src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotResolvedObjectTypeImpl.java
changeset 47216 71c04702a3d5
parent 45626 c4ea64135530
child 47668 fc4cfca10556
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotResolvedObjectTypeImpl.java	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,937 @@
+/*
+ * Copyright (c) 2011, 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package jdk.vm.ci.hotspot;
+
+import static java.util.Objects.requireNonNull;
+import static jdk.vm.ci.hotspot.CompilerToVM.compilerToVM;
+import static jdk.vm.ci.hotspot.HotSpotConstantPool.isSignaturePolymorphicHolder;
+import static jdk.vm.ci.hotspot.HotSpotJVMCIRuntime.runtime;
+import static jdk.vm.ci.hotspot.HotSpotModifiers.jvmClassModifiers;
+import static jdk.vm.ci.hotspot.HotSpotVMConfig.config;
+import static jdk.vm.ci.hotspot.UnsafeAccess.UNSAFE;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Array;
+import java.lang.reflect.Constructor;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.nio.ByteOrder;
+import java.util.HashMap;
+
+import jdk.vm.ci.common.JVMCIError;
+import jdk.vm.ci.meta.Assumptions.AssumptionResult;
+import jdk.vm.ci.meta.Assumptions.ConcreteMethod;
+import jdk.vm.ci.meta.Assumptions.ConcreteSubtype;
+import jdk.vm.ci.meta.Assumptions.LeafType;
+import jdk.vm.ci.meta.Assumptions.NoFinalizableSubclass;
+import jdk.vm.ci.meta.Constant;
+import jdk.vm.ci.meta.JavaConstant;
+import jdk.vm.ci.meta.JavaKind;
+import jdk.vm.ci.meta.JavaType;
+import jdk.vm.ci.meta.ResolvedJavaField;
+import jdk.vm.ci.meta.ResolvedJavaMethod;
+import jdk.vm.ci.meta.ResolvedJavaType;
+
+/**
+ * Implementation of {@link JavaType} for resolved non-primitive HotSpot classes.
+ */
+final class HotSpotResolvedObjectTypeImpl extends HotSpotResolvedJavaType implements HotSpotResolvedObjectType, MetaspaceWrapperObject {
+
+    private static final HotSpotResolvedJavaField[] NO_FIELDS = new HotSpotResolvedJavaField[0];
+    private static final int METHOD_CACHE_ARRAY_CAPACITY = 8;
+
+    /**
+     * The Java class this type represents.
+     */
+    private final Class<?> javaClass;
+    private HotSpotResolvedJavaMethodImpl[] methodCacheArray;
+    private HashMap<Long, HotSpotResolvedJavaMethodImpl> methodCacheHashMap;
+    private HotSpotResolvedJavaField[] instanceFields;
+    private HotSpotResolvedObjectTypeImpl[] interfaces;
+    private HotSpotConstantPool constantPool;
+    final HotSpotJVMCIMetaAccessContext context;
+    private HotSpotResolvedObjectType arrayOfType;
+
+    /**
+     * Gets the JVMCI mirror for a {@link Class} object.
+     *
+     * @return the {@link HotSpotResolvedJavaType} corresponding to {@code javaClass}
+     */
+    static HotSpotResolvedObjectTypeImpl fromObjectClass(Class<?> javaClass) {
+        return (HotSpotResolvedObjectTypeImpl) runtime().fromClass(javaClass);
+    }
+
+    /**
+     * Gets the JVMCI mirror from a HotSpot type. Since {@link Class} is already a proxy for the
+     * underlying Klass*, it is used instead of the raw Klass*.
+     *
+     * Called from the VM.
+     *
+     * @param javaClass a {@link Class} object
+     * @return the {@link ResolvedJavaType} corresponding to {@code javaClass}
+     */
+    @SuppressWarnings("unused")
+    private static HotSpotResolvedObjectTypeImpl fromMetaspace(Class<?> javaClass) {
+        return fromObjectClass(javaClass);
+    }
+
+    /**
+     * Creates the JVMCI mirror for a {@link Class} object.
+     *
+     * <p>
+     * <b>NOTE</b>: Creating an instance of this class does not install the mirror for the
+     * {@link Class} type. Use {@link #fromObjectClass(Class)} or {@link #fromMetaspace(Class)}
+     * instead.
+     * </p>
+     *
+     * @param javaClass the Class to create the mirror for
+     * @param context
+     */
+    HotSpotResolvedObjectTypeImpl(Class<?> javaClass, HotSpotJVMCIMetaAccessContext context) {
+        super(getSignatureName(javaClass));
+        this.javaClass = javaClass;
+        this.context = context;
+        assert getName().charAt(0) != '[' || isArray() : getName();
+    }
+
+    /**
+     * Returns the name of this type as it would appear in a signature.
