https://openjdk.java.net/ 
/*
 * Copyright (c) 2012, 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 java.lang.invoke;

import jdk.internal.org.objectweb.asm.*;
import sun.invoke.util.BytecodeDescriptor;
import jdk.internal.misc.Unsafe;
import sun.security.action.GetPropertyAction;

import java.io.FilePermission;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.LinkedHashSet;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.PropertyPermission;
import java.util.Set;

import static jdk.internal.org.objectweb.asm.Opcodes.*;


Lambda metafactory implementation which dynamically creates an
inner-class-like class per lambda callsite.

See Also:
  • LambdaMetafactory
/**
 * Lambda metafactory implementation which dynamically creates an
 * inner-class-like class per lambda callsite.
 *
 * @see LambdaMetafactory
 */
/* package */ final class InnerClassLambdaMetafactory extends AbstractValidatingLambdaMetafactory {
    private static final Unsafe UNSAFE = Unsafe.getUnsafe();

    private static final int CLASSFILE_VERSION = 52;
    private static final String METHOD_DESCRIPTOR_VOID = Type.getMethodDescriptor(Type.VOID_TYPE);
    private static final String JAVA_LANG_OBJECT = "java/lang/Object";
    private static final String NAME_CTOR = "<init>";
    private static final String NAME_FACTORY = "get$Lambda";

    //Serialization support
    private static final String NAME_SERIALIZED_LAMBDA = "java/lang/invoke/SerializedLambda";
    private static final String NAME_NOT_SERIALIZABLE_EXCEPTION = "java/io/NotSerializableException";
    private static final String DESCR_METHOD_WRITE_REPLACE = "()Ljava/lang/Object;";
    private static final String DESCR_METHOD_WRITE_OBJECT = "(Ljava/io/ObjectOutputStream;)V";
    private static final String DESCR_METHOD_READ_OBJECT = "(Ljava/io/ObjectInputStream;)V";
    private static final String NAME_METHOD_WRITE_REPLACE = "writeReplace";
    private static final String NAME_METHOD_READ_OBJECT = "readObject";
    private static final String NAME_METHOD_WRITE_OBJECT = "writeObject";

    private static final String DESCR_CLASS = "Ljava/lang/Class;";
    private static final String DESCR_STRING = "Ljava/lang/String;";
    private static final String DESCR_OBJECT = "Ljava/lang/Object;";
    private static final String DESCR_CTOR_SERIALIZED_LAMBDA
            = "(" + DESCR_CLASS + DESCR_STRING + DESCR_STRING + DESCR_STRING + "I"
            + DESCR_STRING + DESCR_STRING + DESCR_STRING + DESCR_STRING + "[" + DESCR_OBJECT + ")V";

    private static final String DESCR_CTOR_NOT_SERIALIZABLE_EXCEPTION = "(Ljava/lang/String;)V";
    private static final String[] SER_HOSTILE_EXCEPTIONS = new String[] {NAME_NOT_SERIALIZABLE_EXCEPTION};


    private static final String[] EMPTY_STRING_ARRAY = new String[0];

    // Used to ensure that each spun class name is unique
    private static final AtomicInteger counter = new AtomicInteger(0);

    // For dumping generated classes to disk, for debugging purposes
    private static final ProxyClassesDumper dumper;

    static {
        final String key = "jdk.internal.lambda.dumpProxyClasses";
        String path = GetPropertyAction.privilegedGetProperty(key);
        dumper = (null == path) ? null : ProxyClassesDumper.getInstance(path);
    }

    // See context values in AbstractValidatingLambdaMetafactory
    private final String implMethodClassName;        // Name of type containing implementation "CC"
    private final String implMethodName;             // Name of implementation method "impl"
    private final String implMethodDesc;             // Type descriptor for implementation methods "(I)Ljava/lang/String;"
    private final MethodType constructorType;        // Generated class constructor type "(CC)void"
    private final ClassWriter cw;                    // ASM class writer
    private final String[] argNames;                 // Generated names for the constructor arguments
    private final String[] argDescs;                 // Type descriptors for the constructor arguments
    private final String lambdaClassName;            // Generated name for the generated class "X$$Lambda$1"

    
General meta-factory constructor, supporting both standard cases and
allowing for uncommon options such as serialization or bridging.

