[GR-69666] JVMCI: Add ResolvedJavaType#{isSealed,getPermittedSubclasses}

src/hotspot/share/jvmci/vmStructs_jvmci.cpp

@@ -165,6 +165,8 @@
   unchecked_nonstatic_field(Array<u2>,         _data,                                  sizeof(u2))                                   \
   nonstatic_field(Array<Klass*>,               _length,                                int)                                          \
   nonstatic_field(Array<Klass*>,               _data[0],                               Klass*)                                       \
+  unchecked_nonstatic_field(Array<jushort>,    _data,                                  sizeof(jushort))                              \
+  nonstatic_field(Array<jushort>,              _length,                                int)                                          \
                                                                                                                                      \
   volatile_nonstatic_field(BasicLock,          _metadata,                              uintptr_t)                                    \
                                                                                                                                      \
@@ -221,6 +223,7 @@
   volatile_nonstatic_field(InstanceKlass,      _init_thread,                                  JavaThread*)                           \
   nonstatic_field(InstanceKlass,               _misc_flags._flags,                            u2)                                    \
   nonstatic_field(InstanceKlass,               _annotations,                                  Annotations*)                          \
+  nonstatic_field(InstanceKlass,               _permitted_subclasses,                         Array<jushort>*)                       \
                                                                                                                                      \
   volatile_nonstatic_field(JavaFrameAnchor,    _last_Java_sp,                                 intptr_t*)                             \
   volatile_nonstatic_field(JavaFrameAnchor,    _last_Java_pc,                                 address)                               \

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotResolvedObjectTypeImpl.java

@@ -34,6 +34,8 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.nio.ByteOrder;
+import java.util.Collections;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 
@@ -100,7 +102,7 @@ static HotSpotResolvedObjectTypeImpl getJavaLangObject() {
 
     /**
      * Gets the JVMCI mirror from a HotSpot type.
-     *
+     * <p>
      * Called from the VM.
      *
      * @param klassPointer a native pointer to the Klass*
@@ -183,6 +185,67 @@ public ResolvedJavaType getComponentType() {
         return this.equals(componentType) ? null : componentType;
     }
 
+    @Override
+    public List<JavaType> getPermittedSubclasses() {
+        if (isArray() || isPrimitive()) {
+            return null;
+        }
+        HotSpotVMConfig config = config();
+        final long metaspacePermittedSubclasses = UNSAFE.getAddress(getKlassPointer() + config.instanceKlassPermittedSubclassesOffset);
+        if (metaspacePermittedSubclasses == 0) {
+            return null;
+        }
+        final int length = UNSAFE.getInt(metaspacePermittedSubclasses + config.arrayJUShortLengthOffset);
+        if (length == 0) {
+            return null;
+        }
+        // is_sealed
+        ArrayList<JavaType> permittedSubclasses = new ArrayList<>(length);
+        for (long i = 0; i < length; i++) {
+            int cpIndex = UNSAFE.getShort(metaspacePermittedSubclasses + config.arrayJUShortDataOffset + compilerToVM().ARRAY_SHORT_INDEX_SCALE * i);
+            Object cpEntry = getConstantPool().lookupConstant(cpIndex);
+            if (cpEntry instanceof ResolvedJavaType rjt) {
+                if (isDirectSubType(rjt)) {
+                    // only adding direct subtypes
+                    permittedSubclasses.add(rjt);
+                }
+            } else if (cpEntry instanceof UnresolvedJavaType ujr) {
+                // Unresolved - cannot tell if it is a direct or indirect subtype
+                permittedSubclasses.add(ujr);
+            } else {
+                throw new InternalError("Unexpected ConstantPool entry: " + cpEntry);
+            }
+        }
+        return Collections.unmodifiableList(permittedSubclasses);
+    }
+
+    @Override
+    public boolean isSealed() {
+        if (isArray()) {
+            return false;
+        }
+        HotSpotVMConfig config = config();
+        final long metaspacePermittedSubclasses = UNSAFE.getAddress(getKlassPointer() + config.instanceKlassPermittedSubclassesOffset);
+        if (metaspacePermittedSubclasses == 0) {
+            return false;
+        }
+        final int length = UNSAFE.getInt(metaspacePermittedSubclasses + config.arrayJUShortLengthOffset);
+        return length != 0;
+    }
+
+    private boolean isDirectSubType(ResolvedJavaType c) {
+        if (isInterface()) {
+            for (ResolvedJavaType i : c.getInterfaces()) {
+                if (i == this) {
+                    return true;
+                }
+            }
+        } else {
+            return c.getSuperclass() == this;
+        }
+        return false;
+    }
+
     @Override
     public AssumptionResult<ResolvedJavaType> findLeafConcreteSubtype() {
         if (isLeaf()) {
@@ -694,11 +757,11 @@ static class FieldInfo {
         /**
          * Creates a field info with the provided indices.
          *
-         * @param nameIndex index of field's name in the constant pool
-         * @param signatureIndex index of field's signature in the constant pool
-         * @param offset field's offset
-         * @param classfileFlags field's access flags (from the class file)
-         * @param internalFlags field's internal flags (from the VM)
+         * @param nameIndex        index of field's name in the constant pool
+         * @param signatureIndex   index of field's signature in the constant pool
+         * @param offset           field's offset
+         * @param classfileFlags   field's access flags (from the class file)
+         * @param internalFlags    field's internal flags (from the VM)
          * @param initializerIndex field's initial value index in the constant pool
          */
         FieldInfo(int nameIndex, int signatureIndex, int offset, int classfileFlags, int internalFlags, int initializerIndex) {
@@ -737,6 +800,7 @@ public int getOffset() {
         /**
          * Returns the name of this field as a {@link String}. If the field is an internal field the
          * name index is pointing into the vmSymbols table.
+         *
          * @param klass field's holder class
          */
         public String getName(HotSpotResolvedObjectTypeImpl klass) {
@@ -746,6 +810,7 @@ public String getName(HotSpotResolvedObjectTypeImpl klass) {
         /**
          * Returns the signature of this field as {@link String}. If the field is an internal field
          * the signature index is pointing into the vmSymbols table.
+         *
          * @param klass field's holder class
          */
         public String getSignature(HotSpotResolvedObjectTypeImpl klass) {
@@ -828,7 +893,7 @@ public ResolvedJavaField[] getStaticFields() {
      * Gets the instance or static fields of this class.
      *
      * @param retrieveStaticFields specifies whether to return instance or static fields
-     * @param prepend an array to be prepended to the returned result
+     * @param prepend              an array to be prepended to the returned result
      */
     private HotSpotResolvedJavaField[] getFields(boolean retrieveStaticFields, HotSpotResolvedJavaField[] prepend) {
         HotSpotVMConfig config = config();
@@ -954,7 +1019,7 @@ public boolean isDefinitelyResolvedWithRespectTo(ResolvedJavaType accessingClass
 
