BoundMethodHandle.java 38.1 KB
Newer Older
1
/*
2
 * Copyright (c) 2008, 2012, Oracle and/or its affiliates. All rights reserved.
3 4 5 6
 * 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
7
 * published by the Free Software Foundation.  Oracle designates this
8
 * particular file as subject to the "Classpath" exception as provided
9
 * by Oracle in the LICENSE file that accompanied this code.
10 11 12 13 14 15 16 17 18 19 20
 *
 * 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.
 *
21 22 23
 * 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.
24 25
 */

26
package java.lang.invoke;
27

28 29 30
import static com.sun.xml.internal.ws.org.objectweb.asm.Opcodes.*;
import static java.lang.invoke.LambdaForm.basicTypes;
import static java.lang.invoke.MethodHandleNatives.Constants.REF_invokeStatic;
31
import static java.lang.invoke.MethodHandleStatics.*;
32

33 34 35 36 37 38 39 40 41 42 43 44 45 46
import java.lang.invoke.LambdaForm.Name;
import java.lang.invoke.LambdaForm.NamedFunction;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.HashMap;

import sun.invoke.util.ValueConversions;
import sun.invoke.util.Wrapper;

import com.sun.xml.internal.ws.org.objectweb.asm.ClassWriter;
import com.sun.xml.internal.ws.org.objectweb.asm.MethodVisitor;
import com.sun.xml.internal.ws.org.objectweb.asm.Type;

47 48 49 50
/**
 * The flavor of method handle which emulates an invoke instruction
 * on a predetermined argument.  The JVM dispatches to the correct method
 * when the handle is created, not when it is invoked.
51 52
 *
 * All bound arguments are encapsulated in dedicated species.
53
 */
54
/* non-public */ abstract class BoundMethodHandle extends MethodHandle {
55

56 57 58
    /* non-public */ BoundMethodHandle(MethodType type, LambdaForm form) {
        super(type, form);
    }
59

60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
    //
    // BMH API and internals
    //

    static MethodHandle bindSingle(MethodType type, LambdaForm form, char xtype, Object x) {
        // for some type signatures, there exist pre-defined concrete BMH classes
        try {
            switch (xtype) {
            case 'L':
                if (true)  return bindSingle(type, form, x);  // Use known fast path.
                return (BoundMethodHandle) SpeciesData.EMPTY.extendWithType('L').constructor[0].invokeBasic(type, form, x);
            case 'I':
                return (BoundMethodHandle) SpeciesData.EMPTY.extendWithType('I').constructor[0].invokeBasic(type, form, ValueConversions.widenSubword(x));
            case 'J':
                return (BoundMethodHandle) SpeciesData.EMPTY.extendWithType('J').constructor[0].invokeBasic(type, form, (long) x);
            case 'F':
                return (BoundMethodHandle) SpeciesData.EMPTY.extendWithType('F').constructor[0].invokeBasic(type, form, (float) x);
            case 'D':
                return (BoundMethodHandle) SpeciesData.EMPTY.extendWithType('D').constructor[0].invokeBasic(type, form, (double) x);
            default : throw new InternalError("unexpected xtype: " + xtype);
            }
        } catch (Throwable t) {
82
            throw newInternalError(t);
83
        }
84
    }
85

86 87
    static MethodHandle bindSingle(MethodType type, LambdaForm form, Object x) {
            return new Species_L(type, form, x);
88 89
    }

90 91 92 93 94 95 96 97 98 99
    MethodHandle cloneExtend(MethodType type, LambdaForm form, char xtype, Object x) {
        try {
            switch (xtype) {
            case 'L': return cloneExtendL(type, form, x);
            case 'I': return cloneExtendI(type, form, ValueConversions.widenSubword(x));
            case 'J': return cloneExtendJ(type, form, (long) x);
            case 'F': return cloneExtendF(type, form, (float) x);
            case 'D': return cloneExtendD(type, form, (double) x);
            }
        } catch (Throwable t) {
100
            throw newInternalError(t);
101
        }
102
        throw new InternalError("unexpected type: " + xtype);
103 104
    }

105 106 107 108 109
    @Override
    MethodHandle bindArgument(int pos, char basicType, Object value) {
        MethodType type = type().dropParameterTypes(pos, pos+1);
        LambdaForm form = internalForm().bind(1+pos, speciesData());
        return cloneExtend(type, form, basicType, value);
110 111
    }

