asm/commons/GeneratorAdapter.java

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

/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package jdk.internal.org.objectweb.asm.commons;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.ConstantDynamic;
import jdk.internal.org.objectweb.asm.Handle;
import jdk.internal.org.objectweb.asm.Label;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import jdk.internal.org.objectweb.asm.Type;

/**
 * A {@link MethodVisitor} with convenient methods to generate code. For example, using this
 * adapter, the class below
 *
 * <pre>
 * public class Example {
 *   public static void main(String[] args) {
 *     System.out.println(&quot;Hello world!&quot;);
 *   }
 * }
 * </pre>
 *
 * <p>can be generated as follows:
 *
 * <pre>
 * ClassWriter cw = new ClassWriter(0);
 * cw.visit(V1_1, ACC_PUBLIC, &quot;Example&quot;, null, &quot;java/lang/Object&quot;, null);
 *
 * Method m = Method.getMethod(&quot;void &lt;init&gt; ()&quot;);
 * GeneratorAdapter mg = new GeneratorAdapter(ACC_PUBLIC, m, null, null, cw);
 * mg.loadThis();
 * mg.invokeConstructor(Type.getType(Object.class), m);
 * mg.returnValue();
 * mg.endMethod();
 *
 * m = Method.getMethod(&quot;void main (String[])&quot;);
 * mg = new GeneratorAdapter(ACC_PUBLIC + ACC_STATIC, m, null, null, cw);
 * mg.getStatic(Type.getType(System.class), &quot;out&quot;, Type.getType(PrintStream.class));
 * mg.push(&quot;Hello world!&quot;);
 * mg.invokeVirtual(Type.getType(PrintStream.class),
 *         Method.getMethod(&quot;void println (String)&quot;));
 * mg.returnValue();
 * mg.endMethod();
 *
 * cw.visitEnd();
 * </pre>
 *
 * @author Juozas Baliuka
 * @author Chris Nokleberg
 * @author Eric Bruneton
 * @author Prashant Deva
 */
public class GeneratorAdapter extends LocalVariablesSorter {

    private static final String CLASS_DESCRIPTOR = "Ljava/lang/Class;";

    private static final Type BYTE_TYPE = Type.getObjectType("java/lang/Byte");

    private static final Type BOOLEAN_TYPE = Type.getObjectType("java/lang/Boolean");

    private static final Type SHORT_TYPE = Type.getObjectType("java/lang/Short");

    private static final Type CHARACTER_TYPE = Type.getObjectType("java/lang/Character");

    private static final Type INTEGER_TYPE = Type.getObjectType("java/lang/Integer");

    private static final Type FLOAT_TYPE = Type.getObjectType("java/lang/Float");

    private static final Type LONG_TYPE = Type.getObjectType("java/lang/Long");

    private static final Type DOUBLE_TYPE = Type.getObjectType("java/lang/Double");

    private static final Type NUMBER_TYPE = Type.getObjectType("java/lang/Number");

    private static final Type OBJECT_TYPE = Type.getObjectType("java/lang/Object");

    private static final Method BOOLEAN_VALUE = Method.getMethod("boolean booleanValue()");

    private static final Method CHAR_VALUE = Method.getMethod("char charValue()");

    private static final Method INT_VALUE = Method.getMethod("int intValue()");

    private static final Method FLOAT_VALUE = Method.getMethod("float floatValue()");

    private static final Method LONG_VALUE = Method.getMethod("long longValue()");

    private static final Method DOUBLE_VALUE = Method.getMethod("double doubleValue()");

    /** Constant for the {@link #math} method. */
    public static final int ADD = Opcodes.IADD;

    /** Constant for the {@link #math} method. */
    public static final int SUB = Opcodes.ISUB;

    /** Constant for the {@link #math} method. */
    public static final int MUL = Opcodes.IMUL;

    /** Constant for the {@link #math} method. */
    public static final int DIV = Opcodes.IDIV;

    /** Constant for the {@link #math} method. */
    public static final int REM = Opcodes.IREM;

    /** Constant for the {@link #math} method. */
    public static final int NEG = Opcodes.INEG;

    /** Constant for the {@link #math} method. */
    public static final int SHL = Opcodes.ISHL;

    /** Constant for the {@link #math} method. */
    public static final int SHR = Opcodes.ISHR;

    /** Constant for the {@link #math} method. */
    public static final int USHR = Opcodes.IUSHR;

    /** Constant for the {@link #math} method. */
    public static final int AND = Opcodes.IAND;

    /** Constant for the {@link #math} method. */
    public static final int OR = Opcodes.IOR;

    /** Constant for the {@link #math} method. */
    public static final int XOR = Opcodes.IXOR;

