/*

 * Copyright (c) 2015, 2017, Oracle and/or its affiliates. All rights reserved.

 */

/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/*

 * $Id: MethodGenerator.java,v 1.2.4.1 2005/09/05 11:16:47 pvedula Exp $

 */

package com.sun.org.apache.xalan.internal.xsltc.compiler.util;

import com.sun.org.apache.bcel.internal.Const;

import com.sun.org.apache.bcel.internal.classfile.Field;

import com.sun.org.apache.bcel.internal.classfile.Method;

import com.sun.org.apache.bcel.internal.generic.ALOAD;

import com.sun.org.apache.bcel.internal.generic.ASTORE;

import com.sun.org.apache.bcel.internal.generic.BranchHandle;

import com.sun.org.apache.bcel.internal.generic.BranchInstruction;

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;

import com.sun.org.apache.bcel.internal.generic.DLOAD;

import com.sun.org.apache.bcel.internal.generic.DSTORE;

import com.sun.org.apache.bcel.internal.generic.FLOAD;

import com.sun.org.apache.bcel.internal.generic.FSTORE;

import com.sun.org.apache.bcel.internal.generic.GETFIELD;

import com.sun.org.apache.bcel.internal.generic.GOTO;

import com.sun.org.apache.bcel.internal.generic.ICONST;

import com.sun.org.apache.bcel.internal.generic.ILOAD;

import com.sun.org.apache.bcel.internal.generic.INVOKEINTERFACE;

import com.sun.org.apache.bcel.internal.generic.INVOKESPECIAL;

import com.sun.org.apache.bcel.internal.generic.INVOKESTATIC;

import com.sun.org.apache.bcel.internal.generic.INVOKEVIRTUAL;

import com.sun.org.apache.bcel.internal.generic.ISTORE;

import com.sun.org.apache.bcel.internal.generic.IfInstruction;

import com.sun.org.apache.bcel.internal.generic.IndexedInstruction;

import com.sun.org.apache.bcel.internal.generic.Instruction;

import com.sun.org.apache.bcel.internal.generic.InstructionConst;

import com.sun.org.apache.bcel.internal.generic.InstructionHandle;

import com.sun.org.apache.bcel.internal.generic.InstructionList;

import com.sun.org.apache.bcel.internal.generic.InstructionTargeter;

import com.sun.org.apache.bcel.internal.generic.LLOAD;

import com.sun.org.apache.bcel.internal.generic.LSTORE;

import com.sun.org.apache.bcel.internal.generic.LocalVariableGen;

import com.sun.org.apache.bcel.internal.generic.LocalVariableInstruction;

import com.sun.org.apache.bcel.internal.generic.MethodGen;

import com.sun.org.apache.bcel.internal.generic.NEW;

import com.sun.org.apache.bcel.internal.generic.PUTFIELD;

import com.sun.org.apache.bcel.internal.generic.RET;

import com.sun.org.apache.bcel.internal.generic.Select;

import com.sun.org.apache.bcel.internal.generic.TargetLostException;

import com.sun.org.apache.bcel.internal.generic.Type;

import com.sun.org.apache.xalan.internal.xsltc.compiler.Pattern;

import com.sun.org.apache.xalan.internal.xsltc.compiler.XSLTC;

import java.util.ArrayList;

import java.util.Collections;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Stack;

/**

 * @author Jacek Ambroziak

 * @author Santiago Pericas-Geertsen

 * @LastModified: Nov 2017

 */

public class MethodGenerator extends MethodGen

    implements com.sun.org.apache.xalan.internal.xsltc.compiler.Constants {

    protected static final int INVALID_INDEX   = -1;

    private static final String START_ELEMENT_SIG

        = "(" + STRING_SIG + ")V";

    private static final String END_ELEMENT_SIG

        = START_ELEMENT_SIG;

    private static final int DOM_INDEX       = 1;

    private static final int ITERATOR_INDEX  = 2;

    private static final int HANDLER_INDEX   = 3;

    private static final int MAX_METHOD_SIZE = 65535;

    private static final int MAX_BRANCH_TARGET_OFFSET = 32767;

    private static final int MIN_BRANCH_TARGET_OFFSET = -32768;

    private static final int TARGET_METHOD_SIZE = 60000;

    private static final int MINIMUM_OUTLINEABLE_CHUNK_SIZE = 1000;

    private Instruction       _iloadCurrent;

    private Instruction       _istoreCurrent;

    private final Instruction _astoreHandler;

    private final Instruction _aloadHandler;

    private final Instruction _astoreIterator;

    private final Instruction _aloadIterator;

    private final Instruction _aloadDom;

    private final Instruction _astoreDom;

    private final Instruction _startElement;

    private final Instruction _endElement;

    private final Instruction _startDocument;

    private final Instruction _endDocument;

    private final Instruction _attribute;

    private final Instruction _uniqueAttribute;

    private final Instruction _namespace;

    private final Instruction _setStartNode;

    private final Instruction _reset;

    private final Instruction _nextNode;

    private SlotAllocator _slotAllocator;

    private boolean _allocatorInit = false;

    private LocalVariableRegistry _localVariableRegistry;

        /**

                 * A mapping between patterns and instruction lists used by

                 * test sequences to avoid compiling the same pattern multiple

                 * times. Note that patterns whose kernels are "*", "node()"

                 * and "@*" can between shared by test sequences.

