/*

 * Copyright (c) 2009, 2014, 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.nodes.java;

import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_2;

import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_1;

import org.graalvm.compiler.core.common.type.StampFactory;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.spi.Canonicalizable;

import org.graalvm.compiler.graph.spi.CanonicalizerTool;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.FixedWithNextNode;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.spi.ArrayLengthProvider;

import org.graalvm.compiler.nodes.spi.Lowerable;

import org.graalvm.compiler.nodes.spi.LoweringTool;

import org.graalvm.compiler.nodes.spi.Virtualizable;

import org.graalvm.compiler.nodes.spi.VirtualizerTool;

import org.graalvm.compiler.nodes.util.GraphUtil;

import org.graalvm.compiler.nodes.virtual.VirtualArrayNode;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.JavaConstant;

/**

 * The {@code ArrayLength} instruction gets the length of an array.

 */

@NodeInfo(cycles = CYCLES_2, size = SIZE_1)

public final class ArrayLengthNode extends FixedWithNextNode implements Canonicalizable.Unary<ValueNode>, Lowerable, Virtualizable {

    public static final NodeClass<ArrayLengthNode> TYPE = NodeClass.create(ArrayLengthNode.class);

    @Input ValueNode array;

    public ValueNode array() {

        return array;

    }

    @Override

    public ValueNode getValue() {

        return array;

    }

    public ArrayLengthNode(ValueNode array) {

        super(TYPE, StampFactory.positiveInt());

        this.array = array;

    }

    public static ValueNode create(ValueNode forValue, ConstantReflectionProvider constantReflection) {

        if (forValue instanceof NewArrayNode) {

            NewArrayNode newArray = (NewArrayNode) forValue;

            return newArray.length();

        }

        ValueNode length = readArrayLengthConstant(forValue, constantReflection);

        if (length != null) {

            return length;

        }

        return new ArrayLengthNode(forValue);

    }

    @Override

    public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {

        ValueNode length = readArrayLength(forValue, tool.getConstantReflection());

        if (length != null) {

            return length;

        }

        return this;

    }

    /**

     * Gets the length of an array if possible.

     *

     * @return a node representing the length of {@code array} or null if it is not available

     */

    public static ValueNode readArrayLength(ValueNode originalArray, ConstantReflectionProvider constantReflection) {

        ValueNode length = GraphUtil.arrayLength(originalArray, ArrayLengthProvider.FindLengthMode.CANONICALIZE_READ);

        if (length != null) {

            return length;

        }

        return readArrayLengthConstant(originalArray, constantReflection);

    }

    private static ValueNode readArrayLengthConstant(ValueNode originalArray, ConstantReflectionProvider constantReflection) {

        ValueNode array = GraphUtil.unproxify(originalArray);

        if (constantReflection != null && array.isConstant() && !array.isNullConstant()) {

            JavaConstant constantValue = array.asJavaConstant();

            if (constantValue != null && constantValue.isNonNull()) {

                Integer constantLength = constantReflection.readArrayLength(constantValue);

                if (constantLength != null) {

                    return ConstantNode.forInt(constantLength);

                }

            }

        }

        return null;

    }

    @Override

    public void lower(LoweringTool tool) {

        tool.getLowerer().lower(this, tool);

    }

    @NodeIntrinsic

    public static native int arrayLength(Object array);

    @Override

    public void virtualize(VirtualizerTool tool) {

        ValueNode alias = tool.getAlias(array());

        if (alias instanceof VirtualArrayNode) {

            VirtualArrayNode virtualArray = (VirtualArrayNode) alias;

            tool.replaceWithValue(ConstantNode.forInt(virtualArray.entryCount(), graph()));

        }

    }

}