Params:
  • caller – Stacked automatically by VM; represents a lookup context
              with the accessibility privileges of the caller.
  • invokedType – Stacked automatically by VM; the signature of the
                   invoked method, which includes the expected static
                   type of the returned lambda object, and the static
                   types of the captured arguments for the lambda.  In
                   the event that the implementation method is an
                   instance method, the first argument in the invocation
                   signature will correspond to the receiver.
  • samMethodName – Name of the method in the functional interface to
                     which the lambda or method reference is being
                     converted, represented as a String.
  • samMethodType – Type of the method in the functional interface to
                     which the lambda or method reference is being
                     converted, represented as a MethodType.
  • implMethod – The implementation method which should be called (with
                  suitable adaptation of argument types, return types,
                  and adjustment for captured arguments) when methods of
                  the resulting functional interface instance are invoked.
  • instantiatedMethodType – The signature of the primary functional
                              interface method after type variables are
                              substituted with their instantiation from
                              the capture site
  • isSerializable – Should the lambda be made serializable? If set, either the target type or one of the additional SAM types must extend Serializable.
  • markerInterfaces – Additional interfaces which the lambda object
                      should implement.
  • additionalBridges – Method types for additional signatures to be
                         bridged to the implementation method
Throws:
/**
     * General meta-factory constructor, supporting both standard cases and
     * allowing for uncommon options such as serialization or bridging.
     *
     * @param caller Stacked automatically by VM; represents a lookup context
     *               with the accessibility privileges of the caller.
     * @param invokedType Stacked automatically by VM; the signature of the
     *                    invoked method, which includes the expected static
     *                    type of the returned lambda object, and the static
     *                    types of the captured arguments for the lambda.  In
     *                    the event that the implementation method is an
     *                    instance method, the first argument in the invocation
     *                    signature will correspond to the receiver.
     * @param samMethodName Name of the method in the functional interface to
     *                      which the lambda or method reference is being
     *                      converted, represented as a String.
     * @param samMethodType Type of the method in the functional interface to
     *                      which the lambda or method reference is being
     *                      converted, represented as a MethodType.
     * @param implMethod The implementation method which should be called (with
     *                   suitable adaptation of argument types, return types,
     *                   and adjustment for captured arguments) when methods of
     *                   the resulting functional interface instance are invoked.
     * @param instantiatedMethodType The signature of the primary functional
     *                               interface method after type variables are
     *                               substituted with their instantiation from
     *                               the capture site
     * @param isSerializable Should the lambda be made serializable?  If set,
     *                       either the target type or one of the additional SAM
     *                       types must extend {@code Serializable}.
     * @param markerInterfaces Additional interfaces which the lambda object
     *                       should implement.
     * @param additionalBridges Method types for additional signatures to be
     *                          bridged to the implementation method
     * @throws LambdaConversionException If any of the meta-factory protocol
     * invariants are violated
     */
    public InnerClassLambdaMetafactory(MethodHandles.Lookup caller,
                                       MethodType invokedType,
                                       String samMethodName,
                                       MethodType samMethodType,
                                       MethodHandle implMethod,
                                       MethodType instantiatedMethodType,
                                       boolean isSerializable,
                                       Class<?>[] markerInterfaces,
                                       MethodType[] additionalBridges)
            throws LambdaConversionException {
        super(caller, invokedType, samMethodName, samMethodType,
              implMethod, instantiatedMethodType,
              isSerializable, markerInterfaces, additionalBridges);
        implMethodClassName = implClass.getName().replace('.', '/');
        implMethodName = implInfo.getName();
        implMethodDesc = implInfo.getMethodType().toMethodDescriptorString();
        constructorType = invokedType.changeReturnType(Void.TYPE);
        lambdaClassName = targetClass.getName().replace('.', '/') + "$$Lambda$" + counter.incrementAndGet();
        cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        int parameterCount = invokedType.parameterCount();
        if (parameterCount > 0) {
            argNames = new String[parameterCount];
            argDescs = new String[parameterCount];
            for (int i = 0; i < parameterCount; i++) {
                argNames[i] = "arg$" + (i + 1);
                argDescs[i] = BytecodeDescriptor.unparse(invokedType.parameterType(i));
            }
        } else {
            argNames = argDescs = EMPTY_STRING_ARRAY;
        }
    }

    
Build the CallSite. Generate a class file which implements the functional
interface, define the class, if there are no parameters create an instance
of the class which the CallSite will return, otherwise, generate handles
which will call the class' constructor.