                 */

        private Map<Pattern, InstructionList> _preCompiled = new HashMap<>();

    public MethodGenerator(int access_flags, Type return_type,

                           Type[] arg_types, String[] arg_names,

                           String method_name, String class_name,

                           InstructionList il, ConstantPoolGen cpg) {

        super(access_flags, return_type, arg_types, arg_names, method_name,

              class_name, il, cpg);

        _astoreHandler  = new ASTORE(HANDLER_INDEX);

        _aloadHandler   = new ALOAD(HANDLER_INDEX);

        _astoreIterator = new ASTORE(ITERATOR_INDEX);

        _aloadIterator  = new ALOAD(ITERATOR_INDEX);

        _aloadDom       = new ALOAD(DOM_INDEX);

        _astoreDom      = new ASTORE(DOM_INDEX);

        final int startElement =

            cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                      "startElement",

                                      START_ELEMENT_SIG);

        _startElement = new INVOKEINTERFACE(startElement, 2);

        final int endElement =

            cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                      "endElement",

                                      END_ELEMENT_SIG);

        _endElement = new INVOKEINTERFACE(endElement, 2);

        final int attribute =

            cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                      "addAttribute",

                                      "("

                                      + STRING_SIG

                                      + STRING_SIG

                                      + ")V");

        _attribute = new INVOKEINTERFACE(attribute, 3);

        final int uniqueAttribute =

            cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                      "addUniqueAttribute",

                                      "("

                                      + STRING_SIG

                                      + STRING_SIG

                                      + "I)V");

        _uniqueAttribute = new INVOKEINTERFACE(uniqueAttribute, 4);

        final int namespace =

            cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                      "namespaceAfterStartElement",

                                      "("

                                      + STRING_SIG

                                      + STRING_SIG

                                      + ")V");

        _namespace = new INVOKEINTERFACE(namespace, 3);

        int index = cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                              "startDocument",

                                              "()V");

        _startDocument = new INVOKEINTERFACE(index, 1);

        index = cpg.addInterfaceMethodref(TRANSLET_OUTPUT_INTERFACE,

                                          "endDocument",

                                          "()V");

        _endDocument = new INVOKEINTERFACE(index, 1);

        index = cpg.addInterfaceMethodref(NODE_ITERATOR,

                                          SET_START_NODE,

                                          SET_START_NODE_SIG);

        _setStartNode = new INVOKEINTERFACE(index, 2);

        index = cpg.addInterfaceMethodref(NODE_ITERATOR,

                                          "reset", "()"+NODE_ITERATOR_SIG);

        _reset = new INVOKEINTERFACE(index, 1);

        index = cpg.addInterfaceMethodref(NODE_ITERATOR, NEXT, NEXT_SIG);

        _nextNode = new INVOKEINTERFACE(index, 1);

        _slotAllocator = new SlotAllocator();

        _slotAllocator.initialize(getLocalVariableRegistry().getLocals(false));

        _allocatorInit = true;

    }

    /**

     * Allocates a local variable. If the slot allocator has already been

     * initialized, then call addLocalVariable2() so that the new variable

     * is known to the allocator. Failing to do this may cause the allocator

     * to return a slot that is already in use.

     */

    public LocalVariableGen addLocalVariable(String name, Type type,

                                             InstructionHandle start,

                                             InstructionHandle end)

    {

        LocalVariableGen lvg;

        if (_allocatorInit) {

            lvg = addLocalVariable2(name, type, start);

        } else {

            lvg = super.addLocalVariable(name, type, start, end);

            getLocalVariableRegistry().registerLocalVariable(lvg);

        }

        return lvg;

    }

    public LocalVariableGen addLocalVariable2(String name, Type type,

                                              InstructionHandle start)

    {

        LocalVariableGen lvg = super.addLocalVariable(name, type,

                                              _slotAllocator.allocateSlot(type),

                                              start, null);

        getLocalVariableRegistry().registerLocalVariable(lvg);

        return lvg;

    }

    private LocalVariableRegistry getLocalVariableRegistry() {

        if (_localVariableRegistry == null) {

            _localVariableRegistry = new LocalVariableRegistry();

        }

        return _localVariableRegistry;

    }

    /**

     * Keeps track of all local variables used in the method.

     * <p>The

     * {@link MethodGen#addLocalVariable(String,Type,InstructionHandle,InstructionHandle)}</code>

     * and

     * {@link MethodGen#addLocalVariable(String,Type,int,InstructionHandle,InstructionHandle)}</code>

     * methods of {@link MethodGen} will only keep track of

     * {@link LocalVariableGen} object until it'ss removed by a call to

     * {@link MethodGen#removeLocalVariable(LocalVariableGen)}.</p>

     * <p>In order to support efficient copying of local variables to outlined

     * methods by

     * {@link #outline(InstructionHandle,InstructionHandle,String,ClassGenerator)},

     * this class keeps track of all local variables defined by the method.</p>

     */

    protected class LocalVariableRegistry {

        /**

         * <p>A <code>java.lang.List</code> of all

         * {@link LocalVariableGen}s created for this method, indexed by the

         * slot number of the local variable.  The JVM stack frame of local

         * variables is divided into "slots".  A single slot can be used to

         * store more than one variable in a method, without regard to type, so

         * long as the byte code keeps the ranges of the two disjoint.</p>

         * <p>If only one registration of use of a particular slot occurs, the

         * corresponding entry of <code>_variables</code> contains the

         * <code>LocalVariableGen</code>; if more than one occurs, the

         * corresponding entry contains all such <code>LocalVariableGen</code>s

         * registered for the same slot; and if none occurs, the entry will be

         * <code>null</code>.

         */

        protected List<Object> _variables = new ArrayList<>();

        /**

         * Maps a name to a {@link LocalVariableGen}

         */

        protected Map<String, Object> _nameToLVGMap = new HashMap<>();

        /**

         * Registers a {@link org.apache.bcel.generic.LocalVariableGen}

         * for this method.

         * <p><b>Preconditions:</b>

         * <ul>

         * <li>The range of instructions for <code>lvg</code> does not

         * overlap with the range of instructions for any

         * <code>LocalVariableGen</code> with the same slot index previously

         * registered for this method.  <b><em>(Unchecked.)</em></b></li>

         * </ul></p>

         * @param lvg The variable to be registered

         */

        @SuppressWarnings("unchecked")

        protected void registerLocalVariable(LocalVariableGen lvg) {

            int slot = lvg.getIndex();

            int registrySize = _variables.size();

            // If the LocalVariableGen uses a slot index beyond any previously

            // encountered, expand the _variables, padding with intervening null

            // entries as required.

            if (slot >= registrySize) {

                for (int i = registrySize; i < slot; i++) {

                    _variables.add(null);

                }

                _variables.add(lvg);

            } else {

                // If the LocalVariableGen reuses a slot, make sure the entry

                // in _variables contains an ArrayList and add the newly

                // registered LocalVariableGen to the list.  If the entry in

                // _variables just contains null padding, store the

                // LocalVariableGen directly.

