/*

 * Copyright (c) 2011, 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

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 */

package org.graalvm.compiler.virtual.phases.ea;

import static org.graalvm.compiler.core.common.GraalOptions.ReadEliminationMaxLoopVisits;

import static org.graalvm.compiler.nodes.NamedLocationIdentity.ARRAY_LENGTH_LOCATION;

import java.util.EnumMap;

import java.util.Iterator;

import java.util.List;

import org.graalvm.compiler.core.common.cfg.Loop;

import org.graalvm.compiler.core.common.spi.ConstantFieldProvider;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.FieldLocationIdentity;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.FixedWithNextNode;

import org.graalvm.compiler.nodes.LoopBeginNode;

import org.graalvm.compiler.nodes.LoopExitNode;

import org.graalvm.compiler.nodes.NamedLocationIdentity;

import org.graalvm.compiler.nodes.PhiNode;

import org.graalvm.compiler.nodes.ProxyNode;

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

import org.graalvm.compiler.nodes.ValueNode;

import org.graalvm.compiler.nodes.ValueProxyNode;

import org.graalvm.compiler.nodes.cfg.Block;

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

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

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

import org.graalvm.compiler.nodes.java.ArrayLengthNode;

import org.graalvm.compiler.nodes.java.LoadFieldNode;

import org.graalvm.compiler.nodes.java.LoadIndexedNode;

import org.graalvm.compiler.nodes.java.StoreFieldNode;

import org.graalvm.compiler.nodes.java.StoreIndexedNode;

import org.graalvm.compiler.nodes.memory.MemoryCheckpoint;

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

import org.graalvm.compiler.nodes.type.StampTool;

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

import org.graalvm.compiler.nodes.virtual.VirtualArrayNode;

import org.graalvm.compiler.options.OptionValues;

import org.graalvm.compiler.virtual.phases.ea.PEReadEliminationBlockState.ReadCacheEntry;

import org.graalvm.util.EconomicMap;

import org.graalvm.util.EconomicSet;

import org.graalvm.util.Equivalence;

import org.graalvm.util.MapCursor;

import org.graalvm.util.Pair;

import org.graalvm.word.LocationIdentity;

import jdk.vm.ci.meta.ConstantReflectionProvider;

import jdk.vm.ci.meta.JavaConstant;

import jdk.vm.ci.meta.JavaKind;

import jdk.vm.ci.meta.MetaAccessProvider;

import jdk.vm.ci.meta.ResolvedJavaType;

public final class PEReadEliminationClosure extends PartialEscapeClosure<PEReadEliminationBlockState> {

    private static final EnumMap<JavaKind, LocationIdentity> UNBOX_LOCATIONS;

    static {

        UNBOX_LOCATIONS = new EnumMap<>(JavaKind.class);

        for (JavaKind kind : JavaKind.values()) {

            UNBOX_LOCATIONS.put(kind, NamedLocationIdentity.immutable("PEA unbox " + kind.getJavaName()));

        }

    }

    public PEReadEliminationClosure(ScheduleResult schedule, MetaAccessProvider metaAccess, ConstantReflectionProvider constantReflection, ConstantFieldProvider constantFieldProvider,

                    LoweringProvider loweringProvider) {

        super(schedule, metaAccess, constantReflection, constantFieldProvider, loweringProvider);

    }

    @Override

    protected PEReadEliminationBlockState getInitialState() {

        return new PEReadEliminationBlockState(tool.getOptions(), tool.getDebug());

    }

    @Override

    protected boolean processNode(Node node, PEReadEliminationBlockState state, GraphEffectList effects, FixedWithNextNode lastFixedNode) {

        if (super.processNode(node, state, effects, lastFixedNode)) {

            return true;

        }

        if (node instanceof LoadFieldNode) {

            return processLoadField((LoadFieldNode) node, state, effects);

        } else if (node instanceof StoreFieldNode) {

            return processStoreField((StoreFieldNode) node, state, effects);

        } else if (node instanceof LoadIndexedNode) {

            return processLoadIndexed((LoadIndexedNode) node, state, effects);

        } else if (node instanceof StoreIndexedNode) {

            return processStoreIndexed((StoreIndexedNode) node, state, effects);

        } else if (node instanceof ArrayLengthNode) {

            return processArrayLength((ArrayLengthNode) node, state, effects);

