1 /*
   2  * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * 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  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.lang.invoke;
  27 
  28 import jdk.internal.loader.BootLoader;
  29 import jdk.internal.org.objectweb.asm.ClassWriter;
  30 import jdk.internal.org.objectweb.asm.FieldVisitor;
  31 import jdk.internal.org.objectweb.asm.MethodVisitor;
  32 import jdk.internal.vm.annotation.Stable;
  33 import sun.invoke.util.BytecodeName;
  34 
  35 import java.lang.reflect.*;
  36 import java.security.AccessController;
  37 import java.security.PrivilegedAction;
  38 import java.security.ProtectionDomain;
  39 import java.util.*;
  40 import java.util.concurrent.ConcurrentHashMap;
  41 
  42 import static java.lang.invoke.LambdaForm.*;
  43 import static java.lang.invoke.MethodHandleNatives.Constants.REF_getStatic;
  44 import static java.lang.invoke.MethodHandleNatives.Constants.REF_putStatic;
  45 import static java.lang.invoke.MethodHandleStatics.*;
  46 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
  47 import static jdk.internal.org.objectweb.asm.Opcodes.*;
  48 
  49 /**
  50  * Class specialization code.
  51  * @param <T> top class under which species classes are created.
  52  * @param <K> key which identifies individual specializations.
  53  * @param <S> species data type.
  54  */
  55 /*non-public*/
  56 abstract class ClassSpecializer<T,K,S extends ClassSpecializer<T,K,S>.SpeciesData> {
  57     private final Class<T> topClass;
  58     private final Class<K> keyType;
  59     private final Class<S> metaType;
  60     private final MemberName sdAccessor;
  61     private final String sdFieldName;
  62     private final List<MemberName> transformMethods;
  63     private final MethodType baseConstructorType;
  64     private final S topSpecies;
  65     private final ConcurrentHashMap<K, Object> cache = new ConcurrentHashMap<>();
  66     private final Factory factory;
  67     private @Stable boolean topClassIsSuper;
  68 
  69     /** Return the top type mirror, for type {@code T} */
  70     public final Class<T> topClass() { return topClass; }
  71 
  72     /** Return the key type mirror, for type {@code K} */
  73     public final Class<K> keyType() { return keyType; }
  74 
  75     /** Return the species metadata type mirror, for type {@code S} */
  76     public final Class<S> metaType() { return metaType; }
  77 
  78     /** Report the leading arguments (if any) required by every species factory.
  79      * Every species factory adds its own field types as additional arguments,
  80      * but these arguments always come first, in every factory method.
  81      */
  82     protected MethodType baseConstructorType() { return baseConstructorType; }
  83 
  84     /** Return the trivial species for the null sequence of arguments. */
  85     protected final S topSpecies() { return topSpecies; }
  86 
  87     /** Return the list of transform methods originally given at creation of this specializer. */
  88     protected final List<MemberName> transformMethods() { return transformMethods; }
  89 
  90     /** Return the factory object used to build and load concrete species code. */
  91     protected final Factory factory() { return factory; }
  92 
  93     /**
  94      * Constructor for this class specializer.
  95      * @param topClass type mirror for T
  96      * @param keyType type mirror for K
  97      * @param metaType type mirror for S
  98      * @param baseConstructorType principal constructor type
  99      * @param sdAccessor the method used to get the speciesData
 100      * @param sdFieldName the name of the species data field, inject the speciesData object
 101      * @param transformMethods optional list of transformMethods
 102      */
 103     protected ClassSpecializer(Class<T> topClass,
 104                                Class<K> keyType,
 105                                Class<S> metaType,
 106                                MethodType baseConstructorType,
 107                                MemberName sdAccessor,
 108                                String sdFieldName,
 109                                List<MemberName> transformMethods) {
 110         this.topClass = topClass;
 111         this.keyType = keyType;
 112         this.metaType = metaType;
 113         this.sdAccessor = sdAccessor;
 114         this.transformMethods = List.copyOf(transformMethods);
 115         this.sdFieldName = sdFieldName;
 116         this.baseConstructorType = baseConstructorType.changeReturnType(void.class);
 117         this.factory = makeFactory();
 118         K tsk = topSpeciesKey();
 119         S topSpecies = null;
 120         if (tsk != null && topSpecies == null) {
 121             // if there is a key, build the top species if needed:
 122             topSpecies = findSpecies(tsk);
 123         }
 124         this.topSpecies = topSpecies;
 125     }
 126 
 127     // Utilities for subclass constructors:
 128     protected static <T> Constructor<T> reflectConstructor(Class<T> defc, Class<?>... ptypes) {
 129         try {
 130             return defc.getDeclaredConstructor(ptypes);
 131         } catch (NoSuchMethodException ex) {
 132             throw newIAE(defc.getName()+"("+MethodType.methodType(void.class, ptypes)+")", ex);
 133         }
 134     }
 135 
 136     protected static Field reflectField(Class<?> defc, String name) {
 137         try {
 138             return defc.getDeclaredField(name);
 139         } catch (NoSuchFieldException ex) {
 140             throw newIAE(defc.getName()+"."+name, ex);
 141         }
 142     }
 143 
 144     private static RuntimeException newIAE(String message, Throwable cause) {
 145         return new IllegalArgumentException(message, cause);
 146     }
 147 
 148     @SuppressWarnings("unchecked")
 149     public final S findSpecies(K key) {
 150         // Note:  Species instantiation may throw VirtualMachineError because of
 151         // code cache overflow.  If this happens the species bytecode may be
 152         // loaded but not linked to its species metadata (with MH's etc).
 153         // That will cause a throw out of this method with a reservation object
 154         // installed in the cache.
 155         //
 156         // In a latter attempt to get the same species, the already-loaded
 157         // class will be present in the system dictionary, causing an
 158         // error when the species generator tries to reload it.
