1 /*
   2  * Copyright (c) 2008, 2013, 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 java.security.AccessController;
  29 import java.security.PrivilegedAction;
  30 import java.util.ArrayList;
  31 import java.util.Arrays;
  32 import java.util.Collections;
  33 import java.util.function.Function;
  34 
  35 import sun.invoke.empty.Empty;
  36 import sun.invoke.util.ValueConversions;
  37 import sun.invoke.util.VerifyType;
  38 import sun.invoke.util.Wrapper;
  39 import sun.reflect.CallerSensitive;
  40 import sun.reflect.Reflection;
  41 import static java.lang.invoke.LambdaForm.*;
  42 import static java.lang.invoke.MethodHandleStatics.*;
  43 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
  44 
  45 /**
  46  * Trusted implementation code for MethodHandle.
  47  * @author jrose
  48  */
  49 /*non-public*/ abstract class MethodHandleImpl {
  50     // Do not adjust this except for special platforms:
  51     private static final int MAX_ARITY;
  52     static {
  53         final Object[] values = { 255 };
  54         AccessController.doPrivileged(new PrivilegedAction<Void>() {
  55             @Override
  56             public Void run() {
  57                 values[0] = Integer.getInteger(MethodHandleImpl.class.getName()+".MAX_ARITY", 255);
  58                 return null;
  59             }
  60         });
  61         MAX_ARITY = (Integer) values[0];
  62     }
  63 
  64     /// Factory methods to create method handles:
  65 
  66     static void initStatics() {
  67         // Trigger selected static initializations.
  68         MemberName.Factory.INSTANCE.getClass();
  69     }
  70 
  71     static MethodHandle makeArrayElementAccessor(Class<?> arrayClass, boolean isSetter) {
  72         if (arrayClass == Object[].class)
  73             return (isSetter ? ArrayAccessor.OBJECT_ARRAY_SETTER : ArrayAccessor.OBJECT_ARRAY_GETTER);
  74         if (!arrayClass.isArray())
  75             throw newIllegalArgumentException("not an array: "+arrayClass);
  76         MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass);
  77         int cacheIndex = (isSetter ? ArrayAccessor.SETTER_INDEX : ArrayAccessor.GETTER_INDEX);
  78         MethodHandle mh = cache[cacheIndex];
  79         if (mh != null)  return mh;
  80         mh = ArrayAccessor.getAccessor(arrayClass, isSetter);
  81         MethodType correctType = ArrayAccessor.correctType(arrayClass, isSetter);
  82         if (mh.type() != correctType) {
  83             assert(mh.type().parameterType(0) == Object[].class);
  84             assert((isSetter ? mh.type().parameterType(2) : mh.type().returnType()) == Object.class);
  85             assert(isSetter || correctType.parameterType(0).getComponentType() == correctType.returnType());
  86             // safe to view non-strictly, because element type follows from array type
  87             mh = mh.viewAsType(correctType, false);
  88         }
  89         mh = makeIntrinsic(mh, (isSetter ? Intrinsic.ARRAY_STORE : Intrinsic.ARRAY_LOAD));
  90         // Atomically update accessor cache.
  91         synchronized(cache) {
  92             if (cache[cacheIndex] == null) {
  93                 cache[cacheIndex] = mh;
  94             } else {
  95                 // Throw away newly constructed accessor and use cached version.
  96                 mh = cache[cacheIndex];
  97             }
  98         }
  99         return mh;
 100     }
 101 
 102     static final class ArrayAccessor {
 103         /// Support for array element access
 104         static final int GETTER_INDEX = 0, SETTER_INDEX = 1, INDEX_LIMIT = 2;
 105         static final ClassValue<MethodHandle[]> TYPED_ACCESSORS
 106                 = new ClassValue<MethodHandle[]>() {
 107                     @Override
 108                     protected MethodHandle[] computeValue(Class<?> type) {
 109                         return new MethodHandle[INDEX_LIMIT];
 110                     }
 111                 };
 112         static final MethodHandle OBJECT_ARRAY_GETTER, OBJECT_ARRAY_SETTER;
 113         static {
 114             MethodHandle[] cache = TYPED_ACCESSORS.get(Object[].class);
 115             cache[GETTER_INDEX] = OBJECT_ARRAY_GETTER = makeIntrinsic(getAccessor(Object[].class, false), Intrinsic.ARRAY_LOAD);
 116             cache[SETTER_INDEX] = OBJECT_ARRAY_SETTER = makeIntrinsic(getAccessor(Object[].class, true),  Intrinsic.ARRAY_STORE);
 117 
 118             assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_GETTER.internalMemberName()));
 119             assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_SETTER.internalMemberName()));
 120         }
 121 
 122         static int     getElementI(int[]     a, int i)            { return              a[i]; }
 123         static long    getElementJ(long[]    a, int i)            { return              a[i]; }
 124         static float   getElementF(float[]   a, int i)            { return              a[i]; }
 125         static double  getElementD(double[]  a, int i)            { return              a[i]; }
 126         static boolean getElementZ(boolean[] a, int i)            { return              a[i]; }
 127         static byte    getElementB(byte[]    a, int i)            { return              a[i]; }
 128         static short   getElementS(short[]   a, int i)            { return              a[i]; }
 129         static char    getElementC(char[]    a, int i)            { return              a[i]; }
 130         static Object  getElementL(Object[]  a, int i)            { return              a[i]; }
 131 
 132         static void    setElementI(int[]     a, int i, int     x) {              a[i] = x; }
 133         static void    setElementJ(long[]    a, int i, long    x) {              a[i] = x; }
 134         static void    setElementF(float[]   a, int i, float   x) {              a[i] = x; }
 135         static void    setElementD(double[]  a, int i, double  x) {              a[i] = x; }
 136         static void    setElementZ(boolean[] a, int i, boolean x) {              a[i] = x; }
 137         static void    setElementB(byte[]    a, int i, byte    x) {              a[i] = x; }
 138         static void    setElementS(short[]   a, int i, short   x) {              a[i] = x; }
 139         static void    setElementC(char[]    a, int i, char    x) {              a[i] = x; }
 140         static void    setElementL(Object[]  a, int i, Object  x) {              a[i] = x; }
 141 
 142         static String name(Class<?> arrayClass, boolean isSetter) {
 143             Class<?> elemClass = arrayClass.getComponentType();
 144             if (elemClass == null)  throw newIllegalArgumentException("not an array", arrayClass);
 145             return (!isSetter ? "getElement" : "setElement") + Wrapper.basicTypeChar(elemClass);
 146         }
 147         static MethodType type(Class<?> arrayClass, boolean isSetter) {
 148             Class<?> elemClass = arrayClass.getComponentType();
 149             Class<?> arrayArgClass = arrayClass;
 150             if (!elemClass.isPrimitive()) {
 151                 arrayArgClass = Object[].class;
 152                 elemClass = Object.class;
 153             }
 154             return !isSetter ?
 155                     MethodType.methodType(elemClass,  arrayArgClass, int.class) :
 156                     MethodType.methodType(void.class, arrayArgClass, int.class, elemClass);
 157         }
 158         static MethodType correctType(Class<?> arrayClass, boolean isSetter) {
 159             Class<?> elemClass = arrayClass.getComponentType();
 160             return !isSetter ?
 161                     MethodType.methodType(elemClass,  arrayClass, int.class) :
 162                     MethodType.methodType(void.class, arrayClass, int.class, elemClass);
 163         }
 164         static MethodHandle getAccessor(Class<?> arrayClass, boolean isSetter) {
 165             String     name = name(arrayClass, isSetter);
 166             MethodType type = type(arrayClass, isSetter);
 167             try {
 168                 return IMPL_LOOKUP.findStatic(ArrayAccessor.class, name, type);
 169             } catch (ReflectiveOperationException ex) {
 170                 throw uncaughtException(ex);
 171             }
 172         }
 173     }
 174 
 175     /**
 176      * Create a JVM-level adapter method handle to conform the given method
 177      * handle to the similar newType, using only pairwise argument conversions.
 178      * For each argument, convert incoming argument to the exact type needed.
 179      * The argument conversions allowed are casting, boxing and unboxing,
 180      * integral widening or narrowing, and floating point widening or narrowing.
 181      * @param srcType required call type
 182      * @param target original method handle
 183      * @param strict if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed
 184      * @param monobox if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)
 185      * @return an adapter to the original handle with the desired new type,
 186      *          or the original target if the types are already identical
 187      *          or null if the adaptation cannot be made
 188      */
 189     static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
 190                                             boolean strict, boolean monobox) {
 191         MethodType dstType = target.type();
 192         if (srcType == dstType)
 193             return target;
 194         return makePairwiseConvertByEditor(target, srcType, strict, monobox);
 195     }
 196 
 197     private static int countNonNull(Object[] array) {
 198         int count = 0;
 199         for (Object x : array) {
 200             if (x != null)  ++count;
 201         }
 202         return count;
 203     }
 204 
 205     static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType srcType,
 206                                                     boolean strict, boolean monobox) {
 207         Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);
 208         int convCount = countNonNull(convSpecs);
 209         if (convCount == 0)
 210             return target.viewAsType(srcType, strict);
 211         MethodType basicSrcType = srcType.basicType();
 212         MethodType midType = target.type().basicType();
 213         BoundMethodHandle mh = target.rebind();
 214         // FIXME: Reduce number of bindings when there is more than one Class conversion.
