/*
 * Copyright (c) 2008, 2020, 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.access.JavaLangInvokeAccess;
import jdk.internal.access.SharedSecrets;
import jdk.internal.invoke.NativeEntryPoint;
import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.reflect.CallerSensitive;
import jdk.internal.reflect.Reflection;
import jdk.internal.vm.annotation.ForceInline;
import jdk.internal.vm.annotation.Hidden;
import jdk.internal.vm.annotation.Stable;
import sun.invoke.empty.Empty;
import sun.invoke.util.ValueConversions;
import sun.invoke.util.VerifyType;
import sun.invoke.util.Wrapper;

import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Array;
import java.nio.ByteOrder;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Stream;

import static java.lang.invoke.LambdaForm.*;
import static java.lang.invoke.MethodHandleStatics.*;
import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
import static jdk.internal.org.objectweb.asm.Opcodes.*;

Trusted implementation code for MethodHandle.
Author:
jrose/**
 * Trusted implementation code for MethodHandle.
 * @author jrose
 */
/*non-public*/
abstract class MethodHandleImpl {

    /// Factory methods to create method handles:

    static MethodHandle makeArrayElementAccessor(Class<?> arrayClass, ArrayAccess access) {
        if (arrayClass == Object[].class) {
            return ArrayAccess.objectAccessor(access);
        }
        if (!arrayClass.isArray())
            throw newIllegalArgumentException("not an array: "+arrayClass);
        MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass);
        int cacheIndex = ArrayAccess.cacheIndex(access);
        MethodHandle mh = cache[cacheIndex];
        if (mh != null)  return mh;
        mh = ArrayAccessor.getAccessor(arrayClass, access);
        MethodType correctType = ArrayAccessor.correctType(arrayClass, access);
        if (mh.type() != correctType) {
            assert(mh.type().parameterType(0) == Object[].class);
            /* if access == SET */ assert(access != ArrayAccess.SET || mh.type().parameterType(2) == Object.class);
            /* if access == GET */ assert(access != ArrayAccess.GET ||
                    (mh.type().returnType() == Object.class &&
                     correctType.parameterType(0).getComponentType() == correctType.returnType()));
            // safe to view non-strictly, because element type follows from array type
            mh = mh.viewAsType(correctType, false);
        }
        mh = makeIntrinsic(mh, ArrayAccess.intrinsic(access));
        // Atomically update accessor cache.
        synchronized(cache) {
            if (cache[cacheIndex] == null) {
                cache[cacheIndex] = mh;
            } else {
                // Throw away newly constructed accessor and use cached version.
                mh = cache[cacheIndex];
            }
        }
        return mh;
    }

    enum ArrayAccess {
        GET, SET, LENGTH;

        // As ArrayAccess and ArrayAccessor have a circular dependency, the ArrayAccess properties cannot be stored in
        // final fields.

        static String opName(ArrayAccess a) {
            switch (a) {
                case GET: return "getElement";
                case SET: return "setElement";
                case LENGTH: return "length";
            }
            throw unmatchedArrayAccess(a);
        }

        static MethodHandle objectAccessor(ArrayAccess a) {
            switch (a) {
                case GET: return ArrayAccessor.OBJECT_ARRAY_GETTER;
                case SET: return ArrayAccessor.OBJECT_ARRAY_SETTER;
                case LENGTH: return ArrayAccessor.OBJECT_ARRAY_LENGTH;
            }
            throw unmatchedArrayAccess(a);
        }

        static int cacheIndex(ArrayAccess a) {
            switch (a) {
                case GET: return ArrayAccessor.GETTER_INDEX;
                case SET: return ArrayAccessor.SETTER_INDEX;
                case LENGTH: return ArrayAccessor.LENGTH_INDEX;
            }
            throw unmatchedArrayAccess(a);
        }

        static Intrinsic intrinsic(ArrayAccess a) {
            switch (a) {
                case GET: return Intrinsic.ARRAY_LOAD;
                case SET: return Intrinsic.ARRAY_STORE;
                case LENGTH: return Intrinsic.ARRAY_LENGTH;
            }
            throw unmatchedArrayAccess(a);
        }
    }

    static InternalError unmatchedArrayAccess(ArrayAccess a) {
        return newInternalError("should not reach here (unmatched ArrayAccess: " + a + ")");
    }

    static final class ArrayAccessor {
        /// Support for array element and length access
        static final int GETTER_INDEX = 0, SETTER_INDEX = 1, LENGTH_INDEX = 2, INDEX_LIMIT = 3;
        static final ClassValue<MethodHandle[]> TYPED_ACCESSORS
                = new ClassValue<MethodHandle[]>() {
                    @Override
                    protected MethodHandle[] computeValue(Class<?> type) {
                        return new MethodHandle[INDEX_LIMIT];
                    }
                };
        static final MethodHandle OBJECT_ARRAY_GETTER, OBJECT_ARRAY_SETTER, OBJECT_ARRAY_LENGTH;
        static {
            MethodHandle[] cache = TYPED_ACCESSORS.get(Object[].class);
            cache[GETTER_INDEX] = OBJECT_ARRAY_GETTER = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.GET),    Intrinsic.ARRAY_LOAD);
            cache[SETTER_INDEX] = OBJECT_ARRAY_SETTER = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.SET),    Intrinsic.ARRAY_STORE);
            cache[LENGTH_INDEX] = OBJECT_ARRAY_LENGTH = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.LENGTH), Intrinsic.ARRAY_LENGTH);

            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_GETTER.internalMemberName()));
            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_SETTER.internalMemberName()));
            assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_LENGTH.internalMemberName()));
        }

        static int     getElementI(int[]     a, int i)            { return              a[i]; }
        static long    getElementJ(long[]    a, int i)            { return              a[i]; }
        static float   getElementF(float[]   a, int i)            { return              a[i]; }
        static double  getElementD(double[]  a, int i)            { return              a[i]; }
        static boolean getElementZ(boolean[] a, int i)            { return              a[i]; }
        static byte    getElementB(byte[]    a, int i)            { return              a[i]; }
        static short   getElementS(short[]   a, int i)            { return              a[i]; }
        static char    getElementC(char[]    a, int i)            { return              a[i]; }
        static Object  getElementL(Object[]  a, int i)            { return              a[i]; }

        static void    setElementI(int[]     a, int i, int     x) {              a[i] = x; }
        static void    setElementJ(long[]    a, int i, long    x) {              a[i] = x; }
        static void    setElementF(float[]   a, int i, float   x) {              a[i] = x; }
        static void    setElementD(double[]  a, int i, double  x) {              a[i] = x; }
        static void    setElementZ(boolean[] a, int i, boolean x) {              a[i] = x; }
        static void    setElementB(byte[]    a, int i, byte    x) {              a[i] = x; }
        static void    setElementS(short[]   a, int i, short   x) {              a[i] = x; }
        static void    setElementC(char[]    a, int i, char    x) {              a[i] = x; }
        static void    setElementL(Object[]  a, int i, Object  x) {              a[i] = x; }

        static int     lengthI(int[]     a)                       { return a.length; }
        static int     lengthJ(long[]    a)                       { return a.length; }
        static int     lengthF(float[]   a)                       { return a.length; }
        static int     lengthD(double[]  a)                       { return a.length; }
        static int     lengthZ(boolean[] a)                       { return a.length; }
        static int     lengthB(byte[]    a)                       { return a.length; }
        static int     lengthS(short[]   a)                       { return a.length; }
        static int     lengthC(char[]    a)                       { return a.length; }
        static int     lengthL(Object[]  a)                       { return a.length; }

        static String name(Class<?> arrayClass, ArrayAccess access) {
            Class<?> elemClass = arrayClass.getComponentType();
            if (elemClass == null)  throw newIllegalArgumentException("not an array", arrayClass);
            return ArrayAccess.opName(access) + Wrapper.basicTypeChar(elemClass);
        }
        static MethodType type(Class<?> arrayClass, ArrayAccess access) {
            Class<?> elemClass = arrayClass.getComponentType();
            Class<?> arrayArgClass = arrayClass;
            if (!elemClass.isPrimitive()) {
                arrayArgClass = Object[].class;
                elemClass = Object.class;
            }
            switch (access) {
                case GET:    return MethodType.methodType(elemClass,  arrayArgClass, int.class);
                case SET:    return MethodType.methodType(void.class, arrayArgClass, int.class, elemClass);
                case LENGTH: return MethodType.methodType(int.class,  arrayArgClass);
            }
            throw unmatchedArrayAccess(access);
        }
        static MethodType correctType(Class<?> arrayClass, ArrayAccess access) {
            Class<?> elemClass = arrayClass.getComponentType();
            switch (access) {
                case GET:    return MethodType.methodType(elemClass,  arrayClass, int.class);
                case SET:    return MethodType.methodType(void.class, arrayClass, int.class, elemClass);
                case LENGTH: return MethodType.methodType(int.class,  arrayClass);
            }
            throw unmatchedArrayAccess(access);
        }
        static MethodHandle getAccessor(Class<?> arrayClass, ArrayAccess access) {
            String     name = name(arrayClass, access);
            MethodType type = type(arrayClass, access);
            try {
                return IMPL_LOOKUP.findStatic(ArrayAccessor.class, name, type);
            } catch (ReflectiveOperationException ex) {
                throw uncaughtException(ex);
            }
        }
    }

    
Create a JVM-level adapter method handle to conform the given method
handle to the similar newType, using only pairwise argument conversions.
For each argument, convert incoming argument to the exact type needed.
The argument conversions allowed are casting, boxing and unboxing,
integral widening or narrowing, and floating point widening or narrowing.
Params:
srcType – required call type
target – original method handle
strict – if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed
monobox – if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)
Returns:
an adapter to the original handle with the desired new type,
         or the original target if the types are already identical
         or null if the adaptation cannot be made/**
     * Create a JVM-level adapter method handle to conform the given method
     * handle to the similar newType, using only pairwise argument conversions.
     * For each argument, convert incoming argument to the exact type needed.
     * The argument conversions allowed are casting, boxing and unboxing,
     * integral widening or narrowing, and floating point widening or narrowing.
     * @param srcType required call type
     * @param target original method handle
     * @param strict if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed
     * @param monobox if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)
     * @return an adapter to the original handle with the desired new type,
     *          or the original target if the types are already identical
     *          or null if the adaptation cannot be made
     */
    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
                                            boolean strict, boolean monobox) {
        MethodType dstType = target.type();
        if (srcType == dstType)
            return target;
        return makePairwiseConvertByEditor(target, srcType, strict, monobox);
    }

    private static int countNonNull(Object[] array) {
        int count = 0;
        if (array != null) {
            for (Object x : array) {
                if (x != null) ++count;
            }
        }
        return count;
    }

    static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType srcType,
                                                    boolean strict, boolean monobox) {
        // In method types arguments start at index 0, while the LF
        // editor have the MH receiver at position 0 - adjust appropriately.
        final int MH_RECEIVER_OFFSET = 1;
        Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);
        int convCount = countNonNull(convSpecs);
        if (convCount == 0)
            return target.viewAsType(srcType, strict);
        MethodType basicSrcType = srcType.basicType();
        MethodType midType = target.type().basicType();
        BoundMethodHandle mh = target.rebind();

        // Match each unique conversion to the positions at which it is to be applied
        var convSpecMap = new HashMap<Object, int[]>(((4 * convCount) / 3) + 1);
        for (int i = 0; i < convSpecs.length - MH_RECEIVER_OFFSET; i++) {
            Object convSpec = convSpecs[i];
            if (convSpec == null) continue;
            int[] positions = convSpecMap.get(convSpec);
            if (positions == null) {
                positions = new int[] { i + MH_RECEIVER_OFFSET };
            } else {
                positions = Arrays.copyOf(positions, positions.length + 1);
                positions[positions.length - 1] = i + MH_RECEIVER_OFFSET;
            }
            convSpecMap.put(convSpec, positions);
        }
        for (var entry : convSpecMap.entrySet()) {
            Object convSpec = entry.getKey();

