xref: /openjdk9/nashorn/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/codegen/MethodEmitter.java

/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package jdk.nashorn.internal.codegen;

import static jdk.internal.org.objectweb.asm.Opcodes.ATHROW;
import static jdk.internal.org.objectweb.asm.Opcodes.CHECKCAST;
import static jdk.internal.org.objectweb.asm.Opcodes.DUP2;
import static jdk.internal.org.objectweb.asm.Opcodes.GETFIELD;
import static jdk.internal.org.objectweb.asm.Opcodes.GETSTATIC;
import static jdk.internal.org.objectweb.asm.Opcodes.GOTO;
import static jdk.internal.org.objectweb.asm.Opcodes.H_INVOKESTATIC;
import static jdk.internal.org.objectweb.asm.Opcodes.IFEQ;
import static jdk.internal.org.objectweb.asm.Opcodes.IFGE;
import static jdk.internal.org.objectweb.asm.Opcodes.IFGT;
import static jdk.internal.org.objectweb.asm.Opcodes.IFLE;
import static jdk.internal.org.objectweb.asm.Opcodes.IFLT;
import static jdk.internal.org.objectweb.asm.Opcodes.IFNE;
import static jdk.internal.org.objectweb.asm.Opcodes.IFNONNULL;
import static jdk.internal.org.objectweb.asm.Opcodes.IFNULL;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ACMPEQ;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ACMPNE;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPEQ;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPGE;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPGT;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPLE;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPLT;
import static jdk.internal.org.objectweb.asm.Opcodes.IF_ICMPNE;
import static jdk.internal.org.objectweb.asm.Opcodes.INSTANCEOF;
import static jdk.internal.org.objectweb.asm.Opcodes.INVOKEINTERFACE;
import static jdk.internal.org.objectweb.asm.Opcodes.INVOKESPECIAL;
import static jdk.internal.org.objectweb.asm.Opcodes.INVOKESTATIC;
import static jdk.internal.org.objectweb.asm.Opcodes.INVOKEVIRTUAL;
import static jdk.internal.org.objectweb.asm.Opcodes.NEW;
import static jdk.internal.org.objectweb.asm.Opcodes.PUTFIELD;
import static jdk.internal.org.objectweb.asm.Opcodes.PUTSTATIC;
import static jdk.internal.org.objectweb.asm.Opcodes.RETURN;
import static jdk.nashorn.internal.codegen.CompilerConstants.ARGUMENTS;
import static jdk.nashorn.internal.codegen.CompilerConstants.CONSTANTS;
import static jdk.nashorn.internal.codegen.CompilerConstants.SCOPE;
import static jdk.nashorn.internal.codegen.CompilerConstants.THIS;
import static jdk.nashorn.internal.codegen.CompilerConstants.THIS_DEBUGGER;
import static jdk.nashorn.internal.codegen.CompilerConstants.VARARGS;
import static jdk.nashorn.internal.codegen.CompilerConstants.className;
import static jdk.nashorn.internal.codegen.CompilerConstants.constructorNoLookup;
import static jdk.nashorn.internal.codegen.CompilerConstants.methodDescriptor;
import static jdk.nashorn.internal.codegen.CompilerConstants.staticField;
import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCallNoLookup;
import static jdk.nashorn.internal.codegen.ObjectClassGenerator.PRIMITIVE_FIELD_TYPE;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_OPTIMISTIC;
import static jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor.CALLSITE_PROGRAM_POINT_SHIFT;

import java.io.PrintStream;
import java.lang.reflect.Array;
import java.util.Collection;
import java.util.EnumSet;
import java.util.IdentityHashMap;
import java.util.List;
import java.util.Map;
import jdk.internal.dynalink.support.NameCodec;
import jdk.internal.org.objectweb.asm.Handle;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.nashorn.internal.codegen.ClassEmitter.Flag;
import jdk.nashorn.internal.codegen.CompilerConstants.Call;
import jdk.nashorn.internal.codegen.CompilerConstants.FieldAccess;
import jdk.nashorn.internal.codegen.types.ArrayType;
import jdk.nashorn.internal.codegen.types.BitwiseType;
import jdk.nashorn.internal.codegen.types.NumericType;
import jdk.nashorn.internal.codegen.types.Type;
import jdk.nashorn.internal.ir.FunctionNode;
import jdk.nashorn.internal.ir.IdentNode;
import jdk.nashorn.internal.ir.JoinPredecessor;
import jdk.nashorn.internal.ir.LiteralNode;
import jdk.nashorn.internal.ir.LocalVariableConversion;
import jdk.nashorn.internal.ir.Symbol;
import jdk.nashorn.internal.ir.TryNode;
import jdk.nashorn.internal.objects.NativeArray;
import jdk.nashorn.internal.runtime.ArgumentSetter;
import jdk.nashorn.internal.runtime.Context;
import jdk.nashorn.internal.runtime.Debug;
import jdk.nashorn.internal.runtime.JSType;
import jdk.nashorn.internal.runtime.RewriteException;
import jdk.nashorn.internal.runtime.Scope;
import jdk.nashorn.internal.runtime.ScriptObject;
import jdk.nashorn.internal.runtime.ScriptRuntime;
import jdk.nashorn.internal.runtime.UnwarrantedOptimismException;
import jdk.nashorn.internal.runtime.linker.Bootstrap;
import jdk.nashorn.internal.runtime.logging.DebugLogger;
import jdk.nashorn.internal.runtime.options.Options;

/**
 * This is the main function responsible for emitting method code
 * in a class. It maintains a type stack and keeps track of control
 * flow to make sure that the registered instructions don't violate
 * byte code verification.
 *
 * Running Nashorn with -ea will assert as soon as a type stack
 * becomes corrupt, for easier debugging
 *
 * Running Nashorn with -Dnashorn.codegen.debug=true will print
 * all generated bytecode and labels to stderr, for easier debugging,
 * including bytecode stack contents
 */
public class MethodEmitter {
    /** The ASM MethodVisitor we are plugged into */
    private final MethodVisitor method;

    /** Parent classEmitter representing the class of this method */
    private final ClassEmitter classEmitter;

    /** FunctionNode representing this method, or null if none exists */
    protected FunctionNode functionNode;

    /** Current type stack for current evaluation */
    private Label.Stack stack;

    private boolean preventUndefinedLoad;

    /**
     * Map of live local variable definitions.
     */
    private final Map<Symbol, LocalVariableDef> localVariableDefs = new IdentityHashMap<>();

    /** The context */
    private final Context context;

    /** Threshold in chars for when string constants should be split */
    static final int LARGE_STRING_THRESHOLD = 32 * 1024;

    /** Debug flag, should we dump all generated bytecode along with stacks? */
    private final DebugLogger log;
    private final boolean     debug;

    /** dump stack on a particular line, or -1 if disabled */
    private static final int DEBUG_TRACE_LINE;

    static {
        final String tl = Options.getStringProperty("nashorn.codegen.debug.trace", "-1");
        int line = -1;
        try {
            line = Integer.parseInt(tl);
        } catch (final NumberFormatException e) {
            //fallthru
        }
        DEBUG_TRACE_LINE = line;
    }

    /** Bootstrap for normal indy:s */
    private static final Handle LINKERBOOTSTRAP  = new Handle(H_INVOKESTATIC, Bootstrap.BOOTSTRAP.className(), Bootstrap.BOOTSTRAP.name(), Bootstrap.BOOTSTRAP.descriptor());

    /** Bootstrap for array populators */
    private static final Handle POPULATE_ARRAY_BOOTSTRAP = new Handle(H_INVOKESTATIC, RewriteException.BOOTSTRAP.className(), RewriteException.BOOTSTRAP.name(), RewriteException.BOOTSTRAP.descriptor());

    /**
     * Constructor - internal use from ClassEmitter only
     * @see ClassEmitter#method
     *
     * @param classEmitter the class emitter weaving the class this method is in
     * @param method       a method visitor
     */
    MethodEmitter(final ClassEmitter classEmitter, final MethodVisitor method) {
        this(classEmitter, method, null);
    }

    /**
     * Constructor - internal use from ClassEmitter only
     * @see ClassEmitter#method
     *
     * @param classEmitter the class emitter weaving the class this method is in
     * @param method       a method visitor
     * @param functionNode a function node representing this method
     */
    MethodEmitter(final ClassEmitter classEmitter, final MethodVisitor method, final FunctionNode functionNode) {
        this.context      = classEmitter.getContext();
        this.classEmitter = classEmitter;
        this.method       = method;
        this.functionNode = functionNode;
        this.stack        = null;
        this.log          = context.getLogger(CodeGenerator.class);
        this.debug        = log.isEnabled();
    }

    /**
     * Begin a method
     */
    public void begin() {
        classEmitter.beginMethod(this);
        newStack();
        method.visitCode();
    }

    /**
     * End a method
     */
    public void end() {
        method.visitMaxs(0, 0);
        method.visitEnd();

        classEmitter.endMethod(this);
    }

    boolean isReachable() {
        return stack != null;
    }

    private void doesNotContinueSequentially() {
        stack = null;
    }

    private void newStack() {
        stack = new Label.Stack();
    }

    @Override
    public String toString() {
        return "methodEmitter: " + (functionNode == null ? method : functionNode.getName()).toString() + ' ' + Debug.id(this);
    }

    /**
     * Push a type to the existing stack
     * @param type the type
     */
    void pushType(final Type type) {
        if (type != null) {
            stack.push(type);
        }
    }

    /**
     * Pop a type from the existing stack
     *
     * @param expected expected type - will assert if wrong
     *
     * @return the type that was retrieved
     */
    private Type popType(final Type expected) {
        final Type type = popType();
        assert type.isObject() && expected.isObject() ||
            type.isEquivalentTo(expected) : type + " is not compatible with " + expected;
        return type;
    }

    /**
     * Pop a type from the existing stack, no matter what it is.
     *
     * @return the type
     */
    private Type popType() {
        return stack.pop();
    }

    /**
     * Pop a type from the existing stack, ensuring that it is numeric. Boolean type is popped as int type.
     *
     * @return the type
     */
    private NumericType popNumeric() {
        final Type type = popType();
        if(type.isBoolean()) {
            // Booleans are treated as int for purposes of arithmetic operations
            return Type.INT;
        }
        assert type.isNumeric();
        return (NumericType)type;
    }

