rev 12327 : 8062543: Replace uses of MethodHandleImpl.castReference with Class.cast

   1 /*
   2  * Copyright (c) 2008, 2015, 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<>() {
  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_cast.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_cast.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_cast, 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_cast, 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     static Object[] computeValueConversions(MethodType srcType, MethodType dstType,
 346                                             boolean strict, boolean monobox) {
 347         final int INARG_COUNT = srcType.parameterCount();
 348         Object[] convSpecs = new Object[INARG_COUNT+1];
 349         for (int i = 0; i <= INARG_COUNT; i++) {
 350             boolean isRet = (i == INARG_COUNT);
 351             Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);
 352             Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);
 353             if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {
 354                 convSpecs[i] = valueConversion(src, dst, strict, monobox);
 355             }
 356         }
 357         return convSpecs;
 358     }
 359     static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
 360                                             boolean strict) {
 361         return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);
 362     }
 363 
 364     /**
 365      * Find a conversion function from the given source to the given destination.
 366      * This conversion function will be used as a LF NamedFunction.
 367      * Return a Class object if a simple cast is needed.
 368      * Return void.class if void is involved.
 369      */
 370     static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {
 371         assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility
 372         if (dst == void.class)
 373             return dst;
 374         MethodHandle fn;
 375         if (src.isPrimitive()) {
 376             if (src == void.class) {
 377                 return void.class;  // caller must recognize this specially
 378             } else if (dst.isPrimitive()) {
 379                 // Examples: int->byte, byte->int, boolean->int (!strict)
 380                 fn = ValueConversions.convertPrimitive(src, dst);
 381             } else {
 382                 // Examples: int->Integer, boolean->Object, float->Number
 383                 Wrapper wsrc = Wrapper.forPrimitiveType(src);
 384                 fn = ValueConversions.boxExact(wsrc);
 385                 assert(fn.type().parameterType(0) == wsrc.primitiveType());
 386                 assert(fn.type().returnType() == wsrc.wrapperType());
 387                 if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {
 388                     // Corner case, such as int->Long, which will probably fail.
 389                     MethodType mt = MethodType.methodType(dst, src);
 390                     if (strict)
 391                         fn = fn.asType(mt);
 392                     else
 393                         fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);
 394                 }
 395             }
 396         } else if (dst.isPrimitive()) {
 397             Wrapper wdst = Wrapper.forPrimitiveType(dst);
 398             if (monobox || src == wdst.wrapperType()) {
 399                 // Use a strongly-typed unboxer, if possible.
 400                 fn = ValueConversions.unboxExact(wdst, strict);
 401             } else {
 402                 // Examples:  Object->int, Number->int, Comparable->int, Byte->int
 403                 // must include additional conversions
 404                 // src must be examined at runtime, to detect Byte, Character, etc.
 405                 fn = (strict
 406                         ? ValueConversions.unboxWiden(wdst)
 407                         : ValueConversions.unboxCast(wdst));
 408             }
 409         } else {
 410             // Simple reference conversion.
 411             // Note:  Do not check for a class hierarchy relation
 412             // between src and dst.  In all cases a 'null' argument
 413             // will pass the cast conversion.
 414             return dst;
 415         }
 416         assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);
 417         return fn;
 418     }
 419 
 420     static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {
 421         MethodType type = target.type();
 422         int last = type.parameterCount() - 1;
 423         if (type.parameterType(last) != arrayType)
 424             target = target.asType(type.changeParameterType(last, arrayType));
 425         target = target.asFixedArity();  // make sure this attribute is turned off
 426         return new AsVarargsCollector(target, arrayType);
 427     }
 428 
 429     private static final class AsVarargsCollector extends DelegatingMethodHandle {
 430         private final MethodHandle target;
 431         private final Class<?> arrayType;
 432         private @Stable MethodHandle asCollectorCache;
 433 
 434         AsVarargsCollector(MethodHandle target, Class<?> arrayType) {
 435             this(target.type(), target, arrayType);
 436         }
 437         AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {
 438             super(type, target);
 439             this.target = target;
 440             this.arrayType = arrayType;
 441             this.asCollectorCache = target.asCollector(arrayType, 0);
 442         }
 443 
 444         @Override
 445         public boolean isVarargsCollector() {
 446             return true;
 447         }
 448 
 449         @Override
 450         protected MethodHandle getTarget() {
 451             return target;
 452         }
 453 
 454         @Override
 455         public MethodHandle asFixedArity() {
 456             return target;
 457         }
 458 
 459         @Override
 460         MethodHandle setVarargs(MemberName member) {
 461             if (member.isVarargs())  return this;
 462             return asFixedArity();
 463         }
 464 
 465         @Override
 466         public MethodHandle asTypeUncached(MethodType newType) {
 467             MethodType type = this.type();
 468             int collectArg = type.parameterCount() - 1;
 469             int newArity = newType.parameterCount();
 470             if (newArity == collectArg+1 &&
 471                 type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {
 472                 // if arity and trailing parameter are compatible, do normal thing
 473                 return asTypeCache = asFixedArity().asType(newType);
 474             }
 475             // check cache
 476             MethodHandle acc = asCollectorCache;
 477             if (acc != null && acc.type().parameterCount() == newArity)
 478                 return asTypeCache = acc.asType(newType);
 479             // build and cache a collector
 480             int arrayLength = newArity - collectArg;
 481             MethodHandle collector;
 482             try {
 483                 collector = asFixedArity().asCollector(arrayType, arrayLength);
 484                 assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;
 485             } catch (IllegalArgumentException ex) {
 486                 throw new WrongMethodTypeException("cannot build collector", ex);
 487             }
 488             asCollectorCache = collector;
 489             return asTypeCache = collector.asType(newType);
 490         }
 491 
 492         @Override
 493         boolean viewAsTypeChecks(MethodType newType, boolean strict) {
 494             super.viewAsTypeChecks(newType, true);
 495             if (strict) return true;
 496             // extra assertion for non-strict checks:
 497             assert (type().lastParameterType().getComponentType()
 498                     .isAssignableFrom(
 499                             newType.lastParameterType().getComponentType()))
 500                     : Arrays.asList(this, newType);
 501             return true;
 502         }
 503     }
 504 
 505     /** Factory method:  Spread selected argument. */
 506     static MethodHandle makeSpreadArguments(MethodHandle target,
 507                                             Class<?> spreadArgType, int spreadArgPos, int spreadArgCount) {
 508         MethodType targetType = target.type();
 509 
 510         for (int i = 0; i < spreadArgCount; i++) {
 511             Class<?> arg = VerifyType.spreadArgElementType(spreadArgType, i);
 512             if (arg == null)  arg = Object.class;
 513             targetType = targetType.changeParameterType(spreadArgPos + i, arg);
 514         }
 515         target = target.asType(targetType);
 516 
 517         MethodType srcType = targetType
 518                 .replaceParameterTypes(spreadArgPos, spreadArgPos + spreadArgCount, spreadArgType);
 519         // Now build a LambdaForm.
 520         MethodType lambdaType = srcType.invokerType();
 521         Name[] names = arguments(spreadArgCount + 2, lambdaType);
 522         int nameCursor = lambdaType.parameterCount();
 523         int[] indexes = new int[targetType.parameterCount()];
 524 
 525         for (int i = 0, argIndex = 1; i < targetType.parameterCount() + 1; i++, argIndex++) {
 526             Class<?> src = lambdaType.parameterType(i);
 527             if (i == spreadArgPos) {
 528                 // Spread the array.