Throws:
Returns:a CallSite, which, when invoked, will return an instance of the
functional interface
/**
     * Build the CallSite. Generate a class file which implements the functional
     * interface, define the class, if there are no parameters create an instance
     * of the class which the CallSite will return, otherwise, generate handles
     * which will call the class' constructor.
     *
     * @return a CallSite, which, when invoked, will return an instance of the
     * functional interface
     * @throws ReflectiveOperationException
     * @throws LambdaConversionException If properly formed functional interface
     * is not found
     */
    @Override
    CallSite buildCallSite() throws LambdaConversionException {
        final Class<?> innerClass = spinInnerClass();
        if (invokedType.parameterCount() == 0) {
            final Constructor<?>[] ctrs = AccessController.doPrivileged(
                    new PrivilegedAction<>() {
                @Override
                public Constructor<?>[] run() {
                    Constructor<?>[] ctrs = innerClass.getDeclaredConstructors();
                    if (ctrs.length == 1) {
                        // The lambda implementing inner class constructor is private, set
                        // it accessible (by us) before creating the constant sole instance
                        ctrs[0].setAccessible(true);
                    }
                    return ctrs;
                }
                    });
            if (ctrs.length != 1) {
                throw new LambdaConversionException("Expected one lambda constructor for "
                        + innerClass.getCanonicalName() + ", got " + ctrs.length);
            }

            try {
                Object inst = ctrs[0].newInstance();
                return new ConstantCallSite(MethodHandles.constant(samBase, inst));
            }
            catch (ReflectiveOperationException e) {
                throw new LambdaConversionException("Exception instantiating lambda object", e);
            }
        } else {
            try {
                UNSAFE.ensureClassInitialized(innerClass);
                return new ConstantCallSite(
                        MethodHandles.Lookup.IMPL_LOOKUP
                             .findStatic(innerClass, NAME_FACTORY, invokedType));
            }
            catch (ReflectiveOperationException e) {
                throw new LambdaConversionException("Exception finding constructor", e);
            }
        }
    }

    
Generate a class file which implements the functional
interface, define and return the class.

Throws:
Implementation Note:The class that is generated does not include signature
information for exceptions that may be present on the SAM method.
This is to reduce classfile size, and is harmless as checked exceptions
are erased anyway, no one will ever compile against this classfile,
and we make no guarantees about the reflective properties of lambda
objects.
Returns:a Class which implements the functional interface
/**
     * Generate a class file which implements the functional
     * interface, define and return the class.
     *
     * @implNote The class that is generated does not include signature
     * information for exceptions that may be present on the SAM method.
     * This is to reduce classfile size, and is harmless as checked exceptions
     * are erased anyway, no one will ever compile against this classfile,
     * and we make no guarantees about the reflective properties of lambda
     * objects.
     *
     * @return a Class which implements the functional interface
     * @throws LambdaConversionException If properly formed functional interface
     * is not found
     */
    private Class<?> spinInnerClass() throws LambdaConversionException {
        String[] interfaces;
        String samIntf = samBase.getName().replace('.', '/');
        boolean accidentallySerializable = !isSerializable && Serializable.class.isAssignableFrom(samBase);
        if (markerInterfaces.length == 0) {
            interfaces = new String[]{samIntf};
        } else {
            // Assure no duplicate interfaces (ClassFormatError)
            Set<String> itfs = new LinkedHashSet<>(markerInterfaces.length + 1);
            itfs.add(samIntf);
            for (Class<?> markerInterface : markerInterfaces) {
                itfs.add(markerInterface.getName().replace('.', '/'));
                accidentallySerializable |= !isSerializable && Serializable.class.isAssignableFrom(markerInterface);
            }
            interfaces = itfs.toArray(new String[itfs.size()]);
        }

        cw.visit(CLASSFILE_VERSION, ACC_SUPER + ACC_FINAL + ACC_SYNTHETIC,
                 lambdaClassName, null,
                 JAVA_LANG_OBJECT, interfaces);