                Object localsInSlot = _variables.get(slot);

                if (localsInSlot != null) {

                    if (localsInSlot instanceof LocalVariableGen) {

                        List<LocalVariableGen> listOfLocalsInSlot = new ArrayList<>();

                        listOfLocalsInSlot.add((LocalVariableGen)localsInSlot);

                        listOfLocalsInSlot.add(lvg);

                        _variables.set(slot, listOfLocalsInSlot);

                    } else {

                        ((List<LocalVariableGen>) localsInSlot).add(lvg);

                    }

                } else {

                    _variables.set(slot, lvg);

                }

            }

            registerByName(lvg);

        }

        /**

         * <p>Find which {@link LocalVariableGen}, if any, is registered for a

         * particular JVM local stack frame slot at a particular position in the

         * byte code for the method.</p>

         * <p><b>Preconditions:</b>

         * <ul>

         * <li>The {@link InstructionList#setPositions()} has been called for

         * the {@link InstructionList} associated with this

         * {@link MethodGenerator}.</li>

         * </ul></p>

         * @param slot the JVM local stack frame slot number

         * @param offset the position in the byte code

         * @return the <code>LocalVariableGen</code> for the local variable

         * stored in the relevant slot at the relevant offset; <code>null</code>

         * if there is none.

         */

        protected LocalVariableGen lookupRegisteredLocalVariable(int slot,

                                                                 int offset) {

            Object localsInSlot = (_variables != null) ? _variables.get(slot)

                                                       : null;

            // If this slot index was never used, _variables.get will return

            // null; if it was used once, it will return the LocalVariableGen;

            // more than once it will return an ArrayList of all the

            // LocalVariableGens for variables stored in that slot.  For each

            // LocalVariableGen, check whether its range includes the

            // specified offset, and return the first such encountered.

            if (localsInSlot != null) {

                if (localsInSlot instanceof LocalVariableGen) {

                    LocalVariableGen lvg = (LocalVariableGen)localsInSlot;

                    if (offsetInLocalVariableGenRange(lvg, offset)) {

                        return lvg;

                    }

                } else {

                    @SuppressWarnings("unchecked")

                    List<LocalVariableGen> listOfLocalsInSlot =

                            (List<LocalVariableGen>) localsInSlot;

                    for (LocalVariableGen lvg : listOfLocalsInSlot) {

                        if (offsetInLocalVariableGenRange(lvg, offset)) {

                            return lvg;

                        }

                    }

                }

            }

            // No local variable stored in the specified slot at the specified

            return null;

        }

        /**

         * <p>Set up a mapping of the name of the specified

         * {@link LocalVariableGen} object to the <code>LocalVariableGen</code>

         * itself.</p>

         * <p>This is a bit of a hack.  XSLTC is relying on the fact that the

         * name that is being looked up won't be duplicated, which isn't

         * guaranteed.  It replaces code which used to call

         * {@link MethodGen#getLocalVariables()} and looped through the

         * <code>LocalVariableGen</code> objects it contained to find the one

         * with the specified name.  However, <code>getLocalVariables()</code>

         * has the side effect of setting the start and end for any

         * <code>LocalVariableGen</code> which did not already have them

         * set, which causes problems for outlining..</p>

         * <p>See also {@link #lookUpByName(String)} and

         * {@link #removeByNameTracking(LocalVariableGen)}</P

         * @param lvg a <code>LocalVariableGen</code>

         */

        @SuppressWarnings("unchecked")

        protected void registerByName(LocalVariableGen lvg) {

            Object duplicateNameEntry = _nameToLVGMap.get(lvg.getName());

            if (duplicateNameEntry == null) {

                _nameToLVGMap.put(lvg.getName(), lvg);

            } else {

                List<LocalVariableGen> sameNameList;

                if (duplicateNameEntry instanceof ArrayList) {

                    sameNameList = (List<LocalVariableGen>)duplicateNameEntry;

                    sameNameList.add(lvg);

                } else {

                    sameNameList = new ArrayList<>();

                    sameNameList.add((LocalVariableGen)duplicateNameEntry);

                    sameNameList.add(lvg);

                }

                _nameToLVGMap.put(lvg.getName(), sameNameList);

            }

        }

        /**

         * Remove the mapping from the name of the specified

         * {@link LocalVariableGen} to itself.

         * See also {@link #registerByName(LocalVariableGen)} and

         * {@link #lookUpByName(String)}

         * @param lvg a <code>LocalVariableGen</code>

         */

        @SuppressWarnings("unchecked")

        protected void removeByNameTracking(LocalVariableGen lvg) {

            Object duplicateNameEntry = _nameToLVGMap.get(lvg.getName());

            if (duplicateNameEntry instanceof ArrayList) {

                List<LocalVariableGen> sameNameList =

                        (List<LocalVariableGen>)duplicateNameEntry;

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

                    if (sameNameList.get(i) == lvg) {

                        sameNameList.remove(i);

                        break;

                    }

                }

            } else {

                _nameToLVGMap.remove(lvg);

            }

        }

        /**

         * <p>Given the name of a variable, finds a {@link LocalVariableGen}

         * corresponding to it.</p>

         * <p>See also {@link #registerByName(LocalVariableGen)} and

         * {@link #removeByNameTracking(LocalVariableGen)}</p>

         * @param name

         * @return

         */

        @SuppressWarnings("unchecked")

        protected LocalVariableGen lookUpByName(String name) {

            LocalVariableGen lvg = null;

            Object duplicateNameEntry = _nameToLVGMap.get(name);

            if (duplicateNameEntry instanceof ArrayList) {

                List<LocalVariableGen> sameNameList =

                        (List<LocalVariableGen>)duplicateNameEntry;

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

                    lvg = sameNameList.get(i);

                    if (lvg.getName() == null ? name == null : lvg.getName().equals(name)) {

                        break;

                    }

                }

            } else {

                lvg = (LocalVariableGen) duplicateNameEntry;

            }

            return lvg;

        }

        /**

         * <p>Gets all {@link LocalVariableGen} objects for this method.</p>

         * <p>When the <code>includeRemoved</code> argument has the value

         * <code>false</code>, this method replaces uses of

         * {@link MethodGen#getLocalVariables()} which has

         * a side-effect of setting the start and end range for any

         * <code>LocalVariableGen</code> if either was <code>null</code>.  That

         * side-effect causes problems for outlining of code in XSLTC.