        } else if (node instanceof UnboxNode) {

            return processUnbox((UnboxNode) node, state, effects);

        } else if (node instanceof RawLoadNode) {

            return processUnsafeLoad((RawLoadNode) node, state, effects);

        } else if (node instanceof RawStoreNode) {

            return processUnsafeStore((RawStoreNode) node, state, effects);

        } else if (node instanceof MemoryCheckpoint.Single) {

            COUNTER_MEMORYCHECKPOINT.increment(node.getDebug());

            LocationIdentity identity = ((MemoryCheckpoint.Single) node).getLocationIdentity();

            processIdentity(state, identity);

        } else if (node instanceof MemoryCheckpoint.Multi) {

            COUNTER_MEMORYCHECKPOINT.increment(node.getDebug());

            for (LocationIdentity identity : ((MemoryCheckpoint.Multi) node).getLocationIdentities()) {

                processIdentity(state, identity);

            }

        }

        return false;

    }

    private boolean processStore(FixedNode store, ValueNode object, LocationIdentity identity, int index, JavaKind accessKind, boolean overflowAccess, ValueNode value,

                    PEReadEliminationBlockState state, GraphEffectList effects) {

        ValueNode unproxiedObject = GraphUtil.unproxify(object);

        ValueNode cachedValue = state.getReadCache(object, identity, index, accessKind, this);

        ValueNode finalValue = getScalarAlias(value);

        boolean result = false;

        if (GraphUtil.unproxify(finalValue) == GraphUtil.unproxify(cachedValue)) {

            effects.deleteNode(store);

            result = true;

        }

        state.killReadCache(identity, index);

        state.addReadCache(unproxiedObject, identity, index, accessKind, overflowAccess, finalValue, this);

        return result;

    }

    private boolean processLoad(FixedNode load, ValueNode object, LocationIdentity identity, int index, JavaKind kind, PEReadEliminationBlockState state, GraphEffectList effects) {

        ValueNode unproxiedObject = GraphUtil.unproxify(object);

        ValueNode cachedValue = state.getReadCache(unproxiedObject, identity, index, kind, this);

        if (cachedValue != null) {

            // perform the read elimination

            effects.replaceAtUsages(load, cachedValue, load);

            addScalarAlias(load, cachedValue);

            return true;

        } else {

            state.addReadCache(unproxiedObject, identity, index, kind, false, load, this);

            return false;

        }

    }

    private static boolean isOverflowAccess(JavaKind accessKind, JavaKind declaredKind) {

        if (accessKind == declaredKind) {

            return false;

        }

        if (accessKind == JavaKind.Object) {

            switch (declaredKind) {

                case Object:

                case Double:

                case Long:

                    return false;

                default:

                    return true;

            }

        }

        assert accessKind.isPrimitive() : "Illegal access kind";

        return declaredKind.isPrimitive() ? accessKind.getBitCount() > declaredKind.getBitCount() : true;

    }

    private boolean processUnsafeLoad(RawLoadNode load, PEReadEliminationBlockState state, GraphEffectList effects) {

        if (load.offset().isConstant()) {

            ResolvedJavaType type = StampTool.typeOrNull(load.object());

            if (type != null && type.isArray()) {

                JavaKind accessKind = load.accessKind();

                JavaKind componentKind = type.getComponentType().getJavaKind();

                long offset = load.offset().asJavaConstant().asLong();

                int index = VirtualArrayNode.entryIndexForOffset(offset, accessKind, type.getComponentType(), Integer.MAX_VALUE);

                ValueNode object = GraphUtil.unproxify(load.object());

                LocationIdentity location = NamedLocationIdentity.getArrayLocation(componentKind);

                ValueNode cachedValue = state.getReadCache(object, location, index, accessKind, this);

                if (cachedValue != null) {

                    effects.replaceAtUsages(load, cachedValue, load);

                    addScalarAlias(load, cachedValue);

                    return true;

                } else {

                    state.addReadCache(object, location, index, accessKind, isOverflowAccess(accessKind, componentKind), load, this);

                }

            }

        }

        return false;

    }

    private boolean processUnsafeStore(RawStoreNode store, PEReadEliminationBlockState state, GraphEffectList effects) {

        ResolvedJavaType type = StampTool.typeOrNull(store.object());

        if (type != null && type.isArray()) {

            JavaKind accessKind = store.accessKind();

            JavaKind componentKind = type.getComponentType().getJavaKind();