    /**
     * Pop a type from the existing stack, ensuring that it is an integer type
     * (integer or long). Boolean type is popped as int type.
     *
     * @return the type
     */
    private BitwiseType popBitwise() {
        final Type type = popType();
        if(type == Type.BOOLEAN) {
            return Type.INT;
        }
        return (BitwiseType)type;
    }

    private BitwiseType popInteger() {
        final Type type = popType();
        if(type == Type.BOOLEAN) {
            return Type.INT;
        }
        assert type == Type.INT;
        return (BitwiseType)type;
    }

    /**
     * Pop a type from the existing stack, ensuring that it is an array type,
     * assert if not
     *
     * @return the type
     */
    private ArrayType popArray() {
        final Type type = popType();
        assert type.isArray() : type;
        return (ArrayType)type;
    }

    /**
     * Peek a given number of slots from the top of the stack and return the
     * type in that slot
     *
     * @param pos the number of positions from the top, 0 is the top element
     *
     * @return the type at position "pos" on the stack
     */
    final Type peekType(final int pos) {
        return stack.peek(pos);
    }

    /**
     * Peek at the type at the top of the stack
     *
     * @return the type at the top of the stack
     */
    final Type peekType() {
        return stack.peek();
    }

    /**
     * Generate code a for instantiating a new object and push the
     * object type on the stack
     *
     * @param classDescriptor class descriptor for the object type
     * @param type the type of the new object
     *
     * @return the method emitter
     */
    MethodEmitter _new(final String classDescriptor, final Type type) {
        debug("new", classDescriptor);
        method.visitTypeInsn(NEW, classDescriptor);
        pushType(type);
        return this;
    }

    /**
     * Generate code a for instantiating a new object and push the
     * object type on the stack
     *
     * @param clazz class type to instatiate
     *
     * @return the method emitter
     */
    MethodEmitter _new(final Class<?> clazz) {
        return _new(className(clazz), Type.typeFor(clazz));
    }

    /**
     * Generate code to call the empty constructor for a class
     *
     * @param clazz class type to instatiate
     *
     * @return the method emitter
     */
    MethodEmitter newInstance(final Class<?> clazz) {
        return invoke(constructorNoLookup(clazz));
    }

    /**
     * Perform a dup, that is, duplicate the top element and
     * push the duplicate down a given number of positions
     * on the stack. This is totally type agnostic.
     *
     * @param depth the depth on which to put the copy
     *
     * @return the method emitter, or null if depth is illegal and
     *  has no instruction equivalent.
     */
    MethodEmitter dup(final int depth) {
        if (peekType().dup(method, depth) == null) {
            return null;
        }

        debug("dup", depth);

        switch (depth) {
        case 0: {
            final int l0 = stack.getTopLocalLoad();
            pushType(peekType());
            stack.markLocalLoad(l0);
            break;
        }
        case 1: {
            final int l0 = stack.getTopLocalLoad();
            final Type p0 = popType();
            final int l1 = stack.getTopLocalLoad();
            final Type p1 = popType();
            pushType(p0);
            stack.markLocalLoad(l0);
            pushType(p1);
            stack.markLocalLoad(l1);
            pushType(p0);
            stack.markLocalLoad(l0);
            break;
        }
        case 2: {
            final int l0 = stack.getTopLocalLoad();
            final Type p0 = popType();
            final int l1 = stack.getTopLocalLoad();
            final Type p1 = popType();
            final int l2 = stack.getTopLocalLoad();
            final Type p2 = popType();
            pushType(p0);
            stack.markLocalLoad(l0);
            pushType(p2);
            stack.markLocalLoad(l2);
            pushType(p1);
            stack.markLocalLoad(l1);
            pushType(p0);
            stack.markLocalLoad(l0);
            break;
        }
        default:
            assert false : "illegal dup depth = " + depth;
            return null;
        }

        return this;
    }

    /**
     * Perform a dup2, that is, duplicate the top element if it
     * is a category 2 type, or two top elements if they are category
     * 1 types, and push them on top of the stack
     *
     * @return the method emitter
     */
    MethodEmitter dup2() {
        debug("dup2");

        if (peekType().isCategory2()) {
            final int l0 = stack.getTopLocalLoad();
            pushType(peekType());
            stack.markLocalLoad(l0);
        } else {
            final int l0 = stack.getTopLocalLoad();
            final Type p0 = popType();
            final int l1 = stack.getTopLocalLoad();
            final Type p1 = popType();
            pushType(p0);
            stack.markLocalLoad(l0);
            pushType(p1);
            stack.markLocalLoad(l1);
            pushType(p0);
            stack.markLocalLoad(l0);
            pushType(p1);
            stack.markLocalLoad(l1);
        }
        method.visitInsn(DUP2);
        return this;
    }

    /**
     * Duplicate the top element on the stack and push it
     *
     * @return the method emitter
     */
    MethodEmitter dup() {
        return dup(0);
    }

    /**
     * Pop the top element of the stack and throw it away
     *
     * @return the method emitter
     */
    MethodEmitter pop() {
        debug("pop", peekType());
        popType().pop(method);
        return this;
    }

    /**
     * Pop the top element of the stack if category 2 type, or the two
     * top elements of the stack if category 1 types
     *
     * @return the method emitter
     */
    MethodEmitter pop2() {
        if (peekType().isCategory2()) {
            popType();
        } else {
            get2n();
        }
        return this;
    }

    /**
     * Swap the top two elements of the stack. This is totally
     * type agnostic and works for all types
     *
     * @return the method emitter
     */
    MethodEmitter swap() {
        debug("swap");

        final int l0 = stack.getTopLocalLoad();
        final Type p0 = popType();
        final int l1 = stack.getTopLocalLoad();
        final Type p1 = popType();
        p0.swap(method, p1);

        pushType(p0);
        stack.markLocalLoad(l0);
        pushType(p1);
        stack.markLocalLoad(l1);
        return this;
    }

    void pack() {
        final Type type = peekType();
        if (type.isInteger()) {
            convert(PRIMITIVE_FIELD_TYPE);
        } else if (type.isLong()) {
            //nop
        } else if (type.isNumber()) {
            invokestatic("java/lang/Double", "doubleToRawLongBits", "(D)J");
        } else {
            assert false : type + " cannot be packed!";
        }
        //all others are nops, objects aren't packed
    }

    /**
     * Initializes a bytecode method parameter
     * @param symbol the symbol for the parameter
     * @param type the type of the parameter
     * @param start the label for the start of the method
     */
    void initializeMethodParameter(final Symbol symbol, final Type type, final Label start) {
        assert symbol.isBytecodeLocal();
        localVariableDefs.put(symbol, new LocalVariableDef(start.getLabel(), type));
    }

    /**
     * Create a new string builder, call the constructor and push the instance to the stack.
     *
     * @return the method emitter
     */
    MethodEmitter newStringBuilder() {
        return invoke(constructorNoLookup(StringBuilder.class)).dup();
    }

    /**
     * Pop a string and a StringBuilder from the top of the stack and call the append
     * function of the StringBuilder, appending the string. Pushes the StringBuilder to
     * the stack when finished.
     *
     * @return the method emitter
     */
    MethodEmitter stringBuilderAppend() {
        convert(Type.STRING);
        return invoke(virtualCallNoLookup(StringBuilder.class, "append", StringBuilder.class, String.class));
    }

    /**
     * Pops two integer types from the stack, performs a bitwise and and pushes
     * the result
     *
     * @return the method emitter
     */
    MethodEmitter and() {
        debug("and");
        pushType(get2i().and(method));
        return this;
    }

    /**
     * Pops two integer types from the stack, performs a bitwise or and pushes
     * the result
     *
     * @return the method emitter
     */
    MethodEmitter or() {
        debug("or");
        pushType(get2i().or(method));
        return this;
    }

    /**
     * Pops two integer types from the stack, performs a bitwise xor and pushes
     * the result
     *
     * @return the method emitter
     */
    MethodEmitter xor() {
        debug("xor");
        pushType(get2i().xor(method));
        return this;
    }

    /**
     * Pops two integer types from the stack, performs a bitwise logic shift right and pushes
     * the result. The shift count, the first element, must be INT.
     *
     * @return the method emitter
     */
    MethodEmitter shr() {
        debug("shr");
        popInteger();
        pushType(popBitwise().shr(method));
        return this;
    }

    /**
     * Pops two integer types from the stack, performs a bitwise shift left and and pushes
     * the result. The shift count, the first element, must be INT.
     *
     * @return the method emitter
     */
    MethodEmitter shl() {
        debug("shl");
        popInteger();
        pushType(popBitwise().shl(method));
        return this;
    }

    /**
     * Pops two integer types from the stack, performs a bitwise arithmetic shift right and pushes
     * the result. The shift count, the first element, must be INT.
     *
     * @return the method emitter
     */
    MethodEmitter sar() {
        debug("sar");
        popInteger();
        pushType(popBitwise().sar(method));
        return this;
    }

    /**
     * Pops a numeric type from the stack, negates it and pushes the result
     *
     * @return the method emitter
     */
    MethodEmitter neg(final int programPoint) {
        debug("neg");
        pushType(popNumeric().neg(method, programPoint));
        return this;
    }

    /**
     * Add label for the start of a catch block and push the exception to the
     * stack
     *
     * @param recovery label pointing to start of catch block
     */
    void _catch(final Label recovery) {
        // While in JVM a catch block can be reached through normal control flow, our code generator never does this,
        // so we might as well presume there's no stack on entry.
        assert stack == null;
        recovery.onCatch();
        label(recovery);
        beginCatchBlock();
    }

