1 /*
   2  * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.lang.invoke;
  27 
  28 import java.lang.annotation.*;
  29 import java.lang.reflect.Method;
  30 import java.util.Map;
  31 import java.util.List;
  32 import java.util.Arrays;
  33 import java.util.ArrayList;
  34 import java.util.HashMap;
  35 import java.util.concurrent.ConcurrentHashMap;
  36 import sun.invoke.util.Wrapper;
  37 import static java.lang.invoke.MethodHandleStatics.*;
  38 import static java.lang.invoke.MethodHandleNatives.Constants.*;
  39 import java.lang.reflect.Field;
  40 import java.util.Objects;
  41 
  42 /**
  43  * The symbolic, non-executable form of a method handle's invocation semantics.
  44  * It consists of a series of names.
  45  * The first N (N=arity) names are parameters,
  46  * while any remaining names are temporary values.
  47  * Each temporary specifies the application of a function to some arguments.
  48  * The functions are method handles, while the arguments are mixes of
  49  * constant values and local names.
  50  * The result of the lambda is defined as one of the names, often the last one.
  51  * <p>
  52  * Here is an approximate grammar:
  53  * <pre>
  54  * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"
  55  * ArgName = "a" N ":" T
  56  * TempName = "t" N ":" T "=" Function "(" Argument* ");"
  57  * Function = ConstantValue
  58  * Argument = NameRef | ConstantValue
  59  * Result = NameRef | "void"
  60  * NameRef = "a" N | "t" N
  61  * N = (any whole number)
  62  * T = "L" | "I" | "J" | "F" | "D" | "V"
  63  * </pre>
  64  * Names are numbered consecutively from left to right starting at zero.
  65  * (The letters are merely a taste of syntax sugar.)
  66  * Thus, the first temporary (if any) is always numbered N (where N=arity).
  67  * Every occurrence of a name reference in an argument list must refer to
  68  * a name previously defined within the same lambda.
  69  * A lambda has a void result if and only if its result index is -1.
  70  * If a temporary has the type "V", it cannot be the subject of a NameRef,
  71  * even though possesses a number.
  72  * Note that all reference types are erased to "L", which stands for {@code Object).
  73  * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.
  74  * The other types stand for the usual primitive types.
  75  * <p>
  76  * Function invocation closely follows the static rules of the Java verifier.
  77  * Arguments and return values must exactly match when their "Name" types are
  78  * considered.
  79  * Conversions are allowed only if they do not change the erased type.
  80  * <ul>
  81  * <li>L = Object: casts are used freely to convert into and out of reference types
  82  * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})
  83  * <li>J = long: no implicit conversions
  84  * <li>F = float: no implicit conversions
  85  * <li>D = double: no implicit conversions
  86  * <li>V = void: a function result may be void if and only if its Name is of type "V"
  87  * </ul>
  88  * Although implicit conversions are not allowed, explicit ones can easily be
  89  * encoded by using temporary expressions which call type-transformed identity functions.
  90  * <p>
  91  * Examples:
  92  * <pre>
  93  * (a0:J)=>{ a0 }
  94  *     == identity(long)
  95  * (a0:I)=>{ t1:V = System.out#println(a0); void }
  96  *     == System.out#println(int)
  97  * (a0:L)=>{ t1:V = System.out#println(a0); a0 }
  98  *     == identity, with printing side-effect
  99  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
 100  *                 t3:L = BoundMethodHandle#target(a0);
 101  *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }
 102  *     == general invoker for unary insertArgument combination
 103  * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);
 104  *                 t3:L = MethodHandle#invoke(t2, a1);
 105  *                 t4:L = FilterMethodHandle#target(a0);
 106  *                 t5:L = MethodHandle#invoke(t4, t3); t5 }
 107  *     == general invoker for unary filterArgument combination
 108  * (a0:L, a1:L)=>{ ...(same as previous example)...