112 113 114 115 116 117
    @Override
    MethodHandle dropArguments(MethodType srcType, int pos, int drops) {
        LambdaForm form = internalForm().addArguments(pos, srcType.parameterList().subList(pos, pos+drops));
        try {
             return clone(srcType, form);
         } catch (Throwable t) {
118
             throw newInternalError(t);
119 120 121 122 123 124 125 126
         }
    }

    @Override
    MethodHandle permuteArguments(MethodType newType, int[] reorder) {
        try {
             return clone(newType, form.permuteArguments(1, reorder, basicTypes(newType.parameterList())));
         } catch (Throwable t) {
127
             throw newInternalError(t);
128 129 130 131 132 133 134 135 136
         }
    }

    static final String EXTENSION_TYPES = "LIJFD";
    static final byte INDEX_L = 0, INDEX_I = 1, INDEX_J = 2, INDEX_F = 3, INDEX_D = 4;
    static byte extensionIndex(char type) {
        int i = EXTENSION_TYPES.indexOf(type);
        if (i < 0)  throw new InternalError();
        return (byte) i;
137 138
    }

139 140 141 142 143 144
    /**
     * Return the {@link SpeciesData} instance representing this BMH species. All subclasses must provide a
     * static field containing this value, and they must accordingly implement this method.
     */
    protected abstract SpeciesData speciesData();

145 146 147 148 149
    @Override
    final Object internalProperties() {
        return "/BMH="+internalValues();
    }

150
    @Override
151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168
    final Object internalValues() {
        Object[] boundValues = new Object[speciesData().fieldCount()];
        for (int i = 0; i < boundValues.length; ++i) {
            boundValues[i] = arg(i);
        }
        return Arrays.asList(boundValues);
    }

    public final Object arg(int i) {
        try {
            switch (speciesData().fieldType(i)) {
            case 'L': return argL(i);
            case 'I': return argI(i);
            case 'F': return argF(i);
            case 'D': return argD(i);
            case 'J': return argJ(i);
            }
        } catch (Throwable ex) {
169
            throw newInternalError(ex);
170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194
        }
        throw new InternalError("unexpected type: " + speciesData().types+"."+i);
    }
    public final Object argL(int i) throws Throwable { return          speciesData().getters[i].invokeBasic(this); }
    public final int    argI(int i) throws Throwable { return (int)    speciesData().getters[i].invokeBasic(this); }
    public final float  argF(int i) throws Throwable { return (float)  speciesData().getters[i].invokeBasic(this); }
    public final double argD(int i) throws Throwable { return (double) speciesData().getters[i].invokeBasic(this); }
    public final long   argJ(int i) throws Throwable { return (long)   speciesData().getters[i].invokeBasic(this); }

    //
    // cloning API
    //

    public abstract BoundMethodHandle clone(MethodType mt, LambdaForm lf) throws Throwable;
    public abstract BoundMethodHandle cloneExtendL(MethodType mt, LambdaForm lf, Object narg) throws Throwable;
    public abstract BoundMethodHandle cloneExtendI(MethodType mt, LambdaForm lf, int    narg) throws Throwable;
    public abstract BoundMethodHandle cloneExtendJ(MethodType mt, LambdaForm lf, long   narg) throws Throwable;
    public abstract BoundMethodHandle cloneExtendF(MethodType mt, LambdaForm lf, float  narg) throws Throwable;
    public abstract BoundMethodHandle cloneExtendD(MethodType mt, LambdaForm lf, double narg) throws Throwable;

    // The following is a grossly irregular hack:
    @Override MethodHandle reinvokerTarget() {
        try {
            return (MethodHandle) argL(0);
        } catch (Throwable ex) {
195
            throw newInternalError(ex);
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321
        }
    }

    //
    // concrete BMH classes required to close bootstrap loops
    //

    private  // make it private to force users to access the enclosing class first
    static final class Species_L extends BoundMethodHandle {
        final Object argL0;
        public Species_L(MethodType mt, LambdaForm lf, Object argL0) {
            super(mt, lf);
            this.argL0 = argL0;
        }
        // The following is a grossly irregular hack:
        @Override MethodHandle reinvokerTarget() { return (MethodHandle) argL0; }
        @Override
        public SpeciesData speciesData() {
            return SPECIES_DATA;
        }
        public static final SpeciesData SPECIES_DATA = SpeciesData.getForClass("L", Species_L.class);
        @Override
        public final BoundMethodHandle clone(MethodType mt, LambdaForm lf) throws Throwable {
            return new Species_L(mt, lf, argL0);
        }
        @Override
        public final BoundMethodHandle cloneExtendL(MethodType mt, LambdaForm lf, Object narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_L).constructor[0].invokeBasic(mt, lf, argL0, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendI(MethodType mt, LambdaForm lf, int narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_I).constructor[0].invokeBasic(mt, lf, argL0, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendJ(MethodType mt, LambdaForm lf, long narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_J).constructor[0].invokeBasic(mt, lf, argL0, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendF(MethodType mt, LambdaForm lf, float narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_F).constructor[0].invokeBasic(mt, lf, argL0, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendD(MethodType mt, LambdaForm lf, double narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_D).constructor[0].invokeBasic(mt, lf, argL0, narg);
        }
    }