    /** Constant for the {@link #ifCmp} method. */
    public static final int EQ = Opcodes.IFEQ;

    /** Constant for the {@link #ifCmp} method. */
    public static final int NE = Opcodes.IFNE;

    /** Constant for the {@link #ifCmp} method. */
    public static final int LT = Opcodes.IFLT;

    /** Constant for the {@link #ifCmp} method. */
    public static final int GE = Opcodes.IFGE;

    /** Constant for the {@link #ifCmp} method. */
    public static final int GT = Opcodes.IFGT;

    /** Constant for the {@link #ifCmp} method. */
    public static final int LE = Opcodes.IFLE;

    /** The access flags of the visited method. */
    private final int access;

    /** The name of the visited method. */
    private final String name;

    /** The return type of the visited method. */
    private final Type returnType;

    /** The argument types of the visited method. */
    private final Type[] argumentTypes;

    /** The types of the local variables of the visited method. */
    private final List<Type> localTypes = new ArrayList<>();

    /**
      * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
      * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
      * version.
      *
      * @param methodVisitor the method visitor to which this adapter delegates calls.
      * @param access the method's access flags (see {@link Opcodes}).
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      * @throws IllegalStateException if a subclass calls this constructor.
      */
    public GeneratorAdapter(
            final MethodVisitor methodVisitor,
            final int access,
            final String name,
            final String descriptor) {
        this(/* latest api = */ Opcodes.ASM8, methodVisitor, access, name, descriptor);
        if (getClass() != GeneratorAdapter.class) {
            throw new IllegalStateException();
        }
    }

    /**
      * Constructs a new {@link GeneratorAdapter}.
      *
      * @param api the ASM API version implemented by this visitor. Must be one of {@link
      *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6}, {@link Opcodes#ASM7} or {@link
      *     Opcodes#ASM8}.
      * @param methodVisitor the method visitor to which this adapter delegates calls.
      * @param access the method's access flags (see {@link Opcodes}).
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      */
    protected GeneratorAdapter(
            final int api,
            final MethodVisitor methodVisitor,
            final int access,
            final String name,
            final String descriptor) {
        super(api, access, descriptor, methodVisitor);
        this.access = access;
        this.name = name;
        this.returnType = Type.getReturnType(descriptor);
        this.argumentTypes = Type.getArgumentTypes(descriptor);
    }

    /**
      * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
      * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
      * version.
      *
      * @param access access flags of the adapted method.
      * @param method the adapted method.
      * @param methodVisitor the method visitor to which this adapter delegates calls.
      */
    public GeneratorAdapter(
            final int access, final Method method, final MethodVisitor methodVisitor) {
        this(methodVisitor, access, method.getName(), method.getDescriptor());
    }

    /**
      * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
      * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
      * version.
      *
      * @param access access flags of the adapted method.
      * @param method the adapted method.
      * @param signature the signature of the adapted method (may be {@literal null}).
      * @param exceptions the exceptions thrown by the adapted method (may be {@literal null}).
      * @param classVisitor the class visitor to which this adapter delegates calls.
      */
    public GeneratorAdapter(
            final int access,
            final Method method,
            final String signature,
            final Type[] exceptions,
            final ClassVisitor classVisitor) {
        this(
                access,
                method,
                classVisitor.visitMethod(
                        access,
                        method.getName(),
                        method.getDescriptor(),
                        signature,
                        exceptions == null ? null : getInternalNames(exceptions)));
    }

    /**
      * Returns the internal names of the given types.
      *
      * @param types a set of types.
      * @return the internal names of the given types.
      */
    private static String[] getInternalNames(final Type[] types) {
        String[] names = new String[types.length];
        for (int i = 0; i < names.length; ++i) {
            names[i] = types[i].getInternalName();
        }
        return names;
    }

    public int getAccess() {
        return access;
    }

    public String getName() {
        return name;
    }

    public Type getReturnType() {
        return returnType;
    }

    public Type[] getArgumentTypes() {
        return argumentTypes.clone();
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to push constants on the stack
    // -----------------------------------------------------------------------------------------------

