/*
 * Copyright (c) 2010, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.codegen;

import static jdk.nashorn.internal.codegen.ClassEmitter.Flag.PRIVATE;
import static jdk.nashorn.internal.codegen.ClassEmitter.Flag.STATIC;
import static jdk.nashorn.internal.codegen.CompilerConstants.ARGUMENTS;
import static jdk.nashorn.internal.codegen.CompilerConstants.CALLEE;
import static jdk.nashorn.internal.codegen.CompilerConstants.CREATE_PROGRAM_FUNCTION;
import static jdk.nashorn.internal.codegen.CompilerConstants.GET_MAP;
import static jdk.nashorn.internal.codegen.CompilerConstants.GET_STRING;
import static jdk.nashorn.internal.codegen.CompilerConstants.QUICK_PREFIX;
import static jdk.nashorn.internal.codegen.CompilerConstants.REGEX_PREFIX;
import static jdk.nashorn.internal.codegen.CompilerConstants.SCOPE;
import static jdk.nashorn.internal.codegen.CompilerConstants.SPLIT_PREFIX;
import static jdk.nashorn.internal.codegen.CompilerConstants.THIS;
import static jdk.nashorn.internal.codegen.CompilerConstants.VARARGS;
import static jdk.nashorn.internal.codegen.CompilerConstants.interfaceCallNoLookup;
import static jdk.nashorn.internal.codegen.CompilerConstants.methodDescriptor;
import static jdk.nashorn.internal.codegen.CompilerConstants.staticCallNoLookup;
import static jdk.nashorn.internal.codegen.CompilerConstants.typeDescriptor;
import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCallNoLookup;
import static jdk.nashorn.internal.ir.Symbol.HAS_SLOT;
import static jdk.nashorn.internal.ir.Symbol.IS_INTERNAL;
import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.INVALID_PROGRAM_POINT;
import static jdk.nashorn.internal.runtime.UnwarrantedOptimismException.isValid;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_APPLY_TO_CALL;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_DECLARE;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_FAST_SCOPE;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_PROGRAM_POINT_SHIFT;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_SCOPE;

import java.io.PrintWriter;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Deque;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import java.util.function.Supplier;
import jdk.nashorn.internal.AssertsEnabled;
import jdk.nashorn.internal.IntDeque;
import jdk.nashorn.internal.codegen.ClassEmitter.Flag;
import jdk.nashorn.internal.codegen.CompilerConstants.Call;
import jdk.nashorn.internal.codegen.types.ArrayType;
import jdk.nashorn.internal.codegen.types.Type;
import jdk.nashorn.internal.ir.AccessNode;
import jdk.nashorn.internal.ir.BaseNode;
import jdk.nashorn.internal.ir.BinaryNode;
import jdk.nashorn.internal.ir.Block;
import jdk.nashorn.internal.ir.BlockStatement;
import jdk.nashorn.internal.ir.BreakNode;
import jdk.nashorn.internal.ir.CallNode;
import jdk.nashorn.internal.ir.CaseNode;
import jdk.nashorn.internal.ir.CatchNode;
import jdk.nashorn.internal.ir.ContinueNode;
import jdk.nashorn.internal.ir.EmptyNode;
import jdk.nashorn.internal.ir.Expression;
import jdk.nashorn.internal.ir.ExpressionStatement;
import jdk.nashorn.internal.ir.ForNode;
import jdk.nashorn.internal.ir.FunctionNode;
import jdk.nashorn.internal.ir.GetSplitState;
import jdk.nashorn.internal.ir.IdentNode;
import jdk.nashorn.internal.ir.IfNode;
import jdk.nashorn.internal.ir.IndexNode;
import jdk.nashorn.internal.ir.JoinPredecessorExpression;
import jdk.nashorn.internal.ir.JumpStatement;
import jdk.nashorn.internal.ir.JumpToInlinedFinally;
import jdk.nashorn.internal.ir.LabelNode;
import jdk.nashorn.internal.ir.LexicalContext;
import jdk.nashorn.internal.ir.LexicalContextNode;
import jdk.nashorn.internal.ir.LiteralNode;
import jdk.nashorn.internal.ir.LiteralNode.ArrayLiteralNode;
import jdk.nashorn.internal.ir.LiteralNode.PrimitiveLiteralNode;
import jdk.nashorn.internal.ir.LocalVariableConversion;
import jdk.nashorn.internal.ir.LoopNode;
import jdk.nashorn.internal.ir.Node;
import jdk.nashorn.internal.ir.ObjectNode;
import jdk.nashorn.internal.ir.Optimistic;
import jdk.nashorn.internal.ir.PropertyNode;
import jdk.nashorn.internal.ir.ReturnNode;
import jdk.nashorn.internal.ir.RuntimeNode;
import jdk.nashorn.internal.ir.RuntimeNode.Request;
import jdk.nashorn.internal.ir.SetSplitState;
import jdk.nashorn.internal.ir.SplitReturn;
import jdk.nashorn.internal.ir.Splittable;
import jdk.nashorn.internal.ir.Statement;
import jdk.nashorn.internal.ir.SwitchNode;
import jdk.nashorn.internal.ir.Symbol;
import jdk.nashorn.internal.ir.TernaryNode;
import jdk.nashorn.internal.ir.ThrowNode;
import jdk.nashorn.internal.ir.TryNode;
import jdk.nashorn.internal.ir.UnaryNode;
import jdk.nashorn.internal.ir.VarNode;
import jdk.nashorn.internal.ir.WhileNode;
import jdk.nashorn.internal.ir.WithNode;
import jdk.nashorn.internal.ir.visitor.NodeOperatorVisitor;
import jdk.nashorn.internal.ir.visitor.SimpleNodeVisitor;
import jdk.nashorn.internal.objects.Global;
import jdk.nashorn.internal.parser.Lexer.RegexToken;
import jdk.nashorn.internal.parser.TokenType;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.Debug;
import jdk.nashorn.internal.runtime.ECMAException;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.OptimisticReturnFilters;
import jdk.nashorn.internal.runtime.PropertyMap;
import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;
import jdk.nashorn.internal.runtime.RewriteException;
import jdk.nashorn.internal.runtime.Scope;
import jdk.nashorn.internal.runtime.ScriptEnvironment;
import jdk.nashorn.internal.runtime.ScriptFunction;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.ScriptRuntime;
import jdk.nashorn.internal.runtime.Source;
import jdk.nashorn.internal.runtime.Undefined;
import jdk.nashorn.internal.runtime.UnwarrantedOptimismException;
import jdk.nashorn.internal.runtime.arrays.ArrayData;
import jdk.nashorn.internal.runtime.linker.LinkerCallSite;
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;

This is the lowest tier of the code generator. It takes lowered ASTs emitted
from Lower and emits Java byte code. The byte code emission logic is broken
out into MethodEmitter. MethodEmitter works internally with a type stack, and
keeps track of the contents of the byte code stack. This way we avoid a large
number of special cases on the form
if (type == INT) {
    visitInsn(ILOAD, slot);
} else if (type == DOUBLE) {
    visitInsn(DOUBLE, slot);
}

This quickly became apparent when the code generator was generalized to work
with all types, and not just numbers or objects.

The CodeGenerator visits nodes only once and emits bytecode for them.
/**
 * This is the lowest tier of the code generator. It takes lowered ASTs emitted
 * from Lower and emits Java byte code. The byte code emission logic is broken
 * out into MethodEmitter. MethodEmitter works internally with a type stack, and
 * keeps track of the contents of the byte code stack. This way we avoid a large
 * number of special cases on the form
 * <pre>
 * if (type == INT) {
 *     visitInsn(ILOAD, slot);
 * } else if (type == DOUBLE) {
 *     visitInsn(DOUBLE, slot);
 * }
 * </pre>
 * This quickly became apparent when the code generator was generalized to work
 * with all types, and not just numbers or objects.
 * <p>
 * The CodeGenerator visits nodes only once and emits bytecode for them.
 */
@Logger(name="codegen")
final class CodeGenerator extends NodeOperatorVisitor<CodeGeneratorLexicalContext> implements Loggable {

    private static final Type SCOPE_TYPE = Type.typeFor(ScriptObject.class);

    private static final String GLOBAL_OBJECT = Type.getInternalName(Global.class);

    private static final Call CREATE_REWRITE_EXCEPTION = CompilerConstants.staticCallNoLookup(RewriteException.class,
            "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class);
    private static final Call CREATE_REWRITE_EXCEPTION_REST_OF = CompilerConstants.staticCallNoLookup(RewriteException.class,
            "create", RewriteException.class, UnwarrantedOptimismException.class, Object[].class, String[].class, int[].class);

    private static final Call ENSURE_INT = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
            "ensureInt", int.class, Object.class, int.class);
    private static final Call ENSURE_NUMBER = CompilerConstants.staticCallNoLookup(OptimisticReturnFilters.class,
            "ensureNumber", double.class, Object.class, int.class);

    private static final Call CREATE_FUNCTION_OBJECT = CompilerConstants.staticCallNoLookup(ScriptFunction.class,
            "create", ScriptFunction.class, Object[].class, int.class, ScriptObject.class);
    private static final Call CREATE_FUNCTION_OBJECT_NO_SCOPE = CompilerConstants.staticCallNoLookup(ScriptFunction.class,
            "create", ScriptFunction.class, Object[].class, int.class);

    private static final Call TO_NUMBER_FOR_EQ = CompilerConstants.staticCallNoLookup(JSType.class,
            "toNumberForEq", double.class, Object.class);
    private static final Call TO_NUMBER_FOR_STRICT_EQ = CompilerConstants.staticCallNoLookup(JSType.class,
            "toNumberForStrictEq", double.class, Object.class);


    private static final Class<?> ITERATOR_CLASS = Iterator.class;
    static {
        assert ITERATOR_CLASS == CompilerConstants.ITERATOR_PREFIX.type();
    }
    private static final Type ITERATOR_TYPE = Type.typeFor(ITERATOR_CLASS);
    private static final Type EXCEPTION_TYPE = Type.typeFor(CompilerConstants.EXCEPTION_PREFIX.type());

    private static final Integer INT_ZERO = 0;

    
Constant data & installation. The only reason the compiler keeps this is because it is assigned
 by reflection in class installation /** Constant data & installation. The only reason the compiler keeps this is because it is assigned
     *  by reflection in class installation */
    private final Compiler compiler;

    
Is the current code submitted by 'eval' call? /** Is the current code submitted by 'eval' call? */
    private final boolean evalCode;

    
Call site flags given to the code generator to be used for all generated call sites /** Call site flags given to the code generator to be used for all generated call sites */
    private final int callSiteFlags;

    
How many regexp fields have been emitted /** How many regexp fields have been emitted */
    private int regexFieldCount;

    
Line number for last statement. If we encounter a new line number, line number bytecode information
 needs to be generated /** Line number for last statement. If we encounter a new line number, line number bytecode information
     *  needs to be generated */
    private int lastLineNumber = -1;

    
When should we stop caching regexp expressions in fields to limit bytecode size? /** When should we stop caching regexp expressions in fields to limit bytecode size? */
    private static final int MAX_REGEX_FIELDS = 2 * 1024;

    
Current method emitter /** Current method emitter */
    private MethodEmitter method;

    
Current compile unit /** Current compile unit */
    private CompileUnit unit;

    private final DebugLogger log;

    
From what size should we use spill instead of fields for JavaScript objects? /** From what size should we use spill instead of fields for JavaScript objects? */
    static final int OBJECT_SPILL_THRESHOLD = Options.getIntProperty("nashorn.spill.threshold", 256);

    private final Set<String> emittedMethods = new HashSet<>();

    // Function Id -> ContinuationInfo. Used by compilation of rest-of function only.
    private ContinuationInfo continuationInfo;

    private final Deque<Label> scopeEntryLabels = new ArrayDeque<>();

    private static final Label METHOD_BOUNDARY = new Label("");
    private final Deque<Label> catchLabels = new ArrayDeque<>();
    // Number of live locals on entry to (and thus also break from) labeled blocks.
    private final IntDeque labeledBlockBreakLiveLocals = new IntDeque();

    //is this a rest of compilation
    private final int[] continuationEntryPoints;

    // Scope object creators needed for for-of and for-in loops
    private final Deque<FieldObjectCreator<?>> scopeObjectCreators = new ArrayDeque<>();

    
Constructor.
Params:
compiler – /**
     * Constructor.
     *
     * @param compiler
     */
    CodeGenerator(final Compiler compiler, final int[] continuationEntryPoints) {
        super(new CodeGeneratorLexicalContext());
        this.compiler                = compiler;
        this.evalCode                = compiler.getSource().isEvalCode();
        this.continuationEntryPoints = continuationEntryPoints;
        this.callSiteFlags           = compiler.getScriptEnvironment()._callsite_flags;
        this.log                     = initLogger(compiler.getContext());
    }

    @Override
    public DebugLogger getLogger() {
        return log;
    }

    @Override
    public DebugLogger initLogger(final Context context) {
        return context.getLogger(this.getClass());
    }

    
Gets the call site flags, adding the strict flag if the current function
being generated is in strict mode
Returns:
the correct flags for a call site in the current function/**
     * Gets the call site flags, adding the strict flag if the current function
     * being generated is in strict mode
     *
     * @return the correct flags for a call site in the current function
     */
    int getCallSiteFlags() {
        return lc.getCurrentFunction().getCallSiteFlags() | callSiteFlags;
    }

    
Gets the flags for a scope call site.
Params:
symbol – a scope symbol
Returns:
the correct flags for the scope call site/**
     * Gets the flags for a scope call site.
     * @param symbol a scope symbol
     * @return the correct flags for the scope call site
     */
    private int getScopeCallSiteFlags(final Symbol symbol) {
        assert symbol.isScope();
        final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
        if (isEvalCode() && symbol.isGlobal()) {
            return flags; // Don't set fast-scope flag on non-declared globals in eval code - see JDK-8077955.
        }
        return isFastScope(symbol) ? flags | CALLSITE_FAST_SCOPE : flags;
    }

    
Are we generating code for 'eval' code?
Returns:
true if currently compiled code is 'eval' code./**
     * Are we generating code for 'eval' code?
     * @return true if currently compiled code is 'eval' code.
     */
    boolean isEvalCode() {
        return evalCode;
    }

    
Are we using dual primitive/object field representation?
Returns:
true if using dual field representation, false for object-only fields/**
     * Are we using dual primitive/object field representation?
     * @return true if using dual field representation, false for object-only fields
     */
    boolean useDualFields() {
        return compiler.getContext().useDualFields();
    }

    
Load an identity node
Params:
identNode – an identity node to load
Returns:
the method generator used/**
     * Load an identity node
     *
     * @param identNode an identity node to load
     * @return the method generator used
     */
    private MethodEmitter loadIdent(final IdentNode identNode, final TypeBounds resultBounds) {
        checkTemporalDeadZone(identNode);
        final Symbol symbol = identNode.getSymbol();

        if (!symbol.isScope()) {
            final Type type = identNode.getType();
            if(type == Type.UNDEFINED) {
                return method.loadUndefined(resultBounds.widest);
            }

            assert symbol.hasSlot() || symbol.isParam();
            return method.load(identNode);
        }

        assert identNode.getSymbol().isScope() : identNode + " is not in scope!";
        final int flags = getScopeCallSiteFlags(symbol);
        if (isFastScope(symbol)) {
            // Only generate shared scope getter for fast-scope symbols so we know we can dial in correct scope.
            if (symbol.getUseCount() > SharedScopeCall.FAST_SCOPE_GET_THRESHOLD && !identNode.isOptimistic()) {
                // As shared scope vars are only used with non-optimistic identifiers, we switch from using TypeBounds to
                // just a single definitive type, resultBounds.widest.
                new OptimisticOperation(identNode, TypeBounds.OBJECT) {
                    @Override
                    void loadStack() {
                        method.loadCompilerConstant(SCOPE);
                    }

                    @Override
                    void consumeStack() {
                        loadSharedScopeVar(resultBounds.widest, symbol, flags);
                    }
                }.emit();
            } else {
                new LoadFastScopeVar(identNode, resultBounds, flags).emit();
            }
        } else {
            //slow scope load, we have no proto depth
            new LoadScopeVar(identNode, resultBounds, flags).emit();
        }

        return method;
    }

    // Any access to LET and CONST variables before their declaration must throw ReferenceError.
    // This is called the temporal dead zone (TDZ). See https://gist.github.com/rwaldron/f0807a758aa03bcdd58a
    private void checkTemporalDeadZone(final IdentNode identNode) {
        if (identNode.isDead()) {
            method.load(identNode.getSymbol().getName()).invoke(ScriptRuntime.THROW_REFERENCE_ERROR);
        }
    }

    // Runtime check for assignment to ES6 const
    private void checkAssignTarget(final Expression expression) {
        if (expression instanceof IdentNode && ((IdentNode)expression).getSymbol().isConst()) {
            method.load(((IdentNode)expression).getSymbol().getName()).invoke(ScriptRuntime.THROW_CONST_TYPE_ERROR);
        }
    }

    private boolean isRestOf() {
        return continuationEntryPoints != null;
    }

    private boolean isCurrentContinuationEntryPoint(final int programPoint) {
        return isRestOf() && getCurrentContinuationEntryPoint() == programPoint;
    }

    private int[] getContinuationEntryPoints() {
        return isRestOf() ? continuationEntryPoints : null;
    }

    private int getCurrentContinuationEntryPoint() {
        return isRestOf() ? continuationEntryPoints[0] : INVALID_PROGRAM_POINT;
    }

    private boolean isContinuationEntryPoint(final int programPoint) {
        if (isRestOf()) {
            assert continuationEntryPoints != null;
            for (final int cep : continuationEntryPoints) {
                if (cep == programPoint) {
                    return true;
                }
            }
        }
        return false;
    }

    
Check if this symbol can be accessed directly with a putfield or getfield or dynamic load
Params:
symbol – symbol to check for fast scope
Returns:
true if fast scope/**
     * Check if this symbol can be accessed directly with a putfield or getfield or dynamic load
     *
     * @param symbol symbol to check for fast scope
     * @return true if fast scope
     */
    private boolean isFastScope(final Symbol symbol) {
        if (!symbol.isScope()) {
            return false;
        }

        if (!lc.inDynamicScope()) {
            // If there's no with or eval in context, and the symbol is marked as scoped, it is fast scoped. Such a
            // symbol must either be global, or its defining block must need scope.
            assert symbol.isGlobal() || lc.getDefiningBlock(symbol).needsScope() : symbol.getName();
            return true;
        }

        if (symbol.isGlobal()) {
            // Shortcut: if there's a with or eval in context, globals can't be fast scoped
            return false;
        }

        // Otherwise, check if there's a dynamic scope between use of the symbol and its definition
        final String name = symbol.getName();
        boolean previousWasBlock = false;
        for (final Iterator<LexicalContextNode> it = lc.getAllNodes(); it.hasNext();) {
            final LexicalContextNode node = it.next();
            if (node instanceof Block) {
                // If this block defines the symbol, then we can fast scope the symbol.
                final Block block = (Block)node;
                if (block.getExistingSymbol(name) == symbol) {
                    assert block.needsScope();
                    return true;
                }
                previousWasBlock = true;
            } else {
                if (node instanceof WithNode && previousWasBlock || node instanceof FunctionNode && ((FunctionNode)node).needsDynamicScope()) {
                    // If we hit a scope that can have symbols introduced into it at run time before finding the defining
                    // block, the symbol can't be fast scoped. A WithNode only counts if we've immediately seen a block
                    // before - its block. Otherwise, we are currently processing the WithNode's expression, and that's
                    // obviously not subjected to introducing new symbols.
                    return false;
                }
                previousWasBlock = false;
            }
        }
        // Should've found the symbol defined in a block
        throw new AssertionError();
    }

    private MethodEmitter loadSharedScopeVar(final Type valueType, final Symbol symbol, final int flags) {
        assert isFastScope(symbol);
        method.load(getScopeProtoDepth(lc.getCurrentBlock(), symbol));
        return lc.getScopeGet(unit, symbol, valueType, flags).generateInvoke(method);
    }

    private class LoadScopeVar extends OptimisticOperation {
        final IdentNode identNode;
        private final int flags;

        LoadScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
            super(identNode, resultBounds);
            this.identNode = identNode;
            this.flags = flags;
        }

        @Override
        void loadStack() {
            method.loadCompilerConstant(SCOPE);
            getProto();
        }

        void getProto() {
            //empty
        }

        @Override
        void consumeStack() {
            // If this is either __FILE__, __DIR__, or __LINE__ then load the property initially as Object as we'd convert
            // it anyway for replaceLocationPropertyPlaceholder.
            if(identNode.isCompileTimePropertyName()) {
                method.dynamicGet(Type.OBJECT, identNode.getSymbol().getName(), flags, identNode.isFunction(), false);
                replaceCompileTimeProperty();
            } else {
                dynamicGet(identNode.getSymbol().getName(), flags, identNode.isFunction(), false);
            }
        }
    }

    private class LoadFastScopeVar extends LoadScopeVar {
        LoadFastScopeVar(final IdentNode identNode, final TypeBounds resultBounds, final int flags) {
            super(identNode, resultBounds, flags);
        }

        @Override
        void getProto() {
            loadFastScopeProto(identNode.getSymbol(), false);
        }
    }

    private MethodEmitter storeFastScopeVar(final Symbol symbol, final int flags) {
        loadFastScopeProto(symbol, true);
        method.dynamicSet(symbol.getName(), flags, false);
        return method;
    }

    private int getScopeProtoDepth(final Block startingBlock, final Symbol symbol) {
        //walk up the chain from starting block and when we bump into the current function boundary, add the external
        //information.
        final FunctionNode fn   = lc.getCurrentFunction();
        final int externalDepth = compiler.getScriptFunctionData(fn.getId()).getExternalSymbolDepth(symbol.getName());

        //count the number of scopes from this place to the start of the function

        final int internalDepth = FindScopeDepths.findInternalDepth(lc, fn, startingBlock, symbol);
        final int scopesToStart = FindScopeDepths.findScopesToStart(lc, fn, startingBlock);
        int depth = 0;
        if (internalDepth == -1) {
            depth = scopesToStart + externalDepth;
        } else {
            assert internalDepth <= scopesToStart;
            depth = internalDepth;
        }

        return depth;
    }

    private void loadFastScopeProto(final Symbol symbol, final boolean swap) {
        final int depth = getScopeProtoDepth(lc.getCurrentBlock(), symbol);
        assert depth != -1 : "Couldn't find scope depth for symbol " + symbol.getName() + " in " + lc.getCurrentFunction();
        if (depth > 0) {
            if (swap) {
                method.swap();
            }
            if (depth > 1) {
                method.load(depth);
                method.invoke(ScriptObject.GET_PROTO_DEPTH);
            } else {
                method.invoke(ScriptObject.GET_PROTO);
            }
            if (swap) {
                method.swap();
            }
        }
    }

    
Generate code that loads this node to the stack, not constraining its type
Params:
expr – node to load
Returns:
the method emitter used/**
     * Generate code that loads this node to the stack, not constraining its type
     *
     * @param expr node to load
     *
     * @return the method emitter used
     */
    private MethodEmitter loadExpressionUnbounded(final Expression expr) {
        return loadExpression(expr, TypeBounds.UNBOUNDED);
    }

    private MethodEmitter loadExpressionAsObject(final Expression expr) {
        return loadExpression(expr, TypeBounds.OBJECT);
    }

    MethodEmitter loadExpressionAsBoolean(final Expression expr) {
        return loadExpression(expr, TypeBounds.BOOLEAN);
    }

    // Test whether conversion from source to target involves a call of ES 9.1 ToPrimitive
    // with possible side effects from calling an object's toString or valueOf methods.
    private static boolean noToPrimitiveConversion(final Type source, final Type target) {
        // Object to boolean conversion does not cause ToPrimitive call
        return source.isJSPrimitive() || !target.isJSPrimitive() || target.isBoolean();
    }

    MethodEmitter loadBinaryOperands(final BinaryNode binaryNode) {
        return loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(binaryNode.getWidestOperandType()), false, false);
    }

    private MethodEmitter loadBinaryOperands(final Expression lhs, final Expression rhs, final TypeBounds explicitOperandBounds, final boolean baseAlreadyOnStack, final boolean forceConversionSeparation) {
        // ECMAScript 5.1 specification (sections 11.5-11.11 and 11.13) prescribes that when evaluating a binary
        // expression "LEFT op RIGHT", the order of operations must be: LOAD LEFT, LOAD RIGHT, CONVERT LEFT, CONVERT
        // RIGHT, EXECUTE OP. Unfortunately, doing it in this order defeats potential optimizations that arise when we
        // can combine a LOAD with a CONVERT operation (e.g. use a dynamic getter with the conversion target type as its
        // return value). What we do here is reorder LOAD RIGHT and CONVERT LEFT when possible; it is possible only when
        // we can prove that executing CONVERT LEFT can't have a side effect that changes the value of LOAD RIGHT.
        // Basically, if we know that either LEFT already is a primitive value, or does not have to be converted to
        // a primitive value, or RIGHT is an expression that loads without side effects, then we can do the
        // reordering and collapse LOAD/CONVERT into a single operation; otherwise we need to do the more costly
        // separate operations to preserve specification semantics.

