8145371: ClassCastException thrown in LambdaFormEditor.getInCache
Reviewed-by: mhaupt

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   5  * This code is free software; you can redistribute it and/or modify it
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   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  *
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  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).
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  25 
  26 package java.lang.invoke;
  27 
  28 import jdk.internal.misc.JavaLangInvokeAccess;
  29 import jdk.internal.misc.SharedSecrets;
  30 import jdk.internal.org.objectweb.asm.AnnotationVisitor;
  31 import jdk.internal.org.objectweb.asm.ClassWriter;
  32 import jdk.internal.org.objectweb.asm.MethodVisitor;
  33 import jdk.internal.reflect.CallerSensitive;
  34 import jdk.internal.reflect.Reflection;
  35 import jdk.internal.vm.annotation.ForceInline;
  36 import jdk.internal.vm.annotation.Stable;
  37 import sun.invoke.empty.Empty;
  38 import sun.invoke.util.ValueConversions;
  39 import sun.invoke.util.VerifyType;
  40 import sun.invoke.util.Wrapper;
  41 
  42 import java.lang.reflect.Array;
  43 import java.util.Arrays;
  44 import java.util.Collections;
  45 import java.util.Iterator;
  46 import java.util.List;
  47 import java.util.Map;
  48 import java.util.function.Function;
  49 import java.util.stream.Stream;
  50 
  51 import static java.lang.invoke.LambdaForm.*;
  52 import static java.lang.invoke.MethodHandleStatics.*;
  53 import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
  54 import static jdk.internal.org.objectweb.asm.Opcodes.*;
  55 
  56 /**
  57  * Trusted implementation code for MethodHandle.
  58  * @author jrose
  59  */
  60 /*non-public*/ abstract class MethodHandleImpl {
  61 
  62     /// Factory methods to create method handles:
  63 
  64     static MethodHandle makeArrayElementAccessor(Class<?> arrayClass, ArrayAccess access) {
  65         if (arrayClass == Object[].class) {
  66             return ArrayAccess.objectAccessor(access);
  67         }
  68         if (!arrayClass.isArray())
  69             throw newIllegalArgumentException("not an array: "+arrayClass);
  70         MethodHandle[] cache = ArrayAccessor.TYPED_ACCESSORS.get(arrayClass);
  71         int cacheIndex = ArrayAccess.cacheIndex(access);
  72         MethodHandle mh = cache[cacheIndex];
  73         if (mh != null)  return mh;
  74         mh = ArrayAccessor.getAccessor(arrayClass, access);
  75         MethodType correctType = ArrayAccessor.correctType(arrayClass, access);
  76         if (mh.type() != correctType) {
  77             assert(mh.type().parameterType(0) == Object[].class);
  78             /* if access == SET */ assert(access != ArrayAccess.SET || mh.type().parameterType(2) == Object.class);
  79             /* if access == GET */ assert(access != ArrayAccess.GET ||
  80                     (mh.type().returnType() == Object.class &&
  81                      correctType.parameterType(0).getComponentType() == correctType.returnType()));
  82             // safe to view non-strictly, because element type follows from array type
  83             mh = mh.viewAsType(correctType, false);
  84         }
  85         mh = makeIntrinsic(mh, ArrayAccess.intrinsic(access));
  86         // Atomically update accessor cache.
  87         synchronized(cache) {
  88             if (cache[cacheIndex] == null) {
  89                 cache[cacheIndex] = mh;
  90             } else {
  91                 // Throw away newly constructed accessor and use cached version.
  92                 mh = cache[cacheIndex];
  93             }
  94         }
  95         return mh;
  96     }
  97 
  98     enum ArrayAccess {
  99         GET, SET, LENGTH;
 100 
 101         // As ArrayAccess and ArrayAccessor have a circular dependency, the ArrayAccess properties cannot be stored in
 102         // final fields.
 103 
 104         static String opName(ArrayAccess a) {
 105             switch (a) {
 106                 case GET: return "getElement";
 107                 case SET: return "setElement";
 108                 case LENGTH: return "length";
 109             }
 110             throw unmatchedArrayAccess(a);
 111         }
 112 
 113         static MethodHandle objectAccessor(ArrayAccess a) {
 114             switch (a) {
 115                 case GET: return ArrayAccessor.OBJECT_ARRAY_GETTER;
 116                 case SET: return ArrayAccessor.OBJECT_ARRAY_SETTER;
 117                 case LENGTH: return ArrayAccessor.OBJECT_ARRAY_LENGTH;
 118             }
 119             throw unmatchedArrayAccess(a);
 120         }
 121 
 122         static int cacheIndex(ArrayAccess a) {
 123             switch (a) {
 124                 case GET: return ArrayAccessor.GETTER_INDEX;
 125                 case SET: return ArrayAccessor.SETTER_INDEX;
 126                 case LENGTH: return ArrayAccessor.LENGTH_INDEX;
 127             }
 128             throw unmatchedArrayAccess(a);
 129         }
 130 
 131         static Intrinsic intrinsic(ArrayAccess a) {
 132             switch (a) {
 133                 case GET: return Intrinsic.ARRAY_LOAD;
 134                 case SET: return Intrinsic.ARRAY_STORE;
 135                 case LENGTH: return Intrinsic.ARRAY_LENGTH;
 136             }
 137             throw unmatchedArrayAccess(a);
 138         }
 139     }
 140 
 141     static InternalError unmatchedArrayAccess(ArrayAccess a) {
 142         return newInternalError("should not reach here (unmatched ArrayAccess: " + a + ")");
 143     }
 144 
 145     static final class ArrayAccessor {
 146         /// Support for array element and length access
 147         static final int GETTER_INDEX = 0, SETTER_INDEX = 1, LENGTH_INDEX = 2, INDEX_LIMIT = 3;
 148         static final ClassValue<MethodHandle[]> TYPED_ACCESSORS
 149                 = new ClassValue<MethodHandle[]>() {
 150                     @Override
 151                     protected MethodHandle[] computeValue(Class<?> type) {
 152                         return new MethodHandle[INDEX_LIMIT];
 153                     }
 154                 };
 155         static final MethodHandle OBJECT_ARRAY_GETTER, OBJECT_ARRAY_SETTER, OBJECT_ARRAY_LENGTH;
 156         static {
 157             MethodHandle[] cache = TYPED_ACCESSORS.get(Object[].class);
 158             cache[GETTER_INDEX] = OBJECT_ARRAY_GETTER = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.GET),    Intrinsic.ARRAY_LOAD);
 159             cache[SETTER_INDEX] = OBJECT_ARRAY_SETTER = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.SET),    Intrinsic.ARRAY_STORE);
 160             cache[LENGTH_INDEX] = OBJECT_ARRAY_LENGTH = makeIntrinsic(getAccessor(Object[].class, ArrayAccess.LENGTH), Intrinsic.ARRAY_LENGTH);
 161 
 162             assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_GETTER.internalMemberName()));
 163             assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_SETTER.internalMemberName()));
 164             assert(InvokerBytecodeGenerator.isStaticallyInvocable(ArrayAccessor.OBJECT_ARRAY_LENGTH.internalMemberName()));
 165         }
 166 
 167         static int     getElementI(int[]     a, int i)            { return              a[i]; }
 168         static long    getElementJ(long[]    a, int i)            { return              a[i]; }
 169         static float   getElementF(float[]   a, int i)            { return              a[i]; }
 170         static double  getElementD(double[]  a, int i)            { return              a[i]; }
 171         static boolean getElementZ(boolean[] a, int i)            { return              a[i]; }
 172         static byte    getElementB(byte[]    a, int i)            { return              a[i]; }
 173         static short   getElementS(short[]   a, int i)            { return              a[i]; }
 174         static char    getElementC(char[]    a, int i)            { return              a[i]; }
 175         static Object  getElementL(Object[]  a, int i)            { return              a[i]; }
 176 
 177         static void    setElementI(int[]     a, int i, int     x) {              a[i] = x; }
 178         static void    setElementJ(long[]    a, int i, long    x) {              a[i] = x; }
 179         static void    setElementF(float[]   a, int i, float   x) {              a[i] = x; }
 180         static void    setElementD(double[]  a, int i, double  x) {              a[i] = x; }
 181         static void    setElementZ(boolean[] a, int i, boolean x) {              a[i] = x; }
 182         static void    setElementB(byte[]    a, int i, byte    x) {              a[i] = x; }
 183         static void    setElementS(short[]   a, int i, short   x) {              a[i] = x; }
 184         static void    setElementC(char[]    a, int i, char    x) {              a[i] = x; }
 185         static void    setElementL(Object[]  a, int i, Object  x) {              a[i] = x; }
 186 
 187         static int     lengthI(int[]     a)                       { return a.length; }
 188         static int     lengthJ(long[]    a)                       { return a.length; }
 189         static int     lengthF(float[]   a)                       { return a.length; }
 190         static int     lengthD(double[]  a)                       { return a.length; }
 191         static int     lengthZ(boolean[] a)                       { return a.length; }
 192         static int     lengthB(byte[]    a)                       { return a.length; }
 193         static int     lengthS(short[]   a)                       { return a.length; }
 194         static int     lengthC(char[]    a)                       { return a.length; }
 195         static int     lengthL(Object[]  a)                       { return a.length; }
 196 
 197         static String name(Class<?> arrayClass, ArrayAccess access) {
 198             Class<?> elemClass = arrayClass.getComponentType();
 199             if (elemClass == null)  throw newIllegalArgumentException("not an array", arrayClass);
 200             return ArrayAccess.opName(access) + Wrapper.basicTypeChar(elemClass);
 201         }
 202         static MethodType type(Class<?> arrayClass, ArrayAccess access) {
 203             Class<?> elemClass = arrayClass.getComponentType();
 204             Class<?> arrayArgClass = arrayClass;
 205             if (!elemClass.isPrimitive()) {
 206                 arrayArgClass = Object[].class;
 207                 elemClass = Object.class;
 208             }
 209             switch (access) {
 210                 case GET:    return MethodType.methodType(elemClass,  arrayArgClass, int.class);
 211                 case SET:    return MethodType.methodType(void.class, arrayArgClass, int.class, elemClass);
 212                 case LENGTH: return MethodType.methodType(int.class,  arrayArgClass);
 213             }
 214             throw unmatchedArrayAccess(access);
 215         }
 216         static MethodType correctType(Class<?> arrayClass, ArrayAccess access) {
 217             Class<?> elemClass = arrayClass.getComponentType();
 218             switch (access) {
 219                 case GET:    return MethodType.methodType(elemClass,  arrayClass, int.class);
 220                 case SET:    return MethodType.methodType(void.class, arrayClass, int.class, elemClass);
 221                 case LENGTH: return MethodType.methodType(int.class,  arrayClass);
 222             }
 223             throw unmatchedArrayAccess(access);
 224         }
 225         static MethodHandle getAccessor(Class<?> arrayClass, ArrayAccess access) {
 226             String     name = name(arrayClass, access);
 227             MethodType type = type(arrayClass, access);
 228             try {
 229                 return IMPL_LOOKUP.findStatic(ArrayAccessor.class, name, type);
 230             } catch (ReflectiveOperationException ex) {
 231                 throw uncaughtException(ex);
 232             }
 233         }
 234     }
 235 
 236     /**
 237      * Create a JVM-level adapter method handle to conform the given method
 238      * handle to the similar newType, using only pairwise argument conversions.
 239      * For each argument, convert incoming argument to the exact type needed.
 240      * The argument conversions allowed are casting, boxing and unboxing,
 241      * integral widening or narrowing, and floating point widening or narrowing.
 242      * @param srcType required call type
 243      * @param target original method handle
 244      * @param strict if true, only asType conversions are allowed; if false, explicitCastArguments conversions allowed
 245      * @param monobox if true, unboxing conversions are assumed to be exactly typed (Integer to int only, not long or double)
 246      * @return an adapter to the original handle with the desired new type,
 247      *          or the original target if the types are already identical
 248      *          or null if the adaptation cannot be made
 249      */
 250     static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
 251                                             boolean strict, boolean monobox) {
 252         MethodType dstType = target.type();
 253         if (srcType == dstType)
 254             return target;
 255         return makePairwiseConvertByEditor(target, srcType, strict, monobox);
 256     }
 257 
 258     private static int countNonNull(Object[] array) {
 259         int count = 0;
 260         for (Object x : array) {
 261             if (x != null)  ++count;
 262         }
 263         return count;
 264     }
 265 
 266     static MethodHandle makePairwiseConvertByEditor(MethodHandle target, MethodType srcType,
 267                                                     boolean strict, boolean monobox) {
 268         Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);
 269         int convCount = countNonNull(convSpecs);
 270         if (convCount == 0)
 271             return target.viewAsType(srcType, strict);
 272         MethodType basicSrcType = srcType.basicType();
 273         MethodType midType = target.type().basicType();
 274         BoundMethodHandle mh = target.rebind();
 275         // FIXME: Reduce number of bindings when there is more than one Class conversion.
 276         // FIXME: Reduce number of bindings when there are repeated conversions.