 215         // FIXME: Reduce number of bindings when there are repeated conversions.
 216         for (int i = 0; i < convSpecs.length-1; i++) {
 217             Object convSpec = convSpecs[i];
 218             if (convSpec == null)  continue;
 219             MethodHandle fn;
 220             if (convSpec instanceof Class) {
 221                 fn = Lazy.MH_castReference.bindTo(convSpec);
 222             } else {
 223                 fn = (MethodHandle) convSpec;
 224             }
 225             Class<?> newType = basicSrcType.parameterType(i);
 226             if (--convCount == 0)
 227                 midType = srcType;
 228             else
 229                 midType = midType.changeParameterType(i, newType);
 230             LambdaForm form2 = mh.editor().filterArgumentForm(1+i, BasicType.basicType(newType));
 231             mh = mh.copyWithExtendL(midType, form2, fn);
 232             mh = mh.rebind();
 233         }
 234         Object convSpec = convSpecs[convSpecs.length-1];
 235         if (convSpec != null) {
 236             MethodHandle fn;
 237             if (convSpec instanceof Class) {
 238                 if (convSpec == void.class)
 239                     fn = null;
 240                 else
 241                     fn = Lazy.MH_castReference.bindTo(convSpec);
 242             } else {
 243                 fn = (MethodHandle) convSpec;
 244             }
 245             Class<?> newType = basicSrcType.returnType();
 246             assert(--convCount == 0);
 247             midType = srcType;
 248             if (fn != null) {
 249                 mh = mh.rebind();  // rebind if too complex
 250                 LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), false);
 251                 mh = mh.copyWithExtendL(midType, form2, fn);
 252             } else {
 253                 LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), true);
 254                 mh = mh.copyWith(midType, form2);
 255             }
 256         }
 257         assert(convCount == 0);
 258         assert(mh.type().equals(srcType));
 259         return mh;
 260     }
 261 
 262     static MethodHandle makePairwiseConvertIndirect(MethodHandle target, MethodType srcType,
 263                                                     boolean strict, boolean monobox) {
 264         assert(target.type().parameterCount() == srcType.parameterCount());
 265         // Calculate extra arguments (temporaries) required in the names array.
 266         Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);
 267         final int INARG_COUNT = srcType.parameterCount();
 268         int convCount = countNonNull(convSpecs);
 269         boolean retConv = (convSpecs[INARG_COUNT] != null);
 270         boolean retVoid = srcType.returnType() == void.class;
 271         if (retConv && retVoid) {
 272             convCount -= 1;
 273             retConv = false;
 274         }
 275 
 276         final int IN_MH         = 0;
 277         final int INARG_BASE    = 1;
 278         final int INARG_LIMIT   = INARG_BASE + INARG_COUNT;
 279         final int NAME_LIMIT    = INARG_LIMIT + convCount + 1;
 280         final int RETURN_CONV   = (!retConv ? -1         : NAME_LIMIT - 1);
 281         final int OUT_CALL      = (!retConv ? NAME_LIMIT : RETURN_CONV) - 1;
 282         final int RESULT        = (retVoid ? -1 : NAME_LIMIT - 1);
 283 
 284         // Now build a LambdaForm.
 285         MethodType lambdaType = srcType.basicType().invokerType();
 286         Name[] names = arguments(NAME_LIMIT - INARG_LIMIT, lambdaType);
 287 
 288         // Collect the arguments to the outgoing call, maybe with conversions:
 289         final int OUTARG_BASE = 0;  // target MH is Name.function, name Name.arguments[0]
 290         Object[] outArgs = new Object[OUTARG_BASE + INARG_COUNT];
 291 
 292         int nameCursor = INARG_LIMIT;
 293         for (int i = 0; i < INARG_COUNT; i++) {
 294             Object convSpec = convSpecs[i];
 295             if (convSpec == null) {
 296                 // do nothing: difference is trivial
 297                 outArgs[OUTARG_BASE + i] = names[INARG_BASE + i];
 298                 continue;
 299             }
 300 
 301             Name conv;
 302             if (convSpec instanceof Class) {
 303                 Class<?> convClass = (Class<?>) convSpec;
 304                 conv = new Name(Lazy.MH_castReference, convClass, names[INARG_BASE + i]);
 305             } else {
 306                 MethodHandle fn = (MethodHandle) convSpec;
 307                 conv = new Name(fn, names[INARG_BASE + i]);
 308             }
 309             assert(names[nameCursor] == null);
 310             names[nameCursor++] = conv;
 311             assert(outArgs[OUTARG_BASE + i] == null);
 312             outArgs[OUTARG_BASE + i] = conv;
 313         }
 314 
 315         // Build argument array for the call.
 316         assert(nameCursor == OUT_CALL);
 317         names[OUT_CALL] = new Name(target, outArgs);
 318 
 319         Object convSpec = convSpecs[INARG_COUNT];
 320         if (!retConv) {
 321             assert(OUT_CALL == names.length-1);
 322         } else {
 323             Name conv;
 324             if (convSpec == void.class) {
 325                 conv = new Name(LambdaForm.constantZero(BasicType.basicType(srcType.returnType())));
 326             } else if (convSpec instanceof Class) {
 327                 Class<?> convClass = (Class<?>) convSpec;
 328                 conv = new Name(Lazy.MH_castReference, convClass, names[OUT_CALL]);
 329             } else {
 330                 MethodHandle fn = (MethodHandle) convSpec;
 331                 if (fn.type().parameterCount() == 0)
 332                     conv = new Name(fn);  // don't pass retval to void conversion
 333                 else
 334                     conv = new Name(fn, names[OUT_CALL]);
 335             }
 336             assert(names[RETURN_CONV] == null);
 337             names[RETURN_CONV] = conv;
 338             assert(RETURN_CONV == names.length-1);
 339         }
 340 
 341         LambdaForm form = new LambdaForm("convert", lambdaType.parameterCount(), names, RESULT);
 342         return SimpleMethodHandle.make(srcType, form);
 343     }
 344 
 345     /**
 346      * Identity function, with reference cast.
 347      * @param t an arbitrary reference type
 348      * @param x an arbitrary reference value
 349      * @return the same value x
 350      */
 351     @ForceInline
 352     @SuppressWarnings("unchecked")
 353     static <T,U> T castReference(Class<? extends T> t, U x) {
 354         // inlined Class.cast because we can't ForceInline it
 355         if (x != null && !t.isInstance(x))
 356             throw newClassCastException(t, x);
 357         return (T) x;
 358     }
 359 
 360     private static ClassCastException newClassCastException(Class<?> t, Object obj) {
 361         return new ClassCastException("Cannot cast " + obj.getClass().getName() + " to " + t.getName());
 362     }
 363 
 364     static Object[] computeValueConversions(MethodType srcType, MethodType dstType,
 365                                             boolean strict, boolean monobox) {
 366         final int INARG_COUNT = srcType.parameterCount();
 367         Object[] convSpecs = new Object[INARG_COUNT+1];
 368         for (int i = 0; i <= INARG_COUNT; i++) {
 369             boolean isRet = (i == INARG_COUNT);
 370             Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);
 371             Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);
 372             if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {
 373                 convSpecs[i] = valueConversion(src, dst, strict, monobox);
 374             }
 375         }
 376         return convSpecs;
 377     }
 378     static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
 379                                             boolean strict) {
 380         return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);
 381     }
 382 
 383     /**
 384      * Find a conversion function from the given source to the given destination.
 385      * This conversion function will be used as a LF NamedFunction.
 386      * Return a Class object if a simple cast is needed.
 387      * Return void.class if void is involved.
 388      */
 389     static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {
 390         assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility
 391         if (dst == void.class)
 392             return dst;
 393         MethodHandle fn;
 394         if (src.isPrimitive()) {
 395             if (src == void.class) {
 396                 return void.class;  // caller must recognize this specially
 397             } else if (dst.isPrimitive()) {
 398                 // Examples: int->byte, byte->int, boolean->int (!strict)
 399                 fn = ValueConversions.convertPrimitive(src, dst);
 400             } else {
 401                 // Examples: int->Integer, boolean->Object, float->Number
 402                 Wrapper wsrc = Wrapper.forPrimitiveType(src);
 403                 fn = ValueConversions.boxExact(wsrc);
 404                 assert(fn.type().parameterType(0) == wsrc.primitiveType());
 405                 assert(fn.type().returnType() == wsrc.wrapperType());
 406                 if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {
 407                     // Corner case, such as int->Long, which will probably fail.
 408                     MethodType mt = MethodType.methodType(dst, src);
 409                     if (strict)
 410                         fn = fn.asType(mt);
 411                     else
 412                         fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);
 413                 }
 414             }
 415         } else if (dst.isPrimitive()) {
 416             Wrapper wdst = Wrapper.forPrimitiveType(dst);
 417             if (monobox || src == wdst.wrapperType()) {
 418                 // Use a strongly-typed unboxer, if possible.