        // Operands' load type should not be narrower than the narrowest of the individual operand types, nor narrower
        // than the lower explicit bound, but it should also not be wider than
        final Type lhsType = undefinedToNumber(lhs.getType());
        final Type rhsType = undefinedToNumber(rhs.getType());
        final Type narrowestOperandType = Type.narrowest(Type.widest(lhsType, rhsType), explicitOperandBounds.widest);
        final TypeBounds operandBounds = explicitOperandBounds.notNarrowerThan(narrowestOperandType);
        if (noToPrimitiveConversion(lhsType, explicitOperandBounds.widest) || rhs.isLocal()) {
            // Can reorder. We might still need to separate conversion, but at least we can do it with reordering
            if (forceConversionSeparation) {
                // Can reorder, but can't move conversion into the operand as the operation depends on operands
                // exact types for its overflow guarantees. E.g. with {L}{%I}expr1 {L}* {L}{%I}expr2 we are not allowed
                // to merge {L}{%I} into {%L}, as that can cause subsequent overflows; test for JDK-8058610 contains
                // concrete cases where this could happen.
                final TypeBounds safeConvertBounds = TypeBounds.UNBOUNDED.notNarrowerThan(narrowestOperandType);
                loadExpression(lhs, safeConvertBounds, baseAlreadyOnStack);
                method.convert(operandBounds.within(method.peekType()));
                loadExpression(rhs, safeConvertBounds, false);
                method.convert(operandBounds.within(method.peekType()));
            } else {
                // Can reorder and move conversion into the operand. Combine load and convert into single operations.
                loadExpression(lhs, operandBounds, baseAlreadyOnStack);
                loadExpression(rhs, operandBounds, false);
            }
        } else {
            // Can't reorder. Load and convert separately.
            final TypeBounds safeConvertBounds = TypeBounds.UNBOUNDED.notNarrowerThan(narrowestOperandType);
            loadExpression(lhs, safeConvertBounds, baseAlreadyOnStack);
            final Type lhsLoadedType = method.peekType();
            loadExpression(rhs, safeConvertBounds, false);
            final Type convertedLhsType = operandBounds.within(method.peekType());
            if (convertedLhsType != lhsLoadedType) {
                // Do it conditionally, so that if conversion is a no-op we don't introduce a SWAP, SWAP.
                method.swap().convert(convertedLhsType).swap();
            }
            method.convert(operandBounds.within(method.peekType()));
        }
        assert Type.generic(method.peekType()) == operandBounds.narrowest;
        assert Type.generic(method.peekType(1)) == operandBounds.narrowest;

        return method;
    }

    
Similar to loadBinaryOperands(BinaryNode) but used specifically for loading operands of relational and equality comparison operators where at least one argument is non-object. (When both arguments are objects, we use ScriptRuntime.EQ(Object, Object), ScriptRuntime.LT(Object, Object) etc. methods instead. Additionally, ScriptRuntime methods are used for strict (in)equality comparison of a boolean to anything that isn't a boolean.) This method handles the special case where one argument is an object and another is a primitive. Naively, these could also be delegated to ScriptRuntime methods by boxing the primitive. However, in all such cases the comparison is performed on numeric values, so it is possible to strength-reduce the operation by taking the number value of the object argument instead and comparing that to the primitive value ("primitive" will always be int, long, double, or boolean, and booleans compare as ints in these cases, so they're essentially numbers too). This method will emit code for loading arguments for such strength-reduced comparison. When both arguments are primitives, it just delegates to loadBinaryOperands(BinaryNode). 
Params:
cmp – the comparison operation for which the operands need to be loaded on stack.
Returns:
the current method emitter./**
     * Similar to {@link #loadBinaryOperands(BinaryNode)} but used specifically for loading operands of
     * relational and equality comparison operators where at least one argument is non-object. (When both
     * arguments are objects, we use {@link ScriptRuntime#EQ(Object, Object)}, {@link ScriptRuntime#LT(Object, Object)}
     * etc. methods instead. Additionally, {@code ScriptRuntime} methods are used for strict (in)equality comparison
     * of a boolean to anything that isn't a boolean.) This method handles the special case where one argument
     * is an object and another is a primitive. Naively, these could also be delegated to {@code ScriptRuntime} methods
     * by boxing the primitive. However, in all such cases the comparison is performed on numeric values, so it is
     * possible to strength-reduce the operation by taking the number value of the object argument instead and
     * comparing that to the primitive value ("primitive" will always be int, long, double, or boolean, and booleans
     * compare as ints in these cases, so they're essentially numbers too). This method will emit code for loading
     * arguments for such strength-reduced comparison. When both arguments are primitives, it just delegates to
     * {@link #loadBinaryOperands(BinaryNode)}.
     *
     * @param cmp the comparison operation for which the operands need to be loaded on stack.
     * @return the current method emitter.
     */
    MethodEmitter loadComparisonOperands(final BinaryNode cmp) {
        final Expression lhs = cmp.lhs();
        final Expression rhs = cmp.rhs();
        final Type lhsType = lhs.getType();
        final Type rhsType = rhs.getType();

        // Only used when not both are object, for that we have ScriptRuntime.LT etc.
        assert !(lhsType.isObject() && rhsType.isObject());

        if (lhsType.isObject() || rhsType.isObject()) {
            // We can reorder CONVERT LEFT and LOAD RIGHT only if either the left is a primitive, or the right
            // is a local. This is more strict than loadBinaryNode reorder criteria, as it can allow JS primitive
            // types too (notably: String is a JS primitive, but not a JVM primitive). We disallow String otherwise
            // we would prematurely convert it to number when comparing to an optimistic expression, e.g. in
            // "Hello" === String("Hello") the RHS starts out as an optimistic-int function call. If we allowed
            // reordering, we'd end up with ToNumber("Hello") === {I%}String("Hello") that is obviously incorrect.
            final boolean canReorder = lhsType.isPrimitive() || rhs.isLocal();
            // If reordering is allowed, and we're using a relational operator (that is, <, <=, >, >=) and not an
            // (in)equality operator, then we encourage combining of LOAD and CONVERT into a single operation.
            // This is because relational operators' semantics prescribes vanilla ToNumber() conversion, while
            // (in)equality operators need the specialized JSType.toNumberFor[Strict]Equals. E.g. in the code snippet
            // "i < obj.size" (where i is primitive and obj.size is statically an object), ".size" will thus be allowed
            // to compile as:
            //   invokedynamic GET_PROPERTY:size(Object;)D
            // instead of the more costly:
            //   invokedynamic GET_PROPERTY:size(Object;)Object
            //   invokestatic JSType.toNumber(Object)D
            // Note also that even if this is allowed, we're only using it on operands that are non-optimistic, as
            // otherwise the logic for determining effective optimistic-ness would turn an optimistic double return
            // into a freely coercible one, which would be wrong.
            final boolean canCombineLoadAndConvert = canReorder && cmp.isRelational();

            // LOAD LEFT
            loadExpression(lhs, canCombineLoadAndConvert && !lhs.isOptimistic() ? TypeBounds.NUMBER : TypeBounds.UNBOUNDED);

            final Type lhsLoadedType = method.peekType();
            final TokenType tt = cmp.tokenType();
            if (canReorder) {
                // Can reorder CONVERT LEFT and LOAD RIGHT
                emitObjectToNumberComparisonConversion(method, tt);
                loadExpression(rhs, canCombineLoadAndConvert && !rhs.isOptimistic() ? TypeBounds.NUMBER : TypeBounds.UNBOUNDED);
            } else {
                // Can't reorder CONVERT LEFT and LOAD RIGHT
                loadExpression(rhs, TypeBounds.UNBOUNDED);
                if (lhsLoadedType != Type.NUMBER) {
                    method.swap();
                    emitObjectToNumberComparisonConversion(method, tt);
                    method.swap();
                }
            }

            // CONVERT RIGHT
            emitObjectToNumberComparisonConversion(method, tt);
            return method;
        }
        // For primitive operands, just don't do anything special.
        return loadBinaryOperands(cmp);
    }

    private static void emitObjectToNumberComparisonConversion(final MethodEmitter method, final TokenType tt) {
        switch(tt) {
        case EQ:
        case NE:
            if (method.peekType().isObject()) {
                TO_NUMBER_FOR_EQ.invoke(method);
                return;
            }
            break;
        case EQ_STRICT:
        case NE_STRICT:
            if (method.peekType().isObject()) {
                TO_NUMBER_FOR_STRICT_EQ.invoke(method);
                return;
            }
            break;
        default:
            break;
        }
        method.convert(Type.NUMBER);
    }

    private static Type undefinedToNumber(final Type type) {
        return type == Type.UNDEFINED ? Type.NUMBER : type;
    }

    private static final class TypeBounds {
        final Type narrowest;
        final Type widest;

        static final TypeBounds UNBOUNDED = new TypeBounds(Type.UNKNOWN, Type.OBJECT);
        static final TypeBounds INT = exact(Type.INT);
        static final TypeBounds NUMBER = exact(Type.NUMBER);
        static final TypeBounds OBJECT = exact(Type.OBJECT);
        static final TypeBounds BOOLEAN = exact(Type.BOOLEAN);

        static TypeBounds exact(final Type type) {
            return new TypeBounds(type, type);
        }

        TypeBounds(final Type narrowest, final Type widest) {
            assert widest    != null && widest    != Type.UNDEFINED && widest != Type.UNKNOWN : widest;
            assert narrowest != null && narrowest != Type.UNDEFINED : narrowest;
            assert !narrowest.widerThan(widest) : narrowest + " wider than " + widest;
            assert !widest.narrowerThan(narrowest);
            this.narrowest = Type.generic(narrowest);
            this.widest = Type.generic(widest);
        }

        TypeBounds notNarrowerThan(final Type type) {
            return maybeNew(Type.narrowest(Type.widest(narrowest, type), widest), widest);
        }

        TypeBounds notWiderThan(final Type type) {
            return maybeNew(Type.narrowest(narrowest, type), Type.narrowest(widest, type));
        }

        boolean canBeNarrowerThan(final Type type) {
            return narrowest.narrowerThan(type);
        }

        TypeBounds maybeNew(final Type newNarrowest, final Type newWidest) {
            if(newNarrowest == narrowest && newWidest == widest) {
                return this;
            }
            return new TypeBounds(newNarrowest, newWidest);
        }

        TypeBounds booleanToInt() {
            return maybeNew(CodeGenerator.booleanToInt(narrowest), CodeGenerator.booleanToInt(widest));
        }

        TypeBounds objectToNumber() {
            return maybeNew(CodeGenerator.objectToNumber(narrowest), CodeGenerator.objectToNumber(widest));
        }

        Type within(final Type type) {
            if(type.narrowerThan(narrowest)) {
                return narrowest;
            }
            if(type.widerThan(widest)) {
                return widest;
            }
            return type;
        }

        @Override
        public String toString() {
            return "[" + narrowest + ", " + widest + "]";
        }
    }

    private static Type booleanToInt(final Type t) {
        return t == Type.BOOLEAN ? Type.INT : t;
    }

    private static Type objectToNumber(final Type t) {
        return t.isObject() ? Type.NUMBER : t;
    }

    MethodEmitter loadExpressionAsType(final Expression expr, final Type type) {
        if(type == Type.BOOLEAN) {
            return loadExpressionAsBoolean(expr);
        } else if(type == Type.UNDEFINED) {
            assert expr.getType() == Type.UNDEFINED;
            return loadExpressionAsObject(expr);
        }
        // having no upper bound preserves semantics of optimistic operations in the expression (by not having them
        // converted early) and then applies explicit conversion afterwards.
        return loadExpression(expr, TypeBounds.UNBOUNDED.notNarrowerThan(type)).convert(type);
    }

    private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds) {
        return loadExpression(expr, resultBounds, false);
    }

    
Emits code for evaluating an expression and leaving its value on top of the stack, narrowing or widening it if
necessary.
Params:
expr – the expression to load
resultBounds – the incoming type bounds. The value on the top of the stack is guaranteed to not be of narrower
type than the narrowest bound, or wider type than the widest bound after it is loaded.
baseAlreadyOnStack – true if the base of an access or index node is already on the stack. Used to avoid double evaluation of bases in self-assignment expressions to access and index nodes. Type.OBJECT is used to indicate the widest possible type.
Returns:
the method emitter/**
     * Emits code for evaluating an expression and leaving its value on top of the stack, narrowing or widening it if
     * necessary.
     * @param expr the expression to load
     * @param resultBounds the incoming type bounds. The value on the top of the stack is guaranteed to not be of narrower
     * type than the narrowest bound, or wider type than the widest bound after it is loaded.
     * @param baseAlreadyOnStack true if the base of an access or index node is already on the stack. Used to avoid
     * double evaluation of bases in self-assignment expressions to access and index nodes. {@code Type.OBJECT} is used
     * to indicate the widest possible type.
     * @return the method emitter
     */
    private MethodEmitter loadExpression(final Expression expr, final TypeBounds resultBounds, final boolean baseAlreadyOnStack) {

        /*
         * The load may be of type IdentNode, e.g. "x", AccessNode, e.g. "x.y"
         * or IndexNode e.g. "x[y]". Both AccessNodes and IndexNodes are
         * BaseNodes and the logic for loading the base object is reused
         */
        final CodeGenerator codegen = this;

        final boolean isCurrentDiscard = codegen.lc.isCurrentDiscard(expr);
        expr.accept(new NodeOperatorVisitor<LexicalContext>(new LexicalContext()) {
            @Override
            public boolean enterIdentNode(final IdentNode identNode) {
                loadIdent(identNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterAccessNode(final AccessNode accessNode) {
                new OptimisticOperation(accessNode, resultBounds) {
                    @Override
                    void loadStack() {
                        if (!baseAlreadyOnStack) {
                            loadExpressionAsObject(accessNode.getBase());
                        }
                        assert method.peekType().isObject();
                    }
                    @Override
                    void consumeStack() {
                        final int flags = getCallSiteFlags();
                        dynamicGet(accessNode.getProperty(), flags, accessNode.isFunction(), accessNode.isIndex());
                    }
                }.emit(baseAlreadyOnStack ? 1 : 0);
                return false;
            }

            @Override
            public boolean enterIndexNode(final IndexNode indexNode) {
                new OptimisticOperation(indexNode, resultBounds) {
                    @Override
                    void loadStack() {
                        if (!baseAlreadyOnStack) {
                            loadExpressionAsObject(indexNode.getBase());
                            loadExpressionUnbounded(indexNode.getIndex());
                        }
                    }
                    @Override
                    void consumeStack() {
                        final int flags = getCallSiteFlags();
                        dynamicGetIndex(flags, indexNode.isFunction());
                    }
                }.emit(baseAlreadyOnStack ? 2 : 0);
                return false;
            }

            @Override
            public boolean enterFunctionNode(final FunctionNode functionNode) {
                // function nodes will always leave a constructed function object on stack, no need to load the symbol
                // separately as in enterDefault()
                lc.pop(functionNode);
                functionNode.accept(codegen);
                // NOTE: functionNode.accept() will produce a different FunctionNode that we discard. This incidentally
                // doesn't cause problems as we're never touching FunctionNode again after it's visited here - codegen
                // is the last element in the compilation pipeline, the AST it produces is not used externally. So, we
                // re-push the original functionNode.
                lc.push(functionNode);
                return false;
            }

            @Override
            public boolean enterASSIGN(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_ADD(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_ADD(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_BIT_AND(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_BIT_AND(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_BIT_OR(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_BIT_OR(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_BIT_XOR(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_BIT_XOR(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_DIV(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_DIV(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_MOD(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_MOD(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_MUL(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_MUL(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_SAR(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_SAR(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_SHL(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_SHL(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_SHR(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_SHR(binaryNode);
                return false;
            }

            @Override
            public boolean enterASSIGN_SUB(final BinaryNode binaryNode) {
                checkAssignTarget(binaryNode.lhs());
                loadASSIGN_SUB(binaryNode);
                return false;
            }

            @Override
            public boolean enterCallNode(final CallNode callNode) {
                return loadCallNode(callNode, resultBounds);
            }

            @Override
            public boolean enterLiteralNode(final LiteralNode<?> literalNode) {
                loadLiteral(literalNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterTernaryNode(final TernaryNode ternaryNode) {
                loadTernaryNode(ternaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterADD(final BinaryNode binaryNode) {
                loadADD(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterSUB(final UnaryNode unaryNode) {
                loadSUB(unaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterSUB(final BinaryNode binaryNode) {
                loadSUB(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterMUL(final BinaryNode binaryNode) {
                loadMUL(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterDIV(final BinaryNode binaryNode) {
                loadDIV(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterMOD(final BinaryNode binaryNode) {
                loadMOD(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterSAR(final BinaryNode binaryNode) {
                loadSAR(binaryNode);
                return false;
            }

            @Override
            public boolean enterSHL(final BinaryNode binaryNode) {
                loadSHL(binaryNode);
                return false;
            }

            @Override
            public boolean enterSHR(final BinaryNode binaryNode) {
                loadSHR(binaryNode);
                return false;
            }

            @Override
            public boolean enterCOMMALEFT(final BinaryNode binaryNode) {
                loadCOMMALEFT(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterCOMMARIGHT(final BinaryNode binaryNode) {
                loadCOMMARIGHT(binaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterAND(final BinaryNode binaryNode) {
                loadAND_OR(binaryNode, resultBounds, true);
                return false;
            }

            @Override
            public boolean enterOR(final BinaryNode binaryNode) {
                loadAND_OR(binaryNode, resultBounds, false);
                return false;
            }

            @Override
            public boolean enterNOT(final UnaryNode unaryNode) {
                loadNOT(unaryNode);
                return false;
            }

            @Override
            public boolean enterADD(final UnaryNode unaryNode) {
                loadADD(unaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterBIT_NOT(final UnaryNode unaryNode) {
                loadBIT_NOT(unaryNode);
                return false;
            }

            @Override
            public boolean enterBIT_AND(final BinaryNode binaryNode) {
                loadBIT_AND(binaryNode);
                return false;
            }

            @Override
            public boolean enterBIT_OR(final BinaryNode binaryNode) {
                loadBIT_OR(binaryNode);
                return false;
            }

            @Override
            public boolean enterBIT_XOR(final BinaryNode binaryNode) {
                loadBIT_XOR(binaryNode);
                return false;
            }

            @Override
            public boolean enterVOID(final UnaryNode unaryNode) {
                loadVOID(unaryNode, resultBounds);
                return false;
            }

            @Override
            public boolean enterEQ(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.EQ);
                return false;
            }

            @Override
            public boolean enterEQ_STRICT(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.EQ);
                return false;
            }

            @Override
            public boolean enterGE(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.GE);
                return false;
            }

            @Override
            public boolean enterGT(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.GT);
                return false;
            }

            @Override
            public boolean enterLE(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.LE);
                return false;
            }

            @Override
            public boolean enterLT(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.LT);
                return false;
            }

            @Override
            public boolean enterNE(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.NE);
                return false;
            }

            @Override
            public boolean enterNE_STRICT(final BinaryNode binaryNode) {
                loadCmp(binaryNode, Condition.NE);
                return false;
            }

            @Override
            public boolean enterObjectNode(final ObjectNode objectNode) {
                loadObjectNode(objectNode);
                return false;
            }

            @Override
            public boolean enterRuntimeNode(final RuntimeNode runtimeNode) {
                loadRuntimeNode(runtimeNode);
                return false;
            }

            @Override
            public boolean enterNEW(final UnaryNode unaryNode) {
                loadNEW(unaryNode);
                return false;
            }

            @Override
            public boolean enterDECINC(final UnaryNode unaryNode) {
                checkAssignTarget(unaryNode.getExpression());
                loadDECINC(unaryNode);
                return false;
            }

            @Override
            public boolean enterJoinPredecessorExpression(final JoinPredecessorExpression joinExpr) {
                loadMaybeDiscard(joinExpr, joinExpr.getExpression(), resultBounds);
                return false;
            }

            @Override
            public boolean enterGetSplitState(final GetSplitState getSplitState) {
                method.loadScope();
                method.invoke(Scope.GET_SPLIT_STATE);
                return false;
            }

            @Override
            public boolean enterDefault(final Node otherNode) {
                // Must have handled all expressions that can legally be encountered.
                throw new AssertionError(otherNode.getClass().getName());
            }
        });
        if(!isCurrentDiscard) {
            coerceStackTop(resultBounds);
        }
        return method;
    }

    private MethodEmitter coerceStackTop(final TypeBounds typeBounds) {
        return method.convert(typeBounds.within(method.peekType()));
    }

    
Closes any still open entries for this block's local variables in the bytecode local variable table.
Params:
block – block containing symbols./**
     * Closes any still open entries for this block's local variables in the bytecode local variable table.
     *
     * @param block block containing symbols.
     */
    private void closeBlockVariables(final Block block) {
        for (final Symbol symbol : block.getSymbols()) {
            if (symbol.isBytecodeLocal()) {
                method.closeLocalVariable(symbol, block.getBreakLabel());
            }
        }
    }

    @Override
    public boolean enterBlock(final Block block) {
        final Label entryLabel = block.getEntryLabel();
        if (entryLabel.isBreakTarget()) {
            // Entry label is a break target only for an inlined finally block.
            assert !method.isReachable();
            method.breakLabel(entryLabel, lc.getUsedSlotCount());
        } else {
            method.label(entryLabel);
        }
        if(!method.isReachable()) {
            return false;
        }
        if(lc.isFunctionBody() && emittedMethods.contains(lc.getCurrentFunction().getName())) {
            return false;
        }
        initLocals(block);

        assert lc.getUsedSlotCount() == method.getFirstTemp();
        return true;
    }

    boolean useOptimisticTypes() {
        return !lc.inSplitNode() && compiler.useOptimisticTypes();
    }

    @Override
    public Node leaveBlock(final Block block) {
        popBlockScope(block);
        method.beforeJoinPoint(block);

        closeBlockVariables(block);
        lc.releaseSlots();
        assert !method.isReachable() || (lc.isFunctionBody() ? 0 : lc.getUsedSlotCount()) == method.getFirstTemp() :
            "reachable="+method.isReachable() +
            " isFunctionBody=" + lc.isFunctionBody() +
            " usedSlotCount=" + lc.getUsedSlotCount() +
            " firstTemp=" + method.getFirstTemp();

        return block;
    }

    private void popBlockScope(final Block block) {
        final Label breakLabel = block.getBreakLabel();

        if (block.providesScopeCreator()) {
            scopeObjectCreators.pop();
        }
        if(!block.needsScope() || lc.isFunctionBody()) {
            emitBlockBreakLabel(breakLabel);
            return;
        }

        final Label beginTryLabel = scopeEntryLabels.pop();
        final Label recoveryLabel = new Label("block_popscope_catch");
        emitBlockBreakLabel(breakLabel);
        final boolean bodyCanThrow = breakLabel.isAfter(beginTryLabel);
        if(bodyCanThrow) {
            method._try(beginTryLabel, breakLabel, recoveryLabel);
        }

        Label afterCatchLabel = null;

        if(method.isReachable()) {
            popScope();
            if(bodyCanThrow) {
                afterCatchLabel = new Label("block_after_catch");
                method._goto(afterCatchLabel);
            }
        }

        if(bodyCanThrow) {
            assert !method.isReachable();
            method._catch(recoveryLabel);
            popScopeException();
            method.athrow();
        }
        if(afterCatchLabel != null) {
            method.label(afterCatchLabel);
        }
    }

    private void emitBlockBreakLabel(final Label breakLabel) {
        // TODO: this is totally backwards. Block should not be breakable, LabelNode should be breakable.
        final LabelNode labelNode = lc.getCurrentBlockLabelNode();
        if(labelNode != null) {
            // Only have conversions if we're reachable
            assert labelNode.getLocalVariableConversion() == null || method.isReachable();
            method.beforeJoinPoint(labelNode);
            method.breakLabel(breakLabel, labeledBlockBreakLiveLocals.pop());
        } else {
            method.label(breakLabel);
        }
    }

    private void popScope() {
        popScopes(1);
    }

    
Pop scope as part of an exception handler. Similar to popScope() but also takes care of adjusting the number of scopes that needs to be popped in case a rest-of continuation handler encounters an exception while performing a ToPrimitive conversion. /**
     * Pop scope as part of an exception handler. Similar to {@code popScope()} but also takes care of adjusting the
     * number of scopes that needs to be popped in case a rest-of continuation handler encounters an exception while
     * performing a ToPrimitive conversion.
     */
    private void popScopeException() {
        popScope();
        final ContinuationInfo ci = getContinuationInfo();
        if(ci != null) {
            final Label catchLabel = ci.catchLabel;
            if(catchLabel != METHOD_BOUNDARY && catchLabel == catchLabels.peek()) {
                ++ci.exceptionScopePops;
            }
        }
    }

    private void popScopesUntil(final LexicalContextNode until) {
        popScopes(lc.getScopeNestingLevelTo(until));
    }

    private void popScopes(final int count) {
        if(count == 0) {
            return;
        }
        assert count > 0; // together with count == 0 check, asserts nonnegative count
        if (!method.hasScope()) {
            // We can sometimes invoke this method even if the method has no slot for the scope object. Typical example:
            // for(;;) { with({}) { break; } }. WithNode normally creates a scope, but if it uses no identifiers and
            // nothing else forces creation of a scope in the method, we just won't have the :scope local variable.
            return;
        }
        method.loadCompilerConstant(SCOPE);
        if (count > 1) {
            method.load(count);
            method.invoke(ScriptObject.GET_PROTO_DEPTH);
        } else {
            method.invoke(ScriptObject.GET_PROTO);
        }
        method.storeCompilerConstant(SCOPE);
    }

    @Override
    public boolean enterBreakNode(final BreakNode breakNode) {
        return enterJumpStatement(breakNode);
    }

