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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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package org.graalvm.compiler.phases.common;

import jdk.internal.vm.compiler.collections.EconomicMap;

import jdk.internal.vm.compiler.collections.EconomicSet;

import jdk.internal.vm.compiler.collections.MapCursor;

import org.graalvm.compiler.graph.NodeStack;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.AbstractDeoptimizeNode;

import org.graalvm.compiler.nodes.AbstractEndNode;

import org.graalvm.compiler.nodes.AbstractMergeNode;

import org.graalvm.compiler.nodes.ControlSplitNode;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.phases.BasePhase;

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

/**

 * This phase will make sure that the branch leading towards this deopt has 0.0 probability.

 *

 */

public class PropagateDeoptimizeProbabilityPhase extends BasePhase<PhaseContext> {

    @Override

    @SuppressWarnings("try")

    protected void run(final StructuredGraph graph, PhaseContext context) {

        assert !graph.hasValueProxies() : "ConvertDeoptimizeToGuardPhase always creates proxies";

        if (graph.hasNode(AbstractDeoptimizeNode.TYPE)) {

            NodeStack stack = new NodeStack();

            EconomicMap<ControlSplitNode, EconomicSet<AbstractBeginNode>> reachableSplits = EconomicMap.create();

            // Mark all control flow nodes that are post-dominated by a deoptimization.

            for (AbstractDeoptimizeNode d : graph.getNodes(AbstractDeoptimizeNode.TYPE)) {

                stack.push(AbstractBeginNode.prevBegin(d));

                while (!stack.isEmpty()) {

                    AbstractBeginNode beginNode = (AbstractBeginNode) stack.pop();

                    FixedNode fixedNode = (FixedNode) beginNode.predecessor();

                    if (fixedNode == null) {

                        // Can happen for start node.

                    } else if (fixedNode instanceof AbstractMergeNode) {

                        AbstractMergeNode mergeNode = (AbstractMergeNode) fixedNode;

                        for (AbstractEndNode end : mergeNode.forwardEnds()) {

                            AbstractBeginNode newBeginNode = AbstractBeginNode.prevBegin(end);

                            stack.push(newBeginNode);

                        }

                    } else if (fixedNode instanceof ControlSplitNode) {

                        ControlSplitNode controlSplitNode = (ControlSplitNode) fixedNode;

                        EconomicSet<AbstractBeginNode> reachableSuccessors = reachableSplits.get(controlSplitNode);

                        if (reachableSuccessors == null) {

                            reachableSuccessors = EconomicSet.create();

                            reachableSplits.put(controlSplitNode, reachableSuccessors);

                        }

                        if (controlSplitNode.getSuccessorCount() == reachableSuccessors.size() - 1) {

                            // All successors of this split lead to deopt, propagate reachability

                            // further upwards.

                            reachableSplits.removeKey(controlSplitNode);

                            stack.push(AbstractBeginNode.prevBegin((FixedNode) controlSplitNode.predecessor()));

                        } else {

                            reachableSuccessors.add(beginNode);

                        }

                    } else {

                        stack.push(AbstractBeginNode.prevBegin(fixedNode));

                    }

                }

            }

            // Make sure the probability on the path towards the deoptimization is 0.0.

            MapCursor<ControlSplitNode, EconomicSet<AbstractBeginNode>> entries = reachableSplits.getEntries();

            while (entries.advance()) {

                ControlSplitNode controlSplitNode = entries.getKey();

                EconomicSet<AbstractBeginNode> value = entries.getValue();

                for (AbstractBeginNode begin : value) {

                    double probability = controlSplitNode.probability(begin);

                    if (probability != 0.0) {

                        controlSplitNode.setProbability(begin, 0.0);

                    }

                }

            }

        }

    }

}