 277         for (int i = 0; i < convSpecs.length-1; i++) {
 278             Object convSpec = convSpecs[i];
 279             if (convSpec == null)  continue;
 280             MethodHandle fn;
 281             if (convSpec instanceof Class) {
 282                 fn = getConstantHandle(MH_cast).bindTo(convSpec);
 283             } else {
 284                 fn = (MethodHandle) convSpec;
 285             }
 286             Class<?> newType = basicSrcType.parameterType(i);
 287             if (--convCount == 0)
 288                 midType = srcType;
 289             else
 290                 midType = midType.changeParameterType(i, newType);
 291             LambdaForm form2 = mh.editor().filterArgumentForm(1+i, BasicType.basicType(newType));
 292             mh = mh.copyWithExtendL(midType, form2, fn);
 293             mh = mh.rebind();
 294         }
 295         Object convSpec = convSpecs[convSpecs.length-1];
 296         if (convSpec != null) {
 297             MethodHandle fn;
 298             if (convSpec instanceof Class) {
 299                 if (convSpec == void.class)
 300                     fn = null;
 301                 else
 302                     fn = getConstantHandle(MH_cast).bindTo(convSpec);
 303             } else {
 304                 fn = (MethodHandle) convSpec;
 305             }
 306             Class<?> newType = basicSrcType.returnType();
 307             assert(--convCount == 0);
 308             midType = srcType;
 309             if (fn != null) {
 310                 mh = mh.rebind();  // rebind if too complex
 311                 LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), false);
 312                 mh = mh.copyWithExtendL(midType, form2, fn);
 313             } else {
 314                 LambdaForm form2 = mh.editor().filterReturnForm(BasicType.basicType(newType), true);
 315                 mh = mh.copyWith(midType, form2);
 316             }
 317         }
 318         assert(convCount == 0);
 319         assert(mh.type().equals(srcType));
 320         return mh;
 321     }
 322 
 323     static MethodHandle makePairwiseConvertIndirect(MethodHandle target, MethodType srcType,
 324                                                     boolean strict, boolean monobox) {
 325         assert(target.type().parameterCount() == srcType.parameterCount());
 326         // Calculate extra arguments (temporaries) required in the names array.
 327         Object[] convSpecs = computeValueConversions(srcType, target.type(), strict, monobox);
 328         final int INARG_COUNT = srcType.parameterCount();
 329         int convCount = countNonNull(convSpecs);
 330         boolean retConv = (convSpecs[INARG_COUNT] != null);
 331         boolean retVoid = srcType.returnType() == void.class;
 332         if (retConv && retVoid) {
 333             convCount -= 1;
 334             retConv = false;
 335         }
 336 
 337         final int IN_MH         = 0;
 338         final int INARG_BASE    = 1;
 339         final int INARG_LIMIT   = INARG_BASE + INARG_COUNT;
 340         final int NAME_LIMIT    = INARG_LIMIT + convCount + 1;
 341         final int RETURN_CONV   = (!retConv ? -1         : NAME_LIMIT - 1);
 342         final int OUT_CALL      = (!retConv ? NAME_LIMIT : RETURN_CONV) - 1;
 343         final int RESULT        = (retVoid ? -1 : NAME_LIMIT - 1);
 344 
 345         // Now build a LambdaForm.
 346         MethodType lambdaType = srcType.basicType().invokerType();
 347         Name[] names = arguments(NAME_LIMIT - INARG_LIMIT, lambdaType);
 348 
 349         // Collect the arguments to the outgoing call, maybe with conversions:
 350         final int OUTARG_BASE = 0;  // target MH is Name.function, name Name.arguments[0]
 351         Object[] outArgs = new Object[OUTARG_BASE + INARG_COUNT];
 352 
 353         int nameCursor = INARG_LIMIT;
 354         for (int i = 0; i < INARG_COUNT; i++) {
 355             Object convSpec = convSpecs[i];
 356             if (convSpec == null) {
 357                 // do nothing: difference is trivial
 358                 outArgs[OUTARG_BASE + i] = names[INARG_BASE + i];
 359                 continue;
 360             }
 361 
 362             Name conv;
 363             if (convSpec instanceof Class) {
 364                 Class<?> convClass = (Class<?>) convSpec;
 365                 conv = new Name(getConstantHandle(MH_cast), convClass, names[INARG_BASE + i]);
 366             } else {
 367                 MethodHandle fn = (MethodHandle) convSpec;
 368                 conv = new Name(fn, names[INARG_BASE + i]);
 369             }
 370             assert(names[nameCursor] == null);
 371             names[nameCursor++] = conv;
 372             assert(outArgs[OUTARG_BASE + i] == null);
 373             outArgs[OUTARG_BASE + i] = conv;
 374         }
 375 
 376         // Build argument array for the call.
 377         assert(nameCursor == OUT_CALL);
 378         names[OUT_CALL] = new Name(target, outArgs);
 379 
 380         Object convSpec = convSpecs[INARG_COUNT];
 381         if (!retConv) {
 382             assert(OUT_CALL == names.length-1);
 383         } else {
 384             Name conv;
 385             if (convSpec == void.class) {
 386                 conv = new Name(LambdaForm.constantZero(BasicType.basicType(srcType.returnType())));
 387             } else if (convSpec instanceof Class) {
 388                 Class<?> convClass = (Class<?>) convSpec;
 389                 conv = new Name(getConstantHandle(MH_cast), convClass, names[OUT_CALL]);
 390             } else {
 391                 MethodHandle fn = (MethodHandle) convSpec;
 392                 if (fn.type().parameterCount() == 0)
 393                     conv = new Name(fn);  // don't pass retval to void conversion
 394                 else
 395                     conv = new Name(fn, names[OUT_CALL]);
 396             }
 397             assert(names[RETURN_CONV] == null);
 398             names[RETURN_CONV] = conv;
 399             assert(RETURN_CONV == names.length-1);
 400         }
 401 
 402         LambdaForm form = new LambdaForm(lambdaType.parameterCount(), names, RESULT, Kind.CONVERT);
 403         return SimpleMethodHandle.make(srcType, form);
 404     }
 405 
 406     static Object[] computeValueConversions(MethodType srcType, MethodType dstType,
 407                                             boolean strict, boolean monobox) {
 408         final int INARG_COUNT = srcType.parameterCount();
 409         Object[] convSpecs = new Object[INARG_COUNT+1];
 410         for (int i = 0; i <= INARG_COUNT; i++) {
 411             boolean isRet = (i == INARG_COUNT);
 412             Class<?> src = isRet ? dstType.returnType() : srcType.parameterType(i);
 413             Class<?> dst = isRet ? srcType.returnType() : dstType.parameterType(i);
 414             if (!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict)) {
 415                 convSpecs[i] = valueConversion(src, dst, strict, monobox);
 416             }
 417         }
 418         return convSpecs;
 419     }
 420     static MethodHandle makePairwiseConvert(MethodHandle target, MethodType srcType,
 421                                             boolean strict) {
 422         return makePairwiseConvert(target, srcType, strict, /*monobox=*/ false);
 423     }
 424 
 425     /**
 426      * Find a conversion function from the given source to the given destination.
 427      * This conversion function will be used as a LF NamedFunction.
 428      * Return a Class object if a simple cast is needed.
 429      * Return void.class if void is involved.
 430      */
 431     static Object valueConversion(Class<?> src, Class<?> dst, boolean strict, boolean monobox) {
 432         assert(!VerifyType.isNullConversion(src, dst, /*keepInterfaces=*/ strict));  // caller responsibility
 433         if (dst == void.class)
 434             return dst;
 435         MethodHandle fn;
 436         if (src.isPrimitive()) {
 437             if (src == void.class) {
 438                 return void.class;  // caller must recognize this specially
 439             } else if (dst.isPrimitive()) {
 440                 // Examples: int->byte, byte->int, boolean->int (!strict)
 441                 fn = ValueConversions.convertPrimitive(src, dst);
 442             } else {
 443                 // Examples: int->Integer, boolean->Object, float->Number
 444                 Wrapper wsrc = Wrapper.forPrimitiveType(src);
 445                 fn = ValueConversions.boxExact(wsrc);
 446                 assert(fn.type().parameterType(0) == wsrc.primitiveType());
 447                 assert(fn.type().returnType() == wsrc.wrapperType());
 448                 if (!VerifyType.isNullConversion(wsrc.wrapperType(), dst, strict)) {
 449                     // Corner case, such as int->Long, which will probably fail.
 450                     MethodType mt = MethodType.methodType(dst, src);
 451                     if (strict)
 452                         fn = fn.asType(mt);
 453                     else
 454                         fn = MethodHandleImpl.makePairwiseConvert(fn, mt, /*strict=*/ false);
 455                 }
 456             }
 457         } else if (dst.isPrimitive()) {
 458             Wrapper wdst = Wrapper.forPrimitiveType(dst);
 459             if (monobox || src == wdst.wrapperType()) {
 460                 // Use a strongly-typed unboxer, if possible.
 461                 fn = ValueConversions.unboxExact(wdst, strict);
 462             } else {
 463                 // Examples:  Object->int, Number->int, Comparable->int, Byte->int
 464                 // must include additional conversions
 465                 // src must be examined at runtime, to detect Byte, Character, etc.
 466                 fn = (strict
 467                         ? ValueConversions.unboxWiden(wdst)
 468                         : ValueConversions.unboxCast(wdst));
 469             }
 470         } else {
 471             // Simple reference conversion.
 472             // Note:  Do not check for a class hierarchy relation
 473             // between src and dst.  In all cases a 'null' argument
 474             // will pass the cast conversion.
 475             return dst;
 476         }
 477         assert(fn.type().parameterCount() <= 1) : "pc"+Arrays.asList(src.getSimpleName(), dst.getSimpleName(), fn);
 478         return fn;
 479     }
 480 
 481     static MethodHandle makeVarargsCollector(MethodHandle target, Class<?> arrayType) {
 482         MethodType type = target.type();
 483         int last = type.parameterCount() - 1;
 484         if (type.parameterType(last) != arrayType)
 485             target = target.asType(type.changeParameterType(last, arrayType));
 486         target = target.asFixedArity();  // make sure this attribute is turned off
 487         return new AsVarargsCollector(target, arrayType);
 488     }
 489 
 490     private static final class AsVarargsCollector extends DelegatingMethodHandle {
 491         private final MethodHandle target;
 492         private final Class<?> arrayType;
 493         private @Stable MethodHandle asCollectorCache;
 494 
 495         AsVarargsCollector(MethodHandle target, Class<?> arrayType) {
 496             this(target.type(), target, arrayType);
 497         }
 498         AsVarargsCollector(MethodType type, MethodHandle target, Class<?> arrayType) {
 499             super(type, target);
 500             this.target = target;
 501             this.arrayType = arrayType;
 502             this.asCollectorCache = target.asCollector(arrayType, 0);
 503         }
 504 
 505         @Override
 506         public boolean isVarargsCollector() {
 507             return true;
 508         }
 509 
 510         @Override
 511         protected MethodHandle getTarget() {
 512             return target;
 513         }
 514 
 515         @Override
 516         public MethodHandle asFixedArity() {
 517             return target;
 518         }
 519 
 520         @Override
 521         MethodHandle setVarargs(MemberName member) {
 522             if (member.isVarargs())  return this;
 523             return asFixedArity();
 524         }
 525 
 526         @Override
 527         public MethodHandle withVarargs(boolean makeVarargs) {
 528             if (makeVarargs)  return this;
 529             return asFixedArity();
 530         }
 531 
 532         @Override
 533         public MethodHandle asTypeUncached(MethodType newType) {
 534             MethodType type = this.type();
 535             int collectArg = type.parameterCount() - 1;
 536             int newArity = newType.parameterCount();
 537             if (newArity == collectArg+1 &&
 538                 type.parameterType(collectArg).isAssignableFrom(newType.parameterType(collectArg))) {
 539                 // if arity and trailing parameter are compatible, do normal thing
 540                 return asTypeCache = asFixedArity().asType(newType);
 541             }
 542             // check cache
 543             MethodHandle acc = asCollectorCache;
 544             if (acc != null && acc.type().parameterCount() == newArity)
 545                 return asTypeCache = acc.asType(newType);
 546             // build and cache a collector
 547             int arrayLength = newArity - collectArg;
 548             MethodHandle collector;
 549             try {
 550                 collector = asFixedArity().asCollector(arrayType, arrayLength);
 551                 assert(collector.type().parameterCount() == newArity) : "newArity="+newArity+" but collector="+collector;
 552             } catch (IllegalArgumentException ex) {
 553                 throw new WrongMethodTypeException("cannot build collector", ex);
 554             }
 555             asCollectorCache = collector;
 556             return asTypeCache = collector.asType(newType);
 557         }
 558 
 559         @Override
 560         boolean viewAsTypeChecks(MethodType newType, boolean strict) {
 561             super.viewAsTypeChecks(newType, true);
 562             if (strict) return true;
 563             // extra assertion for non-strict checks:
 564             assert (type().lastParameterType().getComponentType()
 565                     .isAssignableFrom(
 566                             newType.lastParameterType().getComponentType()))
 567                     : Arrays.asList(this, newType);
 568             return true;
 569         }
 570 
 571         @Override
 572         public Object invokeWithArguments(Object... arguments) throws Throwable {
 573             MethodType type = this.type();
 574             int argc;
 575             final int MAX_SAFE = 127;  // 127 longs require 254 slots, which is safe to spread
 576             if (arguments == null
 577                     || (argc = arguments.length) <= MAX_SAFE
 578                     || argc < type.parameterCount()) {
 579                 return super.invokeWithArguments(arguments);
 580             }
 581 
 582             // a jumbo invocation requires more explicit reboxing of the trailing arguments
 583             int uncollected = type.parameterCount() - 1;
 584             Class<?> elemType = arrayType.getComponentType();
 585             int collected = argc - uncollected;
 586             Object collArgs = (elemType == Object.class)
 587                 ? new Object[collected] : Array.newInstance(elemType, collected);
 588             if (!elemType.isPrimitive()) {
 589                 // simple cast:  just do some casting
 590                 try {
 591                     System.arraycopy(arguments, uncollected, collArgs, 0, collected);
 592                 } catch (ArrayStoreException ex) {
 593                     return super.invokeWithArguments(arguments);
 594                 }
 595             } else {
 596                 // corner case of flat array requires reflection (or specialized copy loop)
 597                 MethodHandle arraySetter = MethodHandles.arrayElementSetter(arrayType);
 598                 try {
 599                     for (int i = 0; i < collected; i++) {
 600                         arraySetter.invoke(collArgs, i, arguments[uncollected + i]);
 601                     }
 602                 } catch (WrongMethodTypeException|ClassCastException ex) {
 603                     return super.invokeWithArguments(arguments);
 604                 }
 605             }
 606 
 607             // chop the jumbo list down to size and call in non-varargs mode
 608             Object[] newArgs = new Object[uncollected + 1];
 609             System.arraycopy(arguments, 0, newArgs, 0, uncollected);
 610             newArgs[uncollected] = collArgs;
 611             return asFixedArity().invokeWithArguments(newArgs);
 612         }
 613     }
 614 
 615     /** Factory method:  Spread selected argument. */
 616     static MethodHandle makeSpreadArguments(MethodHandle target,
 617                                             Class<?> spreadArgType, int spreadArgPos, int spreadArgCount) {
 618         MethodType targetType = target.type();
 619 
 620         for (int i = 0; i < spreadArgCount; i++) {
 621             Class<?> arg = VerifyType.spreadArgElementType(spreadArgType, i);
 622             if (arg == null)  arg = Object.class;
 623             targetType = targetType.changeParameterType(spreadArgPos + i, arg);
 624         }
 625         target = target.asType(targetType);
 626 
 627         MethodType srcType = targetType
 628                 .replaceParameterTypes(spreadArgPos, spreadArgPos + spreadArgCount, spreadArgType);
 629         // Now build a LambdaForm.