    /**
     * Add any number of labels for the start of a catch block and push the exception to the
     * stack
     *
     * @param recoveries labels pointing to start of catch block
     */
    void _catch(final Collection<Label> recoveries) {
        assert stack == null;
        for(final Label l: recoveries) {
            label(l);
        }
        beginCatchBlock();
    }

    private void beginCatchBlock() {
        // It can happen that the catch label wasn't marked as reachable. They are marked as reachable if there's an
        // assignment in the try block, but it's possible that there was none.
        if(!isReachable()) {
            newStack();
        }
        pushType(Type.typeFor(Throwable.class));
    }
    /**
     * Start a try/catch block.
     *
     * @param entry          start label for try
     * @param exit           end label for try
     * @param recovery       start label for catch
     * @param typeDescriptor type descriptor for exception
     * @param isOptimismHandler true if this is a hander for {@code UnwarrantedOptimismException}. Normally joining on a
     * catch handler kills temporary variables, but optimism handlers are an exception, as they need to capture
     * temporaries as well, so they must remain live.
     */
    private void _try(final Label entry, final Label exit, final Label recovery, final String typeDescriptor, final boolean isOptimismHandler) {
        recovery.joinFromTry(entry.getStack(), isOptimismHandler);
        method.visitTryCatchBlock(entry.getLabel(), exit.getLabel(), recovery.getLabel(), typeDescriptor);
    }

    /**
     * Start a try/catch block.
     *
     * @param entry    start label for try
     * @param exit     end label for try
     * @param recovery start label for catch
     * @param clazz    exception class
     */
    void _try(final Label entry, final Label exit, final Label recovery, final Class<?> clazz) {
        _try(entry, exit, recovery, CompilerConstants.className(clazz), clazz == UnwarrantedOptimismException.class);
    }

    /**
     * Start a try/catch block. The catch is "Throwable" - i.e. catch-all
     *
     * @param entry    start label for try
     * @param exit     end label for try
     * @param recovery start label for catch
     */
    void _try(final Label entry, final Label exit, final Label recovery) {
        _try(entry, exit, recovery, (String)null, false);
    }

    void markLabelAsOptimisticCatchHandler(final Label label, final int liveLocalCount) {
        label.markAsOptimisticCatchHandler(stack, liveLocalCount);
    }

    /**
     * Load the constants array
     * @return this method emitter
     */
    MethodEmitter loadConstants() {
        getStatic(classEmitter.getUnitClassName(), CONSTANTS.symbolName(), CONSTANTS.descriptor());
        assert peekType().isArray() : peekType();
        return this;
    }

    /**
     * Push the undefined value for the given type, i.e.
     * UNDEFINED or UNDEFINEDNUMBER. Currently we have no way of
     * representing UNDEFINED for INTs and LONGs, so they are not
     * allowed to be local variables (yet)
     *
     * @param type the type for which to push UNDEFINED
     * @return the method emitter
     */
    MethodEmitter loadUndefined(final Type type) {
        debug("load undefined ", type);
        pushType(type.loadUndefined(method));
        return this;
    }

    MethodEmitter loadForcedInitializer(final Type type) {
        debug("load forced initializer ", type);
        pushType(type.loadForcedInitializer(method));
        return this;
    }

    /**
     * Push the empty value for the given type, i.e. EMPTY.
     *
     * @param type the type
     * @return the method emitter
     */
    MethodEmitter loadEmpty(final Type type) {
        debug("load empty ", type);
        pushType(type.loadEmpty(method));
        return this;
    }

    /**
     * Push null to stack
     *
     * @return the method emitter
     */
    MethodEmitter loadNull() {
        debug("aconst_null");
        pushType(Type.OBJECT.ldc(method, null));
        return this;
    }

    /**
     * Push a handle representing this class top stack
     *
     * @param className name of the class
     *
     * @return the method emitter
     */
    MethodEmitter loadType(final String className) {
        debug("load type", className);
        method.visitLdcInsn(jdk.internal.org.objectweb.asm.Type.getObjectType(className));
        pushType(Type.OBJECT);
        return this;
    }

    /**
     * Push a boolean constant to the stack.
     *
     * @param b value of boolean
     *
     * @return the method emitter
     */
    MethodEmitter load(final boolean b) {
        debug("load boolean", b);
        pushType(Type.BOOLEAN.ldc(method, b));
        return this;
    }

    /**
     * Push an int constant to the stack
     *
     * @param i value of the int
     *
     * @return the method emitter
     */
    MethodEmitter load(final int i) {
        debug("load int", i);
        pushType(Type.INT.ldc(method, i));
        return this;
    }

    /**
     * Push a double constant to the stack
     *
     * @param d value of the double
     *
     * @return the method emitter
     */
    MethodEmitter load(final double d) {
        debug("load double", d);
        pushType(Type.NUMBER.ldc(method, d));
        return this;
    }

    /**
     * Push an long constant to the stack
     *
     * @param l value of the long
     *
     * @return the method emitter
     */
    MethodEmitter load(final long l) {
        debug("load long", l);
        pushType(Type.LONG.ldc(method, l));
        return this;
    }

    /**
     * Fetch the length of an array.
     * @return Array length.
     */
    MethodEmitter arraylength() {
        debug("arraylength");
        popType(Type.OBJECT);
        pushType(Type.OBJECT_ARRAY.arraylength(method));
        return this;
    }

    /**
     * Push a String constant to the stack
     *
     * @param s value of the String
     *
     * @return the method emitter
     */
    MethodEmitter load(final String s) {
        debug("load string", s);

        if (s == null) {
            loadNull();
            return this;
        }

        //NASHORN-142 - split too large string
        final int length = s.length();
        if (length > LARGE_STRING_THRESHOLD) {

            _new(StringBuilder.class);
            dup();
            load(length);
            invoke(constructorNoLookup(StringBuilder.class, int.class));

            for (int n = 0; n < length; n += LARGE_STRING_THRESHOLD) {
                final String part = s.substring(n, Math.min(n + LARGE_STRING_THRESHOLD, length));
                load(part);
                stringBuilderAppend();
            }

            invoke(virtualCallNoLookup(StringBuilder.class, "toString", String.class));

            return this;
        }

        pushType(Type.OBJECT.ldc(method, s));
        return this;
    }

    /**
     * Pushes the value of an identifier to the stack. If the identifier does not represent a local variable or a
     * parameter, this will be a no-op.
     *
     * @param ident the identifier for the variable being loaded.
     *
     * @return the method emitter
     */
    MethodEmitter load(final IdentNode ident) {
        return load(ident.getSymbol(), ident.getType());
    }

    /**
     * Pushes the value of the symbol to the stack with the specified type. No type conversion is being performed, and
     * the type is only being used if the symbol addresses a local variable slot. The value of the symbol is loaded if
     * it addresses a local variable slot, or it is a parameter (in which case it can also be loaded from a vararg array
     * or the arguments object). If it is neither, the operation is a no-op.
     *
     * @param symbol the symbol addressing the value being loaded
     * @param type the presumed type of the value when it is loaded from a local variable slot
     * @return the method emitter
     */
    MethodEmitter load(final Symbol symbol, final Type type) {
        assert symbol != null;
        if (symbol.hasSlot()) {
            final int slot = symbol.getSlot(type);
            debug("load symbol", symbol.getName(), " slot=", slot, "type=", type);
            load(type, slot);
           // _try(new Label("dummy"), new Label("dummy2"), recovery);
           // method.visitTryCatchBlock(new Label(), arg1, arg2, arg3);
        } else if (symbol.isParam()) {
            assert functionNode.isVarArg() : "Non-vararg functions have slotted parameters";
            final int index = symbol.getFieldIndex();
            if (functionNode.needsArguments()) {
                // ScriptObject.getArgument(int) on arguments
                debug("load symbol", symbol.getName(), " arguments index=", index);
                loadCompilerConstant(ARGUMENTS);
                load(index);
                ScriptObject.GET_ARGUMENT.invoke(this);
            } else {
                // array load from __varargs__
                debug("load symbol", symbol.getName(), " array index=", index);
                loadCompilerConstant(VARARGS);
                load(symbol.getFieldIndex());
                arrayload();
            }
        }
        return this;
    }

    /**
     * Push a local variable to the stack, given an explicit bytecode slot.
     * This is used e.g. for stub generation where we know where items like
     * "this" and "scope" reside.
     *
     * @param type  the type of the variable
     * @param slot  the slot the variable is in
     *
     * @return the method emitter
     */
    MethodEmitter load(final Type type, final int slot) {
        debug("explicit load", type, slot);
        final Type loadType = type.load(method, slot);
        assert loadType != null;
        pushType(loadType == Type.OBJECT && isThisSlot(slot) ? Type.THIS : loadType);
        assert !preventUndefinedLoad || (slot < stack.localVariableTypes.size() && stack.localVariableTypes.get(slot) != Type.UNKNOWN)
            : "Attempted load of uninitialized slot " + slot + " (as type " + type + ")";
        stack.markLocalLoad(slot);
        return this;
    }

    private boolean isThisSlot(final int slot) {
        if (functionNode == null) {
            return slot == CompilerConstants.JAVA_THIS.slot();
        }
        final int thisSlot = getCompilerConstantSymbol(THIS).getSlot(Type.OBJECT);
        assert !functionNode.needsCallee() || thisSlot == 1; // needsCallee -> thisSlot == 1
        assert functionNode.needsCallee() || thisSlot == 0; // !needsCallee -> thisSlot == 0
        return slot == thisSlot;
    }

    /**
     * Push a method handle to the stack
     *
     * @param className  class name
     * @param methodName method name
     * @param descName   descriptor
     * @param flags      flags that describe this handle, e.g. invokespecial new, or invoke virtual
     *
     * @return the method emitter
     */
    MethodEmitter loadHandle(final String className, final String methodName, final String descName, final EnumSet<Flag> flags) {
        debug("load handle ");
        pushType(Type.OBJECT.ldc(method, new Handle(Flag.getValue(flags), className, methodName, descName)));
        return this;
    }

    private Symbol getCompilerConstantSymbol(final CompilerConstants cc) {
        return functionNode.getBody().getExistingSymbol(cc.symbolName());
    }

    /**
     * True if this method has a slot allocated for the scope variable (meaning, something in the method actually needs
     * the scope).
     * @return if this method has a slot allocated for the scope variable.
     */
    boolean hasScope() {
        return getCompilerConstantSymbol(SCOPE).hasSlot();
    }

    MethodEmitter loadCompilerConstant(final CompilerConstants cc) {
        return loadCompilerConstant(cc, null);
    }

    MethodEmitter loadCompilerConstant(final CompilerConstants cc, final Type type) {
        if (cc == SCOPE && peekType() == Type.SCOPE) {
            dup();
            return this;
        }
        return load(getCompilerConstantSymbol(cc), type != null ? type : getCompilerConstantType(cc));
    }