 159         // We try to detect this case and link the pre-existing code.
 160         //
 161         // Although it would be better to start fresh by loading a new
 162         // copy, we have to salvage the previously loaded but broken code.
 163         // (As an alternative, we might spin a new class with a new name,
 164         // or use the anonymous class mechanism.)
 165         //
 166         // In the end, as long as everybody goes through this method,
 167         // its initialization logic will ensure only one SpeciesData will be set
 168         // successfully on a concrete class if ever.
 169         // The concrete class is published via SpeciesData instance
 170         // returned here only after the class and species data are linked together.
 171         Object reservation = new Object();
 172         S speciesData;
 173         Object speciesDataOrReservation = cache.putIfAbsent(key, reservation);
 174         if (speciesDataOrReservation instanceof ClassSpecializer<?, ?, ?>.SpeciesData) {
 175             // already cached
 176             speciesData = (S) speciesDataOrReservation;
 177         } else {
 178             // resolve the race for reservation
 179             if (speciesDataOrReservation != null) {
 180                 reservation = speciesDataOrReservation;
 181             }
 182             synchronized (reservation) {
 183                 // re-check under lock
 184                 speciesDataOrReservation = cache.get(key);
 185                 if (speciesDataOrReservation == reservation) {
 186                     // the thread that enters synchronized (reservation) and finds
 187                     // reservation still in cache, tries to (re)initialize species data.
 188                     // if the initialization fails, the reservation object is left in CHM
 189                     // for next thread to pick it up and retry...
 190                     speciesData = factory.loadSpecies(newSpeciesData(key));
 191                     if (!cache.replace(key, reservation, speciesData)) {
 192                         throw new AssertionError("Thought this was unreachable");
 193                     }
 194                 } else {
 195                     // the thread that enters synchronized (reservation) and finds
 196                     // a reference that is not a reservation, has found the initialized
 197                     // species data...
 198                     assert speciesDataOrReservation instanceof ClassSpecializer<?, ?, ?>.SpeciesData;
 199                     speciesData = (S) speciesDataOrReservation;
 200                 }
 201             }
 202         }
 203         assert(speciesData != null && speciesData.isResolved());
 204         return speciesData;
 205     }
 206 
 207     /**
 208      * Meta-data wrapper for concrete subtypes of the top class.
 209      * Each concrete subtype corresponds to a given sequence of basic field types (LIJFD).
 210      * The fields are immutable; their values are fully specified at object construction.
 211      * Each species supplies an array of getter functions which may be used in lambda forms.
 212      * A concrete value is always constructed from the full tuple of its field values,
 213      * accompanied by the required constructor parameters.
 214      * There *may* also be transforms which cloning a species instance and
 215      * either replace a constructor parameter or add one or more new field values.
 216      * The shortest possible species has zero fields.
 217      * Subtypes are not interrelated among themselves by subtyping, even though
 218      * it would appear that a shorter species could serve as a supertype of a
 219      * longer one which extends it.
 220      */
 221     public abstract class SpeciesData {
 222         // Bootstrapping requires circular relations Class -> SpeciesData -> Class
 223         // Therefore, we need non-final links in the chain.  Use @Stable fields.
 224         private final K key;
 225         private final List<Class<?>> fieldTypes;
 226         @Stable private Class<? extends T> speciesCode;
 227         @Stable private List<MethodHandle> factories;
 228         @Stable private List<MethodHandle> getters;
 229         @Stable private List<LambdaForm.NamedFunction> nominalGetters;
 230         @Stable private final MethodHandle[] transformHelpers = new MethodHandle[transformMethods.size()];
 231 
 232         protected SpeciesData(K key) {
 233             this.key = keyType.cast(Objects.requireNonNull(key));
 234             List<Class<?>> types = deriveFieldTypes(key);
 235             this.fieldTypes = List.copyOf(types);
 236         }
 237 
 238         public final K key() {
 239             return key;
 240         }
 241 
 242         protected final List<Class<?>> fieldTypes() {
 243             return fieldTypes;
 244         }
 245 
 246         protected final int fieldCount() {
 247             return fieldTypes.size();
 248         }
 249 
 250         protected ClassSpecializer<T,K,S> outer() {
 251             return ClassSpecializer.this;
 252         }
 253 
 254         protected final boolean isResolved() {
 255             return speciesCode != null && factories != null && !factories.isEmpty();
 256         }
 257 
 258         @Override public String toString() {
 259             return metaType.getSimpleName() + "[" + key.toString() + " => " + (isResolved() ? speciesCode.getSimpleName() : "UNRESOLVED") + "]";
 260         }
 261 
 262         @Override
 263         public int hashCode() {
 264             return key.hashCode();
 265         }
 266 
 267         @Override
 268         public boolean equals(Object obj) {
 269             if (!(obj instanceof ClassSpecializer.SpeciesData)) {
 270                 return false;
 271             }
 272             @SuppressWarnings("rawtypes")
 273             ClassSpecializer.SpeciesData that = (ClassSpecializer.SpeciesData) obj;
 274             return this.outer() == that.outer() && this.key.equals(that.key);
 275         }
 276 
 277         /** Throws NPE if this species is not yet resolved. */
 278         protected final Class<? extends T> speciesCode() {
 279             return Objects.requireNonNull(speciesCode);
 280         }
 281 
 282         /**
 283          * Return a {@link MethodHandle} which can get the indexed field of this species.
 284          * The return type is the type of the species field it accesses.
 285          * The argument type is the {@code fieldHolder} class of this species.
 286          */
 287         protected MethodHandle getter(int i) {
 288             return getters.get(i);
 289         }
 290 
 291         /**
 292          * Return a {@link LambdaForm.Name} containing a {@link LambdaForm.NamedFunction} that
 293          * represents a MH bound to a generic invoker, which in turn forwards to the corresponding
 294          * getter.