 630         MethodType lambdaType = srcType.invokerType();
 631         Name[] names = arguments(spreadArgCount + 2, lambdaType);
 632         int nameCursor = lambdaType.parameterCount();
 633         int[] indexes = new int[targetType.parameterCount()];
 634 
 635         for (int i = 0, argIndex = 1; i < targetType.parameterCount() + 1; i++, argIndex++) {
 636             Class<?> src = lambdaType.parameterType(i);
 637             if (i == spreadArgPos) {
 638                 // Spread the array.
 639                 MethodHandle aload = MethodHandles.arrayElementGetter(spreadArgType);
 640                 Name array = names[argIndex];
 641                 names[nameCursor++] = new Name(getFunction(NF_checkSpreadArgument), array, spreadArgCount);
 642                 for (int j = 0; j < spreadArgCount; i++, j++) {
 643                     indexes[i] = nameCursor;
 644                     names[nameCursor++] = new Name(new NamedFunction(aload, Intrinsic.ARRAY_LOAD), array, j);
 645                 }
 646             } else if (i < indexes.length) {
 647                 indexes[i] = argIndex;
 648             }
 649         }
 650         assert(nameCursor == names.length-1);  // leave room for the final call
 651 
 652         // Build argument array for the call.
 653         Name[] targetArgs = new Name[targetType.parameterCount()];
 654         for (int i = 0; i < targetType.parameterCount(); i++) {
 655             int idx = indexes[i];
 656             targetArgs[i] = names[idx];
 657         }
 658         names[names.length - 1] = new Name(target, (Object[]) targetArgs);
 659 
 660         LambdaForm form = new LambdaForm(lambdaType.parameterCount(), names, Kind.SPREAD);
 661         return SimpleMethodHandle.make(srcType, form);
 662     }
 663 
 664     static void checkSpreadArgument(Object av, int n) {
 665         if (av == null && n == 0) {
 666             return;
 667         } else if (av == null) {
 668             throw new NullPointerException("null array reference");
 669         } else if (av instanceof Object[]) {
 670             int len = ((Object[])av).length;
 671             if (len == n)  return;
 672         } else {
 673             int len = java.lang.reflect.Array.getLength(av);
 674             if (len == n)  return;
 675         }
 676         // fall through to error:
 677         throw newIllegalArgumentException("array is not of length "+n);
 678     }
 679 
 680     /** Factory method:  Collect or filter selected argument(s). */
 681     static MethodHandle makeCollectArguments(MethodHandle target,
 682                 MethodHandle collector, int collectArgPos, boolean retainOriginalArgs) {
 683         MethodType targetType = target.type();          // (a..., c, [b...])=>r
 684         MethodType collectorType = collector.type();    // (b...)=>c
 685         int collectArgCount = collectorType.parameterCount();
 686         Class<?> collectValType = collectorType.returnType();
 687         int collectValCount = (collectValType == void.class ? 0 : 1);
 688         MethodType srcType = targetType                 // (a..., [b...])=>r
 689                 .dropParameterTypes(collectArgPos, collectArgPos+collectValCount);
 690         if (!retainOriginalArgs) {                      // (a..., b...)=>r
 691             srcType = srcType.insertParameterTypes(collectArgPos, collectorType.parameterArray());
 692         }
 693         // in  arglist: [0: ...keep1 | cpos: collect...  | cpos+cacount: keep2... ]
 694         // out arglist: [0: ...keep1 | cpos: collectVal? | cpos+cvcount: keep2... ]
 695         // out(retain): [0: ...keep1 | cpos: cV? coll... | cpos+cvc+cac: keep2... ]
 696 
 697         // Now build a LambdaForm.
 698         MethodType lambdaType = srcType.invokerType();
 699         Name[] names = arguments(2, lambdaType);
 700         final int collectNamePos = names.length - 2;
 701         final int targetNamePos  = names.length - 1;
 702 
 703         Name[] collectorArgs = Arrays.copyOfRange(names, 1 + collectArgPos, 1 + collectArgPos + collectArgCount);
 704         names[collectNamePos] = new Name(collector, (Object[]) collectorArgs);
 705 
 706         // Build argument array for the target.
 707         // Incoming LF args to copy are: [ (mh) headArgs collectArgs tailArgs ].
 708         // Output argument array is [ headArgs (collectVal)? (collectArgs)? tailArgs ].
 709         Name[] targetArgs = new Name[targetType.parameterCount()];
 710         int inputArgPos  = 1;  // incoming LF args to copy to target
 711         int targetArgPos = 0;  // fill pointer for targetArgs
 712         int chunk = collectArgPos;  // |headArgs|
 713         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 714         inputArgPos  += chunk;
 715         targetArgPos += chunk;
 716         if (collectValType != void.class) {
 717             targetArgs[targetArgPos++] = names[collectNamePos];
 718         }
 719         chunk = collectArgCount;
 720         if (retainOriginalArgs) {
 721             System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 722             targetArgPos += chunk;   // optionally pass on the collected chunk
 723         }
 724         inputArgPos += chunk;
 725         chunk = targetArgs.length - targetArgPos;  // all the rest
 726         System.arraycopy(names, inputArgPos, targetArgs, targetArgPos, chunk);
 727         assert(inputArgPos + chunk == collectNamePos);  // use of rest of input args also
 728         names[targetNamePos] = new Name(target, (Object[]) targetArgs);
 729 
 730         LambdaForm form = new LambdaForm(lambdaType.parameterCount(), names, Kind.COLLECT);
 731         return SimpleMethodHandle.make(srcType, form);
 732     }
 733 
 734     @LambdaForm.Hidden
 735     static
 736     MethodHandle selectAlternative(boolean testResult, MethodHandle target, MethodHandle fallback) {
 737         if (testResult) {
 738             return target;
 739         } else {
 740             return fallback;
 741         }
 742     }
 743 
 744     // Intrinsified by C2. Counters are used during parsing to calculate branch frequencies.
 745     @LambdaForm.Hidden
 746     @jdk.internal.HotSpotIntrinsicCandidate
 747     static
 748     boolean profileBoolean(boolean result, int[] counters) {
 749         // Profile is int[2] where [0] and [1] correspond to false and true occurrences respectively.
 750         int idx = result ? 1 : 0;
 751         try {
 752             counters[idx] = Math.addExact(counters[idx], 1);
 753         } catch (ArithmeticException e) {
 754             // Avoid continuous overflow by halving the problematic count.
 755             counters[idx] = counters[idx] / 2;
 756         }
 757         return result;
 758     }
 759 
 760     // Intrinsified by C2. Returns true if obj is a compile-time constant.
 761     @LambdaForm.Hidden
 762     @jdk.internal.HotSpotIntrinsicCandidate
 763     static
 764     boolean isCompileConstant(Object obj) {
 765         return false;
 766     }
 767 
 768     static
 769     MethodHandle makeGuardWithTest(MethodHandle test,
 770                                    MethodHandle target,
 771                                    MethodHandle fallback) {
 772         MethodType type = target.type();
 773         assert(test.type().equals(type.changeReturnType(boolean.class)) && fallback.type().equals(type));
 774         MethodType basicType = type.basicType();
 775         LambdaForm form = makeGuardWithTestForm(basicType);
 776         BoundMethodHandle mh;
 777         try {
 778             if (PROFILE_GWT) {
 779                 int[] counts = new int[2];
 780                 mh = (BoundMethodHandle)
 781                         BoundMethodHandle.speciesData_LLLL().factory().invokeBasic(type, form,
 782                                 (Object) test, (Object) profile(target), (Object) profile(fallback), counts);
 783             } else {
 784                 mh = (BoundMethodHandle)
 785                         BoundMethodHandle.speciesData_LLL().factory().invokeBasic(type, form,
 786                                 (Object) test, (Object) profile(target), (Object) profile(fallback));
 787             }
 788         } catch (Throwable ex) {
 789             throw uncaughtException(ex);
 790         }
 791         assert(mh.type() == type);
 792         return mh;
 793     }
 794 
 795 
 796     static
 797     MethodHandle profile(MethodHandle target) {
 798         if (DONT_INLINE_THRESHOLD >= 0) {
 799             return makeBlockInliningWrapper(target);
 800         } else {
 801             return target;
 802         }
 803     }
 804 
 805     /**
 806      * Block inlining during JIT-compilation of a target method handle if it hasn't been invoked enough times.
 807      * Corresponding LambdaForm has @DontInline when compiled into bytecode.
 808      */
 809     static
 810     MethodHandle makeBlockInliningWrapper(MethodHandle target) {
 811         LambdaForm lform;
 812         if (DONT_INLINE_THRESHOLD > 0) {
 813             lform = Makers.PRODUCE_BLOCK_INLINING_FORM.apply(target);
 814         } else {
 815             lform = Makers.PRODUCE_REINVOKER_FORM.apply(target);
 816         }
 817         return new CountingWrapper(target, lform,
 818                 Makers.PRODUCE_BLOCK_INLINING_FORM, Makers.PRODUCE_REINVOKER_FORM,
 819                                    DONT_INLINE_THRESHOLD);
 820     }
 821 
 822     private final static class Makers {
 823         /** Constructs reinvoker lambda form which block inlining during JIT-compilation for a particular method handle */
 824         static final Function<MethodHandle, LambdaForm> PRODUCE_BLOCK_INLINING_FORM = new Function<MethodHandle, LambdaForm>() {
 825             @Override
 826             public LambdaForm apply(MethodHandle target) {
 827                 return DelegatingMethodHandle.makeReinvokerForm(target,
 828                                    MethodTypeForm.LF_DELEGATE_BLOCK_INLINING, CountingWrapper.class, false,
 829                                    DelegatingMethodHandle.NF_getTarget, CountingWrapper.NF_maybeStopCounting);
 830             }
 831         };
 832 
 833         /** Constructs simple reinvoker lambda form for a particular method handle */
 834         static final Function<MethodHandle, LambdaForm> PRODUCE_REINVOKER_FORM = new Function<MethodHandle, LambdaForm>() {
 835             @Override
 836             public LambdaForm apply(MethodHandle target) {
 837                 return DelegatingMethodHandle.makeReinvokerForm(target,
 838                         MethodTypeForm.LF_DELEGATE, DelegatingMethodHandle.class, DelegatingMethodHandle.NF_getTarget);
 839             }
 840         };
 841 
 842         /** Maker of type-polymorphic varargs */
 843         static final ClassValue<MethodHandle[]> TYPED_COLLECTORS = new ClassValue<MethodHandle[]>() {
 844             @Override
 845             protected MethodHandle[] computeValue(Class<?> type) {
 846                 return new MethodHandle[MAX_JVM_ARITY + 1];
 847             }
 848         };
 849     }
 850 
 851     /**
 852      * Counting method handle. It has 2 states: counting and non-counting.
 853      * It is in counting state for the first n invocations and then transitions to non-counting state.
 854      * Behavior in counting and non-counting states is determined by lambda forms produced by
 855      * countingFormProducer & nonCountingFormProducer respectively.
 856      */
 857     static class CountingWrapper extends DelegatingMethodHandle {
 858         private final MethodHandle target;
 859         private int count;
 860         private Function<MethodHandle, LambdaForm> countingFormProducer;
 861         private Function<MethodHandle, LambdaForm> nonCountingFormProducer;
 862         private volatile boolean isCounting;
 863 
 864         private CountingWrapper(MethodHandle target, LambdaForm lform,
 865                                 Function<MethodHandle, LambdaForm> countingFromProducer,
 866                                 Function<MethodHandle, LambdaForm> nonCountingFormProducer,
 867                                 int count) {
 868             super(target.type(), lform);
 869             this.target = target;
 870             this.count = count;
 871             this.countingFormProducer = countingFromProducer;
 872             this.nonCountingFormProducer = nonCountingFormProducer;
 873             this.isCounting = (count > 0);
 874         }
 875 
 876         @Hidden
 877         @Override
 878         protected MethodHandle getTarget() {
 879             return target;
 880         }
 881 
 882         @Override
 883         public MethodHandle asTypeUncached(MethodType newType) {
 884             MethodHandle newTarget = target.asType(newType);
 885             MethodHandle wrapper;
 886             if (isCounting) {
 887                 LambdaForm lform;
 888                 lform = countingFormProducer.apply(newTarget);
 889                 wrapper = new CountingWrapper(newTarget, lform, countingFormProducer, nonCountingFormProducer, DONT_INLINE_THRESHOLD);
 890             } else {
 891                 wrapper = newTarget; // no need for a counting wrapper anymore
 892             }
 893             return (asTypeCache = wrapper);
 894         }
 895 
 896         // Customize target if counting happens for too long.