/*
    static final class Species_LL extends BoundMethodHandle {
        final Object argL0;
        final Object argL1;
        public Species_LL(MethodType mt, LambdaForm lf, Object argL0, Object argL1) {
            super(mt, lf);
            this.argL0 = argL0;
            this.argL1 = argL1;
        }
        @Override
        public SpeciesData speciesData() {
            return SPECIES_DATA;
        }
        public static final SpeciesData SPECIES_DATA = SpeciesData.getForClass("LL", Species_LL.class);
        @Override
        public final BoundMethodHandle clone(MethodType mt, LambdaForm lf) throws Throwable {
            return new Species_LL(mt, lf, argL0, argL1);
        }
        @Override
        public final BoundMethodHandle cloneExtendL(MethodType mt, LambdaForm lf, Object narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_L).constructor[0].invokeBasic(mt, lf, argL0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendI(MethodType mt, LambdaForm lf, int narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_I).constructor[0].invokeBasic(mt, lf, argL0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendJ(MethodType mt, LambdaForm lf, long narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_J).constructor[0].invokeBasic(mt, lf, argL0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendF(MethodType mt, LambdaForm lf, float narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_F).constructor[0].invokeBasic(mt, lf, argL0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendD(MethodType mt, LambdaForm lf, double narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_D).constructor[0].invokeBasic(mt, lf, argL0, argL1, narg);
        }
    }

    static final class Species_JL extends BoundMethodHandle {
        final long argJ0;
        final Object argL1;
        public Species_JL(MethodType mt, LambdaForm lf, long argJ0, Object argL1) {
            super(mt, lf);
            this.argJ0 = argJ0;
            this.argL1 = argL1;
        }
        @Override
        public SpeciesData speciesData() {
            return SPECIES_DATA;
        }
        public static final SpeciesData SPECIES_DATA = SpeciesData.getForClass("JL", Species_JL.class);
        @Override public final long   argJ0() { return argJ0; }
        @Override public final Object argL1() { return argL1; }
        @Override
        public final BoundMethodHandle clone(MethodType mt, LambdaForm lf) throws Throwable {
            return new Species_JL(mt, lf, argJ0, argL1);
        }
        @Override
        public final BoundMethodHandle cloneExtendL(MethodType mt, LambdaForm lf, Object narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_L).constructor[0].invokeBasic(mt, lf, argJ0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendI(MethodType mt, LambdaForm lf, int narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_I).constructor[0].invokeBasic(mt, lf, argJ0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendJ(MethodType mt, LambdaForm lf, long narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_J).constructor[0].invokeBasic(mt, lf, argJ0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendF(MethodType mt, LambdaForm lf, float narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_F).constructor[0].invokeBasic(mt, lf, argJ0, argL1, narg);
        }
        @Override
        public final BoundMethodHandle cloneExtendD(MethodType mt, LambdaForm lf, double narg) throws Throwable {
            return (BoundMethodHandle) SPECIES_DATA.extendWithIndex(INDEX_D).constructor[0].invokeBasic(mt, lf, argJ0, argL1, narg);
        }
322
    }
323
*/
324

325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370
    //
    // BMH species meta-data
    //

    /**
     * Meta-data wrapper for concrete BMH classes.
     */
    static class SpeciesData {
        final String                             types;
        final Class<? extends BoundMethodHandle> clazz;
        // Bootstrapping requires circular relations MH -> BMH -> SpeciesData -> MH
        // Therefore, we need a non-final link in the chain.  Use array elements.
        final MethodHandle[]                     constructor;
        final MethodHandle[]                     getters;
        final SpeciesData[]                      extensions;

        public int fieldCount() {
            return types.length();
        }
        public char fieldType(int i) {
            return types.charAt(i);
        }

        public String toString() {
            return "SpeciesData["+(isPlaceholder() ? "<placeholder>" : clazz.getSimpleName())+":"+types+"]";
        }

