/*
 * Copyright (c) 2018, 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
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package org.graalvm.compiler.nodes.extended;

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.Stamp;
import org.graalvm.compiler.graph.Node;
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.Lowerable;
import org.graalvm.compiler.nodes.spi.LoweringTool;
import org.graalvm.compiler.nodes.spi.StampProvider;

import jdk.vm.ci.meta.ConstantReflectionProvider;
import jdk.vm.ci.meta.MetaAccessProvider;
import jdk.vm.ci.meta.ResolvedJavaType;

Loads the component hub for of the provided array hub.
This is a fixed node because on certain VMs, for example the HotSpot VM, the read is only valid
when the provided hub is actually an array hub (and not, e.g., a primitive hub), so this node
must not float above a possible type check. Properly guarding this node would be possible too,
but it is unlikely that the guard would be more flexible than just fixing the node in the control
flow.
/**
 * Loads the component hub for of the provided array hub.
 *
 * This is a fixed node because on certain VMs, for example the HotSpot VM, the read is only valid
 * when the provided hub is actually an array hub (and not, e.g., a primitive hub), so this node
 * must not float above a possible type check. Properly guarding this node would be possible too,
 * but it is unlikely that the guard would be more flexible than just fixing the node in the control
 * flow.
 */
@NodeInfo(cycles = CYCLES_2, size = SIZE_1)
public final class LoadArrayComponentHubNode extends FixedWithNextNode implements Lowerable, Canonicalizable.Unary<ValueNode> {

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

    private @Input ValueNode value;

    public static ValueNode create(ValueNode value, StampProvider stampProvider, MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection) {
        Stamp stamp = stampProvider.createHubStamp(null);
        return findSynonym(null, value, stamp, metaAccess, constantReflection);
    }

    protected LoadArrayComponentHubNode(Stamp stamp, ValueNode value) {
        super(TYPE, stamp);
        this.value = value;
    }

    @Override
    public ValueNode getValue() {
        return value;
    }

    @Override
    public void lower(LoweringTool tool) {
        tool.getLowerer().lower(this, tool);
    }

    @Override
    public Node canonical(CanonicalizerTool tool, ValueNode forValue) {
        return findSynonym(this, forValue, stamp, tool.getMetaAccess(), tool.getConstantReflection());
    }

    private static ValueNode findSynonym(LoadArrayComponentHubNode self, ValueNode forValue, Stamp stamp, MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection) {
        if (forValue.isConstant()) {
            ResolvedJavaType type = constantReflection.asJavaType(forValue.asConstant());
            if (type != null) {
                return ConstantNode.forConstant(stamp, constantReflection.asObjectHub(type.getComponentType()), metaAccess);
            }
        }
        return self != null ? self : new LoadArrayComponentHubNode(stamp, forValue);
    }
}