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final boolean value) {
        push(value ? 1 : 0);
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final int value) {
        if (value >= -1 && value <= 5) {
            mv.visitInsn(Opcodes.ICONST_0 + value);
        } else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
            mv.visitIntInsn(Opcodes.BIPUSH, value);
        } else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
            mv.visitIntInsn(Opcodes.SIPUSH, value);
        } else {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final long value) {
        if (value == 0L || value == 1L) {
            mv.visitInsn(Opcodes.LCONST_0 + (int) value);
        } else {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final float value) {
        int bits = Float.floatToIntBits(value);
        if (bits == 0L || bits == 0x3F800000 || bits == 0x40000000) { // 0..2
            mv.visitInsn(Opcodes.FCONST_0 + (int) value);
        } else {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final double value) {
        long bits = Double.doubleToLongBits(value);
        if (bits == 0L || bits == 0x3FF0000000000000L) { // +0.0d and 1.0d
            mv.visitInsn(Opcodes.DCONST_0 + (int) value);
        } else {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack. May be {@literal null}.
      */
    public void push(final String value) {
        if (value == null) {
            mv.visitInsn(Opcodes.ACONST_NULL);
        } else {
            mv.visitLdcInsn(value);
        }
    }

    /**
      * Generates the instruction to push the given value on the stack.
      *
      * @param value the value to be pushed on the stack.
      */
    public void push(final Type value) {
        if (value == null) {
            mv.visitInsn(Opcodes.ACONST_NULL);
        } else {
            switch (value.getSort()) {
                case Type.BOOLEAN:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Boolean", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.CHAR:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Character", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.BYTE:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Byte", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.SHORT:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Short", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.INT:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Integer", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.FLOAT:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Float", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.LONG:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Long", "TYPE", CLASS_DESCRIPTOR);
                    break;
                case Type.DOUBLE:
                    mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Double", "TYPE", CLASS_DESCRIPTOR);
                    break;
                default:
                    mv.visitLdcInsn(value);
                    break;
            }
        }
    }

    /**
      * Generates the instruction to push a handle on the stack.
      *
      * @param handle the handle to be pushed on the stack.
      */
    public void push(final Handle handle) {
        if (handle == null) {
            mv.visitInsn(Opcodes.ACONST_NULL);
        } else {
            mv.visitLdcInsn(handle);
        }
    }

    /**
      * Generates the instruction to push a constant dynamic on the stack.
      *
      * @param constantDynamic the constant dynamic to be pushed on the stack.
      */
    public void push(final ConstantDynamic constantDynamic) {
        if (constantDynamic == null) {
            mv.visitInsn(Opcodes.ACONST_NULL);
        } else {
            mv.visitLdcInsn(constantDynamic);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to load and store method arguments
    // -----------------------------------------------------------------------------------------------

    /**
      * Returns the index of the given method argument in the frame's local variables array.
      *
      * @param arg the index of a method argument.
      * @return the index of the given method argument in the frame's local variables array.
      */
    private int getArgIndex(final int arg) {
        int index = (access & Opcodes.ACC_STATIC) == 0 ? 1 : 0;
        for (int i = 0; i < arg; i++) {
            index += argumentTypes[i].getSize();
        }
        return index;
    }

    /**
      * Generates the instruction to push a local variable on the stack.
      *
      * @param type the type of the local variable to be loaded.
      * @param index an index in the frame's local variables array.
      */
    private void loadInsn(final Type type, final int index) {
        mv.visitVarInsn(type.getOpcode(Opcodes.ILOAD), index);
    }

    /**
      * Generates the instruction to store the top stack value in a local variable.
      *
      * @param type the type of the local variable to be stored.
      * @param index an index in the frame's local variables array.
      */
    private void storeInsn(final Type type, final int index) {
        mv.visitVarInsn(type.getOpcode(Opcodes.ISTORE), index);
    }

    /** Generates the instruction to load 'this' on the stack. */
    public void loadThis() {
        if ((access & Opcodes.ACC_STATIC) != 0) {
            throw new IllegalStateException("no 'this' pointer within static method");
        }
        mv.visitVarInsn(Opcodes.ALOAD, 0);
    }

    /**
      * Generates the instruction to load the given method argument on the stack.
      *
      * @param arg the index of a method argument.
      */
    public void loadArg(final int arg) {
        loadInsn(argumentTypes[arg], getArgIndex(arg));
    }

    /**
      * Generates the instructions to load the given method arguments on the stack.
      *
      * @param arg the index of the first method argument to be loaded.
      * @param count the number of method arguments to be loaded.
      */
    public void loadArgs(final int arg, final int count) {
        int index = getArgIndex(arg);
        for (int i = 0; i < count; ++i) {
            Type argumentType = argumentTypes[arg + i];
            loadInsn(argumentType, index);
            index += argumentType.getSize();
        }
    }

    /** Generates the instructions to load all the method arguments on the stack. */
    public void loadArgs() {
        loadArgs(0, argumentTypes.length);
    }

    /**
      * Generates the instructions to load all the method arguments on the stack, as a single object
      * array.
      */
    public void loadArgArray() {
        push(argumentTypes.length);
        newArray(OBJECT_TYPE);
        for (int i = 0; i < argumentTypes.length; i++) {
            dup();
            push(i);
            loadArg(i);
            box(argumentTypes[i]);
            arrayStore(OBJECT_TYPE);
        }
    }

