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 * Copyright (c) 2010, 2013, 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * 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 jdk.nashorn.internal.codegen;

import static jdk.nashorn.internal.codegen.CompilerConstants.SPLIT_PREFIX;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import jdk.nashorn.internal.ir.Block;

import jdk.nashorn.internal.ir.FunctionNode;

import jdk.nashorn.internal.ir.LexicalContext;

import jdk.nashorn.internal.ir.LiteralNode;

import jdk.nashorn.internal.ir.LiteralNode.ArrayLiteralNode;

import jdk.nashorn.internal.ir.Node;

import jdk.nashorn.internal.ir.SplitNode;

import jdk.nashorn.internal.ir.Statement;

import jdk.nashorn.internal.ir.visitor.NodeVisitor;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.logging.DebugLogger;

import jdk.nashorn.internal.runtime.logging.Loggable;

import jdk.nashorn.internal.runtime.logging.Logger;

import jdk.nashorn.internal.runtime.options.Options;

/**

 * Split the IR into smaller compile units.

 */

@Logger(name="splitter")

final class Splitter extends NodeVisitor<LexicalContext> implements Loggable {

    /** Current compiler. */

    private final Compiler compiler;

    /** IR to be broken down. */

    private final FunctionNode outermost;

    /** Compile unit for the main script. */

    private final CompileUnit outermostCompileUnit;

    /** Cache for calculated block weights. */

    private final Map<Node, Long> weightCache = new HashMap<>();

    /** Weight threshold for when to start a split. */

    public static final long SPLIT_THRESHOLD = Options.getIntProperty("nashorn.compiler.splitter.threshold", 32 * 1024);

    private final DebugLogger log;

    /**

     * Constructor.

     *

     * @param compiler              the compiler

     * @param functionNode          function node to split

     * @param outermostCompileUnit  compile unit for outermost function, if non-lazy this is the script's compile unit

     */

    public Splitter(final Compiler compiler, final FunctionNode functionNode, final CompileUnit outermostCompileUnit) {

        super(new LexicalContext());

        this.compiler             = compiler;

        this.outermost            = functionNode;

        this.outermostCompileUnit = outermostCompileUnit;

        this.log                  = initLogger(compiler.getContext());

    }

    @Override

    public DebugLogger initLogger(final Context context) {

        return context.getLogger(this.getClass());

    }

    @Override

    public DebugLogger getLogger() {

        return log;

    }

    /**

     * Execute the split.

     * @param fn the function to split

     * @param top whether this is the topmost compiled function (it's either a program, or we're doing a recompilation).

     */

    FunctionNode split(final FunctionNode fn, final boolean top) {

        FunctionNode functionNode = fn;

        log.fine("Initiating split of '", functionNode.getName(), "'");

        long weight = WeighNodes.weigh(functionNode);

        // We know that our LexicalContext is empty outside the call to functionNode.accept(this) below,

        // so we can pass null to all methods expecting a LexicalContext parameter.

        assert lc.isEmpty() : "LexicalContext not empty";

        if (weight >= SPLIT_THRESHOLD) {

            log.info("Splitting '", functionNode.getName(), "' as its weight ", weight, " exceeds split threshold ", SPLIT_THRESHOLD);

            functionNode = (FunctionNode)functionNode.accept(this);

            if (functionNode.isSplit()) {

                // Weight has changed so weigh again, this time using block weight cache

                weight = WeighNodes.weigh(functionNode, weightCache);

                functionNode = functionNode.setBody(null, functionNode.getBody().setNeedsScope(null));

            }

            if (weight >= SPLIT_THRESHOLD) {

                functionNode = functionNode.setBody(null, splitBlock(functionNode.getBody(), functionNode));

                functionNode = functionNode.setFlag(null, FunctionNode.IS_SPLIT);

                weight = WeighNodes.weigh(functionNode.getBody(), weightCache);

            }

        }

        assert functionNode.getCompileUnit() == null : "compile unit already set for " + functionNode.getName();

        if (top) {

            assert outermostCompileUnit != null : "outermost compile unit is null";

            functionNode = functionNode.setCompileUnit(null, outermostCompileUnit);

            outermostCompileUnit.addWeight(weight + WeighNodes.FUNCTION_WEIGHT);

        } else {

            functionNode = functionNode.setCompileUnit(null, findUnit(weight));

        }

        final Block body = functionNode.getBody();

        final List<FunctionNode> dc = directChildren(functionNode);

        final Block newBody = (Block)body.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

            @Override

            public boolean enterFunctionNode(final FunctionNode nestedFunction) {

                return dc.contains(nestedFunction);

            }

            @Override

            public Node leaveFunctionNode(final FunctionNode nestedFunction) {

                final FunctionNode split = new Splitter(compiler, nestedFunction, outermostCompileUnit).split(nestedFunction, false);

                lc.replace(nestedFunction, split);

                return split;

            }

        });

        functionNode = functionNode.setBody(null, newBody);

        assert functionNode.getCompileUnit() != null;

        return functionNode;

