/*

  * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  */

 package java.lang.invoke;

 import java.lang.annotation.*;

 import java.lang.reflect.Method;

 import java.util.Map;

 import java.util.List;

 import java.util.Arrays;

 import java.util.ArrayList;

 import java.util.HashMap;

 import java.util.concurrent.ConcurrentHashMap;

 import sun.invoke.util.Wrapper;

 import static java.lang.invoke.MethodHandleStatics.*;

 import static java.lang.invoke.MethodHandleNatives.Constants.*;

 import java.lang.reflect.Field;

 import java.util.Objects;

 /**

  * The symbolic, non-executable form of a method handle's invocation semantics.

  * It consists of a series of names.

  * The first N (N=arity) names are parameters,

  * while any remaining names are temporary values.

  * Each temporary specifies the application of a function to some arguments.

  * The functions are method handles, while the arguments are mixes of

  * constant values and local names.

  * The result of the lambda is defined as one of the names, often the last one.

  * <p>

  * Here is an approximate grammar:

  * <blockquote><pre>{@code

  * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"

  * ArgName = "a" N ":" T

  * TempName = "t" N ":" T "=" Function "(" Argument* ");"

  * Function = ConstantValue

  * Argument = NameRef | ConstantValue

  * Result = NameRef | "void"

  * NameRef = "a" N | "t" N

  * N = (any whole number)

  * T = "L" | "I" | "J" | "F" | "D" | "V"

  * }</pre></blockquote>

  * Names are numbered consecutively from left to right starting at zero.

  * (The letters are merely a taste of syntax sugar.)

  * Thus, the first temporary (if any) is always numbered N (where N=arity).

  * Every occurrence of a name reference in an argument list must refer to

  * a name previously defined within the same lambda.

  * A lambda has a void result if and only if its result index is -1.

  * If a temporary has the type "V", it cannot be the subject of a NameRef,

  * even though possesses a number.

  * Note that all reference types are erased to "L", which stands for {@code Object}.

  * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.

  * The other types stand for the usual primitive types.

  * <p>

  * Function invocation closely follows the static rules of the Java verifier.

  * Arguments and return values must exactly match when their "Name" types are

  * considered.

  * Conversions are allowed only if they do not change the erased type.

  * <ul>

  * <li>L = Object: casts are used freely to convert into and out of reference types

  * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})

  * <li>J = long: no implicit conversions

  * <li>F = float: no implicit conversions

  * <li>D = double: no implicit conversions

  * <li>V = void: a function result may be void if and only if its Name is of type "V"

  * </ul>

  * Although implicit conversions are not allowed, explicit ones can easily be

  * encoded by using temporary expressions which call type-transformed identity functions.

  * <p>

  * Examples:

  * <blockquote><pre>{@code

  * (a0:J)=>{ a0 }

  *     == identity(long)

  * (a0:I)=>{ t1:V = System.out#println(a0); void }

  *     == System.out#println(int)

  * (a0:L)=>{ t1:V = System.out#println(a0); a0 }

  *     == identity, with printing side-effect

  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

  *                 t3:L = BoundMethodHandle#target(a0);

  *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }

  *     == general invoker for unary insertArgument combination

  * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);

  *                 t3:L = MethodHandle#invoke(t2, a1);

  *                 t4:L = FilterMethodHandle#target(a0);

  *                 t5:L = MethodHandle#invoke(t4, t3); t5 }

  *     == general invoker for unary filterArgument combination

  * (a0:L, a1:L)=>{ ...(same as previous example)...

  *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }

  *     == general invoker for unary/unary foldArgument combination

  * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }

  *     == invoker for identity method handle which performs i2l

  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);

  *                 t3:L = Class#cast(t2,a1); t3 }

  *     == invoker for identity method handle which performs cast

  * }</pre></blockquote>

  * <p>

  * @author John Rose, JSR 292 EG

  */

 class LambdaForm {

     final int arity;

     final int result;

     @Stable final Name[] names;

     final String debugName;

     MemberName vmentry;   // low-level behavior, or null if not yet prepared

     private boolean isCompiled;

     // Caches for common structural transforms:

     LambdaForm[] bindCache;

     public static final int VOID_RESULT = -1, LAST_RESULT = -2;

     LambdaForm(String debugName,

                int arity, Name[] names, int result) {

         assert(namesOK(arity, names));

         this.arity = arity;

         this.result = fixResult(result, names);

         this.names = names.clone();

         this.debugName = debugName;

         normalize();

     }

     LambdaForm(String debugName,

                int arity, Name[] names) {

         this(debugName,

              arity, names, LAST_RESULT);

     }

     LambdaForm(String debugName,

                Name[] formals, Name[] temps, Name result) {

         this(debugName,

              formals.length, buildNames(formals, temps, result), LAST_RESULT);

     }

     private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {

         int arity = formals.length;

         int length = arity + temps.length + (result == null ? 0 : 1);

         Name[] names = Arrays.copyOf(formals, length);

         System.arraycopy(temps, 0, names, arity, temps.length);

         if (result != null)

             names[length - 1] = result;

         return names;

     }

     private LambdaForm(String sig) {

         // Make a blank lambda form, which returns a constant zero or null.

         // It is used as a template for managing the invocation of similar forms that are non-empty.

         // Called only from getPreparedForm.

         assert(isValidSignature(sig));

         this.arity = signatureArity(sig);

         this.result = (signatureReturn(sig) == 'V' ? -1 : arity);

         this.names = buildEmptyNames(arity, sig);

         this.debugName = "LF.zero";

         assert(nameRefsAreLegal());

         assert(isEmpty());

         assert(sig.equals(basicTypeSignature()));

     }

     private static Name[] buildEmptyNames(int arity, String basicTypeSignature) {

         assert(isValidSignature(basicTypeSignature));

         int resultPos = arity + 1;  // skip '_'

         if (arity < 0 || basicTypeSignature.length() != resultPos+1)

             throw new IllegalArgumentException("bad arity for "+basicTypeSignature);

         int numRes = (basicTypeSignature.charAt(resultPos) == 'V' ? 0 : 1);

         Name[] names = arguments(numRes, basicTypeSignature.substring(0, arity));

         for (int i = 0; i < numRes; i++) {

             names[arity + i] = constantZero(arity + i, basicTypeSignature.charAt(resultPos + i));

         }

         return names;

     }

     private static int fixResult(int result, Name[] names) {

         if (result >= 0) {

             if (names[result].type == 'V')

                 return -1;

         } else if (result == LAST_RESULT) {

             return names.length - 1;

         }

         return result;

     }

     private static boolean namesOK(int arity, Name[] names) {

         for (int i = 0; i < names.length; i++) {

             Name n = names[i];

             assert(n != null) : "n is null";

             if (i < arity)

                 assert( n.isParam()) : n + " is not param at " + i;

             else

                 assert(!n.isParam()) : n + " is param at " + i;

         }

         return true;

     }

     /** Renumber and/or replace params so that they are interned and canonically numbered. */

     private void normalize() {

         Name[] oldNames = null;

         int changesStart = 0;

         for (int i = 0; i < names.length; i++) {

             Name n = names[i];

             if (!n.initIndex(i)) {

                 if (oldNames == null) {

                     oldNames = names.clone();

                     changesStart = i;

                 }

                 names[i] = n.cloneWithIndex(i);

             }

         }

         if (oldNames != null) {

             int startFixing = arity;

             if (startFixing <= changesStart)

                 startFixing = changesStart+1;

             for (int i = startFixing; i < names.length; i++) {

                 Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);

                 names[i] = fixed.newIndex(i);

             }

         }

         assert(nameRefsAreLegal());

         int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);

         boolean needIntern = false;

         for (int i = 0; i < maxInterned; i++) {

             Name n = names[i], n2 = internArgument(n);

             if (n != n2) {

                 names[i] = n2;

                 needIntern = true;

             }

         }

         if (needIntern) {

             for (int i = arity; i < names.length; i++) {

                 names[i].internArguments();

             }

             assert(nameRefsAreLegal());

         }

     }

     /**

      * Check that all embedded Name references are localizable to this lambda,

      * and are properly ordered after their corresponding definitions.