    /**
      * Generates the instruction to store the top stack value in the given method argument.
      *
      * @param arg the index of a method argument.
      */
    public void storeArg(final int arg) {
        storeInsn(argumentTypes[arg], getArgIndex(arg));
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to load and store local variables
    // -----------------------------------------------------------------------------------------------

    /**
      * Returns the type of the given local variable.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      * @return the type of the given local variable.
      */
    public Type getLocalType(final int local) {
        return localTypes.get(local - firstLocal);
    }

    @Override
    protected void setLocalType(final int local, final Type type) {
        int index = local - firstLocal;
        while (localTypes.size() < index + 1) {
            localTypes.add(null);
        }
        localTypes.set(index, type);
    }

    /**
      * Generates the instruction to load the given local variable on the stack.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      */
    public void loadLocal(final int local) {
        loadInsn(getLocalType(local), local);
    }

    /**
      * Generates the instruction to load the given local variable on the stack.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      * @param type the type of this local variable.
      */
    public void loadLocal(final int local, final Type type) {
        setLocalType(local, type);
        loadInsn(type, local);
    }

    /**
      * Generates the instruction to store the top stack value in the given local variable.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      */
    public void storeLocal(final int local) {
        storeInsn(getLocalType(local), local);
    }

    /**
      * Generates the instruction to store the top stack value in the given local variable.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      * @param type the type of this local variable.
      */
    public void storeLocal(final int local, final Type type) {
        setLocalType(local, type);
        storeInsn(type, local);
    }

    /**
      * Generates the instruction to load an element from an array.
      *
      * @param type the type of the array element to be loaded.
      */
    public void arrayLoad(final Type type) {
        mv.visitInsn(type.getOpcode(Opcodes.IALOAD));
    }

    /**
      * Generates the instruction to store an element in an array.
      *
      * @param type the type of the array element to be stored.
      */
    public void arrayStore(final Type type) {
        mv.visitInsn(type.getOpcode(Opcodes.IASTORE));
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to manage the stack
    // -----------------------------------------------------------------------------------------------

    /** Generates a POP instruction. */
    public void pop() {
        mv.visitInsn(Opcodes.POP);
    }

    /** Generates a POP2 instruction. */
    public void pop2() {
        mv.visitInsn(Opcodes.POP2);
    }

    /** Generates a DUP instruction. */
    public void dup() {
        mv.visitInsn(Opcodes.DUP);
    }

    /** Generates a DUP2 instruction. */
    public void dup2() {
        mv.visitInsn(Opcodes.DUP2);
    }

    /** Generates a DUP_X1 instruction. */
    public void dupX1() {
        mv.visitInsn(Opcodes.DUP_X1);
    }

    /** Generates a DUP_X2 instruction. */
    public void dupX2() {
        mv.visitInsn(Opcodes.DUP_X2);
    }

    /** Generates a DUP2_X1 instruction. */
    public void dup2X1() {
        mv.visitInsn(Opcodes.DUP2_X1);
    }

    /** Generates a DUP2_X2 instruction. */
    public void dup2X2() {
        mv.visitInsn(Opcodes.DUP2_X2);
    }

    /** Generates a SWAP instruction. */
    public void swap() {
        mv.visitInsn(Opcodes.SWAP);
    }

    /**
      * Generates the instructions to swap the top two stack values.
      *
      * @param prev type of the top - 1 stack value.
      * @param type type of the top stack value.
      */
    public void swap(final Type prev, final Type type) {
        if (type.getSize() == 1) {
            if (prev.getSize() == 1) {
                swap(); // Same as dupX1 pop.
            } else {
                dupX2();
                pop();
            }
        } else {
            if (prev.getSize() == 1) {
                dup2X1();
                pop2();
            } else {
                dup2X2();
                pop2();
            }
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to do mathematical and logical operations
    // -----------------------------------------------------------------------------------------------

    /**
      * Generates the instruction to do the specified mathematical or logical operation.
      *
      * @param op a mathematical or logical operation. Must be one of ADD, SUB, MUL, DIV, REM, NEG,
      *     SHL, SHR, USHR, AND, OR, XOR.
      * @param type the type of the operand(s) for this operation.
      */
    public void math(final int op, final Type type) {
        mv.visitInsn(type.getOpcode(op));
    }

    /** Generates the instructions to compute the bitwise negation of the top stack value. */
    public void not() {
        mv.visitInsn(Opcodes.ICONST_1);
        mv.visitInsn(Opcodes.IXOR);
    }