        /**
         * Return a {@link LambdaForm.Name} containing a {@link LambdaForm.NamedFunction} that
         * represents a MH bound to a generic invoker, which in turn forwards to the corresponding
         * getter.
         */
        Name getterName(Name mhName, int i) {
            MethodHandle mh = getters[i];
            assert(mh != null) : this+"."+i;
            return new Name(mh, mhName);
        }

        static final SpeciesData EMPTY = new SpeciesData("", BoundMethodHandle.class);

        private SpeciesData(String types, Class<? extends BoundMethodHandle> clazz) {
            this.types = types;
            this.clazz = clazz;
            if (!INIT_DONE) {
                this.constructor = new MethodHandle[1];
                this.getters = new MethodHandle[types.length()];
371
            } else {
372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421
                this.constructor = Factory.makeCtors(clazz, types, null);
                this.getters = Factory.makeGetters(clazz, types, null);
            }
            this.extensions = new SpeciesData[EXTENSION_TYPES.length()];
        }

        private void initForBootstrap() {
            assert(!INIT_DONE);
            if (constructor[0] == null) {
                Factory.makeCtors(clazz, types, this.constructor);
                Factory.makeGetters(clazz, types, this.getters);
            }
        }

        private SpeciesData(String types) {
            // Placeholder only.
            this.types = types;
            this.clazz = null;
            this.constructor = null;
            this.getters = null;
            this.extensions = null;
        }
        private boolean isPlaceholder() { return clazz == null; }

        private static final HashMap<String, SpeciesData> CACHE = new HashMap<>();
        private static final boolean INIT_DONE;  // set after <clinit> finishes...

        SpeciesData extendWithType(char type) {
            int i = extensionIndex(type);
            SpeciesData d = extensions[i];
            if (d != null)  return d;
            extensions[i] = d = get(types+type);
            return d;
        }

        SpeciesData extendWithIndex(byte index) {
            SpeciesData d = extensions[index];
            if (d != null)  return d;
            extensions[index] = d = get(types+EXTENSION_TYPES.charAt(index));
            return d;
        }

        private static SpeciesData get(String types) {
            // Acquire cache lock for query.
            SpeciesData d = lookupCache(types);
            if (!d.isPlaceholder())
                return d;
            synchronized (d) {
                // Use synch. on the placeholder to prevent multiple instantiation of one species.
                // Creating this class forces a recursive call to getForClass.
422 423
                if (lookupCache(types).isPlaceholder())
                    Factory.generateConcreteBMHClass(types);
424
            }
425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441
            // Reacquire cache lock.
            d = lookupCache(types);
            // Class loading must have upgraded the cache.
            assert(d != null && !d.isPlaceholder());
            return d;
        }
        static SpeciesData getForClass(String types, Class<? extends BoundMethodHandle> clazz) {
            // clazz is a new class which is initializing its SPECIES_DATA field
            return updateCache(types, new SpeciesData(types, clazz));
        }
        private static synchronized SpeciesData lookupCache(String types) {
            SpeciesData d = CACHE.get(types);
            if (d != null)  return d;
            d = new SpeciesData(types);
            assert(d.isPlaceholder());
            CACHE.put(types, d);
            return d;
442
        }
443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466
        private static synchronized SpeciesData updateCache(String types, SpeciesData d) {
            SpeciesData d2;
            assert((d2 = CACHE.get(types)) == null || d2.isPlaceholder());
            assert(!d.isPlaceholder());
            CACHE.put(types, d);
            return d;
        }

        static {
            // pre-fill the BMH speciesdata cache with BMH's inner classes
            final Class<BoundMethodHandle> rootCls = BoundMethodHandle.class;
            SpeciesData d0 = BoundMethodHandle.SPECIES_DATA;  // trigger class init
            assert(d0 == null || d0 == lookupCache("")) : d0;
            try {
                for (Class<?> c : rootCls.getDeclaredClasses()) {
                    if (rootCls.isAssignableFrom(c)) {
                        final Class<? extends BoundMethodHandle> cbmh = c.asSubclass(BoundMethodHandle.class);
                        SpeciesData d = Factory.speciesDataFromConcreteBMHClass(cbmh);
                        assert(d != null) : cbmh.getName();
                        assert(d.clazz == cbmh);
                        assert(d == lookupCache(d.types));
                    }
                }
            } catch (Throwable e) {
467
                throw newInternalError(e);
468 469 470 471 472 473 474 475 476 477 478 479 480
            }

            for (SpeciesData d : CACHE.values()) {
                d.initForBootstrap();
            }
            // Note:  Do not simplify this, because INIT_DONE must not be
            // a compile-time constant during bootstrapping.
            INIT_DONE = Boolean.TRUE;
        }
    }

    static SpeciesData getSpeciesData(String types) {
        return SpeciesData.get(types);
481 482
    }