      * <p>

      * Note that a Name can be local to multiple lambdas, as long as

      * it possesses the same index in each use site.

      * This allows Name references to be freely reused to construct

      * fresh lambdas, without confusion.

      */

     private boolean nameRefsAreLegal() {

         assert(arity >= 0 && arity <= names.length);

         assert(result >= -1 && result < names.length);

         // Do all names possess an index consistent with their local definition order?

         for (int i = 0; i < arity; i++) {

             Name n = names[i];

             assert(n.index() == i) : Arrays.asList(n.index(), i);

             assert(n.isParam());

         }

         // Also, do all local name references

         for (int i = arity; i < names.length; i++) {

             Name n = names[i];

             assert(n.index() == i);

             for (Object arg : n.arguments) {

                 if (arg instanceof Name) {

                     Name n2 = (Name) arg;

                     int i2 = n2.index;

                     assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;

                     assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);

                     assert(i2 < i);  // ref must come after def!

                 }

             }

         }

         return true;

     }

     /** Invoke this form on the given arguments. */

     // final Object invoke(Object... args) throws Throwable {

     //     // NYI: fit this into the fast path?

     //     return interpretWithArguments(args);

     // }

     /** Report the return type. */

     char returnType() {

         if (result < 0)  return 'V';

         Name n = names[result];

         return n.type;

     }

     /** Report the N-th argument type. */

     char parameterType(int n) {

         assert(n < arity);

         return names[n].type;

     }

     /** Report the arity. */

     int arity() {

         return arity;

     }

     /** Return the method type corresponding to my basic type signature. */

     MethodType methodType() {

         return signatureType(basicTypeSignature());

     }

     /** Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character. */

     final String basicTypeSignature() {

         StringBuilder buf = new StringBuilder(arity() + 3);

         for (int i = 0, a = arity(); i < a; i++)

             buf.append(parameterType(i));

         return buf.append('_').append(returnType()).toString();

     }

     static int signatureArity(String sig) {

         assert(isValidSignature(sig));

         return sig.indexOf('_');

     }

     static char signatureReturn(String sig) {

         return sig.charAt(signatureArity(sig)+1);

     }

     static boolean isValidSignature(String sig) {

         int arity = sig.indexOf('_');

         if (arity < 0)  return false;  // must be of the form *_*

         int siglen = sig.length();

         if (siglen != arity + 2)  return false;  // *_X

         for (int i = 0; i < siglen; i++) {

             if (i == arity)  continue;  // skip '_'

             char c = sig.charAt(i);

             if (c == 'V')

                 return (i == siglen - 1 && arity == siglen - 2);

             if (ALL_TYPES.indexOf(c) < 0)  return false; // must be [LIJFD]

         }

         return true;  // [LIJFD]*_[LIJFDV]

     }

     static Class<?> typeClass(char t) {

         switch (t) {

         case 'I': return int.class;

         case 'J': return long.class;

         case 'F': return float.class;

         case 'D': return double.class;

         case 'L': return Object.class;

         case 'V': return void.class;

         default: assert false;

         }

         return null;

     }

     static MethodType signatureType(String sig) {

         Class<?>[] ptypes = new Class<?>[signatureArity(sig)];

         for (int i = 0; i < ptypes.length; i++)

             ptypes[i] = typeClass(sig.charAt(i));

         Class<?> rtype = typeClass(signatureReturn(sig));

         return MethodType.methodType(rtype, ptypes);

     }

     /*

      * Code generation issues:

      *

      * Compiled LFs should be reusable in general.

      * The biggest issue is how to decide when to pull a name into

      * the bytecode, versus loading a reified form from the MH data.

      *

      * For example, an asType wrapper may require execution of a cast

      * after a call to a MH.  The target type of the cast can be placed

      * as a constant in the LF itself.  This will force the cast type

      * to be compiled into the bytecodes and native code for the MH.

      * Or, the target type of the cast can be erased in the LF, and

      * loaded from the MH data.  (Later on, if the MH as a whole is

      * inlined, the data will flow into the inlined instance of the LF,

      * as a constant, and the end result will be an optimal cast.)

      *

      * This erasure of cast types can be done with any use of

      * reference types.  It can also be done with whole method

      * handles.  Erasing a method handle might leave behind

      * LF code that executes correctly for any MH of a given

      * type, and load the required MH from the enclosing MH's data.

      * Or, the erasure might even erase the expected MT.

      *

      * Also, for direct MHs, the MemberName of the target

      * could be erased, and loaded from the containing direct MH.

      * As a simple case, a LF for all int-valued non-static

      * field getters would perform a cast on its input argument

      * (to non-constant base type derived from the MemberName)

      * and load an integer value from the input object

      * (at a non-constant offset also derived from the MemberName).

      * Such MN-erased LFs would be inlinable back to optimized

      * code, whenever a constant enclosing DMH is available

      * to supply a constant MN from its data.

      *

      * The main problem here is to keep LFs reasonably generic,

      * while ensuring that hot spots will inline good instances.

      * "Reasonably generic" means that we don't end up with

      * repeated versions of bytecode or machine code that do

      * not differ in their optimized form.  Repeated versions

      * of machine would have the undesirable overheads of

      * (a) redundant compilation work and (b) extra I$ pressure.

      * To control repeated versions, we need to be ready to

      * erase details from LFs and move them into MH data,

      * whevener those details are not relevant to significant

      * optimization.  "Significant" means optimization of

      * code that is actually hot.

      *

      * Achieving this may require dynamic splitting of MHs, by replacing

      * a generic LF with a more specialized one, on the same MH,

      * if (a) the MH is frequently executed and (b) the MH cannot

      * be inlined into a containing caller, such as an invokedynamic.

      *

      * Compiled LFs that are no longer used should be GC-able.

      * If they contain non-BCP references, they should be properly

      * interlinked with the class loader(s) that their embedded types

      * depend on.  This probably means that reusable compiled LFs

      * will be tabulated (indexed) on relevant class loaders,

      * or else that the tables that cache them will have weak links.

      */

     /**

      * Make this LF directly executable, as part of a MethodHandle.

      * Invariant:  Every MH which is invoked must prepare its LF

      * before invocation.

      * (In principle, the JVM could do this very lazily,

      * as a sort of pre-invocation linkage step.)