 295          */
 296         protected LambdaForm.NamedFunction getterFunction(int i) {
 297             LambdaForm.NamedFunction nf = nominalGetters.get(i);
 298             assert(nf.memberDeclaringClassOrNull() == speciesCode());
 299             assert(nf.returnType() == BasicType.basicType(fieldTypes.get(i)));
 300             return nf;
 301         }
 302 
 303         protected List<LambdaForm.NamedFunction> getterFunctions() {
 304             return nominalGetters;
 305         }
 306 
 307         protected List<MethodHandle> getters() {
 308             return getters;
 309         }
 310 
 311         protected MethodHandle factory() {
 312             return factories.get(0);
 313         }
 314 
 315         protected MethodHandle transformHelper(int whichtm) {
 316             MethodHandle mh = transformHelpers[whichtm];
 317             if (mh != null)  return mh;
 318             mh = deriveTransformHelper(transformMethods().get(whichtm), whichtm);
 319             // Do a little type checking before we start using the MH.
 320             // (It will be called with invokeBasic, so this is our only chance.)
 321             final MethodType mt = transformHelperType(whichtm);
 322             mh = mh.asType(mt);
 323             return transformHelpers[whichtm] = mh;
 324         }
 325 
 326         private final MethodType transformHelperType(int whichtm) {
 327             MemberName tm = transformMethods().get(whichtm);
 328             ArrayList<Class<?>> args = new ArrayList<>();
 329             ArrayList<Class<?>> fields = new ArrayList<>();
 330             Collections.addAll(args, tm.getParameterTypes());
 331             fields.addAll(fieldTypes());
 332             List<Class<?>> helperArgs = deriveTransformHelperArguments(tm, whichtm, args, fields);
 333             return MethodType.methodType(tm.getReturnType(), helperArgs);
 334         }
 335 
 336         // Hooks for subclasses:
 337 
 338         /**
 339          * Given a key, derive the list of field types, which all instances of this
 340          * species must store.
 341          */
 342         protected abstract List<Class<?>> deriveFieldTypes(K key);
 343 
 344         /**
 345          * Given the index of a method in the transforms list, supply a factory
 346          * method that takes the arguments of the transform, plus the local fields,
 347          * and produce a value of the required type.
 348          * You can override this to return null or throw if there are no transforms.
 349          * This method exists so that the transforms can be "grown" lazily.
 350          * This is necessary if the transform *adds* a field to an instance,
 351          * which sometimtes requires the creation, on the fly, of an extended species.
 352          * This method is only called once for any particular parameter.
 353          * The species caches the result in a private array.
 354          *
 355          * @param transform the transform being implemented
 356          * @param whichtm the index of that transform in the original list of transforms
 357          * @return the method handle which creates a new result from a mix of transform
 358          * arguments and field values
 359          */
 360         protected abstract MethodHandle deriveTransformHelper(MemberName transform, int whichtm);
 361 
 362         /**
 363          * During code generation, this method is called once per transform to determine
 364          * what is the mix of arguments to hand to the transform-helper.  The bytecode
 365          * which marshals these arguments is open-coded in the species-specific transform.
 366          * The two lists are of opaque objects, which you shouldn't do anything with besides
 367          * reordering them into the output list.  (They are both mutable, to make editing
 368          * easier.)  The imputed types of the args correspond to the transform's parameter
 369          * list, while the imputed types of the fields correspond to the species field types.
 370          * After code generation, this method may be called occasionally by error-checking code.
 371          *
 372          * @param transform the transform being implemented
 373          * @param whichtm the index of that transform in the original list of transforms
 374          * @param args a list of opaque objects representing the incoming transform arguments
 375          * @param fields a list of opaque objects representing the field values of the receiver
 376          * @param <X> the common element type of the various lists
 377          * @return a new list
 378          */
 379         protected abstract <X> List<X> deriveTransformHelperArguments(MemberName transform, int whichtm,
 380                                                                       List<X> args, List<X> fields);
 381 
 382         /** Given a key, generate the name of the class which implements the species for that key.
 383          * This algorithm must be stable.
 384          *
 385          * @return class name, which by default is {@code outer().topClass().getName() + "$Species_" + deriveTypeString(key)}
 386          */
 387         protected String deriveClassName() {
 388             return outer().topClass().getName() + "$Species_" + deriveTypeString();
 389         }
 390 
 391         /**
 392          * Default implementation collects basic type characters,
 393          * plus possibly type names, if some types don't correspond
 394          * to basic types.
 395          *
 396          * @return a string suitable for use in a class name
 397          */
 398         protected String deriveTypeString() {
 399             List<Class<?>> types = fieldTypes();
 400             StringBuilder buf = new StringBuilder();
 401             StringBuilder end = new StringBuilder();
 402             for (Class<?> type : types) {
 403                 BasicType basicType = BasicType.basicType(type);
 404                 if (basicType.basicTypeClass() == type) {
 405                     buf.append(basicType.basicTypeChar());
 406                 } else {
 407                     buf.append('V');
 408                     end.append(classSig(type));
 409                 }
 410             }
 411             String typeString;
 412             if (end.length() > 0) {
 413                 typeString = BytecodeName.toBytecodeName(buf.append("_").append(end).toString());
 414             } else {
 415                 typeString = buf.toString();
 416             }
 417             return LambdaForm.shortenSignature(typeString);
 418         }
 419 
 420         /**
 421          * Report what immediate super-class to use for the concrete class of this species.
 422          * Normally this is {@code topClass}, but if that is an interface, the factory must override.
 423          * The super-class must provide a constructor which takes the {@code baseConstructorType} arguments, if any.
 424          * This hook also allows the code generator to use more than one canned supertype for species.