483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750
    /**
     * Generation of concrete BMH classes.
     *
     * A concrete BMH species is fit for binding a number of values adhering to a
     * given type pattern. Reference types are erased.
     *
     * BMH species are cached by type pattern.
     *
     * A BMH species has a number of fields with the concrete (possibly erased) types of
     * bound values. Setters are provided as an API in BMH. Getters are exposed as MHs,
     * which can be included as names in lambda forms.
     */
    static class Factory {

        static final String JLO_SIG  = "Ljava/lang/Object;";
        static final String JLS_SIG  = "Ljava/lang/String;";
        static final String JLC_SIG  = "Ljava/lang/Class;";
        static final String MH       = "java/lang/invoke/MethodHandle";
        static final String MH_SIG   = "L"+MH+";";
        static final String BMH      = "java/lang/invoke/BoundMethodHandle";
        static final String BMH_SIG  = "L"+BMH+";";
        static final String SPECIES_DATA     = "java/lang/invoke/BoundMethodHandle$SpeciesData";
        static final String SPECIES_DATA_SIG = "L"+SPECIES_DATA+";";

        static final String SPECIES_PREFIX_NAME = "Species_";
        static final String SPECIES_PREFIX_PATH = BMH + "$" + SPECIES_PREFIX_NAME;

        static final String BMHSPECIES_DATA_EWI_SIG = "(B)" + SPECIES_DATA_SIG;
        static final String BMHSPECIES_DATA_GFC_SIG = "(" + JLS_SIG + JLC_SIG + ")" + SPECIES_DATA_SIG;
        static final String MYSPECIES_DATA_SIG = "()" + SPECIES_DATA_SIG;
        static final String VOID_SIG   = "()V";

        static final String SIG_INCIPIT = "(Ljava/lang/invoke/MethodType;Ljava/lang/invoke/LambdaForm;";

        static final Class<?>[] TYPES = new Class<?>[] { Object.class, int.class, long.class, float.class, double.class };

        static final String[] E_THROWABLE = new String[] { "java/lang/Throwable" };

        /**
         * Generate a concrete subclass of BMH for a given combination of bound types.
         *
         * A concrete BMH species adheres to the following schema:
         *
         * <pre>
         * class Species_<<types>> extends BoundMethodHandle {
         *     <<fields>>
         *     final SpeciesData speciesData() { return SpeciesData.get("<<types>>"); }
         * }
         * </pre>
         *
         * The {@code <<types>>} signature is precisely the string that is passed to this
         * method.
         *
         * The {@code <<fields>>} section consists of one field definition per character in
         * the type signature, adhering to the naming schema described in the definition of
         * {@link #makeFieldName()}.
         *
         * For example, a concrete BMH species for two reference and one integral bound values
         * would have the following shape:
         *
         * <pre>
         * class BoundMethodHandle { ... private static
         * final class Species_LLI extends BoundMethodHandle {
         *     final Object argL0;
         *     final Object argL1;
         *     final int argI2;
         *     public Species_LLI(MethodType mt, LambdaForm lf, Object argL0, Object argL1, int argI2) {
         *         super(mt, lf);
         *         this.argL0 = argL0;
         *         this.argL1 = argL1;
         *         this.argI2 = argI2;
         *     }
         *     public final SpeciesData speciesData() { return SPECIES_DATA; }
         *     public static final SpeciesData SPECIES_DATA = SpeciesData.getForClass("LLI", Species_LLI.class);
         *     public final BoundMethodHandle clone(MethodType mt, LambdaForm lf) {
         *         return SPECIES_DATA.constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2);
         *     }
         *     public final BoundMethodHandle cloneExtendL(MethodType mt, LambdaForm lf, Object narg) {
         *         return SPECIES_DATA.extendWithIndex(INDEX_L).constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2, narg);
         *     }
         *     public final BoundMethodHandle cloneExtendI(MethodType mt, LambdaForm lf, int narg) {
         *         return SPECIES_DATA.extendWithIndex(INDEX_I).constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2, narg);
         *     }
         *     public final BoundMethodHandle cloneExtendJ(MethodType mt, LambdaForm lf, long narg) {
         *         return SPECIES_DATA.extendWithIndex(INDEX_J).constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2, narg);
         *     }
         *     public final BoundMethodHandle cloneExtendF(MethodType mt, LambdaForm lf, float narg) {
         *         return SPECIES_DATA.extendWithIndex(INDEX_F).constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2, narg);
         *     }
         *     public final BoundMethodHandle cloneExtendD(MethodType mt, LambdaForm lf, double narg) {
         *         return SPECIES_DATA.extendWithIndex(INDEX_D).constructor[0].invokeBasic(mt, lf, argL0, argL1, argI2, narg);
         *     }
         * }
         * </pre>
         *
         * @param types the type signature, wherein reference types are erased to 'L'
         * @return the generated concrete BMH class
         */
        static Class<? extends BoundMethodHandle> generateConcreteBMHClass(String types) {
            final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);