    @Override
    public boolean enterJumpToInlinedFinally(final JumpToInlinedFinally jumpToInlinedFinally) {
        return enterJumpStatement(jumpToInlinedFinally);
    }

    private boolean enterJumpStatement(final JumpStatement jump) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(jump);

        method.beforeJoinPoint(jump);
        popScopesUntil(jump.getPopScopeLimit(lc));
        final Label targetLabel = jump.getTargetLabel(lc);
        targetLabel.markAsBreakTarget();
        method._goto(targetLabel);

        return false;
    }

    private int loadArgs(final List<Expression> args) {
        final int argCount = args.size();
        // arg have already been converted to objects here.
        if (argCount > LinkerCallSite.ARGLIMIT) {
            loadArgsArray(args);
            return 1;
        }

        for (final Expression arg : args) {
            assert arg != null;
            loadExpressionUnbounded(arg);
        }
        return argCount;
    }

    private boolean loadCallNode(final CallNode callNode, final TypeBounds resultBounds) {
        lineNumber(callNode.getLineNumber());

        final List<Expression> args = callNode.getArgs();
        final Expression function = callNode.getFunction();
        final Block currentBlock = lc.getCurrentBlock();
        final CodeGeneratorLexicalContext codegenLexicalContext = lc;

        function.accept(new SimpleNodeVisitor() {
            private MethodEmitter sharedScopeCall(final IdentNode identNode, final int flags) {
                final Symbol symbol = identNode.getSymbol();
                final boolean isFastScope = isFastScope(symbol);
                new OptimisticOperation(callNode, resultBounds) {
                    @Override
                    void loadStack() {
                        method.loadCompilerConstant(SCOPE);
                        if (isFastScope) {
                            method.load(getScopeProtoDepth(currentBlock, symbol));
                        } else {
                            method.load(-1); // Bypass fast-scope code in shared callsite
                        }
                        loadArgs(args);
                    }
                    @Override
                    void consumeStack() {
                        final Type[] paramTypes = method.getTypesFromStack(args.size());
                        // We have trouble finding e.g. in Type.typeFor(asm.Type) because it can't see the Context class
                        // loader, so we need to weaken reference signatures to Object.
                        for(int i = 0; i < paramTypes.length; ++i) {
                            paramTypes[i] = Type.generic(paramTypes[i]);
                        }
                        // As shared scope calls are only used in non-optimistic compilation, we switch from using
                        // TypeBounds to just a single definitive type, resultBounds.widest.
                        final SharedScopeCall scopeCall = codegenLexicalContext.getScopeCall(unit, symbol,
                                identNode.getType(), resultBounds.widest, paramTypes, flags);
                        scopeCall.generateInvoke(method);
                    }
                }.emit();
                return method;
            }

            private void scopeCall(final IdentNode ident, final int flags) {
                new OptimisticOperation(callNode, resultBounds) {
                    int argsCount;
                    @Override
                    void loadStack() {
                        loadExpressionAsObject(ident); // foo() makes no sense if foo == 3
                        // ScriptFunction will see CALLSITE_SCOPE and will bind scope accordingly.
                        method.loadUndefined(Type.OBJECT); //the 'this'
                        argsCount = loadArgs(args);
                    }
                    @Override
                    void consumeStack() {
                        dynamicCall(2 + argsCount, flags, ident.getName());
                    }
                }.emit();
            }

            private void evalCall(final IdentNode ident, final int flags) {
                final Label invoke_direct_eval  = new Label("invoke_direct_eval");
                final Label is_not_eval  = new Label("is_not_eval");
                final Label eval_done = new Label("eval_done");

                new OptimisticOperation(callNode, resultBounds) {
                    int argsCount;
                    @Override
                    void loadStack() {
                        /*
                         * We want to load 'eval' to check if it is indeed global builtin eval.
                         * If this eval call is inside a 'with' statement, GET_METHOD_PROPERTY
                         * would be generated if ident is a "isFunction". But, that would result in a
                         * bound function from WithObject. We don't want that as bound function as that
                         * won't be detected as builtin eval. So, we make ident as "not a function" which
                         * results in GET_PROPERTY being generated and so WithObject
                         * would return unbounded eval function.
                         *
                         * Example:
                         *
                         *  var global = this;
                         *  function func() {
                         *      with({ eval: global.eval) { eval("var x = 10;") }
                         *  }
                         */
                        loadExpressionAsObject(ident.setIsNotFunction()); // Type.OBJECT as foo() makes no sense if foo == 3
                        globalIsEval();
                        method.ifeq(is_not_eval);

                        // Load up self (scope).
                        method.loadCompilerConstant(SCOPE);
                        final List<Expression> evalArgs = callNode.getEvalArgs().getArgs();
                        // load evaluated code
                        loadExpressionAsObject(evalArgs.get(0));
                        // load second and subsequent args for side-effect
                        final int numArgs = evalArgs.size();
                        for (int i = 1; i < numArgs; i++) {
                            loadAndDiscard(evalArgs.get(i));
                        }
                        method._goto(invoke_direct_eval);

                        method.label(is_not_eval);
                        // load this time but with GET_METHOD_PROPERTY
                        loadExpressionAsObject(ident); // Type.OBJECT as foo() makes no sense if foo == 3
                        // This is some scope 'eval' or global eval replaced by user
                        // but not the built-in ECMAScript 'eval' function call
                        method.loadNull();
                        argsCount = loadArgs(callNode.getArgs());
                    }

                    @Override
                    void consumeStack() {
                        // Ordinary call
                        dynamicCall(2 + argsCount, flags, "eval");
                        method._goto(eval_done);

                        method.label(invoke_direct_eval);
                        // Special/extra 'eval' arguments. These can be loaded late (in consumeStack) as we know none of
                        // them can ever be optimistic.
                        method.loadCompilerConstant(THIS);
                        method.load(callNode.getEvalArgs().getLocation());
                        method.load(CodeGenerator.this.lc.getCurrentFunction().isStrict());
                        // direct call to Global.directEval
                        globalDirectEval();
                        convertOptimisticReturnValue();
                        coerceStackTop(resultBounds);
                    }
                }.emit();

                method.label(eval_done);
            }

            @Override
            public boolean enterIdentNode(final IdentNode node) {
                final Symbol symbol = node.getSymbol();

                if (symbol.isScope()) {
                    final int flags = getScopeCallSiteFlags(symbol);
                    final int useCount = symbol.getUseCount();

                    // Threshold for generating shared scope callsite is lower for fast scope symbols because we know
                    // we can dial in the correct scope. However, we also need to enable it for non-fast scopes to
                    // support huge scripts like mandreel.js.
                    if (callNode.isEval()) {
                        evalCall(node, flags);
                    } else if (useCount <= SharedScopeCall.FAST_SCOPE_CALL_THRESHOLD
                            || !isFastScope(symbol) && useCount <= SharedScopeCall.SLOW_SCOPE_CALL_THRESHOLD
                            || CodeGenerator.this.lc.inDynamicScope()
                            || callNode.isOptimistic()) {
                        scopeCall(node, flags);
                    } else {
                        sharedScopeCall(node, flags);
                    }
                    assert method.peekType().equals(resultBounds.within(callNode.getType())) : method.peekType() + " != " + resultBounds + "(" + callNode.getType() + ")";
                } else {
                    enterDefault(node);
                }

                return false;
            }

            @Override
            public boolean enterAccessNode(final AccessNode node) {
                //check if this is an apply to call node. only real applies, that haven't been
                //shadowed from their way to the global scope counts

                //call nodes have program points.

                final int flags = getCallSiteFlags() | (callNode.isApplyToCall() ? CALLSITE_APPLY_TO_CALL : 0);

                new OptimisticOperation(callNode, resultBounds) {
                    int argCount;
                    @Override
                    void loadStack() {
                        loadExpressionAsObject(node.getBase());
                        method.dup();
                        // NOTE: not using a nested OptimisticOperation on this dynamicGet, as we expect to get back
                        // a callable object. Nobody in their right mind would optimistically type this call site.
                        assert !node.isOptimistic();
                        method.dynamicGet(node.getType(), node.getProperty(), flags, true, node.isIndex());
                        method.swap();
                        argCount = loadArgs(args);
                    }
                    @Override
                    void consumeStack() {
                        dynamicCall(2 + argCount, flags, node.toString(false));
                    }
                }.emit();

                return false;
            }

            @Override
            public boolean enterFunctionNode(final FunctionNode origCallee) {
                new OptimisticOperation(callNode, resultBounds) {
                    FunctionNode callee;
                    int argsCount;
                    @Override
                    void loadStack() {
                        callee = (FunctionNode)origCallee.accept(CodeGenerator.this);
                        if (callee.isStrict()) { // "this" is undefined
                            method.loadUndefined(Type.OBJECT);
                        } else { // get global from scope (which is the self)
                            globalInstance();
                        }
                        argsCount = loadArgs(args);
                    }

                    @Override
                    void consumeStack() {
                        dynamicCall(2 + argsCount, getCallSiteFlags(), null);
                    }
                }.emit();
                return false;
            }

            @Override
            public boolean enterIndexNode(final IndexNode node) {
                new OptimisticOperation(callNode, resultBounds) {
                    int argsCount;
                    @Override
                    void loadStack() {
                        loadExpressionAsObject(node.getBase());
                        method.dup();
                        final Type indexType = node.getIndex().getType();
                        if (indexType.isObject() || indexType.isBoolean()) {
                            loadExpressionAsObject(node.getIndex()); //TODO boolean
                        } else {
                            loadExpressionUnbounded(node.getIndex());
                        }
                        // NOTE: not using a nested OptimisticOperation on this dynamicGetIndex, as we expect to get
                        // back a callable object. Nobody in their right mind would optimistically type this call site.
                        assert !node.isOptimistic();
                        method.dynamicGetIndex(node.getType(), getCallSiteFlags(), true);
                        method.swap();
                        argsCount = loadArgs(args);
                    }
                    @Override
                    void consumeStack() {
                        dynamicCall(2 + argsCount, getCallSiteFlags(), node.toString(false));
                    }
                }.emit();
                return false;
            }

            @Override
            protected boolean enterDefault(final Node node) {
                new OptimisticOperation(callNode, resultBounds) {
                    int argsCount;
                    @Override
                    void loadStack() {
                        // Load up function.
                        loadExpressionAsObject(function); //TODO, e.g. booleans can be used as functions
                        method.loadUndefined(Type.OBJECT); // ScriptFunction will figure out the correct this when it sees CALLSITE_SCOPE
                        argsCount = loadArgs(args);
                        }
                        @Override
                        void consumeStack() {
                            final int flags = getCallSiteFlags() | CALLSITE_SCOPE;
                            dynamicCall(2 + argsCount, flags, node.toString(false));
                        }
                }.emit();
                return false;
            }
        });

        return false;
    }

    
Returns the flags with optimistic flag and program point removed.
Params:
flags – the flags that need optimism stripped from them.
Returns:
flags without optimism/**
     * Returns the flags with optimistic flag and program point removed.
     * @param flags the flags that need optimism stripped from them.
     * @return flags without optimism
     */
    static int nonOptimisticFlags(final int flags) {
        return flags & ~(CALLSITE_OPTIMISTIC | -1 << CALLSITE_PROGRAM_POINT_SHIFT);
    }

    @Override
    public boolean enterContinueNode(final ContinueNode continueNode) {
        return enterJumpStatement(continueNode);
    }

    @Override
    public boolean enterEmptyNode(final EmptyNode emptyNode) {
        // Don't even record the line number, it's irrelevant as there's no code.
        return false;
    }

    @Override
    public boolean enterExpressionStatement(final ExpressionStatement expressionStatement) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(expressionStatement);

        loadAndDiscard(expressionStatement.getExpression());
        assert method.getStackSize() == 0 : "stack not empty in " + expressionStatement;

        return false;
    }

    @Override
    public boolean enterBlockStatement(final BlockStatement blockStatement) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(blockStatement);

        blockStatement.getBlock().accept(this);

        return false;
    }

    @Override
    public boolean enterForNode(final ForNode forNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(forNode);
        if (forNode.isForInOrOf()) {
            enterForIn(forNode);
        } else {
            final Expression init = forNode.getInit();
            if (init != null) {
                loadAndDiscard(init);
            }
            enterForOrWhile(forNode, forNode.getModify());
        }

        return false;
    }

    private void enterForIn(final ForNode forNode) {
        loadExpression(forNode.getModify(), TypeBounds.OBJECT);
        if (forNode.isForEach()) {
            method.invoke(ScriptRuntime.TO_VALUE_ITERATOR);
        } else if (forNode.isForIn()) {
            method.invoke(ScriptRuntime.TO_PROPERTY_ITERATOR);
        } else if (forNode.isForOf()) {
            method.invoke(ScriptRuntime.TO_ES6_ITERATOR);
        } else {
            throw new IllegalArgumentException("Unexpected for node");
        }
        final Symbol iterSymbol = forNode.getIterator();
        final int iterSlot = iterSymbol.getSlot(Type.OBJECT);
        method.store(iterSymbol, ITERATOR_TYPE);

        method.beforeJoinPoint(forNode);

        final Label continueLabel = forNode.getContinueLabel();
        final Label breakLabel    = forNode.getBreakLabel();

        method.label(continueLabel);
        method.load(ITERATOR_TYPE, iterSlot);
        method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "hasNext", boolean.class));
        final JoinPredecessorExpression test = forNode.getTest();
        final Block body = forNode.getBody();
        if(LocalVariableConversion.hasLiveConversion(test)) {
            final Label afterConversion = new Label("for_in_after_test_conv");
            method.ifne(afterConversion);
            method.beforeJoinPoint(test);
            method._goto(breakLabel);
            method.label(afterConversion);
        } else {
            method.ifeq(breakLabel);
        }

        new Store<Expression>(forNode.getInit()) {
            @Override
            protected void storeNonDiscard() {
                // This expression is neither part of a discard, nor needs to be left on the stack after it was
                // stored, so we override storeNonDiscard to be a no-op.
            }

            @Override
            protected void evaluate() {
                new OptimisticOperation((Optimistic)forNode.getInit(), TypeBounds.UNBOUNDED) {
                    @Override
                    void loadStack() {
                        method.load(ITERATOR_TYPE, iterSlot);
                    }

                    @Override
                    void consumeStack() {
                        method.invoke(interfaceCallNoLookup(ITERATOR_CLASS, "next", Object.class));
                        convertOptimisticReturnValue();
                    }
                }.emit();
            }
        }.store();
        body.accept(this);

        if (forNode.needsScopeCreator() && lc.getCurrentBlock().providesScopeCreator()) {
            // for-in loops with lexical declaration need a new scope for each iteration.
            final FieldObjectCreator<?> creator = scopeObjectCreators.peek();
            assert creator != null;
            creator.createForInIterationScope(method);
            method.storeCompilerConstant(SCOPE);
        }

        if(method.isReachable()) {
            method._goto(continueLabel);
        }
        method.label(breakLabel);
    }

    
Initialize the slots in a frame to undefined.
Params:
block – block with local vars./**
     * Initialize the slots in a frame to undefined.
     *
     * @param block block with local vars.
     */
    private void initLocals(final Block block) {
        lc.onEnterBlock(block);

        final boolean isFunctionBody = lc.isFunctionBody();
        final FunctionNode function = lc.getCurrentFunction();
        if (isFunctionBody) {
            initializeMethodParameters(function);
            if(!function.isVarArg()) {
                expandParameterSlots(function);
            }
            if (method.hasScope()) {
                if (function.needsParentScope()) {
                    method.loadCompilerConstant(CALLEE);
                    method.invoke(ScriptFunction.GET_SCOPE);
                } else {
                    assert function.hasScopeBlock();
                    method.loadNull();
                }
                method.storeCompilerConstant(SCOPE);
            }
            if (function.needsArguments()) {
                initArguments(function);
            }
        }

        /*
         * Determine if block needs scope, if not, just do initSymbols for this block.
         */
        if (block.needsScope()) {
            /*
             * Determine if function is varargs and consequently variables have to
             * be in the scope.
             */
            final boolean varsInScope = function.allVarsInScope();

            // TODO for LET we can do better: if *block* does not contain any eval/with, we don't need its vars in scope.

            final boolean hasArguments = function.needsArguments();
            final List<MapTuple<Symbol>> tuples = new ArrayList<>();
            final Iterator<IdentNode> paramIter = function.getParameters().iterator();
            for (final Symbol symbol : block.getSymbols()) {
                if (symbol.isInternal() || symbol.isThis()) {
                    continue;
                }

                if (symbol.isVar()) {
                    assert !varsInScope || symbol.isScope();
                    if (varsInScope || symbol.isScope()) {
                        assert symbol.isScope()   : "scope for " + symbol + " should have been set in Lower already " + function.getName();
                        assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already" + function.getName();

                        //this tuple will not be put fielded, as it has no value, just a symbol
                        tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, null));
                    } else {
                        assert symbol.hasSlot() || symbol.slotCount() == 0 : symbol + " should have a slot only, no scope";
                    }
                } else if (symbol.isParam() && (varsInScope || hasArguments || symbol.isScope())) {
                    assert symbol.isScope()   : "scope for " + symbol + " should have been set in AssignSymbols already " + function.getName() + " varsInScope="+varsInScope+" hasArguments="+hasArguments+" symbol.isScope()=" + symbol.isScope();
                    assert !(hasArguments && symbol.hasSlot())  : "slot for " + symbol + " should have been removed in Lower already " + function.getName();

                    final Type   paramType;
                    final Symbol paramSymbol;

                    if (hasArguments) {
                        assert !symbol.hasSlot()  : "slot for " + symbol + " should have been removed in Lower already ";
                        paramSymbol = null;
                        paramType   = null;
                    } else {
                        paramSymbol = symbol;
                        // NOTE: We're relying on the fact here that Block.symbols is a LinkedHashMap, hence it will
                        // return symbols in the order they were defined, and parameters are defined in the same order
                        // they appear in the function. That's why we can have a single pass over the parameter list
                        // with an iterator, always just scanning forward for the next parameter that matches the symbol
                        // name.
                        for(;;) {
                            final IdentNode nextParam = paramIter.next();
                            if(nextParam.getName().equals(symbol.getName())) {
                                paramType = nextParam.getType();
                                break;
                            }
                        }
                    }

                    tuples.add(new MapTuple<Symbol>(symbol.getName(), symbol, paramType, paramSymbol) {
                        //this symbol will be put fielded, we can't initialize it as undefined with a known type
                        @Override
                        public Class<?> getValueType() {
                            if (!useDualFields() ||  value == null || paramType == null || paramType.isBoolean()) {
                                return Object.class;
                            }
                            return paramType.getTypeClass();
                        }
                    });
                }
            }

            /*
             * Create a new object based on the symbols and values, generate
             * bootstrap code for object
             */
            final FieldObjectCreator<Symbol> creator = new FieldObjectCreator<Symbol>(this, tuples, true, hasArguments) {
                @Override
                protected void loadValue(final Symbol value, final Type type) {
                    method.load(value, type);
                }
            };
            creator.makeObject(method);
            if (block.providesScopeCreator()) {
                scopeObjectCreators.push(creator);
            }
            // program function: merge scope into global
            if (isFunctionBody && function.isProgram()) {
                method.invoke(ScriptRuntime.MERGE_SCOPE);
            }

            method.storeCompilerConstant(SCOPE);
            if(!isFunctionBody) {
                // Function body doesn't need a try/catch to restore scope, as it'd be a dead store anyway. Allowing it
                // actually causes issues with UnwarrantedOptimismException handlers as ASM will sort this handler to
                // the top of the exception handler table, so it'll be triggered instead of the UOE handlers.
                final Label scopeEntryLabel = new Label("scope_entry");
                scopeEntryLabels.push(scopeEntryLabel);
                method.label(scopeEntryLabel);
            }
        } else if (isFunctionBody && function.isVarArg()) {
            // Since we don't have a scope, parameters didn't get assigned array indices by the FieldObjectCreator, so
            // we need to assign them separately here.
            int nextParam = 0;
            for (final IdentNode param : function.getParameters()) {
                param.getSymbol().setFieldIndex(nextParam++);
            }
        }

        // Debugging: print symbols? @see --print-symbols flag
        printSymbols(block, function, (isFunctionBody ? "Function " : "Block in ") + (function.getIdent() == null ? "<anonymous>" : function.getIdent().getName()));
    }

    
Incoming method parameters are always declared on method entry; declare them in the local variable table.
Params:
function – function for which code is being generated./**
     * Incoming method parameters are always declared on method entry; declare them in the local variable table.
     * @param function function for which code is being generated.
     */
    private void initializeMethodParameters(final FunctionNode function) {
        final Label functionStart = new Label("fn_start");
        method.label(functionStart);
        int nextSlot = 0;
        if(function.needsCallee()) {
            initializeInternalFunctionParameter(CALLEE, function, functionStart, nextSlot++);
        }
        initializeInternalFunctionParameter(THIS, function, functionStart, nextSlot++);
        if(function.isVarArg()) {
            initializeInternalFunctionParameter(VARARGS, function, functionStart, nextSlot++);
        } else {
            for(final IdentNode param: function.getParameters()) {
                final Symbol symbol = param.getSymbol();
                if(symbol.isBytecodeLocal()) {
                    method.initializeMethodParameter(symbol, param.getType(), functionStart);
                }
            }
        }
    }

    private void initializeInternalFunctionParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
        final Symbol symbol = initializeInternalFunctionOrSplitParameter(cc, fn, functionStart, slot);
        // Internal function params (:callee, this, and :varargs) are never expanded to multiple slots
        assert symbol.getFirstSlot() == slot;
    }

    private Symbol initializeInternalFunctionOrSplitParameter(final CompilerConstants cc, final FunctionNode fn, final Label functionStart, final int slot) {
        final Symbol symbol = fn.getBody().getExistingSymbol(cc.symbolName());
        final Type type = Type.typeFor(cc.type());
        method.initializeMethodParameter(symbol, type, functionStart);
        method.onLocalStore(type, slot);
        return symbol;
    }

    
Parameters come into the method packed into local variable slots next to each other. Nashorn on the other hand
can use 1-6 slots for a local variable depending on all the types it needs to store. When this method is invoked,
the symbols are already allocated such wider slots, but the values are still in tightly packed incoming slots,
and we need to spread them into their new locations.
Params:
function – the function for which parameter-spreading code needs to be emitted/**
     * Parameters come into the method packed into local variable slots next to each other. Nashorn on the other hand
     * can use 1-6 slots for a local variable depending on all the types it needs to store. When this method is invoked,
     * the symbols are already allocated such wider slots, but the values are still in tightly packed incoming slots,
     * and we need to spread them into their new locations.
     * @param function the function for which parameter-spreading code needs to be emitted
     */
    private void expandParameterSlots(final FunctionNode function) {
        final List<IdentNode> parameters = function.getParameters();
        // Calculate the total number of incoming parameter slots
        int currentIncomingSlot = function.needsCallee() ? 2 : 1;
        for(final IdentNode parameter: parameters) {
            currentIncomingSlot += parameter.getType().getSlots();
        }
        // Starting from last parameter going backwards, move the parameter values into their new slots.
        for(int i = parameters.size(); i-- > 0;) {
            final IdentNode parameter = parameters.get(i);
            final Type parameterType = parameter.getType();
            final int typeWidth = parameterType.getSlots();
            currentIncomingSlot -= typeWidth;
            final Symbol symbol = parameter.getSymbol();
            final int slotCount = symbol.slotCount();
            assert slotCount > 0;
            // Scoped parameters must not hold more than one value
            assert symbol.isBytecodeLocal() || slotCount == typeWidth;

            // Mark it as having its value stored into it by the method invocation.
            method.onLocalStore(parameterType, currentIncomingSlot);
            if(currentIncomingSlot != symbol.getSlot(parameterType)) {
                method.load(parameterType, currentIncomingSlot);
                method.store(symbol, parameterType);
            }
        }
    }

    private void initArguments(final FunctionNode function) {
        method.loadCompilerConstant(VARARGS);
        if (function.needsCallee()) {
            method.loadCompilerConstant(CALLEE);
        } else {
            // If function is strict mode, "arguments.callee" is not populated, so we don't necessarily need the
            // caller.
            assert function.isStrict();
            method.loadNull();
        }
        method.load(function.getParameters().size());
        globalAllocateArguments();
        method.storeCompilerConstant(ARGUMENTS);
    }

    private boolean skipFunction(final FunctionNode functionNode) {
        final ScriptEnvironment env = compiler.getScriptEnvironment();
        final boolean lazy = env._lazy_compilation;
        final boolean onDemand = compiler.isOnDemandCompilation();

        // If this is on-demand or lazy compilation, don't compile a nested (not topmost) function.
        if((onDemand || lazy) && lc.getOutermostFunction() != functionNode) {
            return true;
        }

        // If lazy compiling with optimistic types, don't compile the program eagerly either. It will soon be
        // invalidated anyway. In presence of a class cache, this further means that an obsoleted program version
        // lingers around. Also, currently loading previously persisted optimistic types information only works if
        // we're on-demand compiling a function, so with this strategy the :program method can also have the warmup
        // benefit of using previously persisted types.
        //
        // NOTE that this means the first compiled class will effectively just have a :createProgramFunction method, and
        // the RecompilableScriptFunctionData (RSFD) object in its constants array. It won't even have the :program
        // method. This is by design. It does mean that we're wasting one compiler execution (and we could minimize this
        // by just running it up to scope depth calculation, which creates the RSFDs and then this limited codegen).
        // We could emit an initial separate compile unit with the initial version of :program in it to better utilize
        // the compilation pipeline, but that would need more invasive changes, as currently the assumption that
        // :program is emitted into the first compilation unit of the function lives in many places.
        return !onDemand && lazy && env._optimistic_types && functionNode.isProgram();
    }

    @Override
    public boolean enterFunctionNode(final FunctionNode functionNode) {
        if (skipFunction(functionNode)) {
            // In case we are not generating code for the function, we must create or retrieve the function object and
            // load it on the stack here.
            newFunctionObject(functionNode, false);
            return false;
        }

        final String fnName = functionNode.getName();

