/*

 * 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 org.graalvm.compiler.nodes.memory;

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

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

import static org.graalvm.compiler.nodes.NamedLocationIdentity.ARRAY_LENGTH_LOCATION;

import org.graalvm.compiler.core.common.LIRKind;

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

import org.graalvm.compiler.debug.DebugCloseable;

import org.graalvm.compiler.debug.GraalError;

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.InputType;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.CanonicalizableLocation;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.FrameState;

import org.graalvm.compiler.nodes.NodeView;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.extended.GuardingNode;

import org.graalvm.compiler.nodes.memory.address.AddressNode;

import org.graalvm.compiler.nodes.memory.address.OffsetAddressNode;

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

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

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

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

import jdk.internal.vm.compiler.word.LocationIdentity;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.MetaAccessProvider;

/**

 * Reads an {@linkplain FixedAccessNode accessed} value.

 */

@NodeInfo(nameTemplate = "Read#{p#location/s}", cycles = CYCLES_2, size = SIZE_1)

public class ReadNode extends FloatableAccessNode implements LIRLowerableAccess, Canonicalizable, Virtualizable, GuardingNode {

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

    public ReadNode(AddressNode address, LocationIdentity location, Stamp stamp, BarrierType barrierType) {

        this(TYPE, address, location, stamp, null, barrierType, false, null);

    }

    protected ReadNode(NodeClass<? extends ReadNode> c, AddressNode address, LocationIdentity location, Stamp stamp, GuardingNode guard, BarrierType barrierType, boolean nullCheck,

                    FrameState stateBefore) {

        super(c, address, location, stamp, guard, barrierType, nullCheck, stateBefore);

    }

    @Override

    public void generate(NodeLIRBuilderTool gen) {

        LIRKind readKind = gen.getLIRGeneratorTool().getLIRKind(getAccessStamp());

        gen.setResult(this, gen.getLIRGeneratorTool().getArithmetic().emitLoad(readKind, gen.operand(address), gen.state(this)));

    }

    @Override

    public Node canonical(CanonicalizerTool tool) {

        if (tool.allUsagesAvailable() && hasNoUsages()) {

            // Read without usages or guard can be safely removed.

            return null;

        }

        if (!getNullCheck()) {

            return canonicalizeRead(this, getAddress(), getLocationIdentity(), tool);

        } else {

            // if this read is a null check, then replacing it with the value is incorrect for

            // guard-type usages

            return this;

        }

    }

    @SuppressWarnings("try")

    @Override

    public FloatingAccessNode asFloatingNode(MemoryNode lastLocationAccess) {

        try (DebugCloseable position = withNodeSourcePosition()) {

            return graph().unique(new FloatingReadNode(getAddress(), getLocationIdentity(), lastLocationAccess, stamp(NodeView.DEFAULT), getGuard(), getBarrierType()));

        }

    }

    @Override

    public boolean isAllowedUsageType(InputType type) {

        return (getNullCheck() && type == InputType.Guard) ? true : super.isAllowedUsageType(type);

    }

    public static ValueNode canonicalizeRead(ValueNode read, AddressNode address, LocationIdentity locationIdentity, CanonicalizerTool tool) {

        NodeView view = NodeView.from(tool);

        MetaAccessProvider metaAccess = tool.getMetaAccess();

        if (tool.canonicalizeReads() && address instanceof OffsetAddressNode) {

            OffsetAddressNode objAddress = (OffsetAddressNode) address;

            ValueNode object = objAddress.getBase();

            if (metaAccess != null && object.isConstant() && !object.isNullConstant() && objAddress.getOffset().isConstant()) {

                long displacement = objAddress.getOffset().asJavaConstant().asLong();

                int stableDimension = ((ConstantNode) object).getStableDimension();

                if (locationIdentity.isImmutable() || stableDimension > 0) {

                    Constant constant = read.stamp(view).readConstant(tool.getConstantReflection().getMemoryAccessProvider(), object.asConstant(), displacement);

                    boolean isDefaultStable = locationIdentity.isImmutable() || ((ConstantNode) object).isDefaultStable();

                    if (constant != null && (isDefaultStable || !constant.isDefaultForKind())) {

                        return ConstantNode.forConstant(read.stamp(view), constant, Math.max(stableDimension - 1, 0), isDefaultStable, metaAccess);

                    }

                }

            }

            if (locationIdentity.equals(ARRAY_LENGTH_LOCATION)) {

                if (length != null) {

                    return length;

                }

            }

            if (locationIdentity instanceof CanonicalizableLocation) {

                CanonicalizableLocation canonicalize = (CanonicalizableLocation) locationIdentity;

                ValueNode result = canonicalize.canonicalizeRead(read, address, object, tool);

                assert result != null && result.stamp(view).isCompatible(read.stamp(view));

                return result;

            }

        }

        return read;

    }

    @Override

    public void virtualize(VirtualizerTool tool) {

        throw GraalError.shouldNotReachHere("unexpected ReadNode before PEA");

    }

    @Override

    public boolean canNullCheck() {

        return true;

    }

    @Override

    public Stamp getAccessStamp() {

        return stamp(NodeView.DEFAULT);

    }

}