 897         private int invocations = CUSTOMIZE_THRESHOLD;
 898         private void maybeCustomizeTarget() {
 899             int c = invocations;
 900             if (c >= 0) {
 901                 if (c == 1) {
 902                     target.customize();
 903                 }
 904                 invocations = c - 1;
 905             }
 906         }
 907 
 908         boolean countDown() {
 909             int c = count;
 910             maybeCustomizeTarget();
 911             if (c <= 1) {
 912                 // Try to limit number of updates. MethodHandle.updateForm() doesn't guarantee LF update visibility.
 913                 if (isCounting) {
 914                     isCounting = false;
 915                     return true;
 916                 } else {
 917                     return false;
 918                 }
 919             } else {
 920                 count = c - 1;
 921                 return false;
 922             }
 923         }
 924 
 925         @Hidden
 926         static void maybeStopCounting(Object o1) {
 927              CountingWrapper wrapper = (CountingWrapper) o1;
 928              if (wrapper.countDown()) {
 929                  // Reached invocation threshold. Replace counting behavior with a non-counting one.
 930                  LambdaForm lform = wrapper.nonCountingFormProducer.apply(wrapper.target);
 931                  lform.compileToBytecode(); // speed up warmup by avoiding LF interpretation again after transition
 932                  wrapper.updateForm(lform);
 933              }
 934         }
 935 
 936         static final NamedFunction NF_maybeStopCounting;
 937         static {
 938             Class<?> THIS_CLASS = CountingWrapper.class;
 939             try {
 940                 NF_maybeStopCounting = new NamedFunction(THIS_CLASS.getDeclaredMethod("maybeStopCounting", Object.class));
 941             } catch (ReflectiveOperationException ex) {
 942                 throw newInternalError(ex);
 943             }
 944         }
 945     }
 946 
 947     static
 948     LambdaForm makeGuardWithTestForm(MethodType basicType) {
 949         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWT);
 950         if (lform != null)  return lform;
 951         final int THIS_MH      = 0;  // the BMH_LLL
 952         final int ARG_BASE     = 1;  // start of incoming arguments
 953         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
 954         int nameCursor = ARG_LIMIT;
 955         final int GET_TEST     = nameCursor++;
 956         final int GET_TARGET   = nameCursor++;
 957         final int GET_FALLBACK = nameCursor++;
 958         final int GET_COUNTERS = PROFILE_GWT ? nameCursor++ : -1;
 959         final int CALL_TEST    = nameCursor++;
 960         final int PROFILE      = (GET_COUNTERS != -1) ? nameCursor++ : -1;
 961         final int TEST         = nameCursor-1; // previous statement: either PROFILE or CALL_TEST
 962         final int SELECT_ALT   = nameCursor++;
 963         final int CALL_TARGET  = nameCursor++;
 964         assert(CALL_TARGET == SELECT_ALT+1);  // must be true to trigger IBG.emitSelectAlternative
 965 
 966         MethodType lambdaType = basicType.invokerType();
 967         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
 968 
 969         BoundMethodHandle.SpeciesData data =
 970                 (GET_COUNTERS != -1) ? BoundMethodHandle.speciesData_LLLL()
 971                                      : BoundMethodHandle.speciesData_LLL();
 972         names[THIS_MH] = names[THIS_MH].withConstraint(data);
 973         names[GET_TEST]     = new Name(data.getterFunction(0), names[THIS_MH]);
 974         names[GET_TARGET]   = new Name(data.getterFunction(1), names[THIS_MH]);
 975         names[GET_FALLBACK] = new Name(data.getterFunction(2), names[THIS_MH]);
 976         if (GET_COUNTERS != -1) {
 977             names[GET_COUNTERS] = new Name(data.getterFunction(3), names[THIS_MH]);
 978         }
 979         Object[] invokeArgs = Arrays.copyOfRange(names, 0, ARG_LIMIT, Object[].class);
 980 
 981         // call test
 982         MethodType testType = basicType.changeReturnType(boolean.class).basicType();
 983         invokeArgs[0] = names[GET_TEST];
 984         names[CALL_TEST] = new Name(testType, invokeArgs);
 985 
 986         // profile branch
 987         if (PROFILE != -1) {
 988             names[PROFILE] = new Name(getFunction(NF_profileBoolean), names[CALL_TEST], names[GET_COUNTERS]);
 989         }
 990         // call selectAlternative
 991         names[SELECT_ALT] = new Name(new NamedFunction(getConstantHandle(MH_selectAlternative), Intrinsic.SELECT_ALTERNATIVE), names[TEST], names[GET_TARGET], names[GET_FALLBACK]);
 992 
 993         // call target or fallback
 994         invokeArgs[0] = names[SELECT_ALT];
 995         names[CALL_TARGET] = new Name(basicType, invokeArgs);
 996 
 997         lform = new LambdaForm(lambdaType.parameterCount(), names, /*forceInline=*/true, Kind.GUARD);
 998 
 999         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWT, lform);
1000     }
1001 
1002     /**
1003      * The LambdaForm shape for catchException combinator is the following:
1004      * <blockquote><pre>{@code
1005      *  guardWithCatch=Lambda(a0:L,a1:L,a2:L)=>{
1006      *    t3:L=BoundMethodHandle$Species_LLLLL.argL0(a0:L);
1007      *    t4:L=BoundMethodHandle$Species_LLLLL.argL1(a0:L);
1008      *    t5:L=BoundMethodHandle$Species_LLLLL.argL2(a0:L);
1009      *    t6:L=BoundMethodHandle$Species_LLLLL.argL3(a0:L);
1010      *    t7:L=BoundMethodHandle$Species_LLLLL.argL4(a0:L);
1011      *    t8:L=MethodHandle.invokeBasic(t6:L,a1:L,a2:L);
1012      *    t9:L=MethodHandleImpl.guardWithCatch(t3:L,t4:L,t5:L,t8:L);
1013      *   t10:I=MethodHandle.invokeBasic(t7:L,t9:L);t10:I}
1014      * }</pre></blockquote>
1015      *
1016      * argL0 and argL2 are target and catcher method handles. argL1 is exception class.
1017      * argL3 and argL4 are auxiliary method handles: argL3 boxes arguments and wraps them into Object[]
1018      * (ValueConversions.array()) and argL4 unboxes result if necessary (ValueConversions.unbox()).
1019      *
1020      * Having t8 and t10 passed outside and not hardcoded into a lambda form allows to share lambda forms
1021      * among catchException combinators with the same basic type.
1022      */
1023     private static LambdaForm makeGuardWithCatchForm(MethodType basicType) {
1024         MethodType lambdaType = basicType.invokerType();
1025 
1026         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_GWC);
1027         if (lform != null) {
1028             return lform;
1029         }
1030         final int THIS_MH      = 0;  // the BMH_LLLLL
1031         final int ARG_BASE     = 1;  // start of incoming arguments
1032         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
1033 
1034         int nameCursor = ARG_LIMIT;
1035         final int GET_TARGET       = nameCursor++;
1036         final int GET_CLASS        = nameCursor++;
1037         final int GET_CATCHER      = nameCursor++;
1038         final int GET_COLLECT_ARGS = nameCursor++;
1039         final int GET_UNBOX_RESULT = nameCursor++;
1040         final int BOXED_ARGS       = nameCursor++;
1041         final int TRY_CATCH        = nameCursor++;
1042         final int UNBOX_RESULT     = nameCursor++;
1043 
1044         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
1045 
1046         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
1047         names[THIS_MH]          = names[THIS_MH].withConstraint(data);
1048         names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
1049         names[GET_CLASS]        = new Name(data.getterFunction(1), names[THIS_MH]);
1050         names[GET_CATCHER]      = new Name(data.getterFunction(2), names[THIS_MH]);
1051         names[GET_COLLECT_ARGS] = new Name(data.getterFunction(3), names[THIS_MH]);
1052         names[GET_UNBOX_RESULT] = new Name(data.getterFunction(4), names[THIS_MH]);
1053 
1054         // FIXME: rework argument boxing/result unboxing logic for LF interpretation
1055 
1056         // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
1057         MethodType collectArgsType = basicType.changeReturnType(Object.class);
1058         MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
1059         Object[] args = new Object[invokeBasic.type().parameterCount()];
1060         args[0] = names[GET_COLLECT_ARGS];
1061         System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
1062         names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.GUARD_WITH_CATCH), args);
1063 
1064         // t_{i+1}:L=MethodHandleImpl.guardWithCatch(target:L,exType:L,catcher:L,t_{i}:L);
1065         Object[] gwcArgs = new Object[] {names[GET_TARGET], names[GET_CLASS], names[GET_CATCHER], names[BOXED_ARGS]};
1066         names[TRY_CATCH] = new Name(getFunction(NF_guardWithCatch), gwcArgs);
1067 
1068         // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
1069         MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
1070         Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_CATCH]};
1071         names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);
1072 
1073         lform = new LambdaForm(lambdaType.parameterCount(), names, Kind.GUARD_WITH_CATCH);
1074 
1075         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_GWC, lform);
1076     }
1077 
1078     static
1079     MethodHandle makeGuardWithCatch(MethodHandle target,
1080                                     Class<? extends Throwable> exType,
1081                                     MethodHandle catcher) {
1082         MethodType type = target.type();
1083         LambdaForm form = makeGuardWithCatchForm(type.basicType());
1084 
1085         // Prepare auxiliary method handles used during LambdaForm interpretation.
1086         // Box arguments and wrap them into Object[]: ValueConversions.array().
1087         MethodType varargsType = type.changeReturnType(Object[].class);
1088         MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
1089         MethodHandle unboxResult = unboxResultHandle(type.returnType());
1090 
1091         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLLL();
1092         BoundMethodHandle mh;
1093         try {
1094             mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) target, (Object) exType,
1095                     (Object) catcher, (Object) collectArgs, (Object) unboxResult);
1096         } catch (Throwable ex) {
1097             throw uncaughtException(ex);
1098         }
1099         assert(mh.type() == type);
1100         return mh;
1101     }
1102 
1103     /**
1104      * Intrinsified during LambdaForm compilation
1105      * (see {@link InvokerBytecodeGenerator#emitGuardWithCatch emitGuardWithCatch}).
1106      */
1107     @LambdaForm.Hidden
1108     static Object guardWithCatch(MethodHandle target, Class<? extends Throwable> exType, MethodHandle catcher,
1109                                  Object... av) throws Throwable {
1110         // Use asFixedArity() to avoid unnecessary boxing of last argument for VarargsCollector case.
1111         try {
1112             return target.asFixedArity().invokeWithArguments(av);
1113         } catch (Throwable t) {
1114             if (!exType.isInstance(t)) throw t;
1115             return catcher.asFixedArity().invokeWithArguments(prepend(av, t));
1116         }
1117     }
1118 
1119     /** Prepend elements to an array. */
1120     @LambdaForm.Hidden
1121     private static Object[] prepend(Object[] array, Object... elems) {
1122         int nArray = array.length;
1123         int nElems = elems.length;
1124         Object[] newArray = new Object[nArray + nElems];
1125         System.arraycopy(elems, 0, newArray, 0, nElems);
1126         System.arraycopy(array, 0, newArray, nElems, nArray);
1127         return newArray;
1128     }
1129 
1130     static
1131     MethodHandle throwException(MethodType type) {
1132         assert(Throwable.class.isAssignableFrom(type.parameterType(0)));
1133         int arity = type.parameterCount();
1134         if (arity > 1) {
1135             MethodHandle mh = throwException(type.dropParameterTypes(1, arity));
1136             mh = MethodHandles.dropArguments(mh, 1, Arrays.copyOfRange(type.parameterArray(), 1, arity));
1137             return mh;
1138         }
1139         return makePairwiseConvert(getFunction(NF_throwException).resolvedHandle(), type, false, true);
1140     }
1141 
1142     static <T extends Throwable> Empty throwException(T t) throws T { throw t; }
1143 
1144     static MethodHandle[] FAKE_METHOD_HANDLE_INVOKE = new MethodHandle[2];
1145     static MethodHandle fakeMethodHandleInvoke(MemberName method) {
1146         int idx;
1147         assert(method.isMethodHandleInvoke());
1148         switch (method.getName()) {
1149         case "invoke":       idx = 0; break;
1150         case "invokeExact":  idx = 1; break;
1151         default:             throw new InternalError(method.getName());
1152         }
1153         MethodHandle mh = FAKE_METHOD_HANDLE_INVOKE[idx];
1154         if (mh != null)  return mh;
1155         MethodType type = MethodType.methodType(Object.class, UnsupportedOperationException.class,
1156                                                 MethodHandle.class, Object[].class);
1157         mh = throwException(type);
1158         mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke MethodHandle"));
1159         if (!method.getInvocationType().equals(mh.type()))
1160             throw new InternalError(method.toString());
1161         mh = mh.withInternalMemberName(method, false);
1162         mh = mh.withVarargs(true);
1163         assert(method.isVarargs());
1164         FAKE_METHOD_HANDLE_INVOKE[idx] = mh;
1165         return mh;
1166     }
1167     static MethodHandle fakeVarHandleInvoke(MemberName method) {
1168         // TODO caching, is it necessary?
