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 * 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

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package org.graalvm.compiler.phases.common;

import java.util.List;

import org.graalvm.compiler.debug.GraalError;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.AbstractMergeNode;

import org.graalvm.compiler.nodes.DeoptimizingNode;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.FrameState;

import org.graalvm.compiler.nodes.LoopBeginNode;

import org.graalvm.compiler.nodes.LoopExitNode;

import org.graalvm.compiler.nodes.StateSplit;

import org.graalvm.compiler.nodes.StructuredGraph;

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

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

import org.graalvm.compiler.phases.Phase;

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

import org.graalvm.compiler.phases.graph.ReentrantNodeIterator.NodeIteratorClosure;

import jdk.vm.ci.code.BytecodeFrame;

/**

 * This phase transfers {@link FrameState} nodes from {@link StateSplit} nodes to

 * {@link DeoptimizingNode DeoptimizingNodes}.

 *

 * This allow to enter the {@link GuardsStage#AFTER_FSA AFTER_FSA} stage of the graph where no new

 * node that may cause deoptimization can be introduced anymore.

 * <p>

 * This Phase processes the graph in post order, assigning the {@link FrameState} from the last

 * {@link StateSplit} node to {@link DeoptimizingNode DeoptimizingNodes}.

 */

public class FrameStateAssignmentPhase extends Phase {

    private static class FrameStateAssignmentClosure extends NodeIteratorClosure<FrameState> {

        @Override

        protected FrameState processNode(FixedNode node, FrameState previousState) {

            FrameState currentState = previousState;

            if (node instanceof DeoptimizingNode.DeoptBefore) {

                DeoptimizingNode.DeoptBefore deopt = (DeoptimizingNode.DeoptBefore) node;

                if (deopt.canDeoptimize() && deopt.stateBefore() == null) {

                    GraalError.guarantee(currentState != null, "no FrameState at DeoptimizingNode %s", deopt);

                    deopt.setStateBefore(currentState);

                }

            }

            if (node instanceof StateSplit) {

                StateSplit stateSplit = (StateSplit) node;

                FrameState stateAfter = stateSplit.stateAfter();

                if (stateAfter != null) {

                    if (stateAfter.bci == BytecodeFrame.INVALID_FRAMESTATE_BCI) {

                        currentState = null;

                    } else {

                        currentState = stateAfter;

                    }

                    stateSplit.setStateAfter(null);

                }

            }

            if (node instanceof DeoptimizingNode.DeoptDuring) {

                DeoptimizingNode.DeoptDuring deopt = (DeoptimizingNode.DeoptDuring) node;

                if (deopt.canDeoptimize()) {

                    GraalError.guarantee(currentState != null, "no FrameState at DeoptimizingNode %s", deopt);

                    deopt.computeStateDuring(currentState);

                }

            }

            if (node instanceof DeoptimizingNode.DeoptAfter) {

                DeoptimizingNode.DeoptAfter deopt = (DeoptimizingNode.DeoptAfter) node;

                if (deopt.canDeoptimize() && deopt.stateAfter() == null) {

                    GraalError.guarantee(currentState != null, "no FrameState at DeoptimizingNode %s", deopt);

                    deopt.setStateAfter(currentState);

                }

            }

            return currentState;

        }

        @Override

        protected FrameState merge(AbstractMergeNode merge, List<FrameState> states) {

            FrameState singleFrameState = singleFrameState(states);

            return singleFrameState == null ? merge.stateAfter() : singleFrameState;

        }

        @Override

        protected FrameState afterSplit(AbstractBeginNode node, FrameState oldState) {

            return oldState;

        }

        @Override

        protected EconomicMap<LoopExitNode, FrameState> processLoop(LoopBeginNode loop, FrameState initialState) {

            return ReentrantNodeIterator.processLoop(this, loop, initialState).exitStates;

        }

    }

    @Override

    protected void run(StructuredGraph graph) {

        assert !graph.getGuardsStage().allowsFloatingGuards() && !hasFloatingDeopts(graph);

        if (graph.getGuardsStage().areFrameStatesAtSideEffects()) {

            ReentrantNodeIterator.apply(new FrameStateAssignmentClosure(), graph.start(), null);

            graph.setGuardsStage(GuardsStage.AFTER_FSA);

            graph.getNodes(FrameState.TYPE).filter(state -> state.hasNoUsages()).forEach(GraphUtil::killWithUnusedFloatingInputs);

        }

    }

    private static boolean hasFloatingDeopts(StructuredGraph graph) {

        for (Node n : graph.getNodes()) {

            if (n instanceof DeoptimizingNode && GraphUtil.isFloatingNode(n)) {

                DeoptimizingNode deoptimizingNode = (DeoptimizingNode) n;

                if (deoptimizingNode.canDeoptimize()) {

                    return true;

                }

            }

        }

        return false;

    }

    private static FrameState singleFrameState(List<FrameState> states) {

        FrameState singleState = states.get(0);

        for (int i = 1; i < states.size(); ++i) {

            if (states.get(i) != singleState) {

                return null;

            }

        }

        if (singleState != null && singleState.bci != BytecodeFrame.INVALID_FRAMESTATE_BCI) {

            return singleState;

        }

        return null;

    }

    @Override

    public boolean checkContract() {

        // TODO GR-1409

        return false;

    }

}