+     */
+    private static String getSignatureName(Class<?> javaClass) {
+        if (javaClass.isArray()) {
+            return javaClass.getName().replace('.', '/');
+        }
+        return "L" + javaClass.getName().replace('.', '/') + ";";
+    }
+
+    /**
+     * Gets the metaspace Klass for this type.
+     */
+    long getMetaspaceKlass() {
+        if (HotSpotJVMCIRuntime.getHostWordKind() == JavaKind.Long) {
+            return UNSAFE.getLong(javaClass, config().klassOffset);
+        }
+        return UNSAFE.getInt(javaClass, config().klassOffset) & 0xFFFFFFFFL;
+    }
+
+    @Override
+    public long getMetaspacePointer() {
+        return getMetaspaceKlass();
+    }
+
+    /**
+     * The Klass* for this object is kept alive by the direct reference to {@link #javaClass} so no
+     * extra work is required.
+     */
+    @Override
+    public boolean isRegistered() {
+        return true;
+    }
+
+    @Override
+    public int getModifiers() {
+        if (isArray()) {
+            return (getElementalType().getModifiers() & (Modifier.PUBLIC | Modifier.PRIVATE | Modifier.PROTECTED)) | Modifier.FINAL | Modifier.ABSTRACT;
+        } else {
+            return getAccessFlags() & jvmClassModifiers();
+        }
+    }
+
+    public int getAccessFlags() {
+        HotSpotVMConfig config = config();
+        return UNSAFE.getInt(getMetaspaceKlass() + config.klassAccessFlagsOffset);
+    }
+
+    @Override
+    public HotSpotResolvedObjectType getArrayClass() {
+        if (arrayOfType == null) {
+            arrayOfType = fromObjectClass(Array.newInstance(mirror(), 0).getClass());
+        }
+        return arrayOfType;
+    }
+
+    @Override
+    public ResolvedJavaType getComponentType() {
+        Class<?> javaComponentType = mirror().getComponentType();
+        return javaComponentType == null ? null : runtime().fromClass(javaComponentType);
+    }
+
+    @Override
+    public AssumptionResult<ResolvedJavaType> findLeafConcreteSubtype() {
+        if (isLeaf()) {
+            // No assumptions are required.
+            return new AssumptionResult<>(this);
+        }
+        HotSpotVMConfig config = config();
+        if (isArray()) {
+            ResolvedJavaType elementalType = getElementalType();
+            AssumptionResult<ResolvedJavaType> elementType = elementalType.findLeafConcreteSubtype();
+            if (elementType != null && elementType.getResult().equals(elementalType)) {
+                /*
+                 * If the elementType is leaf then the array is leaf under the same assumptions but
+                 * only if the element type is exactly the leaf type. The element type can be
+                 * abstract even if there is only one implementor of the abstract type.
+                 */
+                AssumptionResult<ResolvedJavaType> result = new AssumptionResult<>(this);
+                result.add(elementType);
+                return result;
+            }
+            return null;
+        } else if (isInterface()) {
+            HotSpotResolvedObjectTypeImpl implementor = getSingleImplementor();
+            /*
+             * If the implementor field contains itself that indicates that the interface has more
+             * than one implementors (see: InstanceKlass::add_implementor).
+             */
+            if (implementor == null || implementor.equals(this)) {
+                return null;
+            }
+
+            assert !implementor.isInterface();
+            if (implementor.isAbstract() || !implementor.isLeafClass()) {
+                AssumptionResult<ResolvedJavaType> leafConcreteSubtype = implementor.findLeafConcreteSubtype();
+                if (leafConcreteSubtype != null) {
+                    assert !leafConcreteSubtype.getResult().equals(implementor);
+                    AssumptionResult<ResolvedJavaType> newResult = new AssumptionResult<>(leafConcreteSubtype.getResult(), new ConcreteSubtype(this, implementor));
+                    // Accumulate leaf assumptions and return the combined result.