      */

     public void prepare() {

         if (COMPILE_THRESHOLD == 0) {

             compileToBytecode();

         }

         if (this.vmentry != null) {

             // already prepared (e.g., a primitive DMH invoker form)

             return;

         }

         LambdaForm prep = getPreparedForm(basicTypeSignature());

         this.vmentry = prep.vmentry;

         // TO DO: Maybe add invokeGeneric, invokeWithArguments

     }

     /** Generate optimizable bytecode for this form. */

     MemberName compileToBytecode() {

         MethodType invokerType = methodType();

         assert(vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));

         if (vmentry != null && isCompiled) {

             return vmentry;  // already compiled somehow

         }

         throw newInternalError("compileToBytecode", new Exception());

 //        try {

 //            vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);

 //            if (TRACE_INTERPRETER)

 //                traceInterpreter("compileToBytecode", this);

 //            isCompiled = true;

 //            return vmentry;

 //        } catch (Error | Exception ex) {

 //            throw newInternalError("compileToBytecode", ex);

 //        }

     }

     private static final ConcurrentHashMap<String,LambdaForm> PREPARED_FORMS;

     static {

         int   capacity   = 512;    // expect many distinct signatures over time

         float loadFactor = 0.75f;  // normal default

         int   writers    = 1;

         PREPARED_FORMS = new ConcurrentHashMap<>(capacity, loadFactor, writers);

     }

     private static Map<String,LambdaForm> computeInitialPreparedForms() {

         // Find all predefined invokers and associate them with canonical empty lambda forms.

         HashMap<String,LambdaForm> forms = new HashMap<>();

         for (MemberName m : MemberName.getFactory().getMethods(LambdaForm.class, false, null, null, null)) {

             if (!m.isStatic() || !m.isPackage())  continue;

             MethodType mt = m.getMethodType();

             if (mt.parameterCount() > 0 &&

                 mt.parameterType(0) == MethodHandle.class &&

                 m.getName().startsWith("interpret_")) {

                 String sig = basicTypeSignature(mt);

                 assert(m.getName().equals("interpret" + sig.substring(sig.indexOf('_'))));

                 LambdaForm form = new LambdaForm(sig);

                 form.vmentry = m;

                 mt.form().setCachedLambdaForm(MethodTypeForm.LF_COUNTER, form);

                 // FIXME: get rid of PREPARED_FORMS; use MethodTypeForm cache only

                 forms.put(sig, form);

             }

         }

         //System.out.println("computeInitialPreparedForms => "+forms);

         return forms;

     }

     // Set this false to disable use of the interpret_L methods defined in this file.

     private static final boolean USE_PREDEFINED_INTERPRET_METHODS = true;

     // The following are predefined exact invokers.  The system must build

     // a separate invoker for each distinct signature.

     static Object interpret_L(MethodHandle mh) throws Throwable {

         Object[] av = {mh};

         String sig = null;

         assert(argumentTypesMatch(sig = "L_L", av));

         Object res = mh.form.interpretWithArguments(av);

         assert(returnTypesMatch(sig, av, res));

         return res;

     }

     static Object interpret_L(MethodHandle mh, Object x1) throws Throwable {

         Object[] av = {mh, x1};

         String sig = null;

         assert(argumentTypesMatch(sig = "LL_L", av));

         Object res = mh.form.interpretWithArguments(av);

         assert(returnTypesMatch(sig, av, res));

         return res;

     }

     static Object interpret_L(MethodHandle mh, Object x1, Object x2) throws Throwable {

         Object[] av = {mh, x1, x2};

         String sig = null;

         assert(argumentTypesMatch(sig = "LLL_L", av));

         Object res = mh.form.interpretWithArguments(av);

         assert(returnTypesMatch(sig, av, res));

         return res;

     }

     private static LambdaForm getPreparedForm(String sig) {

         MethodType mtype = signatureType(sig);

         //LambdaForm prep = PREPARED_FORMS.get(sig);

         LambdaForm prep =  mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);

         if (prep != null)  return prep;

         assert(isValidSignature(sig));

         prep = new LambdaForm(sig);

 //        prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(sig);

         if (true) throw new IllegalStateException();

         //LambdaForm prep2 = PREPARED_FORMS.putIfAbsent(sig.intern(), prep);

         return mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);

     }

     // The next few routines are called only from assert expressions

     // They verify that the built-in invokers process the correct raw data types.

     private static boolean argumentTypesMatch(String sig, Object[] av) {

         int arity = signatureArity(sig);

         assert(av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;

         assert(av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];

         MethodHandle mh = (MethodHandle) av[0];

         MethodType mt = mh.type();

         assert(mt.parameterCount() == arity-1);

         for (int i = 0; i < av.length; i++) {

             Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i-1));

             assert(valueMatches(sig.charAt(i), pt, av[i]));

         }

         return true;

     }

     private static boolean valueMatches(char tc, Class<?> type, Object x) {

         // The following line is needed because (...)void method handles can use non-void invokers

         if (type == void.class)  tc = 'V';   // can drop any kind of value

         assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);

         switch (tc) {

         case 'I': assert checkInt(type, x)   : "checkInt(" + type + "," + x +")";   break;

         case 'J': assert x instanceof Long   : "instanceof Long: " + x;             break;

         case 'F': assert x instanceof Float  : "instanceof Float: " + x;            break;

         case 'D': assert x instanceof Double : "instanceof Double: " + x;           break;

         case 'L': assert checkRef(type, x)   : "checkRef(" + type + "," + x + ")";  break;

         case 'V': break;  // allow anything here; will be dropped

         default:  assert(false);

         }

         return true;

     }

     private static boolean returnTypesMatch(String sig, Object[] av, Object res) {

         MethodHandle mh = (MethodHandle) av[0];

         return valueMatches(signatureReturn(sig), mh.type().returnType(), res);

     }

     private static boolean checkInt(Class<?> type, Object x) {

         assert(x instanceof Integer);

         if (type == int.class)  return true;

         Wrapper w = Wrapper.forBasicType(type);

         assert(w.isSubwordOrInt());

         Object x1 = Wrapper.INT.wrap(w.wrap(x));

         return x.equals(x1);

     }

     private static boolean checkRef(Class<?> type, Object x) {

         assert(!type.isPrimitive());

         if (x == null)  return true;

         if (type.isInterface())  return true;

         return type.isInstance(x);

     }

     /** If the invocation count hits the threshold we spin bytecodes and call that subsequently. */

     private static final int COMPILE_THRESHOLD;

     static {

         if (MethodHandleStatics.COMPILE_THRESHOLD != null)

             COMPILE_THRESHOLD = MethodHandleStatics.COMPILE_THRESHOLD;

         else

             COMPILE_THRESHOLD = 30;  // default value

     }

     private int invocationCounter = 0;

     @Hidden

     @DontInline

     /** Interpretively invoke this form on the given arguments. */

     Object interpretWithArguments(Object... argumentValues) throws Throwable {

         if (TRACE_INTERPRETER)

             return interpretWithArgumentsTracing(argumentValues);

         checkInvocationCounter();

         assert(arityCheck(argumentValues));

         Object[] values = Arrays.copyOf(argumentValues, names.length);

         for (int i = argumentValues.length; i < values.length; i++) {

             values[i] = interpretName(names[i], values);

         }

         return (result < 0) ? null : values[result];

     }

     @Hidden

     @DontInline

     /** Evaluate a single Name within this form, applying its function to its arguments. */