 529                 MethodHandle aload = MethodHandles.arrayElementGetter(spreadArgType);
 530                 Name array = names[argIndex];
 531                 names[nameCursor++] = new Name(Lazy.NF_checkSpreadArgument, array, spreadArgCount);
 532                 for (int j = 0; j < spreadArgCount; i++, j++) {
 533                     indexes[i] = nameCursor;
 534                     names[nameCursor++] = new Name(aload, array, j);
 535                 }
 536             } else if (i < indexes.length) {
 537                 indexes[i] = argIndex;
 538             }
 539         }
 540         assert(nameCursor == names.length-1);  // leave room for the final call
 541 
 542         // Build argument array for the call.
 543         Name[] targetArgs = new Name[targetType.parameterCount()];
 544         for (int i = 0; i < targetType.parameterCount(); i++) {
 545             int idx = indexes[i];
 546             targetArgs[i] = names[idx];
 547         }
 548         names[names.length - 1] = new Name(target, (Object[]) targetArgs);
 549 
 550         LambdaForm form = new LambdaForm("spread", lambdaType.parameterCount(), names);
 551         return SimpleMethodHandle.make(srcType, form);
 552     }
 553 
 554     static void checkSpreadArgument(Object av, int n) {
 555         if (av == null) {
 556             if (n == 0)  return;
 557         } else if (av instanceof Object[]) {
 558             int len = ((Object[])av).length;
 559             if (len == n)  return;
 560         } else {
 561             int len = java.lang.reflect.Array.getLength(av);
 562             if (len == n)  return;
 563         }
 564         // fall through to error:
 565         throw newIllegalArgumentException("array is not of length "+n);
 566     }
 567 
 568     /**
 569      * Pre-initialized NamedFunctions for bootstrapping purposes.
 570      * Factored in an inner class to delay initialization until first usage.
 571      */
 572     static class Lazy {
 573         private static final Class<?> MHI = MethodHandleImpl.class;
 574         private static final Class<?> CLS = Class.class;
 575 
 576         private static final MethodHandle[] ARRAYS;
 577         private static final MethodHandle[] FILL_ARRAYS;
 578 
 579         static final NamedFunction NF_checkSpreadArgument;
 580         static final NamedFunction NF_guardWithCatch;
 581         static final NamedFunction NF_throwException;
 582         static final NamedFunction NF_profileBoolean;
 583 
 584         static final MethodHandle MH_cast;
 585         static final MethodHandle MH_selectAlternative;
 586         static final MethodHandle MH_copyAsPrimitiveArray;
 587         static final MethodHandle MH_fillNewTypedArray;
 588         static final MethodHandle MH_fillNewArray;
 589         static final MethodHandle MH_arrayIdentity;
 590 
 591         static {
 592             ARRAYS      = makeArrays();
 593             FILL_ARRAYS = makeFillArrays();
 594 
 595             try {
 596                 NF_checkSpreadArgument = new NamedFunction(MHI.getDeclaredMethod("checkSpreadArgument", Object.class, int.class));
 597                 NF_guardWithCatch      = new NamedFunction(MHI.getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,
 598                                                                                  MethodHandle.class, Object[].class));
 599                 NF_throwException      = new NamedFunction(MHI.getDeclaredMethod("throwException", Throwable.class));
 600                 NF_profileBoolean      = new NamedFunction(MHI.getDeclaredMethod("profileBoolean", boolean.class, int[].class));
 601 
 602                 NF_checkSpreadArgument.resolve();
 603                 NF_guardWithCatch.resolve();
 604                 NF_throwException.resolve();
 605                 NF_profileBoolean.resolve();
 606 
 607                 MH_cast                 = IMPL_LOOKUP.findVirtual(CLS, "cast",
 608                                             MethodType.methodType(Object.class, Object.class));
 609                 MH_copyAsPrimitiveArray = IMPL_LOOKUP.findStatic(MHI, "copyAsPrimitiveArray",
 610                                             MethodType.methodType(Object.class, Wrapper.class, Object[].class));
 611                 MH_arrayIdentity        = IMPL_LOOKUP.findStatic(MHI, "identity",
 612                                             MethodType.methodType(Object[].class, Object[].class));
 613                 MH_fillNewArray         = IMPL_LOOKUP.findStatic(MHI, "fillNewArray",
 614                                             MethodType.methodType(Object[].class, Integer.class, Object[].class));
 615                 MH_fillNewTypedArray    = IMPL_LOOKUP.findStatic(MHI, "fillNewTypedArray",
 616                                             MethodType.methodType(Object[].class, Object[].class, Integer.class, Object[].class));
 617 
 618                 MH_selectAlternative    = makeIntrinsic(
 619                         IMPL_LOOKUP.findStatic(MHI, "selectAlternative",
 620                                 MethodType.methodType(MethodHandle.class, boolean.class, MethodHandle.class, MethodHandle.class)),
 621                         Intrinsic.SELECT_ALTERNATIVE);
 622             } catch (ReflectiveOperationException ex) {
 623                 throw newInternalError(ex);
 624             }
 625         }
 626     }
 627 
 628     /** Factory method:  Collect or filter selected argument(s). */
 629     static MethodHandle makeCollectArguments(MethodHandle target,
 630                 MethodHandle collector, int collectArgPos, boolean retainOriginalArgs) {
 631         MethodType targetType = target.type();          // (a..., c, [b...])=>r
 632         MethodType collectorType = collector.type();    // (b...)=>c
 633         int collectArgCount = collectorType.parameterCount();
 634         Class<?> collectValType = collectorType.returnType();
 635         int collectValCount = (collectValType == void.class ? 0 : 1);
 636         MethodType srcType = targetType                 // (a..., [b...])=>r
 637                 .dropParameterTypes(collectArgPos, collectArgPos+collectValCount);
 638         if (!retainOriginalArgs) {                      // (a..., b...)=>r
 639             srcType = srcType.insertParameterTypes(collectArgPos, collectorType.parameterList());
 640         }
 641         // in  arglist: [0: ...keep1 | cpos: collect...  | cpos+cacount: keep2... ]
 642         // out arglist: [0: ...keep1 | cpos: collectVal? | cpos+cvcount: keep2... ]
 643         // out(retain): [0: ...keep1 | cpos: cV? coll... | cpos+cvc+cac: keep2... ]
 644 
 645         // Now build a LambdaForm.
 646         MethodType lambdaType = srcType.invokerType();
 647         Name[] names = arguments(2, lambdaType);
 648         final int collectNamePos = names.length - 2;
 649         final int targetNamePos  = names.length - 1;
 650 
 651         Name[] collectorArgs = Arrays.copyOfRange(names, 1 + collectArgPos, 1 + collectArgPos + collectArgCount);
 652         names[collectNamePos] = new Name(collector, (Object[]) collectorArgs);
 653 
 654         // Build argument array for the target.
 655         // Incoming LF args to copy are: [ (mh) headArgs collectArgs tailArgs ].
 656         // Output argument array is [ headArgs (collectVal)? (collectArgs)? tailArgs ].