 419                 fn = ValueConversions.unboxExact(wdst, strict);
 420             } else {
 421                 // Examples:  Object->int, Number->int, Comparable->int, Byte->int
 422                 // must include additional conversions
 423                 // src must be examined at runtime, to detect Byte, Character, etc.
 424                 fn = (strict
 425                         ? ValueConversions.unboxWiden(wdst)
 426                         : ValueConversions.unboxCast(wdst));
 427             }
 428         } else {
 429             // Simple reference conversion.
 430             // Note:  Do not check for a class hierarchy relation
 431             // between src and dst.  In all cases a 'null' argument
 432             // will pass the cast conversion.
 433             return dst;
 434         }
 435         assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);
 436         return fn;
 437     }
 438 
 439     static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {
 440         MethodType type = target.type();
 441         int last = type.parameterCount() - 1;
 442         if (type.parameterType(last) != arrayType)
 443             target = target.asType(type.changeParameterType(last, arrayType));
 444         target = target.asFixedArity();  // make sure this attribute is turned off
 445         return new AsVarargsCollector(target, arrayType);
 446     }
 447 
 448     private static final class AsVarargsCollector extends DelegatingMethodHandle {
 449         private final MethodHandle target;
 450         private final Class<?> arrayType;
 451         private @Stable MethodHandle asCollectorCache;
 452 
 453         AsVarargsCollector(MethodHandle target, Class<?> arrayType) {
 454             this(target.type(), target, arrayType);
 455         }
 456         AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {
 457             super(type, target);
 458             this.target = target;
 459             this.arrayType = arrayType;
 460             this.asCollectorCache = target.asCollector(arrayType, 0);
 461         }
 462 
 463         @Override
 464         public boolean isVarargsCollector() {
 465             return true;
 466         }
 467 
 468         @Override
 469         protected MethodHandle getTarget() {
 470             return target;
 471         }
 472 
 473         @Override
 474         public MethodHandle asFixedArity() {
 475             return target;
 476         }
 477 
 478         @Override
 479         MethodHandle setVarargs(MemberName member) {
 480             if (member.isVarargs())  return this;
 481             return asFixedArity();
 482         }
 483 
 484         @Override
 485         public MethodHandle asTypeUncached(MethodType newType) {
 486             MethodType type = this.type();
 487             int collectArg = type.parameterCount() - 1;
 488             int newArity = newType.parameterCount();
 489             if (newArity == collectArg+1 &&
 490                 type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {
 491                 // if arity and trailing parameter are compatible, do normal thing
 492                 return asTypeCache = asFixedArity().asType(newType);
 493             }
 494             // check cache
 495             MethodHandle acc = asCollectorCache;
 496             if (acc != null && acc.type().parameterCount() == newArity)
 497                 return asTypeCache = acc.asType(newType);
 498             // build and cache a collector
 499             int arrayLength = newArity - collectArg;
 500             MethodHandle collector;
 501             try {
 502                 collector = asFixedArity().asCollector(arrayType, arrayLength);
 503                 assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;
 504             } catch (IllegalArgumentException ex) {
 505                 throw new WrongMethodTypeException("cannot build collector", ex);
 506             }
 507             asCollectorCache = collector;
 508             return asTypeCache = collector.asType(newType);
 509         }
 510 
 511         @Override
 512         boolean viewAsTypeChecks(MethodType newType, boolean strict) {
 513             super.viewAsTypeChecks(newType, true);
 514             if (strict) return true;
 515             // extra assertion for non-strict checks:
 516             assert (type().lastParameterType().getComponentType()
 517                     .isAssignableFrom(
 518                             newType.lastParameterType().getComponentType()))
 519                     : Arrays.asList(this, newType);
 520             return true;
 521         }
 522     }
 523 
 524     /** Factory method:  Spread selected argument. */
 525     static MethodHandle makeSpreadArguments(MethodHandle target,
 526                                             Class<?> spreadArgType, int spreadArgPos, int spreadArgCount) {
 527         MethodType targetType = target.type();
 528 
 529         for (int i = 0; i < spreadArgCount; i++) {
 530             Class<?> arg = VerifyType.spreadArgElementType(spreadArgType, i);
 531             if (arg == null)  arg = Object.class;
 532             targetType = targetType.changeParameterType(spreadArgPos + i, arg);
 533         }
 534         target = target.asType(targetType);
 535 
 536         MethodType srcType = targetType
 537                 .replaceParameterTypes(spreadArgPos, spreadArgPos + spreadArgCount, spreadArgType);
 538         // Now build a LambdaForm.
 539         MethodType lambdaType = srcType.invokerType();
 540         Name[] names = arguments(spreadArgCount + 2, lambdaType);
 541         int nameCursor = lambdaType.parameterCount();
 542         int[] indexes = new int[targetType.parameterCount()];
 543 
 544         for (int i = 0, argIndex = 1; i < targetType.parameterCount() + 1; i++, argIndex++) {
 545             Class<?> src = lambdaType.parameterType(i);
 546             if (i == spreadArgPos) {
 547                 // Spread the array.
 548                 MethodHandle aload = MethodHandles.arrayElementGetter(spreadArgType);
 549                 Name array = names[argIndex];
 550                 names[nameCursor++] = new Name(Lazy.NF_checkSpreadArgument, array, spreadArgCount);
 551                 for (int j = 0; j < spreadArgCount; i++, j++) {
 552                     indexes[i] = nameCursor;
 553                     names[nameCursor++] = new Name(aload, array, j);
 554                 }
 555             } else if (i < indexes.length) {
 556                 indexes[i] = argIndex;
 557             }
 558         }
 559         assert(nameCursor == names.length-1);  // leave room for the final call
 560 
 561         // Build argument array for the call.
 562         Name[] targetArgs = new Name[targetType.parameterCount()];
 563         for (int i = 0; i < targetType.parameterCount(); i++) {
 564             int idx = indexes[i];
 565             targetArgs[i] = names[idx];
 566         }
 567         names[names.length - 1] = new Name(target, (Object[]) targetArgs);
 568 
 569         LambdaForm form = new LambdaForm("spread", lambdaType.parameterCount(), names);
 570         return SimpleMethodHandle.make(srcType, form);
 571     }
 572 
 573     static void checkSpreadArgument(Object av, int n) {
 574         if (av == null) {
 575             if (n == 0)  return;
 576         } else if (av instanceof Object[]) {
 577             int len = ((Object[])av).length;
 578             if (len == n)  return;
 579         } else {
 580             int len = java.lang.reflect.Array.getLength(av);
 581             if (len == n)  return;
 582         }
 583         // fall through to error:
 584         throw newIllegalArgumentException("array is not of length "+n);
 585     }
 586 
 587     /**
 588      * Pre-initialized NamedFunctions for bootstrapping purposes.
 589      * Factored in an inner class to delay initialization until first usage.
 590      */
 591     static class Lazy {
 592         private static final Class<?> MHI = MethodHandleImpl.class;
 593 
 594         private static final MethodHandle[] ARRAYS;
 595         private static final MethodHandle[] FILL_ARRAYS;
 596 
 597         static final NamedFunction NF_checkSpreadArgument;
 598         static final NamedFunction NF_guardWithCatch;
 599         static final NamedFunction NF_throwException;
 600         static final NamedFunction NF_profileBoolean;
 601 
 602         static final MethodHandle MH_castReference;
 603         static final MethodHandle MH_selectAlternative;
 604         static final MethodHandle MH_copyAsPrimitiveArray;
 605         static final MethodHandle MH_fillNewTypedArray;
 606         static final MethodHandle MH_fillNewArray;
 607         static final MethodHandle MH_arrayIdentity;
 608 
 609         static {
 610             ARRAYS      = makeArrays();
 611             FILL_ARRAYS = makeFillArrays();
 612 
 613             try {
 614                 NF_checkSpreadArgument = new NamedFunction(MHI.getDeclaredMethod("checkSpreadArgument", Object.class, int.class));
 615                 NF_guardWithCatch      = new NamedFunction(MHI.getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,
 616                                                                                  MethodHandle.class, Object[].class));
 617                 NF_throwException      = new NamedFunction(MHI.getDeclaredMethod("throwException", Throwable.class));
 618                 NF_profileBoolean      = new NamedFunction(MHI.getDeclaredMethod("profileBoolean", boolean.class, int[].class));
 619 
 620                 NF_checkSpreadArgument.resolve();
 621                 NF_guardWithCatch.resolve();
 622                 NF_throwException.resolve();
 623                 NF_profileBoolean.resolve();
 624 
 625                 MH_castReference        = IMPL_LOOKUP.findStatic(MHI, "castReference",
 626                                             MethodType.methodType(Object.class, Class.class, Object.class));
 627                 MH_copyAsPrimitiveArray = IMPL_LOOKUP.findStatic(MHI, "copyAsPrimitiveArray",
 628                                             MethodType.methodType(Object.class, Wrapper.class, Object[].class));
 629                 MH_arrayIdentity        = IMPL_LOOKUP.findStatic(MHI, "identity",
 630                                             MethodType.methodType(Object[].class, Object[].class));
 631                 MH_fillNewArray         = IMPL_LOOKUP.findStatic(MHI, "fillNewArray",
 632                                             MethodType.methodType(Object[].class, Integer.class, Object[].class));
 633                 MH_fillNewTypedArray    = IMPL_LOOKUP.findStatic(MHI, "fillNewTypedArray",
 634                                             MethodType.methodType(Object[].class, Object[].class, Integer.class, Object[].class));
 635 
 636                 MH_selectAlternative    = makeIntrinsic(
 637                         IMPL_LOOKUP.findStatic(MHI, "selectAlternative",
 638                                 MethodType.methodType(MethodHandle.class, boolean.class, MethodHandle.class, MethodHandle.class)),
 639                         Intrinsic.SELECT_ALTERNATIVE);
 640             } catch (ReflectiveOperationException ex) {
 641                 throw newInternalError(ex);
 642             }
 643         }
 644     }
 645 
 646     /** Factory method:  Collect or filter selected argument(s). */
 647     static MethodHandle makeCollectArguments(MethodHandle target,
 648                 MethodHandle collector, int collectArgPos, boolean retainOriginalArgs) {
 649         MethodType targetType = target.type();          // (a..., c, [b...])=>r
 650         MethodType collectorType = collector.type();    // (b...)=>c
 651         int collectArgCount = collectorType.parameterCount();
 652         Class<?> collectValType = collectorType.returnType();
 653         int collectValCount = (collectValType == void.class ? 0 : 1);
 654         MethodType srcType = targetType                 // (a..., [b...])=>r
 655                 .dropParameterTypes(collectArgPos, collectArgPos+collectValCount);
 656         if (!retainOriginalArgs) {                      // (a..., b...)=>r
 657             srcType = srcType.insertParameterTypes(collectArgPos, collectorType.parameterList());
 658         }
 659         // in  arglist: [0: ...keep1 | cpos: collect...  | cpos+cacount: keep2... ]
 660         // out arglist: [0: ...keep1 | cpos: collectVal? | cpos+cvcount: keep2... ]
 661         // out(retain): [0: ...keep1 | cpos: cV? coll... | cpos+cvc+cac: keep2... ]
 662 
 663         // Now build a LambdaForm.