         * @param includeRemoved Specifies whether all local variables ever

         * declared should be returned (<code>true</code>) or only those not

         * removed (<code>false</code>)

         * @return an array of <code>LocalVariableGen</code> containing all the

         * local variables

         */

        @SuppressWarnings("unchecked")

        protected LocalVariableGen[] getLocals(boolean includeRemoved) {

            LocalVariableGen[] locals = null;

            List<LocalVariableGen> allVarsEverDeclared = new ArrayList<>();

            if (includeRemoved) {

                int slotCount = allVarsEverDeclared.size();

                for (int i = 0; i < slotCount; i++) {

                    Object slotEntries = _variables.get(i);

                    if (slotEntries != null) {

                        if (slotEntries instanceof ArrayList) {

                            List<LocalVariableGen> slotList =

                                    (List<LocalVariableGen>)slotEntries;

                            for (int j = 0; j < slotList.size(); j++) {

                                allVarsEverDeclared.add(slotList.get(i));

                            }

                        } else {

                            allVarsEverDeclared.add((LocalVariableGen)slotEntries);

                        }

                    }

                }

            } else {

                for (Map.Entry<String, Object> nameVarsPair : _nameToLVGMap.entrySet()) {

                    Object vars = nameVarsPair.getValue();

                    if (vars != null) {

                        if (vars instanceof ArrayList) {

                            List<LocalVariableGen> varsList =

                                    (List<LocalVariableGen>) vars;

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

                                allVarsEverDeclared.add(varsList.get(i));

                            }

                        } else {

                            allVarsEverDeclared.add((LocalVariableGen)vars);

                        }

                    }

                }

            }

            locals = new LocalVariableGen[allVarsEverDeclared.size()];

            allVarsEverDeclared.toArray(locals);

            return locals;

        }

    }

    /**

     * Determines whether a particular variable is in use at a particular offset

     * in the byte code for this method.

     * <p><b>Preconditions:</b>

     * <ul>

     * <li>The {@link InstructionList#setPositions()} has been called for the

     * {@link InstructionList} associated with this {@link MethodGenerator}.

     * </li></ul></p>

     * @param lvg the {@link LocalVariableGen} for the variable

     * @param offset the position in the byte code

     * @return <code>true</code> if and only if the specified variable is in

     * use at the particular byte code offset.

     */

    boolean offsetInLocalVariableGenRange(LocalVariableGen lvg, int offset) {

        InstructionHandle lvgStart = lvg.getStart();

        InstructionHandle lvgEnd = lvg.getEnd();

        // If no start handle is recorded for the LocalVariableGen, it is

        // assumed to be in use from the beginning of the method.

        if (lvgStart == null) {

            lvgStart = getInstructionList().getStart();

        }

        // If no end handle is recorded for the LocalVariableGen, it is assumed

        // to be in use to the end of the method.

        if (lvgEnd == null) {

            lvgEnd = getInstructionList().getEnd();

        }

        // Does the range of the instruction include the specified offset?

        // Note that the InstructionHandle.getPosition method returns the

        // offset of the beginning of an instruction.  A LocalVariableGen's

        // range includes the end instruction itself, so that instruction's

        // length must be taken into consideration in computing whether the

        // varible is in range at a particular offset.

        return ((lvgStart.getPosition() <= offset)

                    && (lvgEnd.getPosition()

                            + lvgEnd.getInstruction().getLength() >= offset));

    }

    public void removeLocalVariable(LocalVariableGen lvg) {

        _slotAllocator.releaseSlot(lvg);

        getLocalVariableRegistry().removeByNameTracking(lvg);

        super.removeLocalVariable(lvg);

    }

    public Instruction loadDOM() {

        return _aloadDom;

    }

    public Instruction storeDOM() {

        return _astoreDom;

    }

    public Instruction storeHandler() {

        return _astoreHandler;

    }

    public Instruction loadHandler() {

        return _aloadHandler;

    }

    public Instruction storeIterator() {

        return _astoreIterator;

    }

    public Instruction loadIterator() {

        return _aloadIterator;

    }

    public final Instruction setStartNode() {

        return _setStartNode;

    }

    public final Instruction reset() {

        return _reset;

    }

    public final Instruction nextNode() {

        return _nextNode;

    }

    public final Instruction startElement() {

        return _startElement;

    }

    public final Instruction endElement() {

        return _endElement;

    }

    public final Instruction startDocument() {

        return _startDocument;

    }

    public final Instruction endDocument() {

        return _endDocument;

    }

    public final Instruction attribute() {

        return _attribute;

    }

    public final Instruction uniqueAttribute() {

        return _uniqueAttribute;

    }

    public final Instruction namespace() {

        return _namespace;

    }

    public Instruction loadCurrentNode() {

        if (_iloadCurrent == null) {

            int idx = getLocalIndex("current");

            if (idx > 0)

                _iloadCurrent = new ILOAD(idx);

            else

                _iloadCurrent = new ICONST(0);

        }

        return _iloadCurrent;

    }

    public Instruction storeCurrentNode() {

        return _istoreCurrent != null

            ? _istoreCurrent

            : (_istoreCurrent = new ISTORE(getLocalIndex("current")));

    }

    /** by default context node is the same as current node. MK437 */

    public Instruction loadContextNode() {

        return loadCurrentNode();

    }

    public Instruction storeContextNode() {

        return storeCurrentNode();

    }

    public int getLocalIndex(String name) {

        return getLocalVariable(name).getIndex();

    }

    public LocalVariableGen getLocalVariable(String name) {

        return getLocalVariableRegistry().lookUpByName(name);

    }

    public void setMaxLocals() {

        // Get the current number of local variable slots

        int maxLocals = super.getMaxLocals();

        int prevLocals = maxLocals;

        // Get numer of actual variables

        final LocalVariableGen[] localVars = super.getLocalVariables();

        if (localVars != null) {

            if (localVars.length > maxLocals)

                maxLocals = localVars.length;

        }

        // We want at least 5 local variable slots (for parameters)

        if (maxLocals < 5) maxLocals = 5;

        super.setMaxLocals(maxLocals);

    }

    /**

     * Add a pre-compiled pattern to this mode.