 109  *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }
 110  *     == general invoker for unary/unary foldArgument combination
 111  * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }
 112  *     == invoker for identity method handle which performs i2l
 113  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
 114  *                 t3:L = Class#cast(t2,a1); t3 }
 115  *     == invoker for identity method handle which performs cast
 116  * </pre>
 117  * <p>
 118  * @author John Rose, JSR 292 EG
 119  */
 120 class LambdaForm {
 121     final int arity;
 122     final int result;
 123     final Name[] names;
 124     final String debugName;
 125     MemberName vmentry;   // low-level behavior, or null if not yet prepared
 126     private boolean isCompiled;
 127 
 128     // Caches for common structural transforms:
 129     LambdaForm[] bindCache;
 130 
 131     public static final int VOID_RESULT = -1, LAST_RESULT = -2;
 132 
 133     LambdaForm(String debugName,
 134                int arity, Name[] names, int result) {
 135         assert(namesOK(arity, names));
 136         this.arity = arity;
 137         this.result = fixResult(result, names);
 138         this.names = names.clone();
 139         this.debugName = debugName;
 140         normalize();
 141     }
 142 
 143     LambdaForm(String debugName,
 144                int arity, Name[] names) {
 145         this(debugName,
 146              arity, names, LAST_RESULT);
 147     }
 148 
 149     LambdaForm(String debugName,
 150                Name[] formals, Name[] temps, Name result) {
 151         this(debugName,
 152              formals.length, buildNames(formals, temps, result), LAST_RESULT);
 153     }
 154 
 155     private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {
 156         int arity = formals.length;
 157         int length = arity + temps.length + (result == null ? 0 : 1);
 158         Name[] names = Arrays.copyOf(formals, length);
 159         System.arraycopy(temps, 0, names, arity, temps.length);
 160         if (result != null)
 161             names[length - 1] = result;
 162         return names;
 163     }
 164 
 165     private LambdaForm(String sig) {
 166         // Make a blank lambda form, which returns a constant zero or null.
 167         // It is used as a template for managing the invocation of similar forms that are non-empty.
 168         // Called only from getPreparedForm.
 169         assert(isValidSignature(sig));
 170         this.arity = signatureArity(sig);
 171         this.result = (signatureReturn(sig) == 'V' ? -1 : arity);
 172         this.names = buildEmptyNames(arity, sig);
 173         this.debugName = "LF.zero";
 174         assert(nameRefsAreLegal());
 175         assert(isEmpty());
 176         assert(sig.equals(basicTypeSignature()));
 177     }
 178 
 179     private static Name[] buildEmptyNames(int arity, String basicTypeSignature) {
 180         assert(isValidSignature(basicTypeSignature));
 181         int resultPos = arity + 1;  // skip '_'
 182         if (arity < 0 || basicTypeSignature.length() != resultPos+1)
 183             throw new IllegalArgumentException("bad arity for "+basicTypeSignature);
 184         int numRes = (basicTypeSignature.charAt(resultPos) == 'V' ? 0 : 1);
 185         Name[] names = arguments(numRes, basicTypeSignature.substring(0, arity));
 186         for (int i = 0; i < numRes; i++) {
 187             names[arity + i] = constantZero(arity + i, basicTypeSignature.charAt(resultPos + i));
 188         }
 189         return names;
 190     }
 191 
 192     private static int fixResult(int result, Name[] names) {
 193         if (result >= 0) {
 194             if (names[result].type == 'V')
 195                 return -1;
 196         } else if (result == LAST_RESULT) {
 197             return names.length - 1;
 198         }
 199         return result;
 200     }
 201 
 202     private static boolean namesOK(int arity, Name[] names) {
 203         for (int i = 0; i < names.length; i++) {
 204             Name n = names[i];
 205             assert(n != null) : "n is null";
 206             if (i < arity)
 207                 assert( n.isParam()) : n + " is not param at " + i;
 208             else
 209                 assert(!n.isParam()) : n + " is param at " + i;
 210         }
 211         return true;
 212     }
 213 
 214     /** Renumber and/or replace params so that they are interned and canonically numbered. */
 215     private void normalize() {
 216         Name[] oldNames = null;
 217         int changesStart = 0;
 218         for (int i = 0; i < names.length; i++) {
 219             Name n = names[i];
 220             if (!n.initIndex(i)) {
 221                 if (oldNames == null) {
 222                     oldNames = names.clone();
 223                     changesStart = i;
 224                 }
 225                 names[i] = n.cloneWithIndex(i);
 226             }
 227         }
 228         if (oldNames != null) {
 229             int startFixing = arity;
 230             if (startFixing <= changesStart)
 231                 startFixing = changesStart+1;
 232             for (int i = startFixing; i < names.length; i++) {
 233                 Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);
 234                 names[i] = fixed.newIndex(i);
 235             }
 236         }
 237         assert(nameRefsAreLegal());
 238         int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);
 239         boolean needIntern = false;
 240         for (int i = 0; i < maxInterned; i++) {
 241             Name n = names[i], n2 = internArgument(n);
 242             if (n != n2) {
 243                 names[i] = n2;
 244                 needIntern = true;
 245             }
 246         }
 247         if (needIntern) {
 248             for (int i = arity; i < names.length; i++) {
 249                 names[i].internArguments();
 250             }
 251             assert(nameRefsAreLegal());
 252         }
 253     }
 254 
 255     /**
 256      * Check that all embedded Name references are localizable to this lambda,
 257      * and are properly ordered after their corresponding definitions.