            MethodHandle fn;
            if (convSpec instanceof Class) {
                fn = getConstantHandle(MH_cast).bindTo(convSpec);
            } else {
                fn = (MethodHandle) convSpec;
            }
            int[] positions = entry.getValue();
            Class<?> newType = basicSrcType.parameterType(positions[0] - MH_RECEIVER_OFFSET);
            BasicType newBasicType = BasicType.basicType(newType);
            convCount -= positions.length;
            if (convCount == 0) {
                midType = srcType;
            } else {
                Class<?>[] ptypes = midType.ptypes().clone();
                for (int pos : positions) {
                    ptypes[pos - 1] = newType;
                }
                midType = MethodType.makeImpl(midType.rtype(), ptypes, true);
            }
            LambdaForm form2;
            if (positions.length > 1) {
                form2 = mh.editor().filterRepeatedArgumentForm(newBasicType, positions);
            } else {
                form2 = mh.editor().filterArgumentForm(positions[0], newBasicType);
            }
            mh = mh.copyWithExtendL(midType, form2, fn);
        }
        Object convSpec = convSpecs[convSpecs.length - 1];
        if (convSpec != null) {
            MethodHandle fn;
            if (convSpec instanceof Class) {
                if (convSpec == void.class)
                    fn = null;
                else
                    fn = getConstantHandle(MH_cast).bindTo(convSpec);
            } else {
                fn = (MethodHandle) convSpec;
            }
            Class<?> newType = basicSrcType.returnType();
            assert(--convCount == 0);
            midType = srcType;
            if (fn != null) {
                mh = mh.rebind();  // rebind if too complex
                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), false);
                mh = mh.copyWithExtendL(midType, form2, fn);
            } else {
                LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), true);
                mh = mh.copyWith(midType, form2);
            }
        }
        assert(convCount == 0);
        assert(mh.type().equals(srcType));
        return mh;
    }

    static Object[] computeValueConversions(MethodType srcType, MethodType dstType,
                                            boolean strict, boolean monobox) {
        final int INARG_COUNT = srcType.parameterCount();
        Object[] convSpecs = null;
        for (int i = 0; i <= INARG_COUNT; i++) {
            boolean isRet = (i == INARG_COUNT);
            Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);
            Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);
            if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {
                if (convSpecs == null) {
                    convSpecs = new Object[INARG_COUNT + 1];
                }
                convSpecs[i] = valueConversion(src, dst, strict, monobox);
            }
        }
        return convSpecs;
    }
    static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
                                            boolean strict) {
        return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);
    }

    
Find a conversion function from the given source to the given destination.
This conversion function will be used as a LF NamedFunction.
Return a Class object if a simple cast is needed.
Return void.class if void is involved.
/**
     * Find a conversion function from the given source to the given destination.
     * This conversion function will be used as a LF NamedFunction.
     * Return a Class object if a simple cast is needed.
     * Return void.class if void is involved.
     */
    static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {
        assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility
        if (dst == void.class)
            return dst;
        MethodHandle fn;
        if (src.isPrimitive()) {
            if (src == void.class) {
                return void.class;  // caller must recognize this specially
            } else if (dst.isPrimitive()) {
                // Examples: int->byte, byte->int, boolean->int (!strict)
                fn = ValueConversions.convertPrimitive(src, dst);
            } else {
                // Examples: int->Integer, boolean->Object, float->Number
                Wrapper wsrc = Wrapper.forPrimitiveType(src);
                fn = ValueConversions.boxExact(wsrc);
                assert(fn.type().parameterType(0) == wsrc.primitiveType());
                assert(fn.type().returnType() == wsrc.wrapperType());
                if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {
                    // Corner case, such as int->Long, which will probably fail.
                    MethodType mt = MethodType.methodType(dst, src);
                    if (strict)
                        fn = fn.asType(mt);
                    else
                        fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);
                }
            }
        } else if (dst.isPrimitive()) {
            Wrapper wdst = Wrapper.forPrimitiveType(dst);
            if (monobox || src == wdst.wrapperType()) {
                // Use a strongly-typed unboxer, if possible.
                fn = ValueConversions.unboxExact(wdst, strict);
            } else {
                // Examples:  Object->int, Number->int, Comparable->int, Byte->int
                // must include additional conversions
                // src must be examined at runtime, to detect Byte, Character, etc.
                fn = (strict
                        ? ValueConversions.unboxWiden(wdst)
                        : ValueConversions.unboxCast(wdst));
            }
        } else {
            // Simple reference conversion.
            // Note:  Do not check for a class hierarchy relation
            // between src and dst.  In all cases a 'null' argument
            // will pass the cast conversion.
            return dst;
        }
        assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);
        return fn;
    }

    static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {
        MethodType type = target.type();
        int last = type.parameterCount() - 1;
        if (type.parameterType(last) != arrayType)
            target = target.asType(type.changeParameterType(last, arrayType));
        target = target.asFixedArity();  // make sure this attribute is turned off
        return new AsVarargsCollector(target, arrayType);
    }

    private static final class AsVarargsCollector extends DelegatingMethodHandle {
        private final MethodHandle target;
        private final Class<?> arrayType;
        private @Stable MethodHandle asCollectorCache;

        AsVarargsCollector(MethodHandle target, Class<?> arrayType) {
            this(target.type(), target, arrayType);
        }
        AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {
            super(type, target);
            this.target = target;
            this.arrayType = arrayType;
        }

        @Override
        public boolean isVarargsCollector() {
            return true;
        }

        @Override
        protected MethodHandle getTarget() {
            return target;
        }

        @Override
        public MethodHandle asFixedArity() {
            return target;
        }

        @Override
        MethodHandle setVarargs(MemberName member) {
            if (member.isVarargs())  return this;
            return asFixedArity();
        }

        @Override
        public MethodHandle withVarargs(boolean makeVarargs) {
            if (makeVarargs)  return this;
            return asFixedArity();
        }

        @Override
        public MethodHandle asTypeUncached(MethodType newType) {
            MethodType type = this.type();
            int collectArg = type.parameterCount() - 1;
            int newArity = newType.parameterCount();
            if (newArity == collectArg+1 &&
                type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {
                // if arity and trailing parameter are compatible, do normal thing
                return asTypeCache = asFixedArity().asType(newType);
            }
            // check cache
            MethodHandle acc = asCollectorCache;
            if (acc != null && acc.type().parameterCount() == newArity)
                return asTypeCache = acc.asType(newType);
            // build and cache a collector
            int arrayLength = newArity - collectArg;
            MethodHandle collector;
            try {
                collector = asFixedArity().asCollector(arrayType, arrayLength);
                assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;
            } catch (IllegalArgumentException ex) {
                throw new WrongMethodTypeException("cannot build collector", ex);
            }
            asCollectorCache = collector;
            return asTypeCache = collector.asType(newType);
        }

        @Override
        boolean viewAsTypeChecks(MethodType newType, boolean strict) {
            super.viewAsTypeChecks(newType, true);
            if (strict) return true;
            // extra assertion for non-strict checks:
            assert (type().lastParameterType().getComponentType()
                    .isAssignableFrom(
                            newType.lastParameterType().getComponentType()))
                    : Arrays.asList(this, newType);
            return true;
        }

        @Override
        public Object invokeWithArguments(Object... arguments) throws Throwable {
            MethodType type = this.type();
            int argc;
            final int MAX_SAFE = 127;  // 127 longs require 254 slots, which is safe to spread
            if (arguments == null
                    || (argc = arguments.length) <= MAX_SAFE
                    || argc < type.parameterCount()) {
                return super.invokeWithArguments(arguments);
            }

            // a jumbo invocation requires more explicit reboxing of the trailing arguments
            int uncollected = type.parameterCount() - 1;
            Class<?> elemType = arrayType.getComponentType();
            int collected = argc - uncollected;
            Object collArgs = (elemType == Object.class)
                ? new Object[collected] : Array.newInstance(elemType, collected);
            if (!elemType.isPrimitive()) {
                // simple cast:  just do some casting
                try {
                    System.arraycopy(arguments, uncollected, collArgs, 0, collected);
                } catch (ArrayStoreException ex) {
                    return super.invokeWithArguments(arguments);
                }
            } else {
                // corner case of flat array requires reflection (or specialized copy loop)
                MethodHandle arraySetter = MethodHandles.arrayElementSetter(arrayType);
                try {
                    for (int i = 0; i < collected; i++) {
                        arraySetter.invoke(collArgs, i, arguments[uncollected + i]);
                    }
                } catch (WrongMethodTypeException|ClassCastException ex) {
                    return super.invokeWithArguments(arguments);
                }
            }

            // chop the jumbo list down to size and call in non-varargs mode
            Object[] newArgs = new Object[uncollected + 1];
            System.arraycopy(arguments, 0, newArgs, 0, uncollected);
            newArgs[uncollected] = collArgs;
            return asFixedArity().invokeWithArguments(newArgs);
        }
    }

    
Factory method:  Spread selected argument. /** Factory method:  Spread selected argument. */
    static MethodHandle makeSpreadArguments(MethodHandle target,
                                            Class<?> spreadArgType, int spreadArgPos, int spreadArgCount) {
        MethodType targetType = target.type();

        for (int i = 0; i < spreadArgCount; i++) {
            Class<?> arg = VerifyType.spreadArgElementType(spreadArgType, i);
            if (arg == null)  arg = Object.class;
            targetType = targetType.changeParameterType(spreadArgPos + i, arg);
        }
        target = target.asType(targetType);

        MethodType srcType = targetType
                .replaceParameterTypes(spreadArgPos, spreadArgPos + spreadArgCount, spreadArgType);
        // Now build a LambdaForm.
        MethodType lambdaType = srcType.invokerType();
        Name[] names = arguments(spreadArgCount + 2, lambdaType);
        int nameCursor = lambdaType.parameterCount();
        int[] indexes = new int[targetType.parameterCount()];

        for (int i = 0, argIndex = 1; i < targetType.parameterCount() + 1; i++, argIndex++) {
            Class<?> src = lambdaType.parameterType(i);
            if (i == spreadArgPos) {
                // Spread the array.
                MethodHandle aload = MethodHandles.arrayElementGetter(spreadArgType);
                Name array = names[argIndex];
                names[nameCursor++] = new Name(getFunction(NF_checkSpreadArgument), array, spreadArgCount);
                for (int j = 0; j < spreadArgCount; i++, j++) {
                    indexes[i] = nameCursor;
                    names[nameCursor++] = new Name(new NamedFunction(aload, Intrinsic.ARRAY_LOAD), array, j);
                }
            } else if (i < indexes.length) {
                indexes[i] = argIndex;
            }
        }
        assert(nameCursor == names.length-1);  // leave room for the final call

        // Build argument array for the call.
        Name[] targetArgs = new Name[targetType.parameterCount()];
        for (int i = 0; i < targetType.parameterCount(); i++) {
            int idx = indexes[i];
            targetArgs[i] = names[idx];
        }
        names[names.length - 1] = new Name(target, (Object[]) targetArgs);

        LambdaForm form = new LambdaForm(lambdaType.parameterCount(), names, Kind.SPREAD);
        return SimpleMethodHandle.make(srcType, form);
    }

    static void checkSpreadArgument(Object av, int n) {
        if (av == null && n == 0) {
            return;
        } else if (av == null) {
            throw new NullPointerException("null array reference");
        } else if (av instanceof Object[]) {
            int len = ((Object[])av).length;
            if (len == n)  return;
        } else {
            int len = java.lang.reflect.Array.getLength(av);
            if (len == n)  return;
        }
        // fall through to error:
        throw newIllegalArgumentException("array is not of length "+n);
    }