    /**
      * Generates the instruction to increment the given local variable.
      *
      * @param local the local variable to be incremented.
      * @param amount the amount by which the local variable must be incremented.
      */
    public void iinc(final int local, final int amount) {
        mv.visitIincInsn(local, amount);
    }

    /**
      * Generates the instructions to cast a numerical value from one type to another.
      *
      * @param from the type of the top stack value
      * @param to the type into which this value must be cast.
      */
    public void cast(final Type from, final Type to) {
        if (from != to) {
            if (from.getSort() < Type.BOOLEAN
                    || from.getSort() > Type.DOUBLE
                    || to.getSort() < Type.BOOLEAN
                    || to.getSort() > Type.DOUBLE) {
                throw new IllegalArgumentException("Cannot cast from " + from + " to " + to);
            }
            InstructionAdapter.cast(mv, from, to);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to do boxing and unboxing operations
    // -----------------------------------------------------------------------------------------------

    private static Type getBoxedType(final Type type) {
        switch (type.getSort()) {
            case Type.BYTE:
                return BYTE_TYPE;
            case Type.BOOLEAN:
                return BOOLEAN_TYPE;
            case Type.SHORT:
                return SHORT_TYPE;
            case Type.CHAR:
                return CHARACTER_TYPE;
            case Type.INT:
                return INTEGER_TYPE;
            case Type.FLOAT:
                return FLOAT_TYPE;
            case Type.LONG:
                return LONG_TYPE;
            case Type.DOUBLE:
                return DOUBLE_TYPE;
            default:
                return type;
        }
    }

    /**
      * Generates the instructions to box the top stack value. This value is replaced by its boxed
      * equivalent on top of the stack.
      *
      * @param type the type of the top stack value.
      */
    public void box(final Type type) {
        if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
            return;
        }
        if (type == Type.VOID_TYPE) {
            push((String) null);
        } else {
            Type boxedType = getBoxedType(type);
            newInstance(boxedType);
            if (type.getSize() == 2) {
                // Pp -> Ppo -> oPpo -> ooPpo -> ooPp -> o
                dupX2();
                dupX2();
                pop();
            } else {
                // p -> po -> opo -> oop -> o
                dupX1();
                swap();
            }
            invokeConstructor(boxedType, new Method("<init>", Type.VOID_TYPE, new Type[] {type}));
        }
    }

    /**
      * Generates the instructions to box the top stack value using Java 5's valueOf() method. This
      * value is replaced by its boxed equivalent on top of the stack.
      *
      * @param type the type of the top stack value.
      */
    public void valueOf(final Type type) {
        if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
            return;
        }
        if (type == Type.VOID_TYPE) {
            push((String) null);
        } else {
            Type boxedType = getBoxedType(type);
            invokeStatic(boxedType, new Method("valueOf", boxedType, new Type[] {type}));
        }
    }

    /**
      * Generates the instructions to unbox the top stack value. This value is replaced by its unboxed
      * equivalent on top of the stack.
      *
      * @param type the type of the top stack value.
      */
    public void unbox(final Type type) {
        Type boxedType = NUMBER_TYPE;
        Method unboxMethod;
        switch (type.getSort()) {
            case Type.VOID:
                return;
            case Type.CHAR:
                boxedType = CHARACTER_TYPE;
                unboxMethod = CHAR_VALUE;
                break;
            case Type.BOOLEAN:
                boxedType = BOOLEAN_TYPE;
                unboxMethod = BOOLEAN_VALUE;
                break;
            case Type.DOUBLE:
                unboxMethod = DOUBLE_VALUE;
                break;
            case Type.FLOAT:
                unboxMethod = FLOAT_VALUE;
                break;
            case Type.LONG:
                unboxMethod = LONG_VALUE;
                break;
            case Type.INT:
            case Type.SHORT:
            case Type.BYTE:
                unboxMethod = INT_VALUE;
                break;
            default:
                unboxMethod = null;
                break;
        }
        if (unboxMethod == null) {
            checkCast(type);
        } else {
            checkCast(boxedType);
            invokeVirtual(boxedType, unboxMethod);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to jump to other instructions
    // -----------------------------------------------------------------------------------------------

    /**
      * Constructs a new {@link Label}.
      *
      * @return a new {@link Label}.
      */
    public Label newLabel() {
        return new Label();
    }

    /**
      * Marks the current code position with the given label.
      *
      * @param label a label.
      */
    public void mark(final Label label) {
        mv.visitLabel(label);
    }

    /**
      * Marks the current code position with a new label.
      *
      * @return the label that was created to mark the current code position.
      */
    public Label mark() {
        Label label = new Label();
        mv.visitLabel(label);
        return label;
    }