 425          *
 426          * @return the super-class of the class to be generated
 427          */
 428         protected Class<? extends T> deriveSuperClass() {
 429             final Class<T> topc = topClass();
 430             if (!topClassIsSuper) {
 431                 try {
 432                     final Constructor<T> con = reflectConstructor(topc, baseConstructorType().parameterArray());
 433                     if (!topc.isInterface() && !Modifier.isPrivate(con.getModifiers())) {
 434                         topClassIsSuper = true;
 435                     }
 436                 } catch (Exception|InternalError ex) {
 437                     // fall through...
 438                 }
 439                 if (!topClassIsSuper) {
 440                     throw newInternalError("must override if the top class cannot serve as a super class");
 441                 }
 442             }
 443             return topc;
 444         }
 445     }
 446 
 447     protected abstract S newSpeciesData(K key);
 448 
 449     protected K topSpeciesKey() {
 450         return null;  // null means don't report a top species
 451     }
 452 
 453     /**
 454      * Code generation support for instances.
 455      * Subclasses can modify the behavior.
 456      */
 457     public class Factory {
 458         /**
 459          * Get a concrete subclass of the top class for a given combination of bound types.
 460          *
 461          * @param speciesData the species requiring the class, not yet linked
 462          * @return a linked version of the same species
 463          */
 464         S loadSpecies(S speciesData) {
 465             String className = speciesData.deriveClassName();
 466             assert(className.indexOf('/') < 0) : className;
 467             Class<?> salvage = null;
 468             try {
 469                 salvage = BootLoader.loadClassOrNull(className);
 470                 if (TRACE_RESOLVE && salvage != null) {
 471                     // Used by jlink species pregeneration plugin, see
 472                     // jdk.tools.jlink.internal.plugins.GenerateJLIClassesPlugin
 473                     System.out.println("[SPECIES_RESOLVE] " + className + " (salvaged)");
 474                 }
 475             } catch (Error ex) {
 476                 if (TRACE_RESOLVE) {
 477                     System.out.println("[SPECIES_FRESOLVE] " + className + " (Error) " + ex.getMessage());
 478                 }
 479             }
 480             final Class<? extends T> speciesCode;
 481             if (salvage != null) {
 482                 speciesCode = salvage.asSubclass(topClass());
 483                 linkSpeciesDataToCode(speciesData, speciesCode);
 484                 linkCodeToSpeciesData(speciesCode, speciesData, true);
 485             } else {
 486                 // Not pregenerated, generate the class
 487                 try {
 488                     speciesCode = generateConcreteSpeciesCode(className, speciesData);
 489                     if (TRACE_RESOLVE) {
 490                         // Used by jlink species pregeneration plugin, see
 491                         // jdk.tools.jlink.internal.plugins.GenerateJLIClassesPlugin
 492                         System.out.println("[SPECIES_RESOLVE] " + className + " (generated)");
 493                     }
 494                     // This operation causes a lot of churn:
 495                     linkSpeciesDataToCode(speciesData, speciesCode);
 496                     // This operation commits the relation, but causes little churn:
 497                     linkCodeToSpeciesData(speciesCode, speciesData, false);
 498                 } catch (Error ex) {
 499                     if (TRACE_RESOLVE) {
 500                         System.out.println("[SPECIES_RESOLVE] " + className + " (Error #2)" );
 501                     }
 502                     // We can get here if there is a race condition loading a class.
 503                     // Or maybe we are out of resources.  Back out of the CHM.get and retry.
 504                     throw ex;
 505                 }
 506             }
 507 
 508             if (!speciesData.isResolved()) {
 509                 throw newInternalError("bad species class linkage for " + className + ": " + speciesData);
 510             }
 511             assert(speciesData == loadSpeciesDataFromCode(speciesCode));
 512             return speciesData;
 513         }
 514 
 515         /**
 516          * Generate a concrete subclass of the top class for a given combination of bound types.
 517          *
 518          * A concrete species subclass roughly matches the following schema:
 519          *
 520          * <pre>
 521          * class Species_[[types]] extends [[T]] {
 522          *     final [[S]] speciesData() { return ... }
 523          *     static [[T]] make([[fields]]) { return ... }
 524          *     [[fields]]
 525          *     final [[T]] transform([[args]]) { return ... }
 526          * }
 527          * </pre>
 528          *
 529          * The {@code [[types]]} signature is precisely the key for the species.
 530          *
 531          * The {@code [[fields]]} section consists of one field definition per character in
 532          * the type signature, adhering to the naming schema described in the definition of
 533          * {@link #chooseFieldName}.