 657         Name[] targetArgs = new Name[targetType.parameterCount()];
 658         int inputArgPos  = 1;  // incoming LF args to copy to target
 659         int targetArgPos = 0;  // fill pointer for targetArgs
 660         int chunk = collectArgPos;  // |headArgs|
 661         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 662         inputArgPos  += chunk;
 663         targetArgPos += chunk;
 664         if (collectValType != void.class) {
 665             targetArgs[targetArgPos++] = names[collectNamePos];
 666         }
 667         chunk = collectArgCount;
 668         if (retainOriginalArgs) {
 669             System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 670             targetArgPos += chunk;   // optionally pass on the collected chunk
 671         }
 672         inputArgPos += chunk;
 673         chunk = targetArgs.length - targetArgPos;  // all the rest
 674         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 675         assert(inputArgPos + chunk == collectNamePos);  // use of rest of input args also
 676         names[targetNamePos] = new Name(target, (Object[]) targetArgs);
 677 
 678         LambdaForm form = new LambdaForm("collect", lambdaType.parameterCount(), names);
 679         return SimpleMethodHandle.make(srcType, form);
 680     }
 681 
 682     @LambdaForm.Hidden
 683     static
 684     MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {
 685         if (testResult) {
 686             return target;
 687         } else {
 688             return fallback;
 689         }
 690     }
 691 
 692     // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.
 693     @LambdaForm.Hidden
 694     static
 695     boolean profileBoolean(boolean result, int[] counters) {
 696         // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.
 697         int idx = result ? 1 : 0;
 698         try {
 699             counters[idx] = Math.addExact(counters[idx], 1);
 700         } catch (ArithmeticException e) {
 701             // Avoid continuous overflow by halving the problematic count.
 702             counters[idx] = counters[idx] / 2;
 703         }
 704         return result;
 705     }
 706 
 707     // Intrinsified by C2. Returns true if obj is a compile-time constant.
 708     @LambdaForm.Hidden
 709     static
 710     boolean isCompileConstant(Object obj) {
 711         return false;
 712     }
 713 
 714     static
 715     MethodHandle makeGuardWithTest(MethodHandle test,
 716                                    MethodHandle target,
 717                                    MethodHandle fallback) {
 718         MethodType type = target.type();
 719         assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));
 720         MethodType basicType = type.basicType();
 721         LambdaForm form = makeGuardWithTestForm(basicType);
 722         BoundMethodHandle mh;
 723         try {
 724             if (PROFILE_GWT) {
 725                 int[] counts = new int[2];
 726                 mh = (BoundMethodHandle)
 727                         BoundMethodHandle.speciesData_LLLL().constructor().invokeBasic(type, form,
 728                                 (Object) test, (Object) profile(target), (Object) profile(fallback), counts);
 729             } else {
 730                 mh = (BoundMethodHandle)
 731                         BoundMethodHandle.speciesData_LLL().constructor().invokeBasic(type, form,
 732                                 (Object) test, (Object) profile(target), (Object) profile(fallback));
 733             }
 734         } catch (Throwable ex) {
 735             throw uncaughtException(ex);
 736         }
 737         assert(mh.type() == type);
 738         return mh;
 739     }
 740 
 741 
 742     static
 743     MethodHandle profile(MethodHandle target) {
 744         if (DONT_INLINE_THRESHOLD >= 0) {
 745             return makeBlockInliningWrapper(target);
 746         } else {
 747             return target;
 748         }
 749     }
 750 
 751     /**
 752      * Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.
 753      * Corresponding LambdaForm has @DontInline when compiled into bytecode.
 754      */
 755     static
 756     MethodHandle makeBlockInliningWrapper(MethodHandle target) {
 757         LambdaForm lform;
 758         if (DONT_INLINE_THRESHOLD > 0) {
 759             lform = PRODUCE_BLOCK_INLINING_FORM.apply(target);
 760         } else {
 761             lform = PRODUCE_REINVOKER_FORM.apply(target);
 762         }
 763         return new CountingWrapper(target, lform,
 764                 PRODUCE_BLOCK_INLINING_FORM, PRODUCE_REINVOKER_FORM,
 765                                    DONT_INLINE_THRESHOLD);
 766     }
 767 
 768     /** Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle */
 769     private static final Function<MethodHandle, LambdaForm> PRODUCE_BLOCK_INLINING_FORM = new Function<MethodHandle, LambdaForm>() {
 770         @Override
 771         public LambdaForm apply(MethodHandle target) {
 772             return DelegatingMethodHandle.makeReinvokerForm(target,
 773                                MethodTypeForm.LF_DELEGATE_BLOCK_INLINING, CountingWrapper.class, "reinvoker.dontInline", false,
 774                                DelegatingMethodHandle.NF_getTarget, CountingWrapper.NF_maybeStopCounting);
 775         }
 776     };
 777 
 778     /** Constructs simple reinvoker lambda form for a particular method handle */
 779     private static final Function<MethodHandle, LambdaForm> PRODUCE_REINVOKER_FORM = new Function<MethodHandle, LambdaForm>() {
 780         @Override
 781         public LambdaForm apply(MethodHandle target) {
 782             return DelegatingMethodHandle.makeReinvokerForm(target,
 783                     MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, DelegatingMethodHandle.NF_getTarget);
 784         }
 785     };
 786 
 787     /**
 788      * Counting method handle. It has 2 states: counting and non-counting.
 789      * It is in counting state for the first n invocations and then transitions to non-counting state.
 790      * Behavior in counting and non-counting states is determined by lambda forms produced by
 791      * countingFormProducer & nonCountingFormProducer respectively.
 792      */
 793     static class CountingWrapper extends DelegatingMethodHandle {
 794         private final MethodHandle target;
 795         private int count;
 796         private Function<MethodHandle, LambdaForm> countingFormProducer;
 797         private Function<MethodHandle, LambdaForm> nonCountingFormProducer;
 798         private volatile boolean isCounting;
 799 
 800         private CountingWrapper(MethodHandle target, LambdaForm lform,
 801                                 Function<MethodHandle, LambdaForm> countingFromProducer,
 802                                 Function<MethodHandle, LambdaForm> nonCountingFormProducer,
 803                                 int count) {
 804             super(target.type(), lform);
 805             this.target = target;
 806             this.count = count;
 807             this.countingFormProducer = countingFromProducer;
 808             this.nonCountingFormProducer = nonCountingFormProducer;
 809             this.isCounting = (count > 0);
 810         }
 811 
 812         @Hidden
 813         @Override
 814         protected MethodHandle getTarget() {
 815             return target;
 816         }
 817 
 818         @Override
 819         public MethodHandle asTypeUncached(MethodType newType) {
 820             MethodHandle newTarget = target.asType(newType);
 821             MethodHandle wrapper;
 822             if (isCounting) {
 823                 LambdaForm lform;
 824                 lform = countingFormProducer.apply(newTarget);
 825                 wrapper = new CountingWrapper(newTarget, lform, countingFormProducer, nonCountingFormProducer, DONT_INLINE_THRESHOLD);
 826             } else {
 827                 wrapper = newTarget; // no need for a counting wrapper anymore
 828             }
 829             return (asTypeCache = wrapper);
 830         }
 831 
 832         boolean countDown() {
 833             int c = count;
 834             if (c <= 1) {
 835                 // Try to limit number of updates. MethodHandle.updateForm() doesn't guarantee LF update visibility.