    /**
      * Generates the instructions to jump to a label based on the comparison of the top two stack
      * values.
      *
      * @param type the type of the top two stack values.
      * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
      * @param label where to jump if the comparison result is {@literal true}.
      */
    public void ifCmp(final Type type, final int mode, final Label label) {
        switch (type.getSort()) {
            case Type.LONG:
                mv.visitInsn(Opcodes.LCMP);
                break;
            case Type.DOUBLE:
                mv.visitInsn(mode == GE || mode == GT ? Opcodes.DCMPL : Opcodes.DCMPG);
                break;
            case Type.FLOAT:
                mv.visitInsn(mode == GE || mode == GT ? Opcodes.FCMPL : Opcodes.FCMPG);
                break;
            case Type.ARRAY:
            case Type.OBJECT:
                if (mode == EQ) {
                    mv.visitJumpInsn(Opcodes.IF_ACMPEQ, label);
                    return;
                } else if (mode == NE) {
                    mv.visitJumpInsn(Opcodes.IF_ACMPNE, label);
                    return;
                } else {
                    throw new IllegalArgumentException("Bad comparison for type " + type);
                }
            default:
                int intOp = -1;
                switch (mode) {
                    case EQ:
                        intOp = Opcodes.IF_ICMPEQ;
                        break;
                    case NE:
                        intOp = Opcodes.IF_ICMPNE;
                        break;
                    case GE:
                        intOp = Opcodes.IF_ICMPGE;
                        break;
                    case LT:
                        intOp = Opcodes.IF_ICMPLT;
                        break;
                    case LE:
                        intOp = Opcodes.IF_ICMPLE;
                        break;
                    case GT:
                        intOp = Opcodes.IF_ICMPGT;
                        break;
                    default:
                        throw new IllegalArgumentException("Bad comparison mode " + mode);
                }
                mv.visitJumpInsn(intOp, label);
                return;
        }
        mv.visitJumpInsn(mode, label);
    }

    /**
      * Generates the instructions to jump to a label based on the comparison of the top two integer
      * stack values.
      *
      * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
      * @param label where to jump if the comparison result is {@literal true}.
      */
    public void ifICmp(final int mode, final Label label) {
        ifCmp(Type.INT_TYPE, mode, label);
    }

    /**
      * Generates the instructions to jump to a label based on the comparison of the top integer stack
      * value with zero.
      *
      * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
      * @param label where to jump if the comparison result is {@literal true}.
      */
    public void ifZCmp(final int mode, final Label label) {
        mv.visitJumpInsn(mode, label);
    }

    /**
      * Generates the instruction to jump to the given label if the top stack value is null.
      *
      * @param label where to jump if the condition is {@literal true}.
      */
    public void ifNull(final Label label) {
        mv.visitJumpInsn(Opcodes.IFNULL, label);
    }

    /**
      * Generates the instruction to jump to the given label if the top stack value is not null.
      *
      * @param label where to jump if the condition is {@literal true}.
      */
    public void ifNonNull(final Label label) {
        mv.visitJumpInsn(Opcodes.IFNONNULL, label);
    }

    /**
      * Generates the instruction to jump to the given label.
      *
      * @param label where to jump if the condition is {@literal true}.
      */
    public void goTo(final Label label) {
        mv.visitJumpInsn(Opcodes.GOTO, label);
    }

    /**
      * Generates a RET instruction.
      *
      * @param local a local variable identifier, as returned by {@link
      *     LocalVariablesSorter#newLocal(Type)}.
      */
    public void ret(final int local) {
        mv.visitVarInsn(Opcodes.RET, local);
    }

    /**
      * Generates the instructions for a switch statement.
      *
      * @param keys the switch case keys.
      * @param generator a generator to generate the code for the switch cases.
      */
    public void tableSwitch(final int[] keys, final TableSwitchGenerator generator) {
        float density;
        if (keys.length == 0) {
            density = 0;
        } else {
            density = (float) keys.length / (keys[keys.length - 1] - keys[0] + 1);
        }
        tableSwitch(keys, generator, density >= 0.5f);
    }

