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 * Copyright (c) 2015, 2020, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * 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
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package org.graalvm.compiler.hotspot.meta;

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

import org.graalvm.compiler.core.common.type.StampPair;
import org.graalvm.compiler.nodes.ConstantNode;
import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.extended.GuardingNode;
import org.graalvm.compiler.nodes.graphbuilderconf.GraphBuilderContext;
import org.graalvm.compiler.nodes.graphbuilderconf.GraphBuilderTool;
import org.graalvm.compiler.nodes.graphbuilderconf.InlineInvokePlugin;
import org.graalvm.compiler.nodes.graphbuilderconf.NodePlugin;
import org.graalvm.compiler.nodes.graphbuilderconf.TypePlugin;
import org.graalvm.compiler.nodes.util.ConstantFoldUtil;
import org.graalvm.compiler.word.Word;
import org.graalvm.compiler.word.WordOperationPlugin;

import jdk.vm.ci.meta.JavaConstant;
import jdk.vm.ci.meta.JavaKind;
import jdk.vm.ci.meta.JavaType;
import jdk.vm.ci.meta.JavaTypeProfile;
import jdk.vm.ci.meta.ResolvedJavaField;
import jdk.vm.ci.meta.ResolvedJavaMethod;
import jdk.vm.ci.meta.ResolvedJavaType;

This plugin does HotSpot-specific customization of bytecode parsing:

Word-type rewriting for intrinsic functions (snippets and method substitutions), by forwarding to the WordOperationPlugin. Note that we forward the NodePlugin and TypePlugin methods, but not the InlineInvokePlugin methods implemented by WordOperationPlugin. The latter is not necessary because HotSpot only uses the Word type in methods that are force-inlined, i.e., there are never non-inlined invokes that involve the Word type.
Constant folding of field loads.

/**
 * This plugin does HotSpot-specific customization of bytecode parsing:
 * <ul>
 * <li>{@link Word}-type rewriting for {@link GraphBuilderContext#parsingIntrinsic intrinsic}
 * functions (snippets and method substitutions), by forwarding to the {@link WordOperationPlugin}.
 * Note that we forward the {@link NodePlugin} and {@link TypePlugin} methods, but not the
 * {@link InlineInvokePlugin} methods implemented by {@link WordOperationPlugin}. The latter is not
 * necessary because HotSpot only uses the {@link Word} type in methods that are force-inlined,
 * i.e., there are never non-inlined invokes that involve the {@link Word} type.</li>
 * <li>Constant folding of field loads.</li>
 * </ul>
 */
public final class HotSpotNodePlugin implements NodePlugin, TypePlugin {

    protected final WordOperationPlugin wordOperationPlugin;

    public HotSpotNodePlugin(WordOperationPlugin wordOperationPlugin) {
        this.wordOperationPlugin = wordOperationPlugin;
    }

    @Override
    public boolean canChangeStackKind(GraphBuilderContext b) {
        if (b.parsingIntrinsic()) {
            return wordOperationPlugin.canChangeStackKind(b);
        }
        return false;
    }

    @Override
    public StampPair interceptType(GraphBuilderTool b, JavaType declaredType, boolean nonNull) {
        if (b.parsingIntrinsic()) {
            return wordOperationPlugin.interceptType(b, declaredType, nonNull);
        }
        return null;
    }

    @Override
    public boolean handleInvoke(GraphBuilderContext b, ResolvedJavaMethod method, ValueNode[] args) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleInvoke(b, method, args)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleLoadField(GraphBuilderContext b, ValueNode object, ResolvedJavaField field) {
        if (!ImmutableCode.getValue(b.getOptions()) || b.parsingIntrinsic()) {
            if (object.isConstant()) {
                JavaConstant asJavaConstant = object.asJavaConstant();
                if (tryReadField(b, field, asJavaConstant)) {
                    return true;
                }
            }
        }
        if (b.parsingIntrinsic() && wordOperationPlugin.handleLoadField(b, object, field)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleLoadStaticField(GraphBuilderContext b, ResolvedJavaField field) {
        if (!ImmutableCode.getValue(b.getOptions()) || b.parsingIntrinsic()) {
            if (tryReadField(b, field, null)) {
                return true;
            }
        }
        if (b.parsingIntrinsic() && wordOperationPlugin.handleLoadStaticField(b, field)) {
            return true;
        }
        return false;
    }

    private static boolean tryReadField(GraphBuilderContext b, ResolvedJavaField field, JavaConstant object) {
        return tryConstantFold(b, field, object);
    }

    private static boolean tryConstantFold(GraphBuilderContext b, ResolvedJavaField field, JavaConstant object) {
        ConstantNode result = ConstantFoldUtil.tryConstantFold(b.getConstantFieldProvider(), b.getConstantReflection(), b.getMetaAccess(), field, object, b.getOptions());
        if (result != null) {
            result = b.getGraph().unique(result);
            b.push(field.getJavaKind(), result);
            return true;
        }
        return false;
    }

    @Override
    public boolean handleStoreField(GraphBuilderContext b, ValueNode object, ResolvedJavaField field, ValueNode value) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleStoreField(b, object, field, value)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleStoreStaticField(GraphBuilderContext b, ResolvedJavaField field, ValueNode value) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleStoreStaticField(b, field, value)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleLoadIndexed(GraphBuilderContext b, ValueNode array, ValueNode index, GuardingNode boundsCheck, JavaKind elementKind) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleLoadIndexed(b, array, index, boundsCheck, elementKind)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleStoreIndexed(GraphBuilderContext b, ValueNode array, ValueNode index, GuardingNode boundsCheck, GuardingNode storeCheck, JavaKind elementKind, ValueNode value) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleStoreIndexed(b, array, index, boundsCheck, storeCheck, elementKind, value)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleCheckCast(GraphBuilderContext b, ValueNode object, ResolvedJavaType type, JavaTypeProfile profile) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleCheckCast(b, object, type, profile)) {
            return true;
        }
        return false;
    }

    @Override
    public boolean handleInstanceOf(GraphBuilderContext b, ValueNode object, ResolvedJavaType type, JavaTypeProfile profile) {
        if (b.parsingIntrinsic() && wordOperationPlugin.handleInstanceOf(b, object, type, profile)) {
            return true;
        }
        return false;
    }
}