 534          *
 535          * For example, a concrete species for two references and one integral bound value
 536          * has a shape like the following:
 537          *
 538          * <pre>
 539          * class TopClass { ... private static
 540          * final class Species_LLI extends TopClass {
 541          *     final Object argL0;
 542          *     final Object argL1;
 543          *     final int argI2;
 544          *     private Species_LLI(CT ctarg, ..., Object argL0, Object argL1, int argI2) {
 545          *         super(ctarg, ...);
 546          *         this.argL0 = argL0;
 547          *         this.argL1 = argL1;
 548          *         this.argI2 = argI2;
 549          *     }
 550          *     final SpeciesData speciesData() { return BMH_SPECIES; }
 551          *     @Stable static SpeciesData BMH_SPECIES; // injected afterwards
 552          *     static TopClass make(CT ctarg, ..., Object argL0, Object argL1, int argI2) {
 553          *         return new Species_LLI(ctarg, ..., argL0, argL1, argI2);
 554          *     }
 555          *     final TopClass copyWith(CT ctarg, ...) {
 556          *         return new Species_LLI(ctarg, ..., argL0, argL1, argI2);
 557          *     }
 558          *     // two transforms, for the sake of illustration:
 559          *     final TopClass copyWithExtendL(CT ctarg, ..., Object narg) {
 560          *         return BMH_SPECIES.transform(L_TYPE).invokeBasic(ctarg, ..., argL0, argL1, argI2, narg);
 561          *     }
 562          *     final TopClass copyWithExtendI(CT ctarg, ..., int narg) {
 563          *         return BMH_SPECIES.transform(I_TYPE).invokeBasic(ctarg, ..., argL0, argL1, argI2, narg);
 564          *     }
 565          * }
 566          * </pre>
 567          *
 568          * @param className of the species
 569          * @param speciesData what species we are generating
 570          * @return the generated concrete TopClass class
 571          */
 572         Class<? extends T> generateConcreteSpeciesCode(String className, ClassSpecializer<T,K,S>.SpeciesData speciesData) {
 573             byte[] classFile = generateConcreteSpeciesCodeFile(className, speciesData);
 574 
 575             // load class
 576             InvokerBytecodeGenerator.maybeDump(classBCName(className), classFile);
 577             Class<?> speciesCode;
 578 
 579             ClassLoader cl = topClass().getClassLoader();
 580             ProtectionDomain pd = null;
 581             if (cl != null) {
 582                 pd = AccessController.doPrivileged(
 583                         new PrivilegedAction<>() {
 584                             @Override
 585                             public ProtectionDomain run() {
 586                                 return topClass().getProtectionDomain();
 587                             }
 588                         });
 589             }
 590             try {
 591                 speciesCode = UNSAFE.defineClass(className, classFile, 0, classFile.length, cl, pd);
 592             } catch (Exception ex) {
 593                 throw newInternalError(ex);
 594             }
 595 
 596             return speciesCode.asSubclass(topClass());
 597         }
 598 
 599         // These are named like constants because there is only one per specialization scheme:
 600         private final String SPECIES_DATA = classBCName(metaType);
 601         private final String SPECIES_DATA_SIG = classSig(SPECIES_DATA);
 602         private final String SPECIES_DATA_NAME = sdAccessor.getName();
 603         private final int SPECIES_DATA_MODS = sdAccessor.getModifiers();
 604         private final List<String> TRANSFORM_NAMES;  // derived from transformMethods
 605         private final List<MethodType> TRANSFORM_TYPES;
 606         private final List<Integer> TRANSFORM_MODS;
 607         {
 608             // Tear apart transformMethods to get the names, types, and modifiers.
 609             List<String> tns = new ArrayList<>();
 610             List<MethodType> tts = new ArrayList<>();
 611             List<Integer> tms = new ArrayList<>();
 612             for (int i = 0; i < transformMethods.size(); i++) {
 613                 MemberName tm = transformMethods.get(i);
 614                 tns.add(tm.getName());
 615                 final MethodType tt = tm.getMethodType();
 616                 tts.add(tt);
 617                 tms.add(tm.getModifiers());
 618             }
 619             TRANSFORM_NAMES = List.of(tns.toArray(new String[0]));
 620             TRANSFORM_TYPES = List.of(tts.toArray(new MethodType[0]));
 621             TRANSFORM_MODS = List.of(tms.toArray(new Integer[0]));
 622         }
 623         private static final int ACC_PPP = ACC_PUBLIC | ACC_PRIVATE | ACC_PROTECTED;
 624 
 625         /*non-public*/ byte[] generateConcreteSpeciesCodeFile(String className0, ClassSpecializer<T,K,S>.SpeciesData speciesData) {
 626             final String className = classBCName(className0);
 627             final String superClassName = classBCName(speciesData.deriveSuperClass());
 628 
 629             final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS + ClassWriter.COMPUTE_FRAMES);
 630             final int NOT_ACC_PUBLIC = 0;  // not ACC_PUBLIC
 631             cw.visit(V1_6, NOT_ACC_PUBLIC + ACC_FINAL + ACC_SUPER, className, null, superClassName, null);
 632 
 633             final String sourceFile = className.substring(className.lastIndexOf('.')+1);
 634             cw.visitSource(sourceFile, null);
 635 
 636             // emit static types and BMH_SPECIES fields
 637             FieldVisitor fw = cw.visitField(NOT_ACC_PUBLIC + ACC_STATIC, sdFieldName, SPECIES_DATA_SIG, null, null);
 638             fw.visitAnnotation(STABLE_SIG, true);
 639             fw.visitEnd();
 640 
 641             // handy holder for dealing with groups of typed values (ctor arguments and fields)
 642             class Var {
 643                 final int index;
 644                 final String name;
 645                 final Class<?> type;
 646                 final String desc;
 647                 final BasicType basicType;
 648                 final int slotIndex;
 649                 Var(int index, int slotIndex) {
 650                     this.index = index;
 651                     this.slotIndex = slotIndex;
 652                     name = null; type = null; desc = null;
 653                     basicType = BasicType.V_TYPE;
 654                 }
 655                 Var(String name, Class<?> type, Var prev) {
 656                     int slotIndex = prev.nextSlotIndex();
 657                     int index = prev.nextIndex();
 658                     if (name == null)  name = "x";
 659                     if (name.endsWith("#"))
 660                         name = name.substring(0, name.length()-1) + index;
 661                     assert(!type.equals(void.class));
 662                     String desc = classSig(type);
 663                     BasicType basicType = BasicType.basicType(type);
