/*
 * Copyright (c) 2011, 2015, 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 com.oracle.graal.phases.schedule;

import static com.oracle.graal.compiler.common.GraalOptions.*;
import static com.oracle.graal.compiler.common.cfg.AbstractControlFlowGraph.*;

import java.util.*;

import com.oracle.graal.debug.*;
import jdk.internal.jvmci.meta.*;

import com.oracle.graal.compiler.common.*;
import com.oracle.graal.compiler.common.cfg.*;
import com.oracle.graal.graph.*;
import com.oracle.graal.nodes.*;
import com.oracle.graal.nodes.cfg.*;
import com.oracle.graal.nodes.memory.*;
import com.oracle.graal.phases.*;

public final class SchedulePhase extends Phase {

    /**
     * Error thrown when a graph cannot be scheduled.
     */
    public static class SchedulingError extends Error {

        private static final long serialVersionUID = 1621001069476473145L;

        public SchedulingError() {
            super();
        }

        /**
         * This constructor creates a {@link SchedulingError} with a message assembled via
         * {@link String#format(String, Object...)}.
         *
         * @param format a {@linkplain Formatter format} string
         * @param args parameters to {@link String#format(String, Object...)}
         */
        public SchedulingError(String format, Object... args) {
            super(String.format(format, args));
        }

    }

    public static enum SchedulingStrategy {
        EARLIEST,
        LATEST,
        LATEST_OUT_OF_LOOPS
    }

    private ControlFlowGraph cfg;

    /**
     * Map from blocks to the nodes in each block.
     */
    private BlockMap<List<Node>> blockToNodesMap;
    private BlockMap<LocationSet> blockToKillSet;
    private final SchedulingStrategy selectedStrategy;
    private NodeMap<Block> nodeToBlockMap;

    public SchedulePhase() {
        this(OptScheduleOutOfLoops.getValue() ? SchedulingStrategy.LATEST_OUT_OF_LOOPS : SchedulingStrategy.LATEST);
    }

    public SchedulePhase(SchedulingStrategy strategy) {
        this.selectedStrategy = strategy;
    }

    @Override
    protected void run(StructuredGraph graph) {
        // assert GraphOrder.assertNonCyclicGraph(graph);
        cfg = ControlFlowGraph.compute(graph, true, true, true, false);

        if (selectedStrategy == SchedulingStrategy.EARLIEST) {
            // Assign early so we are getting a context in case of an exception.
            this.nodeToBlockMap = graph.createNodeMap();
            this.blockToNodesMap = new BlockMap<>(cfg);
            NodeBitMap visited = graph.createNodeBitMap();
            scheduleEarliestIterative(cfg, blockToNodesMap, nodeToBlockMap, visited, graph);
            return;
        } else {
            boolean isOutOfLoops = selectedStrategy == SchedulingStrategy.LATEST_OUT_OF_LOOPS;
            if (selectedStrategy == SchedulingStrategy.LATEST || isOutOfLoops) {
                NodeMap<Block> currentNodeMap = graph.createNodeMap();
                BlockMap<List<Node>> earliestBlockToNodesMap = new BlockMap<>(cfg);
                NodeBitMap visited = graph.createNodeBitMap();

                // Assign early so we are getting a context in case of an exception.
                this.blockToNodesMap = earliestBlockToNodesMap;
                this.nodeToBlockMap = currentNodeMap;

                scheduleEarliestIterative(cfg, earliestBlockToNodesMap, currentNodeMap, visited, graph);
                BlockMap<List<Node>> latestBlockToNodesMap = new BlockMap<>(cfg);

                for (Block b : cfg.getBlocks()) {
                    latestBlockToNodesMap.put(b, new ArrayList<Node>());
                }