        // NOTE: we only emit the method for a function with the given name once. We can have multiple functions with
        // the same name as a result of inlining finally blocks. However, in the future -- with type specialization,
        // notably -- we might need to check for both name *and* signature. Of course, even that might not be
        // sufficient; the function might have a code dependency on the type of the variables in its enclosing scopes,
        // and the type of such a variable can be different in catch and finally blocks. So, in the future we will have
        // to decide to either generate a unique method for each inlined copy of the function, maybe figure out its
        // exact type closure and deduplicate based on that, or just decide that functions in finally blocks aren't
        // worth it, and generate one method with most generic type closure.
        if (!emittedMethods.contains(fnName)) {
            log.info("=== BEGIN ", fnName);

            assert functionNode.getCompileUnit() != null : "no compile unit for " + fnName + " " + Debug.id(functionNode);
            unit = lc.pushCompileUnit(functionNode.getCompileUnit());
            assert lc.hasCompileUnits();

            final ClassEmitter classEmitter = unit.getClassEmitter();
            pushMethodEmitter(isRestOf() ? classEmitter.restOfMethod(functionNode) : classEmitter.method(functionNode));
            method.setPreventUndefinedLoad();
            if(useOptimisticTypes()) {
                lc.pushUnwarrantedOptimismHandlers();
            }

            // new method - reset last line number
            lastLineNumber = -1;

            method.begin();

            if (isRestOf()) {
                assert continuationInfo == null;
                continuationInfo = new ContinuationInfo();
                method.gotoLoopStart(continuationInfo.getHandlerLabel());
            }
        }

        return true;
    }

    private void pushMethodEmitter(final MethodEmitter newMethod) {
        method = lc.pushMethodEmitter(newMethod);
        catchLabels.push(METHOD_BOUNDARY);
    }

    private void popMethodEmitter() {
        method = lc.popMethodEmitter(method);
        assert catchLabels.peek() == METHOD_BOUNDARY;
        catchLabels.pop();
    }

    @Override
    public Node leaveFunctionNode(final FunctionNode functionNode) {
        try {
            final boolean markOptimistic;
            if (emittedMethods.add(functionNode.getName())) {
                markOptimistic = generateUnwarrantedOptimismExceptionHandlers(functionNode);
                generateContinuationHandler();
                method.end(); // wrap up this method
                unit   = lc.popCompileUnit(functionNode.getCompileUnit());
                popMethodEmitter();
                log.info("=== END ", functionNode.getName());
            } else {
                markOptimistic = false;
            }

            FunctionNode newFunctionNode = functionNode;
            if (markOptimistic) {
                newFunctionNode = newFunctionNode.setFlag(lc, FunctionNode.IS_DEOPTIMIZABLE);
            }

            newFunctionObject(newFunctionNode, true);
            return newFunctionNode;
        } catch (final Throwable t) {
            Context.printStackTrace(t);
            final VerifyError e = new VerifyError("Code generation bug in \"" + functionNode.getName() + "\": likely stack misaligned: " + t + " " + functionNode.getSource().getName());
            e.initCause(t);
            throw e;
        }
    }

    @Override
    public boolean enterIfNode(final IfNode ifNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(ifNode);

        final Expression test = ifNode.getTest();
        final Block pass = ifNode.getPass();
        final Block fail = ifNode.getFail();

        if (Expression.isAlwaysTrue(test)) {
            loadAndDiscard(test);
            pass.accept(this);
            return false;
        } else if (Expression.isAlwaysFalse(test)) {
            loadAndDiscard(test);
            if (fail != null) {
                fail.accept(this);
            }
            return false;
        }

        final boolean hasFailConversion = LocalVariableConversion.hasLiveConversion(ifNode);

        final Label failLabel  = new Label("if_fail");
        final Label afterLabel = (fail == null && !hasFailConversion) ? null : new Label("if_done");

        emitBranch(test, failLabel, false);

        pass.accept(this);
        if(method.isReachable() && afterLabel != null) {
            method._goto(afterLabel); //don't fallthru to fail block
        }
        method.label(failLabel);

        if (fail != null) {
            fail.accept(this);
        } else if(hasFailConversion) {
            method.beforeJoinPoint(ifNode);
        }

        if(afterLabel != null && afterLabel.isReachable()) {
            method.label(afterLabel);
        }

        return false;
    }

    private void emitBranch(final Expression test, final Label label, final boolean jumpWhenTrue) {
        new BranchOptimizer(this, method).execute(test, label, jumpWhenTrue);
    }

    private void enterStatement(final Statement statement) {
        lineNumber(statement);
    }

    private void lineNumber(final Statement statement) {
        lineNumber(statement.getLineNumber());
    }

    private void lineNumber(final int lineNumber) {
        if (lineNumber != lastLineNumber && lineNumber != Node.NO_LINE_NUMBER) {
            method.lineNumber(lineNumber);
            lastLineNumber = lineNumber;
        }
    }

    int getLastLineNumber() {
        return lastLineNumber;
    }

    
Load a list of nodes as an array of a specific type
The array will contain the visited nodes.
Params:
arrayLiteralNode – the array of contents
arrayType –        the type of the array, e.g. ARRAY_NUMBER or ARRAY_OBJECT/**
     * Load a list of nodes as an array of a specific type
     * The array will contain the visited nodes.
     *
     * @param arrayLiteralNode the array of contents
     * @param arrayType        the type of the array, e.g. ARRAY_NUMBER or ARRAY_OBJECT
     */
    private void loadArray(final ArrayLiteralNode arrayLiteralNode, final ArrayType arrayType) {
        assert arrayType == Type.INT_ARRAY || arrayType == Type.NUMBER_ARRAY || arrayType == Type.OBJECT_ARRAY;

        final Expression[]     nodes    = arrayLiteralNode.getValue();
        final Object           presets  = arrayLiteralNode.getPresets();
        final int[]            postsets = arrayLiteralNode.getPostsets();
        final List<Splittable.SplitRange> ranges   = arrayLiteralNode.getSplitRanges();

        loadConstant(presets);

        final Type elementType = arrayType.getElementType();

        if (ranges != null) {

            loadSplitLiteral(new SplitLiteralCreator() {
                @Override
                public void populateRange(final MethodEmitter method, final Type type, final int slot, final int start, final int end) {
                    for (int i = start; i < end; i++) {
                        method.load(type, slot);
                        storeElement(nodes, elementType, postsets[i]);
                    }
                    method.load(type, slot);
                }
            }, ranges, arrayType);

            return;
        }

        if(postsets.length > 0) {
            final int arraySlot = method.getUsedSlotsWithLiveTemporaries();
            method.storeTemp(arrayType, arraySlot);
            for (final int postset : postsets) {
                method.load(arrayType, arraySlot);
                storeElement(nodes, elementType, postset);
            }
            method.load(arrayType, arraySlot);
        }
    }

    private void storeElement(final Expression[] nodes, final Type elementType, final int index) {
        method.load(index);

        final Expression element = nodes[index];

        if (element == null) {
            method.loadEmpty(elementType);
        } else {
            loadExpressionAsType(element, elementType);
        }

        method.arraystore();
    }

    private MethodEmitter loadArgsArray(final List<Expression> args) {
        final Object[] array = new Object[args.size()];
        loadConstant(array);

        for (int i = 0; i < args.size(); i++) {
            method.dup();
            method.load(i);
            loadExpression(args.get(i), TypeBounds.OBJECT); // variable arity methods always take objects
            method.arraystore();
        }

        return method;
    }

    
Load a constant from the constant array. This is only public to be callable from the objects
subpackage. Do not call directly.
Params:
string – string to load/**
     * Load a constant from the constant array. This is only public to be callable from the objects
     * subpackage. Do not call directly.
     *
     * @param string string to load
     */
    void loadConstant(final String string) {
        final String       unitClassName = unit.getUnitClassName();
        final ClassEmitter classEmitter  = unit.getClassEmitter();
        final int          index         = compiler.getConstantData().add(string);

        method.load(index);
        method.invokestatic(unitClassName, GET_STRING.symbolName(), methodDescriptor(String.class, int.class));
        classEmitter.needGetConstantMethod(String.class);
    }

    
Load a constant from the constant array. This is only public to be callable from the objects
subpackage. Do not call directly.
Params:
object – object to load/**
     * Load a constant from the constant array. This is only public to be callable from the objects
     * subpackage. Do not call directly.
     *
     * @param object object to load
     */
    void loadConstant(final Object object) {
        loadConstant(object, unit, method);
    }

    private void loadConstant(final Object object, final CompileUnit compileUnit, final MethodEmitter methodEmitter) {
        final String       unitClassName = compileUnit.getUnitClassName();
        final ClassEmitter classEmitter  = compileUnit.getClassEmitter();
        final int          index         = compiler.getConstantData().add(object);
        final Class<?>     cls           = object.getClass();

        if (cls == PropertyMap.class) {
            methodEmitter.load(index);
            methodEmitter.invokestatic(unitClassName, GET_MAP.symbolName(), methodDescriptor(PropertyMap.class, int.class));
            classEmitter.needGetConstantMethod(PropertyMap.class);
        } else if (cls.isArray()) {
            methodEmitter.load(index);
            final String methodName = ClassEmitter.getArrayMethodName(cls);
            methodEmitter.invokestatic(unitClassName, methodName, methodDescriptor(cls, int.class));
            classEmitter.needGetConstantMethod(cls);
        } else {
            methodEmitter.loadConstants().load(index).arrayload();
            if (object instanceof ArrayData) {
                methodEmitter.checkcast(ArrayData.class);
                methodEmitter.invoke(virtualCallNoLookup(ArrayData.class, "copy", ArrayData.class));
            } else if (cls != Object.class) {
                methodEmitter.checkcast(cls);
            }
        }
    }

    private void loadConstantsAndIndex(final Object object, final MethodEmitter methodEmitter) {
        methodEmitter.loadConstants().load(compiler.getConstantData().add(object));
    }

    // literal values
    private void loadLiteral(final LiteralNode<?> node, final TypeBounds resultBounds) {
        final Object value = node.getValue();

        if (value == null) {
            method.loadNull();
        } else if (value instanceof Undefined) {
            method.loadUndefined(resultBounds.within(Type.OBJECT));
        } else if (value instanceof String) {
            final String string = (String)value;

            if (string.length() > MethodEmitter.LARGE_STRING_THRESHOLD / 3) { // 3 == max bytes per encoded char
                loadConstant(string);
            } else {
                method.load(string);
            }
        } else if (value instanceof RegexToken) {
            loadRegex((RegexToken)value);
        } else if (value instanceof Boolean) {
            method.load((Boolean)value);
        } else if (value instanceof Integer) {
            if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
                method.load((Integer)value);
                method.convert(Type.OBJECT);
            } else if(!resultBounds.canBeNarrowerThan(Type.NUMBER)) {
                method.load(((Integer)value).doubleValue());
            } else {
                method.load((Integer)value);
            }
        } else if (value instanceof Double) {
            if(!resultBounds.canBeNarrowerThan(Type.OBJECT)) {
                method.load((Double)value);
                method.convert(Type.OBJECT);
            } else {
                method.load((Double)value);
            }
        } else if (node instanceof ArrayLiteralNode) {
            final ArrayLiteralNode arrayLiteral = (ArrayLiteralNode)node;
            final ArrayType atype = arrayLiteral.getArrayType();
            loadArray(arrayLiteral, atype);
            globalAllocateArray(atype);
        } else {
            throw new UnsupportedOperationException("Unknown literal for " + node.getClass() + " " + value.getClass() + " " + value);
        }
    }

    private MethodEmitter loadRegexToken(final RegexToken value) {
        method.load(value.getExpression());
        method.load(value.getOptions());
        return globalNewRegExp();
    }

    private MethodEmitter loadRegex(final RegexToken regexToken) {
        if (regexFieldCount > MAX_REGEX_FIELDS) {
            return loadRegexToken(regexToken);
        }
        // emit field
        final String       regexName    = lc.getCurrentFunction().uniqueName(REGEX_PREFIX.symbolName());
        final ClassEmitter classEmitter = unit.getClassEmitter();

        classEmitter.field(EnumSet.of(PRIVATE, STATIC), regexName, Object.class);
        regexFieldCount++;

        // get field, if null create new regex, finally clone regex object
        method.getStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));
        method.dup();
        final Label cachedLabel = new Label("cached");
        method.ifnonnull(cachedLabel);

        method.pop();
        loadRegexToken(regexToken);
        method.dup();
        method.putStatic(unit.getUnitClassName(), regexName, typeDescriptor(Object.class));

        method.label(cachedLabel);
        globalRegExpCopy();

        return method;
    }

    
Check if a property value contains a particular program point
Params:
value – value
pp –    program point
Returns:
true if it's there./**
     * Check if a property value contains a particular program point
     * @param value value
     * @param pp    program point
     * @return true if it's there.
     */
    private static boolean propertyValueContains(final Expression value, final int pp) {
        return new Supplier<Boolean>() {
            boolean contains;

            @Override
            public Boolean get() {
                value.accept(new SimpleNodeVisitor() {
                    @Override
                    public boolean enterFunctionNode(final FunctionNode functionNode) {
                        return false;
                    }

                    @Override
                    public boolean enterDefault(final Node node) {
                        if (contains) {
                            return false;
                        }
                        if (node instanceof Optimistic && ((Optimistic)node).getProgramPoint() == pp) {
                            contains = true;
                            return false;
                        }
                        return true;
                    }
                });

                return contains;
            }
        }.get();
    }

    private void loadObjectNode(final ObjectNode objectNode) {
        final List<PropertyNode> elements = objectNode.getElements();

        final List<MapTuple<Expression>> tuples = new ArrayList<>();
        // List below will contain getter/setter properties and properties with computed keys (ES6)
        final List<PropertyNode> specialProperties = new ArrayList<>();
        final int ccp = getCurrentContinuationEntryPoint();
        final List<Splittable.SplitRange> ranges = objectNode.getSplitRanges();

        Expression protoNode = null;
        boolean restOfProperty = false;

        for (final PropertyNode propertyNode : elements) {
            final Expression value = propertyNode.getValue();
            final String key = propertyNode.getKeyName();
            final boolean isComputedOrAccessor = propertyNode.isComputed() || value == null;

            // Just use a pseudo-symbol. We just need something non null; use the name and zero flags.
            final Symbol symbol = isComputedOrAccessor ? null : new Symbol(key, 0);

            if (isComputedOrAccessor) {
                // Properties with computed names or getter/setters need special handling.
                specialProperties.add(propertyNode);
            } else if (propertyNode.getKey() instanceof IdentNode &&
                       key.equals(ScriptObject.PROTO_PROPERTY_NAME)) {
                // ES6 draft compliant __proto__ inside object literal
                // Identifier key and name is __proto__
                protoNode = value;
                continue;
            }

            restOfProperty |=
                value != null &&
                isValid(ccp) &&
                propertyValueContains(value, ccp);

            //for literals, a value of null means object type, i.e. the value null or getter setter function
            //(I think)
            final Class<?> valueType = (!useDualFields() || isComputedOrAccessor || value.getType().isBoolean()) ? Object.class : value.getType().getTypeClass();
            tuples.add(new MapTuple<Expression>(key, symbol, Type.typeFor(valueType), value) {
                @Override
                public Class<?> getValueType() {
                    return type.getTypeClass();
                }
            });
        }

        final ObjectCreator<?> oc;
        if (elements.size() > OBJECT_SPILL_THRESHOLD) {
            oc = new SpillObjectCreator(this, tuples);
        } else {
            oc = new FieldObjectCreator<Expression>(this, tuples) {
                @Override
                protected void loadValue(final Expression node, final Type type) {
                    // Use generic type in order to avoid conversion between object types
                    loadExpressionAsType(node, Type.generic(type));
                }};
        }

        if (ranges != null) {
            oc.createObject(method);
            loadSplitLiteral(oc, ranges, Type.typeFor(oc.getAllocatorClass()));
        } else {
            oc.makeObject(method);
        }

        //if this is a rest of method and our continuation point was found as one of the values
        //in the properties above, we need to reset the map to oc.getMap() in the continuation
        //handler
        if (restOfProperty) {
            final ContinuationInfo ci = getContinuationInfo();
            ci.setObjectLiteralMap(method.getStackSize(), oc.getMap());
        }

        method.dup();
        if (protoNode != null) {
            loadExpressionAsObject(protoNode);
            // take care of { __proto__: 34 } or some such!
            method.convert(Type.OBJECT);
            method.invoke(ScriptObject.SET_PROTO_FROM_LITERAL);
        } else {
            method.invoke(ScriptObject.SET_GLOBAL_OBJECT_PROTO);
        }

        for (final PropertyNode propertyNode : specialProperties) {

            method.dup();

            if (propertyNode.isComputed()) {
                assert propertyNode.getKeyName() == null;
                loadExpressionAsObject(propertyNode.getKey());
            } else {
                method.loadKey(propertyNode.getKey());
            }

            if (propertyNode.getValue() != null) {
                loadExpressionAsObject(propertyNode.getValue());
                method.load(0);
                method.invoke(ScriptObject.GENERIC_SET);
            } else {
                final FunctionNode getter = propertyNode.getGetter();
                final FunctionNode setter = propertyNode.getSetter();

                assert getter != null || setter != null;

                if (getter == null) {
                    method.loadNull();
                } else {
                    getter.accept(this);
                }

                if (setter == null) {
                    method.loadNull();
                } else {
                    setter.accept(this);
                }

                method.invoke(ScriptObject.SET_USER_ACCESSORS);
            }
        }
    }

    @Override
    public boolean enterReturnNode(final ReturnNode returnNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(returnNode);

        final Type returnType = lc.getCurrentFunction().getReturnType();

        final Expression expression = returnNode.getExpression();
        if (expression != null) {
            loadExpressionUnbounded(expression);
        } else {
            method.loadUndefined(returnType);
        }

        method._return(returnType);

        return false;
    }

    private boolean undefinedCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
        final Request request = runtimeNode.getRequest();

        if (!Request.isUndefinedCheck(request)) {
            return false;
        }

        final Expression lhs = args.get(0);
        final Expression rhs = args.get(1);

        final Symbol lhsSymbol = lhs instanceof IdentNode ? ((IdentNode)lhs).getSymbol() : null;
        final Symbol rhsSymbol = rhs instanceof IdentNode ? ((IdentNode)rhs).getSymbol() : null;
        // One must be a "undefined" identifier, otherwise we can't get here
        assert lhsSymbol != null || rhsSymbol != null;

        final Symbol undefinedSymbol;
        if (isUndefinedSymbol(lhsSymbol)) {
            undefinedSymbol = lhsSymbol;
        } else {
            assert isUndefinedSymbol(rhsSymbol);
            undefinedSymbol = rhsSymbol;
        }

        assert undefinedSymbol != null; //remove warning
        if (!undefinedSymbol.isScope()) {
            return false; //disallow undefined as local var or parameter
        }

        if (lhsSymbol == undefinedSymbol && lhs.getType().isPrimitive()) {
            //we load the undefined first. never mind, because this will deoptimize anyway
            return false;
        }

        if(isDeoptimizedExpression(lhs)) {
            // This is actually related to "lhs.getType().isPrimitive()" above: any expression being deoptimized in
            // the current chain of rest-of compilations used to have a type narrower than Object (so it was primitive).
            // We must not perform undefined check specialization for them, as then we'd violate the basic rule of
            // "Thou shalt not alter the stack shape between a deoptimized method and any of its (transitive) rest-ofs."
            return false;
        }

        //make sure that undefined has not been overridden or scoped as a local var
        //between us and global
        if (!compiler.isGlobalSymbol(lc.getCurrentFunction(), "undefined")) {
            return false;
        }

        final boolean isUndefinedCheck = request == Request.IS_UNDEFINED;
        final Expression expr = undefinedSymbol == lhsSymbol ? rhs : lhs;
        if (expr.getType().isPrimitive()) {
            loadAndDiscard(expr); //throw away lhs, but it still needs to be evaluated for side effects, even if not in scope, as it can be optimistic
            method.load(!isUndefinedCheck);
        } else {
            final Label checkTrue  = new Label("ud_check_true");
            final Label end        = new Label("end");
            loadExpressionAsObject(expr);
            method.loadUndefined(Type.OBJECT);
            method.if_acmpeq(checkTrue);
            method.load(!isUndefinedCheck);
            method._goto(end);
            method.label(checkTrue);
            method.load(isUndefinedCheck);
            method.label(end);
        }

        return true;
    }

    private static boolean isUndefinedSymbol(final Symbol symbol) {
        return symbol != null && "undefined".equals(symbol.getName());
    }

    private static boolean isNullLiteral(final Node node) {
        return node instanceof LiteralNode<?> && ((LiteralNode<?>) node).isNull();
    }

    private boolean nullCheck(final RuntimeNode runtimeNode, final List<Expression> args) {
        final Request request = runtimeNode.getRequest();

        if (!Request.isEQ(request) && !Request.isNE(request)) {
            return false;
        }

        assert args.size() == 2 : "EQ or NE or TYPEOF need two args";

        Expression lhs = args.get(0);
        Expression rhs = args.get(1);

        if (isNullLiteral(lhs)) {
            final Expression tmp = lhs;
            lhs = rhs;
            rhs = tmp;
        }

        if (!isNullLiteral(rhs)) {
            return false;
        }

        if (!lhs.getType().isObject()) {
            return false;
        }

        if(isDeoptimizedExpression(lhs)) {
            // This is actually related to "!lhs.getType().isObject()" above: any expression being deoptimized in
            // the current chain of rest-of compilations used to have a type narrower than Object. We must not
            // perform null check specialization for them, as then we'd no longer be loading aconst_null on stack
            // and thus violate the basic rule of "Thou shalt not alter the stack shape between a deoptimized
            // method and any of its (transitive) rest-ofs."
            // NOTE also that if we had a representation for well-known constants (e.g. null, 0, 1, -1, etc.) in
            // Label$Stack.localLoads then this wouldn't be an issue, as we would never (somewhat ridiculously)
            // allocate a temporary local to hold the result of aconst_null before attempting an optimistic
            // operation.
            return false;
        }

        // this is a null literal check, so if there is implicit coercion
        // involved like {D}x=null, we will fail - this is very rare
        final Label trueLabel  = new Label("trueLabel");
        final Label falseLabel = new Label("falseLabel");
        final Label endLabel   = new Label("end");

        loadExpressionUnbounded(lhs);    //lhs
        final Label popLabel;
        if (!Request.isStrict(request)) {
            method.dup(); //lhs lhs
            popLabel = new Label("pop");
        } else {
            popLabel = null;
        }

        if (Request.isEQ(request)) {
            method.ifnull(!Request.isStrict(request) ? popLabel : trueLabel);
            if (!Request.isStrict(request)) {
                method.loadUndefined(Type.OBJECT);
                method.if_acmpeq(trueLabel);
            }
            method.label(falseLabel);
            method.load(false);
            method._goto(endLabel);
            if (!Request.isStrict(request)) {
                method.label(popLabel);
                method.pop();
            }
            method.label(trueLabel);
            method.load(true);
            method.label(endLabel);
        } else if (Request.isNE(request)) {
            method.ifnull(!Request.isStrict(request) ? popLabel : falseLabel);
            if (!Request.isStrict(request)) {
                method.loadUndefined(Type.OBJECT);
                method.if_acmpeq(falseLabel);
            }
            method.label(trueLabel);
            method.load(true);
            method._goto(endLabel);
            if (!Request.isStrict(request)) {
                method.label(popLabel);
                method.pop();
            }
            method.label(falseLabel);
            method.load(false);
            method.label(endLabel);
        }

        assert runtimeNode.getType().isBoolean();
        method.convert(runtimeNode.getType());

        return true;
    }

    
Was this expression or any of its subexpressions deoptimized in the current recompilation chain of rest-of methods?
Params:
rootExpr – the expression being tested
Returns:
true if the expression or any of its subexpressions was deoptimized in the current recompilation chain./**
     * Was this expression or any of its subexpressions deoptimized in the current recompilation chain of rest-of methods?
     * @param rootExpr the expression being tested
     * @return true if the expression or any of its subexpressions was deoptimized in the current recompilation chain.
     */
    private boolean isDeoptimizedExpression(final Expression rootExpr) {
        if(!isRestOf()) {
            return false;
        }
        return new Supplier<Boolean>() {
            boolean contains;
            @Override
            public Boolean get() {
                rootExpr.accept(new SimpleNodeVisitor() {
                    @Override
                    public boolean enterFunctionNode(final FunctionNode functionNode) {
                        return false;
                    }
                    @Override
                    public boolean enterDefault(final Node node) {
                        if(!contains && node instanceof Optimistic) {
                            final int pp = ((Optimistic)node).getProgramPoint();
                            contains = isValid(pp) && isContinuationEntryPoint(pp);
                        }
                        return !contains;
                    }
                });
                return contains;
            }
        }.get();
    }

    private void loadRuntimeNode(final RuntimeNode runtimeNode) {
        final List<Expression> args = new ArrayList<>(runtimeNode.getArgs());
        if (nullCheck(runtimeNode, args)) {
           return;
        } else if(undefinedCheck(runtimeNode, args)) {
            return;
        }
        // Revert a false undefined check to a strict equality check
        final RuntimeNode newRuntimeNode;
        final Request request = runtimeNode.getRequest();
        if (Request.isUndefinedCheck(request)) {
            newRuntimeNode = runtimeNode.setRequest(request == Request.IS_UNDEFINED ? Request.EQ_STRICT : Request.NE_STRICT);
        } else {
            newRuntimeNode = runtimeNode;
        }

        for (final Expression arg : args) {
            loadExpression(arg, TypeBounds.OBJECT);
        }

        method.invokestatic(
                CompilerConstants.className(ScriptRuntime.class),
                newRuntimeNode.getRequest().toString(),
                new FunctionSignature(
                    false,
                    false,
                    newRuntimeNode.getType(),
                    args.size()).toString());

        method.convert(newRuntimeNode.getType());
    }

    private void defineCommonSplitMethodParameters() {
        defineSplitMethodParameter(0, CALLEE);
        defineSplitMethodParameter(1, THIS);
        defineSplitMethodParameter(2, SCOPE);
    }

    private void defineSplitMethodParameter(final int slot, final CompilerConstants cc) {
        defineSplitMethodParameter(slot, Type.typeFor(cc.type()));
    }

    private void defineSplitMethodParameter(final int slot, final Type type) {
        method.defineBlockLocalVariable(slot, slot + type.getSlots());
        method.onLocalStore(type, slot);
    }

    private void loadSplitLiteral(final SplitLiteralCreator creator, final List<Splittable.SplitRange> ranges, final Type literalType) {
        assert ranges != null;