     */

    public void addInstructionList(Pattern pattern, InstructionList ilist) {

        _preCompiled.put(pattern, ilist);

    }

    /**

     * Get the instruction list for a pre-compiled pattern. Used by

     * test sequences to avoid compiling patterns more than once.

     */

    public InstructionList getInstructionList(Pattern pattern) {

        return _preCompiled.get(pattern);

    }

    /**

     * Used to keep track of an outlineable chunk of instructions in the

     * current method.  See {@link OutlineableChunkStart} and

     * {@link OutlineableChunkEnd} for more information.

     */

    private class Chunk implements Comparable<Object> {

        /**

         * {@link InstructionHandle} of the first instruction in the outlineable

         * chunk.

         */

        private InstructionHandle m_start;

        /**

         * {@link org.apache.bcel.generic.InstructionHandle} of the first

         * instruction in the outlineable chunk.

         */

        private InstructionHandle m_end;

        /**

         * Number of bytes in the instructions contained in this outlineable

         * chunk.

         */

        private int m_size;

        /**

         * <p>Constructor for an outlineable {@link MethodGenerator.Chunk}.</p>

         * <p><b>Preconditions:</b>

         * <ul>

         * <li>The {@link InstructionList#setPositions()} has been called for

         * the {@link InstructionList} associated with this

         * {@link MethodGenerator}.</li>

         * </ul></p>

         * @param start The {@link InstructionHandle} of the first

         *              instruction in the outlineable chunk.

         * @param end The {@link InstructionHandle} of the last

         *            instruction in the outlineable chunk.

         */

        Chunk(InstructionHandle start, InstructionHandle end) {

            m_start = start;

            m_end = end;

            m_size = end.getPosition() - start.getPosition();

        }

        /**

         * Determines whether this outlineable {@link MethodGenerator.Chunk} is

         * followed immediately by the argument

         * <code>MethodGenerator.Chunk</code>, with no other intervening

         * instructions, including {@link OutlineableChunkStart} or

         * {@link OutlineableChunkEnd} instructions.

         * @param neighbour an outlineable {@link MethodGenerator.Chunk}

         * @return <code>true</code> if and only if the argument chunk

         * immediately follows <code>this</code> chunk

         */

        boolean isAdjacentTo(Chunk neighbour) {

            return getChunkEnd().getNext() == neighbour.getChunkStart();

        }

        /**

         * Getter method for the start of this {@linke MethodGenerator.Chunk}

         * @return the {@link org.apache.bcel.generic.InstructionHandle} of the

         * start of this chunk

         */

        InstructionHandle getChunkStart() {

            return m_start;

        }

        /**

         * Getter method for the end of this {@link MethodGenerator.Chunk}

         * @return the {@link InstructionHandle} of the start of this chunk

         */

        InstructionHandle getChunkEnd() {

            return m_end;

        }

        /**

         * The size of this {@link MethodGenerator.Chunk}

         * @return the number of bytes in the byte code represented by this

         *         chunk.

         */

        int getChunkSize() {

            return m_size;

        }

        /**

         * Implements the <code>java.util.Comparable.compareTo(Object)</code>

         * method.

         * @return

         * <ul>

         * <li>A positive <code>int</code> if the length of <code>this</code>

         * chunk in bytes is greater than that of <code>comparand</code></li>

         * <li>A negative <code>int</code> if the length of <code>this</code>

         * chunk in bytes is less than that of <code>comparand</code></li>

         * <li>Zero, otherwise.</li>

         * </ul>

         */

        public int compareTo(Object comparand) {

            return getChunkSize() - ((Chunk)comparand).getChunkSize();

        }

    }

    /**

     * Find the outlineable chunks in this method that would be the best choices

     * to outline, based on size and position in the method.

     * @param classGen The {@link ClassGen} with which the generated methods

     *                 will be associated

     * @param totalMethodSize the size of the bytecode in the original method

     * @return a <code>java.util.List</code> containing the

     *  {@link MethodGenerator.Chunk}s that may be outlined from this method

     */

    private List<Chunk> getCandidateChunks(ClassGenerator classGen,

                                         int totalMethodSize) {

        Iterator<InstructionHandle> instructions = getInstructionList().iterator();

        List<Chunk> candidateChunks = new ArrayList<>();

        List<InstructionHandle> currLevelChunks = new ArrayList<>();

        Stack<List<InstructionHandle>> subChunkStack = new Stack<>();

        boolean openChunkAtCurrLevel = false;

        boolean firstInstruction = true;

        InstructionHandle currentHandle;

        if (m_openChunks != 0) {

            String msg =

                (new ErrorMsg(ErrorMsg.OUTLINE_ERR_UNBALANCED_MARKERS))

                    .toString();

            throw new InternalError(msg);

        }

        // Scan instructions in the method, keeping track of the nesting level

        // of outlineable chunks.

        //

        // currLevelChunks

        //     keeps track of the child chunks of a chunk.  For each chunk,

        //     there will be a pair of entries:  the InstructionHandles for the

        //     start and for the end of the chunk

        // subChunkStack

        //     a stack containing the partially accumulated currLevelChunks for

        //     each chunk that's still open at the current position in the

        //     InstructionList.