                BlockMap<ArrayList<FloatingReadNode>> watchListMap = calcLatestBlocks(isOutOfLoops, currentNodeMap, earliestBlockToNodesMap, visited, latestBlockToNodesMap);
                sortNodesLatestWithinBlock(cfg, earliestBlockToNodesMap, latestBlockToNodesMap, currentNodeMap, watchListMap, visited);

                assert verifySchedule(cfg, latestBlockToNodesMap, currentNodeMap);
                assert MemoryScheduleVerification.check(cfg.getStartBlock(), latestBlockToNodesMap);

                this.blockToNodesMap = latestBlockToNodesMap;
                this.nodeToBlockMap = currentNodeMap;

                cfg.setNodeToBlock(currentNodeMap);
            }
        }
    }

    @SuppressFBWarnings(value = "RCN_REDUNDANT_NULLCHECK_WOULD_HAVE_BEEN_A_NPE", justification = "false positive found by findbugs")
    private BlockMap<ArrayList<FloatingReadNode>> calcLatestBlocks(boolean isOutOfLoops, NodeMap<Block> currentNodeMap, BlockMap<List<Node>> earliestBlockToNodesMap, NodeBitMap visited,
                    BlockMap<List<Node>> latestBlockToNodesMap) {
        BlockMap<ArrayList<FloatingReadNode>> watchListMap = null;
        for (Block b : cfg.postOrder()) {
            List<Node> blockToNodes = earliestBlockToNodesMap.get(b);
            LocationSet killed = null;
            int previousIndex = blockToNodes.size();
            for (int i = blockToNodes.size() - 1; i >= 0; --i) {
                Node currentNode = blockToNodes.get(i);
                assert currentNodeMap.get(currentNode) == b;
                assert !(currentNode instanceof PhiNode) && !(currentNode instanceof ProxyNode);
                assert visited.isMarked(currentNode);
                if (currentNode instanceof FixedNode) {
                    // For these nodes, the earliest is at the same time the latest block.
                } else {
                    Block currentBlock = b;
                    assert currentBlock != null;

                    Block latestBlock = calcLatestBlock(b, isOutOfLoops, currentNode, currentNodeMap);
                    assert checkLatestEarliestRelation(currentNode, currentBlock, latestBlock);
                    if (latestBlock != currentBlock) {
                        if (currentNode instanceof FloatingReadNode) {

                            FloatingReadNode floatingReadNode = (FloatingReadNode) currentNode;
                            LocationIdentity location = floatingReadNode.getLocationIdentity();
                            if (location.isMutable()) {
                                if (currentBlock.canKill(location)) {
                                    if (killed == null) {
                                        killed = new LocationSet();
                                    }
                                    fillKillSet(killed, blockToNodes.subList(i + 1, previousIndex));
                                    previousIndex = i;
                                    if (killed.contains(location)) {
                                        latestBlock = currentBlock;
                                    }
                                }

                                if (latestBlock != currentBlock) {
                                    // We are not constraint within currentBlock. Check if
                                    // we are contraint while walking down the dominator
                                    // line.
                                    Block newLatestBlock = adjustLatestForRead(floatingReadNode, currentBlock, latestBlock, location);
                                    assert dominates(newLatestBlock, latestBlock);
                                    assert dominates(currentBlock, newLatestBlock);
                                    latestBlock = newLatestBlock;

                                    if (newLatestBlock != currentBlock && latestBlock.canKill(location)) {
                                        if (watchListMap == null) {
                                            watchListMap = new BlockMap<>(cfg);
                                        }
                                        if (watchListMap.get(latestBlock) == null) {
                                            watchListMap.put(latestBlock, new ArrayList<>());
                                        }
                                        watchListMap.get(latestBlock).add(floatingReadNode);
                                    }
                                }
                            }
                        }
                        currentNodeMap.set(currentNode, latestBlock);
                        currentBlock = latestBlock;
                    }
                    latestBlockToNodesMap.get(currentBlock).add(currentNode);
                }
            }
        }
        return watchListMap;
    }

    private static boolean checkLatestEarliestRelation(Node currentNode, Block earliestBlock, Block latestBlock) {
        assert AbstractControlFlowGraph.dominates(earliestBlock, latestBlock) || (currentNode instanceof VirtualState && latestBlock == earliestBlock.getDominator()) : String.format(
                        "%s %s (%s) %s (%s)", currentNode, earliestBlock, earliestBlock.getBeginNode(), latestBlock, latestBlock.getBeginNode());
        return true;
    }