+                    newResult.add(leafConcreteSubtype);
+                    return newResult;
+                }
+                return null;
+            }
+            return concreteSubtype(implementor);
+        } else {
+            HotSpotResolvedObjectTypeImpl type = this;
+            while (type.isAbstract()) {
+                HotSpotResolvedObjectTypeImpl subklass = type.getSubklass();
+                if (subklass == null || UNSAFE.getAddress(subklass.getMetaspaceKlass() + config.nextSiblingOffset) != 0) {
+                    return null;
+                }
+                type = subklass;
+            }
+            if (type.isAbstract() || type.isInterface() || !type.isLeafClass()) {
+                return null;
+            }
+            if (this.isAbstract()) {
+                return concreteSubtype(type);
+            } else {
+                assert this.equals(type);
+                return new AssumptionResult<>(type, new LeafType(type));
+            }
+        }
+    }
+
+    private AssumptionResult<ResolvedJavaType> concreteSubtype(HotSpotResolvedObjectTypeImpl type) {
+        if (type.isLeaf()) {
+            return new AssumptionResult<>(type, new ConcreteSubtype(this, type));
+        } else {
+            return new AssumptionResult<>(type, new LeafType(type), new ConcreteSubtype(this, type));
+        }
+    }
+
+    /**
+     * Returns if type {@code type} is a leaf class. This is the case if the
+     * {@code Klass::_subklass} field of the underlying class is zero.
+     *
+     * @return true if the type is a leaf class
+     */
+    private boolean isLeafClass() {
+        return UNSAFE.getLong(this.getMetaspaceKlass() + config().subklassOffset) == 0;
+    }
+
+    /**
+     * Returns the {@code Klass::_subklass} field of the underlying metaspace klass for the given
+     * type {@code type}.
+     *
+     * @return value of the subklass field as metaspace klass pointer
+     */
+    private HotSpotResolvedObjectTypeImpl getSubklass() {
+        return compilerToVM().getResolvedJavaType(this, config().subklassOffset, false);
+    }
+
+    @Override
+    public HotSpotResolvedObjectTypeImpl getSuperclass() {
+        Class<?> javaSuperclass = mirror().getSuperclass();
+        return javaSuperclass == null ? null : fromObjectClass(javaSuperclass);
+    }
+
+    @Override
+    public HotSpotResolvedObjectTypeImpl[] getInterfaces() {
+        if (interfaces == null) {
+            Class<?>[] javaInterfaces = mirror().getInterfaces();
+            HotSpotResolvedObjectTypeImpl[] result = new HotSpotResolvedObjectTypeImpl[javaInterfaces.length];
+            for (int i = 0; i < javaInterfaces.length; i++) {
+                result[i] = fromObjectClass(javaInterfaces[i]);
+            }
+            interfaces = result;
+        }
+        return interfaces;
+    }
+
+    @Override
+    public HotSpotResolvedObjectTypeImpl getSingleImplementor() {
+        if (!isInterface()) {
+            throw new JVMCIError("Cannot call getSingleImplementor() on a non-interface type: %s", this);
+        }
+        return compilerToVM().getImplementor(this);
+    }
+
+    public HotSpotResolvedObjectTypeImpl getSupertype() {
+        if (isArray()) {
+            ResolvedJavaType componentType = getComponentType();
+            if (mirror() == Object[].class || componentType.isPrimitive()) {
+                return fromObjectClass(Object.class);
+            }
+            return (HotSpotResolvedObjectTypeImpl) ((HotSpotResolvedObjectTypeImpl) componentType).getSupertype().getArrayClass();
+        }
+        if (isInterface()) {
+            return fromObjectClass(Object.class);
+        }
+        return getSuperclass();
+    }
+
+    @Override
+    public HotSpotResolvedObjectType findLeastCommonAncestor(ResolvedJavaType otherType) {
+        if (otherType.isPrimitive()) {
+            return null;
+        } else {
+            HotSpotResolvedObjectTypeImpl t1 = this;
+            HotSpotResolvedObjectTypeImpl t2 = (HotSpotResolvedObjectTypeImpl) otherType;
+            while (true) {
+                if (t1.isAssignableFrom(t2)) {
+                    return t1;
+                }
+                if (t2.isAssignableFrom(t1)) {
+                    return t2;
+                }
+                t1 = t1.getSupertype();
+                t2 = t2.getSupertype();
+            }
+        }
+    }
+
+    @Override
+    public AssumptionResult<Boolean> hasFinalizableSubclass() {
+        assert !isArray();
+        if (!compilerToVM().hasFinalizableSubclass(this)) {
+            return new AssumptionResult<>(false, new NoFinalizableSubclass(this));
+        }
+        return new AssumptionResult<>(true);
+    }
+
+    @Override
+    public boolean hasFinalizer() {
+        return (getAccessFlags() & config().jvmAccHasFinalizer) != 0;
+    }
+
+    @Override
+    public boolean isPrimitive() {
+        return false;
+    }
+
+    @Override
+    public boolean isArray() {
+        return mirror().isArray();
+    }
+
+    @Override
+    public boolean isInitialized() {
+        return isArray() ? true : getInitState() == config().instanceKlassStateFullyInitialized;
+    }
+
+    @Override
+    public boolean isLinked() {
+        return isArray() ? true : getInitState() >= config().instanceKlassStateLinked;
+    }
+
+    /**
+     * Returns the value of the state field {@code InstanceKlass::_init_state} of the metaspace
+     * klass.