    
Factory method:  Collect or filter selected argument(s). /** Factory method:  Collect or filter selected argument(s). */
    static MethodHandle makeCollectArguments(MethodHandle target,
                MethodHandle collector, int collectArgPos, boolean retainOriginalArgs) {
        MethodType targetType = target.type();          // (a..., c, [b...])=>r
        MethodType collectorType = collector.type();    // (b...)=>c
        int collectArgCount = collectorType.parameterCount();
        Class<?> collectValType = collectorType.returnType();
        int collectValCount = (collectValType == void.class ? 0 : 1);
        MethodType srcType = targetType                 // (a..., [b...])=>r
                .dropParameterTypes(collectArgPos, collectArgPos+collectValCount);
        if (!retainOriginalArgs) {                      // (a..., b...)=>r
            srcType = srcType.insertParameterTypes(collectArgPos, collectorType.parameterArray());
        }
        // in  arglist: [0: ...keep1 | cpos: collect...  | cpos+cacount: keep2... ]
        // out arglist: [0: ...keep1 | cpos: collectVal? | cpos+cvcount: keep2... ]
        // out(retain): [0: ...keep1 | cpos: cV? coll... | cpos+cvc+cac: keep2... ]

        // Now build a LambdaForm.
        MethodType lambdaType = srcType.invokerType();
        Name[] names = arguments(2, lambdaType);
        final int collectNamePos = names.length - 2;
        final int targetNamePos  = names.length - 1;

        Name[] collectorArgs = Arrays.copyOfRange(names, 1 + collectArgPos, 1 + collectArgPos + collectArgCount);
        names[collectNamePos] = new Name(collector, (Object[]) collectorArgs);

        // Build argument array for the target.
        // Incoming LF args to copy are: [ (mh) headArgs collectArgs tailArgs ].
        // Output argument array is [ headArgs (collectVal)? (collectArgs)? tailArgs ].
        Name[] targetArgs = new Name[targetType.parameterCount()];
        int inputArgPos  = 1;  // incoming LF args to copy to target
        int targetArgPos = 0;  // fill pointer for targetArgs
        int chunk = collectArgPos;  // |headArgs|
        System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
        inputArgPos  += chunk;
        targetArgPos += chunk;
        if (collectValType != void.class) {
            targetArgs[targetArgPos++] = names[collectNamePos];
        }
        chunk = collectArgCount;
        if (retainOriginalArgs) {
            System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
            targetArgPos += chunk;   // optionally pass on the collected chunk
        }
        inputArgPos += chunk;
        chunk = targetArgs.length - targetArgPos;  // all the rest
        System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
        assert(inputArgPos + chunk == collectNamePos);  // use of rest of input args also
        names[targetNamePos] = new Name(target, (Object[]) targetArgs);

        LambdaForm form = new LambdaForm(lambdaType.parameterCount(), names, Kind.COLLECT);
        return SimpleMethodHandle.make(srcType, form);
    }

    @Hidden
    static MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {
        if (testResult) {
            return target;
        } else {
            return fallback;
        }
    }

    // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.
    @Hidden
    @jdk.internal.vm.annotation.IntrinsicCandidate
    static boolean profileBoolean(boolean result, int[] counters) {
        // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.
        int idx = result ? 1 : 0;
        try {
            counters[idx] = Math.addExact(counters[idx], 1);
        } catch (ArithmeticException e) {
            // Avoid continuous overflow by halving the problematic count.
            counters[idx] = counters[idx] / 2;
        }
        return result;
    }

    // Intrinsified by C2. Returns true if obj is a compile-time constant.
    @Hidden
    @jdk.internal.vm.annotation.IntrinsicCandidate
    static boolean isCompileConstant(Object obj) {
        return false;
    }

    static MethodHandle makeGuardWithTest(MethodHandle test,
                                   MethodHandle target,
                                   MethodHandle fallback) {
        MethodType type = target.type();
        assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));
        MethodType basicType = type.basicType();
        LambdaForm form = makeGuardWithTestForm(basicType);
        BoundMethodHandle mh;
        try {
            if (PROFILE_GWT) {
                int[] counts = new int[2];
                mh = (BoundMethodHandle)
                        BoundMethodHandle.speciesData_LLLL().factory().invokeBasic(type, form,
                                (Object) test, (Object) profile(target), (Object) profile(fallback), counts);
            } else {
                mh = (BoundMethodHandle)
                        BoundMethodHandle.speciesData_LLL().factory().invokeBasic(type, form,
                                (Object) test, (Object) profile(target), (Object) profile(fallback));
            }
        } catch (Throwable ex) {
            throw uncaughtException(ex);
        }
        assert(mh.type() == type);
        return mh;
    }


    static MethodHandle profile(MethodHandle target) {
        if (DONT_INLINE_THRESHOLD >= 0) {
            return makeBlockInliningWrapper(target);
        } else {
            return target;
        }
    }

    
Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.
Corresponding LambdaForm has @DontInline when compiled into bytecode.
/**
     * Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.
     * Corresponding LambdaForm has @DontInline when compiled into bytecode.
     */
    static MethodHandle makeBlockInliningWrapper(MethodHandle target) {
        LambdaForm lform;
        if (DONT_INLINE_THRESHOLD > 0) {
            lform = Makers.PRODUCE_BLOCK_INLINING_FORM.apply(target);
        } else {
            lform = Makers.PRODUCE_REINVOKER_FORM.apply(target);
        }
        return new CountingWrapper(target, lform,
                Makers.PRODUCE_BLOCK_INLINING_FORM, Makers.PRODUCE_REINVOKER_FORM,
                                   DONT_INLINE_THRESHOLD);
    }

    private final static class Makers {
        
Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle /** Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle */
        static final Function<MethodHandle, LambdaForm> PRODUCE_BLOCK_INLINING_FORM = new Function<MethodHandle, LambdaForm>() {
            @Override
            public LambdaForm apply(MethodHandle target) {
                return DelegatingMethodHandle.makeReinvokerForm(target,
                                   MethodTypeForm.LF_DELEGATE_BLOCK_INLINING, CountingWrapper.class, false,
                                   DelegatingMethodHandle.NF_getTarget, CountingWrapper.NF_maybeStopCounting);
            }
        };

        
Constructs simple reinvoker lambda form for a particular method handle /** Constructs simple reinvoker lambda form for a particular method handle */
        static final Function<MethodHandle, LambdaForm> PRODUCE_REINVOKER_FORM = new Function<MethodHandle, LambdaForm>() {
            @Override
            public LambdaForm apply(MethodHandle target) {
                return DelegatingMethodHandle.makeReinvokerForm(target,
                        MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, DelegatingMethodHandle.NF_getTarget);
            }
        };

        
Maker of type-polymorphic varargs /** Maker of type-polymorphic varargs */
        static final ClassValue<MethodHandle[]> TYPED_COLLECTORS = new ClassValue<MethodHandle[]>() {
            @Override
            protected MethodHandle[] computeValue(Class<?> type) {
                return new MethodHandle[MAX_JVM_ARITY + 1];
            }
        };
    }

    
Counting method handle. It has 2 states: counting and non-counting.
It is in counting state for the first n invocations and then transitions to non-counting state.
Behavior in counting and non-counting states is determined by lambda forms produced by
countingFormProducer & nonCountingFormProducer respectively.
/**
     * Counting method handle. It has 2 states: counting and non-counting.
     * It is in counting state for the first n invocations and then transitions to non-counting state.
     * Behavior in counting and non-counting states is determined by lambda forms produced by
     * countingFormProducer & nonCountingFormProducer respectively.
     */
    static class CountingWrapper extends DelegatingMethodHandle {
        private final MethodHandle target;
        private int count;
        private Function<MethodHandle, LambdaForm> countingFormProducer;
        private Function<MethodHandle, LambdaForm> nonCountingFormProducer;
        private volatile boolean isCounting;

        private CountingWrapper(MethodHandle target, LambdaForm lform,
                                Function<MethodHandle, LambdaForm> countingFromProducer,
                                Function<MethodHandle, LambdaForm> nonCountingFormProducer,
                                int count) {
            super(target.type(), lform);
            this.target = target;
            this.count = count;
            this.countingFormProducer = countingFromProducer;
            this.nonCountingFormProducer = nonCountingFormProducer;
            this.isCounting = (count > 0);
        }

        @Hidden
        @Override
        protected MethodHandle getTarget() {
            return target;
        }

        @Override
        public MethodHandle asTypeUncached(MethodType newType) {
            MethodHandle newTarget = target.asType(newType);
            MethodHandle wrapper;
            if (isCounting) {
                LambdaForm lform;
                lform = countingFormProducer.apply(newTarget);
                wrapper = new CountingWrapper(newTarget, lform, countingFormProducer, nonCountingFormProducer, DONT_INLINE_THRESHOLD);
            } else {
                wrapper = newTarget; // no need for a counting wrapper anymore
            }
            return (asTypeCache = wrapper);
        }

        boolean countDown() {
            int c = count;
            target.maybeCustomize(); // customize if counting happens for too long
            if (c <= 1) {
                // Try to limit number of updates. MethodHandle.updateForm() doesn't guarantee LF update visibility.
                if (isCounting) {
                    isCounting = false;
                    return true;
                } else {
                    return false;
                }
            } else {
                count = c - 1;
                return false;
            }
        }

        @Hidden
        static void maybeStopCounting(Object o1) {
             final CountingWrapper wrapper = (CountingWrapper) o1;
             if (wrapper.countDown()) {
                 // Reached invocation threshold. Replace counting behavior with a non-counting one.
                 wrapper.updateForm(new Function<>() {
                     public LambdaForm apply(LambdaForm oldForm) {
                         LambdaForm lform = wrapper.nonCountingFormProducer.apply(wrapper.target);
                         lform.compileToBytecode(); // speed up warmup by avoiding LF interpretation again after transition
                         return lform;
                     }});
             }
        }

        static final NamedFunction NF_maybeStopCounting;
        static {
            Class<?> THIS_CLASS = CountingWrapper.class;
            try {
                NF_maybeStopCounting = new NamedFunction(THIS_CLASS.getDeclaredMethod("maybeStopCounting", Object.class));
            } catch (ReflectiveOperationException ex) {
                throw newInternalError(ex);
            }
        }
    }

    static LambdaForm makeGuardWithTestForm(MethodType basicType) {
        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWT);
        if (lform != null)  return lform;
        final int THIS_MH      = 0;  // the BMH_LLL
        final int ARG_BASE     = 1;  // start of incoming arguments
        final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
        int nameCursor = ARG_LIMIT;
        final int GET_TEST     = nameCursor++;
        final int GET_TARGET   = nameCursor++;
        final int GET_FALLBACK = nameCursor++;
        final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;
        final int CALL_TEST    = nameCursor++;
        final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;
        final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST
        final int SELECT_ALT   = nameCursor++;
        final int CALL_TARGET  = nameCursor++;
        assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative

        MethodType lambdaType = basicType.invokerType();
        Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

        BoundMethodHandle.SpeciesData data =
                (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()
                                     : BoundMethodHandle.speciesData_LLL();
        names[THIS_MH] = names[THIS_MH].withConstraint(data);
        names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);
        names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);
        names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);
        if (GET_COUNTERS != -1) {
            names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);
        }
        Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);

        // call test
        MethodType testType = basicType.changeReturnType(boolean.class).basicType();
        invokeArgs[0] = names[GET_TEST];
        names[CALL_TEST] = new Name(testType, invokeArgs);