    private static boolean verifySchedule(ControlFlowGraph cfg, BlockMap<List<Node>> blockToNodesMap, NodeMap<Block> nodeMap) {
        for (Block b : cfg.getBlocks()) {
            List<Node> nodes = blockToNodesMap.get(b);
            for (Node n : nodes) {
                assert n.isAlive();
                assert nodeMap.get(n) == b;
            }
        }
        return true;
    }

    private static Block adjustLatestForRead(FloatingReadNode floatingReadNode, Block earliestBlock, Block latestBlock, LocationIdentity location) {
        assert strictlyDominates(earliestBlock, latestBlock);
        Block current = latestBlock.getDominator();

        // Collect dominator chain that needs checking.
        List<Block> dominatorChain = new ArrayList<>();
        dominatorChain.add(latestBlock);
        while (current != earliestBlock) {
            // Current is an intermediate dominator between earliestBlock and latestBlock.
            assert strictlyDominates(earliestBlock, current) && strictlyDominates(current, latestBlock);
            if (current.canKill(location)) {
                dominatorChain.clear();
            }
            dominatorChain.add(current);
            current = current.getDominator();
            assert current != null : floatingReadNode;
        }

        // The first element of dominatorChain now contains the latest possible block.
        assert dominatorChain.size() >= 1;
        assert dominatorChain.get(dominatorChain.size() - 1).getDominator() == earliestBlock;

        Block lastBlock = earliestBlock;
        for (int i = dominatorChain.size() - 1; i >= 0; --i) {
            Block currentBlock = dominatorChain.get(i);
            if (currentBlock.getLoopDepth() > lastBlock.getLoopDepth()) {
                // We are entering a loop boundary. The new loops must not kill the location for the
                // crossing to be safe.
                if (currentBlock.getLoop() != null && ((HIRLoop) currentBlock.getLoop()).canKill(location)) {
                    break;
                }
            }

            if (currentBlock.canKillBetweenThisAndDominator(location)) {
                break;
            }
            lastBlock = currentBlock;
        }

        return lastBlock;
    }

    private static void fillKillSet(LocationSet killed, List<Node> subList) {
        if (!killed.isAny()) {
            for (Node n : subList) {
                // Check if this node kills a node in the watch list.
                if (n instanceof MemoryCheckpoint.Single) {
                    LocationIdentity identity = ((MemoryCheckpoint.Single) n).getLocationIdentity();
                    killed.add(identity);
                    if (killed.isAny()) {
                        return;
                    }
                } else if (n instanceof MemoryCheckpoint.Multi) {
                    for (LocationIdentity identity : ((MemoryCheckpoint.Multi) n).getLocationIdentities()) {
                        killed.add(identity);
                        if (killed.isAny()) {
                            return;
                        }
                    }
                }
            }
        }
    }

    private static void sortNodesLatestWithinBlock(ControlFlowGraph cfg, BlockMap<List<Node>> earliestBlockToNodesMap, BlockMap<List<Node>> latestBlockToNodesMap, NodeMap<Block> currentNodeMap,
                    BlockMap<ArrayList<FloatingReadNode>> watchListMap, NodeBitMap visited) {
        for (Block b : cfg.getBlocks()) {
            sortNodesLatestWithinBlock(b, earliestBlockToNodesMap, latestBlockToNodesMap, currentNodeMap, watchListMap, visited);
        }
    }