    /**
      * Generates the instructions for a switch statement.
      *
      * @param keys the switch case keys.
      * @param generator a generator to generate the code for the switch cases.
      * @param useTable {@literal true} to use a TABLESWITCH instruction, or {@literal false} to use a
      *     LOOKUPSWITCH instruction.
      */
    public void tableSwitch(
            final int[] keys, final TableSwitchGenerator generator, final boolean useTable) {
        for (int i = 1; i < keys.length; ++i) {
            if (keys[i] < keys[i - 1]) {
                throw new IllegalArgumentException("keys must be sorted in ascending order");
            }
        }
        Label defaultLabel = newLabel();
        Label endLabel = newLabel();
        if (keys.length > 0) {
            int numKeys = keys.length;
            if (useTable) {
                int min = keys[0];
                int max = keys[numKeys - 1];
                int range = max - min + 1;
                Label[] labels = new Label[range];
                Arrays.fill(labels, defaultLabel);
                for (int i = 0; i < numKeys; ++i) {
                    labels[keys[i] - min] = newLabel();
                }
                mv.visitTableSwitchInsn(min, max, defaultLabel, labels);
                for (int i = 0; i < range; ++i) {
                    Label label = labels[i];
                    if (label != defaultLabel) {
                        mark(label);
                        generator.generateCase(i + min, endLabel);
                    }
                }
            } else {
                Label[] labels = new Label[numKeys];
                for (int i = 0; i < numKeys; ++i) {
                    labels[i] = newLabel();
                }
                mv.visitLookupSwitchInsn(defaultLabel, keys, labels);
                for (int i = 0; i < numKeys; ++i) {
                    mark(labels[i]);
                    generator.generateCase(keys[i], endLabel);
                }
            }
        }
        mark(defaultLabel);
        generator.generateDefault();
        mark(endLabel);
    }

    /** Generates the instruction to return the top stack value to the caller. */
    public void returnValue() {
        mv.visitInsn(returnType.getOpcode(Opcodes.IRETURN));
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to load and store fields
    // -----------------------------------------------------------------------------------------------

    /**
      * Generates a get field or set field instruction.
      *
      * @param opcode the instruction's opcode.
      * @param ownerType the class in which the field is defined.
      * @param name the name of the field.
      * @param fieldType the type of the field.
      */
    private void fieldInsn(
            final int opcode, final Type ownerType, final String name, final Type fieldType) {
        mv.visitFieldInsn(opcode, ownerType.getInternalName(), name, fieldType.getDescriptor());
    }

    /**
      * Generates the instruction to push the value of a static field on the stack.
      *
      * @param owner the class in which the field is defined.
      * @param name the name of the field.
      * @param type the type of the field.
      */
    public void getStatic(final Type owner, final String name, final Type type) {
        fieldInsn(Opcodes.GETSTATIC, owner, name, type);
    }

    /**
      * Generates the instruction to store the top stack value in a static field.
      *
      * @param owner the class in which the field is defined.
      * @param name the name of the field.
      * @param type the type of the field.
      */
    public void putStatic(final Type owner, final String name, final Type type) {
        fieldInsn(Opcodes.PUTSTATIC, owner, name, type);
    }

    /**
      * Generates the instruction to push the value of a non static field on the stack.
      *
      * @param owner the class in which the field is defined.
      * @param name the name of the field.
      * @param type the type of the field.
      */
    public void getField(final Type owner, final String name, final Type type) {
        fieldInsn(Opcodes.GETFIELD, owner, name, type);
    }

    /**
      * Generates the instruction to store the top stack value in a non static field.
      *
      * @param owner the class in which the field is defined.
      * @param name the name of the field.
      * @param type the type of the field.
      */
    public void putField(final Type owner, final String name, final Type type) {
        fieldInsn(Opcodes.PUTFIELD, owner, name, type);
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to invoke methods
    // -----------------------------------------------------------------------------------------------

    /**
      * Generates an invoke method instruction.
      *
      * @param opcode the instruction's opcode.
      * @param type the class in which the method is defined.
      * @param method the method to be invoked.
      * @param isInterface whether the 'type' class is an interface or not.
      */
    private void invokeInsn(
            final int opcode, final Type type, final Method method, final boolean isInterface) {
        String owner = type.getSort() == Type.ARRAY ? type.getDescriptor() : type.getInternalName();
        mv.visitMethodInsn(opcode, owner, method.getName(), method.getDescriptor(), isInterface);
    }

    /**
      * Generates the instruction to invoke a normal method.
      *
      * @param owner the class in which the method is defined.
      * @param method the method to be invoked.
      */
    public void invokeVirtual(final Type owner, final Method method) {
        invokeInsn(Opcodes.INVOKEVIRTUAL, owner, method, false);
    }

    /**
      * Generates the instruction to invoke a constructor.
      *
      * @param type the class in which the constructor is defined.
      * @param method the constructor to be invoked.
      */
    public void invokeConstructor(final Type type, final Method method) {
        invokeInsn(Opcodes.INVOKESPECIAL, type, method, false);
    }