1169         MethodType type = MethodType.methodType(method.getReturnType(), UnsupportedOperationException.class,
1170                                                 VarHandle.class, Object[].class);
1171         MethodHandle mh = throwException(type);
1172         mh = mh.bindTo(new UnsupportedOperationException("cannot reflectively invoke VarHandle"));
1173         if (!method.getInvocationType().equals(mh.type()))
1174             throw new InternalError(method.toString());
1175         mh = mh.withInternalMemberName(method, false);
1176         mh = mh.asVarargsCollector(Object[].class);
1177         assert(method.isVarargs());
1178         return mh;
1179     }
1180 
1181     /**
1182      * Create an alias for the method handle which, when called,
1183      * appears to be called from the same class loader and protection domain
1184      * as hostClass.
1185      * This is an expensive no-op unless the method which is called
1186      * is sensitive to its caller.  A small number of system methods
1187      * are in this category, including Class.forName and Method.invoke.
1188      */
1189     static
1190     MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1191         return BindCaller.bindCaller(mh, hostClass);
1192     }
1193 
1194     // Put the whole mess into its own nested class.
1195     // That way we can lazily load the code and set up the constants.
1196     private static class BindCaller {
1197         private static MethodType INVOKER_MT = MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1198 
1199         static
1200         MethodHandle bindCaller(MethodHandle mh, Class<?> hostClass) {
1201             // Code in the boot layer should now be careful while creating method handles or
1202             // functional interface instances created from method references to @CallerSensitive  methods,
1203             // it needs to be ensured the handles or interface instances are kept safe and are not passed
1204             // from the boot layer to untrusted code.
1205             if (hostClass == null
1206                 ||    (hostClass.isArray() ||
1207                        hostClass.isPrimitive() ||
1208                        hostClass.getName().startsWith("java.lang.invoke."))) {
1209                 throw new InternalError();  // does not happen, and should not anyway
1210             }
1211             // For simplicity, convert mh to a varargs-like method.
1212             MethodHandle vamh = prepareForInvoker(mh);
1213             // Cache the result of makeInjectedInvoker once per argument class.
1214             MethodHandle bccInvoker = CV_makeInjectedInvoker.get(hostClass);
1215             return restoreToType(bccInvoker.bindTo(vamh), mh, hostClass);
1216         }
1217 
1218         private static MethodHandle makeInjectedInvoker(Class<?> hostClass) {
1219             try {
1220                 Class<?> invokerClass = UNSAFE.defineAnonymousClass(hostClass, INJECTED_INVOKER_TEMPLATE, null);
1221                 assert checkInjectedInvoker(hostClass, invokerClass);
1222                 return IMPL_LOOKUP.findStatic(invokerClass, "invoke_V", INVOKER_MT);
1223             } catch (ReflectiveOperationException ex) {
1224                 throw uncaughtException(ex);
1225             }
1226         }
1227 
1228         private static ClassValue<MethodHandle> CV_makeInjectedInvoker = new ClassValue<MethodHandle>() {
1229             @Override protected MethodHandle computeValue(Class<?> hostClass) {
1230                 return makeInjectedInvoker(hostClass);
1231             }
1232         };
1233 
1234         // Adapt mh so that it can be called directly from an injected invoker:
1235         private static MethodHandle prepareForInvoker(MethodHandle mh) {
1236             mh = mh.asFixedArity();
1237             MethodType mt = mh.type();
1238             int arity = mt.parameterCount();
1239             MethodHandle vamh = mh.asType(mt.generic());
1240             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1241             vamh = vamh.asSpreader(Object[].class, arity);
1242             vamh.internalForm().compileToBytecode();  // eliminate LFI stack frames
1243             return vamh;
1244         }
1245 
1246         // Undo the adapter effect of prepareForInvoker:
1247         private static MethodHandle restoreToType(MethodHandle vamh,
1248                                                   MethodHandle original,
1249                                                   Class<?> hostClass) {
1250             MethodType type = original.type();
1251             MethodHandle mh = vamh.asCollector(Object[].class, type.parameterCount());
1252             MemberName member = original.internalMemberName();
1253             mh = mh.asType(type);
1254             mh = new WrappedMember(mh, type, member, original.isInvokeSpecial(), hostClass);
1255             return mh;
1256         }
1257 
1258         private static boolean checkInjectedInvoker(Class<?> hostClass, Class<?> invokerClass) {
1259             assert (hostClass.getClassLoader() == invokerClass.getClassLoader()) : hostClass.getName()+" (CL)";
1260             try {
1261                 assert (hostClass.getProtectionDomain() == invokerClass.getProtectionDomain()) : hostClass.getName()+" (PD)";
1262             } catch (SecurityException ex) {
1263                 // Self-check was blocked by security manager. This is OK.
1264             }
1265             try {
1266                 // Test the invoker to ensure that it really injects into the right place.
1267                 MethodHandle invoker = IMPL_LOOKUP.findStatic(invokerClass, "invoke_V", INVOKER_MT);
1268                 MethodHandle vamh = prepareForInvoker(MH_checkCallerClass);
1269                 return (boolean)invoker.invoke(vamh, new Object[]{ invokerClass });
1270             } catch (Throwable ex) {
1271                 throw new InternalError(ex);
1272             }
1273         }
1274 
1275         private static final MethodHandle MH_checkCallerClass;
1276         static {
1277             final Class<?> THIS_CLASS = BindCaller.class;
1278             assert(checkCallerClass(THIS_CLASS));
1279             try {
1280                 MH_checkCallerClass = IMPL_LOOKUP
1281                     .findStatic(THIS_CLASS, "checkCallerClass",
1282                                 MethodType.methodType(boolean.class, Class.class));
1283                 assert((boolean) MH_checkCallerClass.invokeExact(THIS_CLASS));
1284             } catch (Throwable ex) {
1285                 throw new InternalError(ex);
1286             }
1287         }
1288 
1289         @CallerSensitive
1290         @ForceInline // to ensure Reflection.getCallerClass optimization
1291         private static boolean checkCallerClass(Class<?> expected) {
1292             // This method is called via MH_checkCallerClass and so it's correct to ask for the immediate caller here.
1293             Class<?> actual = Reflection.getCallerClass();
1294             if (actual != expected)
1295                 throw new InternalError("found " + actual.getName() + ", expected " + expected.getName());
1296             return true;
1297         }
1298 
1299         private static final byte[] INJECTED_INVOKER_TEMPLATE = generateInvokerTemplate();
1300 
1301         /** Produces byte code for a class that is used as an injected invoker. */
1302         private static byte[] generateInvokerTemplate() {
1303             ClassWriter cw = new ClassWriter(0);
1304 
1305             // private static class InjectedInvoker {
1306             //     @Hidden
1307             //     static Object invoke_V(MethodHandle vamh, Object[] args) throws Throwable {
1308             //        return vamh.invokeExact(args);
1309             //     }
1310             // }
1311             cw.visit(52, ACC_PRIVATE | ACC_SUPER, "InjectedInvoker", null, "java/lang/Object", null);
1312 
1313             MethodVisitor mv = cw.visitMethod(ACC_STATIC, "invoke_V",
1314                           "(Ljava/lang/invoke/MethodHandle;[Ljava/lang/Object;)Ljava/lang/Object;",
1315                           null, null);
1316 
1317             // Suppress invoker method in stack traces.
1318             AnnotationVisitor av0 = mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);
1319             av0.visitEnd();
1320 
1321             mv.visitCode();
1322             mv.visitVarInsn(ALOAD, 0);
1323             mv.visitVarInsn(ALOAD, 1);
1324             mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/invoke/MethodHandle", "invokeExact",
1325                                "([Ljava/lang/Object;)Ljava/lang/Object;", false);
1326             mv.visitInsn(ARETURN);
1327             mv.visitMaxs(2, 2);
1328             mv.visitEnd();
1329 
1330             cw.visitEnd();
1331             return cw.toByteArray();
1332         }
1333     }
1334 
1335     /** This subclass allows a wrapped method handle to be re-associated with an arbitrary member name. */
1336     private static final class WrappedMember extends DelegatingMethodHandle {
1337         private final MethodHandle target;
1338         private final MemberName member;
1339         private final Class<?> callerClass;
1340         private final boolean isInvokeSpecial;
1341 
1342         private WrappedMember(MethodHandle target, MethodType type,
1343                               MemberName member, boolean isInvokeSpecial,
1344                               Class<?> callerClass) {
1345             super(type, target);
1346             this.target = target;
1347             this.member = member;
1348             this.callerClass = callerClass;
1349             this.isInvokeSpecial = isInvokeSpecial;
1350         }
1351 
1352         @Override
1353         MemberName internalMemberName() {
1354             return member;
1355         }
1356         @Override
1357         Class<?> internalCallerClass() {
1358             return callerClass;
1359         }
1360         @Override
1361         boolean isInvokeSpecial() {
1362             return isInvokeSpecial;
1363         }
1364         @Override
1365         protected MethodHandle getTarget() {
1366             return target;
1367         }
1368         @Override
1369         public MethodHandle asTypeUncached(MethodType newType) {
1370             // This MH is an alias for target, except for the MemberName
1371             // Drop the MemberName if there is any conversion.
1372             return asTypeCache = target.asType(newType);
1373         }
1374     }
1375 
1376     static MethodHandle makeWrappedMember(MethodHandle target, MemberName member, boolean isInvokeSpecial) {
1377         if (member.equals(target.internalMemberName()) && isInvokeSpecial == target.isInvokeSpecial())
1378             return target;
1379         return new WrappedMember(target, target.type(), member, isInvokeSpecial, null);
1380     }
1381 
1382     /** Intrinsic IDs */
1383     /*non-public*/
1384     enum Intrinsic {
1385         SELECT_ALTERNATIVE,
1386         GUARD_WITH_CATCH,
1387         TRY_FINALLY,
1388         LOOP,
1389         NEW_ARRAY,
1390         ARRAY_LOAD,
1391         ARRAY_STORE,
1392         ARRAY_LENGTH,
1393         IDENTITY,
1394         ZERO,
1395         NONE // no intrinsic associated
1396     }
1397 
1398     /** Mark arbitrary method handle as intrinsic.
1399      * InvokerBytecodeGenerator uses this info to produce more efficient bytecode shape. */
1400     static final class IntrinsicMethodHandle extends DelegatingMethodHandle {
1401         private final MethodHandle target;
1402         private final Intrinsic intrinsicName;
1403 
1404         IntrinsicMethodHandle(MethodHandle target, Intrinsic intrinsicName) {
1405             super(target.type(), target);
1406             this.target = target;
1407             this.intrinsicName = intrinsicName;
1408         }
1409 
1410         @Override
1411         protected MethodHandle getTarget() {
1412             return target;
1413         }
1414 
1415         @Override
1416         Intrinsic intrinsicName() {
1417             return intrinsicName;
1418         }
1419 
1420         @Override
1421         public MethodHandle asTypeUncached(MethodType newType) {
1422             // This MH is an alias for target, except for the intrinsic name
1423             // Drop the name if there is any conversion.
1424             return asTypeCache = target.asType(newType);
1425         }
1426 
1427         @Override
1428         String internalProperties() {
1429             return super.internalProperties() +
1430                     "\n& Intrinsic="+intrinsicName;
1431         }
1432 
1433         @Override
1434         public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
1435             if (intrinsicName == Intrinsic.IDENTITY) {
1436                 MethodType resultType = type().asCollectorType(arrayType, type().parameterCount() - 1, arrayLength);
1437                 MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
1438                 return newArray.asType(resultType);
1439             }
1440             return super.asCollector(arrayType, arrayLength);
1441         }
1442     }
1443 
1444     static MethodHandle makeIntrinsic(MethodHandle target, Intrinsic intrinsicName) {
1445         if (intrinsicName == target.intrinsicName())
1446             return target;
1447         return new IntrinsicMethodHandle(target, intrinsicName);
1448     }
1449 
1450     static MethodHandle makeIntrinsic(MethodType type, LambdaForm form, Intrinsic intrinsicName) {
1451         return new IntrinsicMethodHandle(SimpleMethodHandle.make(type, form), intrinsicName);
1452     }
1453 
1454     /// Collection of multiple arguments.
