[GR-54712] Add layered string interning support.

PullRequest: graal/18075

substratevm/src/com.oracle.graal.pointsto/src/com/oracle/graal/pointsto/heap/ImageLayerWriter.java

@@ -69,6 +69,7 @@
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.IdentityHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -86,7 +87,6 @@
 import com.oracle.graal.pointsto.util.AnalysisFuture;
 import com.oracle.svm.util.FileDumpingUtil;
 
-import jdk.graal.compiler.core.common.SuppressFBWarnings;
 import jdk.graal.compiler.debug.GraalError;
 import jdk.graal.compiler.nodes.spi.IdentityHashCodeProvider;
 import jdk.graal.compiler.util.json.JsonWriter;
@@ -99,10 +99,7 @@ public class ImageLayerWriter {
  public static final String TYPE_SWITCH_SUBSTRING = "$$TypeSwitch";
  private final ImageLayerSnapshotUtil imageLayerSnapshotUtil;
  private ImageHeap imageHeap;
- /**
- * Contains the same array as StringInternSupport#imageInternedStrings, which is sorted.
- */
- private String[] imageInternedStrings;
+ private IdentityHashMap<String, String> internedStringsIdentityMap;
 
  protected EconomicMap<String, Object> jsonMap = EconomicMap.create();
  protected List<Integer> constantsToRelink;
@@ -120,8 +117,8 @@ public ImageLayerWriter(ImageLayerSnapshotUtil imageLayerSnapshotUtil) {
  this.constantsToRelink = new ArrayList<>();
  }
 
- public void setImageInternedStrings(String[] imageInternedStrings) {
- this.imageInternedStrings = imageInternedStrings;
+ public void setInternedStringsIdentityMap(IdentityHashMap<String, String> map) {
+ this.internedStringsIdentityMap = map;
  }
 
  public void setImageHeap(ImageHeap heap) {
@@ -338,16 +335,13 @@ public void persistConstantRelinkingInfo(EconomicMap<String, Object> constantMap
  }
  }
 
- @SuppressFBWarnings(value = "ES", justification = "Reference equality check needed to detect intern status")
  public void persistConstantRelinkingInfo(EconomicMap<String, Object> constantMap, BigBang bb, Class<?> clazz, JavaConstant hostedObject, int id) {
  if (clazz.equals(String.class)) {
  String value = bb.getSnippetReflectionProvider().asObject(String.class, hostedObject);
- int stringIndex = Arrays.binarySearch(imageInternedStrings, value);
- /*
- * Arrays.binarySearch compares the strings by value. A comparison by reference is
- * needed here as only interned strings are relinked.
- */
- if (stringIndex >= 0 && imageInternedStrings[stringIndex] == value) {
+ if (internedStringsIdentityMap.containsKey(value)) {
+ /*
+ * Interned strings must be relinked.
+ */
  constantMap.put(VALUE_TAG, value);
  constantsToRelink.add(id);
  }

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/StringInternSupport.java

@@ -25,7 +25,12 @@
 package com.oracle.svm.core.jdk;
 
 import java.lang.reflect.Field;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.EnumSet;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.graalvm.nativeimage.Platform;
@@ -34,10 +39,19 @@
 import com.oracle.svm.core.BuildPhaseProvider.AfterHeapLayout;
 import com.oracle.svm.core.feature.AutomaticallyRegisteredImageSingleton;
 import com.oracle.svm.core.heap.UnknownObjectField;
+import com.oracle.svm.core.imagelayer.ImageLayerBuildingSupport;
+import com.oracle.svm.core.layeredimagesingleton.ImageSingletonLoader;
+import com.oracle.svm.core.layeredimagesingleton.ImageSingletonWriter;
+import com.oracle.svm.core.layeredimagesingleton.LayeredImageSingletonBuilderFlags;
+import com.oracle.svm.core.layeredimagesingleton.MultiLayeredImageSingleton;
 import com.oracle.svm.util.ReflectionUtil;
 
 @AutomaticallyRegisteredImageSingleton
-public final class StringInternSupport {
+public final class StringInternSupport implements MultiLayeredImageSingleton {
+
+ interface SetGenerator {
+ Set<String> generateSet();
+ }
 