 258      * <p>
 259      * Note that a Name can be local to multiple lambdas, as long as
 260      * it possesses the same index in each use site.
 261      * This allows Name references to be freely reused to construct
 262      * fresh lambdas, without confusion.
 263      */
 264     private boolean nameRefsAreLegal() {
 265         assert(arity >= 0 && arity <= names.length);
 266         assert(result >= -1 && result < names.length);
 267         // Do all names possess an index consistent with their local definition order?
 268         for (int i = 0; i < arity; i++) {
 269             Name n = names[i];
 270             assert(n.index() == i) : Arrays.asList(n.index(), i);
 271             assert(n.isParam());
 272         }
 273         // Also, do all local name references
 274         for (int i = arity; i < names.length; i++) {
 275             Name n = names[i];
 276             assert(n.index() == i);
 277             for (Object arg : n.arguments) {
 278                 if (arg instanceof Name) {
 279                     Name n2 = (Name) arg;
 280                     int i2 = n2.index;
 281                     assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;
 282                     assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);
 283                     assert(i2 < i);  // ref must come after def!
 284                 }
 285             }
 286         }
 287         return true;
 288     }
 289 
 290     /** Invoke this form on the given arguments. */
 291     // final Object invoke(Object... args) throws Throwable {
 292     //     // NYI: fit this into the fast path?
 293     //     return interpretWithArguments(args);
 294     // }
 295 
 296     /** Report the return type. */
 297     char returnType() {
 298         if (result < 0)  return 'V';
 299         Name n = names[result];
 300         return n.type;
 301     }
 302 
 303     /** Report the N-th argument type. */
 304     char parameterType(int n) {
 305         assert(n < arity);
 306         return names[n].type;
 307     }
 308 
 309     /** Report the arity. */
 310     int arity() {
 311         return arity;
 312     }
 313 
 314     /** Return the method type corresponding to my basic type signature. */
 315     MethodType methodType() {
 316         return signatureType(basicTypeSignature());
 317     }
 318     /** Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character. */
 319     final String basicTypeSignature() {
 320         StringBuilder buf = new StringBuilder(arity() + 3);
 321         for (int i = 0, a = arity(); i < a; i++)
 322             buf.append(parameterType(i));
 323         return buf.append('_').append(returnType()).toString();
 324     }
 325     static int signatureArity(String sig) {
 326         assert(isValidSignature(sig));
 327         return sig.indexOf('_');
 328     }
 329     static char signatureReturn(String sig) {
 330         return sig.charAt(signatureArity(sig)+1);
 331     }
 332     static boolean isValidSignature(String sig) {
 333         int arity = sig.indexOf('_');
 334         if (arity < 0)  return false;  // must be of the form *_*
 335         int siglen = sig.length();
 336         if (siglen != arity + 2)  return false;  // *_X
 337         for (int i = 0; i < siglen; i++) {
 338             if (i == arity)  continue;  // skip '_'
 339             char c = sig.charAt(i);
 340             if (c == 'V')
 341                 return (i == siglen - 1 && arity == siglen - 2);
 342             if (ALL_TYPES.indexOf(c) < 0)  return false; // must be [LIJFD]
 343         }
 344         return true;  // [LIJFD]*_[LIJFDV]
 345     }
 346     static Class<?> typeClass(char t) {
 347         switch (t) {
 348         case 'I': return int.class;
 349         case 'J': return long.class;
 350         case 'F': return float.class;
 351         case 'D': return double.class;
 352         case 'L': return Object.class;
 353         case 'V': return void.class;
 354         default: assert false;
 355         }
 356         return null;
 357     }
 358     static MethodType signatureType(String sig) {
 359         Class<?>[] ptypes = new Class<?>[signatureArity(sig)];
 360         for (int i = 0; i < ptypes.length; i++)
 361             ptypes[i] = typeClass(sig.charAt(i));
 362         Class<?> rtype = typeClass(signatureReturn(sig));
 363         return MethodType.methodType(rtype, ptypes);
 364     }
 365 
 366     /*
 367      * Code generation issues:
 368      *
 369      * Compiled LFs should be reusable in general.