    MethodEmitter loadScope() {
        return loadCompilerConstant(SCOPE).checkcast(Scope.class);
    }

    MethodEmitter setSplitState(final int state) {
        return loadScope().load(state).invoke(Scope.SET_SPLIT_STATE);
    }

    void storeCompilerConstant(final CompilerConstants cc) {
        storeCompilerConstant(cc, null);
    }

    void storeCompilerConstant(final CompilerConstants cc, final Type type) {
        final Symbol symbol = getCompilerConstantSymbol(cc);
        if(!symbol.hasSlot()) {
            return;
        }
        debug("store compiler constant ", symbol);
        store(symbol, type != null ? type : getCompilerConstantType(cc));
    }

    private static Type getCompilerConstantType(final CompilerConstants cc) {
        final Class<?> constantType = cc.type();
        assert constantType != null;
        return Type.typeFor(constantType);
    }

    /**
     * Load an element from an array, determining type automatically
     * @return the method emitter
     */
    MethodEmitter arrayload() {
        debug("Xaload");
        popType(Type.INT);
        pushType(popArray().aload(method));
        return this;
    }

    /**
     * Pop a value, an index and an array from the stack and store
     * the value at the given index in the array.
     */
    void arraystore() {
        debug("Xastore");
        final Type value = popType();
        final Type index = popType(Type.INT);
        assert index.isInteger() : "array index is not integer, but " + index;
        final ArrayType array = popArray();

        assert value.isEquivalentTo(array.getElementType()) : "Storing "+value+" into "+array;
        assert array.isObject();
        array.astore(method);
    }

    /**
     * Pop a value from the stack and store it in a local variable represented
     * by the given identifier. If the symbol has no slot, this is a NOP
     *
     * @param ident identifier to store stack to
     */
    void store(final IdentNode ident) {
        final Type type = ident.getType();
        final Symbol symbol = ident.getSymbol();
        if(type == Type.UNDEFINED) {
            assert peekType() == Type.UNDEFINED;
            store(symbol, Type.OBJECT);
        } else {
            store(symbol, type);
        }
    }

    /**
     * Represents a definition of a local variable with a type. Used for local variable table building.
     */
    private static class LocalVariableDef {
        // The start label from where this definition lives.
        private final jdk.internal.org.objectweb.asm.Label label;
        // The currently live type of the local variable.
        private final Type type;

        LocalVariableDef(final jdk.internal.org.objectweb.asm.Label label, final Type type) {
            this.label = label;
            this.type = type;
        }

    }

    void closeLocalVariable(final Symbol symbol, final Label label) {
        final LocalVariableDef def = localVariableDefs.get(symbol);
        if(def != null) {
            endLocalValueDef(symbol, def, label.getLabel());
        }
        if(isReachable()) {
            markDeadLocalVariable(symbol);
        }
    }

    void markDeadLocalVariable(final Symbol symbol) {
        if(!symbol.isDead()) {
            markDeadSlots(symbol.getFirstSlot(), symbol.slotCount());
        }
    }

    void markDeadSlots(final int firstSlot, final int slotCount) {
        stack.markDeadLocalVariables(firstSlot, slotCount);
    }

    private void endLocalValueDef(final Symbol symbol, final LocalVariableDef def, final jdk.internal.org.objectweb.asm.Label label) {
        String name = symbol.getName();
        if (name.equals(THIS.symbolName())) {
            name = THIS_DEBUGGER.symbolName();
        }
        method.visitLocalVariable(name, def.type.getDescriptor(), null, def.label, label, symbol.getSlot(def.type));
    }

    void store(final Symbol symbol, final Type type) {
        store(symbol, type, true);
    }

    /**
     * Pop a value from the stack and store it in a variable denoted by the given symbol. The variable should be either
     * a local variable, or a function parameter (and not a scoped variable). For local variables, this method will also
     * do the bookkeeping of the local variable table as well as mark values in all alternative slots for the symbol as
     * dead. In this regard it differs from {@link #storeHidden(Type, int)}.
     *
     * @param symbol the symbol to store into.
     * @param type the type to store
     * @param onlySymbolLiveValue if true, this is the sole live value for the symbol. If false, currently live values should
     * be kept live.
     */
    void store(final Symbol symbol, final Type type, final boolean onlySymbolLiveValue) {
        assert symbol != null : "No symbol to store";
        if (symbol.hasSlot()) {
            final boolean isLiveType = symbol.hasSlotFor(type);
            final LocalVariableDef existingDef = localVariableDefs.get(symbol);
            if(existingDef == null || existingDef.type != type) {
                final jdk.internal.org.objectweb.asm.Label here = new jdk.internal.org.objectweb.asm.Label();
                if(isLiveType) {
                    final LocalVariableDef newDef = new LocalVariableDef(here, type);
                    localVariableDefs.put(symbol, newDef);
                }
                method.visitLabel(here);
                if(existingDef != null) {
                    endLocalValueDef(symbol, existingDef, here);
                }
            }
            if(isLiveType) {
                final int slot = symbol.getSlot(type);
                debug("store symbol", symbol.getName(), " type=", type, " slot=", slot);
                storeHidden(type, slot, onlySymbolLiveValue);
            } else {
                if(onlySymbolLiveValue) {
                    markDeadLocalVariable(symbol);
                }
                debug("dead store symbol ", symbol.getName(), " type=", type);
                pop();
            }
        } else if (symbol.isParam()) {
            assert !symbol.isScope();
            assert functionNode.isVarArg() : "Non-vararg functions have slotted parameters";
            final int index = symbol.getFieldIndex();
            if (functionNode.needsArguments()) {
                convert(Type.OBJECT);
                debug("store symbol", symbol.getName(), " arguments index=", index);
                loadCompilerConstant(ARGUMENTS);
                load(index);
                ArgumentSetter.SET_ARGUMENT.invoke(this);
            } else {
                convert(Type.OBJECT);
                // varargs without arguments object - just do array store to __varargs__
                debug("store symbol", symbol.getName(), " array index=", index);
                loadCompilerConstant(VARARGS);
                load(index);
                ArgumentSetter.SET_ARRAY_ELEMENT.invoke(this);
            }
        } else {
            debug("dead store symbol ", symbol.getName(), " type=", type);
            pop();
        }
    }

    /**
     * Pop a value from the stack and store it in a local variable slot. Note that in contrast with
     * {@link #store(Symbol, Type)}, this method does not adjust the local variable table, nor marks slots for
     * alternative value types for the symbol as being dead. For that reason, this method is usually not called
     * directly. Notable exceptions are temporary internal locals (e.g. quick store, last-catch-condition, etc.) that
     * are not desired to show up in the local variable table.
     *
     * @param type the type to pop
     * @param slot the slot
     */
    void storeHidden(final Type type, final int slot) {
        storeHidden(type, slot, true);
    }

    void storeHidden(final Type type, final int slot, final boolean onlyLiveSymbolValue) {
        explicitStore(type, slot);
        stack.onLocalStore(type, slot, onlyLiveSymbolValue);
    }

    void storeTemp(final Type type, final int slot) {
        explicitStore(type, slot);
        defineTemporaryLocalVariable(slot, slot + type.getSlots());
        onLocalStore(type, slot);
    }

    void onLocalStore(final Type type, final int slot) {
        stack.onLocalStore(type, slot, true);
    }

    private void explicitStore(final Type type, final int slot) {
        assert slot != -1;
        debug("explicit store", type, slot);
        popType(type);
        type.store(method, slot);
    }

    /**
     * Marks a range of slots as belonging to a defined local variable. The slots will start out with no live value
     * in them.
     * @param fromSlot first slot, inclusive.
     * @param toSlot last slot, exclusive.
     */
    void defineBlockLocalVariable(final int fromSlot, final int toSlot) {
        stack.defineBlockLocalVariable(fromSlot, toSlot);
    }

    /**
     * Marks a range of slots as belonging to a defined temporary local variable. The slots will start out with no
     * live value in them.
     * @param fromSlot first slot, inclusive.
     * @param toSlot last slot, exclusive.
     */
    void defineTemporaryLocalVariable(final int fromSlot, final int toSlot) {
        stack.defineTemporaryLocalVariable(fromSlot, toSlot);
    }

    /**
     * Defines a new temporary local variable and returns its allocated index.
     * @param width the required width (in slots) for the new variable.
     * @return the bytecode slot index where the newly allocated local begins.
     */
    int defineTemporaryLocalVariable(final int width) {
        return stack.defineTemporaryLocalVariable(width);
    }

    void undefineLocalVariables(final int fromSlot, final boolean canTruncateSymbol) {
        if(isReachable()) {
            stack.undefineLocalVariables(fromSlot, canTruncateSymbol);
        }
    }

    List<Type> getLocalVariableTypes() {
        return stack.localVariableTypes;
    }

    List<Type> getWidestLiveLocals(final List<Type> localTypes) {
        return stack.getWidestLiveLocals(localTypes);
    }

    String markSymbolBoundariesInLvarTypesDescriptor(final String lvarDescriptor) {
        return stack.markSymbolBoundariesInLvarTypesDescriptor(lvarDescriptor);
    }

    /**
     * Increment/Decrement a local integer by the given value.
     *
     * @param slot the int slot
     * @param increment the amount to increment
     */
    void iinc(final int slot, final int increment) {
        debug("iinc");
        method.visitIincInsn(slot, increment);
    }

    /**
     * Pop an exception object from the stack and generate code
     * for throwing it
     */
    public void athrow() {
        debug("athrow");
        final Type receiver = popType(Type.OBJECT);
        assert Throwable.class.isAssignableFrom(receiver.getTypeClass()) : receiver.getTypeClass();
        method.visitInsn(ATHROW);
        doesNotContinueSequentially();
    }

    /**
     * Pop an object from the stack and perform an instanceof
     * operation, given a classDescriptor to compare it to.
     * Push the boolean result 1/0 as an int to the stack
     *
     * @param classDescriptor descriptor of the class to type check against
     *
     * @return the method emitter
     */
    MethodEmitter _instanceof(final String classDescriptor) {
        debug("instanceof", classDescriptor);
        popType(Type.OBJECT);
        method.visitTypeInsn(INSTANCEOF, classDescriptor);
        pushType(Type.INT);
        return this;
    }