        // profile branch
        if (PROFILE != -1) {
            names[PROFILE] = new Name(getFunction(NF_profileBoolean), names[CALL_TEST], names[GET_COUNTERS]);
        }
        // call selectAlternative
        names[SELECT_ALT] = new Name(new NamedFunction(getConstantHandle(MH_selectAlternative), Intrinsic.SELECT_ALTERNATIVE), names[TEST], names[GET_TARGET], names[GET_FALLBACK]);

        // call target or fallback
        invokeArgs[0] = names[SELECT_ALT];
        names[CALL_TARGET] = new Name(basicType, invokeArgs);

        lform = new LambdaForm(lambdaType.parameterCount(), names, /*forceInline=*/true, Kind.GUARD);

        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);
    }

    
The LambdaForm shape for catchException combinator is the following:

 guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{
   t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);
   t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);
   t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);
   t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);
   t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);
   t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);
   t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);
  t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}

argL0 and argL2 are target and catcher method handles. argL1 is exception class.
argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]
(ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).
Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms
among catchException combinators with the same basic type.
/**
     * The LambdaForm shape for catchException combinator is the following:
     * <blockquote><pre>{@code
     *  guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{
     *    t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);
     *    t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);
     *    t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);
     *    t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);
     *    t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);
     *    t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);
     *    t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);
     *   t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}
     * }</pre></blockquote>
     *
     * argL0 and argL2 are target and catcher method handles. argL1 is exception class.
     * argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]
     * (ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).
     *
     * Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms
     * among catchException combinators with the same basic type.
     */
    private static LambdaForm makeGuardWithCatchForm(MethodType basicType) {
        MethodType lambdaType = basicType.invokerType();

        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWC);
        if (lform != null) {
            return lform;
        }
        final int THIS_MH      = 0;  // the BMH_LLLLL
        final int ARG_BASE     = 1;  // start of incoming arguments
        final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();

        int nameCursor = ARG_LIMIT;
        final int GET_TARGET       = nameCursor++;
        final int GET_CLASS        = nameCursor++;
        final int GET_CATCHER      = nameCursor++;
        final int GET_COLLECT_ARGS = nameCursor++;
        final int GET_UNBOX_RESULT = nameCursor++;
        final int BOXED_ARGS       = nameCursor++;
        final int TRY_CATCH        = nameCursor++;
        final int UNBOX_RESULT     = nameCursor++;

        Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
        names[THIS_MH]          = names[THIS_MH].withConstraint(data);
        names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
        names[GET_CLASS]        = new Name(data.getterFunction(1), names[THIS_MH]);
        names[GET_CATCHER]      = new Name(data.getterFunction(2), names[THIS_MH]);
        names[GET_COLLECT_ARGS] = new Name(data.getterFunction(3), names[THIS_MH]);
        names[GET_UNBOX_RESULT] = new Name(data.getterFunction(4), names[THIS_MH]);

        // FIXME: rework argument boxing/result unboxing logic for LF interpretation

        // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
        MethodType collectArgsType = basicType.changeReturnType(Object.class);
        MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
        Object[] args = new Object[invokeBasic.type().parameterCount()];
        args[0] = names[GET_COLLECT_ARGS];
        System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
        names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.GUARD_WITH_CATCH), args);

        // t_{i+1}:L=MethodHandleImpl.guardWithCatch(target:L,exType:L,catcher:L,t_{i}:L);
        Object[] gwcArgs = new Object[] {names[GET_TARGET], names[GET_CLASS], names[GET_CATCHER], names[BOXED_ARGS]};
        names[TRY_CATCH] = new Name(getFunction(NF_guardWithCatch), gwcArgs);

        // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
        MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
        Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_CATCH]};
        names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);

        lform = new LambdaForm(lambdaType.parameterCount(), names, Kind.GUARD_WITH_CATCH);

        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
    }

    static MethodHandle makeGuardWithCatch(MethodHandle target,
                                    Class<? extends Throwable> exType,
                                    MethodHandle catcher) {
        MethodType type = target.type();
        LambdaForm form = makeGuardWithCatchForm(type.basicType());

        // Prepare auxiliary method handles used during LambdaForm interpretation.
        // Box arguments and wrap them into Object[]: ValueConversions.array().
        MethodType varargsType = type.changeReturnType(Object[].class);
        MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
        MethodHandle unboxResult = unboxResultHandle(type.returnType());

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
        BoundMethodHandle mh;
        try {
            mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) target, (Object) exType,
                    (Object) catcher, (Object) collectArgs, (Object) unboxResult);
        } catch (Throwable ex) {
            throw uncaughtException(ex);
        }
        assert(mh.type() == type);
        return mh;
    }

    
Intrinsified during LambdaForm compilation (see emitGuardWithCatch). /**
     * Intrinsified during LambdaForm compilation
     * (see {@link InvokerBytecodeGenerator#emitGuardWithCatch emitGuardWithCatch}).
     */
    @Hidden
    static Object guardWithCatch(MethodHandle target, Class<? extends Throwable> exType, MethodHandle catcher,
                                 Object... av) throws Throwable {
        // Use asFixedArity() to avoid unnecessary boxing of last argument for VarargsCollector case.
        try {
            return target.asFixedArity().invokeWithArguments(av);
        } catch (Throwable t) {
            if (!exType.isInstance(t)) throw t;
            return catcher.asFixedArity().invokeWithArguments(prepend(av, t));
        }
    }

    
Prepend elements to an array. /** Prepend elements to an array. */
    @Hidden
    private static Object[] prepend(Object[] array, Object... elems) {
        int nArray = array.length;
        int nElems = elems.length;
        Object[] newArray = new Object[nArray + nElems];
        System.arraycopy(elems, 0, newArray, 0, nElems);
        System.arraycopy(array, 0, newArray, nElems, nArray);
        return newArray;
    }

    static MethodHandle throwException(MethodType type) {
        assert(Throwable.class.isAssignableFrom(type.parameterType(0)));
        int arity = type.parameterCount();
        if (arity > 1) {
            MethodHandle mh = throwException(type.dropParameterTypes(1, arity));
            mh = MethodHandles.dropArguments(mh, 1, Arrays.copyOfRange(type.parameterArray(), 1, arity));
            return mh;
        }
        return makePairwiseConvert(getFunction(NF_throwException).resolvedHandle(), type, false, true);
    }

    static <T extends Throwable> Empty throwException(T t) throws T { throw t; }

    static MethodHandle[] FAKE_METHOD_HANDLE_INVOKE = new MethodHandle[2];
    static MethodHandle fakeMethodHandleInvoke(MemberName method) {
        int idx;
        assert(method.isMethodHandleInvoke());
        switch (method.getName()) {
        case "invoke":       idx = 0; break;
        case "invokeExact":  idx = 1; break;
        default:             throw new InternalError(method.getName());
        }
        MethodHandle mh = FAKE_METHOD_HANDLE_INVOKE[idx];
        if (mh != null)  return mh;
        MethodType type = MethodType.methodType(Object.class, UnsupportedOperationException.class,
                                                MethodHandle.class, Object[].class);
        mh = throwException(type);
        mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke MethodHandle"));
        if (!method.getInvocationType().equals(mh.type()))
            throw new InternalError(method.toString());
        mh = mh.withInternalMemberName(method, false);
        mh = mh.withVarargs(true);
        assert(method.isVarargs());
        FAKE_METHOD_HANDLE_INVOKE[idx] = mh;
        return mh;
    }
    static MethodHandle fakeVarHandleInvoke(MemberName method) {
        // TODO caching, is it necessary?
        MethodType type = MethodType.methodType(method.getReturnType(), UnsupportedOperationException.class,
                                                VarHandle.class, Object[].class);
        MethodHandle mh = throwException(type);
        mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke VarHandle"));
        if (!method.getInvocationType().equals(mh.type()))
            throw new InternalError(method.toString());
        mh = mh.withInternalMemberName(method, false);
        mh = mh.asVarargsCollector(Object[].class);
        assert(method.isVarargs());
        return mh;
    }

    
Create an alias for the method handle which, when called,
appears to be called from the same class loader and protection domain
as hostClass.
This is an expensive no-op unless the method which is called
is sensitive to its caller.  A small number of system methods
are in this category, including Class.forName and Method.invoke.
/**
     * Create an alias for the method handle which, when called,
     * appears to be called from the same class loader and protection domain
     * as hostClass.
     * This is an expensive no-op unless the method which is called
     * is sensitive to its caller.  A small number of system methods
     * are in this category, including Class.forName and Method.invoke.
     */
    static MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
        return BindCaller.bindCaller(mh, hostClass);
    }

    // Put the whole mess into its own nested class.
    // That way we can lazily load the code and set up the constants.
    private static class BindCaller {
        private static MethodType INVOKER_MT = MethodType.methodType(Object.class, MethodHandle.class, Object[].class);

        static MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
            // Code in the boot layer should now be careful while creating method handles or
            // functional interface instances created from method references to @CallerSensitive  methods,
            // it needs to be ensured the handles or interface instances are kept safe and are not passed
            // from the boot layer to untrusted code.
            if (hostClass == null
                ||    (hostClass.isArray() ||
                       hostClass.isPrimitive() ||
                       hostClass.getName().startsWith("java.lang.invoke."))) {
                throw new InternalError();  // does not happen, and should not anyway
            }
            // For simplicity, convert mh to a varargs-like method.
            MethodHandle vamh = prepareForInvoker(mh);
            // Cache the result of makeInjectedInvoker once per argument class.
            MethodHandle bccInvoker = CV_makeInjectedInvoker.get(hostClass);
            return restoreToType(bccInvoker.bindTo(vamh), mh, hostClass);
        }

        private static MethodHandle makeInjectedInvoker(Class<?> targetClass) {
            try {
                /*
                 * The invoker class defined to the same class loader as the lookup class
                 * but in an unnamed package so that the class bytes can be cached and
                 * reused for any @CSM.
                 *
                 * @CSM must be public and exported if called by any module.
                 */
                String name = targetClass.getName() + "$$InjectedInvoker";
                if (targetClass.isHidden()) {
                    // use the original class name
                    name = name.replace('/', '_');
                }
                Class<?> invokerClass = new Lookup(targetClass)
                        .makeHiddenClassDefiner(name, INJECTED_INVOKER_TEMPLATE)
                        .defineClass(true);
                assert checkInjectedInvoker(targetClass, invokerClass);
                return IMPL_LOOKUP.findStatic(invokerClass, "invoke_V", INVOKER_MT);
            } catch (ReflectiveOperationException ex) {
                throw uncaughtException(ex);
            }
        }

        private static ClassValue<MethodHandle> CV_makeInjectedInvoker = new ClassValue<MethodHandle>() {
            @Override protected MethodHandle computeValue(Class<?> hostClass) {
                return makeInjectedInvoker(hostClass);
            }
        };

        // Adapt mh so that it can be called directly from an injected invoker:
        private static MethodHandle prepareForInvoker(MethodHandle mh) {
            mh = mh.asFixedArity();
            MethodType mt = mh.type();
            int arity = mt.parameterCount();
            MethodHandle vamh = mh.asType(mt.generic());
            vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
            vamh = vamh.asSpreader(Object[].class, arity);
            vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
            return vamh;
        }

