/*

 * Copyright (c) 2012, 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.phases.common.inlining.info.elem;

import static org.graalvm.compiler.phases.common.DeadCodeEliminationPhase.Optionality.Optional;

import java.util.ArrayList;

import java.util.List;

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

import org.graalvm.compiler.debug.DebugContext;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeInputList;

import org.graalvm.compiler.nodes.ConstantNode;

import org.graalvm.compiler.nodes.Invoke;

import org.graalvm.compiler.nodes.ParameterNode;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.StructuredGraph.AllowAssumptions;

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.phases.common.CanonicalizerPhase;

import org.graalvm.compiler.phases.common.DeadCodeEliminationPhase;

import org.graalvm.compiler.phases.common.inlining.InliningUtil;

import org.graalvm.compiler.phases.graph.FixedNodeProbabilityCache;

import org.graalvm.compiler.phases.tiers.HighTierContext;

import jdk.vm.ci.meta.Constant;

import jdk.vm.ci.meta.ResolvedJavaMethod;

/**

 * <p>

 * Represents a feasible concrete target for inlining, whose graph has been copied already and thus

 * can be modified without affecting the original (usually cached) version.

 * </p>

 *

 * <p>

 * Instances of this class don't make sense in isolation but as part of an

 * {@link org.graalvm.compiler.phases.common.inlining.info.InlineInfo InlineInfo}.

 * </p>

 *

 * @see org.graalvm.compiler.phases.common.inlining.walker.InliningData#moveForward()

 * @see org.graalvm.compiler.phases.common.inlining.walker.CallsiteHolderExplorable

 */

public class InlineableGraph implements Inlineable {

    private final StructuredGraph graph;

    private FixedNodeProbabilityCache probabilites = new FixedNodeProbabilityCache();

    public InlineableGraph(final ResolvedJavaMethod method, final Invoke invoke, final HighTierContext context, CanonicalizerPhase canonicalizer) {

        StructuredGraph original = getOriginalGraph(method, context, canonicalizer, invoke.asNode().graph(), invoke.bci());

        // TODO copying the graph is only necessary if it is modified or if it contains any invokes

        this.graph = (StructuredGraph) original.copy(invoke.asNode().getDebug());

        specializeGraphToArguments(invoke, context, canonicalizer);

    }

    /**

     * This method looks up in a cache the graph for the argument, if not found bytecode is parsed.

     * The graph thus obtained is returned, ie the caller is responsible for cloning before

     * modification.

     */

    private static StructuredGraph getOriginalGraph(final ResolvedJavaMethod method, final HighTierContext context, CanonicalizerPhase canonicalizer, StructuredGraph caller, int callerBci) {

        StructuredGraph result = InliningUtil.getIntrinsicGraph(context.getReplacements(), method, callerBci);

        if (result != null) {

            return result;

        }

        return parseBytecodes(method, context, canonicalizer, caller);

    }

    /**

     * @return true iff one or more parameters <code>newGraph</code> were specialized to account for

     *         a constant argument, or an argument with a more specific stamp.

     */

    @SuppressWarnings("try")

    private boolean specializeGraphToArguments(final Invoke invoke, final HighTierContext context, CanonicalizerPhase canonicalizer) {

        DebugContext debug = graph.getDebug();

        try (DebugContext.Scope s = debug.scope("InlineGraph", graph)) {

            ArrayList<Node> parameterUsages = replaceParamsWithMoreInformativeArguments(invoke, context);

            if (parameterUsages != null) {

                assert !parameterUsages.isEmpty() : "The caller didn't have more information about arguments after all";

                canonicalizer.applyIncremental(graph, context, parameterUsages);

                return true;

            } else {

                // TODO (chaeubl): if args are not more concrete, inlining should be avoided

                // in most cases or we could at least use the previous graph size + invoke

                // probability to check the inlining

                return false;

            }

        } catch (Throwable e) {

            throw debug.handle(e);

        }

    }

    private static boolean isArgMoreInformativeThanParam(ValueNode arg, ParameterNode param) {

        return arg.isConstant() || canStampBeImproved(arg, param);

    }

    private static boolean canStampBeImproved(ValueNode arg, ParameterNode param) {

        return improvedStamp(arg, param) != null;

    }

    private static Stamp improvedStamp(ValueNode arg, ParameterNode param) {

        Stamp joinedStamp = param.stamp().join(arg.stamp());

        if (joinedStamp == null || joinedStamp.equals(param.stamp())) {

            return null;

        }

        return joinedStamp;

    }

    /**

     * This method detects:

     * <ul>

     * <li>constants among the arguments to the <code>invoke</code></li>

     * <li>arguments with more precise type than that declared by the corresponding parameter</li>

     * </ul>

     *

     * <p>

     * The corresponding parameters are updated to reflect the above information. Before doing so,

     * their usages are added to <code>parameterUsages</code> for later incremental

     * canonicalization.