     Object interpretName(Name name, Object[] values) throws Throwable {

         if (TRACE_INTERPRETER)

             traceInterpreter("| interpretName", name.debugString(), (Object[]) null);

         Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);

         for (int i = 0; i < arguments.length; i++) {

             Object a = arguments[i];

             if (a instanceof Name) {

                 int i2 = ((Name)a).index();

                 assert(names[i2] == a);

                 a = values[i2];

                 arguments[i] = a;

             }

         }

         return name.function.invokeWithArguments(arguments);

     }

     private void checkInvocationCounter() {

         if (COMPILE_THRESHOLD != 0 &&

             invocationCounter < COMPILE_THRESHOLD) {

             invocationCounter++;  // benign race

             if (invocationCounter >= COMPILE_THRESHOLD) {

                 // Replace vmentry with a bytecode version of this LF.

                 compileToBytecode();

             }

         }

     }

     Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {

         traceInterpreter("[ interpretWithArguments", this, argumentValues);

         if (invocationCounter < COMPILE_THRESHOLD) {

             int ctr = invocationCounter++;  // benign race

             traceInterpreter("| invocationCounter", ctr);

             if (invocationCounter >= COMPILE_THRESHOLD) {

                 compileToBytecode();

             }

         }

         Object rval;

         try {

             assert(arityCheck(argumentValues));

             Object[] values = Arrays.copyOf(argumentValues, names.length);

             for (int i = argumentValues.length; i < values.length; i++) {

                 values[i] = interpretName(names[i], values);

             }

             rval = (result < 0) ? null : values[result];

         } catch (Throwable ex) {

             traceInterpreter("] throw =>", ex);

             throw ex;

         }

         traceInterpreter("] return =>", rval);

         return rval;

     }

     //** This transform is applied (statically) to every name.function. */

     /*

     private static MethodHandle eraseSubwordTypes(MethodHandle mh) {

         MethodType mt = mh.type();

         if (mt.hasPrimitives()) {

             mt = mt.changeReturnType(eraseSubwordType(mt.returnType()));

             for (int i = 0; i < mt.parameterCount(); i++) {

                 mt = mt.changeParameterType(i, eraseSubwordType(mt.parameterType(i)));

             }

             mh = MethodHandles.explicitCastArguments(mh, mt);

         }

         return mh;

     }

     private static Class<?> eraseSubwordType(Class<?> type) {

         if (!type.isPrimitive())  return type;

         if (type == int.class)  return type;

         Wrapper w = Wrapper.forPrimitiveType(type);

         if (w.isSubwordOrInt())  return int.class;

         return type;

     }

     */

     static void traceInterpreter(String event, Object obj, Object... args) {

         if (TRACE_INTERPRETER) {

             System.out.println("LFI: "+event+" "+(obj != null ? obj : "")+(args != null && args.length != 0 ? Arrays.asList(args) : ""));

         }

     }

     static void traceInterpreter(String event, Object obj) {

         traceInterpreter(event, obj, (Object[])null);

     }

     private boolean arityCheck(Object[] argumentValues) {

         assert(argumentValues.length == arity) : arity+"!="+Arrays.asList(argumentValues)+".length";

         // also check that the leading (receiver) argument is somehow bound to this LF:

         assert(argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];

         assert(((MethodHandle)argumentValues[0]).internalForm() == this);

         // note:  argument #0 could also be an interface wrapper, in the future

         return true;

     }

     private boolean isEmpty() {

         if (result < 0)

             return (names.length == arity);

         else if (result == arity && names.length == arity + 1)

             return names[arity].isConstantZero();

         else

             return false;

     }

     public String toString() {

         StringBuilder buf = new StringBuilder(debugName+"=Lambda(");

         for (int i = 0; i < names.length; i++) {

             if (i == arity)  buf.append(")=>{");

             Name n = names[i];

             if (i >= arity)  buf.append("\n    ");

             buf.append(n);

             if (i < arity) {

                 if (i+1 < arity)  buf.append(",");

                 continue;

             }

             buf.append("=").append(n.exprString());

             buf.append(";");

         }

         buf.append(result < 0 ? "void" : names[result]).append("}");

         if (TRACE_INTERPRETER) {

             // Extra verbosity:

             buf.append(":").append(basicTypeSignature());

             buf.append("/").append(vmentry);

         }

         return buf.toString();

     }

     /**

      * Apply immediate binding for a Name in this form indicated by its position relative to the form.

      * The first parameter to a LambdaForm, a0:L, always represents the form's method handle, so 0 is not

      * accepted as valid.

      */

     LambdaForm bindImmediate(int pos, char basicType, Object value) {

         // must be an argument, and the types must match

         assert pos > 0 && pos < arity && names[pos].type == basicType && Name.typesMatch(basicType, value);

         int arity2 = arity - 1;

         Name[] names2 = new Name[names.length - 1];

         for (int r = 0, w = 0; r < names.length; ++r, ++w) { // (r)ead from names, (w)rite to names2

             Name n = names[r];

             if (n.isParam()) {

                 if (n.index == pos) {

                     // do not copy over the argument that is to be replaced with a literal,

                     // but adjust the write index

                     --w;

                 } else {

                     names2[w] = new Name(w, n.type);

                 }

             } else {

                 Object[] arguments2 = new Object[n.arguments.length];

                 for (int i = 0; i < n.arguments.length; ++i) {

                     Object arg = n.arguments[i];

                     if (arg instanceof Name) {

                         int ni = ((Name) arg).index;

                         if (ni == pos) {

                             arguments2[i] = value;

                         } else if (ni < pos) {

                             // replacement position not yet passed

                             arguments2[i] = names2[ni];

                         } else {

                             // replacement position passed

                             arguments2[i] = names2[ni - 1];

                         }

                     } else {

                         arguments2[i] = arg;

                     }

                 }

                 names2[w] = new Name(n.function, arguments2);

                 names2[w].initIndex(w);

             }

         }

         int result2 = result == -1 ? -1 : result - 1;

         return new LambdaForm(debugName, arity2, names2, result2);

     }

     LambdaForm bind(int namePos, BoundMethodHandle.SpeciesData oldData) {

         Name name = names[namePos];

         BoundMethodHandle.SpeciesData newData = oldData.extendWithType(name.type);

         return bind(name, newData.getterName(names[0], oldData.fieldCount()), oldData, newData);

     }

     LambdaForm bind(Name name, Name binding,

                     BoundMethodHandle.SpeciesData oldData,

                     BoundMethodHandle.SpeciesData newData) {

         int pos = name.index;

         assert(name.isParam());

         assert(!binding.isParam());

         assert(name.type == binding.type);

         assert(0 <= pos && pos < arity && names[pos] == name);

         assert(binding.function.memberDeclaringClassOrNull() == newData.clazz);

         assert(oldData.getters.length == newData.getters.length-1);

         if (bindCache != null) {

             LambdaForm form = bindCache[pos];

             if (form != null) {

                 assert(form.contains(binding)) : "form << " + form + " >> does not contain binding << " + binding + " >>";

                 return form;

             }

         } else {

             bindCache = new LambdaForm[arity];

         }

         assert(nameRefsAreLegal());

         int arity2 = arity-1;

         Name[] names2 = names.clone();

         names2[pos] = binding;  // we might move this in a moment

         // The newly created LF will run with a different BMH.