        // Undo the adapter effect of prepareForInvoker:
        private static MethodHandle restoreToType(MethodHandle vamh,
                                                  MethodHandle original,
                                                  Class<?> hostClass) {
            MethodType type = original.type();
            MethodHandle mh = vamh.asCollector(Object[].class, type.parameterCount());
            MemberName member = original.internalMemberName();
            mh = mh.asType(type);
            mh = new WrappedMember(mh, type, member, original.isInvokeSpecial(), hostClass);
            return mh;
        }

        private static boolean checkInjectedInvoker(Class<?> hostClass, Class<?> invokerClass) {
            assert (hostClass.getClassLoader() == invokerClass.getClassLoader()) : hostClass.getName()+" (CL)";
            try {
                assert (hostClass.getProtectionDomain() == invokerClass.getProtectionDomain()) : hostClass.getName()+" (PD)";
            } catch (SecurityException ex) {
                // Self-check was blocked by security manager. This is OK.
            }
            try {
                // Test the invoker to ensure that it really injects into the right place.
                MethodHandle invoker = IMPL_LOOKUP.findStatic(invokerClass, "invoke_V", INVOKER_MT);
                MethodHandle vamh = prepareForInvoker(MH_checkCallerClass);
                return (boolean)invoker.invoke(vamh, new Object[]{ invokerClass });
            } catch (Throwable ex) {
                throw new InternalError(ex);
            }
        }

        private static final MethodHandle MH_checkCallerClass;
        static {
            final Class<?> THIS_CLASS = BindCaller.class;
            assert(checkCallerClass(THIS_CLASS));
            try {
                MH_checkCallerClass = IMPL_LOOKUP
                    .findStatic(THIS_CLASS, "checkCallerClass",
                                MethodType.methodType(boolean.class, Class.class));
                assert((boolean) MH_checkCallerClass.invokeExact(THIS_CLASS));
            } catch (Throwable ex) {
                throw new InternalError(ex);
            }
        }

        @CallerSensitive
        @ForceInline // to ensure Reflection.getCallerClass optimization
        private static boolean checkCallerClass(Class<?> expected) {
            // This method is called via MH_checkCallerClass and so it's correct to ask for the immediate caller here.
            Class<?> actual = Reflection.getCallerClass();
            if (actual != expected)
                throw new InternalError("found " + actual.getName() + ", expected " + expected.getName());
            return true;
        }

        private static final byte[] INJECTED_INVOKER_TEMPLATE = generateInvokerTemplate();

        
Produces byte code for a class that is used as an injected invoker. /** Produces byte code for a class that is used as an injected invoker. */
        private static byte[] generateInvokerTemplate() {
            ClassWriter cw = new ClassWriter(0);

            // private static class InjectedInvoker {
            //     @Hidden
            //     static Object invoke_V(MethodHandle vamh, Object[] args) throws Throwable {
            //        return vamh.invokeExact(args);
            //     }
            // }
            cw.visit(52, ACC_PRIVATE | ACC_SUPER, "InjectedInvoker", null, "java/lang/Object", null);

            MethodVisitor mv = cw.visitMethod(ACC_STATIC, "invoke_V",
                          "(Ljava/lang/invoke/MethodHandle;[Ljava/lang/Object;)Ljava/lang/Object;",
                          null, null);

            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/invoke/MethodHandle", "invokeExact",
                               "([Ljava/lang/Object;)Ljava/lang/Object;", false);
            mv.visitInsn(ARETURN);
            mv.visitMaxs(2, 2);
            mv.visitEnd();

            cw.visitEnd();
            return cw.toByteArray();
        }
    }

    
This subclass allows a wrapped method handle to be re-associated with an arbitrary member name. /** This subclass allows a wrapped method handle to be re-associated with an arbitrary member name. */
    private static final class WrappedMember extends DelegatingMethodHandle {
        private final MethodHandle target;
        private final MemberName member;
        private final Class<?> callerClass;
        private final boolean isInvokeSpecial;

        private WrappedMember(MethodHandle target, MethodType type,
                              MemberName member, boolean isInvokeSpecial,
                              Class<?> callerClass) {
            super(type, target);
            this.target = target;
            this.member = member;
            this.callerClass = callerClass;
            this.isInvokeSpecial = isInvokeSpecial;
        }

        @Override
        MemberName internalMemberName() {
            return member;
        }
        @Override
        Class<?> internalCallerClass() {
            return callerClass;
        }
        @Override
        boolean isInvokeSpecial() {
            return isInvokeSpecial;
        }
        @Override
        protected MethodHandle getTarget() {
            return target;
        }
        @Override
        public MethodHandle asTypeUncached(MethodType newType) {
            // This MH is an alias for target, except for the MemberName
            // Drop the MemberName if there is any conversion.
            return asTypeCache = target.asType(newType);
        }
    }

    static MethodHandle makeWrappedMember(MethodHandle target, MemberName member, boolean isInvokeSpecial) {
        if (member.equals(target.internalMemberName()) && isInvokeSpecial == target.isInvokeSpecial())
            return target;
        return new WrappedMember(target, target.type(), member, isInvokeSpecial, null);
    }

    
Intrinsic IDs /** Intrinsic IDs */
    /*non-public*/
    enum Intrinsic {
        SELECT_ALTERNATIVE,
        GUARD_WITH_CATCH,
        TRY_FINALLY,
        LOOP,
        NEW_ARRAY,
        ARRAY_LOAD,
        ARRAY_STORE,
        ARRAY_LENGTH,
        IDENTITY,
        ZERO,
        NONE // no intrinsic associated
    }

    
Mark arbitrary method handle as intrinsic.
InvokerBytecodeGenerator uses this info to produce more efficient bytecode shape. /** Mark arbitrary method handle as intrinsic.
     * InvokerBytecodeGenerator uses this info to produce more efficient bytecode shape. */
    static final class IntrinsicMethodHandle extends DelegatingMethodHandle {
        private final MethodHandle target;
        private final Intrinsic intrinsicName;

        IntrinsicMethodHandle(MethodHandle target, Intrinsic intrinsicName) {
            super(target.type(), target);
            this.target = target;
            this.intrinsicName = intrinsicName;
        }

        @Override
        protected MethodHandle getTarget() {
            return target;
        }

        @Override
        Intrinsic intrinsicName() {
            return intrinsicName;
        }

        @Override
        public MethodHandle asTypeUncached(MethodType newType) {
            // This MH is an alias for target, except for the intrinsic name
            // Drop the name if there is any conversion.
            return asTypeCache = target.asType(newType);
        }

        @Override
        String internalProperties() {
            return super.internalProperties() +
                    "\n& Intrinsic="+intrinsicName;
        }

        @Override
        public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
            if (intrinsicName == Intrinsic.IDENTITY) {
                MethodType resultType = type().asCollectorType(arrayType, type().parameterCount() - 1, arrayLength);
                MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
                return newArray.asType(resultType);
            }
            return super.asCollector(arrayType, arrayLength);
        }
    }

    static MethodHandle makeIntrinsic(MethodHandle target, Intrinsic intrinsicName) {
        if (intrinsicName == target.intrinsicName())
            return target;
        return new IntrinsicMethodHandle(target, intrinsicName);
    }

    static MethodHandle makeIntrinsic(MethodType type, LambdaForm form, Intrinsic intrinsicName) {
        return new IntrinsicMethodHandle(SimpleMethodHandle.make(type, form), intrinsicName);
    }

    /// Collection of multiple arguments.

    private static MethodHandle findCollector(String name, int nargs, Class<?> rtype, Class<?>... ptypes) {
        MethodType type = MethodType.genericMethodType(nargs)
                .changeReturnType(rtype)
                .insertParameterTypes(0, ptypes);
        try {
            return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, name, type);
        } catch (ReflectiveOperationException ex) {
            return null;
        }
    }

    private static final Object[] NO_ARGS_ARRAY = {};
    private static Object[] makeArray(Object... args) { return args; }
    private static Object[] array() { return NO_ARGS_ARRAY; }
    private static Object[] array(Object a0)
                { return makeArray(a0); }
    private static Object[] array(Object a0, Object a1)
                { return makeArray(a0, a1); }
    private static Object[] array(Object a0, Object a1, Object a2)
                { return makeArray(a0, a1, a2); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3)
                { return makeArray(a0, a1, a2, a3); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4)
                { return makeArray(a0, a1, a2, a3, a4); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5)
                { return makeArray(a0, a1, a2, a3, a4, a5); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6)
                { return makeArray(a0, a1, a2, a3, a4, a5, a6); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7)
                { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7,
                                  Object a8)
                { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8); }
    private static Object[] array(Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7,
                                  Object a8, Object a9)
                { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); }

    private static final int ARRAYS_COUNT = 11;
    private static final @Stable MethodHandle[] ARRAYS = new MethodHandle[MAX_ARITY + 1];

    // filling versions of the above:
    // using Integer len instead of int len and no varargs to avoid bootstrapping problems
    private static Object[] fillNewArray(Integer len, Object[] /*not ...*/ args) {
        Object[] a = new Object[len];
        fillWithArguments(a, 0, args);
        return a;
    }
    private static Object[] fillNewTypedArray(Object[] example, Integer len, Object[] /*not ...*/ args) {
        Object[] a = Arrays.copyOf(example, len);
        assert(a.getClass() != Object[].class);
        fillWithArguments(a, 0, args);
        return a;
    }
    private static void fillWithArguments(Object[] a, int pos, Object... args) {
        System.arraycopy(args, 0, a, pos, args.length);
    }
    // using Integer pos instead of int pos to avoid bootstrapping problems
    private static Object[] fillArray(Integer pos, Object[] a, Object a0)
                { fillWithArguments(a, pos, a0); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1)
                { fillWithArguments(a, pos, a0, a1); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2)
                { fillWithArguments(a, pos, a0, a1, a2); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3)
                { fillWithArguments(a, pos, a0, a1, a2, a3); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7,
                                  Object a8)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8); return a; }
    private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
                                  Object a4, Object a5, Object a6, Object a7,
                                  Object a8, Object a9)
                { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); return a; }

    private static final int FILL_ARRAYS_COUNT = 11; // current number of fillArray methods
    private static final @Stable MethodHandle[] FILL_ARRAYS = new MethodHandle[FILL_ARRAYS_COUNT];

    private static MethodHandle getFillArray(int count) {
        assert (count > 0 && count < FILL_ARRAYS_COUNT);
        MethodHandle mh = FILL_ARRAYS[count];
        if (mh != null) {
            return mh;
        }
        mh = findCollector("fillArray", count, Object[].class, Integer.class, Object[].class);
        FILL_ARRAYS[count] = mh;
        return mh;
    }

    private static Object copyAsPrimitiveArray(Wrapper w, Object... boxes) {
        Object a = w.makeArray(boxes.length);
        w.copyArrayUnboxing(boxes, 0, a, 0, boxes.length);
        return a;
    }

    
Return a method handle that takes the indicated number of Object
 arguments and returns an Object array of them, as if for varargs.
/** Return a method handle that takes the indicated number of Object
     *  arguments and returns an Object array of them, as if for varargs.
     */
    static MethodHandle varargsArray(int nargs) {
        MethodHandle mh = ARRAYS[nargs];
        if (mh != null) {
            return mh;
        }
        if (nargs < ARRAYS_COUNT) {
            mh = findCollector("array", nargs, Object[].class);
        } else {
            mh = buildVarargsArray(getConstantHandle(MH_fillNewArray),
                    getConstantHandle(MH_arrayIdentity), nargs);
        }
        assert(assertCorrectArity(mh, nargs));
        mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
        return ARRAYS[nargs] = mh;
    }

    private static boolean assertCorrectArity(MethodHandle mh, int arity) {
        assert(mh.type().parameterCount() == arity) : "arity != "+arity+": "+mh;
        return true;
    }