     private boolean hasSameClassLoader(HotSpotResolvedObjectTypeImpl otherMirror) {
         return UnsafeAccess.UNSAFE.getAddress(getKlassPointer() + config().classLoaderDataOffset) == UnsafeAccess.UNSAFE.getAddress(
-                        otherMirror.getKlassPointer() + config().classLoaderDataOffset);
+                otherMirror.getKlassPointer() + config().classLoaderDataOffset);
     }
 
     @Override

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotResolvedPrimitiveType.java

@@ -102,6 +102,16 @@ public ResolvedJavaType getElementalType() {
         return this;
     }
 
+    @Override
+    public List<JavaType> getPermittedSubclasses() {
+        return null;
+    }
+
+    @Override
+    public boolean isSealed() {
+        return false;
+    }
+
     @Override
     public ResolvedJavaType getComponentType() {
         return null;

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotVMConfig.java

@@ -26,7 +26,6 @@
 import static jdk.vm.ci.hotspot.UnsafeAccess.UNSAFE;
 
 import jdk.vm.ci.common.JVMCIError;
-import jdk.vm.ci.services.Services;
 import jdk.internal.misc.Unsafe;
 import jdk.internal.util.Architecture;
 
@@ -97,6 +96,7 @@ static String getHostArchitectureName() {
     final int instanceKlassConstantsOffset = getFieldOffset("InstanceKlass::_constants", Integer.class, "ConstantPool*");
     final int instanceKlassFieldInfoStreamOffset = getFieldOffset("InstanceKlass::_fieldinfo_stream", Integer.class, "Array<u1>*");
     final int instanceKlassAnnotationsOffset = getFieldOffset("InstanceKlass::_annotations", Integer.class, "Annotations*");
+    final int instanceKlassPermittedSubclassesOffset = getFieldOffset("InstanceKlass::_permitted_subclasses", Integer.class, "Array<jushort>*");
     final int instanceKlassMiscFlagsOffset = getFieldOffset("InstanceKlass::_misc_flags._flags", Integer.class, "u2");
     final int klassMiscFlagsOffset = getFieldOffset("Klass::_misc_flags._flags", Integer.class, "u1");
     final int klassVtableStartOffset = getFieldValue("CompilerToVM::Data::Klass_vtable_start_offset", Integer.class, "int");
@@ -113,6 +113,8 @@ static String getHostArchitectureName() {
     final int arrayU1LengthOffset = getFieldOffset("Array<int>::_length", Integer.class, "int");
     final int arrayU1DataOffset = getFieldOffset("Array<u1>::_data", Integer.class);
     final int arrayU2DataOffset = getFieldOffset("Array<u2>::_data", Integer.class);
+    final int arrayJUShortDataOffset = getFieldOffset("Array<jushort>::_data", Integer.class);
+    final int arrayJUShortLengthOffset = getFieldOffset("Array<jushort>::_length", Integer.class, "int");
 
     final int jvmAccHasFinalizer = getConstant("KlassFlags::_misc_has_finalizer", Integer.class);
     final int jvmFieldFlagInternalShift = getConstant("FieldInfo::FieldFlags::_ff_injected", Integer.class);