+     *
+     * @return state field value of this type
+     */
+    private int getInitState() {
+        assert !isArray() : "_init_state only exists in InstanceKlass";
+        return UNSAFE.getByte(getMetaspaceKlass() + config().instanceKlassInitStateOffset) & 0xFF;
+    }
+
+    @Override
+    public void initialize() {
+        if (!isInitialized()) {
+            UNSAFE.ensureClassInitialized(mirror());
+            assert isInitialized();
+        }
+    }
+
+    @Override
+    public boolean isInstance(JavaConstant obj) {
+        if (obj.getJavaKind() == JavaKind.Object && !obj.isNull()) {
+            return mirror().isInstance(((HotSpotObjectConstantImpl) obj).object());
+        }
+        return false;
+    }
+
+    @Override
+    public boolean isInstanceClass() {
+        return !isArray() && !isInterface();
+    }
+
+    @Override
+    public boolean isInterface() {
+        return mirror().isInterface();
+    }
+
+    @Override
+    public boolean isAssignableFrom(ResolvedJavaType other) {
+        assert other != null;
+        if (other instanceof HotSpotResolvedObjectTypeImpl) {
+            HotSpotResolvedObjectTypeImpl otherType = (HotSpotResolvedObjectTypeImpl) other;
+            return mirror().isAssignableFrom(otherType.mirror());
+        }
+        return false;
+    }
+
+    @Override
+    public ResolvedJavaType getHostClass() {
+        if (isArray()) {
+            return null;
+        }
+        return compilerToVM().getHostClass(this);
+    }
+
+    @Override
+    public boolean isJavaLangObject() {
+        return javaClass.equals(Object.class);
+    }
+
+    @Override
+    public JavaKind getJavaKind() {
+        return JavaKind.Object;
+    }
+
+    @Override
+    public ResolvedJavaMethod resolveMethod(ResolvedJavaMethod method, ResolvedJavaType callerType) {
+        assert !callerType.isArray();
+        if (isInterface()) {
+            // Methods can only be resolved against concrete types
+            return null;
+        }
+        if (method.isConcrete() && method.getDeclaringClass().equals(this) && method.isPublic() && !isSignaturePolymorphicHolder(method.getDeclaringClass())) {
+            return method;
+        }
+        if (!method.getDeclaringClass().isAssignableFrom(this)) {
+            return null;
+        }
+        HotSpotResolvedJavaMethodImpl hotSpotMethod = (HotSpotResolvedJavaMethodImpl) method;
+        HotSpotResolvedObjectTypeImpl hotSpotCallerType = (HotSpotResolvedObjectTypeImpl) callerType;
+        return compilerToVM().resolveMethod(this, hotSpotMethod, hotSpotCallerType);
+    }
+
+    public HotSpotConstantPool getConstantPool() {
+        if (constantPool == null || !isArray() && UNSAFE.getAddress(getMetaspaceKlass() + config().instanceKlassConstantsOffset) != constantPool.getMetaspaceConstantPool()) {
+            /*
+             * If the pointer to the ConstantPool has changed since this was last read refresh the
+             * HotSpotConstantPool wrapper object. This ensures that uses of the constant pool are
+             * operating on the latest one and that HotSpotResolvedJavaMethodImpls will be able to
+             * use the shared copy instead of creating their own instance.
+             */
+            constantPool = compilerToVM().getConstantPool(this);
+        }
+        return constantPool;
+    }
+
+    /**
+     * Gets the instance size of this type. If an instance of this type cannot be fast path
+     * allocated, then the returned value is negative (its absolute value gives the size). Must not
+     * be called if this is an array or interface type.