 370      * The biggest issue is how to decide when to pull a name into
 371      * the bytecode, versus loading a reified form from the MH data.
 372      *
 373      * For example, an asType wrapper may require execution of a cast
 374      * after a call to a MH.  The target type of the cast can be placed
 375      * as a constant in the LF itself.  This will force the cast type
 376      * to be compiled into the bytecodes and native code for the MH.
 377      * Or, the target type of the cast can be erased in the LF, and
 378      * loaded from the MH data.  (Later on, if the MH as a whole is
 379      * inlined, the data will flow into the inlined instance of the LF,
 380      * as a constant, and the end result will be an optimal cast.)
 381      *
 382      * This erasure of cast types can be done with any use of
 383      * reference types.  It can also be done with whole method
 384      * handles.  Erasing a method handle might leave behind
 385      * LF code that executes correctly for any MH of a given
 386      * type, and load the required MH from the enclosing MH's data.
 387      * Or, the erasure might even erase the expected MT.
 388      *
 389      * Also, for direct MHs, the MemberName of the target
 390      * could be erased, and loaded from the containing direct MH.
 391      * As a simple case, a LF for all int-valued non-static
 392      * field getters would perform a cast on its input argument
 393      * (to non-constant base type derived from the MemberName)
 394      * and load an integer value from the input object
 395      * (at a non-constant offset also derived from the MemberName).
 396      * Such MN-erased LFs would be inlinable back to optimized
 397      * code, whenever a constant enclosing DMH is available
 398      * to supply a constant MN from its data.
 399      *
 400      * The main problem here is to keep LFs reasonably generic,
 401      * while ensuring that hot spots will inline good instances.
 402      * "Reasonably generic" means that we don't end up with
 403      * repeated versions of bytecode or machine code that do
 404      * not differ in their optimized form.  Repeated versions
 405      * of machine would have the undesirable overheads of
 406      * (a) redundant compilation work and (b) extra I$ pressure.
 407      * To control repeated versions, we need to be ready to
 408      * erase details from LFs and move them into MH data,
 409      * whevener those details are not relevant to significant
 410      * optimization.  "Significant" means optimization of
 411      * code that is actually hot.
 412      *
 413      * Achieving this may require dynamic splitting of MHs, by replacing
 414      * a generic LF with a more specialized one, on the same MH,
 415      * if (a) the MH is frequently executed and (b) the MH cannot
 416      * be inlined into a containing caller, such as an invokedynamic.
 417      *
 418      * Compiled LFs that are no longer used should be GC-able.
 419      * If they contain non-BCP references, they should be properly
 420      * interlinked with the class loader(s) that their embedded types
 421      * depend on.  This probably means that reusable compiled LFs
 422      * will be tabulated (indexed) on relevant class loaders,
 423      * or else that the tables that cache them will have weak links.
 424      */
 425 
 426     /**
 427      * Make this LF directly executable, as part of a MethodHandle.
 428      * Invariant:  Every MH which is invoked must prepare its LF
 429      * before invocation.
 430      * (In principle, the JVM could do this very lazily,
 431      * as a sort of pre-invocation linkage step.)