        // final Type literalType = Type.typeFor(literalClass);
        final MethodEmitter savedMethod     = method;
        final FunctionNode  currentFunction = lc.getCurrentFunction();

        for (final Splittable.SplitRange splitRange : ranges) {
            unit = lc.pushCompileUnit(splitRange.getCompileUnit());

            assert unit != null;
            final String className = unit.getUnitClassName();
            final String name      = currentFunction.uniqueName(SPLIT_PREFIX.symbolName());
            final Class<?> clazz   = literalType.getTypeClass();
            final String signature = methodDescriptor(clazz, ScriptFunction.class, Object.class, ScriptObject.class, clazz);

            pushMethodEmitter(unit.getClassEmitter().method(EnumSet.of(Flag.PUBLIC, Flag.STATIC), name, signature));

            method.setFunctionNode(currentFunction);
            method.begin();

            defineCommonSplitMethodParameters();
            defineSplitMethodParameter(CompilerConstants.SPLIT_ARRAY_ARG.slot(), literalType);

            // NOTE: when this is no longer needed, SplitIntoFunctions will no longer have to add IS_SPLIT
            // to synthetic functions, and FunctionNode.needsCallee() will no longer need to test for isSplit().
            final int literalSlot = fixScopeSlot(currentFunction, 3);

            lc.enterSplitNode();

            creator.populateRange(method, literalType, literalSlot, splitRange.getLow(), splitRange.getHigh());

            method._return();
            lc.exitSplitNode();
            method.end();
            lc.releaseSlots();
            popMethodEmitter();

            assert method == savedMethod;
            method.loadCompilerConstant(CALLEE).swap();
            method.loadCompilerConstant(THIS).swap();
            method.loadCompilerConstant(SCOPE).swap();
            method.invokestatic(className, name, signature);

            unit = lc.popCompileUnit(unit);
        }
    }

    private int fixScopeSlot(final FunctionNode functionNode, final int extraSlot) {
        // TODO hack to move the scope to the expected slot (needed because split methods reuse the same slots as the root method)
        final int actualScopeSlot = functionNode.compilerConstant(SCOPE).getSlot(SCOPE_TYPE);
        final int defaultScopeSlot = SCOPE.slot();
        int newExtraSlot = extraSlot;
        if (actualScopeSlot != defaultScopeSlot) {
            if (actualScopeSlot == extraSlot) {
                newExtraSlot = extraSlot + 1;
                method.defineBlockLocalVariable(newExtraSlot, newExtraSlot + 1);
                method.load(Type.OBJECT, extraSlot);
                method.storeHidden(Type.OBJECT, newExtraSlot);
            } else {
                method.defineBlockLocalVariable(actualScopeSlot, actualScopeSlot + 1);
            }
            method.load(SCOPE_TYPE, defaultScopeSlot);
            method.storeCompilerConstant(SCOPE);
        }
        return newExtraSlot;
    }

    @Override
    public boolean enterSplitReturn(final SplitReturn splitReturn) {
        if (method.isReachable()) {
            method.loadUndefined(lc.getCurrentFunction().getReturnType())._return();
        }
        return false;
    }

    @Override
    public boolean enterSetSplitState(final SetSplitState setSplitState) {
        if (method.isReachable()) {
            method.setSplitState(setSplitState.getState());
        }
        return false;
    }

    @Override
    public boolean enterSwitchNode(final SwitchNode switchNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(switchNode);

        final Expression     expression  = switchNode.getExpression();
        final List<CaseNode> cases       = switchNode.getCases();

        if (cases.isEmpty()) {
            // still evaluate expression for side-effects.
            loadAndDiscard(expression);
            return false;
        }

        final CaseNode defaultCase       = switchNode.getDefaultCase();
        final Label    breakLabel        = switchNode.getBreakLabel();
        final int      liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();

        if (defaultCase != null && cases.size() == 1) {
            // default case only
            assert cases.get(0) == defaultCase;
            loadAndDiscard(expression);
            defaultCase.getBody().accept(this);
            method.breakLabel(breakLabel, liveLocalsOnBreak);
            return false;
        }

        // NOTE: it can still change in the tableswitch/lookupswitch case if there's no default case
        // but we need to add a synthetic default case for local variable conversions
        Label defaultLabel = defaultCase != null ? defaultCase.getEntry() : breakLabel;
        final boolean hasSkipConversion = LocalVariableConversion.hasLiveConversion(switchNode);

        if (switchNode.isUniqueInteger()) {
            // Tree for sorting values.
            final TreeMap<Integer, Label> tree = new TreeMap<>();

            // Build up sorted tree.
            for (final CaseNode caseNode : cases) {
                final Node test = caseNode.getTest();

                if (test != null) {
                    final Integer value = (Integer)((LiteralNode<?>)test).getValue();
                    final Label   entry = caseNode.getEntry();

                    // Take first duplicate.
                    if (!tree.containsKey(value)) {
                        tree.put(value, entry);
                    }
                }
            }

            // Copy values and labels to arrays.
            final int       size   = tree.size();
            final Integer[] values = tree.keySet().toArray(new Integer[0]);
            final Label[]   labels = tree.values().toArray(new Label[0]);

            // Discern low, high and range.
            final int lo    = values[0];
            final int hi    = values[size - 1];
            final long range = (long)hi - (long)lo + 1;

            // Find an unused value for default.
            int deflt = Integer.MIN_VALUE;
            for (final int value : values) {
                if (deflt == value) {
                    deflt++;
                } else if (deflt < value) {
                    break;
                }
            }

            // Load switch expression.
            loadExpressionUnbounded(expression);
            final Type type = expression.getType();

            // If expression not int see if we can convert, if not use deflt to trigger default.
            if (!type.isInteger()) {
                method.load(deflt);
                final Class<?> exprClass = type.getTypeClass();
                method.invoke(staticCallNoLookup(ScriptRuntime.class, "switchTagAsInt", int.class, exprClass.isPrimitive()? exprClass : Object.class, int.class));
            }

            if(hasSkipConversion) {
                assert defaultLabel == breakLabel;
                defaultLabel = new Label("switch_skip");
            }
            // TABLESWITCH needs (range + 3) 32-bit values; LOOKUPSWITCH needs ((size * 2) + 2). Choose the one with
            // smaller representation, favor TABLESWITCH when they're equal size.
            if (range + 1 <= (size * 2) && range <= Integer.MAX_VALUE) {
                final Label[] table = new Label[(int)range];
                Arrays.fill(table, defaultLabel);
                for (int i = 0; i < size; i++) {
                    final int value = values[i];
                    table[value - lo] = labels[i];
                }

                method.tableswitch(lo, hi, defaultLabel, table);
            } else {
                final int[] ints = new int[size];
                for (int i = 0; i < size; i++) {
                    ints[i] = values[i];
                }

                method.lookupswitch(defaultLabel, ints, labels);
            }
            // This is a synthetic "default case" used in absence of actual default case, created if we need to apply
            // local variable conversions if neither case is taken.
            if(hasSkipConversion) {
                method.label(defaultLabel);
                method.beforeJoinPoint(switchNode);
                method._goto(breakLabel);
            }
        } else {
            final Symbol tagSymbol = switchNode.getTag();
            // TODO: we could have non-object tag
            final int tagSlot = tagSymbol.getSlot(Type.OBJECT);
            loadExpressionAsObject(expression);
            method.store(tagSymbol, Type.OBJECT);

            for (final CaseNode caseNode : cases) {
                final Expression test = caseNode.getTest();

                if (test != null) {
                    method.load(Type.OBJECT, tagSlot);
                    loadExpressionAsObject(test);
                    method.invoke(ScriptRuntime.EQ_STRICT);
                    method.ifne(caseNode.getEntry());
                }
            }

            if (defaultCase != null) {
                method._goto(defaultLabel);
            } else {
                method.beforeJoinPoint(switchNode);
                method._goto(breakLabel);
            }
        }

        // First case is only reachable through jump
        assert !method.isReachable();

        for (final CaseNode caseNode : cases) {
            final Label fallThroughLabel;
            if(caseNode.getLocalVariableConversion() != null && method.isReachable()) {
                fallThroughLabel = new Label("fallthrough");
                method._goto(fallThroughLabel);
            } else {
                fallThroughLabel = null;
            }
            method.label(caseNode.getEntry());
            method.beforeJoinPoint(caseNode);
            if(fallThroughLabel != null) {
                method.label(fallThroughLabel);
            }
            caseNode.getBody().accept(this);
        }

        method.breakLabel(breakLabel, liveLocalsOnBreak);

        return false;
    }

    @Override
    public boolean enterThrowNode(final ThrowNode throwNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(throwNode);

        if (throwNode.isSyntheticRethrow()) {
            method.beforeJoinPoint(throwNode);

            //do not wrap whatever this is in an ecma exception, just rethrow it
            final IdentNode exceptionExpr = (IdentNode)throwNode.getExpression();
            final Symbol exceptionSymbol = exceptionExpr.getSymbol();
            method.load(exceptionSymbol, EXCEPTION_TYPE);
            method.checkcast(EXCEPTION_TYPE.getTypeClass());
            method.athrow();
            return false;
        }

        final Source     source     = getCurrentSource();
        final Expression expression = throwNode.getExpression();
        final int        position   = throwNode.position();
        final int        line       = throwNode.getLineNumber();
        final int        column     = source.getColumn(position);

        // NOTE: we first evaluate the expression, and only after it was evaluated do we create the new ECMAException
        // object and then somewhat cumbersomely move it beneath the evaluated expression on the stack. The reason for
        // this is that if expression is optimistic (or contains an optimistic subexpression), we'd potentially access
        // the not-yet-<init>ialized object on the stack from the UnwarrantedOptimismException handler, and bytecode
        // verifier forbids that.
        loadExpressionAsObject(expression);

        method.load(source.getName());
        method.load(line);
        method.load(column);
        method.invoke(ECMAException.CREATE);

        method.beforeJoinPoint(throwNode);
        method.athrow();

        return false;
    }

    private Source getCurrentSource() {
        return lc.getCurrentFunction().getSource();
    }

    @Override
    public boolean enterTryNode(final TryNode tryNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(tryNode);

        final Block       body        = tryNode.getBody();
        final List<Block> catchBlocks = tryNode.getCatchBlocks();
        final Symbol      vmException = tryNode.getException();
        final Label       entry       = new Label("try");
        final Label       recovery    = new Label("catch");
        final Label       exit        = new Label("end_try");
        final Label       skip        = new Label("skip");

        method.canThrow(recovery);
        // Effect any conversions that might be observed at the entry of the catch node before entering the try node.
        // This is because even the first instruction in the try block must be presumed to be able to transfer control
        // to the catch block. Note that this doesn't kill the original values; in this regard it works a lot like
        // conversions of assignments within the try block.
        method.beforeTry(tryNode, recovery);
        method.label(entry);
        catchLabels.push(recovery);
        try {
            body.accept(this);
        } finally {
            assert catchLabels.peek() == recovery;
            catchLabels.pop();
        }

        method.label(exit);
        final boolean bodyCanThrow = exit.isAfter(entry);
        if(!bodyCanThrow) {
            // The body can't throw an exception; don't even bother emitting the catch handlers, they're all dead code.
            return false;
        }

        method._try(entry, exit, recovery, Throwable.class);

        if (method.isReachable()) {
            method._goto(skip);
        }

        for (final Block inlinedFinally : tryNode.getInlinedFinallies()) {
            TryNode.getLabelledInlinedFinallyBlock(inlinedFinally).accept(this);
            // All inlined finallies end with a jump or a return
            assert !method.isReachable();
        }


        method._catch(recovery);
        method.store(vmException, EXCEPTION_TYPE);

        final int catchBlockCount = catchBlocks.size();
        final Label afterCatch = new Label("after_catch");
        for (int i = 0; i < catchBlockCount; i++) {
            assert method.isReachable();
            final Block catchBlock = catchBlocks.get(i);

            // Because of the peculiarities of the flow control, we need to use an explicit push/enterBlock/leaveBlock
            // here.
            lc.push(catchBlock);
            enterBlock(catchBlock);

            final CatchNode  catchNode          = (CatchNode)catchBlocks.get(i).getStatements().get(0);
            final IdentNode  exception          = catchNode.getExceptionIdentifier();
            final Expression exceptionCondition = catchNode.getExceptionCondition();
            final Block      catchBody          = catchNode.getBody();

            new Store<IdentNode>(exception) {
                @Override
                protected void storeNonDiscard() {
                    // This expression is neither part of a discard, nor needs to be left on the stack after it was
                    // stored, so we override storeNonDiscard to be a no-op.
                }

                @Override
                protected void evaluate() {
                    if (catchNode.isSyntheticRethrow()) {
                        method.load(vmException, EXCEPTION_TYPE);
                        return;
                    }
                    /*
                     * If caught object is an instance of ECMAException, then
                     * bind obj.thrown to the script catch var. Or else bind the
                     * caught object itself to the script catch var.
                     */
                    final Label notEcmaException = new Label("no_ecma_exception");
                    method.load(vmException, EXCEPTION_TYPE).dup()._instanceof(ECMAException.class).ifeq(notEcmaException);
                    method.checkcast(ECMAException.class); //TODO is this necessary?
                    method.getField(ECMAException.THROWN);
                    method.label(notEcmaException);
                }
            }.store();

            final boolean isConditionalCatch = exceptionCondition != null;
            final Label nextCatch;
            if (isConditionalCatch) {
                loadExpressionAsBoolean(exceptionCondition);
                nextCatch = new Label("next_catch");
                nextCatch.markAsBreakTarget();
                method.ifeq(nextCatch);
            } else {
                nextCatch = null;
            }

            catchBody.accept(this);
            leaveBlock(catchBlock);
            lc.pop(catchBlock);
            if(nextCatch != null) {
                if(method.isReachable()) {
                    method._goto(afterCatch);
                }
                method.breakLabel(nextCatch, lc.getUsedSlotCount());
            }
        }

        // afterCatch could be the same as skip, except that we need to establish that the vmException is dead.
        method.label(afterCatch);
        if(method.isReachable()) {
            method.markDeadLocalVariable(vmException);
        }
        method.label(skip);

        // Finally body is always inlined elsewhere so it doesn't need to be emitted
        assert tryNode.getFinallyBody() == null;

        return false;
    }

    @Override
    public boolean enterVarNode(final VarNode varNode) {
        if(!method.isReachable()) {
            return false;
        }
        final Expression init = varNode.getInit();
        final IdentNode identNode = varNode.getName();
        final Symbol identSymbol = identNode.getSymbol();
        assert identSymbol != null : "variable node " + varNode + " requires a name with a symbol";
        final boolean needsScope = identSymbol.isScope();

        if (init == null) {
            // Block-scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ).
            // However, don't do this for CONST which always has an initializer except in the special case of
            // for-in/of loops, in which it is initialized in the loop header and should be left untouched here.
            if (needsScope && varNode.isLet()) {
                method.loadCompilerConstant(SCOPE);
                method.loadUndefined(Type.OBJECT);
                final int flags = getScopeCallSiteFlags(identSymbol) | CALLSITE_DECLARE;
                assert isFastScope(identSymbol);
                storeFastScopeVar(identSymbol, flags);
            }
            return false;
        }

        enterStatement(varNode);
        assert method != null;

        if (needsScope) {
            method.loadCompilerConstant(SCOPE);
            loadExpressionUnbounded(init);
            // block scoped variables need a DECLARE flag to signal end of temporal dead zone (TDZ)
            final int flags = getScopeCallSiteFlags(identSymbol) | (varNode.isBlockScoped() ? CALLSITE_DECLARE : 0);
            if (isFastScope(identSymbol)) {
                storeFastScopeVar(identSymbol, flags);
            } else {
                method.dynamicSet(identNode.getName(), flags, false);
            }
        } else {
            final Type identType = identNode.getType();
            if(identType == Type.UNDEFINED) {
                // The initializer is either itself undefined (explicit assignment of undefined to undefined),
                // or the left hand side is a dead variable.
                assert init.getType() == Type.UNDEFINED || identNode.getSymbol().slotCount() == 0;
                loadAndDiscard(init);
                return false;
            }
            loadExpressionAsType(init, identType);
            storeIdentWithCatchConversion(identNode, identType);
        }

        return false;
    }

    private void storeIdentWithCatchConversion(final IdentNode identNode, final Type type) {
        // Assignments happening in try/catch blocks need to ensure that they also store a possibly wider typed value
        // that will be live at the exit from the try block
        final LocalVariableConversion conversion = identNode.getLocalVariableConversion();
        final Symbol symbol = identNode.getSymbol();
        if(conversion != null && conversion.isLive()) {
            assert symbol == conversion.getSymbol();
            assert symbol.isBytecodeLocal();
            // Only a single conversion from the target type to the join type is expected.
            assert conversion.getNext() == null;
            assert conversion.getFrom() == type;
            // We must propagate potential type change to the catch block
            final Label catchLabel = catchLabels.peek();
            assert catchLabel != METHOD_BOUNDARY; // ident conversion only exists in try blocks
            assert catchLabel.isReachable();
            final Type joinType = conversion.getTo();
            final Label.Stack catchStack = catchLabel.getStack();
            final int joinSlot = symbol.getSlot(joinType);
            // With nested try/catch blocks (incl. synthetic ones for finally), we can have a supposed conversion for
            // the exception symbol in the nested catch, but it isn't live in the outer catch block, so prevent doing
            // conversions for it. E.g. in "try { try { ... } catch(e) { e = 1; } } catch(e2) { ... }", we must not
            // introduce an I->O conversion on "e = 1" assignment as "e" is not live in "catch(e2)".
            if(catchStack.getUsedSlotsWithLiveTemporaries() > joinSlot) {
                method.dup();
                method.convert(joinType);
                method.store(symbol, joinType);
                catchLabel.getStack().onLocalStore(joinType, joinSlot, true);
                method.canThrow(catchLabel);
                // Store but keep the previous store live too.
                method.store(symbol, type, false);
                return;
            }
        }

        method.store(symbol, type, true);
    }

    @Override
    public boolean enterWhileNode(final WhileNode whileNode) {
        if(!method.isReachable()) {
            return false;
        }
        if(whileNode.isDoWhile()) {
            enterDoWhile(whileNode);
        } else {
            enterStatement(whileNode);
            enterForOrWhile(whileNode, null);
        }
        return false;
    }

    private void enterForOrWhile(final LoopNode loopNode, final JoinPredecessorExpression modify) {
        // NOTE: the usual pattern for compiling test-first loops is "GOTO test; body; test; IFNE body". We use the less
        // conventional "test; IFEQ break; body; GOTO test; break;". It has one extra unconditional GOTO in each repeat
        // of the loop, but it's not a problem for modern JIT compilers. We do this because our local variable type
        // tracking is unfortunately not really prepared for out-of-order execution, e.g. compiling the following
        // contrived but legal JavaScript code snippet would fail because the test changes the type of "i" from object
        // to double: var i = {valueOf: function() { return 1} }; while(--i >= 0) { ... }
        // Instead of adding more complexity to the local variable type tracking, we instead choose to emit this
        // different code shape.
        final int liveLocalsOnBreak = method.getUsedSlotsWithLiveTemporaries();
        final JoinPredecessorExpression test = loopNode.getTest();
        if(Expression.isAlwaysFalse(test)) {
            loadAndDiscard(test);
            return;
        }

        method.beforeJoinPoint(loopNode);

        final Label continueLabel = loopNode.getContinueLabel();
        final Label repeatLabel = modify != null ? new Label("for_repeat") : continueLabel;
        method.label(repeatLabel);
        final int liveLocalsOnContinue = method.getUsedSlotsWithLiveTemporaries();

        final Block   body                  = loopNode.getBody();
        final Label   breakLabel            = loopNode.getBreakLabel();
        final boolean testHasLiveConversion = test != null && LocalVariableConversion.hasLiveConversion(test);

        if(Expression.isAlwaysTrue(test)) {
            if(test != null) {
                loadAndDiscard(test);
                if(testHasLiveConversion) {
                    method.beforeJoinPoint(test);
                }
            }
        } else if (test != null) {
            if (testHasLiveConversion) {
                emitBranch(test.getExpression(), body.getEntryLabel(), true);
                method.beforeJoinPoint(test);
                method._goto(breakLabel);
            } else {
                emitBranch(test.getExpression(), breakLabel, false);
            }
        }

        body.accept(this);
        if(repeatLabel != continueLabel) {
            emitContinueLabel(continueLabel, liveLocalsOnContinue);
        }

        if (loopNode.hasPerIterationScope() && lc.getCurrentBlock().needsScope()) {
            // ES6 for loops with LET init need a new scope for each iteration. We just create a shallow copy here.
            method.loadCompilerConstant(SCOPE);
            method.invoke(virtualCallNoLookup(ScriptObject.class, "copy", ScriptObject.class));
            method.storeCompilerConstant(SCOPE);
        }

        if(method.isReachable()) {
            if(modify != null) {
                lineNumber(loopNode);
                loadAndDiscard(modify);
                method.beforeJoinPoint(modify);
            }
            method._goto(repeatLabel);
        }

        method.breakLabel(breakLabel, liveLocalsOnBreak);
    }

    private void emitContinueLabel(final Label continueLabel, final int liveLocals) {
        final boolean reachable = method.isReachable();
        method.breakLabel(continueLabel, liveLocals);
        // If we reach here only through a continue statement (e.g. body does not exit normally) then the
        // continueLabel can have extra non-temp symbols (e.g. exception from a try/catch contained in the body). We
        // must make sure those are thrown away.
        if(!reachable) {
            method.undefineLocalVariables(lc.getUsedSlotCount(), false);
        }
    }

    private void enterDoWhile(final WhileNode whileNode) {
        final int liveLocalsOnContinueOrBreak = method.getUsedSlotsWithLiveTemporaries();
        method.beforeJoinPoint(whileNode);

        final Block body = whileNode.getBody();
        body.accept(this);

        emitContinueLabel(whileNode.getContinueLabel(), liveLocalsOnContinueOrBreak);
        if(method.isReachable()) {
            lineNumber(whileNode);
            final JoinPredecessorExpression test = whileNode.getTest();
            final Label bodyEntryLabel = body.getEntryLabel();
            final boolean testHasLiveConversion = LocalVariableConversion.hasLiveConversion(test);
            if(Expression.isAlwaysFalse(test)) {
                loadAndDiscard(test);
                if(testHasLiveConversion) {
                    method.beforeJoinPoint(test);
                }
            } else if(testHasLiveConversion) {
                // If we have conversions after the test in do-while, they need to be effected on both branches.
                final Label beforeExit = new Label("do_while_preexit");
                emitBranch(test.getExpression(), beforeExit, false);
                method.beforeJoinPoint(test);
                method._goto(bodyEntryLabel);
                method.label(beforeExit);
                method.beforeJoinPoint(test);
            } else {
                emitBranch(test.getExpression(), bodyEntryLabel, true);
            }
        }
        method.breakLabel(whileNode.getBreakLabel(), liveLocalsOnContinueOrBreak);
    }


    @Override
    public boolean enterWithNode(final WithNode withNode) {
        if(!method.isReachable()) {
            return false;
        }
        enterStatement(withNode);
        final Expression expression = withNode.getExpression();
        final Block      body       = withNode.getBody();

        // It is possible to have a "pathological" case where the with block does not reference *any* identifiers. It's
        // pointless, but legal. In that case, if nothing else in the method forced the assignment of a slot to the
        // scope object, its' possible that it won't have a slot assigned. In this case we'll only evaluate expression
        // for its side effect and visit the body, and not bother opening and closing a WithObject.
        final boolean hasScope = method.hasScope();

        if (hasScope) {
            method.loadCompilerConstant(SCOPE);
        }

        loadExpressionAsObject(expression);

        final Label tryLabel;
        if (hasScope) {
            // Construct a WithObject if we have a scope
            method.invoke(ScriptRuntime.OPEN_WITH);
            method.storeCompilerConstant(SCOPE);
            tryLabel = new Label("with_try");
            method.label(tryLabel);
        } else {
            // We just loaded the expression for its side effect and to check
            // for null or undefined value.
            globalCheckObjectCoercible();
            tryLabel = null;
        }