            LocationIdentity location = NamedLocationIdentity.getArrayLocation(componentKind);

            if (store.offset().isConstant()) {

                long offset = store.offset().asJavaConstant().asLong();

                boolean overflowAccess = isOverflowAccess(accessKind, componentKind);

                int index = overflowAccess ? -1 : VirtualArrayNode.entryIndexForOffset(offset, accessKind, type.getComponentType(), Integer.MAX_VALUE);

                return processStore(store, store.object(), location, index, accessKind, overflowAccess, store.value(), state, effects);

            } else {

                processIdentity(state, location);

            }

        } else {

            state.killReadCache();

        }

        return false;

    }

    private boolean processArrayLength(ArrayLengthNode length, PEReadEliminationBlockState state, GraphEffectList effects) {

        return processLoad(length, length.array(), ARRAY_LENGTH_LOCATION, -1, JavaKind.Int, state, effects);

    }

    private boolean processStoreField(StoreFieldNode store, PEReadEliminationBlockState state, GraphEffectList effects) {

        if (store.isVolatile()) {

            state.killReadCache();

            return false;

        }

        JavaKind kind = store.field().getJavaKind();

        return processStore(store, store.object(), new FieldLocationIdentity(store.field()), -1, kind, false, store.value(), state, effects);

    }

    private boolean processLoadField(LoadFieldNode load, PEReadEliminationBlockState state, GraphEffectList effects) {

        if (load.isVolatile()) {

            state.killReadCache();

            return false;

        }

        return processLoad(load, load.object(), new FieldLocationIdentity(load.field()), -1, load.field().getJavaKind(), state, effects);

    }

    private static JavaKind getElementKindFromStamp(ValueNode array) {

        ResolvedJavaType type = StampTool.typeOrNull(array);

        if (type != null && type.isArray()) {

            return type.getComponentType().getJavaKind();

        } else {

            // It is likely an OSRLocal without valid stamp

            return JavaKind.Illegal;

        }

    }

    private boolean processStoreIndexed(StoreIndexedNode store, PEReadEliminationBlockState state, GraphEffectList effects) {

        int index = store.index().isConstant() ? ((JavaConstant) store.index().asConstant()).asInt() : -1;

        // BASTORE (with elementKind being Byte) can be used to store values in boolean arrays.

        JavaKind elementKind = store.elementKind();

        if (elementKind == JavaKind.Byte) {

            elementKind = getElementKindFromStamp(store.array());

            if (elementKind == JavaKind.Illegal) {

                // Could not determine the actual access kind from stamp. Hence kill both.

                state.killReadCache(NamedLocationIdentity.getArrayLocation(JavaKind.Boolean), index);

                state.killReadCache(NamedLocationIdentity.getArrayLocation(JavaKind.Byte), index);

                return false;

            }

        }

        LocationIdentity arrayLocation = NamedLocationIdentity.getArrayLocation(elementKind);

        if (index != -1) {

            return processStore(store, store.array(), arrayLocation, index, elementKind, false, store.value(), state, effects);

        } else {

            state.killReadCache(arrayLocation, -1);

        }

        return false;

    }

    private boolean processLoadIndexed(LoadIndexedNode load, PEReadEliminationBlockState state, GraphEffectList effects) {

        if (load.index().isConstant()) {

            int index = ((JavaConstant) load.index().asConstant()).asInt();

            // BALOAD (with elementKind being Byte) can be used to retrieve values from boolean

            // arrays.

            JavaKind elementKind = load.elementKind();

            if (elementKind == JavaKind.Byte) {

                elementKind = getElementKindFromStamp(load.array());

                if (elementKind == JavaKind.Illegal) {

                    return false;

                }

            }

            LocationIdentity arrayLocation = NamedLocationIdentity.getArrayLocation(elementKind);

            return processLoad(load, load.array(), arrayLocation, index, elementKind, state, effects);

        }

        return false;

    }

    private boolean processUnbox(UnboxNode unbox, PEReadEliminationBlockState state, GraphEffectList effects) {

        return processLoad(unbox, unbox.getValue(), UNBOX_LOCATIONS.get(unbox.getBoxingKind()), -1, unbox.getBoxingKind(), state, effects);

    }

    private static void processIdentity(PEReadEliminationBlockState state, LocationIdentity identity) {

        if (identity.isAny()) {

            state.killReadCache();