        // candidateChunks

        //     the list of chunks which have been accepted as candidates chunks

        //     for outlining

        do {

            // Get the next instruction.  The loop will perform one extra

            // iteration after it reaches the end of the InstructionList, with

            // currentHandle set to null.

            currentHandle = instructions.hasNext()

                                    ? instructions.next()

                                    : null;

            Instruction inst =

                    (currentHandle != null) ? currentHandle.getInstruction()

                                            : null;

            // At the first iteration, create a chunk representing all the

            // code in the method.  This is done just to simplify the logic -

            // this chunk can never be outlined because it will be too big.

            if (firstInstruction) {

                openChunkAtCurrLevel = true;

                currLevelChunks.add(currentHandle);

                firstInstruction = false;

            }

            // Found a new chunk

            if (inst instanceof OutlineableChunkStart) {

                // If last MarkerInstruction encountered was an

                // OutlineableChunkStart, this represents the first chunk

                // nested within that previous chunk - push the list of chunks

                // from the outer level onto the stack

                if (openChunkAtCurrLevel) {

                    subChunkStack.push(currLevelChunks);

                    currLevelChunks = new ArrayList<>();

                }

                openChunkAtCurrLevel = true;

                currLevelChunks.add(currentHandle);

            // Close off an open chunk

            } else if (currentHandle == null

                           || inst instanceof OutlineableChunkEnd) {

                List<InstructionHandle> nestedSubChunks = null;

                // If the last MarkerInstruction encountered was an

                // OutlineableChunkEnd, it means that the current instruction

                // marks the end of a chunk that contained child chunks.

                // Those children might need to be examined below in case they

                // are better candidates for outlining than the current chunk.

                if (!openChunkAtCurrLevel) {

                    nestedSubChunks = currLevelChunks;

                    currLevelChunks = subChunkStack.pop();

                }

                // Get the handle for the start of this chunk (the last entry

                // in currLevelChunks)

                InstructionHandle chunkStart =

                        currLevelChunks.get(currLevelChunks.size()-1);

                int chunkEndPosition =

                        (currentHandle != null) ? currentHandle.getPosition()

                                                : totalMethodSize;

                int chunkSize = chunkEndPosition - chunkStart.getPosition();

                // Two ranges of chunk size to consider:

                //

                // 1. [0,TARGET_METHOD_SIZE]

                //      Keep this chunk in consideration as a candidate,

                //      and ignore its subchunks, if any - there's nothing to be

                //      gained by outlining both the current chunk and its

                //      children!

                //

                // 2. (TARGET_METHOD_SIZE,+infinity)

                //      Ignore this chunk - it's too big.  Add its subchunks

                //      as candidates, after merging adjacent chunks to produce

                //      chunks that are as large as possible

                if (chunkSize <= TARGET_METHOD_SIZE) {

                    currLevelChunks.add(currentHandle);

                } else {

                    if (!openChunkAtCurrLevel) {

                        int childChunkCount = nestedSubChunks.size() / 2;

                        if (childChunkCount > 0) {

                            Chunk[] childChunks = new Chunk[childChunkCount];

                            // Gather all the child chunks of the current chunk

                            for (int i = 0; i < childChunkCount; i++) {

                                InstructionHandle start = nestedSubChunks.get(i*2);

                                InstructionHandle end = nestedSubChunks.get(i*2+1);

                                childChunks[i] = new Chunk(start, end);

                            }

                            // Merge adjacent siblings

                            List<Chunk> mergedChildChunks =

                                        mergeAdjacentChunks(childChunks);

                            // Add chunks that mean minimum size requirements

                            // to the list of candidate chunks for outlining

                            for (Chunk mergedChunk : mergedChildChunks) {

                                int mergedSize = mergedChunk.getChunkSize();

                                if (mergedSize >= MINIMUM_OUTLINEABLE_CHUNK_SIZE

                                        && mergedSize <= TARGET_METHOD_SIZE) {

                                    candidateChunks.add(mergedChunk);

                                }

                            }

                        }

                    }

                    // Drop the chunk which was too big

                    currLevelChunks.remove(currLevelChunks.size() - 1);

                }

                // currLevelChunks contains pairs of InstructionHandles.  If

                // its size is an odd number, the loop has encountered the

                // start of a chunk at this level, but not its end.

                openChunkAtCurrLevel = ((currLevelChunks.size() & 0x1) == 1);

            }

        } while (currentHandle != null);

        return candidateChunks;

    }

    /**

     * Merge adjacent sibling chunks to produce larger candidate chunks for

     * outlining

     * @param chunks array of sibling {@link MethodGenerator.Chunk}s that are

     *               under consideration for outlining.  Chunks must be in

     *               the order encountered in the {@link InstructionList}

     * @return a <code>java.util.List</code> of

     *         <code>MethodGenerator.Chunk</code>s maximally merged

     */

    private List<Chunk> mergeAdjacentChunks(Chunk[] chunks) {

        int[] adjacencyRunStart = new int[chunks.length];

        int[] adjacencyRunLength = new int[chunks.length];

        boolean[] chunkWasMerged = new boolean[chunks.length];

        int maximumRunOfChunks = 0;

        int startOfCurrentRun;

        int numAdjacentRuns = 0;

        List<Chunk> mergedChunks = new ArrayList<>();

        startOfCurrentRun = 0;

        // Loop through chunks, and record in adjacencyRunStart where each

        // run of adjacent chunks begins and how many are in that run.  For

        // example, given chunks A B C D E F, if A is adjacent to B, but not

        // to C, and C, D, E and F are all adjacent,

        //   adjacencyRunStart[0] == 0; adjacencyRunLength[0] == 2

        //   adjacencyRunStart[1] == 2; adjacencyRunLength[1] == 4

        for (int i = 1; i < chunks.length; i++) {

            if (!chunks[i-1].isAdjacentTo(chunks[i])) {

                int lengthOfRun = i - startOfCurrentRun;

                // Track the longest run of chunks found

                if (maximumRunOfChunks < lengthOfRun) {

                    maximumRunOfChunks = lengthOfRun;

                }

                if (lengthOfRun > 1 ) {

                    adjacencyRunLength[numAdjacentRuns] = lengthOfRun;

                    adjacencyRunStart[numAdjacentRuns] = startOfCurrentRun;

                    numAdjacentRuns++;