+     */
+    public int instanceSize() {
+        assert !isArray();
+        assert !isInterface();
+
+        HotSpotVMConfig config = config();
+        final int layoutHelper = layoutHelper();
+        assert layoutHelper > config.klassLayoutHelperNeutralValue : "must be instance";
+
+        // See: Klass::layout_helper_size_in_bytes
+        int size = layoutHelper & ~config.klassLayoutHelperInstanceSlowPathBit;
+
+        // See: Klass::layout_helper_needs_slow_path
+        boolean needsSlowPath = (layoutHelper & config.klassLayoutHelperInstanceSlowPathBit) != 0;
+
+        return needsSlowPath ? -size : size;
+    }
+
+    public int layoutHelper() {
+        HotSpotVMConfig config = config();
+        return UNSAFE.getInt(getMetaspaceKlass() + config.klassLayoutHelperOffset);
+    }
+
+    @Override
+    public long getFingerprint() {
+        return compilerToVM().getFingerprint(getMetaspaceKlass());
+    }
+
+    synchronized HotSpotResolvedJavaMethod createMethod(long metaspaceMethod) {
+        // Maintain cache as array.
+        if (methodCacheArray == null) {
+            methodCacheArray = new HotSpotResolvedJavaMethodImpl[METHOD_CACHE_ARRAY_CAPACITY];
+        }
+
+        int i = 0;
+        for (; i < methodCacheArray.length; ++i) {
+            HotSpotResolvedJavaMethodImpl curMethod = methodCacheArray[i];
+            if (curMethod == null) {
+                HotSpotResolvedJavaMethodImpl newMethod = new HotSpotResolvedJavaMethodImpl(this, metaspaceMethod);
+                methodCacheArray[i] = newMethod;
+                context.add(newMethod);
+                return newMethod;
+            } else if (curMethod.getMetaspacePointer() == metaspaceMethod) {
+                return curMethod;
+            }
+        }
+
+        // Fall-back to hash table.
+        if (methodCacheHashMap == null) {
+            methodCacheHashMap = new HashMap<>();
+        }
+
+        HotSpotResolvedJavaMethodImpl lookupResult = methodCacheHashMap.get(metaspaceMethod);
+        if (lookupResult == null) {
+            HotSpotResolvedJavaMethodImpl newMethod = new HotSpotResolvedJavaMethodImpl(this, metaspaceMethod);
+            methodCacheHashMap.put(metaspaceMethod, newMethod);
+            context.add(lookupResult);
+            return newMethod;
+        } else {
+            return lookupResult;
+        }
+    }
+
+    public int getVtableLength() {
+        HotSpotVMConfig config = config();
+        if (isInterface() || isArray()) {
+            /* Everything has the core vtable of java.lang.Object */
+            return config.baseVtableLength();
+        }
+        int result = UNSAFE.getInt(getMetaspaceKlass() + config.klassVtableLengthOffset) / (config.vtableEntrySize / config.heapWordSize);
+        assert result >= config.baseVtableLength() : UNSAFE.getInt(getMetaspaceKlass() + config.klassVtableLengthOffset) + " " + config.vtableEntrySize;
+        return result;
+    }
+
+    synchronized HotSpotResolvedJavaField createField(JavaType type, long offset, int rawFlags, int index) {
+        return new HotSpotResolvedJavaFieldImpl(this, type, offset, rawFlags, index);
+    }
+
+    @Override
+    public AssumptionResult<ResolvedJavaMethod> findUniqueConcreteMethod(ResolvedJavaMethod method) {
+        HotSpotResolvedJavaMethod hmethod = (HotSpotResolvedJavaMethod) method;
+        HotSpotResolvedObjectType declaredHolder = hmethod.getDeclaringClass();
+        /*
+         * Sometimes the receiver type in the graph hasn't stabilized to a subtype of declared
+         * holder, usually because of phis, so make sure that the type is related to the declared
+         * type before using it for lookup. Unlinked types should also be ignored because we can't
+         * resolve the proper method to invoke. Generally unlinked types in invokes should result in
+         * a deopt instead since they can't really be used if they aren't linked yet.
+         */
+        if (!declaredHolder.isAssignableFrom(this) || this.isArray() || this.equals(declaredHolder) || !isLinked() || isInterface()) {
+            ResolvedJavaMethod result = hmethod.uniqueConcreteMethod(declaredHolder);
+            if (result != null) {
+                return new AssumptionResult<>(result, new ConcreteMethod(method, declaredHolder, result));
+            }
+            return null;
+        }
+        /*
+         * The holder may be a subtype of the declaredHolder so make sure to resolve the method to
+         * the correct method for the subtype.
+         */
+        HotSpotResolvedJavaMethod resolvedMethod = (HotSpotResolvedJavaMethod) resolveMethod(hmethod, this);
+        if (resolvedMethod == null) {
+            // The type isn't known to implement the method.
