/*

 * Copyright (c) 2016, 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 org.graalvm.compiler.hotspot.meta;

import static org.graalvm.compiler.core.common.GraalOptions.ImmutableCode;

import static org.graalvm.compiler.hotspot.meta.HotSpotGraalConstantFieldProvider.ImmutableCodeLazy.isCalledForSnippets;

import static org.graalvm.compiler.hotspot.stubs.SnippetStub.SnippetGraphUnderConstruction;

import java.util.ArrayList;

import java.util.List;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.hotspot.GraalHotSpotVMConfig;

import org.graalvm.compiler.options.StableOptionValue;

import org.graalvm.compiler.replacements.ReplacementsImpl;

import org.graalvm.compiler.replacements.SnippetCounter;

import org.graalvm.compiler.replacements.SnippetTemplate;

import org.graalvm.compiler.replacements.SnippetTemplate.Arguments;

import jdk.vm.ci.meta.JavaConstant;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaField;

import jdk.vm.ci.meta.ResolvedJavaMethod;

import jdk.vm.ci.meta.ResolvedJavaType;

import jdk.vm.ci.runtime.JVMCI;

/**

 * Extends {@link HotSpotConstantFieldProvider} to override the implementation of

 * {@link #readConstantField} with Graal specific semantics.

 */

public class HotSpotGraalConstantFieldProvider extends HotSpotConstantFieldProvider {

    public HotSpotGraalConstantFieldProvider(GraalHotSpotVMConfig config, MetaAccessProvider metaAccess) {

        super(config, metaAccess);

        this.metaAccess = metaAccess;

    }

    @Override

    public <T> T readConstantField(ResolvedJavaField field, ConstantFieldTool<T> tool) {

        assert !ImmutableCode.getValue() || isCalledForSnippets(metaAccess) || SnippetGraphUnderConstruction.get() != null ||

                        FieldReadEnabledInImmutableCode.get() == Boolean.TRUE : tool.getReceiver();

        if (!field.isStatic() && field.getName().equals("value")) {

            if (getStableOptionValueType().isInstance(tool.getReceiver())) {

                JavaConstant ret = tool.readValue();

                return tool.foldConstant(ret);

            }

        }

        return super.readConstantField(field, tool);

    }

    /**

     * In AOT mode, some fields should never be embedded even for snippets/replacements.

     */

    @Override

    protected boolean isStaticFieldConstant(ResolvedJavaField field) {

        return super.isStaticFieldConstant(field) && (!ImmutableCode.getValue() || ImmutableCodeLazy.isEmbeddable(field));

    }

    @Override

    protected boolean isFinalFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {

        if (super.isFinalFieldValueConstant(field, value, tool)) {

            return true;

        }

        if (!field.isStatic()) {

            JavaConstant receiver = tool.getReceiver();

            if (getSnippetCounterType().isInstance(receiver) || getNodeClassType().isInstance(receiver)) {

                return true;

            }

        }

        return false;

    }

    @Override

    protected boolean isStableFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {

        if (super.isStableFieldValueConstant(field, value, tool)) {

            return true;

        }

        if (!field.isStatic()) {

            JavaConstant receiver = tool.getReceiver();

            if (getHotSpotVMConfigType().isInstance(receiver)) {

                return true;

            }

        }

        return false;

    }

    private final MetaAccessProvider metaAccess;

    private ResolvedJavaType cachedStableOptionValueType;

    private ResolvedJavaType cachedHotSpotVMConfigType;

    private ResolvedJavaType cachedSnippetCounterType;

    private ResolvedJavaType cachedNodeClassType;

    private ResolvedJavaType getStableOptionValueType() {

        if (cachedStableOptionValueType == null) {

            cachedStableOptionValueType = metaAccess.lookupJavaType(StableOptionValue.class);

        }

        return cachedStableOptionValueType;

    }

    private ResolvedJavaType getHotSpotVMConfigType() {

        if (cachedHotSpotVMConfigType == null) {

            cachedHotSpotVMConfigType = metaAccess.lookupJavaType(GraalHotSpotVMConfig.class);

        }

        return cachedHotSpotVMConfigType;

    }

    private ResolvedJavaType getSnippetCounterType() {

        if (cachedSnippetCounterType == null) {

            cachedSnippetCounterType = metaAccess.lookupJavaType(SnippetCounter.class);

        }

        return cachedSnippetCounterType;

    }

    private ResolvedJavaType getNodeClassType() {

        if (cachedNodeClassType == null) {

            cachedNodeClassType = metaAccess.lookupJavaType(NodeClass.class);

        }

        return cachedNodeClassType;

    }

    @SuppressWarnings("all")

    private static boolean assertionsEnabled() {

        boolean enabled = false;

        assert enabled = true;

        return enabled;

    }

    public static final ThreadLocal<Boolean> FieldReadEnabledInImmutableCode = assertionsEnabled() ? new ThreadLocal<>() : null;

    /**

     * Compares two {@link StackTraceElement}s for equality, ignoring differences in

     * {@linkplain StackTraceElement#getLineNumber() line number}.

