumUtil.safeToInt(ConfigurationValues.getObjectLayout().getArraySize(ARRAY_ELEMENT_KIND, 0, false));
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}
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@Fold
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static int arrayBaseOffset() {
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return ConfigurationValues.getObjectLayout().getArrayBaseOffset(ARRAY_ELEMENT_KIND);
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}
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@Override
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public boolean visit(Pointer objSeq, UnsignedWord size, Pointer newAddress, Pointer nextObjSeq) {
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assert objSeq.equal(newAddress);
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if (nextObjSeq.isNonNull()) {
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Pointer gapStart = objSeq.add(size);
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assert gapStart.belowThan(nextObjSeq);
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writeFillerObjectAt(gapStart, nextObjSeq.subtract(gapStart));
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FillerObjectUtil.writeFillerObjectAt(gapStart, nextObjSeq.subtract(gapStart));
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// Note that we have already added first object table entries for fillers during fixup.
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} else {
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AlignedHeapChunk.AlignedHeader chunk = AlignedHeapChunk.getEnclosingChunkFromObjectPointer(objSeq);
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assert objSeq.add(size).equal(HeapChunk.getTopPointer(chunk));
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}
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return true;
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}
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private static void writeFillerObjectAt(Pointer p, UnsignedWord size) {
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assert size.aboveThan(0);
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if (size.aboveOrEqual(arrayMinSize())) {
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int length = UnsignedUtils.safeToInt(size.subtract(arrayBaseOffset()).unsignedDivide(ARRAY_ELEMENT_SIZE));
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FormatArrayNode.formatArray(p, ARRAY_CLASS, length, true, false, WITH_GARBAGE_IF_ASSERTIONS_ENABLED, false);
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} else {
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FormatObjectNode.formatObject(p, FillerObject.class, true, WITH_GARBAGE_IF_ASSERTIONS_ENABLED, false);
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}
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assert LayoutEncoding.getSizeFromObjectInGC(p.toObject()).equal(size);
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}
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}

‎substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/config/ObjectLayout.java‎

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import com.oracle.svm.core.util.VMError;
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import jdk.graal.compiler.api.directives.GraalDirectives;
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import jdk.graal.compiler.api.replacements.Fold;
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import jdk.graal.compiler.core.common.NumUtil;
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import jdk.graal.compiler.replacements.ReplacementsUtil;
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import jdk.vm.ci.code.CodeUtil;
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return NumUtil.safeToInt(getArraySize(JavaKind.Byte, 0, true));
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}
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@Fold
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public int getMinImageHeapObjectSize() {
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return Math.min(getMinImageHeapArraySize(), getMinImageHeapInstanceSize());
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}

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