+            return null;
+        }
+
+        ResolvedJavaMethod result = resolvedMethod.uniqueConcreteMethod(this);
+        if (result != null) {
+            return new AssumptionResult<>(result, new ConcreteMethod(method, this, result));
+        }
+        return null;
+    }
+
+    FieldInfo createFieldInfo(int index) {
+        return new FieldInfo(index);
+    }
+
+    /**
+     * This class represents the field information for one field contained in the fields array of an
+     * {@code InstanceKlass}. The implementation is similar to the native {@code FieldInfo} class.
+     */
+    class FieldInfo {
+        /**
+         * Native pointer into the array of Java shorts.
+         */
+        private final long metaspaceData;
+
+        /**
+         * Creates a field info for the field in the fields array at index {@code index}.
+         *
+         * @param index index to the fields array
+         */
+        FieldInfo(int index) {
+            HotSpotVMConfig config = config();
+            // Get Klass::_fields
+            final long metaspaceFields = UNSAFE.getAddress(getMetaspaceKlass() + config.instanceKlassFieldsOffset);
+            assert config.fieldInfoFieldSlots == 6 : "revisit the field parsing code";
+            int offset = config.fieldInfoFieldSlots * Short.BYTES * index;
+            metaspaceData = metaspaceFields + config.arrayU2DataOffset + offset;
+        }
+
+        private int getAccessFlags() {
+            return readFieldSlot(config().fieldInfoAccessFlagsOffset);
+        }
+
+        private int getNameIndex() {
+            return readFieldSlot(config().fieldInfoNameIndexOffset);
+        }
+
+        private int getSignatureIndex() {
+            return readFieldSlot(config().fieldInfoSignatureIndexOffset);
+        }
+
+        public int getOffset() {
+            HotSpotVMConfig config = config();
+            final int lowPacked = readFieldSlot(config.fieldInfoLowPackedOffset);
+            final int highPacked = readFieldSlot(config.fieldInfoHighPackedOffset);
+            final int offset = ((highPacked << Short.SIZE) | lowPacked) >> config.fieldInfoTagSize;
+            return offset;
+        }
+
+        /**
+         * Helper method to read an entry (slot) from the field array. Currently field info is laid
+         * on top an array of Java shorts.
+         */
+        private int readFieldSlot(int index) {
+            int offset = Short.BYTES * index;
+            return UNSAFE.getChar(metaspaceData + offset);
+        }
+
+        /**
+         * 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.
+         */
+        public String getName() {
+            final int nameIndex = getNameIndex();
+            return isInternal() ? config().symbolAt(nameIndex) : getConstantPool().lookupUtf8(nameIndex);
+        }
+
+        /**
+         * 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.
+         */
+        public String getSignature() {
+            final int signatureIndex = getSignatureIndex();
+            return isInternal() ? config().symbolAt(signatureIndex) : getConstantPool().lookupUtf8(signatureIndex);
+        }
+
+        public JavaType getType() {
+            String signature = getSignature();
+            return runtime().lookupType(signature, HotSpotResolvedObjectTypeImpl.this, false);
+        }
+
+        private boolean isInternal() {
+            return (getAccessFlags() & config().jvmAccFieldInternal) != 0;
+        }
+
+        public boolean isStatic() {
+            return Modifier.isStatic(getAccessFlags());
+        }
+
+        public boolean hasGenericSignature() {
+            return (getAccessFlags() & config().jvmAccFieldHasGenericSignature) != 0;
+        }
+    }
+
+    @Override
+    public ResolvedJavaField[] getInstanceFields(boolean includeSuperclasses) {
+        if (instanceFields == null) {
+            if (isArray() || isInterface()) {
+                instanceFields = NO_FIELDS;
+            } else {
+                HotSpotResolvedJavaField[] prepend = NO_FIELDS;
+                if (getSuperclass() != null) {
+                    prepend = (HotSpotResolvedJavaField[]) getSuperclass().getInstanceFields(true);
+                }
+                instanceFields = getFields(false, prepend);
+            }
+        }
+        if (!includeSuperclasses && getSuperclass() != null) {
+            int superClassFieldCount = getSuperclass().getInstanceFields(true).length;
+            if (superClassFieldCount == instanceFields.length) {
+                // This class does not have any instance fields of its own.
+                return NO_FIELDS;
+            } else if (superClassFieldCount != 0) {
+                HotSpotResolvedJavaField[] result = new HotSpotResolvedJavaField[instanceFields.length - superClassFieldCount];
+                System.arraycopy(instanceFields, superClassFieldCount, result, 0, result.length);
+                return result;
+            } else {
+                // The super classes of this class do not have any instance fields.