 664         MethodType lambdaType = srcType.invokerType();
 665         Name[] names = arguments(2, lambdaType);
 666         final int collectNamePos = names.length - 2;
 667         final int targetNamePos  = names.length - 1;
 668 
 669         Name[] collectorArgs = Arrays.copyOfRange(names, 1 + collectArgPos, 1 + collectArgPos + collectArgCount);
 670         names[collectNamePos] = new Name(collector, (Object[]) collectorArgs);
 671 
 672         // Build argument array for the target.
 673         // Incoming LF args to copy are: [ (mh) headArgs collectArgs tailArgs ].
 674         // Output argument array is [ headArgs (collectVal)? (collectArgs)? tailArgs ].
 675         Name[] targetArgs = new Name[targetType.parameterCount()];
 676         int inputArgPos  = 1;  // incoming LF args to copy to target
 677         int targetArgPos = 0;  // fill pointer for targetArgs
 678         int chunk = collectArgPos;  // |headArgs|
 679         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 680         inputArgPos  += chunk;
 681         targetArgPos += chunk;
 682         if (collectValType != void.class) {
 683             targetArgs[targetArgPos++] = names[collectNamePos];
 684         }
 685         chunk = collectArgCount;
 686         if (retainOriginalArgs) {
 687             System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 688             targetArgPos += chunk;   // optionally pass on the collected chunk
 689         }
 690         inputArgPos += chunk;
 691         chunk = targetArgs.length - targetArgPos;  // all the rest
 692         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 693         assert(inputArgPos + chunk == collectNamePos);  // use of rest of input args also
 694         names[targetNamePos] = new Name(target, (Object[]) targetArgs);
 695 
 696         LambdaForm form = new LambdaForm("collect", lambdaType.parameterCount(), names);
 697         return SimpleMethodHandle.make(srcType, form);
 698     }
 699 
 700     @LambdaForm.Hidden
 701     static
 702     MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {
 703         if (testResult) {
 704             return target;
 705         } else {
 706             return fallback;
 707         }
 708     }
 709 
 710     // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.
 711     @LambdaForm.Hidden
 712     static
 713     boolean profileBoolean(boolean result, int[] counters) {
 714         // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.
 715         int idx = result ? 1 : 0;
 716         try {
 717             counters[idx] = Math.addExact(counters[idx], 1);
 718         } catch (ArithmeticException e) {
 719             // Avoid continuous overflow by halving the problematic count.
 720             counters[idx] = counters[idx] / 2;
 721         }
 722         return result;
 723     }
 724 
 725     static
 726     MethodHandle makeGuardWithTest(MethodHandle test,
 727                                    MethodHandle target,
 728                                    MethodHandle fallback) {
 729         MethodType type = target.type();
 730         assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));
 731         MethodType basicType = type.basicType();
 732         LambdaForm form = makeGuardWithTestForm(basicType);
 733         BoundMethodHandle mh;
 734         try {
 735             if (PROFILE_GWT) {
 736                 int[] counts = new int[2];
 737                 mh = (BoundMethodHandle)
 738                         BoundMethodHandle.speciesData_LLLL().constructor().invokeBasic(type, form,
 739                                 (Object) test, (Object) profile(target), (Object) profile(fallback), counts);
 740             } else {
 741                 mh = (BoundMethodHandle)
 742                         BoundMethodHandle.speciesData_LLL().constructor().invokeBasic(type, form,
 743                                 (Object) test, (Object) profile(target), (Object) profile(fallback));
 744             }
 745         } catch (Throwable ex) {
 746             throw uncaughtException(ex);
 747         }
 748         assert(mh.type() == type);
 749         return mh;
 750     }
 751 
 752 
 753     static
 754     MethodHandle profile(MethodHandle target) {
 755         if (DONT_INLINE_THRESHOLD >= 0) {
 756             return makeBlockInlningWrapper(target);
 757         } else {
 758             return target;
 759         }
 760     }
 761 
 762     /**
 763      * Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.
 764      * Corresponding LambdaForm has @DontInline when compiled into bytecode.
 765      */
 766     static
 767     MethodHandle makeBlockInlningWrapper(MethodHandle target) {
 768         LambdaForm lform = PRODUCE_BLOCK_INLINING_FORM.apply(target);
 769         return new CountingWrapper(target, lform,
 770                 PRODUCE_BLOCK_INLINING_FORM, PRODUCE_REINVOKER_FORM,
 771                                    DONT_INLINE_THRESHOLD);
 772     }
 773 
 774     /** Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle */
 775     private static final Function<MethodHandle, LambdaForm> PRODUCE_BLOCK_INLINING_FORM = new Function<MethodHandle, LambdaForm>() {
 776         @Override
 777         public LambdaForm apply(MethodHandle target) {
 778             return DelegatingMethodHandle.makeReinvokerForm(target,
 779                                MethodTypeForm.LF_DELEGATE_BLOCK_INLINING, CountingWrapper.class, "reinvoker.dontInline", false,
 780                                DelegatingMethodHandle.NF_getTarget, CountingWrapper.NF_maybeStopCounting);
 781         }
 782     };
 783 
 784     /** Constructs simple reinvoker lambda form for a particular method handle */
 785     private static final Function<MethodHandle, LambdaForm> PRODUCE_REINVOKER_FORM = new Function<MethodHandle, LambdaForm>() {
 786         @Override
 787         public LambdaForm apply(MethodHandle target) {
 788             return DelegatingMethodHandle.makeReinvokerForm(target,
 789                     MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, DelegatingMethodHandle.NF_getTarget);
 790         }
 791     };
 792 
 793     /**
 794      * Counting method handle. It has 2 states: counting and non-counting.
 795      * It is in counting state for the first n invocations and then transitions to non-counting state.
 796      * Behavior in counting and non-counting states is determined by lambda forms produced by
 797      * countingFormProducer & nonCountingFormProducer respectively.
 798      */
 799     static class CountingWrapper extends DelegatingMethodHandle {
 800         private final MethodHandle target;
 801         private int count;
 802         private Function<MethodHandle, LambdaForm> countingFormProducer;
 803         private Function<MethodHandle, LambdaForm> nonCountingFormProducer;
 804         private volatile boolean isCounting;
 805 
 806         private CountingWrapper(MethodHandle target, LambdaForm lform,
 807                                 Function<MethodHandle, LambdaForm> countingFromProducer,
 808                                 Function<MethodHandle, LambdaForm> nonCountingFormProducer,
 809                                 int count) {
 810             super(target.type(), lform);
 811             this.target = target;
 812             this.count = count;
 813             this.countingFormProducer = countingFromProducer;
 814             this.nonCountingFormProducer = nonCountingFormProducer;
 815             this.isCounting = (count > 0);
 816         }
 817 
 818         @Hidden
 819         @Override
 820         protected MethodHandle getTarget() {
 821             return target;
 822         }
 823 
 824         @Override
 825         public MethodHandle asTypeUncached(MethodType newType) {
 826             MethodHandle newTarget = target.asType(newType);
 827             MethodHandle wrapper;
 828             if (isCounting) {
 829                 LambdaForm lform;
 830                 lform = countingFormProducer.apply(target);
 831                 wrapper = new CountingWrapper(newTarget, lform, countingFormProducer, nonCountingFormProducer, DONT_INLINE_THRESHOLD);
 832             } else {
 833                 wrapper = newTarget; // no need for a counting wrapper anymore
 834             }
 835             return (asTypeCache = wrapper);
 836         }
 837 
 838         boolean countDown() {
 839             if (count <= 0) {
 840                 // Try to limit number of updates. MethodHandle.updateForm() doesn't guarantee LF update visibility.