 664                     this.index = index;
 665                     this.name = name;
 666                     this.type = type;
 667                     this.desc = desc;
 668                     this.basicType = basicType;
 669                     this.slotIndex = slotIndex;
 670                 }
 671                 Var lastOf(List<Var> vars) {
 672                     int n = vars.size();
 673                     return (n == 0 ? this : vars.get(n-1));
 674                 }
 675                 <X> List<Var> fromTypes(List<X> types) {
 676                     Var prev = this;
 677                     ArrayList<Var> result = new ArrayList<>(types.size());
 678                     int i = 0;
 679                     for (X x : types) {
 680                         String vn = name;
 681                         Class<?> vt;
 682                         if (x instanceof Class) {
 683                             vt = (Class<?>) x;
 684                             // make the names friendlier if debugging
 685                             assert((vn = vn + "_" + (i++)) != null);
 686                         } else {
 687                             @SuppressWarnings("unchecked")
 688                             Var v = (Var) x;
 689                             vn = v.name;
 690                             vt = v.type;
 691                         }
 692                         prev = new Var(vn, vt, prev);
 693                         result.add(prev);
 694                     }
 695                     return result;
 696                 }
 697 
 698                 int slotSize() { return basicType.basicTypeSlots(); }
 699                 int nextIndex() { return index + (slotSize() == 0 ? 0 : 1); }
 700                 int nextSlotIndex() { return slotIndex >= 0 ? slotIndex + slotSize() : slotIndex; }
 701                 boolean isInHeap() { return slotIndex < 0; }
 702                 void emitVarInstruction(int asmop, MethodVisitor mv) {
 703                     if (asmop == ALOAD)
 704                         asmop = typeLoadOp(basicType.basicTypeChar());
 705                     else
 706                         throw new AssertionError("bad op="+asmop+" for desc="+desc);
 707                     mv.visitVarInsn(asmop, slotIndex);
 708                 }
 709                 public void emitFieldInsn(int asmop, MethodVisitor mv) {
 710                     mv.visitFieldInsn(asmop, className, name, desc);
 711                 }
 712             }
 713 
 714             final Var NO_THIS = new Var(0, 0),
 715                     AFTER_THIS = new Var(0, 1),
 716                     IN_HEAP = new Var(0, -1);
 717 
 718             // figure out the field types
 719             final List<Class<?>> fieldTypes = speciesData.fieldTypes();
 720             final List<Var> fields = new ArrayList<>(fieldTypes.size());
 721             {
 722                 Var nextF = IN_HEAP;
 723                 for (Class<?> ft : fieldTypes) {
 724                     String fn = chooseFieldName(ft, nextF.nextIndex());
 725                     nextF = new Var(fn, ft, nextF);
 726                     fields.add(nextF);
 727                 }
 728             }
 729 
 730             // emit bound argument fields
 731             for (Var field : fields) {
 732                 cw.visitField(ACC_FINAL, field.name, field.desc, null, null).visitEnd();
 733             }
 734 
 735             MethodVisitor mv;
 736 
 737             // emit implementation of speciesData()
 738             mv = cw.visitMethod((SPECIES_DATA_MODS & ACC_PPP) + ACC_FINAL,
 739                     SPECIES_DATA_NAME, "()" + SPECIES_DATA_SIG, null, null);
 740             mv.visitCode();
 741             mv.visitFieldInsn(GETSTATIC, className, sdFieldName, SPECIES_DATA_SIG);
 742             mv.visitInsn(ARETURN);
 743             mv.visitMaxs(0, 0);
 744             mv.visitEnd();
 745 
 746             // figure out the constructor arguments
 747             MethodType superCtorType = ClassSpecializer.this.baseConstructorType();
 748             MethodType thisCtorType = superCtorType.appendParameterTypes(fieldTypes);
 749 
 750             // emit constructor
 751             {
 752                 mv = cw.visitMethod(ACC_PRIVATE,
 753                         "<init>", methodSig(thisCtorType), null, null);
 754                 mv.visitCode();
 755                 mv.visitVarInsn(ALOAD, 0); // this
 756 
 757                 final List<Var> ctorArgs = AFTER_THIS.fromTypes(superCtorType.parameterList());
 758                 for (Var ca : ctorArgs) {
 759                     ca.emitVarInstruction(ALOAD, mv);
 760                 }
 761 
 762                 // super(ca...)
 763                 mv.visitMethodInsn(INVOKESPECIAL, superClassName,
 764                         "<init>", methodSig(superCtorType), false);
 765 
 766                 // store down fields
 767                 Var lastFV = AFTER_THIS.lastOf(ctorArgs);
 768                 for (Var f : fields) {
 769                     // this.argL1 = argL1
 770                     mv.visitVarInsn(ALOAD, 0);  // this
 771                     lastFV = new Var(f.name, f.type, lastFV);
 772                     lastFV.emitVarInstruction(ALOAD, mv);
 773                     f.emitFieldInsn(PUTFIELD, mv);
 774                 }
 775 
 776                 mv.visitInsn(RETURN);
 777                 mv.visitMaxs(0, 0);
 778                 mv.visitEnd();
 779             }
 780 
 781             // emit make()  ...factory method wrapping constructor
 782             {
 783                 MethodType ftryType = thisCtorType.changeReturnType(topClass());
 784                 mv = cw.visitMethod(NOT_ACC_PUBLIC + ACC_STATIC,
 785                         "make", methodSig(ftryType), null, null);
 786                 mv.visitCode();
 787                 // make instance
 788                 mv.visitTypeInsn(NEW, className);
 789                 mv.visitInsn(DUP);
 790                 // load factory method arguments:  ctarg... and arg...
 791                 for (Var v : NO_THIS.fromTypes(ftryType.parameterList())) {
 792                     v.emitVarInstruction(ALOAD, mv);
 793                 }
 794 
 795                 // finally, invoke the constructor and return
 796                 mv.visitMethodInsn(INVOKESPECIAL, className,
 797                         "<init>", methodSig(thisCtorType), false);
 798                 mv.visitInsn(ARETURN);
 799                 mv.visitMaxs(0, 0);
 800                 mv.visitEnd();
 801             }
 802 
 803             // For each transform, emit the customized override of the transform method.
 804             // This method mixes together some incoming arguments (from the transform's
 805             // static type signature) with the field types themselves, and passes
 806             // the resulting mish-mosh of values to a method handle produced by
 807             // the species itself.  (Typically this method handle is the factory
 808             // method of this species or a related one.)