 836                 if (isCounting) {
 837                     isCounting = false;
 838                     return true;
 839                 } else {
 840                     return false;
 841                 }
 842             } else {
 843                 count = c - 1;
 844                 return false;
 845             }
 846         }
 847 
 848         @Hidden
 849         static void maybeStopCounting(Object o1) {
 850              CountingWrapper wrapper = (CountingWrapper) o1;
 851              if (wrapper.countDown()) {
 852                  // Reached invocation threshold. Replace counting behavior with a non-counting one.
 853                  LambdaForm lform = wrapper.nonCountingFormProducer.apply(wrapper.target);
 854                  lform.compileToBytecode(); // speed up warmup by avoiding LF interpretation again after transition
 855                  wrapper.updateForm(lform);
 856              }
 857         }
 858 
 859         static final NamedFunction NF_maybeStopCounting;
 860         static {
 861             Class<?> THIS_CLASS = CountingWrapper.class;
 862             try {
 863                 NF_maybeStopCounting = new NamedFunction(THIS_CLASS.getDeclaredMethod("maybeStopCounting", Object.class));
 864             } catch (ReflectiveOperationException ex) {
 865                 throw newInternalError(ex);
 866             }
 867         }
 868     }
 869 
 870     static
 871     LambdaForm makeGuardWithTestForm(MethodType basicType) {
 872         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWT);
 873         if (lform != null)  return lform;
 874         final int THIS_MH      = 0;  // the BMH_LLL
 875         final int ARG_BASE     = 1;  // start of incoming arguments
 876         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
 877         int nameCursor = ARG_LIMIT;
 878         final int GET_TEST     = nameCursor++;
 879         final int GET_TARGET   = nameCursor++;
 880         final int GET_FALLBACK = nameCursor++;
 881         final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;
 882         final int CALL_TEST    = nameCursor++;
 883         final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;
 884         final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST
 885         final int SELECT_ALT   = nameCursor++;
 886         final int CALL_TARGET  = nameCursor++;
 887         assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative
 888 
 889         MethodType lambdaType = basicType.invokerType();
 890         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 891 
 892         BoundMethodHandle.SpeciesData data =
 893                 (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()
 894                                      : BoundMethodHandle.speciesData_LLL();
 895         names[THIS_MH] = names[THIS_MH].withConstraint(data);
 896         names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);
 897         names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);
 898         names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);
 899         if (GET_COUNTERS != -1) {
 900             names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);
 901         }
 902         Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);
 903 
 904         // call test
 905         MethodType testType = basicType.changeReturnType(boolean.class).basicType();
 906         invokeArgs[0] = names[GET_TEST];
 907         names[CALL_TEST] = new Name(testType, invokeArgs);
 908 
 909         // profile branch
 910         if (PROFILE != -1) {
 911             names[PROFILE] = new Name(Lazy.NF_profileBoolean, names[CALL_TEST], names[GET_COUNTERS]);
 912         }
 913         // call selectAlternative
 914         names[SELECT_ALT] = new Name(Lazy.MH_selectAlternative, names[TEST], names[GET_TARGET], names[GET_FALLBACK]);
 915 
 916         // call target or fallback
 917         invokeArgs[0] = names[SELECT_ALT];
 918         names[CALL_TARGET] = new Name(basicType, invokeArgs);
 919 
 920         lform = new LambdaForm("guard", lambdaType.parameterCount(), names, /*forceInline=*/true);
 921 
 922         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);
 923     }
 924 
 925     /**
 926      * The LambdaForm shape for catchException combinator is the following:
 927      * <blockquote><pre>{@code
 928      *  guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{
 929      *    t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);
 930      *    t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);
 931      *    t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);
 932      *    t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);
 933      *    t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);
 934      *    t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);
 935      *    t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);
 936      *   t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}
 937      * }</pre></blockquote>
 938      *
 939      * argL0 and argL2 are target and catcher method handles. argL1 is exception class.
 940      * argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]
 941      * (ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).
 942      *
 943      * Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms
 944      * among catchException combinators with the same basic type.
 945      */
 946     private static LambdaForm makeGuardWithCatchForm(MethodType basicType) {
 947         MethodType lambdaType = basicType.invokerType();
 948 
 949         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWC);
 950         if (lform != null) {
 951             return lform;
 952         }
 953         final int THIS_MH      = 0;  // the BMH_LLLLL
 954         final int ARG_BASE     = 1;  // start of incoming arguments
 955         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
 956 
 957         int nameCursor = ARG_LIMIT;
 958         final int GET_TARGET       = nameCursor++;
 959         final int GET_CLASS        = nameCursor++;
 960         final int GET_CATCHER      = nameCursor++;
 961         final int GET_COLLECT_ARGS = nameCursor++;
 962         final int GET_UNBOX_RESULT = nameCursor++;
 963         final int BOXED_ARGS       = nameCursor++;
 964         final int TRY_CATCH        = nameCursor++;
 965         final int UNBOX_RESULT     = nameCursor++;
 966 
 967         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 968 
 969         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
 970         names[THIS_MH]          = names[THIS_MH].withConstraint(data);
 971         names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
 972         names[GET_CLASS]        = new Name(data.getterFunction(1), names[THIS_MH]);
 973         names[GET_CATCHER]      = new Name(data.getterFunction(2), names[THIS_MH]);
 974         names[GET_COLLECT_ARGS] = new Name(data.getterFunction(3), names[THIS_MH]);
 975         names[GET_UNBOX_RESULT] = new Name(data.getterFunction(4), names[THIS_MH]);
 976 
 977         // FIXME: rework argument boxing/result unboxing logic for LF interpretation
 978 
 979         // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
 980         MethodType collectArgsType = basicType.changeReturnType(Object.class);
 981         MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
 982         Object[] args = new Object[invokeBasic.type().parameterCount()];
 983         args[0] = names[GET_COLLECT_ARGS];
 984         System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
 985         names[BOXED_ARGS] = new Name(makeIntrinsic(invokeBasic, Intrinsic.GUARD_WITH_CATCH), args);
 986 
 987         // t_{i+1}:L=MethodHandleImpl.guardWithCatch(target:L,exType:L,catcher:L,t_{i}:L);
 988         Object[] gwcArgs = new Object[] {names[GET_TARGET], names[GET_CLASS], names[GET_CATCHER], names[BOXED_ARGS]};
 989         names[TRY_CATCH] = new Name(Lazy.NF_guardWithCatch, gwcArgs);
 990 
 991         // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
 992         MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
 993         Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_CATCH]};
 994         names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);
 995 
 996         lform = new LambdaForm("guardWithCatch", lambdaType.parameterCount(), names);
 997 
 998         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
 999     }
1000 
1001     static
1002     MethodHandle makeGuardWithCatch(MethodHandle target,
1003                                     Class<? extends Throwable> exType,
1004                                     MethodHandle catcher) {
1005         MethodType type = target.type();
1006         LambdaForm form = makeGuardWithCatchForm(type.basicType());
1007 
1008         // Prepare auxiliary method handles used during LambdaForm interpretation.
1009         // Box arguments and wrap them into Object[]: ValueConversions.array().
1010         MethodType varargsType = type.changeReturnType(Object[].class);
1011         MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
1012         // Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore().