 841                 if (isCounting) {
 842                     isCounting = false;
 843                     return true;
 844                 } else {
 845                     return false;
 846                 }
 847             } else {
 848                 --count;
 849                 return false;
 850             }
 851         }
 852 
 853         @Hidden
 854         static void maybeStopCounting(Object o1) {
 855              CountingWrapper wrapper = (CountingWrapper) o1;
 856              if (wrapper.countDown()) {
 857                  // Reached invocation threshold. Replace counting behavior with a non-counting one.
 858                  LambdaForm lform = wrapper.nonCountingFormProducer.apply(wrapper.target);
 859                  lform.compileToBytecode(); // speed up warmup by avoiding LF interpretation again after transition
 860                  wrapper.updateForm(lform);
 861              }
 862         }
 863 
 864         static final NamedFunction NF_maybeStopCounting;
 865         static {
 866             Class<?> THIS_CLASS = CountingWrapper.class;
 867             try {
 868                 NF_maybeStopCounting = new NamedFunction(THIS_CLASS.getDeclaredMethod("maybeStopCounting", Object.class));
 869             } catch (ReflectiveOperationException ex) {
 870                 throw newInternalError(ex);
 871             }
 872         }
 873     }
 874 
 875     static
 876     LambdaForm makeGuardWithTestForm(MethodType basicType) {
 877         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWT);
 878         if (lform != null)  return lform;
 879         final int THIS_MH      = 0;  // the BMH_LLL
 880         final int ARG_BASE     = 1;  // start of incoming arguments
 881         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
 882         int nameCursor = ARG_LIMIT;
 883         final int GET_TEST     = nameCursor++;
 884         final int GET_TARGET   = nameCursor++;
 885         final int GET_FALLBACK = nameCursor++;
 886         final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;
 887         final int CALL_TEST    = nameCursor++;
 888         final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;
 889         final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST
 890         final int SELECT_ALT   = nameCursor++;
 891         final int CALL_TARGET  = nameCursor++;
 892         assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative
 893 
 894         MethodType lambdaType = basicType.invokerType();
 895         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 896 
 897         BoundMethodHandle.SpeciesData data =
 898                 (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()
 899                                      : BoundMethodHandle.speciesData_LLL();
 900         names[THIS_MH] = names[THIS_MH].withConstraint(data);
 901         names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);
 902         names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);
 903         names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);
 904         if (GET_COUNTERS != -1) {
 905             names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);
 906         }
 907         Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);
 908 
 909         // call test
 910         MethodType testType = basicType.changeReturnType(boolean.class).basicType();
 911         invokeArgs[0] = names[GET_TEST];
 912         names[CALL_TEST] = new Name(testType, invokeArgs);
 913 
 914         // profile branch
 915         if (PROFILE != -1) {
 916             names[PROFILE] = new Name(Lazy.NF_profileBoolean, names[CALL_TEST], names[GET_COUNTERS]);
 917         }
 918         // call selectAlternative
 919         names[SELECT_ALT] = new Name(Lazy.MH_selectAlternative, names[TEST], names[GET_TARGET], names[GET_FALLBACK]);
 920 
 921         // call target or fallback
 922         invokeArgs[0] = names[SELECT_ALT];
 923         names[CALL_TARGET] = new Name(basicType, invokeArgs);
 924 
 925         lform = new LambdaForm("guard", lambdaType.parameterCount(), names, /*forceInline=*/true);
 926 
 927         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);
 928     }
 929 
 930     /**
 931      * The LambdaForm shape for catchException combinator is the following:
 932      * <blockquote><pre>{@code
 933      *  guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{
 934      *    t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);
 935      *    t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);
 936      *    t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);
 937      *    t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);
 938      *    t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);
 939      *    t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);
 940      *    t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);
 941      *   t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}
 942      * }</pre></blockquote>
 943      *
 944      * argL0 and argL2 are target and catcher method handles. argL1 is exception class.
 945      * argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]
 946      * (ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).
 947      *
 948      * Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms
 949      * among catchException combinators with the same basic type.
 950      */
 951     private static LambdaForm makeGuardWithCatchForm(MethodType basicType) {
 952         MethodType lambdaType = basicType.invokerType();
 953 
 954         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWC);
 955         if (lform != null) {
 956             return lform;
 957         }
 958         final int THIS_MH      = 0;  // the BMH_LLLLL
 959         final int ARG_BASE     = 1;  // start of incoming arguments
 960         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
 961 
 962         int nameCursor = ARG_LIMIT;
 963         final int GET_TARGET       = nameCursor++;
 964         final int GET_CLASS        = nameCursor++;
 965         final int GET_CATCHER      = nameCursor++;
 966         final int GET_COLLECT_ARGS = nameCursor++;
 967         final int GET_UNBOX_RESULT = nameCursor++;
 968         final int BOXED_ARGS       = nameCursor++;
 969         final int TRY_CATCH        = nameCursor++;
 970         final int UNBOX_RESULT     = nameCursor++;
 971 
 972         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 973 
 974         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
 975         names[THIS_MH]          = names[THIS_MH].withConstraint(data);
 976         names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
 977         names[GET_CLASS]        = new Name(data.getterFunction(1), names[THIS_MH]);
 978         names[GET_CATCHER]      = new Name(data.getterFunction(2), names[THIS_MH]);
 979         names[GET_COLLECT_ARGS] = new Name(data.getterFunction(3), names[THIS_MH]);
 980         names[GET_UNBOX_RESULT] = new Name(data.getterFunction(4), names[THIS_MH]);
 981 
 982         // FIXME: rework argument boxing/result unboxing logic for LF interpretation
 983 
 984         // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
 985         MethodType collectArgsType = basicType.changeReturnType(Object.class);
 986         MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
 987         Object[] args = new Object[invokeBasic.type().parameterCount()];
 988         args[0] = names[GET_COLLECT_ARGS];
 989         System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
 990         names[BOXED_ARGS] = new Name(makeIntrinsic(invokeBasic, Intrinsic.GUARD_WITH_CATCH), args);
 991 
 992         // t_{i+1}:L=MethodHandleImpl.guardWithCatch(target:L,exType:L,catcher:L,t_{i}:L);
 993         Object[] gwcArgs = new Object[] {names[GET_TARGET], names[GET_CLASS], names[GET_CATCHER], names[BOXED_ARGS]};
 994         names[TRY_CATCH] = new Name(Lazy.NF_guardWithCatch, gwcArgs);
 995 
 996         // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
 997         MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
 998         Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_CATCH]};
 999         names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);
1000 
1001         lform = new LambdaForm("guardWithCatch", lambdaType.parameterCount(), names);
1002 
1003         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
1004     }
1005 
1006     static
1007     MethodHandle makeGuardWithCatch(MethodHandle target,
1008                                     Class<? extends Throwable> exType,
1009                                     MethodHandle catcher) {
1010         MethodType type = target.type();
1011         LambdaForm form = makeGuardWithCatchForm(type.basicType());
1012 
1013         // Prepare auxiliary method handles used during LambdaForm interpretation.
1014         // Box arguments and wrap them into Object[]: ValueConversions.array().
1015         MethodType varargsType = type.changeReturnType(Object[].class);
1016         MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
1017         // Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore().
1018         MethodHandle unboxResult;
1019         Class<?> rtype = type.returnType();
1020         if (rtype.isPrimitive()) {
1021             if (rtype == void.class) {
1022                 unboxResult = ValueConversions.ignore();
1023             } else {
1024                 Wrapper w = Wrapper.forPrimitiveType(type.returnType());
1025                 unboxResult = ValueConversions.unboxExact(w);
1026             }
1027         } else {
1028             unboxResult = MethodHandles.identity(Object.class);
1029         }
1030 
1031         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
1032         BoundMethodHandle mh;
1033         try {
1034             mh = (BoundMethodHandle)
1035                     data.constructor().invokeBasic(type, form, (Object) target, (Object) exType, (Object) catcher,
1036                                                    (Object) collectArgs, (Object) unboxResult);
1037         } catch (Throwable ex) {
1038             throw uncaughtException(ex);
1039         }
1040         assert(mh.type() == type);
1041         return mh;
1042     }
1043 
1044     /**
1045      * Intrinsified during LambdaForm compilation
1046      * (see {@link InvokerBytecodeGenerator#emitGuardWithCatch emitGuardWithCatch}).
1047      */
1048     @LambdaForm.Hidden
1049     static Object guardWithCatch(MethodHandle target, Class<? extends Throwable> exType, MethodHandle catcher,
1050                                  Object... av) throws Throwable {
1051         // Use asFixedArity() to avoid unnecessary boxing of last argument for VarargsCollector case.