 809             for (int whichtm = 0; whichtm < TRANSFORM_NAMES.size(); whichtm++) {
 810                 final String     TNAME = TRANSFORM_NAMES.get(whichtm);
 811                 final MethodType TTYPE = TRANSFORM_TYPES.get(whichtm);
 812                 final int        TMODS = TRANSFORM_MODS.get(whichtm);
 813                 mv = cw.visitMethod((TMODS & ACC_PPP) | ACC_FINAL,
 814                         TNAME, TTYPE.toMethodDescriptorString(), null, E_THROWABLE);
 815                 mv.visitCode();
 816                 // return a call to the corresponding "transform helper", something like this:
 817                 //   MY_SPECIES.transformHelper(whichtm).invokeBasic(ctarg, ..., argL0, ..., xarg)
 818                 mv.visitFieldInsn(GETSTATIC, className,
 819                         sdFieldName, SPECIES_DATA_SIG);
 820                 emitIntConstant(whichtm, mv);
 821                 mv.visitMethodInsn(INVOKEVIRTUAL, SPECIES_DATA,
 822                         "transformHelper", "(I)" + MH_SIG, false);
 823 
 824                 List<Var> targs = AFTER_THIS.fromTypes(TTYPE.parameterList());
 825                 List<Var> tfields = new ArrayList<>(fields);
 826                 // mix them up and load them for the transform helper:
 827                 List<Var> helperArgs = speciesData.deriveTransformHelperArguments(transformMethods.get(whichtm), whichtm, targs, tfields);
 828                 List<Class<?>> helperTypes = new ArrayList<>(helperArgs.size());
 829                 for (Var ha : helperArgs) {
 830                     helperTypes.add(ha.basicType.basicTypeClass());
 831                     if (ha.isInHeap()) {
 832                         assert(tfields.contains(ha));
 833                         mv.visitVarInsn(ALOAD, 0);
 834                         ha.emitFieldInsn(GETFIELD, mv);
 835                     } else {
 836                         assert(targs.contains(ha));
 837                         ha.emitVarInstruction(ALOAD, mv);
 838                     }
 839                 }
 840 
 841                 // jump into the helper (which is probably a factory method)
 842                 final Class<?> rtype = TTYPE.returnType();
 843                 final BasicType rbt = BasicType.basicType(rtype);
 844                 MethodType invokeBasicType = MethodType.methodType(rbt.basicTypeClass(), helperTypes);
 845                 mv.visitMethodInsn(INVOKEVIRTUAL, MH,
 846                         "invokeBasic", methodSig(invokeBasicType), false);
 847                 if (rbt == BasicType.L_TYPE) {
 848                     mv.visitTypeInsn(CHECKCAST, classBCName(rtype));
 849                     mv.visitInsn(ARETURN);
 850                 } else {
 851                     throw newInternalError("NYI: transform of type "+rtype);
 852                 }
 853                 mv.visitMaxs(0, 0);
 854                 mv.visitEnd();
 855             }
 856 
 857             cw.visitEnd();
 858 
 859             return cw.toByteArray();
 860         }
 861 
 862         private int typeLoadOp(char t) {
 863             switch (t) {
 864             case 'L': return ALOAD;
 865             case 'I': return ILOAD;
 866             case 'J': return LLOAD;
 867             case 'F': return FLOAD;
 868             case 'D': return DLOAD;
 869             default : throw newInternalError("unrecognized type " + t);
 870             }
 871         }
 872 
 873         private void emitIntConstant(int con, MethodVisitor mv) {
 874             if (ICONST_M1 - ICONST_0 <= con && con <= ICONST_5 - ICONST_0)
 875                 mv.visitInsn(ICONST_0 + con);
 876             else if (con == (byte) con)
 877                 mv.visitIntInsn(BIPUSH, con);
 878             else if (con == (short) con)
 879                 mv.visitIntInsn(SIPUSH, con);
 880             else {
 881                 mv.visitLdcInsn(con);
 882             }
 883 
 884         }
 885 
 886         //
 887         // Getter MH generation.
 888         //
 889 
 890         private MethodHandle findGetter(Class<?> speciesCode, List<Class<?>> types, int index) {
 891             Class<?> fieldType = types.get(index);
 892             String fieldName = chooseFieldName(fieldType, index);
 893             try {
 894                 return IMPL_LOOKUP.findGetter(speciesCode, fieldName, fieldType);
 895             } catch (NoSuchFieldException | IllegalAccessException e) {
 896                 throw newInternalError(e);
 897             }
 898         }
 899 
 900         private List<MethodHandle> findGetters(Class<?> speciesCode, List<Class<?>> types) {
 901             MethodHandle[] mhs = new MethodHandle[types.size()];
 902             for (int i = 0; i < mhs.length; ++i) {
 903                 mhs[i] = findGetter(speciesCode, types, i);
 904                 assert(mhs[i].internalMemberName().getDeclaringClass() == speciesCode);
 905             }
 906             return List.of(mhs);
 907         }
 908 
 909         private List<MethodHandle> findFactories(Class<? extends T> speciesCode, List<Class<?>> types) {
 910             MethodHandle[] mhs = new MethodHandle[1];
 911             mhs[0] = findFactory(speciesCode, types);
 912             return List.of(mhs);
 913         }
 914 
 915         List<LambdaForm.NamedFunction> makeNominalGetters(List<Class<?>> types, List<MethodHandle> getters) {
 916             LambdaForm.NamedFunction[] nfs = new LambdaForm.NamedFunction[types.size()];
 917             for (int i = 0; i < nfs.length; ++i) {
 918                 nfs[i] = new LambdaForm.NamedFunction(getters.get(i));
 919             }
 920             return List.of(nfs);
 921         }
 922 
 923         //
 924         // Auxiliary methods.