     * </p>

     *

     * @return null if no incremental canonicalization is need, a list of nodes for such

     *         canonicalization otherwise.

     */

    private ArrayList<Node> replaceParamsWithMoreInformativeArguments(final Invoke invoke, final HighTierContext context) {

        NodeInputList<ValueNode> args = invoke.callTarget().arguments();

        ArrayList<Node> parameterUsages = null;

        List<ParameterNode> params = graph.getNodes(ParameterNode.TYPE).snapshot();

        assert params.size() <= args.size();

        /*

         * param-nodes that aren't used (eg, as a result of canonicalization) don't occur in

         * `params`. Thus, in general, the sizes of `params` and `args` don't always match. Still,

         * it's always possible to pair a param-node with its corresponding arg-node using

         * param.index() as index into `args`.

         */

        for (ParameterNode param : params) {

            if (param.usages().isNotEmpty()) {

                ValueNode arg = args.get(param.index());

                if (arg.isConstant()) {

                    Constant constant = arg.asConstant();

                    parameterUsages = trackParameterUsages(param, parameterUsages);

                    // collect param usages before replacing the param

                    param.replaceAtUsagesAndDelete(graph.unique(

                                    ConstantNode.forConstant(arg.stamp(), constant, ((ConstantNode) arg).getStableDimension(), ((ConstantNode) arg).isDefaultStable(), context.getMetaAccess())));

                    // param-node gone, leaving a gap in the sequence given by param.index()

                } else {

                    Stamp impro = improvedStamp(arg, param);

                    if (impro != null) {

                        param.setStamp(impro);

                        parameterUsages = trackParameterUsages(param, parameterUsages);

                    } else {

                        assert !isArgMoreInformativeThanParam(arg, param);

                    }

                }

            }

        }

        assert (parameterUsages == null) || (!parameterUsages.isEmpty());

        return parameterUsages;

    }

    private static ArrayList<Node> trackParameterUsages(ParameterNode param, ArrayList<Node> parameterUsages) {

        ArrayList<Node> result = (parameterUsages == null) ? new ArrayList<>() : parameterUsages;

        param.usages().snapshotTo(result);

        return result;

    }

    /**

     * This method builds the IR nodes for the given <code>method</code> and canonicalizes them.

     * Provided profiling info is mature, the resulting graph is cached. The caller is responsible

     * for cloning before modification.

     * </p>

     */

    @SuppressWarnings("try")

    private static StructuredGraph parseBytecodes(ResolvedJavaMethod method, HighTierContext context, CanonicalizerPhase canonicalizer, StructuredGraph caller) {

        DebugContext debug = caller.getDebug();

        StructuredGraph newGraph = new StructuredGraph.Builder(caller.getOptions(), debug, AllowAssumptions.ifNonNull(caller.getAssumptions())).method(method).build();

        try (DebugContext.Scope s = debug.scope("InlineGraph", newGraph)) {

            if (!caller.isUnsafeAccessTrackingEnabled()) {

                newGraph.disableUnsafeAccessTracking();

            }

            if (context.getGraphBuilderSuite() != null) {

                context.getGraphBuilderSuite().apply(newGraph, context);

            }

            assert newGraph.start().next() != null : "graph needs to be populated by the GraphBuilderSuite " + method + ", " + method.canBeInlined();

            new DeadCodeEliminationPhase(Optional).apply(newGraph);

            canonicalizer.apply(newGraph, context);

            return newGraph;

        } catch (Throwable e) {

            throw debug.handle(e);

        }

    }

    @Override

    public int getNodeCount() {

        return InliningUtil.getNodeCount(graph);

    }

    @Override

    public Iterable<Invoke> getInvokes() {

        return graph.getInvokes();

    }

    @Override

    public double getProbability(Invoke invoke) {

        return probabilites.applyAsDouble(invoke.asNode());

    }

    public StructuredGraph getGraph() {

        return graph;

    }

}