         // Switch over any pre-existing BMH field references to the new BMH class.

         int firstOldRef = -1;

         for (int i = 0; i < names2.length; i++) {

             Name n = names[i];

             if (n.function != null &&

                 n.function.memberDeclaringClassOrNull() == oldData.clazz) {

                 MethodHandle oldGetter = n.function.resolvedHandle;

                 MethodHandle newGetter = null;

                 for (int j = 0; j < oldData.getters.length; j++) {

                     if (oldGetter == oldData.getters[j])

                         newGetter =  newData.getters[j];

                 }

                 if (newGetter != null) {

                     if (firstOldRef < 0)  firstOldRef = i;

                     Name n2 = new Name(newGetter, n.arguments);

                     names2[i] = n2;

                 }

             }

         }

         // Walk over the new list of names once, in forward order.

         // Replace references to 'name' with 'binding'.

         // Replace data structure references to the old BMH species with the new.

         // This might cause a ripple effect, but it will settle in one pass.

         assert(firstOldRef < 0 || firstOldRef > pos);

         for (int i = pos+1; i < names2.length; i++) {

             if (i <= arity2)  continue;

             names2[i] = names2[i].replaceNames(names, names2, pos, i);

         }

         //  (a0, a1, name=a2, a3, a4)  =>  (a0, a1, a3, a4, binding)

         int insPos = pos;

         for (; insPos+1 < names2.length; insPos++) {

             Name n = names2[insPos+1];

             if (n.isSiblingBindingBefore(binding)) {

                 names2[insPos] = n;

             } else {

                 break;

             }

         }

         names2[insPos] = binding;

         // Since we moved some stuff, maybe update the result reference:

         int result2 = result;

         if (result2 == pos)

             result2 = insPos;

         else if (result2 > pos && result2 <= insPos)

             result2 -= 1;

         return bindCache[pos] = new LambdaForm(debugName, arity2, names2, result2);

     }

     boolean contains(Name name) {

         int pos = name.index();

         if (pos >= 0) {

             return pos < names.length && name.equals(names[pos]);

         }

         for (int i = arity; i < names.length; i++) {

             if (name.equals(names[i]))

                 return true;

         }

         return false;

     }

     LambdaForm addArguments(int pos, char... types) {

         assert(pos <= arity);

         int length = names.length;

         int inTypes = types.length;

         Name[] names2 = Arrays.copyOf(names, length + inTypes);

         int arity2 = arity + inTypes;

         int result2 = result;

         if (result2 >= arity)

             result2 += inTypes;

         // names array has MH in slot 0; skip it.

         int argpos = pos + 1;

         // Note:  The LF constructor will rename names2[argpos...].

         // Make space for new arguments (shift temporaries).

         System.arraycopy(names, argpos, names2, argpos + inTypes, length - argpos);

         for (int i = 0; i < inTypes; i++) {

             names2[argpos + i] = new Name(types[i]);

         }

         return new LambdaForm(debugName, arity2, names2, result2);

     }

     LambdaForm addArguments(int pos, List<Class<?>> types) {

         char[] basicTypes = new char[types.size()];

         for (int i = 0; i < basicTypes.length; i++)

             basicTypes[i] = basicType(types.get(i));

         return addArguments(pos, basicTypes);

     }

     LambdaForm permuteArguments(int skip, int[] reorder, char[] types) {

         // Note:  When inArg = reorder[outArg], outArg is fed by a copy of inArg.

         // The types are the types of the new (incoming) arguments.

         int length = names.length;

         int inTypes = types.length;

         int outArgs = reorder.length;

         assert(skip+outArgs == arity);

         assert(permutedTypesMatch(reorder, types, names, skip));

         int pos = 0;

         // skip trivial first part of reordering:

         while (pos < outArgs && reorder[pos] == pos)  pos += 1;

         Name[] names2 = new Name[length - outArgs + inTypes];

         System.arraycopy(names, 0, names2, 0, skip+pos);

         // copy the body:

         int bodyLength = length - arity;

         System.arraycopy(names, skip+outArgs, names2, skip+inTypes, bodyLength);

         int arity2 = names2.length - bodyLength;

         int result2 = result;

         if (result2 >= 0) {

             if (result2 < skip+outArgs) {

                 // return the corresponding inArg

                 result2 = reorder[result2-skip];

             } else {

                 result2 = result2 - outArgs + inTypes;

             }

         }

         // rework names in the body:

         for (int j = pos; j < outArgs; j++) {

             Name n = names[skip+j];

             int i = reorder[j];

             // replace names[skip+j] by names2[skip+i]

             Name n2 = names2[skip+i];

             if (n2 == null)

                 names2[skip+i] = n2 = new Name(types[i]);

             else

                 assert(n2.type == types[i]);

             for (int k = arity2; k < names2.length; k++) {

                 names2[k] = names2[k].replaceName(n, n2);

             }

         }

         // some names are unused, but must be filled in

         for (int i = skip+pos; i < arity2; i++) {

             if (names2[i] == null)

                 names2[i] = argument(i, types[i - skip]);

         }

         for (int j = arity; j < names.length; j++) {

             int i = j - arity + arity2;

             // replace names2[i] by names[j]

             Name n = names[j];

             Name n2 = names2[i];

             if (n != n2) {

                 for (int k = i+1; k < names2.length; k++) {

                     names2[k] = names2[k].replaceName(n, n2);

                 }

             }

         }

         return new LambdaForm(debugName, arity2, names2, result2);

     }

     static boolean permutedTypesMatch(int[] reorder, char[] types, Name[] names, int skip) {

         int inTypes = types.length;

         int outArgs = reorder.length;

         for (int i = 0; i < outArgs; i++) {

             assert(names[skip+i].isParam());

             assert(names[skip+i].type == types[reorder[i]]);

         }

         return true;

     }

     static class NamedFunction {

         final MemberName member;

         @Stable MethodHandle resolvedHandle;

         @Stable MethodHandle invoker;

         NamedFunction(MethodHandle resolvedHandle) {

             this(resolvedHandle.internalMemberName(), resolvedHandle);

         }

         NamedFunction(MemberName member, MethodHandle resolvedHandle) {

             this.member = member;

             //resolvedHandle = eraseSubwordTypes(resolvedHandle);

             this.resolvedHandle = resolvedHandle;

         }

         NamedFunction(MethodType basicInvokerType) {

             assert(basicInvokerType == basicInvokerType.basicType()) : basicInvokerType;

             if (basicInvokerType.parameterSlotCount() < MethodType.MAX_MH_INVOKER_ARITY) {

                 this.resolvedHandle = basicInvokerType.invokers().basicInvoker();

                 this.member = resolvedHandle.internalMemberName();

             } else {

                 // necessary to pass BigArityTest

                 this.member = Invokers.invokeBasicMethod(basicInvokerType);

             }

         }

         // The next 3 constructors are used to break circular dependencies on MH.invokeStatic, etc.

         // Any LambdaForm containing such a member is not interpretable.

         // This is OK, since all such LFs are prepared with special primitive vmentry points.

         // And even without the resolvedHandle, the name can still be compiled and optimized.