1013         MethodHandle unboxResult;
1014         Class<?> rtype = type.returnType();
1015         if (rtype.isPrimitive()) {
1016             if (rtype == void.class) {
1017                 unboxResult = ValueConversions.ignore();
1018             } else {
1019                 Wrapper w = Wrapper.forPrimitiveType(type.returnType());
1020                 unboxResult = ValueConversions.unboxExact(w);
1021             }
1022         } else {
1023             unboxResult = MethodHandles.identity(Object.class);
1024         }
1025 
1026         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
1027         BoundMethodHandle mh;
1028         try {
1029             mh = (BoundMethodHandle)
1030                     data.constructor().invokeBasic(type, form, (Object) target, (Object) exType, (Object) catcher,
1031                                                    (Object) collectArgs, (Object) unboxResult);
1032         } catch (Throwable ex) {
1033             throw uncaughtException(ex);
1034         }
1035         assert(mh.type() == type);
1036         return mh;
1037     }
1038 
1039     /**
1040      * Intrinsified during LambdaForm compilation
1041      * (see {@link InvokerBytecodeGenerator#emitGuardWithCatch emitGuardWithCatch}).
1042      */
1043     @LambdaForm.Hidden
1044     static Object guardWithCatch(MethodHandle target, Class<? extends Throwable> exType, MethodHandle catcher,
1045                                  Object... av) throws Throwable {
1046         // Use asFixedArity() to avoid unnecessary boxing of last argument for VarargsCollector case.
1047         try {
1048             return target.asFixedArity().invokeWithArguments(av);
1049         } catch (Throwable t) {
1050             if (!exType.isInstance(t)) throw t;
1051             return catcher.asFixedArity().invokeWithArguments(prepend(t, av));
1052         }
1053     }
1054 
1055     /** Prepend an element {@code elem} to an {@code array}. */
1056     @LambdaForm.Hidden
1057     private static Object[] prepend(Object elem, Object[] array) {
1058         Object[] newArray = new Object[array.length+1];
1059         newArray[0] = elem;
1060         System.arraycopy(array, 0, newArray, 1, array.length);
1061         return newArray;
1062     }
1063 
1064     static
1065     MethodHandle throwException(MethodType type) {
1066         assert(Throwable.class.isAssignableFrom(type.parameterType(0)));
1067         int arity = type.parameterCount();
1068         if (arity > 1) {
1069             MethodHandle mh = throwException(type.dropParameterTypes(1, arity));
1070             mh = MethodHandles.dropArguments(mh, 1, type.parameterList().subList(1, arity));
1071             return mh;
1072         }
1073         return makePairwiseConvert(Lazy.NF_throwException.resolvedHandle(), type, false, true);
1074     }
1075 
1076     static <T extends Throwable> Empty throwException(T t) throws T { throw t; }
1077 
1078     static MethodHandle[] FAKE_METHOD_HANDLE_INVOKE = new MethodHandle[2];
1079     static MethodHandle fakeMethodHandleInvoke(MemberName method) {
1080         int idx;
1081         assert(method.isMethodHandleInvoke());
1082         switch (method.getName()) {
1083         case "invoke":       idx = 0; break;
1084         case "invokeExact":  idx = 1; break;
1085         default:             throw new InternalError(method.getName());
1086         }
1087         MethodHandle mh = FAKE_METHOD_HANDLE_INVOKE[idx];
1088         if (mh != null)  return mh;
1089         MethodType type = MethodType.methodType(Object.class, UnsupportedOperationException.class,
1090                                                 MethodHandle.class, Object[].class);
1091         mh = throwException(type);
1092         mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke MethodHandle"));
1093         if (!method.getInvocationType().equals(mh.type()))
1094             throw new InternalError(method.toString());
1095         mh = mh.withInternalMemberName(method, false);
1096         mh = mh.asVarargsCollector(Object[].class);
1097         assert(method.isVarargs());
1098         FAKE_METHOD_HANDLE_INVOKE[idx] = mh;
1099         return mh;
1100     }
1101 
1102     /**
1103      * Create an alias for the method handle which, when called,
1104      * appears to be called from the same class loader and protection domain
1105      * as hostClass.
1106      * This is an expensive no-op unless the method which is called
1107      * is sensitive to its caller.  A small number of system methods
1108      * are in this category, including Class.forName and Method.invoke.
1109      */
1110     static
1111     MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1112         return BindCaller.bindCaller(mh, hostClass);
1113     }
1114 
1115     // Put the whole mess into its own nested class.
1116     // That way we can lazily load the code and set up the constants.
1117     private static class BindCaller {
1118         static
1119         MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1120             // Do not use this function to inject calls into system classes.
1121             if (hostClass == null
1122                 ||    (hostClass.isArray() ||
1123                        hostClass.isPrimitive() ||
1124                        hostClass.getName().startsWith("java.") ||
1125                        hostClass.getName().startsWith("sun."))) {
1126                 throw new InternalError();  // does not happen, and should not anyway
1127             }
1128             // For simplicity, convert mh to a varargs-like method.
1129             MethodHandle vamh = prepareForInvoker(mh);
1130             // Cache the result of makeInjectedInvoker once per argument class.
1131             MethodHandle bccInvoker = CV_makeInjectedInvoker.get(hostClass);
1132             return restoreToType(bccInvoker.bindTo(vamh), mh, hostClass);
1133         }
1134 
1135         private static MethodHandle makeInjectedInvoker(Class<?> hostClass) {
1136             Class<?> bcc = UNSAFE.defineAnonymousClass(hostClass, T_BYTES, null);
1137             if (hostClass.getClassLoader() != bcc.getClassLoader())
1138                 throw new InternalError(hostClass.getName()+" (CL)");
1139             try {
1140                 if (hostClass.getProtectionDomain() != bcc.getProtectionDomain())
1141                     throw new InternalError(hostClass.getName()+" (PD)");
1142             } catch (SecurityException ex) {
1143                 // Self-check was blocked by security manager.  This is OK.
1144                 // In fact the whole try body could be turned into an assertion.
1145             }
1146             try {
1147                 MethodHandle init = IMPL_LOOKUP.findStatic(bcc, "init", MethodType.methodType(void.class));
1148                 init.invokeExact();  // force initialization of the class
1149             } catch (Throwable ex) {
1150                 throw uncaughtException(ex);
1151             }
1152             MethodHandle bccInvoker;
1153             try {
1154                 MethodType invokerMT = MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1155                 bccInvoker = IMPL_LOOKUP.findStatic(bcc, "invoke_V", invokerMT);
1156             } catch (ReflectiveOperationException ex) {
1157                 throw uncaughtException(ex);
1158             }
1159             // Test the invoker, to ensure that it really injects into the right place.