  @Platforms(Platform.HOSTED_ONLY.class)
  public static Field getInternedStringsField() {
@@ -59,17 +73,75 @@ public static Field getInternedStringsField() {
  */
  @UnknownObjectField(availability = AfterHeapLayout.class) private String[] imageInternedStrings;
 
+ @Platforms(Platform.HOSTED_ONLY.class) private Object priorLayersInternedStrings;
+
+ @Platforms(Platform.HOSTED_ONLY.class) private IdentityHashMap<String, String> internedStringsIdentityMap;
+
  @Platforms(Platform.HOSTED_ONLY.class)
  public StringInternSupport() {
+ this(Set.of());
+ }
+
+ private StringInternSupport(Object obj) {
  this.internedStrings = new ConcurrentHashMap<>(16, 0.75f, 1);
+ this.priorLayersInternedStrings = obj;
  }
 
  @Platforms(Platform.HOSTED_ONLY.class)
  public void setImageInternedStrings(String[] newImageInternedStrings) {
+ assert !ImageLayerBuildingSupport.buildingImageLayer();
  this.imageInternedStrings = newImageInternedStrings;
  }
 
- protected String intern(String str) {
+ @SuppressWarnings("unchecked")
+ @Platforms(Platform.HOSTED_ONLY.class)
+ public String[] layeredSetImageInternedStrings(Set<String> layerInternedStrings) {
+ assert ImageLayerBuildingSupport.buildingImageLayer();
+ /*
+ * When building a layered image, it is possible that this string has been interned in a
+ * prior layer. Thus, we must filter the interned string away from this array.
+ *
+ * In addition, the hashcode for the string should match across layers.
+ */
+ String[] currentLayerInternedStrings;
+ Set<String> priorInternedStrings;
+ if (priorLayersInternedStrings instanceof SetGenerator generator) {
+ priorInternedStrings = generator.generateSet();
+ } else {
+ priorInternedStrings = (Set<String>) priorLayersInternedStrings;
+ }
+ // don't need this anymore
+ priorLayersInternedStrings = null;
+
+ if (priorInternedStrings.isEmpty()) {
+ currentLayerInternedStrings = layerInternedStrings.toArray(String[]::new);
+ } else {
+ currentLayerInternedStrings = layerInternedStrings.stream().filter(value -> !priorInternedStrings.contains(value)).toArray(String[]::new);
+ }
+
+ Arrays.sort(currentLayerInternedStrings);
+
+ this.imageInternedStrings = currentLayerInternedStrings;
+
+ if (ImageLayerBuildingSupport.buildingSharedLayer()) {
+ internedStringsIdentityMap = new IdentityHashMap<>(priorInternedStrings.size() + currentLayerInternedStrings.length);
+ for (var value : priorInternedStrings) {
+ String internedVersion = value.intern();
+ internedStringsIdentityMap.put(internedVersion, internedVersion);
+ }
+ Arrays.stream(currentLayerInternedStrings).forEach(internedString -> internedStringsIdentityMap.put(internedString, internedString));
+ }
+
+ return imageInternedStrings;
+ }
+
+ @Platforms(Platform.HOSTED_ONLY.class)
+ public IdentityHashMap<String, String> getInternedStringsIdentityMap() {
+ assert internedStringsIdentityMap != null;
+ return internedStringsIdentityMap;
+ }
+
+ String intern(String str) {
  String result = internedStrings.get(str);
  if (result != null) {
  return result;
@@ -80,14 +152,49 @@ protected String intern(String str) {
 