+            }
+        }
+        return instanceFields;
+    }
+
+    @Override
+    public ResolvedJavaField[] getStaticFields() {
+        if (isArray()) {
+            return new HotSpotResolvedJavaField[0];
+        } else {
+            return getFields(true, NO_FIELDS);
+        }
+    }
+
+    /**
+     * 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
+     */
+    private HotSpotResolvedJavaField[] getFields(boolean retrieveStaticFields, HotSpotResolvedJavaField[] prepend) {
+        HotSpotVMConfig config = config();
+        final long metaspaceFields = UNSAFE.getAddress(getMetaspaceKlass() + config.instanceKlassFieldsOffset);
+        int metaspaceFieldsLength = UNSAFE.getInt(metaspaceFields + config.arrayU1LengthOffset);
+        int resultCount = 0;
+        int index = 0;
+        for (int i = 0; i < metaspaceFieldsLength; i += config.fieldInfoFieldSlots, index++) {
+            FieldInfo field = new FieldInfo(index);
+            if (field.hasGenericSignature()) {
+                metaspaceFieldsLength--;
+            }
+
+            if (field.isStatic() == retrieveStaticFields) {
+                resultCount++;
+            }
+        }
+
+        if (resultCount == 0) {
+            return prepend;
+        }
+
+        int prependLength = prepend.length;
+        resultCount += prependLength;
+
+        HotSpotResolvedJavaField[] result = new HotSpotResolvedJavaField[resultCount];
+        if (prependLength != 0) {
+            System.arraycopy(prepend, 0, result, 0, prependLength);
+        }
+
+        int resultIndex = prependLength;
+        for (int i = 0; i < index; ++i) {
+            FieldInfo field = new FieldInfo(i);
+            if (field.isStatic() == retrieveStaticFields) {
+                int offset = field.getOffset();
+                HotSpotResolvedJavaField resolvedJavaField = createField(field.getType(), offset, field.getAccessFlags(), i);
+
+                // Make sure the result is sorted by offset.
+                int j;
+                for (j = resultIndex - 1; j >= prependLength && result[j].offset() > offset; j--) {
+                    result[j + 1] = result[j];
+                }
+                result[j + 1] = resolvedJavaField;
+                resultIndex++;
+            }
+        }
+
+        return result;
+    }
+
+    @Override
+    public Class<?> mirror() {
+        return javaClass;
+    }
+
+    @Override
+    public String getSourceFileName() {
+        HotSpotVMConfig config = config();
+        final int sourceFileNameIndex = UNSAFE.getChar(getMetaspaceKlass() + config.instanceKlassSourceFileNameIndexOffset);
+        if (sourceFileNameIndex == 0) {
+            return null;
+        }
+        return getConstantPool().lookupUtf8(sourceFileNameIndex);
+    }
+
+    @Override
+    public Annotation[] getAnnotations() {
+        return mirror().getAnnotations();
+    }
+
+    @Override
+    public Annotation[] getDeclaredAnnotations() {
+        return mirror().getDeclaredAnnotations();
+    }
+
+    @Override
+    public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
+        return mirror().getAnnotation(annotationClass);
+    }
+
+    /**
+     * Performs a fast-path check that this type is resolved in the context of a given accessing
+     * class. A negative result does not mean this type is not resolved with respect to
+     * {@code accessingClass}. That can only be determined by
+     * {@linkplain HotSpotJVMCIRuntime#lookupType(String, HotSpotResolvedObjectType, boolean)
+     * re-resolving} the type.
+     */
+    public boolean isDefinitelyResolvedWithRespectTo(ResolvedJavaType accessingClass) {
+        assert accessingClass != null;
+        ResolvedJavaType elementType = getElementalType();
+        if (elementType.isPrimitive()) {
+            // Primitive type resolution is context free.
+            return true;
+        }
+        if (elementType.getName().startsWith("Ljava/")) {
+            // Classes in a java.* package can only be defined by the
+            // boot or platform class loader.
+            return true;
+        }
+        ClassLoader thisCl = mirror().getClassLoader();
+        ClassLoader accessingClassCl = ((HotSpotResolvedObjectTypeImpl) accessingClass).mirror().getClassLoader();
+        return thisCl == accessingClassCl;
+    }
+
+    @Override
+    public ResolvedJavaType resolve(ResolvedJavaType accessingClass) {
+        if (isDefinitelyResolvedWithRespectTo(requireNonNull(accessingClass))) {
+            return this;
+        }
+        HotSpotResolvedObjectTypeImpl accessingType = (HotSpotResolvedObjectTypeImpl) accessingClass;
+        return (ResolvedJavaType) runtime().lookupType(getName(), accessingType, true);
+    }
+
+    /**
+     * Gets the metaspace Klass boxed in a {@link JavaConstant}.