1160             try {
1161                 MethodHandle vamh = prepareForInvoker(MH_checkCallerClass);
1162                 Object ok = bccInvoker.invokeExact(vamh, new Object[]{hostClass, bcc});
1163             } catch (Throwable ex) {
1164                 throw new InternalError(ex);
1165             }
1166             return bccInvoker;
1167         }
1168         private static ClassValue<MethodHandle> CV_makeInjectedInvoker = new ClassValue<MethodHandle>() {
1169             @Override protected MethodHandle computeValue(Class<?> hostClass) {
1170                 return makeInjectedInvoker(hostClass);
1171             }
1172         };
1173 
1174         // Adapt mh so that it can be called directly from an injected invoker:
1175         private static MethodHandle prepareForInvoker(MethodHandle mh) {
1176             mh = mh.asFixedArity();
1177             MethodType mt = mh.type();
1178             int arity = mt.parameterCount();
1179             MethodHandle vamh = mh.asType(mt.generic());
1180             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1181             vamh = vamh.asSpreader(Object[].class, arity);
1182             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1183             return vamh;
1184         }
1185 
1186         // Undo the adapter effect of prepareForInvoker:
1187         private static MethodHandle restoreToType(MethodHandle vamh,
1188                                                   MethodHandle original,
1189                                                   Class<?> hostClass) {
1190             MethodType type = original.type();
1191             MethodHandle mh = vamh.asCollector(Object[].class, type.parameterCount());
1192             MemberName member = original.internalMemberName();
1193             mh = mh.asType(type);
1194             mh = new WrappedMember(mh, type, member, original.isInvokeSpecial(), hostClass);
1195             return mh;
1196         }
1197 
1198         private static final MethodHandle MH_checkCallerClass;
1199         static {
1200             final Class<?> THIS_CLASS = BindCaller.class;
1201             assert(checkCallerClass(THIS_CLASS, THIS_CLASS));
1202             try {
1203                 MH_checkCallerClass = IMPL_LOOKUP
1204                     .findStatic(THIS_CLASS, "checkCallerClass",
1205                                 MethodType.methodType(boolean.class, Class.class, Class.class));
1206                 assert((boolean) MH_checkCallerClass.invokeExact(THIS_CLASS, THIS_CLASS));
1207             } catch (Throwable ex) {
1208                 throw new InternalError(ex);
1209             }
1210         }
1211 
1212         @CallerSensitive
1213         private static boolean checkCallerClass(Class<?> expected, Class<?> expected2) {
1214             // This method is called via MH_checkCallerClass and so it's
1215             // correct to ask for the immediate caller here.
1216             Class<?> actual = Reflection.getCallerClass();
1217             if (actual != expected && actual != expected2)
1218                 throw new InternalError("found "+actual.getName()+", expected "+expected.getName()
1219                                         +(expected == expected2 ? "" : ", or else "+expected2.getName()));
1220             return true;
1221         }
1222 
1223         private static final byte[] T_BYTES;
1224         static {
1225             final Object[] values = {null};
1226             AccessController.doPrivileged(new PrivilegedAction<>() {
1227                     public Void run() {
1228                         try {
1229                             Class<T> tClass = T.class;
1230                             String tName = tClass.getName();
1231                             String tResource = tName.substring(tName.lastIndexOf('.')+1)+".class";
1232                             java.net.URLConnection uconn = tClass.getResource(tResource).openConnection();
1233                             int len = uconn.getContentLength();
1234                             byte[] bytes = new byte[len];
1235                             try (java.io.InputStream str = uconn.getInputStream()) {
1236                                 int nr = str.read(bytes);
1237                                 if (nr != len)  throw new java.io.IOException(tResource);
1238                             }
1239                             values[0] = bytes;
1240                         } catch (java.io.IOException ex) {
1241                             throw new InternalError(ex);
1242                         }
1243                         return null;
1244                     }
1245                 });
1246             T_BYTES = (byte[]) values[0];
1247         }
1248 
1249         // The following class is used as a template for Unsafe.defineAnonymousClass:
1250         private static class T {
1251             static void init() { }  // side effect: initializes this class
1252             static Object invoke_V(MethodHandle vamh, Object[] args) throws Throwable {
1253                 return vamh.invokeExact(args);
1254             }
1255         }
1256     }
1257 
1258 
1259     /** This subclass allows a wrapped method handle to be re-associated with an arbitrary member name. */
1260     private static final class WrappedMember extends DelegatingMethodHandle {
1261         private final MethodHandle target;
1262         private final MemberName member;
1263         private final Class<?> callerClass;
1264         private final boolean isInvokeSpecial;
1265 
1266         private WrappedMember(MethodHandle target, MethodType type,
1267                               MemberName member, boolean isInvokeSpecial,
1268                               Class<?> callerClass) {
1269             super(type, target);
1270             this.target = target;
1271             this.member = member;
1272             this.callerClass = callerClass;
1273             this.isInvokeSpecial = isInvokeSpecial;
1274         }
1275 
1276         @Override
1277         MemberName internalMemberName() {
1278             return member;
1279         }
1280         @Override
1281         Class<?> internalCallerClass() {
1282             return callerClass;
1283         }
1284         @Override
1285         boolean isInvokeSpecial() {
1286             return isInvokeSpecial;
1287         }
1288         @Override
1289         protected MethodHandle getTarget() {
1290             return target;
1291         }
1292         @Override
1293         public MethodHandle asTypeUncached(MethodType newType) {
1294             // This MH is an alias for target, except for the MemberName
1295             // Drop the MemberName if there is any conversion.
1296             return asTypeCache = target.asType(newType);
1297         }
1298     }
1299 
1300     static MethodHandle makeWrappedMember(MethodHandle target, MemberName member, boolean isInvokeSpecial) {
1301         if (member.equals(target.internalMemberName()) && isInvokeSpecial == target.isInvokeSpecial())
1302             return target;
1303         return new WrappedMember(target, target.type(), member, isInvokeSpecial, null);
1304     }
1305 
1306     /** Intrinsic IDs */
1307     /*non-public*/
1308     enum Intrinsic {
1309         SELECT_ALTERNATIVE,
1310         GUARD_WITH_CATCH,
1311         NEW_ARRAY,
1312         ARRAY_LOAD,
1313         ARRAY_STORE,
1314         IDENTITY,
1315         ZERO,
1316         NONE // no intrinsic associated
1317     }
1318 
1319     /** Mark arbitrary method handle as intrinsic.
1320      * InvokerBytecodeGenerator uses this info to produce more efficient bytecode shape. */
1321     private static final class IntrinsicMethodHandle extends DelegatingMethodHandle {
1322         private final MethodHandle target;
1323         private final Intrinsic intrinsicName;
1324 
1325         IntrinsicMethodHandle(MethodHandle target, Intrinsic intrinsicName) {
1326             super(target.type(), target);
1327             this.target = target;
1328             this.intrinsicName = intrinsicName;
1329         }
1330 
1331         @Override
1332         protected MethodHandle getTarget() {
1333             return target;
1334         }
1335 
1336         @Override
1337         Intrinsic intrinsicName() {
1338             return intrinsicName;
1339         }
1340 
1341         @Override
1342         public MethodHandle asTypeUncached(MethodType newType) {
1343             // This MH is an alias for target, except for the intrinsic name
1344             // Drop the name if there is any conversion.
1345             return asTypeCache = target.asType(newType);
1346         }
1347 
1348         @Override
1349         String internalProperties() {
1350             return super.internalProperties() +
1351                     "\n& Intrinsic="+intrinsicName;
1352         }
1353 
1354         @Override
1355         public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
1356             if (intrinsicName == Intrinsic.IDENTITY) {
1357                 MethodType resultType = type().asCollectorType(arrayType, arrayLength);
1358                 MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
1359                 return newArray.asType(resultType);
1360             }
1361             return super.asCollector(arrayType, arrayLength);
1362         }
1363     }
1364 
1365     static MethodHandle makeIntrinsic(MethodHandle target, Intrinsic intrinsicName) {
1366         if (intrinsicName == target.intrinsicName())
1367             return target;
1368         return new IntrinsicMethodHandle(target, intrinsicName);
1369     }
1370 
1371     static MethodHandle makeIntrinsic(MethodType type, LambdaForm form, Intrinsic intrinsicName) {
1372         return new IntrinsicMethodHandle(SimpleMethodHandle.make(type, form), intrinsicName);
1373     }
1374 
1375     /// Collection of multiple arguments.