1455 
1456     private static MethodHandle findCollector(String name, int nargs, Class<?> rtype, Class<?>... ptypes) {
1457         MethodType type = MethodType.genericMethodType(nargs)
1458                 .changeReturnType(rtype)
1459                 .insertParameterTypes(0, ptypes);
1460         try {
1461             return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, name, type);
1462         } catch (ReflectiveOperationException ex) {
1463             return null;
1464         }
1465     }
1466 
1467     private static final Object[] NO_ARGS_ARRAY = {};
1468     private static Object[] makeArray(Object... args) { return args; }
1469     private static Object[] array() { return NO_ARGS_ARRAY; }
1470     private static Object[] array(Object a0)
1471                 { return makeArray(a0); }
1472     private static Object[] array(Object a0, Object a1)
1473                 { return makeArray(a0, a1); }
1474     private static Object[] array(Object a0, Object a1, Object a2)
1475                 { return makeArray(a0, a1, a2); }
1476     private static Object[] array(Object a0, Object a1, Object a2, Object a3)
1477                 { return makeArray(a0, a1, a2, a3); }
1478     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1479                                   Object a4)
1480                 { return makeArray(a0, a1, a2, a3, a4); }
1481     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1482                                   Object a4, Object a5)
1483                 { return makeArray(a0, a1, a2, a3, a4, a5); }
1484     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1485                                   Object a4, Object a5, Object a6)
1486                 { return makeArray(a0, a1, a2, a3, a4, a5, a6); }
1487     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1488                                   Object a4, Object a5, Object a6, Object a7)
1489                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7); }
1490     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1491                                   Object a4, Object a5, Object a6, Object a7,
1492                                   Object a8)
1493                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8); }
1494     private static Object[] array(Object a0, Object a1, Object a2, Object a3,
1495                                   Object a4, Object a5, Object a6, Object a7,
1496                                   Object a8, Object a9)
1497                 { return makeArray(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); }
1498 
1499     private static final int ARRAYS_COUNT = 11;
1500     private static final @Stable MethodHandle[] ARRAYS = new MethodHandle[MAX_ARITY + 1];
1501 
1502     // filling versions of the above:
1503     // using Integer len instead of int len and no varargs to avoid bootstrapping problems
1504     private static Object[] fillNewArray(Integer len, Object[] /*not ...*/ args) {
1505         Object[] a = new Object[len];
1506         fillWithArguments(a, 0, args);
1507         return a;
1508     }
1509     private static Object[] fillNewTypedArray(Object[] example, Integer len, Object[] /*not ...*/ args) {
1510         Object[] a = Arrays.copyOf(example, len);
1511         assert(a.getClass() != Object[].class);
1512         fillWithArguments(a, 0, args);
1513         return a;
1514     }
1515     private static void fillWithArguments(Object[] a, int pos, Object... args) {
1516         System.arraycopy(args, 0, a, pos, args.length);
1517     }
1518     // using Integer pos instead of int pos to avoid bootstrapping problems
1519     private static Object[] fillArray(Integer pos, Object[] a, Object a0)
1520                 { fillWithArguments(a, pos, a0); return a; }
1521     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1)
1522                 { fillWithArguments(a, pos, a0, a1); return a; }
1523     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2)
1524                 { fillWithArguments(a, pos, a0, a1, a2); return a; }
1525     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3)
1526                 { fillWithArguments(a, pos, a0, a1, a2, a3); return a; }
1527     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1528                                   Object a4)
1529                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4); return a; }
1530     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1531                                   Object a4, Object a5)
1532                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5); return a; }
1533     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1534                                   Object a4, Object a5, Object a6)
1535                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6); return a; }
1536     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1537                                   Object a4, Object a5, Object a6, Object a7)
1538                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7); return a; }
1539     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1540                                   Object a4, Object a5, Object a6, Object a7,
1541                                   Object a8)
1542                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8); return a; }
1543     private static Object[] fillArray(Integer pos, Object[] a, Object a0, Object a1, Object a2, Object a3,
1544                                   Object a4, Object a5, Object a6, Object a7,
1545                                   Object a8, Object a9)
1546                 { fillWithArguments(a, pos, a0, a1, a2, a3, a4, a5, a6, a7, a8, a9); return a; }
1547 
1548     private static final int FILL_ARRAYS_COUNT = 11; // current number of fillArray methods
1549     private static final @Stable MethodHandle[] FILL_ARRAYS = new MethodHandle[FILL_ARRAYS_COUNT];
1550 
1551     private static MethodHandle getFillArray(int count) {
1552         assert (count > 0 && count < FILL_ARRAYS_COUNT);
1553         MethodHandle mh = FILL_ARRAYS[count];
1554         if (mh != null) {
1555             return mh;
1556         }
1557         mh = findCollector("fillArray", count, Object[].class, Integer.class, Object[].class);
1558         FILL_ARRAYS[count] = mh;
1559         return mh;
1560     }
1561 
1562     private static Object copyAsPrimitiveArray(Wrapper w, Object... boxes) {
1563         Object a = w.makeArray(boxes.length);
1564         w.copyArrayUnboxing(boxes, 0, a, 0, boxes.length);
1565         return a;
1566     }
1567 
1568     /** Return a method handle that takes the indicated number of Object
1569      *  arguments and returns an Object array of them, as if for varargs.
1570      */
1571     static MethodHandle varargsArray(int nargs) {
1572         MethodHandle mh = ARRAYS[nargs];
1573         if (mh != null) {
1574             return mh;
1575         }
1576         if (nargs < ARRAYS_COUNT) {
1577             mh = findCollector("array", nargs, Object[].class);
1578         } else {
1579             mh = buildVarargsArray(getConstantHandle(MH_fillNewArray),
1580                     getConstantHandle(MH_arrayIdentity), nargs);
1581         }
1582         assert(assertCorrectArity(mh, nargs));
1583         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1584         return ARRAYS[nargs] = mh;
1585     }
1586 
1587     private static boolean assertCorrectArity(MethodHandle mh, int arity) {
1588         assert(mh.type().parameterCount() == arity) : "arity != "+arity+": "+mh;
1589         return true;
1590     }
1591 
1592     // Array identity function (used as getConstantHandle(MH_arrayIdentity)).
1593     static <T> T[] identity(T[] x) {
1594         return x;
1595     }
1596 
1597     private static MethodHandle buildVarargsArray(MethodHandle newArray, MethodHandle finisher, int nargs) {
1598         // Build up the result mh as a sequence of fills like this:
1599         //   finisher(fill(fill(newArrayWA(23,x1..x10),10,x11..x20),20,x21..x23))
1600         // The various fill(_,10*I,___*[J]) are reusable.
1601         int leftLen = Math.min(nargs, LEFT_ARGS);  // absorb some arguments immediately
1602         int rightLen = nargs - leftLen;
1603         MethodHandle leftCollector = newArray.bindTo(nargs);
1604         leftCollector = leftCollector.asCollector(Object[].class, leftLen);
1605         MethodHandle mh = finisher;
1606         if (rightLen > 0) {
1607             MethodHandle rightFiller = fillToRight(LEFT_ARGS + rightLen);
1608             if (mh.equals(getConstantHandle(MH_arrayIdentity)))
1609                 mh = rightFiller;
1610             else
1611                 mh = MethodHandles.collectArguments(mh, 0, rightFiller);
1612         }
1613         if (mh.equals(getConstantHandle(MH_arrayIdentity)))
1614             mh = leftCollector;
1615         else
1616             mh = MethodHandles.collectArguments(mh, 0, leftCollector);
1617         return mh;
1618     }
1619 
1620     private static final int LEFT_ARGS = FILL_ARRAYS_COUNT - 1;
1621     private static final @Stable MethodHandle[] FILL_ARRAY_TO_RIGHT = new MethodHandle[MAX_ARITY + 1];
1622     /** fill_array_to_right(N).invoke(a, argL..arg[N-1])
1623      *  fills a[L]..a[N-1] with corresponding arguments,
1624      *  and then returns a.  The value L is a global constant (LEFT_ARGS).
1625      */
1626     private static MethodHandle fillToRight(int nargs) {
1627         MethodHandle filler = FILL_ARRAY_TO_RIGHT[nargs];
1628         if (filler != null)  return filler;
1629         filler = buildFiller(nargs);
1630         assert(assertCorrectArity(filler, nargs - LEFT_ARGS + 1));
1631         return FILL_ARRAY_TO_RIGHT[nargs] = filler;
1632     }
1633     private static MethodHandle buildFiller(int nargs) {
1634         if (nargs <= LEFT_ARGS)
1635             return getConstantHandle(MH_arrayIdentity);  // no args to fill; return the array unchanged
1636         // we need room for both mh and a in mh.invoke(a, arg*[nargs])
1637         final int CHUNK = LEFT_ARGS;
1638         int rightLen = nargs % CHUNK;
1639         int midLen = nargs - rightLen;
1640         if (rightLen == 0) {
1641             midLen = nargs - (rightLen = CHUNK);
1642             if (FILL_ARRAY_TO_RIGHT[midLen] == null) {
1643                 // build some precursors from left to right
1644                 for (int j = LEFT_ARGS % CHUNK; j < midLen; j += CHUNK)
1645                     if (j > LEFT_ARGS)  fillToRight(j);
1646             }
1647         }
1648         if (midLen < LEFT_ARGS) rightLen = nargs - (midLen = LEFT_ARGS);
1649         assert(rightLen > 0);
1650         MethodHandle midFill = fillToRight(midLen);  // recursive fill
1651         MethodHandle rightFill = getFillArray(rightLen).bindTo(midLen);  // [midLen..nargs-1]
1652         assert(midFill.type().parameterCount()   == 1 + midLen - LEFT_ARGS);
1653         assert(rightFill.type().parameterCount() == 1 + rightLen);
1654 
1655         // Combine the two fills:
1656         //   right(mid(a, x10..x19), x20..x23)
1657         // The final product will look like this:
1658         //   right(mid(newArrayLeft(24, x0..x9), x10..x19), x20..x23)
1659         if (midLen == LEFT_ARGS)
1660             return rightFill;
1661         else
1662             return MethodHandles.collectArguments(rightFill, 0, midFill);
1663     }
1664 
1665     static final int MAX_JVM_ARITY = 255;  // limit imposed by the JVM
1666 
1667     /** Return a method handle that takes the indicated number of
1668      *  typed arguments and returns an array of them.
1669      *  The type argument is the array type.
1670      */
1671     static MethodHandle varargsArray(Class<?> arrayType, int nargs) {
1672         Class<?> elemType = arrayType.getComponentType();
1673         if (elemType == null)  throw new IllegalArgumentException("not an array: "+arrayType);
1674         // FIXME: Need more special casing and caching here.
1675         if (nargs >= MAX_JVM_ARITY/2 - 1) {
1676             int slots = nargs;
1677             final int MAX_ARRAY_SLOTS = MAX_JVM_ARITY - 1;  // 1 for receiver MH
1678             if (slots <= MAX_ARRAY_SLOTS && elemType.isPrimitive())
1679                 slots *= Wrapper.forPrimitiveType(elemType).stackSlots();
1680             if (slots > MAX_ARRAY_SLOTS)
1681                 throw new IllegalArgumentException("too many arguments: "+arrayType.getSimpleName()+", length "+nargs);
1682         }
1683         if (elemType == Object.class)
1684             return varargsArray(nargs);
1685         // other cases:  primitive arrays, subtypes of Object[]
1686         MethodHandle cache[] = Makers.TYPED_COLLECTORS.get(elemType);
1687         MethodHandle mh = nargs < cache.length ? cache[nargs] : null;
1688         if (mh != null)  return mh;
1689         if (nargs == 0) {
1690             Object example = java.lang.reflect.Array.newInstance(arrayType.getComponentType(), 0);
1691             mh = MethodHandles.constant(arrayType, example);
1692         } else if (elemType.isPrimitive()) {
1693             MethodHandle builder = getConstantHandle(MH_fillNewArray);
1694             MethodHandle producer = buildArrayProducer(arrayType);
1695             mh = buildVarargsArray(builder, producer, nargs);
1696         } else {
1697             Class<? extends Object[]> objArrayType = arrayType.asSubclass(Object[].class);
1698             Object[] example = Arrays.copyOf(NO_ARGS_ARRAY, 0, objArrayType);
1699             MethodHandle builder = getConstantHandle(MH_fillNewTypedArray).bindTo(example);
1700             MethodHandle producer = getConstantHandle(MH_arrayIdentity); // must be weakly typed
1701             mh = buildVarargsArray(builder, producer, nargs);
1702         }
1703         mh = mh.asType(MethodType.methodType(arrayType, Collections.<Class<?>>nCopies(nargs, elemType)));
1704         mh = makeIntrinsic(mh, Intrinsic.NEW_ARRAY);
1705         assert(assertCorrectArity(mh, nargs));
1706         if (nargs < cache.length)
1707             cache[nargs] = mh;
1708         return mh;
1709     }
1710 
1711     private static MethodHandle buildArrayProducer(Class<?> arrayType) {
1712         Class<?> elemType = arrayType.getComponentType();
1713         assert(elemType.isPrimitive());
1714         return getConstantHandle(MH_copyAsPrimitiveArray).bindTo(Wrapper.forPrimitiveType(elemType));
1715     }
1716 
1717     /*non-public*/ static void assertSame(Object mh1, Object mh2) {
1718         if (mh1 != mh2) {
1719             String msg = String.format("mh1 != mh2: mh1 = %s (form: %s); mh2 = %s (form: %s)",
1720                     mh1, ((MethodHandle)mh1).form,
1721                     mh2, ((MethodHandle)mh2).form);
1722             throw newInternalError(msg);
1723         }
1724     }
1725 
1726     // Local constant functions:
1727 
1728     /* non-public */
1729     static final byte NF_checkSpreadArgument = 0,
1730             NF_guardWithCatch = 1,
1731             NF_throwException = 2,
1732             NF_tryFinally = 3,
1733             NF_loop = 4,
1734             NF_profileBoolean = 5,
1735             NF_LIMIT = 6;
1736 
1737     private static final @Stable NamedFunction[] NFS = new NamedFunction[NF_LIMIT];
1738 
1739     static NamedFunction getFunction(byte func) {
1740         NamedFunction nf = NFS[func];
1741         if (nf != null) {
1742             return nf;
1743         }
1744         return NFS[func] = createFunction(func);
1745     }
1746 
1747     private static NamedFunction createFunction(byte func) {
1748         try {
1749             switch (func) {
1750                 case NF_checkSpreadArgument:
1751                     return new NamedFunction(MethodHandleImpl.class
1752                             .getDeclaredMethod("checkSpreadArgument", Object.class, int.class));