    // Array identity function (used as getConstantHandle(MH_arrayIdentity)).
    static <T> T[] identity(T[] x) {
        return x;
    }

    private static MethodHandle buildVarargsArray(MethodHandle newArray, MethodHandle finisher, int nargs) {
        // Build up the result mh as a sequence of fills like this:
        //   finisher(fill(fill(newArrayWA(23,x1..x10),10,x11..x20),20,x21..x23))
        // The various fill(_,10*I,___*[J]) are reusable.
        int leftLen = Math.min(nargs, LEFT_ARGS);  // absorb some arguments immediately
        int rightLen = nargs - leftLen;
        MethodHandle leftCollector = newArray.bindTo(nargs);
        leftCollector = leftCollector.asCollector(Object[].class, leftLen);
        MethodHandle mh = finisher;
        if (rightLen > 0) {
            MethodHandle rightFiller = fillToRight(LEFT_ARGS + rightLen);
            if (mh.equals(getConstantHandle(MH_arrayIdentity)))
                mh = rightFiller;
            else
                mh = MethodHandles.collectArguments(mh, 0, rightFiller);
        }
        if (mh.equals(getConstantHandle(MH_arrayIdentity)))
            mh = leftCollector;
        else
            mh = MethodHandles.collectArguments(mh, 0, leftCollector);
        return mh;
    }

    private static final int LEFT_ARGS = FILL_ARRAYS_COUNT - 1;
    private static final @Stable MethodHandle[] FILL_ARRAY_TO_RIGHT = new MethodHandle[MAX_ARITY + 1];
    
fill_array_to_right(N).invoke(a, argL..arg[N-1])
 fills a[L]..a[N-1] with corresponding arguments,
 and then returns a.  The value L is a global constant (LEFT_ARGS).
/** fill_array_to_right(N).invoke(a, argL..arg[N-1])
     *  fills a[L]..a[N-1] with corresponding arguments,
     *  and then returns a.  The value L is a global constant (LEFT_ARGS).
     */
    private static MethodHandle fillToRight(int nargs) {
        MethodHandle filler = FILL_ARRAY_TO_RIGHT[nargs];
        if (filler != null)  return filler;
        filler = buildFiller(nargs);
        assert(assertCorrectArity(filler, nargs - LEFT_ARGS + 1));
        return FILL_ARRAY_TO_RIGHT[nargs] = filler;
    }
    private static MethodHandle buildFiller(int nargs) {
        if (nargs <= LEFT_ARGS)
            return getConstantHandle(MH_arrayIdentity);  // no args to fill; return the array unchanged
        // we need room for both mh and a in mh.invoke(a, arg*[nargs])
        final int CHUNK = LEFT_ARGS;
        int rightLen = nargs % CHUNK;
        int midLen = nargs - rightLen;
        if (rightLen == 0) {
            midLen = nargs - (rightLen = CHUNK);
            if (FILL_ARRAY_TO_RIGHT[midLen] == null) {
                // build some precursors from left to right
                for (int j = LEFT_ARGS % CHUNK; j < midLen; j += CHUNK)
                    if (j > LEFT_ARGS)  fillToRight(j);
            }
        }
        if (midLen < LEFT_ARGS) rightLen = nargs - (midLen = LEFT_ARGS);
        assert(rightLen > 0);
        MethodHandle midFill = fillToRight(midLen);  // recursive fill
        MethodHandle rightFill = getFillArray(rightLen).bindTo(midLen);  // [midLen..nargs-1]
        assert(midFill.type().parameterCount()   == 1 + midLen - LEFT_ARGS);
        assert(rightFill.type().parameterCount() == 1 + rightLen);

        // Combine the two fills:
        //   right(mid(a, x10..x19), x20..x23)
        // The final product will look like this:
        //   right(mid(newArrayLeft(24, x0..x9), x10..x19), x20..x23)
        if (midLen == LEFT_ARGS)
            return rightFill;
        else
            return MethodHandles.collectArguments(rightFill, 0, midFill);
    }

    static final int MAX_JVM_ARITY = 255;  // limit imposed by the JVM

    
Return a method handle that takes the indicated number of
 typed arguments and returns an array of them.
 The type argument is the array type.
/** Return a method handle that takes the indicated number of
     *  typed arguments and returns an array of them.
     *  The type argument is the array type.
     */
    static MethodHandle varargsArray(Class<?> arrayType, int nargs) {
        Class<?> elemType = arrayType.getComponentType();
        if (elemType == null)  throw new IllegalArgumentException("not an array: "+arrayType);
        // FIXME: Need more special casing and caching here.
        if (nargs >= MAX_JVM_ARITY/2 - 1) {
            int slots = nargs;
            final int MAX_ARRAY_SLOTS = MAX_JVM_ARITY - 1;  // 1 for receiver MH
            if (slots <= MAX_ARRAY_SLOTS && elemType.isPrimitive())
                slots *= Wrapper.forPrimitiveType(elemType).stackSlots();
            if (slots > MAX_ARRAY_SLOTS)
                throw new IllegalArgumentException("too many arguments: "+arrayType.getSimpleName()+", length "+nargs);
        }
        if (elemType == Object.class)
            return varargsArray(nargs);
        // other cases:  primitive arrays, subtypes of Object[]
        MethodHandle cache[] = Makers.TYPED_COLLECTORS.get(elemType);
        MethodHandle mh = nargs < cache.length ? cache[nargs] : null;
        if (mh != null)  return mh;
        if (nargs == 0) {
            Object example = java.lang.reflect.Array.newInstance(arrayType.getComponentType(), 0);
            mh = MethodHandles.constant(arrayType, example);
        } else if (elemType.isPrimitive()) {
            MethodHandle builder = getConstantHandle(MH_fillNewArray);
            MethodHandle producer = buildArrayProducer(arrayType);
            mh = buildVarargsArray(builder, producer, nargs);
        } else {
            Class<? extends Object[]> objArrayType = arrayType.asSubclass(Object[].class);
            Object[] example = Arrays.copyOf(NO_ARGS_ARRAY, 0, objArrayType);
            MethodHandle builder = getConstantHandle(MH_fillNewTypedArray).bindTo(example);
            MethodHandle producer = getConstantHandle(MH_arrayIdentity); // must be weakly typed
            mh = buildVarargsArray(builder, producer, nargs);
        }
        mh = mh.asType(MethodType.methodType(arrayType, Collections.<Class<?>>nCopies(nargs, elemType)));
        mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
        assert(assertCorrectArity(mh, nargs));
        if (nargs < cache.length)
            cache[nargs] = mh;
        return mh;
    }

    private static MethodHandle buildArrayProducer(Class<?> arrayType) {
        Class<?> elemType = arrayType.getComponentType();
        assert(elemType.isPrimitive());
        return getConstantHandle(MH_copyAsPrimitiveArray).bindTo(Wrapper.forPrimitiveType(elemType));
    }

    /*non-public*/
    static void assertSame(Object mh1, Object mh2) {
        if (mh1 != mh2) {
            String msg = String.format("mh1 != mh2: mh1 = %s (form: %s); mh2 = %s (form: %s)",
                    mh1, ((MethodHandle)mh1).form,
                    mh2, ((MethodHandle)mh2).form);
            throw newInternalError(msg);
        }
    }

    // Local constant functions:

    /* non-public */
    static final byte NF_checkSpreadArgument = 0,
            NF_guardWithCatch = 1,
            NF_throwException = 2,
            NF_tryFinally = 3,
            NF_loop = 4,
            NF_profileBoolean = 5,
            NF_LIMIT = 6;

    private static final @Stable NamedFunction[] NFS = new NamedFunction[NF_LIMIT];

    static NamedFunction getFunction(byte func) {
        NamedFunction nf = NFS[func];
        if (nf != null) {
            return nf;
        }
        return NFS[func] = createFunction(func);
    }

    private static NamedFunction createFunction(byte func) {
        try {
            switch (func) {
                case NF_checkSpreadArgument:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("checkSpreadArgument", Object.class, int.class));
                case NF_guardWithCatch:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,
                                    MethodHandle.class, Object[].class));
                case NF_tryFinally:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("tryFinally", MethodHandle.class, MethodHandle.class, Object[].class));
                case NF_loop:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("loop", BasicType[].class, LoopClauses.class, Object[].class));
                case NF_throwException:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("throwException", Throwable.class));
                case NF_profileBoolean:
                    return new NamedFunction(MethodHandleImpl.class
                            .getDeclaredMethod("profileBoolean", boolean.class, int[].class));
                default:
                    throw new InternalError("Undefined function: " + func);
            }
        } catch (ReflectiveOperationException ex) {
            throw newInternalError(ex);
        }
    }

    static {
        SharedSecrets.setJavaLangInvokeAccess(new JavaLangInvokeAccess() {
            @Override
            public Object newMemberName() {
                return new MemberName();
            }

            @Override
            public String getName(Object mname) {
                MemberName memberName = (MemberName)mname;
                return memberName.getName();
            }
            @Override
            public Class<?> getDeclaringClass(Object mname) {
                MemberName memberName = (MemberName)mname;
                return memberName.getDeclaringClass();
            }

            @Override
            public MethodType getMethodType(Object mname) {
                MemberName memberName = (MemberName)mname;
                return memberName.getMethodType();
            }

            @Override
            public String getMethodDescriptor(Object mname) {
                MemberName memberName = (MemberName)mname;
                return memberName.getMethodDescriptor();
            }

            @Override
            public boolean isNative(Object mname) {
                MemberName memberName = (MemberName)mname;
                return memberName.isNative();
            }

            @Override
            public Map<String, byte[]> generateHolderClasses(Stream<String> traces) {
                return GenerateJLIClassesHelper.generateHolderClasses(traces);
            }

            @Override
            public VarHandle memoryAccessVarHandle(Class<?> carrier, boolean skipAlignmentMaskCheck, long alignmentMask,
                                                   ByteOrder order) {
                return VarHandles.makeMemoryAddressViewHandle(carrier, skipAlignmentMaskCheck, alignmentMask, order);
            }

            @Override
            public MethodHandle nativeMethodHandle(NativeEntryPoint nep, MethodHandle fallback) {
                return NativeMethodHandle.make(nep, fallback);
            }

            @Override
            public VarHandle filterValue(VarHandle target, MethodHandle filterToTarget, MethodHandle filterFromTarget) {
                return VarHandles.filterValue(target, filterToTarget, filterFromTarget);
            }

            @Override
            public VarHandle filterCoordinates(VarHandle target, int pos, MethodHandle... filters) {
                return VarHandles.filterCoordinates(target, pos, filters);
            }

            @Override
            public VarHandle dropCoordinates(VarHandle target, int pos, Class<?>... valueTypes) {
                return VarHandles.dropCoordinates(target, pos, valueTypes);
            }

            @Override
            public VarHandle permuteCoordinates(VarHandle target, List<Class<?>> newCoordinates, int... reorder) {
                return VarHandles.permuteCoordinates(target, newCoordinates, reorder);
            }

            @Override
            public VarHandle collectCoordinates(VarHandle target, int pos, MethodHandle filter) {
                return VarHandles.collectCoordinates(target, pos, filter);
            }

            @Override
            public VarHandle insertCoordinates(VarHandle target, int pos, Object... values) {
                return VarHandles.insertCoordinates(target, pos, values);
            }
        });
    }

    
Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore(). /** Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore(). */
    private static MethodHandle unboxResultHandle(Class<?> returnType) {
        if (returnType.isPrimitive()) {
            if (returnType == void.class) {
                return ValueConversions.ignore();
            } else {
                Wrapper w = Wrapper.forPrimitiveType(returnType);
                return ValueConversions.unboxExact(w);
            }
        } else {
            return MethodHandles.identity(Object.class);
        }
    }

