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[GR-44303] Never burden @ValueBased objects with a monitor field, including boxed primitives. #6046

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Merged
merged 1 commit into from
Feb 22, 2023
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[GR-44303] Never burden @ValueBased objects with a monitor field, including boxed primitives. #6046

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20 changes: 16 additions & 4 deletions substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/HostedConfiguration.java
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
*/
package com.oracle.svm.hosted;

import java.lang.annotation.Annotation;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.HashSet;
Expand Down Expand Up @@ -74,12 +75,15 @@
import com.oracle.svm.hosted.meta.HostedMetaAccess;
import com.oracle.svm.hosted.meta.HostedUniverse;
import com.oracle.svm.hosted.substitute.UnsafeAutomaticSubstitutionProcessor;
import com.oracle.svm.util.ReflectionUtil;

import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.MetaAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaField;

public class HostedConfiguration {
@SuppressWarnings("unchecked") private static final Class<? extends Annotation> VALUE_BASED_ANNOTATION = //
(Class<? extends Annotation>) ReflectionUtil.lookupClass(false, "jdk.internal.ValueBased");

public HostedConfiguration() {
}
Expand Down Expand Up @@ -230,7 +234,10 @@ public AbstractAnalysisResultsBuilder createStaticAnalysisResultsBuilder(Inflati

public void collectMonitorFieldInfo(BigBang bb, HostedUniverse hUniverse, Set<AnalysisType> immutableTypes) {
/* First set the monitor field for types that always need it. */
getForceMonitorSlotTypes(bb).forEach(type -> setMonitorField(hUniverse, type));
for (AnalysisType type : getForceMonitorSlotTypes(bb)) {
assert !immutableTypes.contains(type);
setMonitorField(hUniverse, type);
}

/* Then decide what other types may need it. */
processedSynchronizedTypes(bb, hUniverse, immutableTypes);
Expand All @@ -253,11 +260,16 @@ protected void processedSynchronizedTypes(BigBang bb, HostedUniverse hUniverse,
}

/**
* Monitor fields on arrays would increase the array header too much. Also, types that must be
* immutable cannot have a monitor field.
* Monitor fields on arrays would enlarge the array header too much.
*
* Also, never burden @ValueBased classes with a monitor field, which in particular reduces
* sizes of boxed primitives. Using monitors with those types is discouraged (instances are
* often cached) and not guaranteed to work in the future.
*
* Types that must be immutable cannot have a monitor field.
*/
protected static void maybeSetMonitorField(HostedUniverse hUniverse, Set<AnalysisType> immutableTypes, AnalysisType type) {
if (!type.isArray() && !immutableTypes.contains(type)) {
if (!type.isArray() && !immutableTypes.contains(type) && !type.isAnnotationPresent(VALUE_BASED_ANNOTATION)) {
setMonitorField(hUniverse, type);
}
}
Expand Down