        } else {

            state.killReadCache(identity, -1);

        }

    }

    @SuppressWarnings("unchecked")

    @Override

    protected void processInitialLoopState(Loop<Block> loop, PEReadEliminationBlockState initialState) {

        super.processInitialLoopState(loop, initialState);

        if (!initialState.getReadCache().isEmpty()) {

            EconomicMap<ValueNode, Pair<ValueNode, Object>> firstValueSet = null;

            for (PhiNode phi : ((LoopBeginNode) loop.getHeader().getBeginNode()).phis()) {

                ValueNode firstValue = phi.valueAt(0);

                if (firstValue != null && phi.getStackKind().isObject()) {

                    ValueNode unproxified = GraphUtil.unproxify(firstValue);

                    if (firstValueSet == null) {

                        firstValueSet = EconomicMap.create(Equivalence.IDENTITY_WITH_SYSTEM_HASHCODE);

                    }

                    Pair<ValueNode, Object> pair = Pair.create(unproxified, firstValueSet.get(unproxified));

                    firstValueSet.put(unproxified, pair);

                }

            }

            if (firstValueSet != null) {

                ReadCacheEntry[] entries = new ReadCacheEntry[initialState.getReadCache().size()];

                int z = 0;

                for (ReadCacheEntry entry : initialState.getReadCache().getKeys()) {

                    entries[z++] = entry;

                }

                for (ReadCacheEntry entry : entries) {

                    ValueNode object = entry.object;

                    if (object != null) {

                        Pair<ValueNode, Object> pair = firstValueSet.get(object);

                        while (pair != null) {

                            initialState.addReadCache(pair.getLeft(), entry.identity, entry.index, entry.kind, entry.overflowAccess, initialState.getReadCache().get(entry), this);

                            pair = (Pair<ValueNode, Object>) pair.getRight();

                        }

                    }

                }

            }

        }

    }

    @Override

    protected void processLoopExit(LoopExitNode exitNode, PEReadEliminationBlockState initialState, PEReadEliminationBlockState exitState, GraphEffectList effects) {

        super.processLoopExit(exitNode, initialState, exitState, effects);

        if (exitNode.graph().hasValueProxies()) {

            MapCursor<ReadCacheEntry, ValueNode> entry = exitState.getReadCache().getEntries();

            while (entry.advance()) {

                if (initialState.getReadCache().get(entry.getKey()) != entry.getValue()) {

                    ValueNode value = exitState.getReadCache(entry.getKey().object, entry.getKey().identity, entry.getKey().index, entry.getKey().kind, this);

                    assert value != null : "Got null from read cache, entry's value:" + entry.getValue();

                    if (!(value instanceof ProxyNode) || ((ProxyNode) value).proxyPoint() != exitNode) {

                        ProxyNode proxy = new ValueProxyNode(value, exitNode);

                        effects.addFloatingNode(proxy, "readCacheProxy");

                        exitState.getReadCache().put(entry.getKey(), proxy);

                    }

                }

            }

        }

    }

    @Override

    protected PEReadEliminationBlockState cloneState(PEReadEliminationBlockState other) {

        return new PEReadEliminationBlockState(other);

    }

    @Override

    protected MergeProcessor createMergeProcessor(Block merge) {

        return new ReadEliminationMergeProcessor(merge);

    }

    private class ReadEliminationMergeProcessor extends MergeProcessor {

        ReadEliminationMergeProcessor(Block mergeBlock) {

            super(mergeBlock);

        }

        @Override

        protected void merge(List<PEReadEliminationBlockState> states) {

            super.merge(states);

            mergeReadCache(states);

        }

        private void mergeReadCache(List<PEReadEliminationBlockState> states) {

            MapCursor<ReadCacheEntry, ValueNode> cursor = states.get(0).readCache.getEntries();

            while (cursor.advance()) {

                ReadCacheEntry key = cursor.getKey();

                ValueNode value = cursor.getValue();

                boolean phi = false;

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

                    ValueNode otherValue = states.get(i).readCache.get(key);

                    // e.g. unsafe loads / stores with different access kinds have different stamps

                    // although location, object and offset are the same, in this case we cannot

                    // create a phi nor can we set a common value

                        value = null;

                        phi = false;

                        break;

                    }

                    if (!phi && otherValue != value) {

                        phi = true;

                    }

                }

                if (phi) {

                    mergeEffects.addFloatingNode(phiNode, "mergeReadCache");

                    for (int i = 0; i < states.size(); i++) {

                        ValueNode v = states.get(i).getReadCache(key.object, key.identity, key.index, key.kind, PEReadEliminationClosure.this);

                        setPhiInput(phiNode, i, v);

                    }

                    newState.readCache.put(key, phiNode);

                } else if (value != null) {

                    newState.readCache.put(key, value);

                }

            }

            /*

             * For object phis, see if there are known reads on all predecessors, for which we could

             * create new phis.