1052         try {
1053             return target.asFixedArity().invokeWithArguments(av);
1054         } catch (Throwable t) {
1055             if (!exType.isInstance(t)) throw t;
1056             return catcher.asFixedArity().invokeWithArguments(prepend(t, av));
1057         }
1058     }
1059 
1060     /** Prepend an element {@code elem} to an {@code array}. */
1061     @LambdaForm.Hidden
1062     private static Object[] prepend(Object elem, Object[] array) {
1063         Object[] newArray = new Object[array.length+1];
1064         newArray[0] = elem;
1065         System.arraycopy(array, 0, newArray, 1, array.length);
1066         return newArray;
1067     }
1068 
1069     static
1070     MethodHandle throwException(MethodType type) {
1071         assert(Throwable.class.isAssignableFrom(type.parameterType(0)));
1072         int arity = type.parameterCount();
1073         if (arity > 1) {
1074             MethodHandle mh = throwException(type.dropParameterTypes(1, arity));
1075             mh = MethodHandles.dropArguments(mh, 1, type.parameterList().subList(1, arity));
1076             return mh;
1077         }
1078         return makePairwiseConvert(Lazy.NF_throwException.resolvedHandle(), type, false, true);
1079     }
1080 
1081     static <T extends Throwable> Empty throwException(T t) throws T { throw t; }
1082 
1083     static MethodHandle[] FAKE_METHOD_HANDLE_INVOKE = new MethodHandle[2];
1084     static MethodHandle fakeMethodHandleInvoke(MemberName method) {
1085         int idx;
1086         assert(method.isMethodHandleInvoke());
1087         switch (method.getName()) {
1088         case "invoke":       idx = 0; break;
1089         case "invokeExact":  idx = 1; break;
1090         default:             throw new InternalError(method.getName());
1091         }
1092         MethodHandle mh = FAKE_METHOD_HANDLE_INVOKE[idx];
1093         if (mh != null)  return mh;
1094         MethodType type = MethodType.methodType(Object.class, UnsupportedOperationException.class,
1095                                                 MethodHandle.class, Object[].class);
1096         mh = throwException(type);
1097         mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke MethodHandle"));
1098         if (!method.getInvocationType().equals(mh.type()))
1099             throw new InternalError(method.toString());
1100         mh = mh.withInternalMemberName(method, false);
1101         mh = mh.asVarargsCollector(Object[].class);
1102         assert(method.isVarargs());
1103         FAKE_METHOD_HANDLE_INVOKE[idx] = mh;
1104         return mh;
1105     }
1106 
1107     /**
1108      * Create an alias for the method handle which, when called,
1109      * appears to be called from the same class loader and protection domain
1110      * as hostClass.
1111      * This is an expensive no-op unless the method which is called
1112      * is sensitive to its caller.  A small number of system methods
1113      * are in this category, including Class.forName and Method.invoke.
1114      */
1115     static
1116     MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1117         return BindCaller.bindCaller(mh, hostClass);
1118     }
1119 
1120     // Put the whole mess into its own nested class.
1121     // That way we can lazily load the code and set up the constants.
1122     private static class BindCaller {
1123         static
1124         MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1125             // Do not use this function to inject calls into system classes.
1126             if (hostClass == null
1127                 ||    (hostClass.isArray() ||
1128                        hostClass.isPrimitive() ||
1129                        hostClass.getName().startsWith("java.") ||
1130                        hostClass.getName().startsWith("sun."))) {
1131                 throw new InternalError();  // does not happen, and should not anyway
1132             }
1133             // For simplicity, convert mh to a varargs-like method.
1134             MethodHandle vamh = prepareForInvoker(mh);
1135             // Cache the result of makeInjectedInvoker once per argument class.
1136             MethodHandle bccInvoker = CV_makeInjectedInvoker.get(hostClass);
1137             return restoreToType(bccInvoker.bindTo(vamh), mh, hostClass);
1138         }
1139 
1140         private static MethodHandle makeInjectedInvoker(Class<?> hostClass) {
1141             Class<?> bcc = UNSAFE.defineAnonymousClass(hostClass, T_BYTES, null);
1142             if (hostClass.getClassLoader() != bcc.getClassLoader())
1143                 throw new InternalError(hostClass.getName()+" (CL)");
1144             try {
1145                 if (hostClass.getProtectionDomain() != bcc.getProtectionDomain())
1146                     throw new InternalError(hostClass.getName()+" (PD)");
1147             } catch (SecurityException ex) {
1148                 // Self-check was blocked by security manager.  This is OK.
1149                 // In fact the whole try body could be turned into an assertion.
1150             }
1151             try {
1152                 MethodHandle init = IMPL_LOOKUP.findStatic(bcc, "init", MethodType.methodType(void.class));
1153                 init.invokeExact();  // force initialization of the class
1154             } catch (Throwable ex) {
1155                 throw uncaughtException(ex);
1156             }
1157             MethodHandle bccInvoker;
1158             try {
1159                 MethodType invokerMT = MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1160                 bccInvoker = IMPL_LOOKUP.findStatic(bcc, "invoke_V", invokerMT);
1161             } catch (ReflectiveOperationException ex) {
1162                 throw uncaughtException(ex);
1163             }
1164             // Test the invoker, to ensure that it really injects into the right place.
1165             try {
1166                 MethodHandle vamh = prepareForInvoker(MH_checkCallerClass);
1167                 Object ok = bccInvoker.invokeExact(vamh, new Object[]{hostClass, bcc});
1168             } catch (Throwable ex) {
1169                 throw new InternalError(ex);
1170             }
1171             return bccInvoker;
1172         }
1173         private static ClassValue<MethodHandle> CV_makeInjectedInvoker = new ClassValue<MethodHandle>() {
1174             @Override protected MethodHandle computeValue(Class<?> hostClass) {
1175                 return makeInjectedInvoker(hostClass);
1176             }
1177         };
1178 
1179         // Adapt mh so that it can be called directly from an injected invoker:
1180         private static MethodHandle prepareForInvoker(MethodHandle mh) {
1181             mh = mh.asFixedArity();
1182             MethodType mt = mh.type();
1183             int arity = mt.parameterCount();
1184             MethodHandle vamh = mh.asType(mt.generic());
1185             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1186             vamh = vamh.asSpreader(Object[].class, arity);
1187             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1188             return vamh;
1189         }
1190 
1191         // Undo the adapter effect of prepareForInvoker:
1192         private static MethodHandle restoreToType(MethodHandle vamh,
1193                                                   MethodHandle original,
1194                                                   Class<?> hostClass) {
1195             MethodType type = original.type();
1196             MethodHandle mh = vamh.asCollector(Object[].class, type.parameterCount());
1197             MemberName member = original.internalMemberName();
1198             mh = mh.asType(type);
1199             mh = new WrappedMember(mh, type, member, original.isInvokeSpecial(), hostClass);
1200             return mh;
1201         }
1202 
1203         private static final MethodHandle MH_checkCallerClass;
1204         static {
1205             final Class<?> THIS_CLASS = BindCaller.class;
1206             assert(checkCallerClass(THIS_CLASS, THIS_CLASS));
1207             try {
1208                 MH_checkCallerClass = IMPL_LOOKUP
1209                     .findStatic(THIS_CLASS, "checkCallerClass",
1210                                 MethodType.methodType(boolean.class, Class.class, Class.class));
1211                 assert((boolean) MH_checkCallerClass.invokeExact(THIS_CLASS, THIS_CLASS));
1212             } catch (Throwable ex) {
1213                 throw new InternalError(ex);
1214             }
1215         }
1216 
1217         @CallerSensitive
1218         private static boolean checkCallerClass(Class<?> expected, Class<?> expected2) {
1219             // This method is called via MH_checkCallerClass and so it's
1220             // correct to ask for the immediate caller here.
1221             Class<?> actual = Reflection.getCallerClass();
1222             if (actual != expected && actual != expected2)
1223                 throw new InternalError("found "+actual.getName()+", expected "+expected.getName()
1224                                         +(expected == expected2 ? "" : ", or else "+expected2.getName()));
1225             return true;
1226         }
1227 
1228         private static final byte[] T_BYTES;
1229         static {
1230             final Object[] values = {null};
1231             AccessController.doPrivileged(new PrivilegedAction<Void>() {
1232                     public Void run() {
1233                         try {
1234                             Class<T> tClass = T.class;
1235                             String tName = tClass.getName();
1236                             String tResource = tName.substring(tName.lastIndexOf('.')+1)+".class";
1237                             java.net.URLConnection uconn = tClass.getResource(tResource).openConnection();
1238                             int len = uconn.getContentLength();
1239                             byte[] bytes = new byte[len];
1240                             try (java.io.InputStream str = uconn.getInputStream()) {
1241                                 int nr = str.read(bytes);
1242                                 if (nr != len)  throw new java.io.IOException(tResource);
1243                             }
1244                             values[0] = bytes;
1245                         } catch (java.io.IOException ex) {
1246                             throw new InternalError(ex);
1247                         }
1248                         return null;
1249                     }
1250                 });
1251             T_BYTES = (byte[]) values[0];
1252         }
1253 
1254         // The following class is used as a template for Unsafe.defineAnonymousClass:
1255         private static class T {
1256             static void init() { }  // side effect: initializes this class
1257             static Object invoke_V(MethodHandle vamh, Object[] args) throws Throwable {
1258                 return vamh.invokeExact(args);
1259             }
1260         }
1261     }
1262 
1263 
1264     /** This subclass allows a wrapped method handle to be re-associated with an arbitrary member name. */
1265     private static final class WrappedMember extends DelegatingMethodHandle {
1266         private final MethodHandle target;
1267         private final MemberName member;
1268         private final Class<?> callerClass;
1269         private final boolean isInvokeSpecial;
1270 
1271         private WrappedMember(MethodHandle target, MethodType type,
1272                               MemberName member, boolean isInvokeSpecial,
1273                               Class<?> callerClass) {
1274             super(type, target);
1275             this.target = target;
1276             this.member = member;
1277             this.callerClass = callerClass;
1278             this.isInvokeSpecial = isInvokeSpecial;
1279         }
1280 
1281         @Override
1282         MemberName internalMemberName() {
1283             return member;
1284         }
1285         @Override
1286         Class<?> internalCallerClass() {
1287             return callerClass;
1288         }
1289         @Override
1290         boolean isInvokeSpecial() {
1291             return isInvokeSpecial;
1292         }
1293         @Override
1294         protected MethodHandle getTarget() {
1295             return target;
1296         }
1297         @Override
1298         public MethodHandle asTypeUncached(MethodType newType) {
1299             // This MH is an alias for target, except for the MemberName
1300             // Drop the MemberName if there is any conversion.