    /**
      * Generates the instruction to invoke a static method.
      *
      * @param owner the class in which the method is defined.
      * @param method the method to be invoked.
      */
    public void invokeStatic(final Type owner, final Method method) {
        invokeInsn(Opcodes.INVOKESTATIC, owner, method, false);
    }

    /**
      * Generates the instruction to invoke an interface method.
      *
      * @param owner the class in which the method is defined.
      * @param method the method to be invoked.
      */
    public void invokeInterface(final Type owner, final Method method) {
        invokeInsn(Opcodes.INVOKEINTERFACE, owner, method, true);
    }

    /**
      * Generates an invokedynamic instruction.
      *
      * @param name the method's name.
      * @param descriptor the method's descriptor (see {@link Type}).
      * @param bootstrapMethodHandle the bootstrap method.
      * @param bootstrapMethodArguments the bootstrap method constant arguments. Each argument must be
      *     an {@link Integer}, {@link Float}, {@link Long}, {@link Double}, {@link String}, {@link
      *     Type} or {@link Handle} value. This method is allowed to modify the content of the array so
      *     a caller should expect that this array may change.
      */
    public void invokeDynamic(
            final String name,
            final String descriptor,
            final Handle bootstrapMethodHandle,
            final Object... bootstrapMethodArguments) {
        mv.visitInvokeDynamicInsn(name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
    }

    // -----------------------------------------------------------------------------------------------
    // Instructions to create objects and arrays
    // -----------------------------------------------------------------------------------------------

    /**
      * Generates a type dependent instruction.
      *
      * @param opcode the instruction's opcode.
      * @param type the instruction's operand.
      */
    private void typeInsn(final int opcode, final Type type) {
        mv.visitTypeInsn(opcode, type.getInternalName());
    }

    /**
      * Generates the instruction to create a new object.
      *
      * @param type the class of the object to be created.
      */
    public void newInstance(final Type type) {
        typeInsn(Opcodes.NEW, type);
    }

    /**
      * Generates the instruction to create a new array.
      *
      * @param type the type of the array elements.
      */
    public void newArray(final Type type) {
        InstructionAdapter.newarray(mv, type);
    }

    // -----------------------------------------------------------------------------------------------
    // Miscellaneous instructions
    // -----------------------------------------------------------------------------------------------

    /** Generates the instruction to compute the length of an array. */
    public void arrayLength() {
        mv.visitInsn(Opcodes.ARRAYLENGTH);
    }

    /** Generates the instruction to throw an exception. */
    public void throwException() {
        mv.visitInsn(Opcodes.ATHROW);
    }

    /**
      * Generates the instructions to create and throw an exception. The exception class must have a
      * constructor with a single String argument.
      *
      * @param type the class of the exception to be thrown.
      * @param message the detailed message of the exception.
      */
    public void throwException(final Type type, final String message) {
        newInstance(type);
        dup();
        push(message);
        invokeConstructor(type, Method.getMethod("void <init> (String)"));
        throwException();
    }

    /**
      * Generates the instruction to check that the top stack value is of the given type.
      *
      * @param type a class or interface type.
      */
    public void checkCast(final Type type) {
        if (!type.equals(OBJECT_TYPE)) {
            typeInsn(Opcodes.CHECKCAST, type);
        }
    }

    /**
      * Generates the instruction to test if the top stack value is of the given type.
      *
      * @param type a class or interface type.
      */
    public void instanceOf(final Type type) {
        typeInsn(Opcodes.INSTANCEOF, type);
    }

    /** Generates the instruction to get the monitor of the top stack value. */
    public void monitorEnter() {
        mv.visitInsn(Opcodes.MONITORENTER);
    }

    /** Generates the instruction to release the monitor of the top stack value. */
    public void monitorExit() {
        mv.visitInsn(Opcodes.MONITOREXIT);
    }

    // -----------------------------------------------------------------------------------------------
    // Non instructions
    // -----------------------------------------------------------------------------------------------

    /** Marks the end of the visited method. */
    public void endMethod() {
        if ((access & Opcodes.ACC_ABSTRACT) == 0) {
            mv.visitMaxs(0, 0);
        }
        mv.visitEnd();
    }

    /**
      * Marks the start of an exception handler.
      *
      * @param start beginning of the exception handler's scope (inclusive).
      * @param end end of the exception handler's scope (exclusive).
      * @param exception internal name of the type of exceptions handled by the handler.
      */
    public void catchException(final Label start, final Label end, final Type exception) {
        Label catchLabel = new Label();
        if (exception == null) {
            mv.visitTryCatchBlock(start, end, catchLabel, null);
        } else {
            mv.visitTryCatchBlock(start, end, catchLabel, exception.getInternalName());
        }
        mark(catchLabel);
    }
}