        // Always process body
        body.accept(this);

        if (hasScope) {
            // Ensure we always close the WithObject
            final Label endLabel   = new Label("with_end");
            final Label catchLabel = new Label("with_catch");
            final Label exitLabel  = new Label("with_exit");

            method.label(endLabel);
            // Somewhat conservatively presume that if the body is not empty, it can throw an exception. In any case,
            // we must prevent trying to emit a try-catch for empty range, as it causes a verification error.
            final boolean bodyCanThrow = endLabel.isAfter(tryLabel);
            if(bodyCanThrow) {
                method._try(tryLabel, endLabel, catchLabel);
            }

            final boolean reachable = method.isReachable();
            if(reachable) {
                popScope();
                if(bodyCanThrow) {
                    method._goto(exitLabel);
                }
            }

            if(bodyCanThrow) {
                method._catch(catchLabel);
                popScopeException();
                method.athrow();
                if(reachable) {
                    method.label(exitLabel);
                }
            }
        }
        return false;
    }

    private void loadADD(final UnaryNode unaryNode, final TypeBounds resultBounds) {
        loadExpression(unaryNode.getExpression(), resultBounds.booleanToInt().notWiderThan(Type.NUMBER));
        if(method.peekType() == Type.BOOLEAN) {
            // It's a no-op in bytecode, but we must make sure it is treated as an int for purposes of type signatures
            method.convert(Type.INT);
        }
    }

    private void loadBIT_NOT(final UnaryNode unaryNode) {
        loadExpression(unaryNode.getExpression(), TypeBounds.INT).load(-1).xor();
    }

    private void loadDECINC(final UnaryNode unaryNode) {
        final Expression operand     = unaryNode.getExpression();
        final Type       type        = unaryNode.getType();
        final TypeBounds typeBounds  = new TypeBounds(type, Type.NUMBER);
        final TokenType  tokenType   = unaryNode.tokenType();
        final boolean    isPostfix   = tokenType == TokenType.DECPOSTFIX || tokenType == TokenType.INCPOSTFIX;
        final boolean    isIncrement = tokenType == TokenType.INCPREFIX || tokenType == TokenType.INCPOSTFIX;

        assert !type.isObject();

        new SelfModifyingStore<UnaryNode>(unaryNode, operand) {

            private void loadRhs() {
                loadExpression(operand, typeBounds, true);
            }

            @Override
            protected void evaluate() {
                if(isPostfix) {
                    loadRhs();
                } else {
                    new OptimisticOperation(unaryNode, typeBounds) {
                        @Override
                        void loadStack() {
                            loadRhs();
                            loadMinusOne();
                        }
                        @Override
                        void consumeStack() {
                            doDecInc(getProgramPoint());
                        }
                    }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(operand));
                }
            }

            @Override
            protected void storeNonDiscard() {
                super.storeNonDiscard();
                if (isPostfix) {
                    new OptimisticOperation(unaryNode, typeBounds) {
                        @Override
                        void loadStack() {
                            loadMinusOne();
                        }
                        @Override
                        void consumeStack() {
                            doDecInc(getProgramPoint());
                        }
                    }.emit(1); // 1 for non-incremented result on the top of the stack pushed in evaluate()
                }
            }

            private void loadMinusOne() {
                if (type.isInteger()) {
                    method.load(isIncrement ? 1 : -1);
                } else {
                    method.load(isIncrement ? 1.0 : -1.0);
                }
            }

            private void doDecInc(final int programPoint) {
                method.add(programPoint);
            }
        }.store();
    }

    private static int getOptimisticIgnoreCountForSelfModifyingExpression(final Expression target) {
        return target instanceof AccessNode ? 1 : target instanceof IndexNode ? 2 : 0;
    }

    private void loadAndDiscard(final Expression expr) {
        // TODO: move checks for discarding to actual expression load code (e.g. as we do with void). That way we might
        // be able to eliminate even more checks.
        if(expr instanceof PrimitiveLiteralNode | isLocalVariable(expr)) {
            assert !lc.isCurrentDiscard(expr);
            // Don't bother evaluating expressions without side effects. Typical usage is "void 0" for reliably generating
            // undefined.
            return;
        }

        lc.pushDiscard(expr);
        loadExpression(expr, TypeBounds.UNBOUNDED);
        if (lc.popDiscardIfCurrent(expr)) {
            assert !expr.isAssignment();
            // NOTE: if we had a way to load with type void, we could avoid popping
            method.pop();
        }
    }

    
Loads the expression with the specified type bounds, but if the parent expression is the current discard,
then instead loads and discards the expression.
Params:
parent – the parent expression that's tested for being the current discard
expr – the expression that's either normally loaded or discard-loaded
resultBounds – result bounds for when loading the expression normally/**
     * Loads the expression with the specified type bounds, but if the parent expression is the current discard,
     * then instead loads and discards the expression.
     * @param parent the parent expression that's tested for being the current discard
     * @param expr the expression that's either normally loaded or discard-loaded
     * @param resultBounds result bounds for when loading the expression normally
     */
    private void loadMaybeDiscard(final Expression parent, final Expression expr, final TypeBounds resultBounds) {
        loadMaybeDiscard(lc.popDiscardIfCurrent(parent), expr, resultBounds);
    }

    
Loads the expression with the specified type bounds, or loads and discards the expression, depending on the
value of the discard flag. Useful as a helper for expressions with control flow where you often can't combine
testing for being the current discard and loading the subexpressions.
Params:
discard – if true, the expression is loaded and discarded
expr – the expression that's either normally loaded or discard-loaded
resultBounds – result bounds for when loading the expression normally/**
     * Loads the expression with the specified type bounds, or loads and discards the expression, depending on the
     * value of the discard flag. Useful as a helper for expressions with control flow where you often can't combine
     * testing for being the current discard and loading the subexpressions.
     * @param discard if true, the expression is loaded and discarded
     * @param expr the expression that's either normally loaded or discard-loaded
     * @param resultBounds result bounds for when loading the expression normally
     */
    private void loadMaybeDiscard(final boolean discard, final Expression expr, final TypeBounds resultBounds) {
        if (discard) {
            loadAndDiscard(expr);
        } else {
            loadExpression(expr, resultBounds);
        }
    }

    private void loadNEW(final UnaryNode unaryNode) {
        final CallNode callNode = (CallNode)unaryNode.getExpression();
        final List<Expression> args   = callNode.getArgs();

        final Expression func = callNode.getFunction();
        // Load function reference.
        loadExpressionAsObject(func); // must detect type error

        method.dynamicNew(1 + loadArgs(args), getCallSiteFlags(), func.toString(false));
    }

    private void loadNOT(final UnaryNode unaryNode) {
        final Expression expr = unaryNode.getExpression();
        if(expr instanceof UnaryNode && expr.isTokenType(TokenType.NOT)) {
            // !!x is idiomatic boolean cast in JavaScript
            loadExpressionAsBoolean(((UnaryNode)expr).getExpression());
        } else {
            final Label trueLabel  = new Label("true");
            final Label afterLabel = new Label("after");

            emitBranch(expr, trueLabel, true);
            method.load(true);
            method._goto(afterLabel);
            method.label(trueLabel);
            method.load(false);
            method.label(afterLabel);
        }
    }

    private void loadSUB(final UnaryNode unaryNode, final TypeBounds resultBounds) {
        final Type type = unaryNode.getType();
        assert type.isNumeric();
        final TypeBounds numericBounds = resultBounds.booleanToInt();
        new OptimisticOperation(unaryNode, numericBounds) {
            @Override
            void loadStack() {
                final Expression expr = unaryNode.getExpression();
                loadExpression(expr, numericBounds.notWiderThan(Type.NUMBER));
            }
            @Override
            void consumeStack() {
                // Must do an explicit conversion to the operation's type when it's double so that we correctly handle
                // negation of an int 0 to a double -0. With this, we get the correct negation of a local variable after
                // it deoptimized, e.g. "iload_2; i2d; dneg". Without this, we get "iload_2; ineg; i2d".
                if(type.isNumber()) {
                    method.convert(type);
                }
                method.neg(getProgramPoint());
            }
        }.emit();
    }

    public void loadVOID(final UnaryNode unaryNode, final TypeBounds resultBounds) {
        loadAndDiscard(unaryNode.getExpression());
        if (!lc.popDiscardIfCurrent(unaryNode)) {
            method.loadUndefined(resultBounds.widest);
        }
    }

    public void loadADD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        new OptimisticOperation(binaryNode, resultBounds) {
            @Override
            void loadStack() {
                final TypeBounds operandBounds;
                final boolean isOptimistic = isValid(getProgramPoint());
                boolean forceConversionSeparation = false;
                if(isOptimistic) {
                    operandBounds = new TypeBounds(binaryNode.getType(), Type.OBJECT);
                } else {
                    // Non-optimistic, non-FP +. Allow it to overflow.
                    final Type widestOperationType = binaryNode.getWidestOperationType();
                    operandBounds = new TypeBounds(Type.narrowest(binaryNode.getWidestOperandType(), resultBounds.widest), widestOperationType);
                    forceConversionSeparation = widestOperationType.narrowerThan(resultBounds.widest);
                }
                loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), operandBounds, false, forceConversionSeparation);
            }

            @Override
            void consumeStack() {
                method.add(getProgramPoint());
            }
        }.emit();
    }

    private void loadAND_OR(final BinaryNode binaryNode, final TypeBounds resultBounds, final boolean isAnd) {
        final Type narrowestOperandType = Type.widestReturnType(binaryNode.lhs().getType(), binaryNode.rhs().getType());

        final boolean isCurrentDiscard = lc.popDiscardIfCurrent(binaryNode);

        final Label skip = new Label("skip");
        if(narrowestOperandType == Type.BOOLEAN) {
            // optimize all-boolean logical expressions
            final Label onTrue = new Label("andor_true");
            emitBranch(binaryNode, onTrue, true);
            if (isCurrentDiscard) {
                method.label(onTrue);
            } else {
                method.load(false);
                method._goto(skip);
                method.label(onTrue);
                method.load(true);
                method.label(skip);
            }
            return;
        }

        final TypeBounds outBounds = resultBounds.notNarrowerThan(narrowestOperandType);
        final JoinPredecessorExpression lhs = (JoinPredecessorExpression)binaryNode.lhs();
        final boolean lhsConvert = LocalVariableConversion.hasLiveConversion(lhs);
        final Label evalRhs = lhsConvert ? new Label("eval_rhs") : null;

        loadExpression(lhs, outBounds);
        if (!isCurrentDiscard) {
            method.dup();
        }
        method.convert(Type.BOOLEAN);
        if (isAnd) {
            if(lhsConvert) {
                method.ifne(evalRhs);
            } else {
                method.ifeq(skip);
            }
        } else if(lhsConvert) {
            method.ifeq(evalRhs);
        } else {
            method.ifne(skip);
        }

        if(lhsConvert) {
            method.beforeJoinPoint(lhs);
            method._goto(skip);
            method.label(evalRhs);
        }

        if (!isCurrentDiscard) {
            method.pop();
        }
        final JoinPredecessorExpression rhs = (JoinPredecessorExpression)binaryNode.rhs();
        loadMaybeDiscard(isCurrentDiscard, rhs, outBounds);
        method.beforeJoinPoint(rhs);
        method.label(skip);
    }

    private static boolean isLocalVariable(final Expression lhs) {
        return lhs instanceof IdentNode && isLocalVariable((IdentNode)lhs);
    }

    private static boolean isLocalVariable(final IdentNode lhs) {
        return lhs.getSymbol().isBytecodeLocal();
    }

    // NOTE: does not use resultBounds as the assignment is driven by the type of the RHS
    private void loadASSIGN(final BinaryNode binaryNode) {
        final Expression lhs = binaryNode.lhs();
        final Expression rhs = binaryNode.rhs();

        final Type rhsType = rhs.getType();
        // Detect dead assignments
        if(lhs instanceof IdentNode) {
            final Symbol symbol = ((IdentNode)lhs).getSymbol();
            if(!symbol.isScope() && !symbol.hasSlotFor(rhsType) && lc.popDiscardIfCurrent(binaryNode)) {
                loadAndDiscard(rhs);
                method.markDeadLocalVariable(symbol);
                return;
            }
        }

        new Store<BinaryNode>(binaryNode, lhs) {
            @Override
            protected void evaluate() {
                // NOTE: we're loading with "at least as wide as" so optimistic operations on the right hand side
                // remain optimistic, and then explicitly convert to the required type if needed.
                loadExpressionAsType(rhs, rhsType);
            }
        }.store();
    }

    
Binary self-assignment that can be optimistic: +=, -=, *=, and /=.
/**
     * Binary self-assignment that can be optimistic: +=, -=, *=, and /=.
     */
    private abstract class BinaryOptimisticSelfAssignment extends SelfModifyingStore<BinaryNode> {

        
Constructor
Params:
node – the assign op node/**
         * Constructor
         *
         * @param node the assign op node
         */
        BinaryOptimisticSelfAssignment(final BinaryNode node) {
            super(node, node.lhs());
        }

        protected abstract void op(OptimisticOperation oo);

        @Override
        protected void evaluate() {
            final Expression lhs = assignNode.lhs();
            final Expression rhs = assignNode.rhs();
            final Type widestOperationType = assignNode.getWidestOperationType();
            final TypeBounds bounds = new TypeBounds(assignNode.getType(), widestOperationType);
            new OptimisticOperation(assignNode, bounds) {
                @Override
                void loadStack() {
                    final boolean forceConversionSeparation;
                    if (isValid(getProgramPoint()) || widestOperationType == Type.NUMBER) {
                        forceConversionSeparation = false;
                    } else {
                        final Type operandType = Type.widest(booleanToInt(objectToNumber(lhs.getType())), booleanToInt(objectToNumber(rhs.getType())));
                        forceConversionSeparation = operandType.narrowerThan(widestOperationType);
                    }
                    loadBinaryOperands(lhs, rhs, bounds, true, forceConversionSeparation);
                }
                @Override
                void consumeStack() {
                    op(this);
                }
            }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(lhs));
            method.convert(assignNode.getType());
        }
    }

    
Non-optimistic binary self-assignment operation. Basically, everything except +=, -=, *=, and /=.
/**
     * Non-optimistic binary self-assignment operation. Basically, everything except +=, -=, *=, and /=.
     */
    private abstract class BinarySelfAssignment extends SelfModifyingStore<BinaryNode> {
        BinarySelfAssignment(final BinaryNode node) {
            super(node, node.lhs());
        }

        protected abstract void op();

        @Override
        protected void evaluate() {
            loadBinaryOperands(assignNode.lhs(), assignNode.rhs(), TypeBounds.UNBOUNDED.notWiderThan(assignNode.getWidestOperandType()), true, false);
            op();
        }
    }

    private void loadASSIGN_ADD(final BinaryNode binaryNode) {
        new BinaryOptimisticSelfAssignment(binaryNode) {
            @Override
            protected void op(final OptimisticOperation oo) {
                assert !(binaryNode.getType().isObject() && oo.isOptimistic);
                method.add(oo.getProgramPoint());
            }
        }.store();
    }

    private void loadASSIGN_BIT_AND(final BinaryNode binaryNode) {
        new BinarySelfAssignment(binaryNode) {
            @Override
            protected void op() {
                method.and();
            }
        }.store();
    }

    private void loadASSIGN_BIT_OR(final BinaryNode binaryNode) {
        new BinarySelfAssignment(binaryNode) {
            @Override
            protected void op() {
                method.or();
            }
        }.store();
    }

    private void loadASSIGN_BIT_XOR(final BinaryNode binaryNode) {
        new BinarySelfAssignment(binaryNode) {
            @Override
            protected void op() {
                method.xor();
            }
        }.store();
    }

    private void loadASSIGN_DIV(final BinaryNode binaryNode) {
        new BinaryOptimisticSelfAssignment(binaryNode) {
            @Override
            protected void op(final OptimisticOperation oo) {
                method.div(oo.getProgramPoint());
            }
        }.store();
    }

    private void loadASSIGN_MOD(final BinaryNode binaryNode) {
        new BinaryOptimisticSelfAssignment(binaryNode) {
            @Override
            protected void op(final OptimisticOperation oo) {
                method.rem(oo.getProgramPoint());
            }
        }.store();
    }

    private void loadASSIGN_MUL(final BinaryNode binaryNode) {
        new BinaryOptimisticSelfAssignment(binaryNode) {
            @Override
            protected void op(final OptimisticOperation oo) {
                method.mul(oo.getProgramPoint());
            }
        }.store();
    }

    private void loadASSIGN_SAR(final BinaryNode binaryNode) {
        new BinarySelfAssignment(binaryNode) {
            @Override
            protected void op() {
                method.sar();
            }
        }.store();
    }

    private void loadASSIGN_SHL(final BinaryNode binaryNode) {
        new BinarySelfAssignment(binaryNode) {
            @Override
            protected void op() {
                method.shl();
            }
        }.store();
    }

    private void loadASSIGN_SHR(final BinaryNode binaryNode) {
        new SelfModifyingStore<BinaryNode>(binaryNode, binaryNode.lhs()) {
            @Override
            protected void evaluate() {
                new OptimisticOperation(assignNode, new TypeBounds(Type.INT, Type.NUMBER)) {
                    @Override
                    void loadStack() {
                        assert assignNode.getWidestOperandType() == Type.INT;
                        if (isRhsZero(binaryNode)) {
                            loadExpression(binaryNode.lhs(), TypeBounds.INT, true);
                        } else {
                            loadBinaryOperands(binaryNode.lhs(), binaryNode.rhs(), TypeBounds.INT, true, false);
                            method.shr();
                        }
                    }

                    @Override
                    void consumeStack() {
                        if (isOptimistic(binaryNode)) {
                            toUint32Optimistic(binaryNode.getProgramPoint());
                        } else {
                            toUint32Double();
                        }
                    }
                }.emit(getOptimisticIgnoreCountForSelfModifyingExpression(binaryNode.lhs()));
                method.convert(assignNode.getType());
            }
        }.store();
    }

    private void doSHR(final BinaryNode binaryNode) {
        new OptimisticOperation(binaryNode, new TypeBounds(Type.INT, Type.NUMBER)) {
            @Override
            void loadStack() {
                if (isRhsZero(binaryNode)) {
                    loadExpressionAsType(binaryNode.lhs(), Type.INT);
                } else {
                    loadBinaryOperands(binaryNode);
                    method.shr();
                }
            }

            @Override
            void consumeStack() {
                if (isOptimistic(binaryNode)) {
                    toUint32Optimistic(binaryNode.getProgramPoint());
                } else {
                    toUint32Double();
                }
            }
        }.emit();

    }

    private void toUint32Optimistic(final int programPoint) {
        method.load(programPoint);
        JSType.TO_UINT32_OPTIMISTIC.invoke(method);
    }

    private void toUint32Double() {
        JSType.TO_UINT32_DOUBLE.invoke(method);
    }

    private void loadASSIGN_SUB(final BinaryNode binaryNode) {
        new BinaryOptimisticSelfAssignment(binaryNode) {
            @Override
            protected void op(final OptimisticOperation oo) {
                method.sub(oo.getProgramPoint());
            }
        }.store();
    }

    
Helper class for binary arithmetic ops
/**
     * Helper class for binary arithmetic ops
     */
    private abstract class BinaryArith {
        protected abstract void op(int programPoint);

        protected void evaluate(final BinaryNode node, final TypeBounds resultBounds) {
            final TypeBounds numericBounds = resultBounds.booleanToInt().objectToNumber();
            new OptimisticOperation(node, numericBounds) {
                @Override
                void loadStack() {
                    final TypeBounds operandBounds;
                    boolean forceConversionSeparation = false;
                    if(numericBounds.narrowest == Type.NUMBER) {
                        // Result should be double always. Propagate it into the operands so we don't have lots of I2D
                        // and L2D after operand evaluation.
                        assert numericBounds.widest == Type.NUMBER;
                        operandBounds = numericBounds;
                    } else {
                        final boolean isOptimistic = isValid(getProgramPoint());
                        if(isOptimistic || node.isTokenType(TokenType.DIV) || node.isTokenType(TokenType.MOD)) {
                            operandBounds = new TypeBounds(node.getType(), Type.NUMBER);
                        } else {
                            // Non-optimistic, non-FP subtraction or multiplication. Allow them to overflow.
                            operandBounds = new TypeBounds(Type.narrowest(node.getWidestOperandType(),
                                    numericBounds.widest), Type.NUMBER);
                            forceConversionSeparation = true;
                        }
                    }
                    loadBinaryOperands(node.lhs(), node.rhs(), operandBounds, false, forceConversionSeparation);
                }

                @Override
                void consumeStack() {
                    op(getProgramPoint());
                }
            }.emit();
        }
    }

    private void loadBIT_AND(final BinaryNode binaryNode) {
        loadBinaryOperands(binaryNode);
        method.and();
    }

    private void loadBIT_OR(final BinaryNode binaryNode) {
        // Optimize x|0 to (int)x
        if (isRhsZero(binaryNode)) {
            loadExpressionAsType(binaryNode.lhs(), Type.INT);
        } else {
            loadBinaryOperands(binaryNode);
            method.or();
        }
    }

    private static boolean isRhsZero(final BinaryNode binaryNode) {
        final Expression rhs = binaryNode.rhs();
        return rhs instanceof LiteralNode && INT_ZERO.equals(((LiteralNode<?>)rhs).getValue());
    }

    private void loadBIT_XOR(final BinaryNode binaryNode) {
        loadBinaryOperands(binaryNode);
        method.xor();
    }

    private void loadCOMMARIGHT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        loadAndDiscard(binaryNode.lhs());
        loadMaybeDiscard(binaryNode, binaryNode.rhs(), resultBounds);
    }

    private void loadCOMMALEFT(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        loadMaybeDiscard(binaryNode, binaryNode.lhs(), resultBounds);
        loadAndDiscard(binaryNode.rhs());
    }

    private void loadDIV(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        new BinaryArith() {
            @Override
            protected void op(final int programPoint) {
                method.div(programPoint);
            }
        }.evaluate(binaryNode, resultBounds);
    }

    private void loadCmp(final BinaryNode binaryNode, final Condition cond) {
        loadComparisonOperands(binaryNode);

        final Label trueLabel  = new Label("trueLabel");
        final Label afterLabel = new Label("skip");

        method.conditionalJump(cond, trueLabel);

        method.load(Boolean.FALSE);
        method._goto(afterLabel);
        method.label(trueLabel);
        method.load(Boolean.TRUE);
        method.label(afterLabel);
    }

    private void loadMOD(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        new BinaryArith() {
            @Override
            protected void op(final int programPoint) {
                method.rem(programPoint);
            }
        }.evaluate(binaryNode, resultBounds);
    }

    private void loadMUL(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        new BinaryArith() {
            @Override
            protected void op(final int programPoint) {
                method.mul(programPoint);
            }
        }.evaluate(binaryNode, resultBounds);
    }

    private void loadSAR(final BinaryNode binaryNode) {
        loadBinaryOperands(binaryNode);
        method.sar();
    }

    private void loadSHL(final BinaryNode binaryNode) {
        loadBinaryOperands(binaryNode);
        method.shl();
    }

    private void loadSHR(final BinaryNode binaryNode) {
        doSHR(binaryNode);
    }

    private void loadSUB(final BinaryNode binaryNode, final TypeBounds resultBounds) {
        new BinaryArith() {
            @Override
            protected void op(final int programPoint) {
                method.sub(programPoint);
            }
        }.evaluate(binaryNode, resultBounds);
    }

    @Override
    public boolean enterLabelNode(final LabelNode labelNode) {
        labeledBlockBreakLiveLocals.push(lc.getUsedSlotCount());
        return true;
    }

    @Override
    protected boolean enterDefault(final Node node) {
        throw new AssertionError("Code generator entered node of type " + node.getClass().getName());
    }

    private void loadTernaryNode(final TernaryNode ternaryNode, final TypeBounds resultBounds) {
        final Expression test = ternaryNode.getTest();
        final JoinPredecessorExpression trueExpr  = ternaryNode.getTrueExpression();
        final JoinPredecessorExpression falseExpr = ternaryNode.getFalseExpression();

        final Label falseLabel = new Label("ternary_false");
        final Label exitLabel  = new Label("ternary_exit");

        final Type outNarrowest = Type.narrowest(resultBounds.widest, Type.generic(Type.widestReturnType(trueExpr.getType(), falseExpr.getType())));
        final TypeBounds outBounds = resultBounds.notNarrowerThan(outNarrowest);

        emitBranch(test, falseLabel, false);

        final boolean isCurrentDiscard = lc.popDiscardIfCurrent(ternaryNode);
        loadMaybeDiscard(isCurrentDiscard, trueExpr.getExpression(), outBounds);
        assert isCurrentDiscard || Type.generic(method.peekType()) == outBounds.narrowest;
        method.beforeJoinPoint(trueExpr);
        method._goto(exitLabel);
        method.label(falseLabel);
        loadMaybeDiscard(isCurrentDiscard, falseExpr.getExpression(), outBounds);
        assert isCurrentDiscard || Type.generic(method.peekType()) == outBounds.narrowest;
        method.beforeJoinPoint(falseExpr);
        method.label(exitLabel);
    }

    
Generate all shared scope calls generated during codegen.
/**
     * Generate all shared scope calls generated during codegen.
     */
    void generateScopeCalls() {
        for (final SharedScopeCall scopeAccess : lc.getScopeCalls()) {
            scopeAccess.generateScopeCall();
        }
    }

    
Debug code used to print symbols
Params:
block – the block we are in
function – the function we are in
ident – identifier for block or function where applicable/**
     * Debug code used to print symbols
     *
     * @param block the block we are in
     * @param function the function we are in
     * @param ident identifier for block or function where applicable
     */
    private void printSymbols(final Block block, final FunctionNode function, final String ident) {
        if (compiler.getScriptEnvironment()._print_symbols || function.getDebugFlag(FunctionNode.DEBUG_PRINT_SYMBOLS)) {
            final PrintWriter out = compiler.getScriptEnvironment().getErr();
            out.println("[BLOCK in '" + ident + "']");
            if (!block.printSymbols(out)) {
                out.println("<no symbols>");
            }
            out.println();
        }
    }