    /**
     * Pop an object from the stack and perform an instanceof
     * operation, given a classDescriptor to compare it to.
     * Push the boolean result 1/0 as an int to the stack
     *
     * @param clazz the type to check instanceof against
     *
     * @return the method emitter
     */
    MethodEmitter _instanceof(final Class<?> clazz) {
        return _instanceof(CompilerConstants.className(clazz));
    }

    /**
     * Perform a checkcast operation on the object at the top of the
     * stack.
     *
     * @param classDescriptor descriptor of the class to type check against
     *
     * @return the method emitter
     */
    MethodEmitter checkcast(final String classDescriptor) {
        debug("checkcast", classDescriptor);
        assert peekType().isObject();
        method.visitTypeInsn(CHECKCAST, classDescriptor);
        return this;
    }

    /**
     * Perform a checkcast operation on the object at the top of the
     * stack.
     *
     * @param clazz class to checkcast against
     *
     * @return the method emitter
     */
    MethodEmitter checkcast(final Class<?> clazz) {
        return checkcast(CompilerConstants.className(clazz));
    }

    /**
     * Instantiate a new array given a length that is popped
     * from the stack and the array type
     *
     * @param arrayType the type of the array
     *
     * @return the method emitter
     */
    MethodEmitter newarray(final ArrayType arrayType) {
        debug("newarray ", "arrayType=", arrayType);
        popType(Type.INT); //LENGTH
        pushType(arrayType.newarray(method));
        return this;
    }

    /**
     * Instantiate a multidimensional array with a given number of dimensions.
     * On the stack are dim lengths of the sub arrays.
     *
     * @param arrayType type of the array
     * @param dims      number of dimensions
     *
     * @return the method emitter
     */
    MethodEmitter multinewarray(final ArrayType arrayType, final int dims) {
        debug("multianewarray ", arrayType, dims);
        for (int i = 0; i < dims; i++) {
            popType(Type.INT); //LENGTH
        }
        pushType(arrayType.newarray(method, dims));
        return this;
    }

    /**
     * Helper function to pop and type check the appropriate arguments
     * from the stack given a method signature
     *
     * @param signature method signature
     *
     * @return return type of method
     */
    private Type fixParamStack(final String signature) {
        final Type[] params = Type.getMethodArguments(signature);
        for (int i = params.length - 1; i >= 0; i--) {
            popType(params[i]);
        }
        final Type returnType = Type.getMethodReturnType(signature);
        return returnType;
    }

    /**
     * Generate an invocation to a Call structure
     * @see CompilerConstants
     *
     * @param call the call object
     *
     * @return the method emitter
     */
    MethodEmitter invoke(final Call call) {
        return call.invoke(this);
    }

    private MethodEmitter invoke(final int opcode, final String className, final String methodName, final String methodDescriptor, final boolean hasReceiver) {
        final Type returnType = fixParamStack(methodDescriptor);

        if (hasReceiver) {
            popType(Type.OBJECT);
        }

        method.visitMethodInsn(opcode, className, methodName, methodDescriptor, opcode == INVOKEINTERFACE);

        if (returnType != null) {
            pushType(returnType);
        }

        return this;
    }

    /**
     * Pop receiver from stack, perform an invoke special
     *
     * @param className        class name
     * @param methodName       method name
     * @param methodDescriptor descriptor
     *
     * @return the method emitter
     */
    MethodEmitter invokespecial(final String className, final String methodName, final String methodDescriptor) {
        debug("invokespecial", className, ".", methodName, methodDescriptor);
        return invoke(INVOKESPECIAL, className, methodName, methodDescriptor, true);
    }

    /**
     * Pop receiver from stack, perform an invoke virtual, push return value if any
     *
     * @param className        class name
     * @param methodName       method name
     * @param methodDescriptor descriptor
     *
     * @return the method emitter
     */
    MethodEmitter invokevirtual(final String className, final String methodName, final String methodDescriptor) {
        debug("invokevirtual", className, ".", methodName, methodDescriptor, " ", stack);
        return invoke(INVOKEVIRTUAL, className, methodName, methodDescriptor, true);
    }

    /**
     * Perform an invoke static and push the return value if any
     *
     * @param className        class name
     * @param methodName       method name
     * @param methodDescriptor descriptor
     *
     * @return the method emitter
     */
    MethodEmitter invokestatic(final String className, final String methodName, final String methodDescriptor) {
        debug("invokestatic", className, ".", methodName, methodDescriptor);
        invoke(INVOKESTATIC, className, methodName, methodDescriptor, false);
        return this;
    }

    /**
     * Perform an invoke static and replace the return type if we know better, e.g. Global.allocate
     * that allocates an array should return an ObjectArray type as a NativeArray counts as that
     *
     * @param className        class name
     * @param methodName       method name
     * @param methodDescriptor descriptor
     * @param returnType       return type override
     *
     * @return the method emitter
     */
    MethodEmitter invokestatic(final String className, final String methodName, final String methodDescriptor, final Type returnType) {
        invokestatic(className, methodName, methodDescriptor);
        popType();
        pushType(returnType);
        return this;
    }

    /**
     * Pop receiver from stack, perform an invoke interface and push return value if any
     *
     * @param className        class name
     * @param methodName       method name
     * @param methodDescriptor descriptor
     *
     * @return the method emitter
     */
    MethodEmitter invokeinterface(final String className, final String methodName, final String methodDescriptor) {
        debug("invokeinterface", className, ".", methodName, methodDescriptor);
        return invoke(INVOKEINTERFACE, className, methodName, methodDescriptor, true);
    }

    static jdk.internal.org.objectweb.asm.Label[] getLabels(final Label... table) {
        final jdk.internal.org.objectweb.asm.Label[] internalLabels = new jdk.internal.org.objectweb.asm.Label[table.length];
        for (int i = 0; i < table.length; i++) {
            internalLabels[i] = table[i].getLabel();
        }
        return internalLabels;
    }

    /**
     * Generate a lookup switch, popping the switch value from the stack
     *
     * @param defaultLabel default label
     * @param values       case values for the table
     * @param table        default label
     */
    void lookupswitch(final Label defaultLabel, final int[] values, final Label... table) {//Collection<Label> table) {
        debug("lookupswitch", peekType());
        adjustStackForSwitch(defaultLabel, table);
        method.visitLookupSwitchInsn(defaultLabel.getLabel(), values, getLabels(table));
        doesNotContinueSequentially();
    }

    /**
     * Generate a table switch
     * @param lo            low value
     * @param hi            high value
     * @param defaultLabel  default label
     * @param table         label table
     */
    void tableswitch(final int lo, final int hi, final Label defaultLabel, final Label... table) {
        debug("tableswitch", peekType());
        adjustStackForSwitch(defaultLabel, table);
        method.visitTableSwitchInsn(lo, hi, defaultLabel.getLabel(), getLabels(table));
        doesNotContinueSequentially();
    }

    private void adjustStackForSwitch(final Label defaultLabel, final Label... table) {
        popType(Type.INT);
        joinTo(defaultLabel);
        for(final Label label: table) {
            joinTo(label);
        }
    }

    /**
     * Abstraction for performing a conditional jump of any type
     *
     * @see Condition
     *
     * @param cond      the condition to test
     * @param trueLabel the destination label is condition is true
     */
    void conditionalJump(final Condition cond, final Label trueLabel) {
        conditionalJump(cond, cond != Condition.GT && cond != Condition.GE, trueLabel);
    }

    /**
     * Abstraction for performing a conditional jump of any type,
     * including a dcmpg/dcmpl semantic for doubles.
     *
     * @param cond      the condition to test
     * @param isCmpG    is this a dcmpg for numbers, false if it's a dcmpl
     * @param trueLabel the destination label if condition is true
     */
    void conditionalJump(final Condition cond, final boolean isCmpG, final Label trueLabel) {
        if (peekType().isCategory2()) {
            debug("[ld]cmp isCmpG=", isCmpG);
            pushType(get2n().cmp(method, isCmpG));
            jump(Condition.toUnary(cond), trueLabel, 1);
        } else {
            debug("if", cond);
            jump(Condition.toBinary(cond, peekType().isObject()), trueLabel, 2);
        }
    }

    /**
     * Perform a non void return, popping the type from the stack
     *
     * @param type the type for the return
     */
    void _return(final Type type) {
        debug("return", type);
        assert stack.size() == 1 : "Only return value on stack allowed at return point - depth=" + stack.size() + " stack = " + stack;
        final Type stackType = peekType();
        if (!Type.areEquivalent(type, stackType)) {
            convert(type);
        }
        popType(type)._return(method);
        doesNotContinueSequentially();
    }

    /**
     * Perform a return using the stack top value as the guide for the type
     */
    void _return() {
        _return(peekType());
    }

    /**
     * Perform a void return.
     */
    void returnVoid() {
        debug("return [void]");
        assert stack.isEmpty() : stack;
        method.visitInsn(RETURN);
        doesNotContinueSequentially();
    }

    /**
     * Perform a comparison of two number types that are popped from the stack
     *
     * @param isCmpG is this a dcmpg semantic, false if it's a dcmpl semantic
     *
     * @return the method emitter
     */
    MethodEmitter cmp(final boolean isCmpG) {
        pushType(get2n().cmp(method, isCmpG));
        return this;
    }

    /**
     * Helper function for jumps, conditional or not
     * @param opcode  opcode for jump
     * @param label   destination
     * @param n       elements on stack to compare, 0-2
     */
    private void jump(final int opcode, final Label label, final int n) {
        for (int i = 0; i < n; i++) {
            assert peekType().isInteger() || peekType().isBoolean() || peekType().isObject() : "expecting integer type or object for jump, but found " + peekType();
            popType();
        }
        joinTo(label);
        method.visitJumpInsn(opcode, label.getLabel());
    }

    /**
     * Generate an if_acmpeq
     *
     * @param label label to true case
     */
    void if_acmpeq(final Label label) {
        debug("if_acmpeq", label);
        jump(IF_ACMPEQ, label, 2);
    }

    /**
     * Generate an if_acmpne
     *
     * @param label label to true case
     */
    void if_acmpne(final Label label) {
        debug("if_acmpne", label);
        jump(IF_ACMPNE, label, 2);
    }

    /**
     * Generate an ifnull
     *
     * @param label label to true case
     */
    void ifnull(final Label label) {
        debug("ifnull", label);
        jump(IFNULL, label, 1);
    }