    private static void sortNodesLatestWithinBlock(Block b, BlockMap<List<Node>> earliestBlockToNodesMap, BlockMap<List<Node>> latestBlockToNodesMap, NodeMap<Block> nodeMap,
                    BlockMap<ArrayList<FloatingReadNode>> watchListMap, NodeBitMap unprocessed) {
        List<Node> earliestSorting = earliestBlockToNodesMap.get(b);
        ArrayList<Node> result = new ArrayList<>(earliestSorting.size());
        ArrayList<FloatingReadNode> watchList = null;
        if (watchListMap != null) {
            watchList = watchListMap.get(b);
            assert watchList == null || !b.getKillLocations().isEmpty();
        }
        AbstractBeginNode beginNode = b.getBeginNode();
        if (beginNode instanceof LoopExitNode) {
            LoopExitNode loopExitNode = (LoopExitNode) beginNode;
            for (ProxyNode proxy : loopExitNode.proxies()) {
                unprocessed.clear(proxy);
                ValueNode value = proxy.value();
                if (value != null && nodeMap.get(value) == b) {
                    sortIntoList(value, b, result, nodeMap, unprocessed, null);
                }
            }
        }
        FixedNode endNode = b.getEndNode();
        FixedNode fixedEndNode = null;
        if (isFixedEnd(endNode)) {
            // Only if the end node is either a control split or an end node, we need to force it to
            // be the last node in the schedule.
            fixedEndNode = endNode;
        }
        for (Node n : earliestSorting) {
            if (n != fixedEndNode) {
                if (n instanceof FixedNode) {
                    assert nodeMap.get(n) == b;
                    checkWatchList(b, nodeMap, unprocessed, result, watchList, n);
                    sortIntoList(n, b, result, nodeMap, unprocessed, null);
                } else if (nodeMap.get(n) == b && n instanceof FloatingReadNode) {
                    FloatingReadNode floatingReadNode = (FloatingReadNode) n;
                    LocationIdentity location = floatingReadNode.getLocationIdentity();
                    if (b.canKill(location)) {
                        // This read can be killed in this block, add to watch list.
                        if (watchList == null) {
                            watchList = new ArrayList<>();
                        }
                        watchList.add(floatingReadNode);
                    }
                }
            }
        }

        for (Node n : latestBlockToNodesMap.get(b)) {
            assert nodeMap.get(n) == b;
            assert !(n instanceof FixedNode);
            if (unprocessed.isMarked(n)) {
                sortIntoList(n, b, result, nodeMap, unprocessed, fixedEndNode);
            }
        }

        if (endNode != null && unprocessed.isMarked(endNode)) {
            sortIntoList(endNode, b, result, nodeMap, unprocessed, null);
        }

        latestBlockToNodesMap.put(b, result);
    }

    private static void checkWatchList(Block b, NodeMap<Block> nodeMap, NodeBitMap unprocessed, ArrayList<Node> result, ArrayList<FloatingReadNode> watchList, Node n) {
        if (watchList != null && !watchList.isEmpty()) {
            // Check if this node kills a node in the watch list.
            if (n instanceof MemoryCheckpoint.Single) {
                LocationIdentity identity = ((MemoryCheckpoint.Single) n).getLocationIdentity();
                checkWatchList(watchList, identity, b, result, nodeMap, unprocessed);
            } else if (n instanceof MemoryCheckpoint.Multi) {
                for (LocationIdentity identity : ((MemoryCheckpoint.Multi) n).getLocationIdentities()) {
                    checkWatchList(watchList, identity, b, result, nodeMap, unprocessed);
                }
            }
        }
    }

    private static void checkWatchList(ArrayList<FloatingReadNode> watchList, LocationIdentity identity, Block b, ArrayList<Node> result, NodeMap<Block> nodeMap, NodeBitMap unprocessed) {
        assert identity.isMutable();
        if (identity.isAny()) {
            for (FloatingReadNode r : watchList) {
                if (unprocessed.isMarked(r)) {
                    sortIntoList(r, b, result, nodeMap, unprocessed, null);
                }
            }
            watchList.clear();
        } else {
            int index = 0;
            while (index < watchList.size()) {
                FloatingReadNode r = watchList.get(index);
                LocationIdentity locationIdentity = r.getLocationIdentity();
                assert locationIdentity.isMutable();
                if (unprocessed.isMarked(r)) {
                    if (identity.overlaps(locationIdentity)) {
                        sortIntoList(r, b, result, nodeMap, unprocessed, null);
                    } else {
                        ++index;
                        continue;
                    }
                }
                int lastIndex = watchList.size() - 1;
                watchList.set(index, watchList.get(lastIndex));
                watchList.remove(lastIndex);
            }
        }
    }

