/*

 * Copyright (c) 2011, 2019, 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;

import java.util.Iterator;

import java.util.NoSuchElementException;

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

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

import org.graalvm.compiler.graph.IterableNodeType;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.graph.Position;

import org.graalvm.compiler.graph.iterators.NodeIterable;

import org.graalvm.compiler.nodeinfo.InputType;

import org.graalvm.compiler.nodeinfo.NodeInfo;

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

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

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

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

@NodeInfo(allowedUsageTypes = {InputType.Guard, InputType.Anchor})

public abstract class AbstractBeginNode extends FixedWithNextNode implements LIRLowerable, GuardingNode, AnchoringNode, IterableNodeType {

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

    private boolean withSpeculationFence;

    protected AbstractBeginNode(NodeClass<? extends AbstractBeginNode> c) {

        this(c, StampFactory.forVoid());

    }

    protected AbstractBeginNode(NodeClass<? extends AbstractBeginNode> c, Stamp stamp) {

        super(c, stamp);

    }

    public static AbstractBeginNode prevBegin(FixedNode from) {

        Node next = from;

        while (next != null) {

            if (next instanceof AbstractBeginNode) {

                return (AbstractBeginNode) next;

            }

            next = next.predecessor();

        }

        return null;

    }

    private void evacuateAnchored(FixedNode evacuateFrom) {

        if (!hasNoUsages()) {

            AbstractBeginNode prevBegin = prevBegin(evacuateFrom);

            assert prevBegin != null;

            replaceAtUsages(InputType.Anchor, prevBegin);

            replaceAtUsages(InputType.Guard, prevBegin);

            assert anchored().isEmpty() : anchored().snapshot();

        }

    }

    public void prepareDelete() {

        prepareDelete((FixedNode) predecessor());

    }

    public void prepareDelete(FixedNode evacuateFrom) {

        evacuateAnchored(evacuateFrom);

    }

    @Override

    public boolean verify() {

        assertTrue(predecessor() != null || this == graph().start() || this instanceof AbstractMergeNode, "begin nodes must be connected");

        return super.verify();

    }

    @Override

    public void generate(NodeLIRBuilderTool gen) {

        if (withSpeculationFence) {

            gen.getLIRGeneratorTool().emitSpeculationFence();

        }

    }

    public boolean isUsedAsGuardInput() {

        if (this.hasUsages()) {

            for (Node n : usages()) {

                for (Position inputPosition : n.inputPositions()) {

                    if (inputPosition.getInputType() == InputType.Guard && inputPosition.get(n) == this) {

                        return true;

                    }

                }

            }

        }

        return false;

    }

    public NodeIterable<GuardNode> guards() {

        return usages().filter(GuardNode.class);

    }

    public NodeIterable<Node> anchored() {

        return usages();

    }

    public boolean hasAnchored() {

        return this.hasUsages();

    }

    public NodeIterable<FixedNode> getBlockNodes() {

        return new NodeIterable<FixedNode>() {

            @Override

            public Iterator<FixedNode> iterator() {

                return new BlockNodeIterator(AbstractBeginNode.this);

            }

        };

    }

    /**

     * Set this begin node to be a speculation fence. This will prevent speculative execution of

     * this block.

     */

    public void setWithSpeculationFence() {

        this.withSpeculationFence = true;

    }

    private static class BlockNodeIterator implements Iterator<FixedNode> {

        private FixedNode current;

        BlockNodeIterator(FixedNode next) {

            this.current = next;

        }

        @Override

        public boolean hasNext() {

            return current != null;

        }

        @Override

        public FixedNode next() {

            FixedNode ret = current;

            if (ret == null) {

                throw new NoSuchElementException();

            }

            if (current instanceof FixedWithNextNode) {

                current = ((FixedWithNextNode) current).next();

                if (current instanceof AbstractBeginNode) {

                    current = null;

                }

            } else {

                current = null;

            }

            return ret;

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

}