    /**
     * Generate an ifnonnull
     *
     * @param label label to true case
     */
    void ifnonnull(final Label label) {
        debug("ifnonnull", label);
        jump(IFNONNULL, label, 1);
    }

    /**
     * Generate an ifeq
     *
     * @param label label to true case
     */
    void ifeq(final Label label) {
        debug("ifeq ", label);
        jump(IFEQ, label, 1);
    }

    /**
     * Generate an if_icmpeq
     *
     * @param label label to true case
     */
    void if_icmpeq(final Label label) {
        debug("if_icmpeq", label);
        jump(IF_ICMPEQ, label, 2);
    }

    /**
     * Generate an if_ne
     *
     * @param label label to true case
     */
    void ifne(final Label label) {
        debug("ifne", label);
        jump(IFNE, label, 1);
    }

    /**
     * Generate an if_icmpne
     *
     * @param label label to true case
     */
    void if_icmpne(final Label label) {
        debug("if_icmpne", label);
        jump(IF_ICMPNE, label, 2);
    }

    /**
     * Generate an iflt
     *
     * @param label label to true case
     */
    void iflt(final Label label) {
        debug("iflt", label);
        jump(IFLT, label, 1);
    }

    /**
     * Generate an if_icmplt
     *
     * @param label label to true case
     */
    void if_icmplt(final Label label) {
        debug("if_icmplt", label);
        jump(IF_ICMPLT, label, 2);
    }

    /**
     * Generate an ifle
     *
     * @param label label to true case
     */
    void ifle(final Label label) {
        debug("ifle", label);
        jump(IFLE, label, 1);
    }

    /**
     * Generate an if_icmple
     *
     * @param label label to true case
     */
    void if_icmple(final Label label) {
        debug("if_icmple", label);
        jump(IF_ICMPLE, label, 2);
    }

    /**
     * Generate an ifgt
     *
     * @param label label to true case
     */
    void ifgt(final Label label) {
        debug("ifgt", label);
        jump(IFGT, label, 1);
    }

    /**
     * Generate an if_icmpgt
     *
     * @param label label to true case
     */
    void if_icmpgt(final Label label) {
        debug("if_icmpgt", label);
        jump(IF_ICMPGT, label, 2);
    }

    /**
     * Generate an ifge
     *
     * @param label label to true case
     */
    void ifge(final Label label) {
        debug("ifge", label);
        jump(IFGE, label, 1);
    }

    /**
     * Generate an if_icmpge
     *
     * @param label label to true case
     */
    void if_icmpge(final Label label) {
        debug("if_icmpge", label);
        jump(IF_ICMPGE, label, 2);
    }

    /**
     * Unconditional jump to a label
     *
     * @param label destination label
     */
    void _goto(final Label label) {
        debug("goto", label);
        jump(GOTO, label, 0);
        doesNotContinueSequentially(); //whoever reaches the point after us provides the stack, because we don't
    }

    /**
     * Unconditional jump to the start label of a loop. It differs from ordinary {@link #_goto(Label)} in that it will
     * preserve the current label stack, as the next instruction after the goto is loop body that the loop will come
     * back to. Also used to jump at the start label of the continuation handler, as it behaves much like a loop test in
     * the sense that after it is evaluated, it also jumps backwards.
     *
     * @param loopStart start label of a loop
     */
    void gotoLoopStart(final Label loopStart) {
        debug("goto (loop)", loopStart);
        jump(GOTO, loopStart, 0);
    }

    /**
     * Unconditional jump without any control flow and data flow testing. You should not normally use this method when
     * generating code, except if you're very sure that you know what you're doing. Normally only used for the
     * admittedly torturous control flow of continuation handler plumbing.
     * @param target the target of the jump
     */
    void uncheckedGoto(final Label target) {
        method.visitJumpInsn(GOTO, target.getLabel());
    }

    /**
     * Potential transfer of control to a catch block.
     *
     * @param catchLabel destination catch label
     */
    void canThrow(final Label catchLabel) {
        catchLabel.joinFromTry(stack, false);
    }

    /**
     * A join in control flow - helper function that makes sure all entry stacks
     * discovered for the join point so far are equivalent
     *
     * MergeStack: we are about to enter a label. If its stack, label.getStack() is null
     * we have never been here before. Then we are expected to carry a stack with us.
     *
     * @param label label
     */
    private void joinTo(final Label label) {
        assert isReachable();
        label.joinFrom(stack);
    }

    /**
     * Register a new label, enter it here.
     * @param label
     */
    void label(final Label label) {
        breakLabel(label, -1);
    }

    /**
     * Register a new break target label, enter it here.
     *
     * @param label the label
     * @param liveLocals the number of live locals at this label
     */
    void breakLabel(final Label label, final int liveLocals) {
        if (!isReachable()) {
            // If we emit a label, and the label's stack is null, it must not be reachable.
            assert (label.getStack() == null) != label.isReachable();
        } else {
            joinTo(label);
        }
        // Use label's stack as we might have no stack.
        final Label.Stack labelStack = label.getStack();
        stack = labelStack == null ? null : labelStack.clone();
        if(stack != null && label.isBreakTarget() && liveLocals != -1) {
            // This has to be done because we might not have another frame to provide us with its firstTemp if the label
            // is only reachable through a break or continue statement; also in this case, the frame can actually
            // give us a higher number of live locals, e.g. if it comes from a catch. Typical example:
            // for(;;) { try{ throw 0; } catch(e) { break; } }.
            // Since the for loop can only be exited through the break in the catch block, it'll bring with it the
            // "e" as a live local, and we need to trim it off here.
            assert stack.firstTemp >= liveLocals;
            stack.firstTemp = liveLocals;
        }
        debug_label(label);
        method.visitLabel(label.getLabel());
    }

    /**
     * Pop element from stack, convert to given type
     *
     * @param to type to convert to
     *
     * @return the method emitter
     */
    MethodEmitter convert(final Type to) {
        final Type from = peekType();
        final Type type = from.convert(method, to);
        if (type != null) {
            if (!from.isEquivalentTo(to)) {
                debug("convert", from, "->", to);
            }
            if (type != from) {
                final int l0 = stack.getTopLocalLoad();
                popType();
                pushType(type);
                // NOTE: conversions from a primitive type are considered to preserve the "load" property of the value
                // on the stack. Otherwise we could introduce temporary locals in a deoptimized rest-of (e.g. doing an
                // "i < x.length" where "i" is int and ".length" gets deoptimized to long would end up converting i to
                // long with "ILOAD i; I2L; LSTORE tmp; LLOAD tmp;"). Such additional temporary would cause an error
                // when restoring the state of the function for rest-of execution, as the not-yet deoptimized variant
                // would have the (now invalidated) assumption that "x.length" is an int, so it wouldn't have the I2L,
                // and therefore neither the subsequent LSTORE tmp; LLOAD tmp;. By making sure conversions from a
                // primitive type don't erase the "load" information, we don't introduce temporaries in the deoptimized
                // rest-of that didn't exist in the more optimistic version that triggered the deoptimization.
                // NOTE: as a more general observation, we could theoretically track the operations required to
                // reproduce any stack value as long as they are all local loads, constant loads, and stack operations.
                // We won't go there in the current system
                if(!from.isObject()) {
                    stack.markLocalLoad(l0);
                }
            }
        }
        return this;
    }

    /**
     * Helper function - expect two types that are equivalent
     *
     * @return common type
     */
    private Type get2() {
        final Type p0 = popType();
        final Type p1 = popType();
        assert p0.isEquivalentTo(p1) : "expecting equivalent types on stack but got " + p0 + " and " + p1;
        return p0;
    }

    /**
     * Helper function - expect two types that are integer types and equivalent
     *
     * @return common type
     */
    private BitwiseType get2i() {
        final BitwiseType p0 = popBitwise();
        final BitwiseType p1 = popBitwise();
        assert p0.isEquivalentTo(p1) : "expecting equivalent types on stack but got " + p0 + " and " + p1;
        return p0;
    }

    /**
     * Helper function - expect two types that are numbers and equivalent
     *
     * @return common type
     */
    private NumericType get2n() {
        final NumericType p0 = popNumeric();
        final NumericType p1 = popNumeric();
        assert p0.isEquivalentTo(p1) : "expecting equivalent types on stack but got " + p0 + " and " + p1;
        return p0;
    }

    /**
     * Pop two numbers, perform addition and push result
     *
     * @return the method emitter
     */
    MethodEmitter add(final int programPoint) {
        debug("add");
        pushType(get2().add(method, programPoint));
        return this;
    }

    /**
     * Pop two numbers, perform subtraction and push result
     *
     * @return the method emitter
     */
    MethodEmitter sub(final int programPoint) {
        debug("sub");
        pushType(get2n().sub(method, programPoint));
        return this;
    }

    /**
     * Pop two numbers, perform multiplication and push result
     *
     * @return the method emitter
     */
    MethodEmitter mul(final int programPoint) {
        debug("mul ");
        pushType(get2n().mul(method, programPoint));
        return this;
    }

    /**
     * Pop two numbers, perform division and push result
     *
     * @return the method emitter
     */
    MethodEmitter div(final int programPoint) {
        debug("div");
        pushType(get2n().div(method, programPoint));
        return this;
    }

    /**
     * Pop two numbers, calculate remainder and push result
     *
     * @return the method emitter
     */
    MethodEmitter rem(final int programPoint) {
        debug("rem");
        pushType(get2n().rem(method, programPoint));
        return this;
    }

    /**
     * Retrieve the top <tt>count</tt> types on the stack without modifying it.
     *
     * @param count number of types to return
     * @return array of Types
     */
    protected Type[] getTypesFromStack(final int count) {
        return stack.getTopTypes(count);
    }

    int[] getLocalLoadsOnStack(final int from, final int to) {
        return stack.getLocalLoads(from, to);
    }

    int getStackSize() {
        return stack.size();
    }

    int getFirstTemp() {
        return stack.firstTemp;
    }

    int getUsedSlotsWithLiveTemporaries() {
        return stack.getUsedSlotsWithLiveTemporaries();
    }