     */

    private static boolean equalsIgnoringLine(StackTraceElement left, StackTraceElement right) {

        return left.getClassName().equals(right.getClassName()) && left.getMethodName().equals(right.getMethodName()) && left.getFileName().equals(right.getFileName());

    }

    /**

     * Separate out the static initialization of {@linkplain #isEmbeddable(ResolvedJavaField)

     * embeddable fields} to eliminate cycles between clinit and other locks that could lead to

     * deadlock. Static code that doesn't call back into type or field machinery is probably ok but

     * anything else should be made lazy.

     */

    static class ImmutableCodeLazy {

        /**

         * If the compiler is configured for AOT mode, {@link #readConstantField} should be only

         * called for snippets or replacements.

         */

        static boolean isCalledForSnippets(MetaAccessProvider metaAccess) {

            assert ImmutableCode.getValue();

            ResolvedJavaMethod makeGraphMethod = null;

            ResolvedJavaMethod initMethod = null;

            try {

                Class<?> rjm = ResolvedJavaMethod.class;

                makeGraphMethod = metaAccess.lookupJavaMethod(ReplacementsImpl.class.getDeclaredMethod("makeGraph", rjm, Object[].class, rjm));

                initMethod = metaAccess.lookupJavaMethod(SnippetTemplate.AbstractTemplates.class.getDeclaredMethod("template", Arguments.class));

            } catch (NoSuchMethodException | SecurityException e) {

                throw new GraalError(e);

            }

            StackTraceElement makeGraphSTE = makeGraphMethod.asStackTraceElement(0);

            StackTraceElement initSTE = initMethod.asStackTraceElement(0);

            StackTraceElement[] stackTrace = new Exception().getStackTrace();

            for (StackTraceElement element : stackTrace) {

                // Ignoring line numbers should not weaken this check too much while at

                // the same time making it more robust against source code changes

                if (equalsIgnoringLine(makeGraphSTE, element) || equalsIgnoringLine(initSTE, element)) {

                    return true;

                }

            }

            return false;

        }

        /**

         * Determine if it's ok to embed the value of {@code field}.

         */

        static boolean isEmbeddable(ResolvedJavaField field) {

            assert ImmutableCode.getValue();

            return !embeddableFields.contains(field);

        }

        private static final List<ResolvedJavaField> embeddableFields = new ArrayList<>();

        static {

            try {

                MetaAccessProvider metaAccess = JVMCI.getRuntime().getHostJVMCIBackend().getMetaAccess();

                embeddableFields.add(metaAccess.lookupJavaField(Boolean.class.getDeclaredField("TRUE")));

                embeddableFields.add(metaAccess.lookupJavaField(Boolean.class.getDeclaredField("FALSE")));

                Class<?> characterCacheClass = Character.class.getDeclaredClasses()[0];

                assert "java.lang.Character$CharacterCache".equals(characterCacheClass.getName());

                embeddableFields.add(metaAccess.lookupJavaField(characterCacheClass.getDeclaredField("cache")));

                Class<?> byteCacheClass = Byte.class.getDeclaredClasses()[0];

                assert "java.lang.Byte$ByteCache".equals(byteCacheClass.getName());

                embeddableFields.add(metaAccess.lookupJavaField(byteCacheClass.getDeclaredField("cache")));

                Class<?> shortCacheClass = Short.class.getDeclaredClasses()[0];

                assert "java.lang.Short$ShortCache".equals(shortCacheClass.getName());

                embeddableFields.add(metaAccess.lookupJavaField(shortCacheClass.getDeclaredField("cache")));

                Class<?> integerCacheClass = Integer.class.getDeclaredClasses()[0];

                assert "java.lang.Integer$IntegerCache".equals(integerCacheClass.getName());

                embeddableFields.add(metaAccess.lookupJavaField(integerCacheClass.getDeclaredField("cache")));

                Class<?> longCacheClass = Long.class.getDeclaredClasses()[0];

                assert "java.lang.Long$LongCache".equals(longCacheClass.getName());

                embeddableFields.add(metaAccess.lookupJavaField(longCacheClass.getDeclaredField("cache")));

                embeddableFields.add(metaAccess.lookupJavaField(Throwable.class.getDeclaredField("UNASSIGNED_STACK")));

                embeddableFields.add(metaAccess.lookupJavaField(Throwable.class.getDeclaredField("SUPPRESSED_SENTINEL")));

            } catch (SecurityException | NoSuchFieldException e) {

                throw new GraalError(e);

            }

        }

    }

}