1376 
1377     private static MethodHandle findCollector(String name, int nargs, Class<?> rtype, Class<?>... ptypes) {
1378         MethodType type = MethodType.genericMethodType(nargs)
1379                 .changeReturnType(rtype)
1380                 .insertParameterTypes(0, ptypes);
1381         try {
1382             return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, name, type);
1383         } catch (ReflectiveOperationException ex) {
1384             return null;
1385         }
1386     }
1387 
1388     private static final Object[] NO_ARGS_ARRAY = {};
1389     private static Object[] makeArray(Object... args) { return args; }
1390     private static Object[] array() { return NO_ARGS_ARRAY; }
1391     private static Object[] array(Object a0)
1392                 { return makeArray(a0); }
1393     private static Object[] array(Object a0, Object a1)
1394                 { return makeArray(a0, a1); }
1395     private static Object[] array(Object a0, Object a1, Object a2)
1396                 { return makeArray(a0, a1, a2); }
1397     private static Object[] array(Object a0, Object a1, Object a2, Object a3)
1398                 { return makeArray(a0, a1, a2, a3); }
1399     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1400                                   Object a4)
1401                 { return makeArray(a0, a1, a2, a3, a4); }
1402     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1403                                   Object a4, Object a5)
1404                 { return makeArray(a0, a1, a2, a3, a4, a5); }
1405     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1406                                   Object a4, Object a5, Object a6)
1407                 { return makeArray(a0, a1, a2, a3, a4, a5, a6); }
1408     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1409                                   Object a4, Object a5, Object a6, Object a7)
1410                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7); }
1411     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1412                                   Object a4, Object a5, Object a6, Object a7,
1413                                   Object a8)
1414                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8); }
1415     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1416                                   Object a4, Object a5, Object a6, Object a7,
1417                                   Object a8, Object a9)
1418                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); }
1419 
1420     private static final int ARRAYS_COUNT = 11;
1421 
1422     private static MethodHandle[] makeArrays() {
1423         MethodHandle[] mhs = new MethodHandle[MAX_ARITY + 1];
1424         for (int i = 0; i < ARRAYS_COUNT; i++) {
1425             MethodHandle mh = findCollector("array", i, Object[].class);
1426             mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1427             mhs[i] = mh;
1428         }
1429         assert(assertArrayMethodCount(mhs));
1430         return mhs;
1431     }
1432 
1433     private static boolean assertArrayMethodCount(MethodHandle[] mhs) {
1434         assert(findCollector("array", ARRAYS_COUNT, Object[].class) == null);
1435         for (int i = 0; i < ARRAYS_COUNT; i++) {
1436             assert(mhs[i] != null);
1437         }
1438         return true;
1439     }
1440 
1441     // filling versions of the above:
1442     // using Integer len instead of int len and no varargs to avoid bootstrapping problems
1443     private static Object[] fillNewArray(Integer len, Object[] /*not ...*/ args) {
1444         Object[] a = new Object[len];
1445         fillWithArguments(a, 0, args);
1446         return a;
1447     }
1448     private static Object[] fillNewTypedArray(Object[] example, Integer len, Object[] /*not ...*/ args) {
1449         Object[] a = Arrays.copyOf(example, len);
1450         assert(a.getClass() != Object[].class);
1451         fillWithArguments(a, 0, args);
1452         return a;
1453     }
1454     private static void fillWithArguments(Object[] a, int pos, Object... args) {
1455         System.arraycopy(args, 0, a, pos, args.length);
1456     }
1457     // using Integer pos instead of int pos to avoid bootstrapping problems
1458     private static Object[] fillArray(Integer pos, Object[] a, Object a0)
1459                 { fillWithArguments(a, pos, a0); return a; }
1460     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1)
1461                 { fillWithArguments(a, pos, a0, a1); return a; }
1462     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2)
1463                 { fillWithArguments(a, pos, a0, a1, a2); return a; }
1464     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3)
1465                 { fillWithArguments(a, pos, a0, a1, a2, a3); return a; }
1466     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1467                                   Object a4)
1468                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4); return a; }
1469     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1470                                   Object a4, Object a5)
1471                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5); return a; }
1472     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1473                                   Object a4, Object a5, Object a6)
1474                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6); return a; }
1475     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1476                                   Object a4, Object a5, Object a6, Object a7)
1477                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7); return a; }
1478     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1479                                   Object a4, Object a5, Object a6, Object a7,
1480                                   Object a8)
1481                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8); return a; }
1482     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1483                                   Object a4, Object a5, Object a6, Object a7,
1484                                   Object a8, Object a9)
1485                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); return a; }
1486 
1487     private static final int FILL_ARRAYS_COUNT = 11; // current number of fillArray methods
1488 
1489     private static MethodHandle[] makeFillArrays() {
1490         MethodHandle[] mhs = new MethodHandle[FILL_ARRAYS_COUNT];
1491         mhs[0] = null;  // there is no empty fill; at least a0 is required
1492         for (int i = 1; i < FILL_ARRAYS_COUNT; i++) {
1493             MethodHandle mh = findCollector("fillArray", i, Object[].class, Integer.class, Object[].class);
1494             mhs[i] = mh;
1495         }
1496         assert(assertFillArrayMethodCount(mhs));
1497         return mhs;
1498     }
1499 
1500     private static boolean assertFillArrayMethodCount(MethodHandle[] mhs) {
1501         assert(findCollector("fillArray", FILL_ARRAYS_COUNT, Object[].class, Integer.class, Object[].class) == null);
1502         for (int i = 1; i < FILL_ARRAYS_COUNT; i++) {
1503             assert(mhs[i] != null);
1504         }
1505         return true;
1506     }
1507 
1508     private static Object copyAsPrimitiveArray(Wrapper w, Object... boxes) {
1509         Object a = w.makeArray(boxes.length);
1510         w.copyArrayUnboxing(boxes, 0, a, 0, boxes.length);
1511         return a;
1512     }
1513 
1514     /** Return a method handle that takes the indicated number of Object
1515      *  arguments and returns an Object array of them, as if for varargs.
1516      */
1517     static MethodHandle varargsArray(int nargs) {
1518         MethodHandle mh = Lazy.ARRAYS[nargs];
1519         if (mh != null)  return mh;
1520         mh = buildVarargsArray(Lazy.MH_fillNewArray, Lazy.MH_arrayIdentity, nargs);
1521         assert(assertCorrectArity(mh, nargs));
1522         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1523         return Lazy.ARRAYS[nargs] = mh;
1524     }
1525 
1526     private static boolean assertCorrectArity(MethodHandle mh, int arity) {
1527         assert(mh.type().parameterCount() == arity) : "arity != "+arity+": "+mh;
1528         return true;
1529     }
1530 
1531     // Array identity function (used as Lazy.MH_arrayIdentity).
1532     static <T> T[] identity(T[] x) {
1533         return x;
1534     }
1535 
1536     private static MethodHandle buildVarargsArray(MethodHandle newArray, MethodHandle finisher, int nargs) {
1537         // Build up the result mh as a sequence of fills like this:
1538         //   finisher(fill(fill(newArrayWA(23,x1..x10),10,x11..x20),20,x21..x23))
1539         // The various fill(_,10*I,___*[J]) are reusable.