1753                 case NF_guardWithCatch:
1754                     return new NamedFunction(MethodHandleImpl.class
1755                             .getDeclaredMethod("guardWithCatch", MethodHandle.class, Class.class,
1756                                     MethodHandle.class, Object[].class));
1757                 case NF_tryFinally:
1758                     return new NamedFunction(MethodHandleImpl.class
1759                             .getDeclaredMethod("tryFinally", MethodHandle.class, MethodHandle.class, Object[].class));
1760                 case NF_loop:
1761                     return new NamedFunction(MethodHandleImpl.class
1762                             .getDeclaredMethod("loop", BasicType[].class, LoopClauses.class, Object[].class));
1763                 case NF_throwException:
1764                     return new NamedFunction(MethodHandleImpl.class
1765                             .getDeclaredMethod("throwException", Throwable.class));
1766                 case NF_profileBoolean:
1767                     return new NamedFunction(MethodHandleImpl.class
1768                             .getDeclaredMethod("profileBoolean", boolean.class, int[].class));
1769                 default:
1770                     throw new InternalError("Undefined function: " + func);
1771             }
1772         } catch (ReflectiveOperationException ex) {
1773             throw newInternalError(ex);
1774         }
1775     }
1776 
1777     static {
1778         SharedSecrets.setJavaLangInvokeAccess(new JavaLangInvokeAccess() {
1779             @Override
1780             public Object newMemberName() {
1781                 return new MemberName();
1782             }
1783 
1784             @Override
1785             public String getName(Object mname) {
1786                 MemberName memberName = (MemberName)mname;
1787                 return memberName.getName();
1788             }
1789             @Override
1790             public Class<?> getDeclaringClass(Object mname) {
1791                 MemberName memberName = (MemberName)mname;
1792                 return memberName.getDeclaringClass();
1793             }
1794 
1795             @Override
1796             public MethodType getMethodType(Object mname) {
1797                 MemberName memberName = (MemberName)mname;
1798                 return memberName.getMethodType();
1799             }
1800 
1801             @Override
1802             public String getMethodDescriptor(Object mname) {
1803                 MemberName memberName = (MemberName)mname;
1804                 return memberName.getMethodDescriptor();
1805             }
1806 
1807             @Override
1808             public boolean isNative(Object mname) {
1809                 MemberName memberName = (MemberName)mname;
1810                 return memberName.isNative();
1811             }
1812 
1813             @Override
1814             public byte[] generateDirectMethodHandleHolderClassBytes(
1815                     String className, MethodType[] methodTypes, int[] types) {
1816                 return GenerateJLIClassesHelper
1817                         .generateDirectMethodHandleHolderClassBytes(
1818                                 className, methodTypes, types);
1819             }
1820 
1821             @Override
1822             public byte[] generateDelegatingMethodHandleHolderClassBytes(
1823                     String className, MethodType[] methodTypes) {
1824                 return GenerateJLIClassesHelper
1825                         .generateDelegatingMethodHandleHolderClassBytes(
1826                                 className, methodTypes);
1827             }
1828 
1829             @Override
1830             public Map.Entry<String, byte[]> generateConcreteBMHClassBytes(
1831                     final String types) {
1832                 return GenerateJLIClassesHelper
1833                         .generateConcreteBMHClassBytes(types);
1834             }
1835 
1836             @Override
1837             public byte[] generateBasicFormsClassBytes(final String className) {
1838                 return GenerateJLIClassesHelper
1839                         .generateBasicFormsClassBytes(className);
1840             }
1841 
1842             @Override
1843             public byte[] generateInvokersHolderClassBytes(final String className,
1844                     MethodType[] methodTypes) {
1845                 return GenerateJLIClassesHelper
1846                         .generateInvokersHolderClassBytes(className, methodTypes);
1847             }
1848         });
1849     }
1850 
1851     /** Result unboxing: ValueConversions.unbox() OR ValueConversions.identity() OR ValueConversions.ignore(). */
1852     private static MethodHandle unboxResultHandle(Class<?> returnType) {
1853         if (returnType.isPrimitive()) {
1854             if (returnType == void.class) {
1855                 return ValueConversions.ignore();
1856             } else {
1857                 Wrapper w = Wrapper.forPrimitiveType(returnType);
1858                 return ValueConversions.unboxExact(w);
1859             }
1860         } else {
1861             return MethodHandles.identity(Object.class);
1862         }
1863     }
1864 
1865     /**
1866      * Assembles a loop method handle from the given handles and type information.
1867      *
1868      * @param tloop the return type of the loop.
1869      * @param targs types of the arguments to be passed to the loop.
1870      * @param init sanitized array of initializers for loop-local variables.
1871      * @param step sanitited array of loop bodies.
1872      * @param pred sanitized array of predicates.
1873      * @param fini sanitized array of loop finalizers.
1874      *
1875      * @return a handle that, when invoked, will execute the loop.
1876      */
1877     static MethodHandle makeLoop(Class<?> tloop, List<Class<?>> targs, List<MethodHandle> init, List<MethodHandle> step,
1878                                  List<MethodHandle> pred, List<MethodHandle> fini) {
1879         MethodType type = MethodType.methodType(tloop, targs);
1880         BasicType[] initClauseTypes =
1881                 init.stream().map(h -> h.type().returnType()).map(BasicType::basicType).toArray(BasicType[]::new);
1882         LambdaForm form = makeLoopForm(type.basicType(), initClauseTypes);
1883 
1884         // Prepare auxiliary method handles used during LambdaForm interpretation.
1885         // Box arguments and wrap them into Object[]: ValueConversions.array().
1886         MethodType varargsType = type.changeReturnType(Object[].class);
1887         MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
1888         MethodHandle unboxResult = unboxResultHandle(tloop);
1889 
1890         LoopClauses clauseData =
1891                 new LoopClauses(new MethodHandle[][]{toArray(init), toArray(step), toArray(pred), toArray(fini)});
1892         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
1893         BoundMethodHandle mh;
1894         try {
1895             mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) clauseData,
1896                     (Object) collectArgs, (Object) unboxResult);
1897         } catch (Throwable ex) {
1898             throw uncaughtException(ex);
1899         }
1900         assert(mh.type() == type);
1901         return mh;
1902     }
1903 
1904     private static MethodHandle[] toArray(List<MethodHandle> l) {
1905         return l.toArray(new MethodHandle[0]);
1906     }
1907 
1908     /**
1909      * Loops introduce some complexity as they can have additional local state. Hence, LambdaForms for loops are
1910      * generated from a template. The LambdaForm template shape for the loop combinator is as follows (assuming one
1911      * reference parameter passed in {@code a1}, and a reference return type, with the return value represented by
1912      * {@code t12}):
1913      * <blockquote><pre>{@code
1914      *  loop=Lambda(a0:L,a1:L)=>{
1915      *    t2:L=BoundMethodHandle$Species_L3.argL0(a0:L);    // LoopClauses holding init, step, pred, fini handles
1916      *    t3:L=BoundMethodHandle$Species_L3.argL1(a0:L);    // helper handle to box the arguments into an Object[]
1917      *    t4:L=BoundMethodHandle$Species_L3.argL2(a0:L);    // helper handle to unbox the result
1918      *    t5:L=MethodHandle.invokeBasic(t3:L,a1:L);         // box the arguments into an Object[]
1919      *    t6:L=MethodHandleImpl.loop(null,t2:L,t3:L);       // call the loop executor
1920      *    t7:L=MethodHandle.invokeBasic(t4:L,t6:L);t7:L}    // unbox the result; return the result
1921      * }</pre></blockquote>
1922      * <p>
1923      * {@code argL0} is a LoopClauses instance holding, in a 2-dimensional array, the init, step, pred, and fini method
1924      * handles. {@code argL1} and {@code argL2} are auxiliary method handles: {@code argL1} boxes arguments and wraps
1925      * them into {@code Object[]} ({@code ValueConversions.array()}), and {@code argL2} unboxes the result if necessary
1926      * ({@code ValueConversions.unbox()}).
1927      * <p>
1928      * Having {@code t3} and {@code t4} passed in via a BMH and not hardcoded in the lambda form allows to share lambda
1929      * forms among loop combinators with the same basic type.
1930      * <p>
1931      * The above template is instantiated by using the {@link LambdaFormEditor} to replace the {@code null} argument to
1932      * the {@code loop} invocation with the {@code BasicType} array describing the loop clause types. This argument is
1933      * ignored in the loop invoker, but will be extracted and used in {@linkplain InvokerBytecodeGenerator#emitLoop(int)
1934      * bytecode generation}.
1935      */
1936     private static LambdaForm makeLoopForm(MethodType basicType, BasicType[] localVarTypes) {
1937         MethodType lambdaType = basicType.invokerType();
1938 
1939         final int THIS_MH = 0;  // the BMH_LLL
1940         final int ARG_BASE = 1; // start of incoming arguments
1941         final int ARG_LIMIT = ARG_BASE + basicType.parameterCount();
1942 
1943         int nameCursor = ARG_LIMIT;
1944         final int GET_CLAUSE_DATA = nameCursor++;
1945         final int GET_COLLECT_ARGS = nameCursor++;
1946         final int GET_UNBOX_RESULT = nameCursor++;
1947         final int BOXED_ARGS = nameCursor++;
1948         final int LOOP = nameCursor++;
1949         final int UNBOX_RESULT = nameCursor++;
1950 
1951         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_LOOP);
1952         if (lform == null) {
1953             Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
1954 
1955             BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLL();
1956             names[THIS_MH] = names[THIS_MH].withConstraint(data);
1957             names[GET_CLAUSE_DATA] = new Name(data.getterFunction(0), names[THIS_MH]);
1958             names[GET_COLLECT_ARGS] = new Name(data.getterFunction(1), names[THIS_MH]);
1959             names[GET_UNBOX_RESULT] = new Name(data.getterFunction(2), names[THIS_MH]);
1960 
1961             // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
1962             MethodType collectArgsType = basicType.changeReturnType(Object.class);
1963             MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
1964             Object[] args = new Object[invokeBasic.type().parameterCount()];
1965             args[0] = names[GET_COLLECT_ARGS];
1966             System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT - ARG_BASE);
1967             names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.LOOP), args);
1968 
1969             // t_{i+1}:L=MethodHandleImpl.loop(localTypes:L,clauses:L,t_{i}:L);
1970             Object[] lArgs =
1971                     new Object[]{null, // placeholder for BasicType[] localTypes - will be added by LambdaFormEditor
1972                             names[GET_CLAUSE_DATA], names[BOXED_ARGS]};
1973             names[LOOP] = new Name(getFunction(NF_loop), lArgs);
1974 
1975             // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
1976             MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
1977             Object[] unboxArgs = new Object[]{names[GET_UNBOX_RESULT], names[LOOP]};
1978             names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);
1979 
1980             lform = basicType.form().setCachedLambdaForm(MethodTypeForm.LF_LOOP,
1981                     new LambdaForm(lambdaType.parameterCount(), names, Kind.LOOP));
1982         }
1983 
1984         // BOXED_ARGS is the index into the names array where the loop idiom starts
1985         return lform.editor().noteLoopLocalTypesForm(BOXED_ARGS, localVarTypes);
1986     }
1987 
1988     static class LoopClauses {
1989         @Stable final MethodHandle[][] clauses;
1990         LoopClauses(MethodHandle[][] clauses) {
1991             assert clauses.length == 4;
1992             this.clauses = clauses;
1993         }
1994         @Override
1995         public String toString() {
1996             StringBuffer sb = new StringBuffer("LoopClauses -- ");
1997             for (int i = 0; i < 4; ++i) {
1998                 if (i > 0) {
1999                     sb.append("       ");
2000                 }
2001                 sb.append('<').append(i).append(">: ");
2002                 MethodHandle[] hs = clauses[i];
2003                 for (int j = 0; j < hs.length; ++j) {
2004                     if (j > 0) {
2005                         sb.append("          ");
2006                     }
2007                     sb.append('*').append(j).append(": ").append(hs[j]).append('\n');
2008                 }
2009             }
2010             sb.append(" --\n");
2011             return sb.toString();
2012         }
2013     }
2014 
2015     /**
2016      * Intrinsified during LambdaForm compilation
2017      * (see {@link InvokerBytecodeGenerator#emitLoop(int)}).
2018      */
2019     @LambdaForm.Hidden
2020     static Object loop(BasicType[] localTypes, LoopClauses clauseData, Object... av) throws Throwable {
2021         final MethodHandle[] init = clauseData.clauses[0];
2022         final MethodHandle[] step = clauseData.clauses[1];
2023         final MethodHandle[] pred = clauseData.clauses[2];
2024         final MethodHandle[] fini = clauseData.clauses[3];
2025         int varSize = (int) Stream.of(init).filter(h -> h.type().returnType() != void.class).count();
2026         int nArgs = init[0].type().parameterCount();
2027         Object[] varsAndArgs = new Object[varSize + nArgs];
2028         for (int i = 0, v = 0; i < init.length; ++i) {
2029             MethodHandle ih = init[i];
2030             if (ih.type().returnType() == void.class) {
2031                 ih.invokeWithArguments(av);
2032             } else {
2033                 varsAndArgs[v++] = ih.invokeWithArguments(av);
2034             }
2035         }
2036         System.arraycopy(av, 0, varsAndArgs, varSize, nArgs);
2037         final int nSteps = step.length;
2038         for (; ; ) {
2039             for (int i = 0, v = 0; i < nSteps; ++i) {
2040                 MethodHandle p = pred[i];
2041                 MethodHandle s = step[i];
2042                 MethodHandle f = fini[i];
2043                 if (s.type().returnType() == void.class) {
2044                     s.invokeWithArguments(varsAndArgs);
2045                 } else {
2046                     varsAndArgs[v++] = s.invokeWithArguments(varsAndArgs);
2047                 }
2048                 if (!(boolean) p.invokeWithArguments(varsAndArgs)) {
2049                     return f.invokeWithArguments(varsAndArgs);
2050                 }
2051             }
2052         }
2053     }
2054 
2055     /**
2056      * This method is bound as the predicate in {@linkplain MethodHandles#countedLoop(MethodHandle, MethodHandle,
2057      * MethodHandle) counting loops}.