    
The difference between a store and a self modifying store is that
the latter may load part of the target on the stack, e.g. the base
of an AccessNode or the base and index of an IndexNode. These are used
both as target and as an extra source. Previously it was problematic
for self modifying stores if the target/lhs didn't belong to one
of three trivial categories: IdentNode, AcessNodes, IndexNodes. In that
case it was evaluated and tagged as "resolved", which meant at the second
time the lhs of this store was read (e.g. in a = a (second) + b for a += b,
it would be evaluated to a nop in the scope and cause stack underflow
see NASHORN-703
Type parameters:
<T> – /**
     * The difference between a store and a self modifying store is that
     * the latter may load part of the target on the stack, e.g. the base
     * of an AccessNode or the base and index of an IndexNode. These are used
     * both as target and as an extra source. Previously it was problematic
     * for self modifying stores if the target/lhs didn't belong to one
     * of three trivial categories: IdentNode, AcessNodes, IndexNodes. In that
     * case it was evaluated and tagged as "resolved", which meant at the second
     * time the lhs of this store was read (e.g. in a = a (second) + b for a += b,
     * it would be evaluated to a nop in the scope and cause stack underflow
     *
     * see NASHORN-703
     *
     * @param <T>
     */
    private abstract class SelfModifyingStore<T extends Expression> extends Store<T> {
        protected SelfModifyingStore(final T assignNode, final Expression target) {
            super(assignNode, target);
        }

        @Override
        protected boolean isSelfModifying() {
            return true;
        }
    }

    
Helper class to generate stores
/**
     * Helper class to generate stores
     */
    private abstract class Store<T extends Expression> {

        
An assignment node, e.g. x += y /** An assignment node, e.g. x += y */
        protected final T assignNode;

        
The target node to store to, e.g. x /** The target node to store to, e.g. x */
        private final Expression target;

        
How deep on the stack do the arguments go if this generates an indy call /** How deep on the stack do the arguments go if this generates an indy call */
        private int depth;

        
If we have too many arguments, we need temporary storage, this is stored in 'quick' /** If we have too many arguments, we need temporary storage, this is stored in 'quick' */
        private IdentNode quick;

        
Constructor
Params:
assignNode – the node representing the whole assignment
target –     the target node of the assignment (destination)/**
         * Constructor
         *
         * @param assignNode the node representing the whole assignment
         * @param target     the target node of the assignment (destination)
         */
        protected Store(final T assignNode, final Expression target) {
            this.assignNode = assignNode;
            this.target = target;
        }

        
Constructor
Params:
assignNode – the node representing the whole assignment/**
         * Constructor
         *
         * @param assignNode the node representing the whole assignment
         */
        protected Store(final T assignNode) {
            this(assignNode, assignNode);
        }

        
Is this a self modifying store operation, e.g. *= or ++
Returns:
true if self modifying store/**
         * Is this a self modifying store operation, e.g. *= or ++
         * @return true if self modifying store
         */
        protected boolean isSelfModifying() {
            return false;
        }

        private void prologue() {
            /*
             * This loads the parts of the target, e.g base and index. they are kept
             * on the stack throughout the store and used at the end to execute it
             */

            target.accept(new SimpleNodeVisitor() {
                @Override
                public boolean enterIdentNode(final IdentNode node) {
                    if (node.getSymbol().isScope()) {
                        method.loadCompilerConstant(SCOPE);
                        depth += Type.SCOPE.getSlots();
                        assert depth == 1;
                    }
                    return false;
                }

                private void enterBaseNode() {
                    assert target instanceof BaseNode : "error - base node " + target + " must be instanceof BaseNode";
                    final BaseNode   baseNode = (BaseNode)target;
                    final Expression base     = baseNode.getBase();

                    loadExpressionAsObject(base);
                    depth += Type.OBJECT.getSlots();
                    assert depth == 1;

                    if (isSelfModifying()) {
                        method.dup();
                    }
                }

                @Override
                public boolean enterAccessNode(final AccessNode node) {
                    enterBaseNode();
                    return false;
                }

                @Override
                public boolean enterIndexNode(final IndexNode node) {
                    enterBaseNode();

                    final Expression index = node.getIndex();
                    if (!index.getType().isNumeric()) {
                        // could be boolean here as well
                        loadExpressionAsObject(index);
                    } else {
                        loadExpressionUnbounded(index);
                    }
                    depth += index.getType().getSlots();

                    if (isSelfModifying()) {
                        //convert "base base index" to "base index base index"
                        method.dup(1);
                    }

                    return false;
                }

            });
        }

        
Generates an extra local variable, always using the same slot, one that is available after the end of the
frame.
Params:
type – the type of the variable
Returns:
the quick variable/**
         * Generates an extra local variable, always using the same slot, one that is available after the end of the
         * frame.
         *
         * @param type the type of the variable
         *
         * @return the quick variable
         */
        private IdentNode quickLocalVariable(final Type type) {
            final String name = lc.getCurrentFunction().uniqueName(QUICK_PREFIX.symbolName());
            final Symbol symbol = new Symbol(name, IS_INTERNAL | HAS_SLOT);
            symbol.setHasSlotFor(type);
            symbol.setFirstSlot(lc.quickSlot(type));

            final IdentNode quickIdent = IdentNode.createInternalIdentifier(symbol).setType(type);

            return quickIdent;
        }

        // store the result that "lives on" after the op, e.g. "i" in i++ postfix.
        protected void storeNonDiscard() {
            if (lc.popDiscardIfCurrent(assignNode)) {
                assert assignNode.isAssignment();
                return;
            }

            if (method.dup(depth) == null) {
                method.dup();
                final Type quickType = method.peekType();
                this.quick = quickLocalVariable(quickType);
                final Symbol quickSymbol = quick.getSymbol();
                method.storeTemp(quickType, quickSymbol.getFirstSlot());
            }
        }

        private void epilogue() {
            /**
             * Take the original target args from the stack and use them
             * together with the value to be stored to emit the store code
             *
             * The case that targetSymbol is in scope (!hasSlot) and we actually
             * need to do a conversion on non-equivalent types exists, but is
             * very rare. See for example test/script/basic/access-specializer.js
             */
            target.accept(new SimpleNodeVisitor() {
                @Override
                protected boolean enterDefault(final Node node) {
                    throw new AssertionError("Unexpected node " + node + " in store epilogue");
                }

                @Override
                public boolean enterIdentNode(final IdentNode node) {
                    final Symbol symbol = node.getSymbol();
                    assert symbol != null;
                    if (symbol.isScope()) {
                        final int flags = getScopeCallSiteFlags(symbol) | (node.isDeclaredHere() ? CALLSITE_DECLARE : 0);
                        if (isFastScope(symbol)) {
                            storeFastScopeVar(symbol, flags);
                        } else {
                            method.dynamicSet(node.getName(), flags, false);
                        }
                    } else {
                        final Type storeType = assignNode.getType();
                        assert storeType != Type.LONG;
                        if (symbol.hasSlotFor(storeType)) {
                            // Only emit a convert for a store known to be live; converts for dead stores can
                            // give us an unnecessary ClassCastException.
                            method.convert(storeType);
                        }
                        storeIdentWithCatchConversion(node, storeType);
                    }
                    return false;

                }

                @Override
                public boolean enterAccessNode(final AccessNode node) {
                    method.dynamicSet(node.getProperty(), getCallSiteFlags(), node.isIndex());
                    return false;
                }

                @Override
                public boolean enterIndexNode(final IndexNode node) {
                    method.dynamicSetIndex(getCallSiteFlags());
                    return false;
                }
            });


            // whatever is on the stack now is the final answer
        }

        protected abstract void evaluate();

        void store() {
            if (target instanceof IdentNode) {
                checkTemporalDeadZone((IdentNode)target);
            }
            prologue();
            evaluate(); // leaves an operation of whatever the operationType was on the stack
            storeNonDiscard();
            epilogue();
            if (quick != null) {
                method.load(quick);
            }
        }
    }

    private void newFunctionObject(final FunctionNode functionNode, final boolean addInitializer) {
        assert lc.peek() == functionNode;

        final RecompilableScriptFunctionData data = compiler.getScriptFunctionData(functionNode.getId());

        if (functionNode.isProgram() && !compiler.isOnDemandCompilation()) {
            final MethodEmitter createFunction = functionNode.getCompileUnit().getClassEmitter().method(
                    EnumSet.of(Flag.PUBLIC, Flag.STATIC), CREATE_PROGRAM_FUNCTION.symbolName(),
                    ScriptFunction.class, ScriptObject.class);
            createFunction.begin();
            loadConstantsAndIndex(data, createFunction);
            createFunction.load(SCOPE_TYPE, 0);
            createFunction.invoke(CREATE_FUNCTION_OBJECT);
            createFunction._return();
            createFunction.end();
        }

        if (addInitializer && !compiler.isOnDemandCompilation()) {
            functionNode.getCompileUnit().addFunctionInitializer(data, functionNode);
        }

        // We don't emit a ScriptFunction on stack for the outermost compiled function (as there's no code being
        // generated in its outer context that'd need it as a callee).
        if (lc.getOutermostFunction() == functionNode) {
            return;
        }

        loadConstantsAndIndex(data, method);

        if (functionNode.needsParentScope()) {
            method.loadCompilerConstant(SCOPE);
            method.invoke(CREATE_FUNCTION_OBJECT);
        } else {
            method.invoke(CREATE_FUNCTION_OBJECT_NO_SCOPE);
        }
    }

    // calls on Global class.
    private MethodEmitter globalInstance() {
        return method.invokestatic(GLOBAL_OBJECT, "instance", "()L" + GLOBAL_OBJECT + ';');
    }

    private MethodEmitter globalAllocateArguments() {
        return method.invokestatic(GLOBAL_OBJECT, "allocateArguments", methodDescriptor(ScriptObject.class, Object[].class, Object.class, int.class));
    }

    private MethodEmitter globalNewRegExp() {
        return method.invokestatic(GLOBAL_OBJECT, "newRegExp", methodDescriptor(Object.class, String.class, String.class));
    }

    private MethodEmitter globalRegExpCopy() {
        return method.invokestatic(GLOBAL_OBJECT, "regExpCopy", methodDescriptor(Object.class, Object.class));
    }

    private MethodEmitter globalAllocateArray(final ArrayType type) {
        //make sure the native array is treated as an array type
        return method.invokestatic(GLOBAL_OBJECT, "allocate", "(" + type.getDescriptor() + ")Ljdk/nashorn/internal/objects/NativeArray;");
    }

    private MethodEmitter globalIsEval() {
        return method.invokestatic(GLOBAL_OBJECT, "isEval", methodDescriptor(boolean.class, Object.class));
    }

    private MethodEmitter globalReplaceLocationPropertyPlaceholder() {
        return method.invokestatic(GLOBAL_OBJECT, "replaceLocationPropertyPlaceholder", methodDescriptor(Object.class, Object.class, Object.class));
    }

    private MethodEmitter globalCheckObjectCoercible() {
        return method.invokestatic(GLOBAL_OBJECT, "checkObjectCoercible", methodDescriptor(void.class, Object.class));
    }

    private MethodEmitter globalDirectEval() {
        return method.invokestatic(GLOBAL_OBJECT, "directEval",
                methodDescriptor(Object.class, Object.class, Object.class, Object.class, Object.class, boolean.class));
    }

    private abstract class OptimisticOperation {
        private final boolean isOptimistic;
        // expression and optimistic are the same reference
        private final Expression expression;
        private final Optimistic optimistic;
        private final TypeBounds resultBounds;

        OptimisticOperation(final Optimistic optimistic, final TypeBounds resultBounds) {
            this.optimistic = optimistic;
            this.expression = (Expression)optimistic;
            this.resultBounds = resultBounds;
            this.isOptimistic = isOptimistic(optimistic) && useOptimisticTypes() &&
                    // Operation is only effectively optimistic if its type, after being coerced into the result bounds
                    // is narrower than the upper bound.
                    resultBounds.within(Type.generic(((Expression)optimistic).getType())).narrowerThan(resultBounds.widest);
        }

        MethodEmitter emit() {
            return emit(0);
        }

        MethodEmitter emit(final int ignoredArgCount) {
            final int     programPoint                  = optimistic.getProgramPoint();
            final boolean optimisticOrContinuation      = isOptimistic || isContinuationEntryPoint(programPoint);
            final boolean currentContinuationEntryPoint = isCurrentContinuationEntryPoint(programPoint);
            final int     stackSizeOnEntry              = method.getStackSize() - ignoredArgCount;

            // First store the values on the stack opportunistically into local variables. Doing it before loadStack()
            // allows us to not have to pop/load any arguments that are pushed onto it by loadStack() in the second
            // storeStack().
            storeStack(ignoredArgCount, optimisticOrContinuation);

            // Now, load the stack
            loadStack();

            // Now store the values on the stack ultimately into local variables. In vast majority of cases, this is
            // (aside from creating the local types map) a no-op, as the first opportunistic stack store will already
            // store all variables. However, there can be operations in the loadStack() that invalidate some of the
            // stack stores, e.g. in "x[i] = x[++i]", "++i" will invalidate the already stored value for "i". In such
            // unfortunate cases this second storeStack() will restore the invariant that everything on the stack is
            // stored into a local variable, although at the cost of doing a store/load on the loaded arguments as well.
            final int liveLocalsCount = storeStack(method.getStackSize() - stackSizeOnEntry, optimisticOrContinuation);
            assert optimisticOrContinuation == (liveLocalsCount != -1);

            final Label beginTry;
            final Label catchLabel;
            final Label afterConsumeStack = isOptimistic || currentContinuationEntryPoint ? new Label("after_consume_stack") : null;
            if(isOptimistic) {
                beginTry = new Label("try_optimistic");
                final String catchLabelName = (afterConsumeStack == null ? "" : afterConsumeStack.toString()) + "_handler";
                catchLabel = new Label(catchLabelName);
                method.label(beginTry);
            } else {
                beginTry = catchLabel = null;
            }

            consumeStack();

            if(isOptimistic) {
                method._try(beginTry, afterConsumeStack, catchLabel, UnwarrantedOptimismException.class);
            }

            if(isOptimistic || currentContinuationEntryPoint) {
                method.label(afterConsumeStack);

                final int[] localLoads = method.getLocalLoadsOnStack(0, stackSizeOnEntry);
                assert everyStackValueIsLocalLoad(localLoads) : Arrays.toString(localLoads) + ", " + stackSizeOnEntry + ", " + ignoredArgCount;
                final List<Type> localTypesList = method.getLocalVariableTypes();
                final int usedLocals = method.getUsedSlotsWithLiveTemporaries();
                final List<Type> localTypes = method.getWidestLiveLocals(localTypesList.subList(0, usedLocals));
                assert everyLocalLoadIsValid(localLoads, usedLocals) : Arrays.toString(localLoads) + " ~ " + localTypes;

                if(isOptimistic) {
                    addUnwarrantedOptimismHandlerLabel(localTypes, catchLabel);
                }
                if(currentContinuationEntryPoint) {
                    final ContinuationInfo ci = getContinuationInfo();
                    assert ci != null : "no continuation info found for " + lc.getCurrentFunction();
                    assert !ci.hasTargetLabel(); // No duplicate program points
                    ci.setTargetLabel(afterConsumeStack);
                    ci.getHandlerLabel().markAsOptimisticContinuationHandlerFor(afterConsumeStack);
                    // Can't rely on targetLabel.stack.localVariableTypes.length, as it can be higher due to effectively
                    // dead local variables.
                    ci.lvarCount = localTypes.size();
                    ci.setStackStoreSpec(localLoads);
                    ci.setStackTypes(Arrays.copyOf(method.getTypesFromStack(method.getStackSize()), stackSizeOnEntry));
                    assert ci.getStackStoreSpec().length == ci.getStackTypes().length;
                    ci.setReturnValueType(method.peekType());
                    ci.lineNumber = getLastLineNumber();
                    ci.catchLabel = catchLabels.peek();
                }
            }
            return method;
        }

        
Stores the current contents of the stack into local variables so they are not lost before invoking something that can result in an UnwarantedOptimizationException. 
Params:
ignoreArgCount – the number of topmost arguments on stack to ignore when deciding on the shape of the catch block. Those are used in the situations when we could not place the call to storeStack early enough (before emitting code for pushing the arguments that the optimistic call will pop). This is admittedly a deficiency in the design of the code generator when it deals with self-assignments and we should probably look into fixing it.
optimisticOrContinuation – if false, this method should not execute a label for a catch block for the UnwarantedOptimizationException, suitable for capturing the currently live local variables, tailored to their types.
Returns:
types of the significant local variables after the stack was stored (types for local variables used
for temporary storage of ignored arguments are not returned)./**
         * Stores the current contents of the stack into local variables so they are not lost before invoking something that
         * can result in an {@code UnwarantedOptimizationException}.
         * @param ignoreArgCount the number of topmost arguments on stack to ignore when deciding on the shape of the catch
         * block. Those are used in the situations when we could not place the call to {@code storeStack} early enough
         * (before emitting code for pushing the arguments that the optimistic call will pop). This is admittedly a
         * deficiency in the design of the code generator when it deals with self-assignments and we should probably look
         * into fixing it.
         * @return types of the significant local variables after the stack was stored (types for local variables used
         * for temporary storage of ignored arguments are not returned).
         * @param optimisticOrContinuation if false, this method should not execute
         * a label for a catch block for the {@code UnwarantedOptimizationException}, suitable for capturing the
         * currently live local variables, tailored to their types.
         */
        private int storeStack(final int ignoreArgCount, final boolean optimisticOrContinuation) {
            if(!optimisticOrContinuation) {
                return -1; // NOTE: correct value to return is lc.getUsedSlotCount(), but it wouldn't be used anyway
            }

            final int stackSize = method.getStackSize();
            final Type[] stackTypes = method.getTypesFromStack(stackSize);
            final int[] localLoadsOnStack = method.getLocalLoadsOnStack(0, stackSize);
            final int usedSlots = method.getUsedSlotsWithLiveTemporaries();

            final int firstIgnored = stackSize - ignoreArgCount;
            // Find the first value on the stack (from the bottom) that is not a load from a local variable.
            int firstNonLoad = 0;
            while(firstNonLoad < firstIgnored && localLoadsOnStack[firstNonLoad] != Label.Stack.NON_LOAD) {
                firstNonLoad++;
            }

            // Only do the store/load if first non-load is not an ignored argument. Otherwise, do nothing and return
            // the number of used slots as the number of live local variables.
            if(firstNonLoad >= firstIgnored) {
                return usedSlots;
            }

            // Find the number of new temporary local variables that we need; it's the number of values on the stack that
            // are not direct loads of existing local variables.
            int tempSlotsNeeded = 0;
            for(int i = firstNonLoad; i < stackSize; ++i) {
                if(localLoadsOnStack[i] == Label.Stack.NON_LOAD) {
                    tempSlotsNeeded += stackTypes[i].getSlots();
                }
            }

            // Ensure all values on the stack that weren't directly loaded from a local variable are stored in a local
            // variable. We're starting from highest local variable index, so that in case ignoreArgCount > 0 the ignored
            // ones end up at the end of the local variable table.
            int lastTempSlot = usedSlots + tempSlotsNeeded;
            int ignoreSlotCount = 0;
            for(int i = stackSize; i -- > firstNonLoad;) {
                final int loadSlot = localLoadsOnStack[i];
                if(loadSlot == Label.Stack.NON_LOAD) {
                    final Type type = stackTypes[i];
                    final int slots = type.getSlots();
                    lastTempSlot -= slots;
                    if(i >= firstIgnored) {
                        ignoreSlotCount += slots;
                    }
                    method.storeTemp(type, lastTempSlot);
                } else {
                    method.pop();
                }
            }
            assert lastTempSlot == usedSlots; // used all temporary locals

            final List<Type> localTypesList = method.getLocalVariableTypes();

            // Load values back on stack.
            for(int i = firstNonLoad; i < stackSize; ++i) {
                final int loadSlot = localLoadsOnStack[i];
                final Type stackType = stackTypes[i];
                final boolean isLoad = loadSlot != Label.Stack.NON_LOAD;
                final int lvarSlot = isLoad ? loadSlot : lastTempSlot;
                final Type lvarType = localTypesList.get(lvarSlot);
                method.load(lvarType, lvarSlot);
                if(isLoad) {
                    // Conversion operators (I2L etc.) preserve "load"-ness of the value despite the fact that, in the
                    // strict sense they are creating a derived value from the loaded value. This special behavior of
                    // on-stack conversion operators is necessary to accommodate for differences in local variable types
                    // after deoptimization; having a conversion operator throw away "load"-ness would create different
                    // local variable table shapes between optimism-failed code and its deoptimized rest-of method).
                    // After we load the value back, we need to redo the conversion to the stack type if stack type is
                    // different.
                    // NOTE: this would only strictly be necessary for widening conversions (I2L, L2D, I2D), and not for
                    // narrowing ones (L2I, D2L, D2I) as only widening conversions are the ones that can get eliminated
                    // in a deoptimized method, as their original input argument got widened. Maybe experiment with
                    // throwing away "load"-ness for narrowing conversions in MethodEmitter.convert()?
                    method.convert(stackType);
                } else {
                    // temporary stores never needs a convert, as their type is always the same as the stack type.
                    assert lvarType == stackType;
                    lastTempSlot += lvarType.getSlots();
                }
            }
            // used all temporaries
            assert lastTempSlot == usedSlots + tempSlotsNeeded;

            return lastTempSlot - ignoreSlotCount;
        }

        private void addUnwarrantedOptimismHandlerLabel(final List<Type> localTypes, final Label label) {
            final String lvarTypesDescriptor = getLvarTypesDescriptor(localTypes);
            final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.getUnwarrantedOptimismHandlers();
            Collection<Label> labels = unwarrantedOptimismHandlers.get(lvarTypesDescriptor);
            if(labels == null) {
                labels = new LinkedList<>();
                unwarrantedOptimismHandlers.put(lvarTypesDescriptor, labels);
            }
            method.markLabelAsOptimisticCatchHandler(label, localTypes.size());
            labels.add(label);
        }

        abstract void loadStack();

        // Make sure that whatever indy call site you emit from this method uses {@code getCallSiteFlagsOptimistic(node)}
        // or otherwise ensure optimistic flag is correctly set in the call site, otherwise it doesn't make much sense
        // to use OptimisticExpression for emitting it.
        abstract void consumeStack();

        
Emits the correct dynamic getter code. Normally just delegates to method emitter, except when the target
expression is optimistic, and the desired type is narrower than the optimistic type. In that case, it'll emit a
dynamic getter with its original optimistic type, and explicitly insert a narrowing conversion. This way we can
preserve the optimism of the values even if they're subsequently immediately coerced into a narrower type. This
is beneficial because in this case we can still presume that since the original getter was optimistic, the
conversion has no side effects.
Params:
name – the name of the property being get
flags – call site flags
isMethod – whether we're preferably retrieving a function
Returns:
the current method emitter/**
         * Emits the correct dynamic getter code. Normally just delegates to method emitter, except when the target
         * expression is optimistic, and the desired type is narrower than the optimistic type. In that case, it'll emit a
         * dynamic getter with its original optimistic type, and explicitly insert a narrowing conversion. This way we can
         * preserve the optimism of the values even if they're subsequently immediately coerced into a narrower type. This
         * is beneficial because in this case we can still presume that since the original getter was optimistic, the
         * conversion has no side effects.
         * @param name the name of the property being get
         * @param flags call site flags
         * @param isMethod whether we're preferably retrieving a function
         * @return the current method emitter
         */
        MethodEmitter dynamicGet(final String name, final int flags, final boolean isMethod, final boolean isIndex) {
            if(isOptimistic) {
                return method.dynamicGet(getOptimisticCoercedType(), name, getOptimisticFlags(flags), isMethod, isIndex);
            }
            return method.dynamicGet(resultBounds.within(expression.getType()), name, nonOptimisticFlags(flags), isMethod, isIndex);
        }

        MethodEmitter dynamicGetIndex(final int flags, final boolean isMethod) {
            if(isOptimistic) {
                return method.dynamicGetIndex(getOptimisticCoercedType(), getOptimisticFlags(flags), isMethod);
            }
            return method.dynamicGetIndex(resultBounds.within(expression.getType()), nonOptimisticFlags(flags), isMethod);
        }

        MethodEmitter dynamicCall(final int argCount, final int flags, final String msg) {
            if (isOptimistic) {
                return method.dynamicCall(getOptimisticCoercedType(), argCount, getOptimisticFlags(flags), msg);
            }
            return method.dynamicCall(resultBounds.within(expression.getType()), argCount, nonOptimisticFlags(flags), msg);
        }

        int getOptimisticFlags(final int flags) {
            return flags | CALLSITE_OPTIMISTIC | (optimistic.getProgramPoint() << CALLSITE_PROGRAM_POINT_SHIFT); //encode program point in high bits
        }

        int getProgramPoint() {
            return isOptimistic ? optimistic.getProgramPoint() : INVALID_PROGRAM_POINT;
        }

        void convertOptimisticReturnValue() {
            if (isOptimistic) {
                final Type optimisticType = getOptimisticCoercedType();
                if(!optimisticType.isObject()) {
                    method.load(optimistic.getProgramPoint());
                    if(optimisticType.isInteger()) {
                        method.invoke(ENSURE_INT);
                    } else if(optimisticType.isNumber()) {
                        method.invoke(ENSURE_NUMBER);
                    } else {
                        throw new AssertionError(optimisticType);
                    }
                }
            }
        }

        void replaceCompileTimeProperty() {
            final IdentNode identNode = (IdentNode)expression;
            final String name = identNode.getSymbol().getName();
            if (CompilerConstants.__FILE__.name().equals(name)) {
                replaceCompileTimeProperty(getCurrentSource().getName());
            } else if (CompilerConstants.__DIR__.name().equals(name)) {
                replaceCompileTimeProperty(getCurrentSource().getBase());
            } else if (CompilerConstants.__LINE__.name().equals(name)) {
                replaceCompileTimeProperty(getCurrentSource().getLine(identNode.position()));
            }
        }