    /**
     * Helper function to generate a function signature based on stack contents
     * and argument count and return type
     *
     * @param returnType return type
     * @param argCount   argument count
     *
     * @return function signature for stack contents
     */
    private String getDynamicSignature(final Type returnType, final int argCount) {
        final Type[]         paramTypes = new Type[argCount];

        int pos = 0;
        for (int i = argCount - 1; i >= 0; i--) {
            Type pt = stack.peek(pos++);
            // "erase" specific ScriptObject subtype info - except for NativeArray.
            // NativeArray is used for array/List/Deque conversion for Java calls.
            if (ScriptObject.class.isAssignableFrom(pt.getTypeClass()) &&
                !NativeArray.class.isAssignableFrom(pt.getTypeClass())) {
                pt = Type.SCRIPT_OBJECT;
            }
            paramTypes[i] = pt;
        }
        final String descriptor = Type.getMethodDescriptor(returnType, paramTypes);
        for (int i = 0; i < argCount; i++) {
            popType(paramTypes[argCount - i - 1]);
        }

        return descriptor;
    }

    MethodEmitter invalidateSpecialName(final String name) {
        switch (name) {
        case "apply":
        case "call":
            debug("invalidate_name", "name=", name);
            load("Function");
            invoke(ScriptRuntime.INVALIDATE_RESERVED_BUILTIN_NAME);
            break;
        default:
            break;
        }
        return this;
    }

    /**
     * Generate a dynamic new
     *
     * @param argCount  number of arguments
     * @param flags     callsite flags
     *
     * @return the method emitter
     */
    MethodEmitter dynamicNew(final int argCount, final int flags) {
        return dynamicNew(argCount, flags, null);
    }

    /**
     * Generate a dynamic new
     *
     * @param argCount  number of arguments
     * @param flags     callsite flags
     * @param msg        additional message to be used when reporting error
     *
     * @return the method emitter
     */
    MethodEmitter dynamicNew(final int argCount, final int flags, final String msg) {
        assert !isOptimistic(flags);
        debug("dynamic_new", "argcount=", argCount);
        final String signature = getDynamicSignature(Type.OBJECT, argCount);
        method.visitInvokeDynamicInsn(
                msg != null && msg.length() < LARGE_STRING_THRESHOLD? "dyn:new:" + NameCodec.encode(msg) : "dyn:new",
                signature, LINKERBOOTSTRAP, flags);
        pushType(Type.OBJECT); //TODO fix result type
        return this;
    }

    /**
     * Generate a dynamic call
     *
     * @param returnType return type
     * @param argCount   number of arguments
     * @param flags      callsite flags
     *
     * @return the method emitter
     */
    MethodEmitter dynamicCall(final Type returnType, final int argCount, final int flags) {
        return dynamicCall(returnType, argCount, flags, null);
    }

    /**
     * Generate a dynamic call
     *
     * @param returnType return type
     * @param argCount   number of arguments
     * @param flags      callsite flags
     * @param msg        additional message to be used when reporting error
     *
     * @return the method emitter
     */
    MethodEmitter dynamicCall(final Type returnType, final int argCount, final int flags, final String msg) {
        debug("dynamic_call", "args=", argCount, "returnType=", returnType);
        final String signature = getDynamicSignature(returnType, argCount); // +1 because the function itself is the 1st parameter for dynamic calls (what you call - call target)
        debug("   signature", signature);
        method.visitInvokeDynamicInsn(
                msg != null && msg.length() < LARGE_STRING_THRESHOLD? "dyn:call:" + NameCodec.encode(msg) : "dyn:call",
                signature, LINKERBOOTSTRAP, flags);
        pushType(returnType);

        return this;
    }

    MethodEmitter dynamicArrayPopulatorCall(final int argCount, final int startIndex) {
        debug("populate_array", "args=", argCount, "startIndex=", startIndex);
        final String signature = getDynamicSignature(Type.OBJECT_ARRAY, argCount);
        method.visitInvokeDynamicInsn("populateArray", signature, POPULATE_ARRAY_BOOTSTRAP, startIndex);
        pushType(Type.OBJECT_ARRAY);
        return this;
    }

    /**
     * Generate dynamic getter. Pop scope from stack. Push result
     *
     * @param valueType type of the value to set
     * @param name      name of property
     * @param flags     call site flags
     * @param isMethod  should it prefer retrieving methods
     * @param isIndex   is this an index operation?
     * @return the method emitter
     */
    MethodEmitter dynamicGet(final Type valueType, final String name, final int flags, final boolean isMethod, final boolean isIndex) {
        if (name.length() > LARGE_STRING_THRESHOLD) { // use getIndex for extremely long names
            return load(name).dynamicGetIndex(valueType, flags, isMethod);
        }

        debug("dynamic_get", name, valueType, getProgramPoint(flags));

        Type type = valueType;
        if (type.isObject() || type.isBoolean()) {
            type = Type.OBJECT; //promote e.g strings to object generic setter
        }

        popType(Type.SCOPE);
        method.visitInvokeDynamicInsn(dynGetOperation(isMethod, isIndex) + ':' + NameCodec.encode(name),
                Type.getMethodDescriptor(type, Type.OBJECT), LINKERBOOTSTRAP, flags);

        pushType(type);
        convert(valueType); //most probably a nop

        return this;
    }

    /**
     * Generate dynamic setter. Pop receiver and property from stack.
     *
     * @param name  name of property
     * @param flags call site flags
     * @param isIndex is this an index operation?
     */
    void dynamicSet(final String name, final int flags, final boolean isIndex) {
        if (name.length() > LARGE_STRING_THRESHOLD) { // use setIndex for extremely long names
            load(name).swap().dynamicSetIndex(flags);
            return;
        }

        assert !isOptimistic(flags);
        debug("dynamic_set", name, peekType());

        Type type = peekType();
        if (type.isObject() || type.isBoolean()) { //promote strings to objects etc
            type = Type.OBJECT;
            convert(Type.OBJECT); //TODO bad- until we specialize boolean setters,
        }
        popType(type);
        popType(Type.SCOPE);

        method.visitInvokeDynamicInsn(dynSetOperation(isIndex) + ':' + NameCodec.encode(name),
                methodDescriptor(void.class, Object.class, type.getTypeClass()), LINKERBOOTSTRAP, flags);
    }

     /**
     * Dynamic getter for indexed structures. Pop index and receiver from stack,
     * generate appropriate signatures based on types
     *
     * @param result result type for getter
     * @param flags call site flags for getter
     * @param isMethod should it prefer retrieving methods
     *
     * @return the method emitter
     */
    MethodEmitter dynamicGetIndex(final Type result, final int flags, final boolean isMethod) {
        assert result.getTypeClass().isPrimitive() || result.getTypeClass() == Object.class;
        debug("dynamic_get_index", peekType(1), "[", peekType(), "]", getProgramPoint(flags));

        Type resultType = result;
        if (result.isBoolean()) {
            resultType = Type.OBJECT; // INT->OBJECT to avoid another dimension of cross products in the getters. TODO
        }

        Type index = peekType();
        if (index.isObject() || index.isBoolean()) {
            index = Type.OBJECT; //e.g. string->object
            convert(Type.OBJECT);
        }
        popType();

        popType(Type.OBJECT);

        final String signature = Type.getMethodDescriptor(resultType, Type.OBJECT /*e.g STRING->OBJECT*/, index);

        method.visitInvokeDynamicInsn(dynGetOperation(isMethod, true), signature, LINKERBOOTSTRAP, flags);
        pushType(resultType);

        if (result.isBoolean()) {
            convert(Type.BOOLEAN);
        }

        return this;
    }

    private static String getProgramPoint(final int flags) {
        if((flags & CALLSITE_OPTIMISTIC) == 0) {
            return "";
        }
        return "pp=" + String.valueOf((flags & (-1 << CALLSITE_PROGRAM_POINT_SHIFT)) >> CALLSITE_PROGRAM_POINT_SHIFT);
    }

    /**
     * Dynamic setter for indexed structures. Pop value, index and receiver from
     * stack, generate appropriate signature based on types
     *
     * @param flags call site flags for setter
     */
    void dynamicSetIndex(final int flags) {
        assert !isOptimistic(flags);
        debug("dynamic_set_index", peekType(2), "[", peekType(1), "] =", peekType());

        Type value = peekType();
        if (value.isObject() || value.isBoolean()) {
            value = Type.OBJECT; //e.g. STRING->OBJECT - one descriptor for all object types
            convert(Type.OBJECT);
        }
        popType();

        Type index = peekType();
        if (index.isObject() || index.isBoolean()) {
            index = Type.OBJECT; //e.g. string->object
            convert(Type.OBJECT);
        }
        popType(index);

        final Type receiver = popType(Type.OBJECT);
        assert receiver.isObject();

        method.visitInvokeDynamicInsn("dyn:setElem|setProp", methodDescriptor(void.class, receiver.getTypeClass(), index.getTypeClass(), value.getTypeClass()), LINKERBOOTSTRAP, flags);
    }

    /**
     * Load a key value in the proper form.
     *
     * @param key
     */
    //TODO move this and break it apart
    MethodEmitter loadKey(final Object key) {
        if (key instanceof IdentNode) {
            method.visitLdcInsn(((IdentNode) key).getName());
        } else if (key instanceof LiteralNode) {
            method.visitLdcInsn(((LiteralNode<?>)key).getString());
        } else {
            method.visitLdcInsn(JSType.toString(key));
        }
        pushType(Type.OBJECT); //STRING
        return this;
    }

     @SuppressWarnings("fallthrough")
     private static Type fieldType(final String desc) {
         switch (desc) {
         case "Z":
         case "B":
         case "C":
         case "S":
         case "I":
             return Type.INT;
         case "F":
             assert false;
         case "D":
             return Type.NUMBER;
         case "J":
             return Type.LONG;
         default:
             assert desc.startsWith("[") || desc.startsWith("L") : desc + " is not an object type";
             switch (desc.charAt(0)) {
             case 'L':
                 return Type.OBJECT;
             case '[':
                 return Type.typeFor(Array.newInstance(fieldType(desc.substring(1)).getTypeClass(), 0).getClass());
             default:
                 assert false;
             }
             return Type.OBJECT;
         }
     }

     /**
      * Generate get for a field access
      *
      * @param fa the field access
      *
      * @return the method emitter
      */
    MethodEmitter getField(final FieldAccess fa) {
        return fa.get(this);
    }