            final String className  = SPECIES_PREFIX_PATH + types;
            final String sourceFile = SPECIES_PREFIX_NAME + types;
            cw.visit(V1_6, ACC_PUBLIC + ACC_FINAL + ACC_SUPER, className, null, BMH, null);
            cw.visitSource(sourceFile, null);

            // emit static types and SPECIES_DATA fields
            cw.visitField(ACC_PUBLIC + ACC_STATIC, "SPECIES_DATA", SPECIES_DATA_SIG, null, null).visitEnd();

            // emit bound argument fields
            for (int i = 0; i < types.length(); ++i) {
                final char t = types.charAt(i);
                final String fieldName = makeFieldName(types, i);
                final String fieldDesc = t == 'L' ? JLO_SIG : String.valueOf(t);
                cw.visitField(ACC_FINAL, fieldName, fieldDesc, null, null).visitEnd();
            }

            MethodVisitor mv;

            // emit constructor
            mv = cw.visitMethod(ACC_PUBLIC, "<init>", makeSignature(types, true), null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitVarInsn(ALOAD, 2);

            mv.visitMethodInsn(INVOKESPECIAL, BMH, "<init>", makeSignature("", true));

            for (int i = 0, j = 0; i < types.length(); ++i, ++j) {
                // i counts the arguments, j counts corresponding argument slots
                char t = types.charAt(i);
                mv.visitVarInsn(ALOAD, 0);
                mv.visitVarInsn(typeLoadOp(t), j + 3); // parameters start at 3
                mv.visitFieldInsn(PUTFIELD, className, makeFieldName(types, i), typeSig(t));
                if (t == 'J' || t == 'D') {
                    ++j; // adjust argument register access
                }
            }

            mv.visitInsn(RETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();

            // emit implementation of reinvokerTarget()
            mv = cw.visitMethod(ACC_PUBLIC + ACC_FINAL, "reinvokerTarget", "()" + MH_SIG, null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitFieldInsn(GETFIELD, className, "argL0", JLO_SIG);
            mv.visitTypeInsn(CHECKCAST, MH);
            mv.visitInsn(ARETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();

            // emit implementation of speciesData()
            mv = cw.visitMethod(ACC_PUBLIC + ACC_FINAL, "speciesData", MYSPECIES_DATA_SIG, null, null);
            mv.visitCode();
            mv.visitFieldInsn(GETSTATIC, className, "SPECIES_DATA", SPECIES_DATA_SIG);
            mv.visitInsn(ARETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();

            // emit clone()
            mv = cw.visitMethod(ACC_PUBLIC + ACC_FINAL, "clone", makeSignature("", false), null, E_THROWABLE);
            mv.visitCode();
            // return speciesData().constructor[0].invokeBasic(mt, lf, argL0, ...)
            // obtain constructor
            mv.visitVarInsn(ALOAD, 0);
            mv.visitFieldInsn(GETSTATIC, className, "SPECIES_DATA", SPECIES_DATA_SIG);
            mv.visitFieldInsn(GETFIELD, SPECIES_DATA, "constructor", "[" + MH_SIG);
            mv.visitInsn(ICONST_0);
            mv.visitInsn(AALOAD);
            // load mt, lf
            mv.visitVarInsn(ALOAD, 1);
            mv.visitVarInsn(ALOAD, 2);
            // put fields on the stack
            emitPushFields(types, className, mv);
            // finally, invoke the constructor and return
            mv.visitMethodInsn(INVOKEVIRTUAL, MH, "invokeBasic", makeSignature(types, false));
            mv.visitInsn(ARETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();

