/*

 * Copyright (c) 2013, 2016, 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.replacements;

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

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

import static org.graalvm.compiler.replacements.SnippetTemplate.DEFAULT_REPLACER;

import java.lang.reflect.Field;

import java.util.Arrays;

import org.graalvm.compiler.api.replacements.Fold;

import org.graalvm.compiler.api.replacements.Snippet;

import org.graalvm.compiler.api.replacements.Snippet.ConstantParameter;

import org.graalvm.compiler.api.replacements.SnippetReflectionProvider;

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

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.NodeClass;

import org.graalvm.compiler.nodeinfo.NodeInfo;

import org.graalvm.compiler.nodes.FixedWithNextNode;

import org.graalvm.compiler.nodes.NamedLocationIdentity;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.ValueNode;

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

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

import org.graalvm.compiler.options.OptionValues;

import org.graalvm.compiler.phases.util.Providers;

import org.graalvm.compiler.replacements.SnippetTemplate.AbstractTemplates;

import org.graalvm.compiler.replacements.SnippetTemplate.Arguments;

import org.graalvm.compiler.replacements.SnippetTemplate.SnippetInfo;

import org.graalvm.compiler.word.ObjectAccess;

import org.graalvm.word.LocationIdentity;

import jdk.vm.ci.code.TargetDescription;

import sun.misc.Unsafe;

/**

 * This node can be used to add a counter to the code that will estimate the dynamic number of calls

 * by adding an increment to the compiled code. This should of course only be used for

 * debugging/testing purposes.

 *

 * A unique counter will be created for each unique name passed to the constructor. Depending on the

 * value of withContext, the name of the root method is added to the counter's name.

 */

@NodeInfo(cycles = CYCLES_IGNORED, size = SIZE_IGNORED)

public class SnippetCounterNode extends FixedWithNextNode implements Lowerable {

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

    @Input protected ValueNode increment;

    protected final SnippetCounter counter;

    public SnippetCounterNode(SnippetCounter counter, ValueNode increment) {

        super(TYPE, StampFactory.forVoid());

        this.counter = counter;

        this.increment = increment;

    }

    public SnippetCounter getCounter() {

        return counter;

    }

    public ValueNode getIncrement() {

        return increment;

    }

    @NodeIntrinsic

    public static native void add(@ConstantNodeParameter SnippetCounter counter, int increment);

    public static void increment(@ConstantNodeParameter SnippetCounter counter) {

        add(counter, 1);

    }

    @Override

    public void lower(LoweringTool tool) {

        if (graph().getGuardsStage().areFrameStatesAtDeopts()) {

            SnippetCounterSnippets.Templates templates = tool.getReplacements().getSnippetTemplateCache(SnippetCounterSnippets.Templates.class);

            templates.lower(this, tool);

        }

    }

    /**

     * Add {@link #SNIPPET_COUNTER_LOCATION} to {@code privateLocations} if it isn't already there.

     *

     * @param privateLocations

     * @return a copy of privateLocations with any needed locations added

     */

    public static LocationIdentity[] addSnippetCounters(LocationIdentity[] privateLocations) {

        for (LocationIdentity location : privateLocations) {

            if (location.equals(SNIPPET_COUNTER_LOCATION)) {

                return privateLocations;

            }

        }

        LocationIdentity[] result = Arrays.copyOf(privateLocations, privateLocations.length + 1);

        result[result.length - 1] = SnippetCounterNode.SNIPPET_COUNTER_LOCATION;

        return result;

    }

    /**

     * We do not want to use the {@link LocationIdentity} of the {@link SnippetCounter#value()}

     * field, so that the usage in snippets is always possible. If a method accesses the counter via

     * the field and the snippet, the result might not be correct though.

     */

    public static final LocationIdentity SNIPPET_COUNTER_LOCATION = NamedLocationIdentity.mutable("SnippetCounter");

    static class SnippetCounterSnippets implements Snippets {

        @Fold

        static int countOffset() {

            try {

                return (int) UNSAFE.objectFieldOffset(SnippetCounter.class.getDeclaredField("value"));

            } catch (Exception e) {

                throw new GraalError(e);

            }

        }

        @Snippet

        public static void add(@ConstantParameter SnippetCounter counter, int increment) {

            long loadedValue = ObjectAccess.readLong(counter, countOffset(), SNIPPET_COUNTER_LOCATION);

            ObjectAccess.writeLong(counter, countOffset(), loadedValue + increment, SNIPPET_COUNTER_LOCATION);

        }

        public static class Templates extends AbstractTemplates {

            private final SnippetInfo add = snippet(SnippetCounterSnippets.class, "add", SNIPPET_COUNTER_LOCATION);

            }

            public void lower(SnippetCounterNode counter, LoweringTool tool) {

                StructuredGraph graph = counter.graph();

                Arguments args = new Arguments(add, graph.getGuardsStage(), tool.getLoweringStage());

                args.addConst("counter", counter.getCounter());

                args.add("increment", counter.getIncrement());

            }

        }

    }

    private static final Unsafe UNSAFE = initUnsafe();

    private static Unsafe initUnsafe() {

        try {

            return Unsafe.getUnsafe();

        } catch (SecurityException se) {

            try {

                Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");

                theUnsafe.setAccessible(true);

                return (Unsafe) theUnsafe.get(Unsafe.class);

            } catch (Exception e) {

                throw new RuntimeException("exception while trying to get Unsafe", e);

            }

        }

    }

}