    private static void sortIntoList(Node n, Block b, ArrayList<Node> result, NodeMap<Block> nodeMap, NodeBitMap unprocessed, Node excludeNode) {
        assert unprocessed.isMarked(n) : n;
        unprocessed.clear(n);

        assert nodeMap.get(n) == b;

        if (n instanceof PhiNode) {
            return;
        }

        for (Node input : n.inputs()) {
            if (nodeMap.get(input) == b && unprocessed.isMarked(input) && input != excludeNode) {
                sortIntoList(input, b, result, nodeMap, unprocessed, excludeNode);
            }
        }

        if (n instanceof ProxyNode) {
            // Skip proxy nodes.
        } else {
            result.add(n);
        }

    }

    private static Block calcLatestBlock(Block earliestBlock, boolean scheduleOutOfLoops, Node currentNode, NodeMap<Block> currentNodeMap) {
        Block block = null;
        assert currentNode.hasUsages();
        for (Node usage : currentNode.usages()) {
            block = calcBlockForUsage(currentNode, usage, block, currentNodeMap);
            assert checkLatestEarliestRelation(currentNode, earliestBlock, block);
            if (scheduleOutOfLoops) {
                while (block.getLoopDepth() > earliestBlock.getLoopDepth() && block != earliestBlock.getDominator()) {
                    block = block.getDominator();
                    assert checkLatestEarliestRelation(currentNode, earliestBlock, block);
                }
            }
        }
        assert block != null : currentNode;
        return block;
    }

    private static Block calcBlockForUsage(Node node, Node usage, Block startCurrentBlock, NodeMap<Block> currentNodeMap) {
        assert !(node instanceof PhiNode);
        Block currentBlock = startCurrentBlock;
        if (usage instanceof PhiNode) {
            // An input to a PhiNode is used at the end of the predecessor block that corresponds to
            // the PhiNode input. One PhiNode can use an input multiple times.
            PhiNode phi = (PhiNode) usage;
            AbstractMergeNode merge = phi.merge();
            Block mergeBlock = currentNodeMap.get(merge);
            for (int i = 0; i < phi.valueCount(); ++i) {
                if (phi.valueAt(i) == node) {
                    currentBlock = AbstractControlFlowGraph.commonDominatorTyped(currentBlock, mergeBlock.getPredecessors().get(i));
                }
            }
        } else if (usage instanceof AbstractBeginNode) {
            AbstractBeginNode abstractBeginNode = (AbstractBeginNode) usage;
            if (abstractBeginNode instanceof StartNode) {
                currentBlock = currentNodeMap.get(abstractBeginNode);
            } else {
                currentBlock = AbstractControlFlowGraph.commonDominatorTyped(currentBlock, currentNodeMap.get(abstractBeginNode).getDominator());
            }
        } else {
            // All other types of usages: Put the input into the same block as the usage.
            currentBlock = AbstractControlFlowGraph.commonDominatorTyped(currentBlock, currentNodeMap.get(usage));
        }
        return currentBlock;
    }

    private static void scheduleEarliestIterative(ControlFlowGraph cfg, BlockMap<List<Node>> blockToNodes, NodeMap<Block> nodeToBlock, NodeBitMap visited, StructuredGraph graph) {

        BitSet floatingReads = new BitSet(cfg.getBlocks().size());