            // for each type, emit cloneExtendT()
            for (Class<?> c : TYPES) {
                char t = Wrapper.basicTypeChar(c);
                mv = cw.visitMethod(ACC_PUBLIC + ACC_FINAL, "cloneExtend" + t, makeSignature(String.valueOf(t), false), null, E_THROWABLE);
                mv.visitCode();
                // return SPECIES_DATA.extendWithIndex(extensionIndex(t)).constructor[0].invokeBasic(mt, lf, argL0, ..., narg)
                // obtain constructor
                mv.visitFieldInsn(GETSTATIC, className, "SPECIES_DATA", SPECIES_DATA_SIG);
                int iconstInsn = ICONST_0 + extensionIndex(t);
                assert(iconstInsn <= ICONST_5);
                mv.visitInsn(iconstInsn);
                mv.visitMethodInsn(INVOKEVIRTUAL, SPECIES_DATA, "extendWithIndex", BMHSPECIES_DATA_EWI_SIG);
                mv.visitFieldInsn(GETFIELD, SPECIES_DATA, "constructor", "[" + MH_SIG);
                mv.visitInsn(ICONST_0);
                mv.visitInsn(AALOAD);
                // load mt, lf
                mv.visitVarInsn(ALOAD, 1);
                mv.visitVarInsn(ALOAD, 2);
                // put fields on the stack
                emitPushFields(types, className, mv);
                // put narg on stack
                mv.visitVarInsn(typeLoadOp(t), 3);
                // finally, invoke the constructor and return
                mv.visitMethodInsn(INVOKEVIRTUAL, MH, "invokeBasic", makeSignature(types + t, false));
                mv.visitInsn(ARETURN);
                mv.visitMaxs(0, 0);
                mv.visitEnd();
            }

            // emit class initializer
            mv = cw.visitMethod(ACC_PUBLIC | ACC_STATIC, "<clinit>", VOID_SIG, null, null);
            mv.visitCode();
            mv.visitLdcInsn(types);
            mv.visitLdcInsn(Type.getObjectType(className));
            mv.visitMethodInsn(INVOKESTATIC, SPECIES_DATA, "getForClass", BMHSPECIES_DATA_GFC_SIG);
            mv.visitFieldInsn(PUTSTATIC, className, "SPECIES_DATA", SPECIES_DATA_SIG);
            mv.visitInsn(RETURN);
            mv.visitMaxs(0, 0);
            mv.visitEnd();

            cw.visitEnd();

            // load class
            final byte[] classFile = cw.toByteArray();
            InvokerBytecodeGenerator.maybeDump(className, classFile);
            Class<? extends BoundMethodHandle> bmhClass =
                //UNSAFE.defineAnonymousClass(BoundMethodHandle.class, classFile, null).asSubclass(BoundMethodHandle.class);
                UNSAFE.defineClass(className, classFile, 0, classFile.length).asSubclass(BoundMethodHandle.class);
            UNSAFE.ensureClassInitialized(bmhClass);

            return bmhClass;
        }

        private static int typeLoadOp(char t) {
            switch (t) {
            case 'L': return ALOAD;
            case 'I': return ILOAD;
            case 'J': return LLOAD;
            case 'F': return FLOAD;
            case 'D': return DLOAD;
            default : throw new InternalError("unrecognized type " + t);
            }
        }

        private static void emitPushFields(String types, String className, MethodVisitor mv) {
            for (int i = 0; i < types.length(); ++i) {
                char tc = types.charAt(i);
                mv.visitVarInsn(ALOAD, 0);
                mv.visitFieldInsn(GETFIELD, className, makeFieldName(types, i), typeSig(tc));
            }
        }

        static String typeSig(char t) {
            return t == 'L' ? JLO_SIG : String.valueOf(t);
        }

        //
        // Getter MH generation.
        //

        private static MethodHandle makeGetter(Class<?> cbmhClass, String types, int index) {
            String fieldName = makeFieldName(types, index);
            Class<?> fieldType = Wrapper.forBasicType(types.charAt(index)).primitiveType();
            try {
                return LOOKUP.findGetter(cbmhClass, fieldName, fieldType);
            } catch (NoSuchFieldException | IllegalAccessException e) {
751
                throw newInternalError(e);
752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778
            }
        }

        static MethodHandle[] makeGetters(Class<?> cbmhClass, String types, MethodHandle[] mhs) {
            if (mhs == null)  mhs = new MethodHandle[types.length()];
            for (int i = 0; i < mhs.length; ++i) {
                mhs[i] = makeGetter(cbmhClass, types, i);
                assert(mhs[i].internalMemberName().getDeclaringClass() == cbmhClass);
            }
            return mhs;
        }

        static MethodHandle[] makeCtors(Class<? extends BoundMethodHandle> cbmh, String types, MethodHandle mhs[]) {
            if (mhs == null)  mhs = new MethodHandle[1];
            mhs[0] = makeCbmhCtor(cbmh, types);
            return mhs;
        }