 925         //
 926 
 927         protected void linkSpeciesDataToCode(ClassSpecializer<T,K,S>.SpeciesData speciesData, Class<? extends T> speciesCode) {
 928             speciesData.speciesCode = speciesCode.asSubclass(topClass);
 929             final List<Class<?>> types = speciesData.fieldTypes;
 930             speciesData.factories = this.findFactories(speciesCode, types);
 931             speciesData.getters = this.findGetters(speciesCode, types);
 932             speciesData.nominalGetters = this.makeNominalGetters(types, speciesData.getters);
 933         }
 934 
 935         private Field reflectSDField(Class<? extends T> speciesCode) {
 936             final Field field = reflectField(speciesCode, sdFieldName);
 937             assert(field.getType() == metaType);
 938             assert(Modifier.isStatic(field.getModifiers()));
 939             return field;
 940         }
 941 
 942         private S readSpeciesDataFromCode(Class<? extends T> speciesCode) {
 943             try {
 944                 MemberName sdField = IMPL_LOOKUP.resolveOrFail(REF_getStatic, speciesCode, sdFieldName, metaType);
 945                 Object base = MethodHandleNatives.staticFieldBase(sdField);
 946                 long offset = MethodHandleNatives.staticFieldOffset(sdField);
 947                 UNSAFE.loadFence();
 948                 return metaType.cast(UNSAFE.getObject(base, offset));
 949             } catch (Error err) {
 950                 throw err;
 951             } catch (Exception ex) {
 952                 throw newInternalError("Failed to load speciesData from speciesCode: " + speciesCode.getName(), ex);
 953             } catch (Throwable t) {
 954                 throw uncaughtException(t);
 955             }
 956         }
 957 
 958         protected S loadSpeciesDataFromCode(Class<? extends T> speciesCode) {
 959             if (speciesCode == topClass()) {
 960                 return topSpecies;
 961             }
 962             S result = readSpeciesDataFromCode(speciesCode);
 963             if (result.outer() != ClassSpecializer.this) {
 964                 throw newInternalError("wrong class");
 965             }
 966             return result;
 967         }
 968 
 969         protected void linkCodeToSpeciesData(Class<? extends T> speciesCode, ClassSpecializer<T,K,S>.SpeciesData speciesData, boolean salvage) {
 970             try {
 971                 assert(readSpeciesDataFromCode(speciesCode) == null ||
 972                     (salvage && readSpeciesDataFromCode(speciesCode).equals(speciesData)));
 973 
 974                 MemberName sdField = IMPL_LOOKUP.resolveOrFail(REF_putStatic, speciesCode, sdFieldName, metaType);
 975                 Object base = MethodHandleNatives.staticFieldBase(sdField);
 976                 long offset = MethodHandleNatives.staticFieldOffset(sdField);
 977                 UNSAFE.storeFence();
 978                 UNSAFE.putObject(base, offset, speciesData);
 979                 UNSAFE.storeFence();
 980             } catch (Error err) {
 981                 throw err;
 982             } catch (Exception ex) {
 983                 throw newInternalError("Failed to link speciesData to speciesCode: " + speciesCode.getName(), ex);
 984             } catch (Throwable t) {
 985                 throw uncaughtException(t);
 986             }
 987         }
 988 
 989         /**
 990          * Field names in concrete species classes adhere to this pattern:
 991          * type + index, where type is a single character (L, I, J, F, D).
 992          * The factory subclass can customize this.
 993          * The name is purely cosmetic, since it applies to a private field.
 994          */
 995         protected String chooseFieldName(Class<?> type, int index) {
 996             BasicType bt = BasicType.basicType(type);
 997             return "" + bt.basicTypeChar() + index;
 998         }
 999 
1000         MethodHandle findFactory(Class<? extends T> speciesCode, List<Class<?>> types) {
1001             final MethodType type = baseConstructorType().changeReturnType(topClass()).appendParameterTypes(types);
1002             try {
1003                 return IMPL_LOOKUP.findStatic(speciesCode, "make", type);
1004             } catch (NoSuchMethodException | IllegalAccessException | IllegalArgumentException | TypeNotPresentException e) {
1005                 throw newInternalError(e);
1006             }
1007         }
1008     }
1009 
1010     /** Hook that virtualizes the Factory class, allowing subclasses to extend it. */
1011     protected Factory makeFactory() {
1012         return new Factory();
1013     }
1014 
1015 
1016     // Other misc helpers:
1017     private static final String MH = "java/lang/invoke/MethodHandle";
1018     private static final String MH_SIG = "L" + MH + ";";
1019     private static final String STABLE = "jdk/internal/vm/annotation/Stable";
1020     private static final String STABLE_SIG = "L" + STABLE + ";";
1021     private static final String[] E_THROWABLE = new String[] { "java/lang/Throwable" };
1022     static {
1023         assert(MH_SIG.equals(classSig(MethodHandle.class)));
1024         assert(MH.equals(classBCName(MethodHandle.class)));
1025     }
1026 
1027     static String methodSig(MethodType mt) {
1028         return mt.toMethodDescriptorString();
1029     }
1030     static String classSig(Class<?> cls) {
1031         if (cls.isPrimitive() || cls.isArray())
1032             return MethodType.methodType(cls).toMethodDescriptorString().substring(2);
1033         return classSig(classBCName(cls));
1034     }
1035     static String classSig(String bcName) {
1036         assert(bcName.indexOf('.') < 0);
1037         assert(!bcName.endsWith(";"));
1038         assert(!bcName.startsWith("["));
1039         return "L" + bcName + ";";
1040     }
1041     static String classBCName(Class<?> cls) {
1042         return classBCName(className(cls));
1043     }
1044     static String classBCName(String str) {
1045         assert(str.indexOf('/') < 0) : str;
1046         return str.replace('.', '/');
1047     }
1048     static String className(Class<?> cls) {
1049         assert(!cls.isArray() && !cls.isPrimitive());
1050         return cls.getName();
1051     }
1052 }