 432      */
 433     public void prepare() {
 434         if (COMPILE_THRESHOLD == 0) {
 435             compileToBytecode();
 436         }
 437         if (this.vmentry != null) {
 438             // already prepared (e.g., a primitive DMH invoker form)
 439             return;
 440         }
 441         LambdaForm prep = getPreparedForm(basicTypeSignature());
 442         this.vmentry = prep.vmentry;
 443         // TO DO: Maybe add invokeGeneric, invokeWithArguments
 444     }
 445 
 446     /** Generate optimizable bytecode for this form. */
 447     MemberName compileToBytecode() {
 448         MethodType invokerType = methodType();
 449         assert(vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));
 450         if (vmentry != null && isCompiled) {
 451             return vmentry;  // already compiled somehow
 452         }
 453         try {
 454             vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);
 455             if (TRACE_INTERPRETER)
 456                 traceInterpreter("compileToBytecode", this);
 457             isCompiled = true;
 458             return vmentry;
 459         } catch (Error | Exception ex) {
 460             throw newInternalError(this.toString(), ex);
 461         }
 462     }
 463 
 464     private static final ConcurrentHashMap<String,LambdaForm> PREPARED_FORMS;
 465     static {
 466         int   capacity   = 512;    // expect many distinct signatures over time
 467         float loadFactor = 0.75f;  // normal default
 468         int   writers    = 1;
 469         PREPARED_FORMS = new ConcurrentHashMap<>(capacity, loadFactor, writers);
 470     }
 471 
 472     private static Map<String,LambdaForm> computeInitialPreparedForms() {
 473         // Find all predefined invokers and associate them with canonical empty lambda forms.
 474         HashMap<String,LambdaForm> forms = new HashMap<>();
 475         for (MemberName m : MemberName.getFactory().getMethods(LambdaForm.class, false, null, null, null)) {
 476             if (!m.isStatic() || !m.isPackage())  continue;
 477             MethodType mt = m.getMethodType();
 478             if (mt.parameterCount() > 0 &&
 479                 mt.parameterType(0) == MethodHandle.class &&
 480                 m.getName().startsWith("interpret_")) {
 481                 String sig = basicTypeSignature(mt);
 482                 assert(m.getName().equals("interpret" + sig.substring(sig.indexOf('_'))));
 483                 LambdaForm form = new LambdaForm(sig);
 484                 form.vmentry = m;
 485                 mt.form().setCachedLambdaForm(MethodTypeForm.LF_COUNTER, form);
 486                 // FIXME: get rid of PREPARED_FORMS; use MethodTypeForm cache only
 487                 forms.put(sig, form);
 488             }
 489         }
 490         //System.out.println("computeInitialPreparedForms => "+forms);
 491         return forms;
 492     }
 493 
 494     // Set this false to disable use of the interpret_L methods defined in this file.
 495     private static final boolean USE_PREDEFINED_INTERPRET_METHODS = true;
 496 
 497     // The following are predefined exact invokers.  The system must build
 498     // a separate invoker for each distinct signature.
 499     static Object interpret_L(MethodHandle mh) throws Throwable {
 500         Object[] av = {mh};
 501         String sig = null;
 502         assert(argumentTypesMatch(sig = "L_L", av));
 503         Object res = mh.form.interpretWithArguments(av);
 504         assert(returnTypesMatch(sig, av, res));
 505         return res;
 506     }
 507     static Object interpret_L(MethodHandle mh, Object x1) throws Throwable {
 508         Object[] av = {mh, x1};
 509         String sig = null;
 510         assert(argumentTypesMatch(sig = "LL_L", av));
 511         Object res = mh.form.interpretWithArguments(av);
 512         assert(returnTypesMatch(sig, av, res));
 513         return res;
 514     }
 515     static Object interpret_L(MethodHandle mh, Object x1, Object x2) throws Throwable {
 516         Object[] av = {mh, x1, x2};
 517         String sig = null;
 518         assert(argumentTypesMatch(sig = "LLL_L", av));
 519         Object res = mh.form.interpretWithArguments(av);
 520         assert(returnTypesMatch(sig, av, res));
 521         return res;
 522     }
 523     private static LambdaForm getPreparedForm(String sig) {
 524         MethodType mtype = signatureType(sig);
 525         //LambdaForm prep = PREPARED_FORMS.get(sig);
 526         LambdaForm prep =  mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);
 527         if (prep != null)  return prep;
 528         assert(isValidSignature(sig));
 529         prep = new LambdaForm(sig);
 530         prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(sig);
 531         //LambdaForm prep2 = PREPARED_FORMS.putIfAbsent(sig.intern(), prep);
 532         return mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);
 533     }
 534 
 535     // The next few routines are called only from assert expressions
 536     // They verify that the built-in invokers process the correct raw data types.