        // Add begin nodes as the first entry and set the block for phi nodes.
        for (Block b : cfg.getBlocks()) {
            AbstractBeginNode beginNode = b.getBeginNode();
            ArrayList<Node> nodes = new ArrayList<>();
            nodeToBlock.set(beginNode, b);
            nodes.add(beginNode);
            blockToNodes.put(b, nodes);

            if (beginNode instanceof AbstractMergeNode) {
                AbstractMergeNode mergeNode = (AbstractMergeNode) beginNode;
                for (PhiNode phi : mergeNode.phis()) {
                    nodeToBlock.set(phi, b);
                }
            } else if (beginNode instanceof LoopExitNode) {
                LoopExitNode loopExitNode = (LoopExitNode) beginNode;
                for (ProxyNode proxy : loopExitNode.proxies()) {
                    nodeToBlock.set(proxy, b);
                }
            }
        }

        NodeStack stack = new NodeStack();

        // Start analysis with control flow ends.
        for (Block b : cfg.postOrder()) {
            FixedNode endNode = b.getEndNode();
            if (isFixedEnd(endNode)) {
                stack.push(endNode);
                nodeToBlock.set(endNode, b);
            }
        }

        processStack(cfg, blockToNodes, nodeToBlock, visited, floatingReads, stack);

        // Visit back input edges of loop phis.
        boolean changed;
        boolean unmarkedPhi;
        do {
            changed = false;
            unmarkedPhi = false;
            for (LoopBeginNode loopBegin : graph.getNodes(LoopBeginNode.TYPE)) {
                for (PhiNode phi : loopBegin.phis()) {
                    if (visited.isMarked(phi)) {
                        for (int i = 0; i < loopBegin.getLoopEndCount(); ++i) {
                            Node node = phi.valueAt(i + loopBegin.forwardEndCount());
                            if (node != null && !visited.isMarked(node)) {
                                changed = true;
                                stack.push(node);
                                processStack(cfg, blockToNodes, nodeToBlock, visited, floatingReads, stack);
                            }
                        }
                    } else {
                        unmarkedPhi = true;
                    }
                }
            }

            /*
             * the processing of one loop phi could have marked a previously checked loop phi,
             * therefore this needs to be iterative.
             */
        } while (unmarkedPhi && changed);

        // Check for dead nodes.
        if (visited.getCounter() < graph.getNodeCount()) {
            for (Node n : graph.getNodes()) {
                if (!visited.isMarked(n)) {
                    n.clearInputs();
                    n.markDeleted();
                }
            }
        }

        // Add end nodes as the last nodes in each block.
        for (Block b : cfg.getBlocks()) {
            FixedNode endNode = b.getEndNode();
            if (isFixedEnd(endNode)) {
                if (endNode != b.getBeginNode()) {
                    addNode(blockToNodes, b, endNode);
                }
            }
        }

        if (!floatingReads.isEmpty()) {
            for (Block b : cfg.getBlocks()) {
                if (floatingReads.get(b.getId())) {
                    resortEarliestWithinBlock(b, blockToNodes, nodeToBlock, visited);
                }
            }
        }

        assert MemoryScheduleVerification.check(cfg.getStartBlock(), blockToNodes);
    }

    private static boolean isFixedEnd(FixedNode endNode) {
        return endNode instanceof ControlSplitNode || endNode instanceof ControlSinkNode || endNode instanceof AbstractEndNode;
    }

    private static void resortEarliestWithinBlock(Block b, BlockMap<List<Node>> blockToNodes, NodeMap<Block> nodeToBlock, NodeBitMap unprocessed) {
        ArrayList<FloatingReadNode> watchList = new ArrayList<>();
        List<Node> oldList = blockToNodes.get(b);
        AbstractBeginNode beginNode = b.getBeginNode();
        for (Node n : oldList) {
            if (n instanceof FloatingReadNode) {
                FloatingReadNode floatingReadNode = (FloatingReadNode) n;
                LocationIdentity locationIdentity = floatingReadNode.getLocationIdentity();
                MemoryNode lastLocationAccess = floatingReadNode.getLastLocationAccess();
                if (locationIdentity.isMutable() && lastLocationAccess != null) {
                    ValueNode lastAccessLocation = lastLocationAccess.asNode();
                    if (nodeToBlock.get(lastAccessLocation) == b && lastAccessLocation != beginNode && !(lastAccessLocation instanceof MemoryPhiNode)) {
                        // This node's last access location is within this block. Add to watch list
                        // when processing the last access location.
                    } else {
                        watchList.add(floatingReadNode);
                    }
                }
            }
        }