2058      *
2059      * @param limit the upper bound of the parameter, statically bound at loop creation time.
2060      * @param counter the counter parameter, passed in during loop execution.
2061      *
2062      * @return whether the counter has reached the limit.
2063      */
2064     static boolean countedLoopPredicate(int limit, int counter) {
2065         return counter < limit;
2066     }
2067 
2068     /**
2069      * This method is bound as the step function in {@linkplain MethodHandles#countedLoop(MethodHandle, MethodHandle,
2070      * MethodHandle) counting loops} to increment the counter.
2071      *
2072      * @param limit the upper bound of the loop counter (ignored).
2073      * @param counter the loop counter.
2074      *
2075      * @return the loop counter incremented by 1.
2076      */
2077     static int countedLoopStep(int limit, int counter) {
2078         return counter + 1;
2079     }
2080 
2081     /**
2082      * This is bound to initialize the loop-local iterator in {@linkplain MethodHandles#iteratedLoop iterating loops}.
2083      *
2084      * @param it the {@link Iterable} over which the loop iterates.
2085      *
2086      * @return an {@link Iterator} over the argument's elements.
2087      */
2088     static Iterator<?> initIterator(Iterable<?> it) {
2089         return it.iterator();
2090     }
2091 
2092     /**
2093      * This method is bound as the predicate in {@linkplain MethodHandles#iteratedLoop iterating loops}.
2094      *
2095      * @param it the iterator to be checked.
2096      *
2097      * @return {@code true} iff there are more elements to iterate over.
2098      */
2099     static boolean iteratePredicate(Iterator<?> it) {
2100         return it.hasNext();
2101     }
2102 
2103     /**
2104      * This method is bound as the step for retrieving the current value from the iterator in {@linkplain
2105      * MethodHandles#iteratedLoop iterating loops}.
2106      *
2107      * @param it the iterator.
2108      *
2109      * @return the next element from the iterator.
2110      */
2111     static Object iterateNext(Iterator<?> it) {
2112         return it.next();
2113     }
2114 
2115     /**
2116      * Makes a {@code try-finally} handle that conforms to the type constraints.
2117      *
2118      * @param target the target to execute in a {@code try-finally} block.
2119      * @param cleanup the cleanup to execute in the {@code finally} block.
2120      * @param rtype the result type of the entire construct.
2121      * @param argTypes the types of the arguments.
2122      *
2123      * @return a handle on the constructed {@code try-finally} block.
2124      */
2125     static MethodHandle makeTryFinally(MethodHandle target, MethodHandle cleanup, Class<?> rtype, List<Class<?>> argTypes) {
2126         MethodType type = MethodType.methodType(rtype, argTypes);
2127         LambdaForm form = makeTryFinallyForm(type.basicType());
2128 
2129         // Prepare auxiliary method handles used during LambdaForm interpretation.
2130         // Box arguments and wrap them into Object[]: ValueConversions.array().
2131         MethodType varargsType = type.changeReturnType(Object[].class);
2132         MethodHandle collectArgs = varargsArray(type.parameterCount()).asType(varargsType);
2133         MethodHandle unboxResult = unboxResultHandle(rtype);
2134 
2135         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLL();
2136         BoundMethodHandle mh;
2137         try {
2138             mh = (BoundMethodHandle) data.factory().invokeBasic(type, form, (Object) target, (Object) cleanup,
2139                     (Object) collectArgs, (Object) unboxResult);
2140         } catch (Throwable ex) {
2141             throw uncaughtException(ex);
2142         }
2143         assert(mh.type() == type);
2144         return mh;
2145     }
2146 
2147     /**
2148      * The LambdaForm shape for the tryFinally combinator is as follows (assuming one reference parameter passed in
2149      * {@code a1}, and a reference return type, with the return value represented by {@code t8}):
2150      * <blockquote><pre>{@code
2151      *  tryFinally=Lambda(a0:L,a1:L)=>{
2152      *    t2:L=BoundMethodHandle$Species_LLLL.argL0(a0:L);  // target method handle
2153      *    t3:L=BoundMethodHandle$Species_LLLL.argL1(a0:L);  // cleanup method handle
2154      *    t4:L=BoundMethodHandle$Species_LLLL.argL2(a0:L);  // helper handle to box the arguments into an Object[]
2155      *    t5:L=BoundMethodHandle$Species_LLLL.argL3(a0:L);  // helper handle to unbox the result
2156      *    t6:L=MethodHandle.invokeBasic(t4:L,a1:L);         // box the arguments into an Object[]
2157      *    t7:L=MethodHandleImpl.tryFinally(t2:L,t3:L,t6:L); // call the tryFinally executor
2158      *    t8:L=MethodHandle.invokeBasic(t5:L,t7:L);t8:L}    // unbox the result; return the result
2159      * }</pre></blockquote>
2160      * <p>
2161      * {@code argL0} and {@code argL1} are the target and cleanup method handles.
2162      * {@code argL2} and {@code argL3} are auxiliary method handles: {@code argL2} boxes arguments and wraps them into
2163      * {@code Object[]} ({@code ValueConversions.array()}), and {@code argL3} unboxes the result if necessary
2164      * ({@code ValueConversions.unbox()}).
2165      * <p>
2166      * Having {@code t4} and {@code t5} passed in via a BMH and not hardcoded in the lambda form allows to share lambda
2167      * forms among tryFinally combinators with the same basic type.
2168      */
2169     private static LambdaForm makeTryFinallyForm(MethodType basicType) {
2170         MethodType lambdaType = basicType.invokerType();
2171 
2172         LambdaForm lform = basicType.form().cachedLambdaForm(MethodTypeForm.LF_TF);
2173         if (lform != null) {
2174             return lform;
2175         }
2176         final int THIS_MH      = 0;  // the BMH_LLLL
2177         final int ARG_BASE     = 1;  // start of incoming arguments
2178         final int ARG_LIMIT    = ARG_BASE + basicType.parameterCount();
2179 
2180         int nameCursor = ARG_LIMIT;
2181         final int GET_TARGET       = nameCursor++;
2182         final int GET_CLEANUP      = nameCursor++;
2183         final int GET_COLLECT_ARGS = nameCursor++;
2184         final int GET_UNBOX_RESULT = nameCursor++;
2185         final int BOXED_ARGS       = nameCursor++;
2186         final int TRY_FINALLY      = nameCursor++;
2187         final int UNBOX_RESULT     = nameCursor++;
2188 
2189         Name[] names = arguments(nameCursor - ARG_LIMIT, lambdaType);
2190 
2191         BoundMethodHandle.SpeciesData data = BoundMethodHandle.speciesData_LLLL();
2192         names[THIS_MH]          = names[THIS_MH].withConstraint(data);
2193         names[GET_TARGET]       = new Name(data.getterFunction(0), names[THIS_MH]);
2194         names[GET_CLEANUP]      = new Name(data.getterFunction(1), names[THIS_MH]);
2195         names[GET_COLLECT_ARGS] = new Name(data.getterFunction(2), names[THIS_MH]);
2196         names[GET_UNBOX_RESULT] = new Name(data.getterFunction(3), names[THIS_MH]);
2197 
2198         // t_{i}:L=MethodHandle.invokeBasic(collectArgs:L,a1:L,...);
2199         MethodType collectArgsType = basicType.changeReturnType(Object.class);
2200         MethodHandle invokeBasic = MethodHandles.basicInvoker(collectArgsType);
2201         Object[] args = new Object[invokeBasic.type().parameterCount()];
2202         args[0] = names[GET_COLLECT_ARGS];
2203         System.arraycopy(names, ARG_BASE, args, 1, ARG_LIMIT-ARG_BASE);
2204         names[BOXED_ARGS] = new Name(new NamedFunction(invokeBasic, Intrinsic.TRY_FINALLY), args);
2205 
2206         // t_{i+1}:L=MethodHandleImpl.tryFinally(target:L,exType:L,catcher:L,t_{i}:L);
2207         Object[] tfArgs = new Object[] {names[GET_TARGET], names[GET_CLEANUP], names[BOXED_ARGS]};
2208         names[TRY_FINALLY] = new Name(getFunction(NF_tryFinally), tfArgs);
2209 
2210         // t_{i+2}:I=MethodHandle.invokeBasic(unbox:L,t_{i+1}:L);
2211         MethodHandle invokeBasicUnbox = MethodHandles.basicInvoker(MethodType.methodType(basicType.rtype(), Object.class));
2212         Object[] unboxArgs  = new Object[] {names[GET_UNBOX_RESULT], names[TRY_FINALLY]};
2213         names[UNBOX_RESULT] = new Name(invokeBasicUnbox, unboxArgs);
2214 
2215         lform = new LambdaForm(lambdaType.parameterCount(), names, Kind.TRY_FINALLY);
2216 
2217         return basicType.form().setCachedLambdaForm(MethodTypeForm.LF_TF, lform);
2218     }
2219 
2220     /**
2221      * Intrinsified during LambdaForm compilation
2222      * (see {@link InvokerBytecodeGenerator#emitTryFinally emitTryFinally}).
2223      */
2224     @LambdaForm.Hidden
2225     static Object tryFinally(MethodHandle target, MethodHandle cleanup, Object... av) throws Throwable {
2226         Throwable t = null;
2227         Object r = null;
2228         try {
2229             r = target.invokeWithArguments(av);
2230         } catch (Throwable thrown) {
2231             t = thrown;
2232             throw t;
2233         } finally {
2234             Object[] args = target.type().returnType() == void.class ? prepend(av, t) : prepend(av, t, r);
2235             r = cleanup.invokeWithArguments(args);
2236         }
2237         return r;
2238     }
2239 
2240     // Indexes into constant method handles:
2241     static final int
2242             MH_cast                  =  0,
2243             MH_selectAlternative     =  1,
2244             MH_copyAsPrimitiveArray  =  2,
2245             MH_fillNewTypedArray     =  3,
2246             MH_fillNewArray          =  4,
2247             MH_arrayIdentity         =  5,
2248             MH_countedLoopPred       =  6,
2249             MH_countedLoopStep       =  7,
2250             MH_initIterator          =  8,
2251             MH_iteratePred           =  9,
2252             MH_iterateNext           = 10,
2253             MH_Array_newInstance     = 11,
2254             MH_LIMIT                 = 12;
2255 
2256     static MethodHandle getConstantHandle(int idx) {
2257         MethodHandle handle = HANDLES[idx];
2258         if (handle != null) {
2259             return handle;
2260         }
2261         return setCachedHandle(idx, makeConstantHandle(idx));
2262     }
2263 
2264     private static synchronized MethodHandle setCachedHandle(int idx, final MethodHandle method) {
2265         // Simulate a CAS, to avoid racy duplication of results.
2266         MethodHandle prev = HANDLES[idx];
2267         if (prev != null) {
2268             return prev;
2269         }
2270         HANDLES[idx] = method;
2271         return method;
2272     }
2273 
2274     // Local constant method handles:
2275     private static final @Stable MethodHandle[] HANDLES = new MethodHandle[MH_LIMIT];
2276 
2277     private static MethodHandle makeConstantHandle(int idx) {
2278         try {
2279             switch (idx) {
2280                 case MH_cast:
2281                     return IMPL_LOOKUP.findVirtual(Class.class, "cast",
2282                             MethodType.methodType(Object.class, Object.class));
2283                 case MH_copyAsPrimitiveArray:
2284                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "copyAsPrimitiveArray",
2285                             MethodType.methodType(Object.class, Wrapper.class, Object[].class));
2286                 case MH_arrayIdentity:
2287                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "identity",
2288                             MethodType.methodType(Object[].class, Object[].class));
2289                 case MH_fillNewArray:
2290                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "fillNewArray",
2291                             MethodType.methodType(Object[].class, Integer.class, Object[].class));
2292                 case MH_fillNewTypedArray:
2293                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "fillNewTypedArray",
2294                             MethodType.methodType(Object[].class, Object[].class, Integer.class, Object[].class));
2295                 case MH_selectAlternative:
2296                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "selectAlternative",
2297                             MethodType.methodType(MethodHandle.class, boolean.class, MethodHandle.class, MethodHandle.class));
2298                 case MH_countedLoopPred:
2299                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "countedLoopPredicate",
2300                             MethodType.methodType(boolean.class, int.class, int.class));
2301                 case MH_countedLoopStep:
2302                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "countedLoopStep",
2303                             MethodType.methodType(int.class, int.class, int.class));
2304                 case MH_initIterator:
2305                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "initIterator",
2306                             MethodType.methodType(Iterator.class, Iterable.class));
2307                 case MH_iteratePred:
2308                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "iteratePredicate",
2309                             MethodType.methodType(boolean.class, Iterator.class));
2310                 case MH_iterateNext:
2311                     return IMPL_LOOKUP.findStatic(MethodHandleImpl.class, "iterateNext",
2312                             MethodType.methodType(Object.class, Iterator.class));
2313                 case MH_Array_newInstance:
2314                     return IMPL_LOOKUP.findStatic(Array.class, "newInstance",
2315                             MethodType.methodType(Object.class, Class.class, int.class));
2316             }
2317         } catch (ReflectiveOperationException ex) {
2318             throw newInternalError(ex);
2319         }
2320         throw newInternalError("Unknown function index: " + idx);
2321     }
2322 }
--- EOF ---