             */

            for (PhiNode phi : getPhis()) {

                if (phi.getStackKind() == JavaKind.Object) {

                    for (ReadCacheEntry entry : states.get(0).readCache.getKeys()) {

                        if (entry.object == getPhiValueAt(phi, 0)) {

                            mergeReadCachePhi(phi, entry.identity, entry.index, entry.kind, entry.overflowAccess, states);

                        }

                    }

                }

            }

        }

        private void mergeReadCachePhi(PhiNode phi, LocationIdentity identity, int index, JavaKind kind, boolean overflowAccess, List<PEReadEliminationBlockState> states) {

            ValueNode[] values = new ValueNode[states.size()];

            values[0] = states.get(0).getReadCache(getPhiValueAt(phi, 0), identity, index, kind, PEReadEliminationClosure.this);

            if (values[0] != null) {

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

                    ValueNode value = states.get(i).getReadCache(getPhiValueAt(phi, i), identity, index, kind, PEReadEliminationClosure.this);

                    // e.g. unsafe loads / stores with same identity and different access kinds see

                    // mergeReadCache(states)

                        return;

                    }

                    values[i] = value;

                }

                mergeEffects.addFloatingNode(phiNode, "mergeReadCachePhi");

                for (int i = 0; i < values.length; i++) {

                    setPhiInput(phiNode, i, values[i]);

                }

                newState.readCache.put(new ReadCacheEntry(identity, phi, index, kind, overflowAccess), phiNode);

            }

        }

    }

    @Override

    protected void processKilledLoopLocations(Loop<Block> loop, PEReadEliminationBlockState initialState, PEReadEliminationBlockState mergedStates) {

        assert initialState != null;

        assert mergedStates != null;

        if (initialState.readCache.size() > 0) {

            LoopKillCache loopKilledLocations = loopLocationKillCache.get(loop);

            // we have fully processed this loop the first time, remember to cache it the next time

            // it is visited

            if (loopKilledLocations == null) {

                loopKilledLocations = new LoopKillCache(1/* 1.visit */);

                loopLocationKillCache.put(loop, loopKilledLocations);

            } else {

                AbstractBeginNode beginNode = loop.getHeader().getBeginNode();

                OptionValues options = beginNode.getOptions();

                if (loopKilledLocations.visits() > ReadEliminationMaxLoopVisits.getValue(options)) {

                    // we have processed the loop too many times, kill all locations so the inner

                    // loop will never be processed more than once again on visit

                    loopKilledLocations.setKillsAll();

                } else {

                    // we have fully processed this loop >1 times, update the killed locations

                    EconomicSet<LocationIdentity> forwardEndLiveLocations = EconomicSet.create(Equivalence.DEFAULT);

                    for (ReadCacheEntry entry : initialState.readCache.getKeys()) {

                        forwardEndLiveLocations.add(entry.identity);

                    }

                    for (ReadCacheEntry entry : mergedStates.readCache.getKeys()) {

                        forwardEndLiveLocations.remove(entry.identity);

                    }

                    // every location that is alive before the loop but not after is killed by the

                    // loop

                    for (LocationIdentity location : forwardEndLiveLocations) {

                        loopKilledLocations.rememberLoopKilledLocation(location);

                    }

                    if (debug.isLogEnabled() && loopKilledLocations != null) {

                        debug.log("[Early Read Elimination] Setting loop killed locations of loop at node %s with %s",

                                        beginNode, forwardEndLiveLocations);

                    }

                }

                // remember the loop visit

                loopKilledLocations.visited();

            }

        }

    }

    @Override

    protected PEReadEliminationBlockState stripKilledLoopLocations(Loop<Block> loop, PEReadEliminationBlockState originalInitialState) {

        PEReadEliminationBlockState initialState = super.stripKilledLoopLocations(loop, originalInitialState);