alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (LambdaForm.java)

This example Java source code file (LambdaForm.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, class, compile_threshold, hidden, lambdaform, membername, methodhandle, methodtype, name, namedfunction, object, reflection, string, threading, threads, throwable, trace_interpreter, util

The LambdaForm.java Java example source code

/*
 * 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>
{@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>
 * 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>
{@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>
 * <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
        }
        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);
        //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
            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;
}

Other Java examples (source code examples)

Here is a short list of links related to this Java LambdaForm.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.