        ArrayList<Node> newList = new ArrayList<>(oldList.size());
        assert oldList.get(0) == beginNode;
        unprocessed.clear(beginNode);
        newList.add(beginNode);
        for (int i = 1; i < oldList.size(); ++i) {
            Node n = oldList.get(i);
            if (unprocessed.isMarked(n)) {
                if (n instanceof MemoryNode) {
                    if (n instanceof MemoryCheckpoint) {
                        assert n instanceof FixedNode;
                        if (watchList.size() > 0) {
                            // Check whether we need to commit reads from the watch list.
                            checkWatchList(b, nodeToBlock, unprocessed, newList, watchList, n);
                        }
                    }
                    // Add potential dependent reads to the watch list.
                    for (Node usage : n.usages()) {
                        if (usage instanceof FloatingReadNode) {
                            FloatingReadNode floatingReadNode = (FloatingReadNode) usage;
                            if (nodeToBlock.get(floatingReadNode) == b && floatingReadNode.getLastLocationAccess() == n && !(n instanceof MemoryPhiNode)) {
                                watchList.add(floatingReadNode);
                            }
                        }
                    }
                }
                assert unprocessed.isMarked(n);
                unprocessed.clear(n);
                newList.add(n);
            } else {
                // This node was pulled up.
                assert !(n instanceof FixedNode) : n;
            }
        }

        for (Node n : newList) {
            unprocessed.mark(n);
        }

        assert newList.size() == oldList.size();
        blockToNodes.put(b, newList);
    }

    private static void addNode(BlockMap<List<Node>> blockToNodes, Block b, Node endNode) {
        assert !blockToNodes.get(b).contains(endNode) : endNode;
        blockToNodes.get(b).add(endNode);
    }

    private static void processStack(ControlFlowGraph cfg, BlockMap<List<Node>> blockToNodes, NodeMap<Block> nodeToBlock, NodeBitMap visited, BitSet floatingReads, NodeStack stack) {
        Block startBlock = cfg.getStartBlock();
        while (!stack.isEmpty()) {
            Node current = stack.peek();
            if (visited.checkAndMarkInc(current)) {

                // Push inputs and predecessor.
                Node predecessor = current.predecessor();
                if (predecessor != null) {
                    stack.push(predecessor);
                }

                if (current instanceof PhiNode) {
                    PhiNode phiNode = (PhiNode) current;
                    AbstractMergeNode merge = phiNode.merge();
                    for (int i = 0; i < merge.forwardEndCount(); ++i) {
                        Node input = phiNode.valueAt(i);
                        if (input != null) {
                            stack.push(input);
                        }
                    }
                } else if (current instanceof ProxyNode) {
                    ProxyNode proxyNode = (ProxyNode) current;
                    for (Node input : proxyNode.inputs()) {
                        if (input != proxyNode.proxyPoint()) {
                            stack.push(input);
                        }
                    }
                } else if (current instanceof FrameState) {
                    for (Node input : current.inputs()) {
                        if (input instanceof StateSplit && ((StateSplit) input).stateAfter() == current) {
                            // Ignore the cycle.
                        } else {
                            stack.push(input);
                        }
                    }
                } else {
                    current.pushInputs(stack);
                }
            } else {

                stack.pop();