 537     private static boolean argumentTypesMatch(String sig, Object[] av) {
 538         int arity = signatureArity(sig);
 539         assert(av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;
 540         assert(av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];
 541         MethodHandle mh = (MethodHandle) av[0];
 542         MethodType mt = mh.type();
 543         assert(mt.parameterCount() == arity-1);
 544         for (int i = 0; i < av.length; i++) {
 545             Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i-1));
 546             assert(valueMatches(sig.charAt(i), pt, av[i]));
 547         }
 548         return true;
 549     }
 550     private static boolean valueMatches(char tc, Class<?> type, Object x) {
 551         // The following line is needed because (...)void method handles can use non-void invokers
 552         if (type == void.class)  tc = 'V';   // can drop any kind of value
 553         assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);
 554         switch (tc) {
 555         case 'I': assert checkInt(type, x)   : "checkInt(" + type + "," + x +")";   break;
 556         case 'J': assert x instanceof Long   : "instanceof Long: " + x;             break;
 557         case 'F': assert x instanceof Float  : "instanceof Float: " + x;            break;
 558         case 'D': assert x instanceof Double : "instanceof Double: " + x;           break;
 559         case 'L': assert checkRef(type, x)   : "checkRef(" + type + "," + x + ")";  break;
 560         case 'V': break;  // allow anything here; will be dropped
 561         default:  assert(false);
 562         }
 563         return true;
 564     }
 565     private static boolean returnTypesMatch(String sig, Object[] av, Object res) {
 566         MethodHandle mh = (MethodHandle) av[0];
 567         return valueMatches(signatureReturn(sig), mh.type().returnType(), res);
 568     }
 569     private static boolean checkInt(Class<?> type, Object x) {
 570         assert(x instanceof Integer);
 571         if (type == int.class)  return true;
 572         Wrapper w = Wrapper.forBasicType(type);
 573         assert(w.isSubwordOrInt());
 574         Object x1 = Wrapper.INT.wrap(w.wrap(x));
 575         return x.equals(x1);
 576     }
 577     private static boolean checkRef(Class<?> type, Object x) {
 578         assert(!type.isPrimitive());
 579         if (x == null)  return true;
 580         if (type.isInterface())  return true;
 581         return type.isInstance(x);
 582     }
 583 
 584     /** If the invocation count hits the threshold we spin bytecodes and call that subsequently. */
 585     private static final int COMPILE_THRESHOLD;
 586     static {
 587         if (MethodHandleStatics.COMPILE_THRESHOLD != null)
 588             COMPILE_THRESHOLD = MethodHandleStatics.COMPILE_THRESHOLD;
 589         else
 590             COMPILE_THRESHOLD = 30;  // default value
 591     }
 592     private int invocationCounter = 0;
 593 
 594     @Hidden
 595     @DontInline
 596     /** Interpretively invoke this form on the given arguments. */
 597     Object interpretWithArguments(Object... argumentValues) throws Throwable {
 598         if (TRACE_INTERPRETER)
 599             return interpretWithArgumentsTracing(argumentValues);
 600         checkInvocationCounter();
 601         assert(arityCheck(argumentValues));
 602         Object[] values = Arrays.copyOf(argumentValues, names.length);
 603         for (int i = argumentValues.length; i < values.length; i++) {
 604             values[i] = interpretName(names[i], values);
 605         }
 606         return (result < 0) ? null : values[result];
 607     }
 608 
 609     @Hidden
 610     @DontInline
 611     /** Evaluate a single Name within this form, applying its function to its arguments. */
 612     Object interpretName(Name name, Object[] values) throws Throwable {
 613         if (TRACE_INTERPRETER)
 614             traceInterpreter("| interpretName", name.debugString(), (Object[]) null);
 615         Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);
 616         for (int i = 0; i < arguments.length; i++) {
 617             Object a = arguments[i];
 618             if (a instanceof Name) {
 619                 int i2 = ((Name)a).index();
 620                 assert(names[i2] == a);
 621                 a = values[i2];
 622                 arguments[i] = a;
 623             }
 624         }
 625         return name.function.invokeWithArguments(arguments);
 626     }
 627 
 628     private void checkInvocationCounter() {
 629         if (COMPILE_THRESHOLD != 0 &&
 630             invocationCounter < COMPILE_THRESHOLD) {
 631             invocationCounter++;  // benign race
 632             if (invocationCounter >= COMPILE_THRESHOLD) {
 633                 // Replace vmentry with a bytecode version of this LF.