         NamedFunction(Method method) {

             this(new MemberName(method));

         }

         NamedFunction(Field field) {

             this(new MemberName(field));

         }

         NamedFunction(MemberName member) {

             this.member = member;

             this.resolvedHandle = null;

         }

         MethodHandle resolvedHandle() {

             if (resolvedHandle == null)  resolve();

             return resolvedHandle;

         }

         void resolve() {

             resolvedHandle = DirectMethodHandle.make(member);

         }

         @Override

         public boolean equals(Object other) {

             if (this == other) return true;

             if (other == null) return false;

             if (!(other instanceof NamedFunction)) return false;

             NamedFunction that = (NamedFunction) other;

             return this.member != null && this.member.equals(that.member);

         }

         @Override

         public int hashCode() {

             if (member != null)

                 return member.hashCode();

             return super.hashCode();

         }

         // Put the predefined NamedFunction invokers into the table.

         static void initializeInvokers() {

             for (MemberName m : MemberName.getFactory().getMethods(NamedFunction.class, false, null, null, null)) {

                 if (!m.isStatic() || !m.isPackage())  continue;

                 MethodType type = m.getMethodType();

                 if (type.equals(INVOKER_METHOD_TYPE) &&

                     m.getName().startsWith("invoke_")) {

                     String sig = m.getName().substring("invoke_".length());

                     int arity = LambdaForm.signatureArity(sig);

                     MethodType srcType = MethodType.genericMethodType(arity);

                     if (LambdaForm.signatureReturn(sig) == 'V')

                         srcType = srcType.changeReturnType(void.class);

                     MethodTypeForm typeForm = srcType.form();

                     typeForm.namedFunctionInvoker = DirectMethodHandle.make(m);

                 }

             }

         }

         // The following are predefined NamedFunction invokers.  The system must build

         // a separate invoker for each distinct signature.

         /** void return type invokers. */

         @Hidden

         static Object invoke__V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 0);

             mh.invokeBasic();

             return null;

         }

         @Hidden

         static Object invoke_L_V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 1);

             mh.invokeBasic(a[0]);

             return null;

         }

         @Hidden

         static Object invoke_LL_V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 2);

             mh.invokeBasic(a[0], a[1]);

             return null;

         }

         @Hidden

         static Object invoke_LLL_V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 3);

             mh.invokeBasic(a[0], a[1], a[2]);

             return null;

         }

         @Hidden

         static Object invoke_LLLL_V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 4);

             mh.invokeBasic(a[0], a[1], a[2], a[3]);

             return null;

         }

         @Hidden

         static Object invoke_LLLLL_V(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 5);

             mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);

             return null;

         }

         /** Object return type invokers. */

         @Hidden

         static Object invoke__L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 0);

             return mh.invokeBasic();

         }

         @Hidden

         static Object invoke_L_L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 1);

             return mh.invokeBasic(a[0]);

         }

         @Hidden

         static Object invoke_LL_L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 2);

             return mh.invokeBasic(a[0], a[1]);

         }

         @Hidden

         static Object invoke_LLL_L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 3);

             return mh.invokeBasic(a[0], a[1], a[2]);

         }

         @Hidden

         static Object invoke_LLLL_L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 4);

             return mh.invokeBasic(a[0], a[1], a[2], a[3]);

         }

         @Hidden

         static Object invoke_LLLLL_L(MethodHandle mh, Object[] a) throws Throwable {

             assert(a.length == 5);

             return mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);

         }

         static final MethodType INVOKER_METHOD_TYPE =

             MethodType.methodType(Object.class, MethodHandle.class, Object[].class);

         private static MethodHandle computeInvoker(MethodTypeForm typeForm) {

             MethodHandle mh = typeForm.namedFunctionInvoker;

             if (mh != null)  return mh;

 //            MemberName invoker = InvokerBytecodeGenerator.generateNamedFunctionInvoker(typeForm);  // this could take a while

             if (true) throw new IllegalStateException();

 //            mh = DirectMethodHandle.make(invoker);

             MethodHandle mh2 = typeForm.namedFunctionInvoker;

             if (mh2 != null)  return mh2;  // benign race

             if (!mh.type().equals(INVOKER_METHOD_TYPE))

                 throw new InternalError(mh.debugString());

             return typeForm.namedFunctionInvoker = mh;

         }

         @Hidden

         Object invokeWithArguments(Object... arguments) throws Throwable {

             // If we have a cached invoker, call it right away.

             // NOTE: The invoker always returns a reference value.

             if (TRACE_INTERPRETER)  return invokeWithArgumentsTracing(arguments);

             assert(checkArgumentTypes(arguments, methodType()));

             return invoker().invokeBasic(resolvedHandle(), arguments);

         }

         @Hidden

         Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {

             Object rval;

             try {

                 traceInterpreter("[ call", this, arguments);

                 if (invoker == null) {

                     traceInterpreter("| getInvoker", this);

                     invoker();

                 }

                 if (resolvedHandle == null) {

                     traceInterpreter("| resolve", this);

                     resolvedHandle();

                 }

                 assert(checkArgumentTypes(arguments, methodType()));

                 rval = invoker().invokeBasic(resolvedHandle(), arguments);

             } catch (Throwable ex) {

                 traceInterpreter("] throw =>", ex);

                 throw ex;

             }

             traceInterpreter("] return =>", rval);

             return rval;

         }

         private MethodHandle invoker() {

             if (invoker != null)  return invoker;

             // Get an invoker and cache it.

             return invoker = computeInvoker(methodType().form());

         }

         private static boolean checkArgumentTypes(Object[] arguments, MethodType methodType) {

             if (true)  return true;  // FIXME

             MethodType dstType = methodType.form().erasedType();

             MethodType srcType = dstType.basicType().wrap();

             Class<?>[] ptypes = new Class<?>[arguments.length];

             for (int i = 0; i < arguments.length; i++) {

                 Object arg = arguments[i];

                 Class<?> ptype = arg == null ? Object.class : arg.getClass();

                 // If the dest. type is a primitive we keep the

                 // argument type.

                 ptypes[i] = dstType.parameterType(i).isPrimitive() ? ptype : Object.class;

             }

             MethodType argType = MethodType.methodType(srcType.returnType(), ptypes).wrap();

             assert(argType.isConvertibleTo(srcType)) : "wrong argument types: cannot convert " + argType + " to " + srcType;

             return true;

         }

         String basicTypeSignature() {

             //return LambdaForm.basicTypeSignature(resolvedHandle.type());

             return LambdaForm.basicTypeSignature(methodType());

         }

         MethodType methodType() {

             if (resolvedHandle != null)

                 return resolvedHandle.type();

             else

                 // only for certain internal LFs during bootstrapping

                 return member.getInvocationType();

         }

         MemberName member() {

             assert(assertMemberIsConsistent());

             return member;

         }

         // Called only from assert.

         private boolean assertMemberIsConsistent() {

             if (resolvedHandle instanceof DirectMethodHandle) {

                 MemberName m = resolvedHandle.internalMemberName();

                 assert(m.equals(member));

             }

             return true;

         }

         Class<?> memberDeclaringClassOrNull() {

             return (member == null) ? null : member.getDeclaringClass();

         }

         char returnType() {

             return basicType(methodType().returnType());

         }

         char parameterType(int n) {

             return basicType(methodType().parameterType(n));

         }

         int arity() {

             //int siglen = member.getMethodType().parameterCount();

             //if (!member.isStatic())  siglen += 1;

             //return siglen;

             return methodType().parameterCount();