        // Generate final fields to be filled in by constructor
        for (int i = 0; i < argDescs.length; i++) {
            FieldVisitor fv = cw.visitField(ACC_PRIVATE + ACC_FINAL,
                                            argNames[i],
                                            argDescs[i],
                                            null, null);
            fv.visitEnd();
        }

        generateConstructor();

        if (invokedType.parameterCount() != 0) {
            generateFactory();
        }

        // Forward the SAM method
        MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, samMethodName,
                                          samMethodType.toMethodDescriptorString(), null, null);
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);
        new ForwardingMethodGenerator(mv).generate(samMethodType);

        // Forward the bridges
        if (additionalBridges != null) {
            for (MethodType mt : additionalBridges) {
                mv = cw.visitMethod(ACC_PUBLIC|ACC_BRIDGE, samMethodName,
                                    mt.toMethodDescriptorString(), null, null);
                mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);
                new ForwardingMethodGenerator(mv).generate(mt);
            }
        }

        if (isSerializable)
            generateSerializationFriendlyMethods();
        else if (accidentallySerializable)
            generateSerializationHostileMethods();

        cw.visitEnd();

        // Define the generated class in this VM.

        final byte[] classBytes = cw.toByteArray();

        // If requested, dump out to a file for debugging purposes
        if (dumper != null) {
            AccessController.doPrivileged(new PrivilegedAction<>() {
                @Override
                public Void run() {
                    dumper.dumpClass(lambdaClassName, classBytes);
                    return null;
                }
            }, null,
            new FilePermission("<<ALL FILES>>", "read, write"),
            // createDirectories may need it
            new PropertyPermission("user.dir", "read"));
        }

        return UNSAFE.defineAnonymousClass(targetClass, classBytes, null);
    }

    
Generate the factory method for the class

/**
     * Generate the factory method for the class
     */
    private void generateFactory() {
        MethodVisitor m = cw.visitMethod(ACC_PRIVATE | ACC_STATIC, NAME_FACTORY, invokedType.toMethodDescriptorString(), null, null);
        m.visitCode();
        m.visitTypeInsn(NEW, lambdaClassName);
        m.visitInsn(Opcodes.DUP);
        int parameterCount = invokedType.parameterCount();
        for (int typeIndex = 0, varIndex = 0; typeIndex < parameterCount; typeIndex++) {
            Class<?> argType = invokedType.parameterType(typeIndex);
            m.visitVarInsn(getLoadOpcode(argType), varIndex);
            varIndex += getParameterSize(argType);
        }
        m.visitMethodInsn(INVOKESPECIAL, lambdaClassName, NAME_CTOR, constructorType.toMethodDescriptorString(), false);
        m.visitInsn(ARETURN);
        m.visitMaxs(-1, -1);
        m.visitEnd();
    }

    
Generate the constructor for the class

/**
     * Generate the constructor for the class
     */
    private void generateConstructor() {
        // Generate constructor
        MethodVisitor ctor = cw.visitMethod(ACC_PRIVATE, NAME_CTOR,
                                            constructorType.toMethodDescriptorString(), null, null);
        ctor.visitCode();
        ctor.visitVarInsn(ALOAD, 0);
        ctor.visitMethodInsn(INVOKESPECIAL, JAVA_LANG_OBJECT, NAME_CTOR,
                             METHOD_DESCRIPTOR_VOID, false);
        int parameterCount = invokedType.parameterCount();
        for (int i = 0, lvIndex = 0; i < parameterCount; i++) {
            ctor.visitVarInsn(ALOAD, 0);
            Class<?> argType = invokedType.parameterType(i);
            ctor.visitVarInsn(getLoadOpcode(argType), lvIndex + 1);
            lvIndex += getParameterSize(argType);
            ctor.visitFieldInsn(PUTFIELD, lambdaClassName, argNames[i], argDescs[i]);
        }
        ctor.visitInsn(RETURN);
        // Maxs computed by ClassWriter.COMPUTE_MAXS, these arguments ignored
        ctor.visitMaxs(-1, -1);
        ctor.visitEnd();
    }