        
When an ident with name __FILE__, __DIR__, or __LINE__ is loaded, we'll try to look it up as any other
identifier. However, if it gets all the way up to the Global object, it will send back a special value that
represents a placeholder for these compile-time location properties. This method will generate code that loads
the value of the compile-time location property and then invokes a method in Global that will replace the
placeholder with the value. Effectively, if the symbol for these properties is defined anywhere in the lexical
scope, they take precedence, but if they aren't, then they resolve to the compile-time location property.
Params:
propertyValue – the actual value of the property/**
         * When an ident with name __FILE__, __DIR__, or __LINE__ is loaded, we'll try to look it up as any other
         * identifier. However, if it gets all the way up to the Global object, it will send back a special value that
         * represents a placeholder for these compile-time location properties. This method will generate code that loads
         * the value of the compile-time location property and then invokes a method in Global that will replace the
         * placeholder with the value. Effectively, if the symbol for these properties is defined anywhere in the lexical
         * scope, they take precedence, but if they aren't, then they resolve to the compile-time location property.
         * @param propertyValue the actual value of the property
         */
        private void replaceCompileTimeProperty(final Object propertyValue) {
            assert method.peekType().isObject();
            if(propertyValue instanceof String || propertyValue == null) {
                method.load((String)propertyValue);
            } else if(propertyValue instanceof Integer) {
                method.load(((Integer)propertyValue));
                method.convert(Type.OBJECT);
            } else {
                throw new AssertionError();
            }
            globalReplaceLocationPropertyPlaceholder();
            convertOptimisticReturnValue();
        }

        
Returns the type that should be used as the return type of the dynamic invocation that is emitted as the code
for the current optimistic operation. If the type bounds is exact boolean or narrower than the expression's
optimistic type, then the optimistic type is returned, otherwise the coercing type. Effectively, this method
allows for moving the coercion into the optimistic type when it won't adversely affect the optimistic
evaluation semantics, and for preserving the optimistic type and doing a separate coercion when it would
affect it.
Returns:
/**
         * Returns the type that should be used as the return type of the dynamic invocation that is emitted as the code
         * for the current optimistic operation. If the type bounds is exact boolean or narrower than the expression's
         * optimistic type, then the optimistic type is returned, otherwise the coercing type. Effectively, this method
         * allows for moving the coercion into the optimistic type when it won't adversely affect the optimistic
         * evaluation semantics, and for preserving the optimistic type and doing a separate coercion when it would
         * affect it.
         * @return
         */
        private Type getOptimisticCoercedType() {
            final Type optimisticType = expression.getType();
            assert resultBounds.widest.widerThan(optimisticType);
            final Type narrowest = resultBounds.narrowest;

            if(narrowest.isBoolean() || narrowest.narrowerThan(optimisticType)) {
                assert !optimisticType.isObject();
                return optimisticType;
            }
            assert !narrowest.isObject();
            return narrowest;
        }
    }

    private static boolean isOptimistic(final Optimistic optimistic) {
        if(!optimistic.canBeOptimistic()) {
            return false;
        }
        final Expression expr = (Expression)optimistic;
        return expr.getType().narrowerThan(expr.getWidestOperationType());
    }

    private static boolean everyLocalLoadIsValid(final int[] loads, final int localCount) {
        for (final int load : loads) {
            if(load < 0 || load >= localCount) {
                return false;
            }
        }
        return true;
    }

    private static boolean everyStackValueIsLocalLoad(final int[] loads) {
        for (final int load : loads) {
            if(load == Label.Stack.NON_LOAD) {
                return false;
            }
        }
        return true;
    }

    private String getLvarTypesDescriptor(final List<Type> localVarTypes) {
        final int count = localVarTypes.size();
        final StringBuilder desc = new StringBuilder(count);
        for(int i = 0; i < count;) {
            i += appendType(desc, localVarTypes.get(i));
        }
        return method.markSymbolBoundariesInLvarTypesDescriptor(desc.toString());
    }

    private static int appendType(final StringBuilder b, final Type t) {
        b.append(t.getBytecodeStackType());
        return t.getSlots();
    }

    private static int countSymbolsInLvarTypeDescriptor(final String lvarTypeDescriptor) {
        int count = 0;
        for(int i = 0; i < lvarTypeDescriptor.length(); ++i) {
            if(Character.isUpperCase(lvarTypeDescriptor.charAt(i))) {
                ++count;
            }
        }
        return count;

    }
    
Generates all the required UnwarrantedOptimismException handlers for the current function. The employed strategy strives to maximize code reuse. Every handler constructs an array to hold the local variables, then fills in some trailing part of the local variables (those for which it has a unique suffix in the descriptor), then jumps to a handler for a prefix that's shared with other handlers. A handler that fills up locals up to position 0 will not jump to a prefix handler (as it has no prefix), but instead end with constructing and throwing a RewriteException. Since we lexicographically sort the entries, we only need to check every entry to its immediately preceding one for longest matching prefix. 
Returns:
true if there is at least one exception handler/**
     * Generates all the required {@code UnwarrantedOptimismException} handlers for the current function. The employed
     * strategy strives to maximize code reuse. Every handler constructs an array to hold the local variables, then
     * fills in some trailing part of the local variables (those for which it has a unique suffix in the descriptor),
     * then jumps to a handler for a prefix that's shared with other handlers. A handler that fills up locals up to
     * position 0 will not jump to a prefix handler (as it has no prefix), but instead end with constructing and
     * throwing a {@code RewriteException}. Since we lexicographically sort the entries, we only need to check every
     * entry to its immediately preceding one for longest matching prefix.
     * @return true if there is at least one exception handler
     */
    private boolean generateUnwarrantedOptimismExceptionHandlers(final FunctionNode fn) {
        if(!useOptimisticTypes()) {
            return false;
        }

        // Take the mapping of lvarSpecs -> labels, and turn them into a descending lexicographically sorted list of
        // handler specifications.
        final Map<String, Collection<Label>> unwarrantedOptimismHandlers = lc.popUnwarrantedOptimismHandlers();
        if(unwarrantedOptimismHandlers.isEmpty()) {
            return false;
        }

        method.lineNumber(0);

        final List<OptimismExceptionHandlerSpec> handlerSpecs = new ArrayList<>(unwarrantedOptimismHandlers.size() * 4/3);
        for(final String spec: unwarrantedOptimismHandlers.keySet()) {
            handlerSpecs.add(new OptimismExceptionHandlerSpec(spec, true));
        }
        Collections.sort(handlerSpecs, Collections.reverseOrder());

        // Map of local variable specifications to labels for populating the array for that local variable spec.
        final Map<String, Label> delegationLabels = new HashMap<>();

        // Do everything in a single pass over the handlerSpecs list. Note that the list can actually grow as we're
        // passing through it as we might add new prefix handlers into it, so can't hoist size() outside of the loop.
        for(int handlerIndex = 0; handlerIndex < handlerSpecs.size(); ++handlerIndex) {
            final OptimismExceptionHandlerSpec spec = handlerSpecs.get(handlerIndex);
            final String lvarSpec = spec.lvarSpec;
            if(spec.catchTarget) {
                assert !method.isReachable();
                // Start a catch block and assign the labels for this lvarSpec with it.
                method._catch(unwarrantedOptimismHandlers.get(lvarSpec));
                // This spec is a catch target, so emit array creation code. The length of the array is the number of
                // symbols - the number of uppercase characters.
                method.load(countSymbolsInLvarTypeDescriptor(lvarSpec));
                method.newarray(Type.OBJECT_ARRAY);
            }
            if(spec.delegationTarget) {
                // If another handler can delegate to this handler as its prefix, then put a jump target here for the
                // shared code (after the array creation code, which is never shared).
                method.label(delegationLabels.get(lvarSpec)); // label must exist
            }

            final boolean lastHandler = handlerIndex == handlerSpecs.size() - 1;

            int lvarIndex;
            final int firstArrayIndex;
            final int firstLvarIndex;
            Label delegationLabel;
            final String commonLvarSpec;
            if(lastHandler) {
                // Last handler block, doesn't delegate to anything.
                lvarIndex = 0;
                firstLvarIndex = 0;
                firstArrayIndex = 0;
                delegationLabel = null;
                commonLvarSpec = null;
            } else {
                // Not yet the last handler block, will definitely delegate to another handler; let's figure out which
                // one. It can be an already declared handler further down the list, or it might need to declare a new
                // prefix handler.

                // Since we're lexicographically ordered, the common prefix handler is defined by the common prefix of
                // this handler and the next handler on the list.
                final int nextHandlerIndex = handlerIndex + 1;
                final String nextLvarSpec = handlerSpecs.get(nextHandlerIndex).lvarSpec;
                commonLvarSpec = commonPrefix(lvarSpec, nextLvarSpec);
                // We don't chop symbols in half
                assert Character.isUpperCase(commonLvarSpec.charAt(commonLvarSpec.length() - 1));

                // Let's find if we already have a declaration for such handler, or we need to insert it.
                {
                    boolean addNewHandler = true;
                    int commonHandlerIndex = nextHandlerIndex;
                    for(; commonHandlerIndex < handlerSpecs.size(); ++commonHandlerIndex) {
                        final OptimismExceptionHandlerSpec forwardHandlerSpec = handlerSpecs.get(commonHandlerIndex);
                        final String forwardLvarSpec = forwardHandlerSpec.lvarSpec;
                        if(forwardLvarSpec.equals(commonLvarSpec)) {
                            // We already have a handler for the common prefix.
                            addNewHandler = false;
                            // Make sure we mark it as a delegation target.
                            forwardHandlerSpec.delegationTarget = true;
                            break;
                        } else if(!forwardLvarSpec.startsWith(commonLvarSpec)) {
                            break;
                        }
                    }
                    if(addNewHandler) {
                        // We need to insert a common prefix handler. Note handlers created with catchTarget == false
                        // will automatically have delegationTarget == true (because that's the only reason for their
                        // existence).
                        handlerSpecs.add(commonHandlerIndex, new OptimismExceptionHandlerSpec(commonLvarSpec, false));
                    }
                }

                firstArrayIndex = countSymbolsInLvarTypeDescriptor(commonLvarSpec);
                lvarIndex = 0;
                for(int j = 0; j < commonLvarSpec.length(); ++j) {
                    lvarIndex += CodeGeneratorLexicalContext.getTypeForSlotDescriptor(commonLvarSpec.charAt(j)).getSlots();
                }
                firstLvarIndex = lvarIndex;

                // Create a delegation label if not already present
                delegationLabel = delegationLabels.get(commonLvarSpec);
                if(delegationLabel == null) {
                    // uo_pa == "unwarranted optimism, populate array"
                    delegationLabel = new Label("uo_pa_" + commonLvarSpec);
                    delegationLabels.put(commonLvarSpec, delegationLabel);
                }
            }

            // Load local variables handled by this handler on stack
            int args = 0;
            boolean symbolHadValue = false;
            for(int typeIndex = commonLvarSpec == null ? 0 : commonLvarSpec.length(); typeIndex < lvarSpec.length(); ++typeIndex) {
                final char typeDesc = lvarSpec.charAt(typeIndex);
                final Type lvarType = CodeGeneratorLexicalContext.getTypeForSlotDescriptor(typeDesc);
                if (!lvarType.isUnknown()) {
                    method.load(lvarType, lvarIndex);
                    symbolHadValue = true;
                    args++;
                } else if(typeDesc == 'U' && !symbolHadValue) {
                    // Symbol boundary with undefined last value. Check if all previous values for this symbol were also
                    // undefined; if so, emit one explicit Undefined. This serves to ensure that we're emiting exactly
                    // one value for every symbol that uses local slots. While we could in theory ignore symbols that
                    // are undefined (in other words, dead) at the point where this exception was thrown, unfortunately
                    // we can't do it in practice. The reason for this is that currently our liveness analysis is
                    // coarse (it can determine whether a symbol has not been read with a particular type anywhere in
                    // the function being compiled, but that's it), and a symbol being promoted to Object due to a
                    // deoptimization will suddenly show up as "live for Object type", and previously dead U->O
                    // conversions on loop entries will suddenly become alive in the deoptimized method which will then
                    // expect a value for that slot in its continuation handler. If we had precise liveness analysis, we
                    // could go back to excluding known dead symbols from the payload of the RewriteException.
                    if(method.peekType() == Type.UNDEFINED) {
                        method.dup();
                    } else {
                        method.loadUndefined(Type.OBJECT);
                    }
                    args++;
                }
                if(Character.isUpperCase(typeDesc)) {
                    // Reached symbol boundary; reset flag for the next symbol.
                    symbolHadValue = false;
                }
                lvarIndex += lvarType.getSlots();
            }
            assert args > 0;
            // Delegate actual storing into array to an array populator utility method.
            //on the stack:
            // object array to be populated
            // start index
            // a lot of types
            method.dynamicArrayPopulatorCall(args + 1, firstArrayIndex);
            if(delegationLabel != null) {
                // We cascade to a prefix handler to fill out the rest of the local variables and throw the
                // RewriteException.
                assert !lastHandler;
                assert commonLvarSpec != null;
                // Must undefine the local variables that we have already processed for the sake of correct join on the
                // delegate label
                method.undefineLocalVariables(firstLvarIndex, true);
                final OptimismExceptionHandlerSpec nextSpec = handlerSpecs.get(handlerIndex + 1);
                // If the delegate immediately follows, and it's not a catch target (so it doesn't have array setup
                // code) don't bother emitting a jump, as we'd just jump to the next instruction.
                if(!nextSpec.lvarSpec.equals(commonLvarSpec) || nextSpec.catchTarget) {
                    method._goto(delegationLabel);
                }
            } else {
                assert lastHandler;
                // Nothing to delegate to, so this handler must create and throw the RewriteException.
                // At this point we have the UnwarrantedOptimismException and the Object[] with local variables on
                // stack. We need to create a RewriteException, push two references to it below the constructor
                // arguments, invoke the constructor, and throw the exception.
                loadConstant(getByteCodeSymbolNames(fn));
                if (isRestOf()) {
                    loadConstant(getContinuationEntryPoints());
                    method.invoke(CREATE_REWRITE_EXCEPTION_REST_OF);
                } else {
                    method.invoke(CREATE_REWRITE_EXCEPTION);
                }
                method.athrow();
            }
        }
        return true;
    }

    private static String[] getByteCodeSymbolNames(final FunctionNode fn) {
        // Only names of local variables on the function level are captured. This information is used to reduce
        // deoptimizations, so as much as we can capture will help. We rely on the fact that function wide variables are
        // all live all the time, so the array passed to rewrite exception contains one element for every slotted symbol
        // here.
        final List<String> names = new ArrayList<>();
        for (final Symbol symbol: fn.getBody().getSymbols()) {
            if (symbol.hasSlot()) {
                if (symbol.isScope()) {
                    // slot + scope can only be true for parameters
                    assert symbol.isParam();
                    names.add(null);
                } else {
                    names.add(symbol.getName());
                }
            }
        }
        return names.toArray(new String[0]);
    }

    private static String commonPrefix(final String s1, final String s2) {
        final int l1 = s1.length();
        final int l = Math.min(l1, s2.length());
        int lms = -1; // last matching symbol
        for(int i = 0; i < l; ++i) {
            final char c1 = s1.charAt(i);
            if(c1 != s2.charAt(i)) {
                return s1.substring(0, lms + 1);
            } else if(Character.isUpperCase(c1)) {
                lms = i;
            }
        }
        return l == l1 ? s1 : s2;
    }

    private static class OptimismExceptionHandlerSpec implements Comparable<OptimismExceptionHandlerSpec> {
        private final String lvarSpec;
        private final boolean catchTarget;
        private boolean delegationTarget;

        OptimismExceptionHandlerSpec(final String lvarSpec, final boolean catchTarget) {
            this.lvarSpec = lvarSpec;
            this.catchTarget = catchTarget;
            if(!catchTarget) {
                delegationTarget = true;
            }
        }

        @Override
        public int compareTo(final OptimismExceptionHandlerSpec o) {
            return lvarSpec.compareTo(o.lvarSpec);
        }

        @Override
        public String toString() {
            final StringBuilder b = new StringBuilder(64).append("[HandlerSpec ").append(lvarSpec);
            if(catchTarget) {
                b.append(", catchTarget");
            }
            if(delegationTarget) {
                b.append(", delegationTarget");
            }
            return b.append("]").toString();
        }
    }

    private static class ContinuationInfo {
        private final Label handlerLabel;
        private Label targetLabel; // Label for the target instruction.
        int lvarCount;
        // Indices of local variables that need to be loaded on the stack when this node completes
        private int[] stackStoreSpec;
        // Types of values loaded on the stack
        private Type[] stackTypes;
        // If non-null, this node should perform the requisite type conversion
        private Type returnValueType;
        // If we are in the middle of an object literal initialization, we need to update the property maps
        private Map<Integer, PropertyMap> objectLiteralMaps;
        // The line number at the continuation point
        private int lineNumber;
        // The active catch label, in case the continuation point is in a try/catch block
        private Label catchLabel;
        // The number of scopes that need to be popped before control is transferred to the catch label.
        private int exceptionScopePops;

        ContinuationInfo() {
            this.handlerLabel = new Label("continuation_handler");
        }

        Label getHandlerLabel() {
            return handlerLabel;
        }

        boolean hasTargetLabel() {
            return targetLabel != null;
        }

        Label getTargetLabel() {
            return targetLabel;
        }

        void setTargetLabel(final Label targetLabel) {
            this.targetLabel = targetLabel;
        }

        int[] getStackStoreSpec() {
            return stackStoreSpec.clone();
        }

        void setStackStoreSpec(final int[] stackStoreSpec) {
            this.stackStoreSpec = stackStoreSpec;
        }

        Type[] getStackTypes() {
            return stackTypes.clone();
        }

        void setStackTypes(final Type[] stackTypes) {
            this.stackTypes = stackTypes;
        }

        Type getReturnValueType() {
            return returnValueType;
        }

        void setReturnValueType(final Type returnValueType) {
            this.returnValueType = returnValueType;
        }

        void setObjectLiteralMap(final int objectLiteralStackDepth, final PropertyMap objectLiteralMap) {
            if (objectLiteralMaps == null) {
                objectLiteralMaps = new HashMap<>();
            }
            objectLiteralMaps.put(objectLiteralStackDepth, objectLiteralMap);
        }

        PropertyMap getObjectLiteralMap(final int stackDepth) {
            return objectLiteralMaps == null ? null : objectLiteralMaps.get(stackDepth);
        }

        @Override
        public String toString() {
             return "[localVariableTypes=" + targetLabel.getStack().getLocalVariableTypesCopy() + ", stackStoreSpec=" +
                     Arrays.toString(stackStoreSpec) + ", returnValueType=" + returnValueType + "]";
        }
    }

    private ContinuationInfo getContinuationInfo() {
        return continuationInfo;
    }

    private void generateContinuationHandler() {
        if (!isRestOf()) {
            return;
        }

        final ContinuationInfo ci = getContinuationInfo();
        method.label(ci.getHandlerLabel());

        // There should never be an exception thrown from the continuation handler, but in case there is (meaning,
        // Nashorn has a bug), then line number 0 will be an indication of where it came from (line numbers are Uint16).
        method.lineNumber(0);

        final Label.Stack stack = ci.getTargetLabel().getStack();
        final List<Type> lvarTypes = stack.getLocalVariableTypesCopy();
        final BitSet symbolBoundary = stack.getSymbolBoundaryCopy();
        final int lvarCount = ci.lvarCount;

        final Type rewriteExceptionType = Type.typeFor(RewriteException.class);
        // Store the RewriteException into an unused local variable slot.
        method.load(rewriteExceptionType, 0);
        method.storeTemp(rewriteExceptionType, lvarCount);
        // Get local variable array
        method.load(rewriteExceptionType, 0);
        method.invoke(RewriteException.GET_BYTECODE_SLOTS);
        // Store local variables. Note that deoptimization might introduce new value types for existing local variables,
        // so we must use both liveLocals and symbolBoundary, as in some cases (when the continuation is inside of a try
        // block) we need to store the incoming value into multiple slots. The optimism exception handlers will have
        // exactly one array element for every symbol that uses bytecode storage. If in the originating method the value
        // was undefined, there will be an explicit Undefined value in the array.
        int arrayIndex = 0;
        for(int lvarIndex = 0; lvarIndex < lvarCount;) {
            final Type lvarType = lvarTypes.get(lvarIndex);
            if(!lvarType.isUnknown()) {
                method.dup();
                method.load(arrayIndex).arrayload();
                final Class<?> typeClass = lvarType.getTypeClass();
                // Deoptimization in array initializers can cause arrays to undergo component type widening
                if(typeClass == long[].class) {
                    method.load(rewriteExceptionType, lvarCount);
                    method.invoke(RewriteException.TO_LONG_ARRAY);
                } else if(typeClass == double[].class) {
                    method.load(rewriteExceptionType, lvarCount);
                    method.invoke(RewriteException.TO_DOUBLE_ARRAY);
                } else if(typeClass == Object[].class) {
                    method.load(rewriteExceptionType, lvarCount);
                    method.invoke(RewriteException.TO_OBJECT_ARRAY);
                } else {
                    if(!(typeClass.isPrimitive() || typeClass == Object.class)) {
                        // NOTE: this can only happen with dead stores. E.g. for the program "1; []; f();" in which the
                        // call to f() will deoptimize the call site, but it'll expect :return to have the type
                        // NativeArray. However, in the more optimal version, :return's only live type is int, therefore
                        // "{O}:return = []" is a dead store, and the variable will be sent into the continuation as
                        // Undefined, however NativeArray can't hold Undefined instance.
                        method.loadType(Type.getInternalName(typeClass));
                        method.invoke(RewriteException.INSTANCE_OR_NULL);
                    }
                    method.convert(lvarType);
                }
                method.storeHidden(lvarType, lvarIndex, false);
            }
            final int nextLvarIndex = lvarIndex + lvarType.getSlots();
            if(symbolBoundary.get(nextLvarIndex - 1)) {
                ++arrayIndex;
            }
            lvarIndex = nextLvarIndex;
        }
        if (AssertsEnabled.assertsEnabled()) {
            method.load(arrayIndex);
            method.invoke(RewriteException.ASSERT_ARRAY_LENGTH);
        } else {
            method.pop();
        }

        final int[]   stackStoreSpec = ci.getStackStoreSpec();
        final Type[]  stackTypes     = ci.getStackTypes();
        final boolean isStackEmpty   = stackStoreSpec.length == 0;
        int replacedObjectLiteralMaps = 0;
        if(!isStackEmpty) {
            // Load arguments on the stack
            for(int i = 0; i < stackStoreSpec.length; ++i) {
                final int slot = stackStoreSpec[i];
                method.load(lvarTypes.get(slot), slot);
                method.convert(stackTypes[i]);
                // stack: s0=object literal being initialized
                // change map of s0 so that the property we are initializing when we failed
                // is now ci.returnValueType
                final PropertyMap map = ci.getObjectLiteralMap(i);
                if (map != null) {
                    method.dup();
                    assert ScriptObject.class.isAssignableFrom(method.peekType().getTypeClass()) : method.peekType().getTypeClass() + " is not a script object";
                    loadConstant(map);
                    method.invoke(ScriptObject.SET_MAP);
                    replacedObjectLiteralMaps++;
                }
            }
        }
        // Must have emitted the code for replacing all object literal maps
        assert ci.objectLiteralMaps == null || ci.objectLiteralMaps.size() == replacedObjectLiteralMaps;
        // Load RewriteException back.
        method.load(rewriteExceptionType, lvarCount);
        // Get rid of the stored reference
        method.loadNull();
        method.storeHidden(Type.OBJECT, lvarCount);
        // Mark it dead
        method.markDeadSlots(lvarCount, Type.OBJECT.getSlots());

        // Load return value on the stack
        method.invoke(RewriteException.GET_RETURN_VALUE);

        final Type returnValueType = ci.getReturnValueType();

        // Set up an exception handler for primitive type conversion of return value if needed
        boolean needsCatch = false;
        final Label targetCatchLabel = ci.catchLabel;
        Label _try = null;
        if(returnValueType.isPrimitive()) {
            // If the conversion throws an exception, we want to report the line number of the continuation point.
            method.lineNumber(ci.lineNumber);

            if(targetCatchLabel != METHOD_BOUNDARY) {
                _try = new Label("");
                method.label(_try);
                needsCatch = true;
            }
        }

        // Convert return value
        method.convert(returnValueType);

        final int scopePopCount = needsCatch ? ci.exceptionScopePops : 0;

        // Declare a try/catch for the conversion. If no scopes need to be popped until the target catch block, just
        // jump into it. Otherwise, we'll need to create a scope-popping catch block below.
        final Label catchLabel = scopePopCount > 0 ? new Label("") : targetCatchLabel;
        if(needsCatch) {
            final Label _end_try = new Label("");
            method.label(_end_try);
            method._try(_try, _end_try, catchLabel);
        }

        // Jump to continuation point
        method._goto(ci.getTargetLabel());

        // Make a scope-popping exception delegate if needed
        if(catchLabel != targetCatchLabel) {
            method.lineNumber(0);
            assert scopePopCount > 0;
            method._catch(catchLabel);
            popScopes(scopePopCount);
            method.uncheckedGoto(targetCatchLabel);
        }
    }

    
Interface implemented by object creators that support splitting over multiple methods.
/**
     * Interface implemented by object creators that support splitting over multiple methods.
     */
    interface SplitLiteralCreator {
        
Generate code to populate a range of the literal object. A reference to the object
should be left on the stack when the method terminates.
Params:
method – the method emitter
type – the type of the literal object
slot – the local slot containing the literal object
start – the start index (inclusive)
end – the end index (exclusive)/**
         * Generate code to populate a range of the literal object. A reference to the object
         * should be left on the stack when the method terminates.
         *
         * @param method the method emitter
         * @param type the type of the literal object
         * @param slot the local slot containing the literal object
         * @param start the start index (inclusive)
         * @param end the end index (exclusive)
         */
        void populateRange(MethodEmitter method, Type type, int slot, int start, int end);
    }
}