1540         int leftLen = Math.min(nargs, LEFT_ARGS);  // absorb some arguments immediately
1541         int rightLen = nargs - leftLen;
1542         MethodHandle leftCollector = newArray.bindTo(nargs);
1543         leftCollector = leftCollector.asCollector(Object[].class, leftLen);
1544         MethodHandle mh = finisher;
1545         if (rightLen > 0) {
1546             MethodHandle rightFiller = fillToRight(LEFT_ARGS + rightLen);
1547             if (mh == Lazy.MH_arrayIdentity)
1548                 mh = rightFiller;
1549             else
1550                 mh = MethodHandles.collectArguments(mh, 0, rightFiller);
1551         }
1552         if (mh == Lazy.MH_arrayIdentity)
1553             mh = leftCollector;
1554         else
1555             mh = MethodHandles.collectArguments(mh, 0, leftCollector);
1556         return mh;
1557     }
1558 
1559     private static final int LEFT_ARGS = FILL_ARRAYS_COUNT - 1;
1560     private static final MethodHandle[] FILL_ARRAY_TO_RIGHT = new MethodHandle[MAX_ARITY+1];
1561     /** fill_array_to_right(N).invoke(a, argL..arg[N-1])
1562      *  fills a[L]..a[N-1] with corresponding arguments,
1563      *  and then returns a.  The value L is a global constant (LEFT_ARGS).
1564      */
1565     private static MethodHandle fillToRight(int nargs) {
1566         MethodHandle filler = FILL_ARRAY_TO_RIGHT[nargs];
1567         if (filler != null)  return filler;
1568         filler = buildFiller(nargs);
1569         assert(assertCorrectArity(filler, nargs - LEFT_ARGS + 1));
1570         return FILL_ARRAY_TO_RIGHT[nargs] = filler;
1571     }
1572     private static MethodHandle buildFiller(int nargs) {
1573         if (nargs <= LEFT_ARGS)
1574             return Lazy.MH_arrayIdentity;  // no args to fill; return the array unchanged
1575         // we need room for both mh and a in mh.invoke(a, arg*[nargs])
1576         final int CHUNK = LEFT_ARGS;
1577         int rightLen = nargs % CHUNK;
1578         int midLen = nargs - rightLen;
1579         if (rightLen == 0) {
1580             midLen = nargs - (rightLen = CHUNK);
1581             if (FILL_ARRAY_TO_RIGHT[midLen] == null) {
1582                 // build some precursors from left to right
1583                 for (int j = LEFT_ARGS % CHUNK; j < midLen; j += CHUNK)
1584                     if (j > LEFT_ARGS)  fillToRight(j);
1585             }
1586         }
1587         if (midLen < LEFT_ARGS) rightLen = nargs - (midLen = LEFT_ARGS);
1588         assert(rightLen > 0);
1589         MethodHandle midFill = fillToRight(midLen);  // recursive fill
1590         MethodHandle rightFill = Lazy.FILL_ARRAYS[rightLen].bindTo(midLen);  // [midLen..nargs-1]
1591         assert(midFill.type().parameterCount()   == 1 + midLen - LEFT_ARGS);
1592         assert(rightFill.type().parameterCount() == 1 + rightLen);
1593 
1594         // Combine the two fills:
1595         //   right(mid(a, x10..x19), x20..x23)
1596         // The final product will look like this:
1597         //   right(mid(newArrayLeft(24, x0..x9), x10..x19), x20..x23)
1598         if (midLen == LEFT_ARGS)
1599             return rightFill;
1600         else
1601             return MethodHandles.collectArguments(rightFill, 0, midFill);
1602     }
1603 
1604     // Type-polymorphic version of varargs maker.
1605     private static final ClassValue<MethodHandle[]> TYPED_COLLECTORS
1606         = new ClassValue<MethodHandle[]>() {
1607             @Override
1608             protected MethodHandle[] computeValue(Class<?> type) {
1609                 return new MethodHandle[256];
1610             }
1611     };
1612 
1613     static final int MAX_JVM_ARITY = 255;  // limit imposed by the JVM
1614 
1615     /** Return a method handle that takes the indicated number of
1616      *  typed arguments and returns an array of them.
1617      *  The type argument is the array type.
1618      */
1619     static MethodHandle varargsArray(Class<?> arrayType, int nargs) {
1620         Class<?> elemType = arrayType.getComponentType();
1621         if (elemType == null)  throw new IllegalArgumentException("not an array: "+arrayType);
1622         // FIXME: Need more special casing and caching here.
1623         if (nargs >= MAX_JVM_ARITY/2 - 1) {
1624             int slots = nargs;
1625             final int MAX_ARRAY_SLOTS = MAX_JVM_ARITY - 1;  // 1 for receiver MH
1626             if (slots <= MAX_ARRAY_SLOTS && elemType.isPrimitive())
1627                 slots *= Wrapper.forPrimitiveType(elemType).stackSlots();
1628             if (slots > MAX_ARRAY_SLOTS)
1629                 throw new IllegalArgumentException("too many arguments: "+arrayType.getSimpleName()+", length "+nargs);
1630         }
1631         if (elemType == Object.class)
1632             return varargsArray(nargs);
1633         // other cases:  primitive arrays, subtypes of Object[]
1634         MethodHandle cache[] = TYPED_COLLECTORS.get(elemType);
1635         MethodHandle mh = nargs < cache.length ? cache[nargs] : null;
1636         if (mh != null)  return mh;
1637         if (nargs == 0) {
1638             Object example = java.lang.reflect.Array.newInstance(arrayType.getComponentType(), 0);
1639             mh = MethodHandles.constant(arrayType, example);
1640         } else if (elemType.isPrimitive()) {
1641             MethodHandle builder = Lazy.MH_fillNewArray;
1642             MethodHandle producer = buildArrayProducer(arrayType);
1643             mh = buildVarargsArray(builder, producer, nargs);
1644         } else {
1645             Class<? extends Object[]> objArrayType = arrayType.asSubclass(Object[].class);
1646             Object[] example = Arrays.copyOf(NO_ARGS_ARRAY, 0, objArrayType);
1647             MethodHandle builder = Lazy.MH_fillNewTypedArray.bindTo(example);
1648             MethodHandle producer = Lazy.MH_arrayIdentity; // must be weakly typed
1649             mh = buildVarargsArray(builder, producer, nargs);
1650         }
1651         mh = mh.asType(MethodType.methodType(arrayType, Collections.<Class<?>>nCopies(nargs, elemType)));
1652         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1653         assert(assertCorrectArity(mh, nargs));
1654         if (nargs < cache.length)
1655             cache[nargs] = mh;
1656         return mh;
1657     }
1658 
1659     private static MethodHandle buildArrayProducer(Class<?> arrayType) {
1660         Class<?> elemType = arrayType.getComponentType();
1661         assert(elemType.isPrimitive());
1662         return Lazy.MH_copyAsPrimitiveArray.bindTo(Wrapper.forPrimitiveType(elemType));
1663     }
1664 
1665     /*non-public*/ static void assertSame(Object mh1, Object mh2) {
1666         if (mh1 != mh2) {
1667             String msg = String.format("mh1 != mh2: mh1 = %s (form: %s); mh2 = %s (form: %s)",
1668                     mh1, ((MethodHandle)mh1).form,
1669                     mh2, ((MethodHandle)mh2).form);
1670             throw newInternalError(msg);
1671         }
1672     }
1673 }
--- EOF ---