    
Generate a writeReplace method that supports serialization

/**
     * Generate a writeReplace method that supports serialization
     */
    private void generateSerializationFriendlyMethods() {
        TypeConvertingMethodAdapter mv
                = new TypeConvertingMethodAdapter(
                    cw.visitMethod(ACC_PRIVATE + ACC_FINAL,
                    NAME_METHOD_WRITE_REPLACE, DESCR_METHOD_WRITE_REPLACE,
                    null, null));

        mv.visitCode();
        mv.visitTypeInsn(NEW, NAME_SERIALIZED_LAMBDA);
        mv.visitInsn(DUP);
        mv.visitLdcInsn(Type.getType(targetClass));
        mv.visitLdcInsn(invokedType.returnType().getName().replace('.', '/'));
        mv.visitLdcInsn(samMethodName);
        mv.visitLdcInsn(samMethodType.toMethodDescriptorString());
        mv.visitLdcInsn(implInfo.getReferenceKind());
        mv.visitLdcInsn(implInfo.getDeclaringClass().getName().replace('.', '/'));
        mv.visitLdcInsn(implInfo.getName());
        mv.visitLdcInsn(implInfo.getMethodType().toMethodDescriptorString());
        mv.visitLdcInsn(instantiatedMethodType.toMethodDescriptorString());
        mv.iconst(argDescs.length);
        mv.visitTypeInsn(ANEWARRAY, JAVA_LANG_OBJECT);
        for (int i = 0; i < argDescs.length; i++) {
            mv.visitInsn(DUP);
            mv.iconst(i);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitFieldInsn(GETFIELD, lambdaClassName, argNames[i], argDescs[i]);
            mv.boxIfTypePrimitive(Type.getType(argDescs[i]));
            mv.visitInsn(AASTORE);
        }
        mv.visitMethodInsn(INVOKESPECIAL, NAME_SERIALIZED_LAMBDA, NAME_CTOR,
                DESCR_CTOR_SERIALIZED_LAMBDA, false);
        mv.visitInsn(ARETURN);
        // Maxs computed by ClassWriter.COMPUTE_MAXS, these arguments ignored
        mv.visitMaxs(-1, -1);
        mv.visitEnd();
    }

    
Generate a readObject/writeObject method that is hostile to serialization

/**
     * Generate a readObject/writeObject method that is hostile to serialization
     */
    private void generateSerializationHostileMethods() {
        MethodVisitor mv = cw.visitMethod(ACC_PRIVATE + ACC_FINAL,
                                          NAME_METHOD_WRITE_OBJECT, DESCR_METHOD_WRITE_OBJECT,
                                          null, SER_HOSTILE_EXCEPTIONS);
        mv.visitCode();
        mv.visitTypeInsn(NEW, NAME_NOT_SERIALIZABLE_EXCEPTION);
        mv.visitInsn(DUP);
        mv.visitLdcInsn("Non-serializable lambda");
        mv.visitMethodInsn(INVOKESPECIAL, NAME_NOT_SERIALIZABLE_EXCEPTION, NAME_CTOR,
                           DESCR_CTOR_NOT_SERIALIZABLE_EXCEPTION, false);
        mv.visitInsn(ATHROW);
        mv.visitMaxs(-1, -1);
        mv.visitEnd();

        mv = cw.visitMethod(ACC_PRIVATE + ACC_FINAL,
                            NAME_METHOD_READ_OBJECT, DESCR_METHOD_READ_OBJECT,
                            null, SER_HOSTILE_EXCEPTIONS);
        mv.visitCode();
        mv.visitTypeInsn(NEW, NAME_NOT_SERIALIZABLE_EXCEPTION);
        mv.visitInsn(DUP);
        mv.visitLdcInsn("Non-serializable lambda");
        mv.visitMethodInsn(INVOKESPECIAL, NAME_NOT_SERIALIZABLE_EXCEPTION, NAME_CTOR,
                           DESCR_CTOR_NOT_SERIALIZABLE_EXCEPTION, false);
        mv.visitInsn(ATHROW);
        mv.visitMaxs(-1, -1);
        mv.visitEnd();
    }

    
This class generates a method body which calls the lambda implementation
method, converting arguments, as needed.