    
Assembles a loop method handle from the given handles and type information.
Params:
tloop – the return type of the loop.
targs – types of the arguments to be passed to the loop.
init – sanitized array of initializers for loop-local variables.
step – sanitited array of loop bodies.
pred – sanitized array of predicates.
fini – sanitized array of loop finalizers.
Returns:
a handle that, when invoked, will execute the loop./**
     * Assembles a loop method handle from the given handles and type information.
     *
     * @param tloop the return type of the loop.
     * @param targs types of the arguments to be passed to the loop.
     * @param init sanitized array of initializers for loop-local variables.
     * @param step sanitited array of loop bodies.
     * @param pred sanitized array of predicates.
     * @param fini sanitized array of loop finalizers.
     *
     * @return a handle that, when invoked, will execute the loop.
     */
    static MethodHandle makeLoop(Class<?> tloop, List<Class<?>> targs, List<MethodHandle> init, List<MethodHandle> step,
                                 List<MethodHandle> pred, List<MethodHandle> fini) {
        MethodType type = MethodType.methodType(tloop, targs);
        BasicType[] initClauseTypes =
                init.stream().map(h -> h.type().returnType()).map(BasicType::basicType).toArray(BasicType[]::new);
        LambdaForm form = makeLoopForm(type.basicType(), initClauseTypes);

        // Prepare auxiliary method handles used during LambdaForm interpretation.
        // Box arguments and wrap them into Object[]: ValueConversions.array().
        MethodType varargsType = type.changeReturnType(Object[].class);
        MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
        MethodHandle unboxResult = unboxResultHandle(tloop);

        LoopClauses clauseData =
                new LoopClauses(new MethodHandle[][]{toArray(init), toArray(step), toArray(pred), toArray(fini)});
        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
        BoundMethodHandle mh;
        try {
            mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) clauseData,
                    (Object) collectArgs, (Object) unboxResult);
        } catch (Throwable ex) {
            throw uncaughtException(ex);
        }
        assert(mh.type() == type);
        return mh;
    }

    private static MethodHandle[] toArray(List<MethodHandle> l) {
        return l.toArray(new MethodHandle[0]);
    }

    
Loops introduce some complexity as they can have additional local state. Hence, LambdaForms for loops are generated from a template. The LambdaForm template shape for the loop combinator is as follows (assuming one reference parameter passed in a1, and a reference return type, with the return value represented by t12): 

 loop=Lambda(a0:L,a1:L)=>{
   t2:L=BoundMethodHandle$Species_L3.argL0(a0:L);    // LoopClauses holding init, step, pred, fini handles
   t3:L=BoundMethodHandle$Species_L3.argL1(a0:L);    // helper handle to box the arguments into an Object[]
   t4:L=BoundMethodHandle$Species_L3.argL2(a0:L);    // helper handle to unbox the result
   t5:L=MethodHandle.invokeBasic(t3:L,a1:L);         // box the arguments into an Object[]
   t6:L=MethodHandleImpl.loop(null,t2:L,t3:L);       // call the loop executor
   t7:L=MethodHandle.invokeBasic(t4:L,t6:L);t7:L}    // unbox the result; return the result

 argL0 is a LoopClauses instance holding, in a 2-dimensional array, the init, step, pred, and fini method handles. argL1 and argL2 are auxiliary method handles: argL1 boxes arguments and wraps them into Object[] (ValueConversions.array()), and argL2 unboxes the result if necessary (ValueConversions.unbox()). 
 Having t3 and t4 passed in via a BMH and not hardcoded in the lambda form allows to share lambda forms among loop combinators with the same basic type. 
 The above template is instantiated by using the LambdaFormEditor to replace the null argument to the loop invocation with the BasicType array describing the loop clause types. This argument is ignored in the loop invoker, but will be extracted and used in 
bytecode generation. /**
     * Loops introduce some complexity as they can have additional local state. Hence, LambdaForms for loops are
     * generated from a template. The LambdaForm template shape for the loop combinator is as follows (assuming one
     * reference parameter passed in {@code a1}, and a reference return type, with the return value represented by
     * {@code t12}):
     * <blockquote><pre>{@code
     *  loop=Lambda(a0:L,a1:L)=>{
     *    t2:L=BoundMethodHandle$Species_L3.argL0(a0:L);    // LoopClauses holding init, step, pred, fini handles
     *    t3:L=BoundMethodHandle$Species_L3.argL1(a0:L);    // helper handle to box the arguments into an Object[]
     *    t4:L=BoundMethodHandle$Species_L3.argL2(a0:L);    // helper handle to unbox the result
     *    t5:L=MethodHandle.invokeBasic(t3:L,a1:L);         // box the arguments into an Object[]
     *    t6:L=MethodHandleImpl.loop(null,t2:L,t3:L);       // call the loop executor
     *    t7:L=MethodHandle.invokeBasic(t4:L,t6:L);t7:L}    // unbox the result; return the result
     * }</pre></blockquote>
     * <p>
     * {@code argL0} is a LoopClauses instance holding, in a 2-dimensional array, the init, step, pred, and fini method
     * handles. {@code argL1} and {@code argL2} are auxiliary method handles: {@code argL1} boxes arguments and wraps
     * them into {@code Object[]} ({@code ValueConversions.array()}), and {@code argL2} unboxes the result if necessary
     * ({@code ValueConversions.unbox()}).
     * <p>
     * Having {@code t3} and {@code t4} passed in via a BMH and not hardcoded in the lambda form allows to share lambda
     * forms among loop combinators with the same basic type.
     * <p>
     * The above template is instantiated by using the {@link LambdaFormEditor} to replace the {@code null} argument to
     * the {@code loop} invocation with the {@code BasicType} array describing the loop clause types. This argument is
     * ignored in the loop invoker, but will be extracted and used in {@linkplain InvokerBytecodeGenerator#emitLoop(int)
     * bytecode generation}.
     */
    private static LambdaForm makeLoopForm(MethodType basicType, BasicType[] localVarTypes) {
        MethodType lambdaType = basicType.invokerType();

        final int THIS_MH = 0;  // the BMH_LLL
        final int ARG_BASE = 1; // start of incoming arguments
        final int ARG_LIMIT = ARG_BASE + basicType.parameterCount();

        int nameCursor = ARG_LIMIT;
        final int GET_CLAUSE_DATA = nameCursor++;
        final int GET_COLLECT_ARGS = nameCursor++;
        final int GET_UNBOX_RESULT = nameCursor++;
        final int BOXED_ARGS = nameCursor++;
        final int LOOP = nameCursor++;
        final int UNBOX_RESULT = nameCursor++;

        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_LOOP);
        if (lform == null) {
            Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

            BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
            names[THIS_MH] = names[THIS_MH].withConstraint(data);
            names[GET_CLAUSE_DATA] = new Name(data.getterFunction(0), names[THIS_MH]);
            names[GET_COLLECT_ARGS] = new Name(data.getterFunction(1), names[THIS_MH]);
            names[GET_UNBOX_RESULT] = new Name(data.getterFunction(2), names[THIS_MH]);

            // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
            MethodType collectArgsType = basicType.changeReturnType(Object.class);
            MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
            Object[] args = new Object[invokeBasic.type().parameterCount()];
            args[0] = names[GET_COLLECT_ARGS];
            System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT - ARG_BASE);
            names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.LOOP), args);

            // t_{i+1}:L=MethodHandleImpl.loop(localTypes:L,clauses:L,t_{i}:L);
            Object[] lArgs =
                    new Object[]{null, // placeholder for BasicType[] localTypes - will be added by LambdaFormEditor
                            names[GET_CLAUSE_DATA], names[BOXED_ARGS]};
            names[LOOP] = new Name(getFunction(NF_loop), lArgs);

            // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
            MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
            Object[] unboxArgs = new Object[]{names[GET_UNBOX_RESULT], names[LOOP]};
            names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);

            lform = basicType.form().setCachedLambdaForm(MethodTypeForm.LF_LOOP,
                    new LambdaForm(lambdaType.parameterCount(), names, Kind.LOOP));
        }

        // BOXED_ARGS is the index into the names array where the loop idiom starts
        return lform.editor().noteLoopLocalTypesForm(BOXED_ARGS, localVarTypes);
    }

    static class LoopClauses {
        @Stable final MethodHandle[][] clauses;
        LoopClauses(MethodHandle[][] clauses) {
            assert clauses.length == 4;
            this.clauses = clauses;
        }
        @Override
        public String toString() {
            StringBuffer sb = new StringBuffer("LoopClauses -- ");
            for (int i = 0; i < 4; ++i) {
                if (i > 0) {
                    sb.append("       ");
                }
                sb.append('<').append(i).append(">: ");
                MethodHandle[] hs = clauses[i];
                for (int j = 0; j < hs.length; ++j) {
                    if (j > 0) {
                        sb.append("          ");
                    }
                    sb.append('*').append(j).append(": ").append(hs[j]).append('\n');
                }
            }
            sb.append(" --\n");
            return sb.toString();
        }
    }

    
Intrinsified during LambdaForm compilation (see InvokerBytecodeGenerator.emitLoop(int)). /**
     * Intrinsified during LambdaForm compilation
     * (see {@link InvokerBytecodeGenerator#emitLoop(int)}).
     */
    @Hidden
    static Object loop(BasicType[] localTypes, LoopClauses clauseData, Object... av) throws Throwable {
        final MethodHandle[] init = clauseData.clauses[0];
        final MethodHandle[] step = clauseData.clauses[1];
        final MethodHandle[] pred = clauseData.clauses[2];
        final MethodHandle[] fini = clauseData.clauses[3];
        int varSize = (int) Stream.of(init).filter(h -> h.type().returnType() != void.class).count();
        int nArgs = init[0].type().parameterCount();
        Object[] varsAndArgs = new Object[varSize + nArgs];
        for (int i = 0, v = 0; i < init.length; ++i) {
            MethodHandle ih = init[i];
            if (ih.type().returnType() == void.class) {
                ih.invokeWithArguments(av);
            } else {
                varsAndArgs[v++] = ih.invokeWithArguments(av);
            }
        }
        System.arraycopy(av, 0, varsAndArgs, varSize, nArgs);
        final int nSteps = step.length;
        for (; ; ) {
            for (int i = 0, v = 0; i < nSteps; ++i) {
                MethodHandle p = pred[i];
                MethodHandle s = step[i];
                MethodHandle f = fini[i];
                if (s.type().returnType() == void.class) {
                    s.invokeWithArguments(varsAndArgs);
                } else {
                    varsAndArgs[v++] = s.invokeWithArguments(varsAndArgs);
                }
                if (!(boolean) p.invokeWithArguments(varsAndArgs)) {
                    return f.invokeWithArguments(varsAndArgs);
                }
            }
        }
    }

    
This method is bound as the predicate in counting loops. 
Params:
limit – the upper bound of the parameter, statically bound at loop creation time.
counter – the counter parameter, passed in during loop execution.
Returns:
whether the counter has reached the limit./**
     * This method is bound as the predicate in {@linkplain MethodHandles#countedLoop(MethodHandle, MethodHandle,
     * MethodHandle) counting loops}.
     *
     * @param limit the upper bound of the parameter, statically bound at loop creation time.
     * @param counter the counter parameter, passed in during loop execution.
     *
     * @return whether the counter has reached the limit.
     */
    static boolean countedLoopPredicate(int limit, int counter) {
        return counter < limit;
    }

    
This method is bound as the step function in counting loops to increment the counter. 
Params:
limit – the upper bound of the loop counter (ignored).
counter – the loop counter.
Returns:
the loop counter incremented by 1./**
     * This method is bound as the step function in {@linkplain MethodHandles#countedLoop(MethodHandle, MethodHandle,
     * MethodHandle) counting loops} to increment the counter.
     *
     * @param limit the upper bound of the loop counter (ignored).
     * @param counter the loop counter.
     *
     * @return the loop counter incremented by 1.
     */
    static int countedLoopStep(int limit, int counter) {
        return counter + 1;
    }