1301             return asTypeCache = target.asType(newType);
1302         }
1303     }
1304 
1305     static MethodHandle makeWrappedMember(MethodHandle target, MemberName member, boolean isInvokeSpecial) {
1306         if (member.equals(target.internalMemberName()) && isInvokeSpecial == target.isInvokeSpecial())
1307             return target;
1308         return new WrappedMember(target, target.type(), member, isInvokeSpecial, null);
1309     }
1310 
1311     /** Intrinsic IDs */
1312     /*non-public*/
1313     enum Intrinsic {
1314         SELECT_ALTERNATIVE,
1315         GUARD_WITH_CATCH,
1316         NEW_ARRAY,
1317         ARRAY_LOAD,
1318         ARRAY_STORE,
1319         IDENTITY,
1320         ZERO,
1321         NONE // no intrinsic associated
1322     }
1323 
1324     /** Mark arbitrary method handle as intrinsic.
1325      * InvokerBytecodeGenerator uses this info to produce more efficient bytecode shape. */
1326     private static final class IntrinsicMethodHandle extends DelegatingMethodHandle {
1327         private final MethodHandle target;
1328         private final Intrinsic intrinsicName;
1329 
1330         IntrinsicMethodHandle(MethodHandle target, Intrinsic intrinsicName) {
1331             super(target.type(), target);
1332             this.target = target;
1333             this.intrinsicName = intrinsicName;
1334         }
1335 
1336         @Override
1337         protected MethodHandle getTarget() {
1338             return target;
1339         }
1340 
1341         @Override
1342         Intrinsic intrinsicName() {
1343             return intrinsicName;
1344         }
1345 
1346         @Override
1347         public MethodHandle asTypeUncached(MethodType newType) {
1348             // This MH is an alias for target, except for the intrinsic name
1349             // Drop the name if there is any conversion.
1350             return asTypeCache = target.asType(newType);
1351         }
1352 
1353         @Override
1354         String internalProperties() {
1355             return super.internalProperties() +
1356                     "\n& Intrinsic="+intrinsicName;
1357         }
1358 
1359         @Override
1360         public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
1361             if (intrinsicName == Intrinsic.IDENTITY) {
1362                 MethodType resultType = type().asCollectorType(arrayType, arrayLength);
1363                 MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
1364                 return newArray.asType(resultType);
1365             }
1366             return super.asCollector(arrayType, arrayLength);
1367         }
1368     }
1369 
1370     static MethodHandle makeIntrinsic(MethodHandle target, Intrinsic intrinsicName) {
1371         if (intrinsicName == target.intrinsicName())
1372             return target;
1373         return new IntrinsicMethodHandle(target, intrinsicName);
1374     }
1375 
1376     static MethodHandle makeIntrinsic(MethodType type, LambdaForm form, Intrinsic intrinsicName) {
1377         return new IntrinsicMethodHandle(SimpleMethodHandle.make(type, form), intrinsicName);
1378     }
1379 
1380     /// Collection of multiple arguments.
1381 
1382     private static MethodHandle findCollector(String name, int nargs, Class<?> rtype, Class<?>... ptypes) {
1383         MethodType type = MethodType.genericMethodType(nargs)
1384                 .changeReturnType(rtype)
1385                 .insertParameterTypes(0, ptypes);
1386         try {
1387             return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, name, type);
1388         } catch (ReflectiveOperationException ex) {
1389             return null;
1390         }
1391     }
1392 
1393     private static final Object[] NO_ARGS_ARRAY = {};
1394     private static Object[] makeArray(Object... args) { return args; }
1395     private static Object[] array() { return NO_ARGS_ARRAY; }
1396     private static Object[] array(Object a0)
1397                 { return makeArray(a0); }
1398     private static Object[] array(Object a0, Object a1)
1399                 { return makeArray(a0, a1); }
1400     private static Object[] array(Object a0, Object a1, Object a2)
1401                 { return makeArray(a0, a1, a2); }
1402     private static Object[] array(Object a0, Object a1, Object a2, Object a3)
1403                 { return makeArray(a0, a1, a2, a3); }
1404     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1405                                   Object a4)
1406                 { return makeArray(a0, a1, a2, a3, a4); }
1407     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1408                                   Object a4, Object a5)
1409                 { return makeArray(a0, a1, a2, a3, a4, a5); }
1410     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1411                                   Object a4, Object a5, Object a6)
1412                 { return makeArray(a0, a1, a2, a3, a4, a5, a6); }
1413     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1414                                   Object a4, Object a5, Object a6, Object a7)
1415                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7); }
1416     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1417                                   Object a4, Object a5, Object a6, Object a7,
1418                                   Object a8)
1419                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8); }
1420     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1421                                   Object a4, Object a5, Object a6, Object a7,
1422                                   Object a8, Object a9)
1423                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); }
1424 
1425     private static final int ARRAYS_COUNT = 11;
1426 
1427     private static MethodHandle[] makeArrays() {
1428         MethodHandle[] mhs = new MethodHandle[MAX_ARITY + 1];
1429         for (int i = 0; i < ARRAYS_COUNT; i++) {
1430             MethodHandle mh = findCollector("array", i, Object[].class);
1431             mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1432             mhs[i] = mh;
1433         }
1434         assert(assertArrayMethodCount(mhs));
1435         return mhs;
1436     }
1437 
1438     private static boolean assertArrayMethodCount(MethodHandle[] mhs) {
1439         assert(findCollector("array", ARRAYS_COUNT, Object[].class) == null);
1440         for (int i = 0; i < ARRAYS_COUNT; i++) {
1441             assert(mhs[i] != null);
1442         }
1443         return true;
1444     }
1445 
1446     // filling versions of the above:
1447     // using Integer len instead of int len and no varargs to avoid bootstrapping problems
1448     private static Object[] fillNewArray(Integer len, Object[] /*not ...*/ args) {
1449         Object[] a = new Object[len];
1450         fillWithArguments(a, 0, args);
1451         return a;
1452     }
1453     private static Object[] fillNewTypedArray(Object[] example, Integer len, Object[] /*not ...*/ args) {
1454         Object[] a = Arrays.copyOf(example, len);
1455         assert(a.getClass() != Object[].class);
1456         fillWithArguments(a, 0, args);
1457         return a;
1458     }
1459     private static void fillWithArguments(Object[] a, int pos, Object... args) {
1460         System.arraycopy(args, 0, a, pos, args.length);
1461     }
1462     // using Integer pos instead of int pos to avoid bootstrapping problems
1463     private static Object[] fillArray(Integer pos, Object[] a, Object a0)
1464                 { fillWithArguments(a, pos, a0); return a; }
1465     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1)
1466                 { fillWithArguments(a, pos, a0, a1); return a; }
1467     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2)
1468                 { fillWithArguments(a, pos, a0, a1, a2); return a; }
1469     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3)
1470                 { fillWithArguments(a, pos, a0, a1, a2, a3); return a; }
1471     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1472                                   Object a4)
1473                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4); return a; }
1474     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1475                                   Object a4, Object a5)
1476                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5); return a; }
1477     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1478                                   Object a4, Object a5, Object a6)
1479                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6); return a; }
1480     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1481                                   Object a4, Object a5, Object a6, Object a7)
1482                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7); return a; }
1483     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1484                                   Object a4, Object a5, Object a6, Object a7,
1485                                   Object a8)
1486                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8); return a; }
1487     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1488                                   Object a4, Object a5, Object a6, Object a7,
1489                                   Object a8, Object a9)
1490                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); return a; }
1491 
1492     private static final int FILL_ARRAYS_COUNT = 11; // current number of fillArray methods
1493 
1494     private static MethodHandle[] makeFillArrays() {
1495         MethodHandle[] mhs = new MethodHandle[FILL_ARRAYS_COUNT];
1496         mhs[0] = null;  // there is no empty fill; at least a0 is required
1497         for (int i = 1; i < FILL_ARRAYS_COUNT; i++) {
1498             MethodHandle mh = findCollector("fillArray", i, Object[].class, Integer.class, Object[].class);
1499             mhs[i] = mh;
1500         }
1501         assert(assertFillArrayMethodCount(mhs));
1502         return mhs;
1503     }
1504 
1505     private static boolean assertFillArrayMethodCount(MethodHandle[] mhs) {
1506         assert(findCollector("fillArray", FILL_ARRAYS_COUNT, Object[].class, Integer.class, Object[].class) == null);
1507         for (int i = 1; i < FILL_ARRAYS_COUNT; i++) {
1508             assert(mhs[i] != null);
1509         }
1510         return true;
1511     }
1512 
1513     private static Object copyAsPrimitiveArray(Wrapper w, Object... boxes) {
1514         Object a = w.makeArray(boxes.length);
1515         w.copyArrayUnboxing(boxes, 0, a, 0, boxes.length);
1516         return a;
1517     }
1518 
1519     /** Return a method handle that takes the indicated number of Object
1520      *  arguments and returns an Object array of them, as if for varargs.