     /**
      * Generate set for a field access
      *
      * @param fa the field access
      */
    void putField(final FieldAccess fa) {
        fa.put(this);
    }

    /**
     * Get the value of a non-static field, pop the receiver from the stack,
     * push value to the stack
     *
     * @param className        class
     * @param fieldName        field name
     * @param fieldDescriptor  field descriptor
     *
     * @return the method emitter
     */
    MethodEmitter getField(final String className, final String fieldName, final String fieldDescriptor) {
        debug("getfield", "receiver=", peekType(), className, ".", fieldName, fieldDescriptor);
        final Type receiver = popType();
        assert receiver.isObject();
        method.visitFieldInsn(GETFIELD, className, fieldName, fieldDescriptor);
        pushType(fieldType(fieldDescriptor));
        return this;
    }

    /**
     * Get the value of a static field, push it to the stack
     *
     * @param className        class
     * @param fieldName        field name
     * @param fieldDescriptor  field descriptor
     *
     * @return the method emitter
     */
    MethodEmitter getStatic(final String className, final String fieldName, final String fieldDescriptor) {
        debug("getstatic", className, ".", fieldName, ".", fieldDescriptor);
        method.visitFieldInsn(GETSTATIC, className, fieldName, fieldDescriptor);
        pushType(fieldType(fieldDescriptor));
        return this;
    }

    /**
     * Pop value and field from stack and write to a non-static field
     *
     * @param className       class
     * @param fieldName       field name
     * @param fieldDescriptor field descriptor
     */
    void putField(final String className, final String fieldName, final String fieldDescriptor) {
        debug("putfield", "receiver=", peekType(1), "value=", peekType());
        popType(fieldType(fieldDescriptor));
        popType(Type.OBJECT);
        method.visitFieldInsn(PUTFIELD, className, fieldName, fieldDescriptor);
    }

    /**
     * Pop value from stack and write to a static field
     *
     * @param className       class
     * @param fieldName       field name
     * @param fieldDescriptor field descriptor
     */
    void putStatic(final String className, final String fieldName, final String fieldDescriptor) {
        debug("putfield", "value=", peekType());
        popType(fieldType(fieldDescriptor));
        method.visitFieldInsn(PUTSTATIC, className, fieldName, fieldDescriptor);
    }

    /**
     * Register line number at a label
     *
     * @param line  line number
     */
    void lineNumber(final int line) {
        if (context.getEnv()._debug_lines) {
            debug_label("[LINE]", line);
            final jdk.internal.org.objectweb.asm.Label l = new jdk.internal.org.objectweb.asm.Label();
            method.visitLabel(l);
            method.visitLineNumber(line, l);
        }
    }

    void beforeJoinPoint(final JoinPredecessor joinPredecessor) {
        LocalVariableConversion next = joinPredecessor.getLocalVariableConversion();
        while(next != null) {
            final Symbol symbol = next.getSymbol();
            if(next.isLive()) {
                emitLocalVariableConversion(next, true);
            } else {
                markDeadLocalVariable(symbol);
            }
            next = next.getNext();
        }
    }

    void beforeTry(final TryNode tryNode, final Label recovery) {
        LocalVariableConversion next = tryNode.getLocalVariableConversion();
        while(next != null) {
            if(next.isLive()) {
                final Type to = emitLocalVariableConversion(next, false);
                recovery.getStack().onLocalStore(to, next.getSymbol().getSlot(to), true);
            }
            next = next.getNext();
        }
    }

    private static String dynGetOperation(final boolean isMethod, final boolean isIndex) {
        if (isMethod) {
            return isIndex ? "dyn:getMethod|getElem|getProp" : "dyn:getMethod|getProp|getElem";
        } else {
            return isIndex ? "dyn:getElem|getProp|getMethod" : "dyn:getProp|getElem|getMethod";
        }
    }

    private static String dynSetOperation(final boolean isIndex) {
        return isIndex ? "dyn:setElem|setProp" : "dyn:setProp|setElem";
    }

    private Type emitLocalVariableConversion(final LocalVariableConversion conversion, final boolean onlySymbolLiveValue) {
        final Type from = conversion.getFrom();
        final Type to = conversion.getTo();
        final Symbol symbol = conversion.getSymbol();
        assert symbol.isBytecodeLocal();
        if(from == Type.UNDEFINED) {
            loadUndefined(to);
        } else {
            load(symbol, from).convert(to);
        }
        store(symbol, to, onlySymbolLiveValue);
        return to;
    }

    /*
     * Debugging below
     */

    private final FieldAccess ERR_STREAM       = staticField(System.class, "err", PrintStream.class);
    private final Call        PRINT            = virtualCallNoLookup(PrintStream.class, "print", void.class, Object.class);
    private final Call        PRINTLN          = virtualCallNoLookup(PrintStream.class, "println", void.class, Object.class);
    private final Call        PRINT_STACKTRACE = virtualCallNoLookup(Throwable.class, "printStackTrace", void.class);

    /**
     * Emit a System.err.print statement of whatever is on top of the bytecode stack
     */
     void print() {
         getField(ERR_STREAM);
         swap();
         convert(Type.OBJECT);
         invoke(PRINT);
     }

    /**
     * Emit a System.err.println statement of whatever is on top of the bytecode stack
     */
     void println() {
         getField(ERR_STREAM);
         swap();
         convert(Type.OBJECT);
         invoke(PRINTLN);
     }

     /**
      * Emit a System.err.print statement
      * @param string string to print
      */
     void print(final String string) {
         getField(ERR_STREAM);
         load(string);
         invoke(PRINT);
     }

     /**
      * Emit a System.err.println statement
      * @param string string to print
      */
     void println(final String string) {
         getField(ERR_STREAM);
         load(string);
         invoke(PRINTLN);
     }

     /**
      * Print a stacktrace to S
      */
     void stacktrace() {
         _new(Throwable.class);
         dup();
         invoke(constructorNoLookup(Throwable.class));
         invoke(PRINT_STACKTRACE);
     }

    private static int linePrefix = 0;

    /**
     * Debug function that outputs generated bytecode and stack contents
     *
     * @param args debug information to print
     */
    @SuppressWarnings("unused")
    private void debug(final Object... args) {
        if (debug) {
            debug(30, args);
        }
    }

    private void debug(final String arg) {
        if (debug) {
            debug(30, arg);
        }
    }

    private void debug(final Object arg0, final Object arg1) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1 });
        }
    }

    private void debug(final Object arg0, final Object arg1, final Object arg2) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1, arg2 });
        }
    }

    private void debug(final Object arg0, final Object arg1, final Object arg2, final Object arg3) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1, arg2, arg3 });
        }
    }

    private void debug(final Object arg0, final Object arg1, final Object arg2, final Object arg3, final Object arg4) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1, arg2, arg3, arg4 });
        }
    }

    private void debug(final Object arg0, final Object arg1, final Object arg2, final Object arg3, final Object arg4, final Object arg5) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1, arg2, arg3, arg4, arg5 });
        }
    }

    private void debug(final Object arg0, final Object arg1, final Object arg2, final Object arg3, final Object arg4, final Object arg5, final Object arg6) {
        if (debug) {
            debug(30, new Object[] { arg0, arg1, arg2, arg3, arg4, arg5, arg6 });
        }
    }

    /**
     * Debug function that outputs generated bytecode and stack contents
     * for a label - indentation is currently the only thing that differs
     *
     * @param args debug information to print
     */
    private void debug_label(final Object... args) {
        if (debug) {
            debug(22, args);
        }
    }

    private void debug(final int padConstant, final Object... args) {
        if (debug) {
            final StringBuilder sb = new StringBuilder();
            int pad;

            sb.append('#');
            sb.append(++linePrefix);

            pad = 5 - sb.length();
            while (pad > 0) {
                sb.append(' ');
                pad--;
            }

            if (isReachable() && !stack.isEmpty()) {
                sb.append("{");
                sb.append(stack.size());
                sb.append(":");
                for (int pos = 0; pos < stack.size(); pos++) {
                    final Type t = stack.peek(pos);

                    if (t == Type.SCOPE) {
                        sb.append("scope");
                    } else if (t == Type.THIS) {
                        sb.append("this");
                    } else if (t.isObject()) {
                        String desc = t.getDescriptor();
                        int i;
                        for (i = 0; desc.charAt(i) == '[' && i < desc.length(); i++) {
                            sb.append('[');
                        }
                        desc = desc.substring(i);
                        final int slash = desc.lastIndexOf('/');
                        if (slash != -1) {
                            desc = desc.substring(slash + 1, desc.length() - 1);
                        }
                        if ("Object".equals(desc)) {
                            sb.append('O');
                        } else {
                            sb.append(desc);
                        }
                    } else {
                        sb.append(t.getDescriptor());
                    }
                    final int loadIndex = stack.localLoads[stack.sp - 1 - pos];
                    if(loadIndex != Label.Stack.NON_LOAD) {
                        sb.append('(').append(loadIndex).append(')');
                    }
                    if (pos + 1 < stack.size()) {
                        sb.append(' ');
                    }
                }
                sb.append('}');
                sb.append(' ');
            }

            pad = padConstant - sb.length();
            while (pad > 0) {
                sb.append(' ');
                pad--;
            }

            for (final Object arg : args) {
                sb.append(arg);
                sb.append(' ');
            }

            if (context.getEnv() != null) { //early bootstrap code doesn't have inited context yet
                log.info(sb);
                if (DEBUG_TRACE_LINE == linePrefix) {
                    new Throwable().printStackTrace(log.getOutputStream());
                }
            }
        }
    }

    /**
     * Set the current function node being emitted
     * @param functionNode the function node
     */
    void setFunctionNode(final FunctionNode functionNode) {
        this.functionNode = functionNode;
    }

    /**
     * Invoke to enforce assertions preventing load from a local variable slot that's known to not have been written to.
     * Used by CodeGenerator, as it strictly enforces tracking of stores. Simpler uses of MethodEmitter, e.g. those
     * for creating initializers for structure  classes, array getters, etc. don't have strict tracking of stores,
     * therefore they would fail if they had this assertion turned on.
     */
    void setPreventUndefinedLoad() {
        this.preventUndefinedLoad = true;
    }

    private static boolean isOptimistic(final int flags) {
        return (flags & CALLSITE_OPTIMISTIC) != 0;
    }
}