         }

         public String toString() {

             if (member == null)  return String.valueOf(resolvedHandle);

             return member.getDeclaringClass().getSimpleName()+"."+member.getName();

         }

     }

     void resolve() {

         for (Name n : names) n.resolve();

     }

     public static char basicType(Class<?> type) {

         char c = Wrapper.basicTypeChar(type);

         if ("ZBSC".indexOf(c) >= 0)  c = 'I';

         assert("LIJFDV".indexOf(c) >= 0);

         return c;

     }

     public static char[] basicTypes(List<Class<?>> types) {

         char[] btypes = new char[types.size()];

         for (int i = 0; i < btypes.length; i++) {

             btypes[i] = basicType(types.get(i));

         }

         return btypes;

     }

     public static String basicTypeSignature(MethodType type) {

         char[] sig = new char[type.parameterCount() + 2];

         int sigp = 0;

         for (Class<?> pt : type.parameterList()) {

             sig[sigp++] = basicType(pt);

         }

         sig[sigp++] = '_';

         sig[sigp++] = basicType(type.returnType());

         assert(sigp == sig.length);

         return String.valueOf(sig);

     }

     static final class Name {

         final char type;

         private short index;

         final NamedFunction function;

         @Stable final Object[] arguments;

         private Name(int index, char type, NamedFunction function, Object[] arguments) {

             this.index = (short)index;

             this.type = type;

             this.function = function;

             this.arguments = arguments;

             assert(this.index == index);

         }

         Name(MethodHandle function, Object... arguments) {

             this(new NamedFunction(function), arguments);

         }

         Name(MethodType functionType, Object... arguments) {

             this(new NamedFunction(functionType), arguments);

             assert(arguments[0] instanceof Name && ((Name)arguments[0]).type == 'L');

         }

         Name(MemberName function, Object... arguments) {

             this(new NamedFunction(function), arguments);

         }

         Name(NamedFunction function, Object... arguments) {

             this(-1, function.returnType(), function, arguments = arguments.clone());

             assert(arguments.length == function.arity()) : "arity mismatch: arguments.length=" + arguments.length + " == function.arity()=" + function.arity() + " in " + debugString();

             for (int i = 0; i < arguments.length; i++)

                 assert(typesMatch(function.parameterType(i), arguments[i])) : "types don't match: function.parameterType(" + i + ")=" + function.parameterType(i) + ", arguments[" + i + "]=" + arguments[i] + " in " + debugString();

         }

         Name(int index, char type) {

             this(index, type, null, null);

         }

         Name(char type) {

             this(-1, type);

         }

         char type() { return type; }

         int index() { return index; }

         boolean initIndex(int i) {

             if (index != i) {

                 if (index != -1)  return false;

                 index = (short)i;

             }

             return true;

         }

         void resolve() {

             if (function != null)

                 function.resolve();

         }

         Name newIndex(int i) {

             if (initIndex(i))  return this;

             return cloneWithIndex(i);

         }

         Name cloneWithIndex(int i) {

             Object[] newArguments = (arguments == null) ? null : arguments.clone();

             return new Name(i, type, function, newArguments);

         }

         Name replaceName(Name oldName, Name newName) {  // FIXME: use replaceNames uniformly

             if (oldName == newName)  return this;

             @SuppressWarnings("LocalVariableHidesMemberVariable")

             Object[] arguments = this.arguments;

             if (arguments == null)  return this;

             boolean replaced = false;

             for (int j = 0; j < arguments.length; j++) {

                 if (arguments[j] == oldName) {

                     if (!replaced) {

                         replaced = true;

                         arguments = arguments.clone();

                     }

                     arguments[j] = newName;

                 }

             }

             if (!replaced)  return this;

             return new Name(function, arguments);

         }

         Name replaceNames(Name[] oldNames, Name[] newNames, int start, int end) {

             @SuppressWarnings("LocalVariableHidesMemberVariable")

             Object[] arguments = this.arguments;

             boolean replaced = false;

         eachArg:

             for (int j = 0; j < arguments.length; j++) {

                 if (arguments[j] instanceof Name) {

                     Name n = (Name) arguments[j];

                     int check = n.index;

                     // harmless check to see if the thing is already in newNames:

                     if (check >= 0 && check < newNames.length && n == newNames[check])

                         continue eachArg;

                     // n might not have the correct index: n != oldNames[n.index].

                     for (int i = start; i < end; i++) {

                         if (n == oldNames[i]) {

                             if (n == newNames[i])

                                 continue eachArg;

                             if (!replaced) {

                                 replaced = true;

                                 arguments = arguments.clone();

                             }

                             arguments[j] = newNames[i];

                             continue eachArg;

                         }

                     }

                 }

             }

             if (!replaced)  return this;

             return new Name(function, arguments);

         }

         void internArguments() {

             @SuppressWarnings("LocalVariableHidesMemberVariable")

             Object[] arguments = this.arguments;

             for (int j = 0; j < arguments.length; j++) {

                 if (arguments[j] instanceof Name) {

                     Name n = (Name) arguments[j];

                     if (n.isParam() && n.index < INTERNED_ARGUMENT_LIMIT)

                         arguments[j] = internArgument(n);

                 }

             }

         }

         boolean isParam() {

             return function == null;

         }

         boolean isConstantZero() {

             return !isParam() && arguments.length == 0 && function.equals(constantZero(0, type).function);

         }

         public String toString() {

             return (isParam()?"a":"t")+(index >= 0 ? index : System.identityHashCode(this))+":"+type;

         }

         public String debugString() {

             String s = toString();

             return (function == null) ? s : s + "=" + exprString();

         }

         public String exprString() {

             if (function == null)  return "null";

             StringBuilder buf = new StringBuilder(function.toString());

             buf.append("(");

             String cma = "";

             for (Object a : arguments) {

                 buf.append(cma); cma = ",";

                 if (a instanceof Name || a instanceof Integer)

                     buf.append(a);

                 else

                     buf.append("(").append(a).append(")");

             }

             buf.append(")");

             return buf.toString();

         }

         private static boolean typesMatch(char parameterType, Object object) {

             if (object instanceof Name) {

                 return ((Name)object).type == parameterType;

             }

             switch (parameterType) {

                 case 'I':  return object instanceof Integer;

                 case 'J':  return object instanceof Long;

                 case 'F':  return object instanceof Float;

                 case 'D':  return object instanceof Double;

             }

             assert(parameterType == 'L');

             return true;

         }

         /**

          * Does this Name precede the given binding node in some canonical order?

          * This predicate is used to order data bindings (via insertion sort)

          * with some stability.