/**
     * This class generates a method body which calls the lambda implementation
     * method, converting arguments, as needed.
     */
    private class ForwardingMethodGenerator extends TypeConvertingMethodAdapter {

        ForwardingMethodGenerator(MethodVisitor mv) {
            super(mv);
        }

        void generate(MethodType methodType) {
            visitCode();

            if (implKind == MethodHandleInfo.REF_newInvokeSpecial) {
                visitTypeInsn(NEW, implMethodClassName);
                visitInsn(DUP);
            }
            for (int i = 0; i < argNames.length; i++) {
                visitVarInsn(ALOAD, 0);
                visitFieldInsn(GETFIELD, lambdaClassName, argNames[i], argDescs[i]);
            }

            convertArgumentTypes(methodType);

            // Invoke the method we want to forward to
            visitMethodInsn(invocationOpcode(), implMethodClassName,
                            implMethodName, implMethodDesc,
                            implClass.isInterface());

            // Convert the return value (if any) and return it
            // Note: if adapting from non-void to void, the 'return'
            // instruction will pop the unneeded result
            Class<?> implReturnClass = implMethodType.returnType();
            Class<?> samReturnClass = methodType.returnType();
            convertType(implReturnClass, samReturnClass, samReturnClass);
            visitInsn(getReturnOpcode(samReturnClass));
            // Maxs computed by ClassWriter.COMPUTE_MAXS,these arguments ignored
            visitMaxs(-1, -1);
            visitEnd();
        }

        private void convertArgumentTypes(MethodType samType) {
            int lvIndex = 0;
            int samParametersLength = samType.parameterCount();
            int captureArity = invokedType.parameterCount();
            for (int i = 0; i < samParametersLength; i++) {
                Class<?> argType = samType.parameterType(i);
                visitVarInsn(getLoadOpcode(argType), lvIndex + 1);
                lvIndex += getParameterSize(argType);
                convertType(argType, implMethodType.parameterType(captureArity + i), instantiatedMethodType.parameterType(i));
            }
        }

        private int invocationOpcode() throws InternalError {
            switch (implKind) {
                case MethodHandleInfo.REF_invokeStatic:
                    return INVOKESTATIC;
                case MethodHandleInfo.REF_newInvokeSpecial:
                    return INVOKESPECIAL;
                 case MethodHandleInfo.REF_invokeVirtual:
                    return INVOKEVIRTUAL;
                case MethodHandleInfo.REF_invokeInterface:
                    return INVOKEINTERFACE;
                case MethodHandleInfo.REF_invokeSpecial:
                    return INVOKESPECIAL;
                default:
                    throw new InternalError("Unexpected invocation kind: " + implKind);
            }
        }
    }

    static int getParameterSize(Class<?> c) {
        if (c == Void.TYPE) {
            return 0;
        } else if (c == Long.TYPE || c == Double.TYPE) {
            return 2;
        }
        return 1;
    }

    static int getLoadOpcode(Class<?> c) {
        if(c == Void.TYPE) {
            throw new InternalError("Unexpected void type of load opcode");
        }
        return ILOAD + getOpcodeOffset(c);
    }

    static int getReturnOpcode(Class<?> c) {
        if(c == Void.TYPE) {
            return RETURN;
        }
        return IRETURN + getOpcodeOffset(c);
    }

    private static int getOpcodeOffset(Class<?> c) {
        if (c.isPrimitive()) {
            if (c == Long.TYPE) {
                return 1;
            } else if (c == Float.TYPE) {
                return 2;
            } else if (c == Double.TYPE) {
                return 3;
            }
            return 0;
        } else {
            return 4;
        }
    }

}