                }

                startOfCurrentRun = i;

            }

        }

        if (chunks.length - startOfCurrentRun > 1) {

            int lengthOfRun = chunks.length - startOfCurrentRun;

            // Track the longest run of chunks found

            if (maximumRunOfChunks < lengthOfRun) {

                maximumRunOfChunks = lengthOfRun;

            }

            adjacencyRunLength[numAdjacentRuns] =

                        chunks.length - startOfCurrentRun;

            adjacencyRunStart[numAdjacentRuns] = startOfCurrentRun;

            numAdjacentRuns++;

        }

        // Try merging adjacent chunks to come up with better sized chunks for

        // outlining.  This algorithm is not optimal, but it should be

        // reasonably fast.  Consider an example like this, where four chunks

        // of the sizes specified in brackets are adjacent.  The best way of

        // combining these chunks would be to merge the first pair and merge

        // the last three to form two chunks, but the algorithm will merge the

        // three in the middle instead, leaving three chunks in all.

        //    [25000] [25000] [20000] [1000] [20000]

        // Start by trying to merge the maximum number of adjacent chunks, and

        // work down from there.

        for (int numToMerge = maximumRunOfChunks; numToMerge>1; numToMerge--) {

            // Look at each run of adjacent chunks

            for (int run = 0; run < numAdjacentRuns; run++) {

                int runStart = adjacencyRunStart[run];

                int runEnd = runStart + adjacencyRunLength[run] - 1;

                boolean foundChunksToMerge = false;

                // Within the current run of adjacent chunks, look at all

                // "subruns" of length numToMerge, until we run out or find

                // a subrun that can be merged.

                for (int mergeStart = runStart;

                     mergeStart+numToMerge-1 <= runEnd && !foundChunksToMerge;

                     mergeStart++) {

                    int mergeEnd = mergeStart + numToMerge - 1;

                    int mergeSize = 0;

                    // Find out how big the subrun is

                    for (int j = mergeStart; j <= mergeEnd; j++) {

                        mergeSize = mergeSize + chunks[j].getChunkSize();

                    }

                    // If the current subrun is small enough to outline,

                    // merge it, and split the remaining chunks in the run

                    if (mergeSize <= TARGET_METHOD_SIZE) {

                        foundChunksToMerge = true;

                        for (int j = mergeStart; j <= mergeEnd; j++) {

                            chunkWasMerged[j] = true;

                        }

                        mergedChunks.add(

                                new Chunk(chunks[mergeStart].getChunkStart(),

                                          chunks[mergeEnd].getChunkEnd()));

                        // Adjust the length of the current run of adjacent

                        // chunks to end at the newly merged chunk...

                        adjacencyRunLength[run] =

                                adjacencyRunStart[run] - mergeStart;

                        int trailingRunLength = runEnd - mergeEnd;

                        // and any chunks that follow the newly merged chunk

                        // in the current run of adjacent chunks form another

                        // new run of adjacent chunks

                        if (trailingRunLength >= 2) {

                            adjacencyRunStart[numAdjacentRuns] = mergeEnd + 1;

                            adjacencyRunLength[numAdjacentRuns] =

                                                            trailingRunLength;

                            numAdjacentRuns++;

                        }

                    }

                }

            }

        }

        // Make a final pass for any chunk that wasn't merged with a sibling

        // and include it in the list of chunks after merging.

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

            if (!chunkWasMerged[i]) {

                mergedChunks.add(chunks[i]);

            }

        }

        return mergedChunks;

    }

    /**

     * Breaks up the IL for this {@link MethodGenerator} into separate

     * outlined methods so that no method exceeds the 64KB limit on the length

     * of the byte code associated with a method.

     * @param classGen The {@link ClassGen} with which the generated methods

     *                 will be associated

     * @param originalMethodSize The number of bytes of bytecode represented by

     *                 the {@link InstructionList} of this method

     * @return an array of the outlined <code>Method</code>s and the original

     *         method itself

     */

    public Method[] outlineChunks(ClassGenerator classGen,

                                  int originalMethodSize) {

        List<Method> methodsOutlined = new ArrayList<>();

        int currentMethodSize = originalMethodSize;

        int outlinedCount = 0;

        boolean moreMethodsOutlined;

        String originalMethodName = getName();

        // Special handling for initialization methods.  No other methods can

        // include the less than and greater than characters in their names,

        // so we munge the names here.

        if (originalMethodName.equals("<init>")) {

            originalMethodName = "$lt$init$gt$";

        } else if (originalMethodName.equals("<clinit>")) {

            originalMethodName = "$lt$clinit$gt$";

        }

        // Loop until the original method comes in under the JVM limit or

        // the loop was unable to outline any more methods

        do {

            // Get all the best candidates for outlining, and sort them in

            // ascending order of size

            List<Chunk> candidateChunks = getCandidateChunks(classGen,

                                                           currentMethodSize);

            Collections.sort(candidateChunks);

            moreMethodsOutlined = false;

            // Loop over the candidates for outlining, from the largest to the

            // smallest and outline them one at a time, until the loop has

            // outlined all or the original method comes in under the JVM

            // limit on the size of a method.

            for (int i = candidateChunks.size()-1;

                 i >= 0 && currentMethodSize > TARGET_METHOD_SIZE;

                 i--) {

                Chunk chunkToOutline = candidateChunks.get(i);

                methodsOutlined.add(outline(chunkToOutline.getChunkStart(),

                                            chunkToOutline.getChunkEnd(),

                                            originalMethodName + "$outline$"

                                                               + outlinedCount,

                                            classGen));

                outlinedCount++;

                moreMethodsOutlined = true;

                InstructionList il = getInstructionList();

                InstructionHandle lastInst = il.getEnd();

                il.setPositions();

                // Check the size of the method now

                currentMethodSize =

                        lastInst.getPosition()

                                + lastInst.getInstruction().getLength();

            }

        } while (moreMethodsOutlined && currentMethodSize > TARGET_METHOD_SIZE);

        // Outlining failed to reduce the size of the current method

        // sufficiently.  Throw an internal error.

        if (currentMethodSize > MAX_METHOD_SIZE) {

            String msg = (new ErrorMsg(ErrorMsg.OUTLINE_ERR_METHOD_TOO_BIG))

                                  .toString();

            throw new InternalError(msg);

        }

        Method[] methodsArr = new Method[methodsOutlined.size() + 1];

        methodsOutlined.toArray(methodsArr);

        methodsArr[methodsOutlined.size()] = getThisMethod();

        return methodsArr;

    }

    /**

     * Given an outlineable chunk of code in the current {@link MethodGenerator}

     * move ("outline") the chunk to a new method, and replace the chunk in the

     * old method with a reference to that new method.  No

     * {@link OutlineableChunkStart} or {@link OutlineableChunkEnd} instructions

     * are copied.