                if (nodeToBlock.get(current) == null) {
                    Block curBlock = cfg.blockFor(current);
                    if (curBlock == null) {
                        assert current.predecessor() == null && !(current instanceof FixedNode) : "The assignment of blocks to fixed nodes is already done when constructing the cfg.";
                        Block earliest = startBlock;
                        for (Node input : current.inputs()) {
                            Block inputEarliest = nodeToBlock.get(input);
                            if (inputEarliest == null) {
                                assert current instanceof FrameState && input instanceof StateSplit && ((StateSplit) input).stateAfter() == current : current;
                            } else {
                                assert inputEarliest != null;
                                if (inputEarliest.getEndNode() == input) {
                                    // This is the last node of the block.
                                    if (current instanceof FrameState && input instanceof StateSplit && ((StateSplit) input).stateAfter() == current) {
                                        // Keep regular inputEarliest.
                                    } else if (input instanceof ControlSplitNode) {
                                        inputEarliest = nodeToBlock.get(((ControlSplitNode) input).getPrimarySuccessor());
                                    } else {
                                        assert inputEarliest.getSuccessorCount() == 1;
                                        assert !(input instanceof AbstractEndNode);
                                        // Keep regular inputEarliest
                                    }
                                }
                                if (earliest.getDominatorDepth() < inputEarliest.getDominatorDepth()) {
                                    earliest = inputEarliest;
                                }
                            }
                        }
                        curBlock = earliest;
                    }
                    assert curBlock != null;
                    addNode(blockToNodes, curBlock, current);
                    nodeToBlock.set(current, curBlock);
                    if (current instanceof FloatingReadNode) {
                        FloatingReadNode floatingReadNode = (FloatingReadNode) current;
                        if (curBlock.canKill(floatingReadNode.getLocationIdentity())) {
                            floatingReads.set(curBlock.getId());
                        }
                    }
                }
            }
        }
    }

    public String printScheduleHelper(String desc) {
        Formatter buf = new Formatter();
        buf.format("=== %s / %s / %s ===%n", getCFG().getStartBlock().getBeginNode().graph(), selectedStrategy, desc);
        for (Block b : getCFG().getBlocks()) {
            buf.format("==== b: %s (loopDepth: %s). ", b, b.getLoopDepth());
            buf.format("dom: %s. ", b.getDominator());
            buf.format("preds: %s. ", b.getPredecessors());
            buf.format("succs: %s ====%n", b.getSuccessors());
            BlockMap<LocationSet> killSets = blockToKillSet;
            if (killSets != null) {
                buf.format("X block kills: %n");
                if (killSets.get(b) != null) {
                    for (LocationIdentity locId : killSets.get(b).getCopyAsList()) {
                        buf.format("X %s killed by %s%n", locId, "dunno anymore");
                    }
                }
            }

            if (blockToNodesMap.get(b) != null) {
                for (Node n : nodesFor(b)) {
                    printNode(n);
                }
            } else {
                for (Node n : b.getNodes()) {
                    printNode(n);
                }
            }
        }
        buf.format("%n");
        return buf.toString();
    }

    private static void printNode(Node n) {
        Formatter buf = new Formatter();
        buf.format("%s", n);
        if (n instanceof MemoryCheckpoint.Single) {
            buf.format(" // kills %s", ((MemoryCheckpoint.Single) n).getLocationIdentity());
        } else if (n instanceof MemoryCheckpoint.Multi) {
            buf.format(" // kills ");
            for (LocationIdentity locid : ((MemoryCheckpoint.Multi) n).getLocationIdentities()) {
                buf.format("%s, ", locid);
            }
        } else if (n instanceof FloatingReadNode) {
            FloatingReadNode frn = (FloatingReadNode) n;
            buf.format(" // from %s", frn.getLocationIdentity());
            buf.format(", lastAccess: %s", frn.getLastLocationAccess());
            buf.format(", address: %s", frn.getAddress());
        } else if (n instanceof GuardNode) {
            buf.format(", anchor: %s", ((GuardNode) n).getAnchor());
        }
        Debug.log("%s", buf);
    }

    public ControlFlowGraph getCFG() {
        return cfg;
    }

    /**
     * Gets the map from each block to the nodes in the block.
     */
    public BlockMap<List<Node>> getBlockToNodesMap() {
        return blockToNodesMap;
    }

    public NodeMap<Block> getNodeToBlockMap() {
        return this.nodeToBlockMap;
    }

    /**
     * Gets the nodes in a given block.
     */
    public List<Node> nodesFor(Block block) {
        return blockToNodesMap.get(block);
    }
}