+     */
+    public Constant klass() {
+        return HotSpotMetaspaceConstantImpl.forMetaspaceObject(this, false);
+    }
+
+    public boolean isPrimaryType() {
+        return config().secondarySuperCacheOffset != superCheckOffset();
+    }
+
+    public int superCheckOffset() {
+        HotSpotVMConfig config = config();
+        return UNSAFE.getInt(getMetaspaceKlass() + config.superCheckOffsetOffset);
+    }
+
+    public long prototypeMarkWord() {
+        HotSpotVMConfig config = config();
+        if (isArray()) {
+            return config.arrayPrototypeMarkWord();
+        } else {
+            return UNSAFE.getAddress(getMetaspaceKlass() + config.prototypeMarkWordOffset);
+        }
+    }
+
+    @Override
+    public ResolvedJavaField findInstanceFieldWithOffset(long offset, JavaKind expectedEntryKind) {
+        ResolvedJavaField[] declaredFields = getInstanceFields(true);
+        return findFieldWithOffset(offset, expectedEntryKind, declaredFields);
+    }
+
+    public ResolvedJavaField findStaticFieldWithOffset(long offset, JavaKind expectedEntryKind) {
+        ResolvedJavaField[] declaredFields = getStaticFields();
+        return findFieldWithOffset(offset, expectedEntryKind, declaredFields);
+    }
+
+    private static ResolvedJavaField findFieldWithOffset(long offset, JavaKind expectedEntryKind, ResolvedJavaField[] declaredFields) {
+        for (ResolvedJavaField field : declaredFields) {
+            HotSpotResolvedJavaField resolvedField = (HotSpotResolvedJavaField) field;
+            long resolvedFieldOffset = resolvedField.offset();
+            // @formatter:off
+            if (ByteOrder.nativeOrder() == ByteOrder.BIG_ENDIAN  &&
+                            expectedEntryKind.isPrimitive() &&
+                            !expectedEntryKind.equals(JavaKind.Void) &&
+                            resolvedField.getJavaKind().isPrimitive()) {
+                resolvedFieldOffset +=
+                                resolvedField.getJavaKind().getByteCount() -
+                                Math.min(resolvedField.getJavaKind().getByteCount(), 4 + expectedEntryKind.getByteCount());
+            }
+            if (resolvedFieldOffset == offset) {
+                return field;
+            }
+            // @formatter:on
+        }
+        return null;
+    }
+
+    @Override
+    public boolean isLocal() {
+        return mirror().isLocalClass();
+    }
+
+    @Override
+    public boolean isMember() {
+        return mirror().isMemberClass();
+    }
+
+    @Override
+    public HotSpotResolvedObjectTypeImpl getEnclosingType() {
+        final Class<?> encl = mirror().getEnclosingClass();
+        return encl == null ? null : fromObjectClass(encl);
+    }
+
+    @Override
+    public ResolvedJavaMethod[] getDeclaredConstructors() {
+        Constructor<?>[] constructors = mirror().getDeclaredConstructors();
+        ResolvedJavaMethod[] result = new ResolvedJavaMethod[constructors.length];
+        for (int i = 0; i < constructors.length; i++) {
+            result[i] = runtime().getHostJVMCIBackend().getMetaAccess().lookupJavaMethod(constructors[i]);
+            assert result[i].isConstructor();
+        }
+        return result;
+    }
+
+    @Override
+    public ResolvedJavaMethod[] getDeclaredMethods() {
+        Method[] methods = mirror().getDeclaredMethods();
+        ResolvedJavaMethod[] result = new ResolvedJavaMethod[methods.length];
+        for (int i = 0; i < methods.length; i++) {
+            result[i] = runtime().getHostJVMCIBackend().getMetaAccess().lookupJavaMethod(methods[i]);
+            assert !result[i].isConstructor();
+        }
+        return result;
+    }
+
+    public ResolvedJavaMethod getClassInitializer() {
+        return compilerToVM().getClassInitializer(this);
+    }
+
+    @Override
+    public String toString() {
+        return "HotSpotType<" + getName() + ", resolved>";
+    }
+
+    @Override
+    public boolean isCloneableWithAllocation() {
+        return (getAccessFlags() & config().jvmAccIsCloneableFast) != 0;
+    }
+}