     * @param first The {@link InstructionHandle} of the first instruction in

     *              the chunk to outline

     * @param last The <code>InstructionHandle</code> of the last instruction in

     *             the chunk to outline

     * @param outlinedMethodName The name of the new method

     * @param classGen The {@link ClassGenerator} of which the original

     *              and new methods will be members

     * @return The new {@link Method} containing the outlined code.

     */

    private Method outline(InstructionHandle first, InstructionHandle last,

                           String outlinedMethodName, ClassGenerator classGen) {

        // We're not equipped to deal with exception handlers yet.  Bail out!

        if (getExceptionHandlers().length != 0) {

            String msg = (new ErrorMsg(ErrorMsg.OUTLINE_ERR_TRY_CATCH))

                                  .toString();

            throw new InternalError(msg);

        }

        int outlineChunkStartOffset = first.getPosition();

        int outlineChunkEndOffset = last.getPosition()

                                        + last.getInstruction().getLength();

        ConstantPoolGen cpg = getConstantPool();

        // Create new outlined method with signature:

        //

        //   private final outlinedMethodName(CopyLocals copyLocals);

        //

        // CopyLocals is an object that is used to copy-in/copy-out local

        // variables that are used by the outlined method.   Only locals whose

        // value is potentially set or referenced outside the range of the

        // chunk that is being outlined will be represented in CopyLocals.  The

        // type of the variable for copying local variables is actually

        // generated to be unique - it is not named CopyLocals.

        //

        // The outlined method never needs to be referenced outside of this

        // class, and will never be overridden, so we mark it private final.

        final InstructionList newIL = new InstructionList();

        final XSLTC  xsltc = classGen.getParser().getXSLTC();

        final String argTypeName = xsltc.getHelperClassName();

        final Type[] argTypes =

            new Type[] {(new ObjectType(argTypeName)).toJCType()};

        final String argName = "copyLocals";

        final String[] argNames = new String[] {argName};

        int methodAttributes = ACC_PRIVATE | ACC_FINAL;

        final boolean isStaticMethod = (getAccessFlags() & ACC_STATIC) != 0;

        if (isStaticMethod) {

            methodAttributes = methodAttributes | ACC_STATIC;

        }

        final MethodGenerator outlinedMethodGen =

            new MethodGenerator(methodAttributes,

                                com.sun.org.apache.bcel.internal.generic.Type.VOID,

                                argTypes, argNames, outlinedMethodName,

                                getClassName(), newIL, cpg);

        // Create class for copying local variables to the outlined method.

        // The fields the class will need to contain will be determined as the

        // code in the outlineable chunk is examined.

        ClassGenerator copyAreaCG

            = new ClassGenerator(argTypeName, OBJECT_CLASS, argTypeName+".java",

                                 ACC_FINAL | ACC_PUBLIC | ACC_SUPER, null,

                                 classGen.getStylesheet()) {

                      public boolean isExternal() {

                          return true;

                      }

                  };

        ConstantPoolGen copyAreaCPG = copyAreaCG.getConstantPool();

        copyAreaCG.addEmptyConstructor(ACC_PUBLIC);

        // Number of fields in the copy class

        int copyAreaFieldCount = 0;

        // The handle for the instruction after the last one to be outlined.

        // Note that this should never end up being null.  An outlineable chunk

        // won't contain a RETURN instruction or other branch out of the chunk,

        // and the JVM specification prohibits code in a method from just

        // "falling off the end" so this should always point to a valid handle.

        InstructionHandle limit = last.getNext();

        // InstructionLists for copying values into and out of an instance of

        // CopyLocals:

        //      oldMethCoypInIL  - from locals in old method into an instance

        //                         of the CopyLocals class (oldMethCopyInIL)

        //      oldMethCopyOutIL - from CopyLocals back into locals in the old

        //                         method

        //      newMethCopyInIL  - from CopyLocals into locals in the new

        //                         method

        //      newMethCopyOutIL - from locals in new method into the instance

        //                         of the CopyLocals class

        InstructionList oldMethCopyInIL  = new InstructionList();

        InstructionList oldMethCopyOutIL = new InstructionList();

        InstructionList newMethCopyInIL  = new InstructionList();

        InstructionList newMethCopyOutIL = new InstructionList();

        // Allocate instance of class in which we'll copy in or copy out locals

        // and make two copies:  last copy is used to invoke constructor;

        // other two are used for references to fields in the CopyLocals object

        InstructionHandle outlinedMethodCallSetup =

            oldMethCopyInIL.append(new NEW(cpg.addClass(argTypeName)));

        oldMethCopyInIL.append(InstructionConst.DUP);

        oldMethCopyInIL.append(InstructionConst.DUP);

        oldMethCopyInIL.append(

            new INVOKESPECIAL(cpg.addMethodref(argTypeName, "<init>", "()V")));

        // Generate code to invoke the new outlined method, and place the code

        // on oldMethCopyOutIL

        InstructionHandle outlinedMethodRef;

        if (isStaticMethod) {

            outlinedMethodRef =

                oldMethCopyOutIL.append(

                    new INVOKESTATIC(cpg.addMethodref(

                                          classGen.getClassName(),

                                          outlinedMethodName,

                                          outlinedMethodGen.getSignature())));