    }

    private static List<FunctionNode> directChildren(final FunctionNode functionNode) {

        final List<FunctionNode> dc = new ArrayList<>();

        functionNode.accept(new NodeVisitor<LexicalContext>(new LexicalContext()) {

            @Override

            public boolean enterFunctionNode(final FunctionNode child) {

                if (child == functionNode) {

                    return true;

                }

                if (lc.getParentFunction(child) == functionNode) {

                    dc.add(child);

                }

                return false;

            }

        });

        return dc;

    }

    /**

     * Override this logic to look up compile units in a different way

     * @param weight weight needed

     * @return compile unit

     */

    protected CompileUnit findUnit(final long weight) {

        return compiler.findUnit(weight);

    }

    /**

     * Split a block into sub methods.

     *

     * @param block Block or function to split.

     *

     * @return new weight for the resulting block.

     */

    private Block splitBlock(final Block block, final FunctionNode function) {

        final List<Statement> splits = new ArrayList<>();

        List<Statement> statements = new ArrayList<>();

        long statementsWeight = 0;

        for (final Statement statement : block.getStatements()) {

            final long weight = WeighNodes.weigh(statement, weightCache);

            if (statementsWeight + weight >= SPLIT_THRESHOLD || statement.isTerminal()) {

                if (!statements.isEmpty()) {

                    splits.add(createBlockSplitNode(block, function, statements, statementsWeight));

                    statements = new ArrayList<>();

                    statementsWeight = 0;

                }

            }

            if (statement.isTerminal()) {

                splits.add(statement);

            } else {

                statements.add(statement);

                statementsWeight += weight;

            }

        }

        if (!statements.isEmpty()) {

            splits.add(createBlockSplitNode(block, function, statements, statementsWeight));

        }

        return block.setStatements(lc, splits);

    }

    /**

     * Create a new split node from statements contained in a parent block.

     *

     * @param parent     Parent block.

     * @param statements Statements to include.

     *

     * @return New split node.

     */

    private SplitNode createBlockSplitNode(final Block parent, final FunctionNode function, final List<Statement> statements, final long weight) {

        final long   token      = parent.getToken();

        final int    finish     = parent.getFinish();

        final String name       = function.uniqueName(SPLIT_PREFIX.symbolName());

        final Block newBlock = new Block(token, finish, statements);

        return new SplitNode(name, newBlock, compiler.findUnit(weight + WeighNodes.FUNCTION_WEIGHT));

    }

    @Override

    public boolean enterBlock(final Block block) {

        if (block.isCatchBlock()) {

            return false;

        }

        final long weight = WeighNodes.weigh(block, weightCache);

        if (weight < SPLIT_THRESHOLD) {

            weightCache.put(block, weight);

            return false;

        }

        return true;

    }

    @Override

    public Node leaveBlock(final Block block) {

        assert !block.isCatchBlock();

        Block newBlock = block;

        // Block was heavier than SLIT_THRESHOLD in enter, but a sub-block may have

        // been split already, so weigh again before splitting.

        long weight = WeighNodes.weigh(block, weightCache);

        if (weight >= SPLIT_THRESHOLD) {

            final FunctionNode currentFunction = lc.getCurrentFunction();

            newBlock = splitBlock(block, currentFunction);

            weight   = WeighNodes.weigh(newBlock, weightCache);

            lc.setFlag(currentFunction, FunctionNode.IS_SPLIT);

        }

        weightCache.put(newBlock, weight);

        return newBlock;

    }

    @SuppressWarnings("rawtypes")

    @Override

    public Node leaveLiteralNode(final LiteralNode literal) {

        long weight = WeighNodes.weigh(literal);

        if (weight < SPLIT_THRESHOLD) {

            return literal;

        }

        final FunctionNode functionNode = lc.getCurrentFunction();

        lc.setFlag(functionNode, FunctionNode.IS_SPLIT);

        if (literal instanceof ArrayLiteralNode) {

            final ArrayLiteralNode arrayLiteralNode = (ArrayLiteralNode) literal;

            final Node[]           value            = arrayLiteralNode.getValue();

            final int[]            postsets         = arrayLiteralNode.getPostsets();

            long totalWeight = 0;

            int  lo          = 0;

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

                final int  postset = postsets[i];

                final Node element = value[postset];

                weight = WeighNodes.weigh(element);

                totalWeight += WeighNodes.AASTORE_WEIGHT + weight;

                if (totalWeight >= SPLIT_THRESHOLD) {

                    final CompileUnit unit = compiler.findUnit(totalWeight - weight);

                    lo = i;

                    totalWeight = weight;

                }

            }

            if (lo != postsets.length) {

                final CompileUnit unit = compiler.findUnit(totalWeight);

            }

        }

        return literal;

    }

    @Override

    public boolean enterFunctionNode(final FunctionNode node) {

        //only go into the function node for this splitter. any subfunctions are rejected

        return node == outermost;

    }

}