        //
        // Auxiliary methods.
        //

        static SpeciesData speciesDataFromConcreteBMHClass(Class<? extends BoundMethodHandle> cbmh) {
            try {
                Field F_SPECIES_DATA = cbmh.getDeclaredField("SPECIES_DATA");
                return (SpeciesData) F_SPECIES_DATA.get(null);
            } catch (ReflectiveOperationException ex) {
779
                throw newInternalError(ex);
780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804
            }
        }

        /**
         * Field names in concrete BMHs adhere to this pattern:
         * arg + type + index
         * where type is a single character (L, I, J, F, D).
         */
        private static String makeFieldName(String types, int index) {
            assert index >= 0 && index < types.length();
            return "arg" + types.charAt(index) + index;
        }

        private static String makeSignature(String types, boolean ctor) {
            StringBuilder buf = new StringBuilder(SIG_INCIPIT);
            for (char c : types.toCharArray()) {
                buf.append(typeSig(c));
            }
            return buf.append(')').append(ctor ? "V" : BMH_SIG).toString();
        }

        static MethodHandle makeCbmhCtor(Class<? extends BoundMethodHandle> cbmh, String types) {
            try {
                return linkConstructor(LOOKUP.findConstructor(cbmh, MethodType.fromMethodDescriptorString(makeSignature(types, true), null)));
            } catch (NoSuchMethodException | IllegalAccessException | IllegalArgumentException | TypeNotPresentException e) {
805
                throw newInternalError(e);
806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835
            }
        }

        /**
         * Wrap a constructor call in a {@link LambdaForm}.
         *
         * If constructors ({@code <init>} methods) are called in LFs, problems might arise if the LFs
         * are turned into bytecode, because the call to the allocator is routed through an MH, and the
         * verifier cannot find a {@code NEW} instruction preceding the {@code INVOKESPECIAL} to
         * {@code <init>}. To avoid this, we add an indirection by invoking {@code <init>} through
         * {@link MethodHandle#linkToSpecial}.
         *
         * The last {@link LambdaForm#Name Name} in the argument's form is expected to be the {@code void}
         * result of the {@code <init>} invocation. This entry is replaced.
         */
        private static MethodHandle linkConstructor(MethodHandle cmh) {
            final LambdaForm lf = cmh.form;
            final int initNameIndex = lf.names.length - 1;
            final Name initName = lf.names[initNameIndex];
            final MemberName ctorMN = initName.function.member;
            final MethodType ctorMT = ctorMN.getInvocationType();

            // obtain function member (call target)
            // linker method type replaces initial parameter (BMH species) with BMH to avoid naming a species (anonymous class!)
            final MethodType linkerMT = ctorMT.changeParameterType(0, BoundMethodHandle.class).appendParameterTypes(MemberName.class);
            MemberName linkerMN = new MemberName(MethodHandle.class, "linkToSpecial", linkerMT, REF_invokeStatic);
            try {
                linkerMN = MemberName.getFactory().resolveOrFail(REF_invokeStatic, linkerMN, null, NoSuchMethodException.class);
                assert(linkerMN.isStatic());
            } catch (ReflectiveOperationException ex) {
836
                throw newInternalError(ex);
837 838 839 840 841 842 843 844 845 846 847 848
            }
            // extend arguments array
            Object[] newArgs = Arrays.copyOf(initName.arguments, initName.arguments.length + 1);
            newArgs[newArgs.length - 1] = ctorMN;
            // replace function
            final NamedFunction nf = new NamedFunction(linkerMN);
            final Name linkedCtor = new Name(nf, newArgs);
            linkedCtor.initIndex(initNameIndex);
            lf.names[initNameIndex] = linkedCtor;
            return cmh;
        }

849
    }
850 851 852 853 854 855 856

    private static final Lookup LOOKUP = Lookup.IMPL_LOOKUP;

    /**
     * All subclasses must provide such a value describing their type signature.
     */
    static final SpeciesData SPECIES_DATA = SpeciesData.EMPTY;
857
}