1521      */
1522     static MethodHandle varargsArray(int nargs) {
1523         MethodHandle mh = Lazy.ARRAYS[nargs];
1524         if (mh != null)  return mh;
1525         mh = buildVarargsArray(Lazy.MH_fillNewArray, Lazy.MH_arrayIdentity, nargs);
1526         assert(assertCorrectArity(mh, nargs));
1527         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1528         return Lazy.ARRAYS[nargs] = mh;
1529     }
1530 
1531     private static boolean assertCorrectArity(MethodHandle mh, int arity) {
1532         assert(mh.type().parameterCount() == arity) : "arity != "+arity+": "+mh;
1533         return true;
1534     }
1535 
1536     // Array identity function (used as Lazy.MH_arrayIdentity).
1537     static <T> T[] identity(T[] x) {
1538         return x;
1539     }
1540 
1541     private static MethodHandle buildVarargsArray(MethodHandle newArray, MethodHandle finisher, int nargs) {
1542         // Build up the result mh as a sequence of fills like this:
1543         //   finisher(fill(fill(newArrayWA(23,x1..x10),10,x11..x20),20,x21..x23))
1544         // The various fill(_,10*I,___*[J]) are reusable.
1545         int leftLen = Math.min(nargs, LEFT_ARGS);  // absorb some arguments immediately
1546         int rightLen = nargs - leftLen;
1547         MethodHandle leftCollector = newArray.bindTo(nargs);
1548         leftCollector = leftCollector.asCollector(Object[].class, leftLen);
1549         MethodHandle mh = finisher;
1550         if (rightLen > 0) {
1551             MethodHandle rightFiller = fillToRight(LEFT_ARGS + rightLen);
1552             if (mh == Lazy.MH_arrayIdentity)
1553                 mh = rightFiller;
1554             else
1555                 mh = MethodHandles.collectArguments(mh, 0, rightFiller);
1556         }
1557         if (mh == Lazy.MH_arrayIdentity)
1558             mh = leftCollector;
1559         else
1560             mh = MethodHandles.collectArguments(mh, 0, leftCollector);
1561         return mh;
1562     }
1563 
1564     private static final int LEFT_ARGS = FILL_ARRAYS_COUNT - 1;
1565     private static final MethodHandle[] FILL_ARRAY_TO_RIGHT = new MethodHandle[MAX_ARITY+1];
1566     /** fill_array_to_right(N).invoke(a, argL..arg[N-1])
1567      *  fills a[L]..a[N-1] with corresponding arguments,
1568      *  and then returns a.  The value L is a global constant (LEFT_ARGS).
1569      */
1570     private static MethodHandle fillToRight(int nargs) {
1571         MethodHandle filler = FILL_ARRAY_TO_RIGHT[nargs];
1572         if (filler != null)  return filler;
1573         filler = buildFiller(nargs);
1574         assert(assertCorrectArity(filler, nargs - LEFT_ARGS + 1));
1575         return FILL_ARRAY_TO_RIGHT[nargs] = filler;
1576     }
1577     private static MethodHandle buildFiller(int nargs) {
1578         if (nargs <= LEFT_ARGS)
1579             return Lazy.MH_arrayIdentity;  // no args to fill; return the array unchanged
1580         // we need room for both mh and a in mh.invoke(a, arg*[nargs])
1581         final int CHUNK = LEFT_ARGS;
1582         int rightLen = nargs % CHUNK;
1583         int midLen = nargs - rightLen;
1584         if (rightLen == 0) {
1585             midLen = nargs - (rightLen = CHUNK);
1586             if (FILL_ARRAY_TO_RIGHT[midLen] == null) {
1587                 // build some precursors from left to right
1588                 for (int j = LEFT_ARGS % CHUNK; j < midLen; j += CHUNK)
1589                     if (j > LEFT_ARGS)  fillToRight(j);
1590             }
1591         }
1592         if (midLen < LEFT_ARGS) rightLen = nargs - (midLen = LEFT_ARGS);
1593         assert(rightLen > 0);
1594         MethodHandle midFill = fillToRight(midLen);  // recursive fill
1595         MethodHandle rightFill = Lazy.FILL_ARRAYS[rightLen].bindTo(midLen);  // [midLen..nargs-1]
1596         assert(midFill.type().parameterCount()   == 1 + midLen - LEFT_ARGS);
1597         assert(rightFill.type().parameterCount() == 1 + rightLen);
1598 
1599         // Combine the two fills:
1600         //   right(mid(a, x10..x19), x20..x23)
1601         // The final product will look like this:
1602         //   right(mid(newArrayLeft(24, x0..x9), x10..x19), x20..x23)
1603         if (midLen == LEFT_ARGS)
1604             return rightFill;
1605         else
1606             return MethodHandles.collectArguments(rightFill, 0, midFill);
1607     }
1608 
1609     // Type-polymorphic version of varargs maker.
1610     private static final ClassValue<MethodHandle[]> TYPED_COLLECTORS
1611         = new ClassValue<MethodHandle[]>() {
1612             @Override
1613             protected MethodHandle[] computeValue(Class<?> type) {
1614                 return new MethodHandle[256];
1615             }
1616     };
1617 
1618     static final int MAX_JVM_ARITY = 255;  // limit imposed by the JVM
1619 
1620     /** Return a method handle that takes the indicated number of
1621      *  typed arguments and returns an array of them.
1622      *  The type argument is the array type.
1623      */
1624     static MethodHandle varargsArray(Class<?> arrayType, int nargs) {
1625         Class<?> elemType = arrayType.getComponentType();
1626         if (elemType == null)  throw new IllegalArgumentException("not an array: "+arrayType);
1627         // FIXME: Need more special casing and caching here.
1628         if (nargs >= MAX_JVM_ARITY/2 - 1) {
1629             int slots = nargs;
1630             final int MAX_ARRAY_SLOTS = MAX_JVM_ARITY - 1;  // 1 for receiver MH
1631             if (slots <= MAX_ARRAY_SLOTS && elemType.isPrimitive())
1632                 slots *= Wrapper.forPrimitiveType(elemType).stackSlots();
1633             if (slots > MAX_ARRAY_SLOTS)
1634                 throw new IllegalArgumentException("too many arguments: "+arrayType.getSimpleName()+", length "+nargs);
1635         }
1636         if (elemType == Object.class)
1637             return varargsArray(nargs);
1638         // other cases:  primitive arrays, subtypes of Object[]
1639         MethodHandle cache[] = TYPED_COLLECTORS.get(elemType);
1640         MethodHandle mh = nargs < cache.length ? cache[nargs] : null;
1641         if (mh != null)  return mh;
1642         if (nargs == 0) {
1643             Object example = java.lang.reflect.Array.newInstance(arrayType.getComponentType(), 0);
1644             mh = MethodHandles.constant(arrayType, example);
1645         } else if (elemType.isPrimitive()) {
1646             MethodHandle builder = Lazy.MH_fillNewArray;
1647             MethodHandle producer = buildArrayProducer(arrayType);
1648             mh = buildVarargsArray(builder, producer, nargs);
1649         } else {
1650             Class<? extends Object[]> objArrayType = arrayType.asSubclass(Object[].class);
1651             Object[] example = Arrays.copyOf(NO_ARGS_ARRAY, 0, objArrayType);
1652             MethodHandle builder = Lazy.MH_fillNewTypedArray.bindTo(example);
1653             MethodHandle producer = Lazy.MH_arrayIdentity; // must be weakly typed
1654             mh = buildVarargsArray(builder, producer, nargs);
1655         }
1656         mh = mh.asType(MethodType.methodType(arrayType, Collections.<Class<?>>nCopies(nargs, elemType)));
1657         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1658         assert(assertCorrectArity(mh, nargs));
1659         if (nargs < cache.length)
1660             cache[nargs] = mh;
1661         return mh;
1662     }
1663 
1664     private static MethodHandle buildArrayProducer(Class<?> arrayType) {
1665         Class<?> elemType = arrayType.getComponentType();
1666         assert(elemType.isPrimitive());
1667         return Lazy.MH_copyAsPrimitiveArray.bindTo(Wrapper.forPrimitiveType(elemType));
1668     }
1669 }