    
This is bound to initialize the loop-local iterator in iterating loops. 
Params:
it – the Iterable over which the loop iterates.
Returns:
an Iterator over the argument's elements./**
     * This is bound to initialize the loop-local iterator in {@linkplain MethodHandles#iteratedLoop iterating loops}.
     *
     * @param it the {@link Iterable} over which the loop iterates.
     *
     * @return an {@link Iterator} over the argument's elements.
     */
    static Iterator<?> initIterator(Iterable<?> it) {
        return it.iterator();
    }

    
This method is bound as the predicate in iterating loops. 
Params:
it – the iterator to be checked.
Returns:
true iff there are more elements to iterate over./**
     * This method is bound as the predicate in {@linkplain MethodHandles#iteratedLoop iterating loops}.
     *
     * @param it the iterator to be checked.
     *
     * @return {@code true} iff there are more elements to iterate over.
     */
    static boolean iteratePredicate(Iterator<?> it) {
        return it.hasNext();
    }

    
This method is bound as the step for retrieving the current value from the iterator in iterating loops. 
Params:
it – the iterator.
Returns:
the next element from the iterator./**
     * This method is bound as the step for retrieving the current value from the iterator in {@linkplain
     * MethodHandles#iteratedLoop iterating loops}.
     *
     * @param it the iterator.
     *
     * @return the next element from the iterator.
     */
    static Object iterateNext(Iterator<?> it) {
        return it.next();
    }

    
Makes a try-finally handle that conforms to the type constraints. 
Params:
target – the target to execute in a try-finally block.
cleanup – the cleanup to execute in the finally block.
rtype – the result type of the entire construct.
argTypes – the types of the arguments.
Returns:
a handle on the constructed try-finally block./**
     * Makes a {@code try-finally} handle that conforms to the type constraints.
     *
     * @param target the target to execute in a {@code try-finally} block.
     * @param cleanup the cleanup to execute in the {@code finally} block.
     * @param rtype the result type of the entire construct.
     * @param argTypes the types of the arguments.
     *
     * @return a handle on the constructed {@code try-finally} block.
     */
    static MethodHandle makeTryFinally(MethodHandle target, MethodHandle cleanup, Class<?> rtype, List<Class<?>> argTypes) {
        MethodType type = MethodType.methodType(rtype, argTypes);
        LambdaForm form = makeTryFinallyForm(type.basicType());

        // Prepare auxiliary method handles used during LambdaForm interpretation.
        // Box arguments and wrap them into Object[]: ValueConversions.array().
        MethodType varargsType = type.changeReturnType(Object[].class);
        MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
        MethodHandle unboxResult = unboxResultHandle(rtype);

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLL();
        BoundMethodHandle mh;
        try {
            mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) target, (Object) cleanup,
                    (Object) collectArgs, (Object) unboxResult);
        } catch (Throwable ex) {
            throw uncaughtException(ex);
        }
        assert(mh.type() == type);
        return mh;
    }

    
The LambdaForm shape for the tryFinally combinator is as follows (assuming one reference parameter passed in a1, and a reference return type, with the return value represented by t8): 

 tryFinally=Lambda(a0:L,a1:L)=>{
   t2:L=BoundMethodHandle$Species_LLLL.argL0(a0:L);  // target method handle
   t3:L=BoundMethodHandle$Species_LLLL.argL1(a0:L);  // cleanup method handle
   t4:L=BoundMethodHandle$Species_LLLL.argL2(a0:L);  // helper handle to box the arguments into an Object[]
   t5:L=BoundMethodHandle$Species_LLLL.argL3(a0:L);  // helper handle to unbox the result
   t6:L=MethodHandle.invokeBasic(t4:L,a1:L);         // box the arguments into an Object[]
   t7:L=MethodHandleImpl.tryFinally(t2:L,t3:L,t6:L); // call the tryFinally executor
   t8:L=MethodHandle.invokeBasic(t5:L,t7:L);t8:L}    // unbox the result; return the result

 argL0 and argL1 are the target and cleanup method handles. argL2 and argL3 are auxiliary method handles: argL2 boxes arguments and wraps them into Object[] (ValueConversions.array()), and argL3 unboxes the result if necessary (ValueConversions.unbox()). 
 Having t4 and t5 passed in via a BMH and not hardcoded in the lambda form allows to share lambda forms among tryFinally combinators with the same basic type. /**
     * The LambdaForm shape for the tryFinally combinator is as follows (assuming one reference parameter passed in
     * {@code a1}, and a reference return type, with the return value represented by {@code t8}):
     * <blockquote><pre>{@code
     *  tryFinally=Lambda(a0:L,a1:L)=>{
     *    t2:L=BoundMethodHandle$Species_LLLL.argL0(a0:L);  // target method handle
     *    t3:L=BoundMethodHandle$Species_LLLL.argL1(a0:L);  // cleanup method handle
     *    t4:L=BoundMethodHandle$Species_LLLL.argL2(a0:L);  // helper handle to box the arguments into an Object[]
     *    t5:L=BoundMethodHandle$Species_LLLL.argL3(a0:L);  // helper handle to unbox the result
     *    t6:L=MethodHandle.invokeBasic(t4:L,a1:L);         // box the arguments into an Object[]
     *    t7:L=MethodHandleImpl.tryFinally(t2:L,t3:L,t6:L); // call the tryFinally executor
     *    t8:L=MethodHandle.invokeBasic(t5:L,t7:L);t8:L}    // unbox the result; return the result
     * }</pre></blockquote>
     * <p>
     * {@code argL0} and {@code argL1} are the target and cleanup method handles.
     * {@code argL2} and {@code argL3} are auxiliary method handles: {@code argL2} boxes arguments and wraps them into
     * {@code Object[]} ({@code ValueConversions.array()}), and {@code argL3} unboxes the result if necessary
     * ({@code ValueConversions.unbox()}).
     * <p>
     * Having {@code t4} and {@code t5} passed in via a BMH and not hardcoded in the lambda form allows to share lambda
     * forms among tryFinally combinators with the same basic type.
     */
    private static LambdaForm makeTryFinallyForm(MethodType basicType) {
        MethodType lambdaType = basicType.invokerType();

        LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_TF);
        if (lform != null) {
            return lform;
        }
        final int THIS_MH      = 0;  // the BMH_LLLL
        final int ARG_BASE     = 1;  // start of incoming arguments
        final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();

        int nameCursor = ARG_LIMIT;
        final int GET_TARGET       = nameCursor++;
        final int GET_CLEANUP      = nameCursor++;
        final int GET_COLLECT_ARGS = nameCursor++;
        final int GET_UNBOX_RESULT = nameCursor++;
        final int BOXED_ARGS       = nameCursor++;
        final int TRY_FINALLY      = nameCursor++;
        final int UNBOX_RESULT     = nameCursor++;

        Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);

        BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLL();
        names[THIS_MH]          = names[THIS_MH].withConstraint(data);
        names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
        names[GET_CLEANUP]      = new Name(data.getterFunction(1), names[THIS_MH]);
        names[GET_COLLECT_ARGS] = new Name(data.getterFunction(2), names[THIS_MH]);
        names[GET_UNBOX_RESULT] = new Name(data.getterFunction(3), names[THIS_MH]);

        // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
        MethodType collectArgsType = basicType.changeReturnType(Object.class);
        MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
        Object[] args = new Object[invokeBasic.type().parameterCount()];
        args[0] = names[GET_COLLECT_ARGS];
        System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
        names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.TRY_FINALLY), args);

        // t_{i+1}:L=MethodHandleImpl.tryFinally(target:L,exType:L,catcher:L,t_{i}:L);
        Object[] tfArgs = new Object[] {names[GET_TARGET], names[GET_CLEANUP], names[BOXED_ARGS]};
        names[TRY_FINALLY] = new Name(getFunction(NF_tryFinally), tfArgs);

        // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
        MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
        Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_FINALLY]};
        names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);

        lform = new LambdaForm(lambdaType.parameterCount(), names, Kind.TRY_FINALLY);

        return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_TF, lform);
    }

    
Intrinsified during LambdaForm compilation (see emitTryFinally). /**
     * Intrinsified during LambdaForm compilation
     * (see {@link InvokerBytecodeGenerator#emitTryFinally emitTryFinally}).
     */
    @Hidden
    static Object tryFinally(MethodHandle target, MethodHandle cleanup, Object... av) throws Throwable {
        Throwable t = null;
        Object r = null;
        try {
            r = target.invokeWithArguments(av);
        } catch (Throwable thrown) {
            t = thrown;
            throw t;
        } finally {
            Object[] args = target.type().returnType() == void.class ? prepend(av, t) : prepend(av, t, r);
            r = cleanup.invokeWithArguments(args);
        }
        return r;
    }

    // Indexes into constant method handles:
    static final int
            MH_cast                  =  0,
            MH_selectAlternative     =  1,
            MH_copyAsPrimitiveArray  =  2,
            MH_fillNewTypedArray     =  3,
            MH_fillNewArray          =  4,
            MH_arrayIdentity         =  5,
            MH_countedLoopPred       =  6,
            MH_countedLoopStep       =  7,
            MH_initIterator          =  8,
            MH_iteratePred           =  9,
            MH_iterateNext           = 10,
            MH_Array_newInstance     = 11,
            MH_LIMIT                 = 12;

    static MethodHandle getConstantHandle(int idx) {
        MethodHandle handle = HANDLES[idx];
        if (handle != null) {
            return handle;
        }
        return setCachedHandle(idx, makeConstantHandle(idx));
    }

    private static synchronized MethodHandle setCachedHandle(int idx, final MethodHandle method) {
        // Simulate a CAS, to avoid racy duplication of results.
        MethodHandle prev = HANDLES[idx];
        if (prev != null) {
            return prev;
        }
        HANDLES[idx] = method;
        return method;
    }

    // Local constant method handles:
    private static final @Stable MethodHandle[] HANDLES = new MethodHandle[MH_LIMIT];

    private static MethodHandle makeConstantHandle(int idx) {
        try {
            switch (idx) {
                case MH_cast:
                    return IMPL_LOOKUP.findVirtual(Class.class, "cast",
                            MethodType.methodType(Object.class, Object.class));
                case MH_copyAsPrimitiveArray:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "copyAsPrimitiveArray",
                            MethodType.methodType(Object.class, Wrapper.class, Object[].class));
                case MH_arrayIdentity:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "identity",
                            MethodType.methodType(Object[].class, Object[].class));
                case MH_fillNewArray:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "fillNewArray",
                            MethodType.methodType(Object[].class, Integer.class, Object[].class));
                case MH_fillNewTypedArray:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "fillNewTypedArray",
                            MethodType.methodType(Object[].class, Object[].class, Integer.class, Object[].class));
                case MH_selectAlternative:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "selectAlternative",
                            MethodType.methodType(MethodHandle.class, boolean.class, MethodHandle.class, MethodHandle.class));
                case MH_countedLoopPred:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "countedLoopPredicate",
                            MethodType.methodType(boolean.class, int.class, int.class));
                case MH_countedLoopStep:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "countedLoopStep",
                            MethodType.methodType(int.class, int.class, int.class));
                case MH_initIterator:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "initIterator",
                            MethodType.methodType(Iterator.class, Iterable.class));
                case MH_iteratePred:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "iteratePredicate",
                            MethodType.methodType(boolean.class, Iterator.class));
                case MH_iterateNext:
                    return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "iterateNext",
                            MethodType.methodType(Object.class, Iterator.class));
                case MH_Array_newInstance:
                    return IMPL_LOOKUP.findStatic(Array.class, "newInstance",
                            MethodType.methodType(Object.class, Class.class, int.class));
            }
        } catch (ReflectiveOperationException ex) {
            throw newInternalError(ex);
        }
        throw newInternalError("Unknown function index: " + idx);
    }
}