          */

         boolean isSiblingBindingBefore(Name binding) {

             assert(!binding.isParam());

             if (isParam())  return true;

             if (function.equals(binding.function) &&

                 arguments.length == binding.arguments.length) {

                 boolean sawInt = false;

                 for (int i = 0; i < arguments.length; i++) {

                     Object a1 = arguments[i];

                     Object a2 = binding.arguments[i];

                     if (!a1.equals(a2)) {

                         if (a1 instanceof Integer && a2 instanceof Integer) {

                             if (sawInt)  continue;

                             sawInt = true;

                             if ((int)a1 < (int)a2)  continue;  // still might be true

                         }

                         return false;

                     }

                 }

                 return sawInt;

             }

             return false;

         }

         public boolean equals(Name that) {

             if (this == that)  return true;

             if (isParam())

                 // each parameter is a unique atom

                 return false;  // this != that

             return

                 //this.index == that.index &&

                 this.type == that.type &&

                 this.function.equals(that.function) &&

                 Arrays.equals(this.arguments, that.arguments);

         }

         @Override

         public boolean equals(Object x) {

             return x instanceof Name && equals((Name)x);

         }

         @Override

         public int hashCode() {

             if (isParam())

                 return index | (type << 8);

             return function.hashCode() ^ Arrays.hashCode(arguments);

         }

     }

     static Name argument(int which, char type) {

         int tn = ALL_TYPES.indexOf(type);

         if (tn < 0 || which >= INTERNED_ARGUMENT_LIMIT)

             return new Name(which, type);

         return INTERNED_ARGUMENTS[tn][which];

     }

     static Name internArgument(Name n) {

         assert(n.isParam()) : "not param: " + n;

         assert(n.index < INTERNED_ARGUMENT_LIMIT);

         return argument(n.index, n.type);

     }

     static Name[] arguments(int extra, String types) {

         int length = types.length();

         Name[] names = new Name[length + extra];

         for (int i = 0; i < length; i++)

             names[i] = argument(i, types.charAt(i));

         return names;

     }

     static Name[] arguments(int extra, char... types) {

         int length = types.length;

         Name[] names = new Name[length + extra];

         for (int i = 0; i < length; i++)

             names[i] = argument(i, types[i]);

         return names;

     }

     static Name[] arguments(int extra, List<Class<?>> types) {

         int length = types.size();

         Name[] names = new Name[length + extra];

         for (int i = 0; i < length; i++)

             names[i] = argument(i, basicType(types.get(i)));

         return names;

     }

     static Name[] arguments(int extra, Class<?>... types) {

         int length = types.length;

         Name[] names = new Name[length + extra];

         for (int i = 0; i < length; i++)

             names[i] = argument(i, basicType(types[i]));

         return names;

     }

     static Name[] arguments(int extra, MethodType types) {

         int length = types.parameterCount();

         Name[] names = new Name[length + extra];

         for (int i = 0; i < length; i++)

             names[i] = argument(i, basicType(types.parameterType(i)));

         return names;

     }

     static final String ALL_TYPES = "LIJFD";  // omit V, not an argument type

     static final int INTERNED_ARGUMENT_LIMIT = 10;

     private static final Name[][] INTERNED_ARGUMENTS

             = new Name[ALL_TYPES.length()][INTERNED_ARGUMENT_LIMIT];

     static {

         for (int tn = 0; tn < ALL_TYPES.length(); tn++) {

             for (int i = 0; i < INTERNED_ARGUMENTS[tn].length; i++) {

                 char type = ALL_TYPES.charAt(tn);

                 INTERNED_ARGUMENTS[tn][i] = new Name(i, type);

             }

         }

     }

     private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();

     static Name constantZero(int which, char type) {

         return CONSTANT_ZERO[ALL_TYPES.indexOf(type)].newIndex(which);

     }

     private static final Name[] CONSTANT_ZERO

             = new Name[ALL_TYPES.length()];

     static {

         for (int tn = 0; tn < ALL_TYPES.length(); tn++) {

             char bt = ALL_TYPES.charAt(tn);

             Wrapper wrap = Wrapper.forBasicType(bt);

             MemberName zmem = new MemberName(LambdaForm.class, "zero"+bt, MethodType.methodType(wrap.primitiveType()), REF_invokeStatic);

             try {

                 zmem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, zmem, null, NoSuchMethodException.class);

             } catch (IllegalAccessException|NoSuchMethodException ex) {

                 throw newInternalError(ex);

             }

             NamedFunction zcon = new NamedFunction(zmem);

             Name n = new Name(zcon).newIndex(0);

             assert(n.type == ALL_TYPES.charAt(tn));

             CONSTANT_ZERO[tn] = n;

             assert(n.isConstantZero());

         }

     }

     // Avoid appealing to ValueConversions at bootstrap time:

     private static int zeroI() { return 0; }

     private static long zeroJ() { return 0; }

     private static float zeroF() { return 0; }

     private static double zeroD() { return 0; }

     private static Object zeroL() { return null; }

     // Put this last, so that previous static inits can run before.

     static {

         if (USE_PREDEFINED_INTERPRET_METHODS)

             PREPARED_FORMS.putAll(computeInitialPreparedForms());

     }

     /**

      * Internal marker for byte-compiled LambdaForms.

      */

     /*non-public*/

     @Target(ElementType.METHOD)

     @Retention(RetentionPolicy.RUNTIME)

     @interface Compiled {

     }

     /**

      * Internal marker for LambdaForm interpreter frames.

      */

     /*non-public*/

     @Target(ElementType.METHOD)

     @Retention(RetentionPolicy.RUNTIME)

     @interface Hidden {

     }

 /*

     // Smoke-test for the invokers used in this file.

     static void testMethodHandleLinkers() throws Throwable {

         MemberName.Factory lookup = MemberName.getFactory();

         MemberName asList_MN = new MemberName(Arrays.class, "asList",

                                               MethodType.methodType(List.class, Object[].class),

                                               REF_invokeStatic);

         //MethodHandleNatives.resolve(asList_MN, null);

         asList_MN = lookup.resolveOrFail(asList_MN, REF_invokeStatic, null, NoSuchMethodException.class);

         System.out.println("about to call "+asList_MN);

         Object[] abc = { "a", "bc" };

         List<?> lst = (List<?>) MethodHandle.linkToStatic(abc, asList_MN);

         System.out.println("lst="+lst);

         MemberName toString_MN = new MemberName(Object.class.getMethod("toString"));

         String s1 = (String) MethodHandle.linkToVirtual(lst, toString_MN);

         toString_MN = new MemberName(Object.class.getMethod("toString"), true);

         String s2 = (String) MethodHandle.linkToSpecial(lst, toString_MN);

         System.out.println("[s1,s2,lst]="+Arrays.asList(s1, s2, lst.toString()));

         MemberName toArray_MN = new MemberName(List.class.getMethod("toArray"));

         Object[] arr = (Object[]) MethodHandle.linkToInterface(lst, toArray_MN);

         System.out.println("toArray="+Arrays.toString(arr));

     }

     static { try { testMethodHandleLinkers(); } catch (Throwable ex) { throw new RuntimeException(ex); } }

     // Requires these definitions in MethodHandle:

     static final native Object linkToStatic(Object x1, MemberName mn) throws Throwable;

     static final native Object linkToVirtual(Object x1, MemberName mn) throws Throwable;

     static final native Object linkToSpecial(Object x1, MemberName mn) throws Throwable;

     static final native Object linkToInterface(Object x1, MemberName mn) throws Throwable;

  */

     static { NamedFunction.initializeInvokers(); }

     // The following hack is necessary in order to suppress TRACE_INTERPRETER

     // during execution of the static initializes of this class.

     // Turning on TRACE_INTERPRETER too early will cause

     // stack overflows and other misbehavior during attempts to trace events

     // that occur during LambdaForm.<clinit>.

     // Therefore, do not move this line higher in this file, and do not remove.

     private static final boolean TRACE_INTERPRETER = MethodHandleStatics.TRACE_INTERPRETER;

 }