  private String doIntern(String str) {
  String result = str;
- int imageIdx = Arrays.binarySearch(imageInternedStrings, str);
- if (imageIdx >= 0) {
- result = imageInternedStrings[imageIdx];
+ if (ImageLayerBuildingSupport.buildingImageLayer()) {
+ StringInternSupport[] layers = MultiLayeredImageSingleton.getAllLayers(StringInternSupport.class);
+ for (StringInternSupport layer : layers) {
+ String[] layerImageInternedStrings = layer.imageInternedStrings;
+ int imageIdx = Arrays.binarySearch(layerImageInternedStrings, str);
+ if (imageIdx >= 0) {
+ result = layerImageInternedStrings[imageIdx];
+ break;
+ }
+ }
+ } else {
+ int imageIdx = Arrays.binarySearch(imageInternedStrings, str);
+ if (imageIdx >= 0) {
+ result = imageInternedStrings[imageIdx];
+ }
  }
  String oldValue = internedStrings.putIfAbsent(result, result);
  if (oldValue != null) {
  result = oldValue;
  }
  return result;
  }
+
+ @Override
+ public EnumSet<LayeredImageSingletonBuilderFlags> getImageBuilderFlags() {
+ return LayeredImageSingletonBuilderFlags.ALL_ACCESS;
+ }
+
+ @Override
+ public PersistFlags preparePersist(ImageSingletonWriter writer) {
+ // This can be switched to use constant ids in the future
+ List<String> newPriorInternedStrings = new ArrayList<>(internedStringsIdentityMap.size());
+
+ newPriorInternedStrings.addAll(internedStringsIdentityMap.keySet());
+
+ writer.writeStringList("internedStrings", newPriorInternedStrings);
+ return PersistFlags.CREATE;
+ }
+
+ @SuppressWarnings("unused")
+ public static Object createFromLoader(ImageSingletonLoader loader) {
+ SetGenerator gen = (() -> Set.of(loader.readStringList("internedStrings").toArray(new String[0])));
+
+ return new StringInternSupport(gen);
+ }
 }

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageHeap.java

@@ -245,11 +245,17 @@ public void addTrailingObjects() {
  * By now, all interned Strings have been added to our internal interning table.
  * Populate the VM configuration with this table, and ensure it is part of the heap.
  */
- String[] imageInternedStrings = internedStrings.keySet().toArray(new String[0]);
- Arrays.sort(imageInternedStrings);
- ImageSingletons.lookup(StringInternSupport.class).setImageInternedStrings(imageInternedStrings);
- if (ImageLayerBuildingSupport.buildingSharedLayer()) {
- HostedImageLayerBuildingSupport.singleton().getWriter().setImageInternedStrings(imageInternedStrings);
+ String[] imageInternedStrings;
+ if (ImageLayerBuildingSupport.buildingImageLayer()) {
+ var internSupport = ImageSingletons.lookup(StringInternSupport.class);
+ imageInternedStrings = internSupport.layeredSetImageInternedStrings(internedStrings.keySet());
+ if (ImageLayerBuildingSupport.buildingSharedLayer()) {
+ HostedImageLayerBuildingSupport.singleton().getWriter().setInternedStringsIdentityMap(internSupport.getInternedStringsIdentityMap());
+ }
+ } else {
+ imageInternedStrings = internedStrings.keySet().toArray(new String[0]);
+ Arrays.sort(imageInternedStrings);
+ ImageSingletons.lookup(StringInternSupport.class).setImageInternedStrings(imageInternedStrings);
  }
  /* Manually snapshot the interned strings array. */
  aUniverse.getHeapScanner().rescanObject(imageInternedStrings, OtherReason.LATE_SCAN);

substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/imagelayer/LoadImageSingletonFeature.java

@@ -302,8 +302,7 @@ public void addInitialObjects(NativeImageHeap heap, HostedUniverse hUniverse) {
  /*
  * Need to install the array which points to all installed singletons.
  */
- heap.hMetaAccess.lookupJavaType(slotInfo.keyClass());
- ImageHeapObjectArray imageHeapArray = createMultiLayerArray(slotInfo.keyClass(), heap.hMetaAccess.lookupJavaType(slotInfo.keyClass()).getWrapped(),
+ ImageHeapObjectArray imageHeapArray = createMultiLayerArray(slotInfo.keyClass(), heap.hMetaAccess.lookupJavaType(slotInfo.keyClass().arrayType()).getWrapped(),
  hUniverse.getSnippetReflection());
 
  heap.addConstant(imageHeapArray, true, addReason);