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/meta/ResolvedJavaType.java

@@ -247,6 +247,42 @@ default ResolvedJavaType getElementalType() {
     @Override
     ResolvedJavaType getArrayClass();
 
+    /**
+     * Returns an unmodifiable list of {@link JavaType} objects representing the subclasses or
+     * subinterfaces that are explicitly permitted to extend or implement this sealed class or
+     * interface, as declared in its <em>PermittedSubclasses</em> class file attribute. Only direct
+     * subtypes listed by the sealing declaration are included.
+     * <p>
+     * For each subtype, if it is resolved, the entry will be a {@link ResolvedJavaType}; otherwise
+     * it will be an {@link UnresolvedJavaType}. For unresolved subtypes, callers must not assume
+     * whether a type is a direct or indirect permitted subtype. The order of the results matches
+     * that of {@link Class#getPermittedSubclasses()}.
+     * <p>
+     * If the type is not sealed, returns {@code null}.
+     *
+     * @return unmodifiable list of permitted subtypes, or {@code null} if this type is not sealed
+     * @see Class#getPermittedSubclasses()
+     */
+    List<JavaType> getPermittedSubclasses();
+
+    /**
+     * Returns {@code true} if and only if this type represents a sealed class or
+     * interface. If this type represents a primitive type, {@code void}, or an array
+     * type, this method returns {@code false}. A sealed class or interface has
+     * (possibly zero) permitted subclasses; {@link #getPermittedSubclasses()} returns
+     * a non-null but possibly empty value for a sealed class or interface.
+     *
+     * @return {@code true} if and only if this type represents a sealed class
+     * or interface.
+     * @see Class#isSealed()
+     */
+    default boolean isSealed() {
+        if (isArray() || isPrimitive()) {
+            return false;
+        }
+        return getPermittedSubclasses() != null;
+    }
+
     /**
      * Resolves the method implementation for virtual dispatches on objects of this dynamic type.
      * This resolution process only searches "up" the class hierarchy of this type. A broader search

test/hotspot/jtreg/compiler/jvmci/jdk.vm.ci.runtime.test/src/jdk/vm/ci/runtime/test/TestResolvedJavaType.java

@@ -59,6 +59,7 @@
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 import java.io.DataInputStream;
 import java.io.IOException;
@@ -708,6 +709,48 @@ public void getArrayClassTest() {
         }
     }
 
+    private static sealed class SealedTestClass
+      permits PermittedTestClass1, PermittedTestClass3 {
+    }
+
+    private static sealed class PermittedTestClass1 extends SealedTestClass
+      permits PermittedTestClass2 {
+    }
+
+    private static final class PermittedTestClass2 extends PermittedTestClass1 {
+    }
+
+    private static final class PermittedTestClass3 extends SealedTestClass {
+    }
+
+    private static class UnsealedTestClass {
+    }
+
+    private static final class UnsealedTestSubClass extends UnsealedTestClass {
+    }
+
+    @Test
+    public void getPermittedSubclassesTest() {
+        assertGetPermittedSubclasses(int.class);
+        assertGetPermittedSubclasses(void.class);
+        assertGetPermittedSubclasses(UnsealedTestClass.class);
+        assertGetPermittedSubclasses(SealedTestClass.class);
+    }
+
+    private void assertGetPermittedSubclasses(Class<?> clazz) {
+        ResolvedJavaType type = metaAccess.lookupJavaType(clazz);
+        assertEquals("Sealed status mismatch for class '" + clazz.getName(), clazz.isSealed(), type.isSealed());
+        List<JavaType> actual = type.getPermittedSubclasses();
+        Class<?>[] expected = clazz.getPermittedSubclasses();
+        if (expected == null) {
+            assertNull(actual);
+        } else {
+            Set<JavaType> actualSet = new HashSet<>(actual);
+            Set<JavaType> expectedSet = Arrays.stream(expected).map(metaAccess::lookupJavaType).collect(Collectors.toSet());
+            assertEquals(expectedSet, actualSet);
+        }
+    }
+
     static class Declarations {
 
         final Method implementation;
@@ -1313,6 +1356,7 @@ public void getAnnotationDataTest() throws Exception {
         "getElementalType",
         "getEnclosingType",
         "lookupType",
+        "isSealed", // tested with getPermittedSubsclasses
         "resolveField",
         "$jacocoInit"
     };