 634                 compileToBytecode();
 635             }
 636         }
 637     }
 638     Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {
 639         traceInterpreter("[ interpretWithArguments", this, argumentValues);
 640         if (invocationCounter < COMPILE_THRESHOLD) {
 641             int ctr = invocationCounter++;  // benign race
 642             traceInterpreter("| invocationCounter", ctr);
 643             if (invocationCounter >= COMPILE_THRESHOLD) {
 644                 compileToBytecode();
 645             }
 646         }
 647         Object rval;
 648         try {
 649             assert(arityCheck(argumentValues));
 650             Object[] values = Arrays.copyOf(argumentValues, names.length);
 651             for (int i = argumentValues.length; i < values.length; i++) {
 652                 values[i] = interpretName(names[i], values);
 653             }
 654             rval = (result < 0) ? null : values[result];
 655         } catch (Throwable ex) {
 656             traceInterpreter("] throw =>", ex);
 657             throw ex;
 658         }
 659         traceInterpreter("] return =>", rval);
 660         return rval;
 661     }
 662 
 663     //** This transform is applied (statically) to every name.function. */
 664     /*
 665     private static MethodHandle eraseSubwordTypes(MethodHandle mh) {
 666         MethodType mt = mh.type();
 667         if (mt.hasPrimitives()) {
 668             mt = mt.changeReturnType(eraseSubwordType(mt.returnType()));
 669             for (int i = 0; i < mt.parameterCount(); i++) {
 670                 mt = mt.changeParameterType(i, eraseSubwordType(mt.parameterType(i)));
 671             }
 672             mh = MethodHandles.explicitCastArguments(mh, mt);
 673         }
 674         return mh;
 675     }
 676     private static Class<?> eraseSubwordType(Class<?> type) {
 677         if (!type.isPrimitive())  return type;
 678         if (type == int.class)  return type;
 679         Wrapper w = Wrapper.forPrimitiveType(type);
 680         if (w.isSubwordOrInt())  return int.class;
 681         return type;
 682     }
 683     */
 684 
 685     static void traceInterpreter(String event, Object obj, Object... args) {
 686         if (!TRACE_INTERPRETER)  return;
 687         System.out.println("LFI: "+event+" "+(obj != null ? obj : "")+(args != null && args.length != 0 ? Arrays.asList(args) : ""));
 688     }
 689     static void traceInterpreter(String event, Object obj) {
 690         traceInterpreter(event, obj, (Object[])null);
 691     }
 692     private boolean arityCheck(Object[] argumentValues) {
 693         assert(argumentValues.length == arity) : arity+"!="+Arrays.asList(argumentValues)+".length";
 694         // also check that the leading (receiver) argument is somehow bound to this LF:
 695         assert(argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];
 696         assert(((MethodHandle)argumentValues[0]).internalForm() == this);
 697         // note:  argument #0 could also be an interface wrapper, in the future
 698         return true;
 699     }
 700 
 701     private boolean isEmpty() {
 702         if (result < 0)
 703             return (names.length == arity);
 704         else if (result == arity && names.length == arity + 1)
 705             return names[arity].isConstantZero();
 706         else
 707             return false;
 708     }
 709 
 710     public String toString() {
 711         StringBuilder buf = new StringBuilder(debugName+"=Lambda(");
 712         for (int i = 0; i < names.length; i++) {
 713             if (i == arity)  buf.append(")=>{");
 714             Name n = names[i];
 715             if (i >= arity)  buf.append("\n    ");
 716             buf.append(n);
 717             if (i < arity) {
 718                 if (i+1 < arity)  buf.append(",");
 719                 continue;
 720             }
 721             buf.append("=").append(n.exprString());
 722             buf.append(";");
 723         }
 724         buf.append(result < 0 ? "void" : names[result]).append("}");
 725         if (TRACE_INTERPRETER) {
 726             // Extra verbosity:
 727             buf.append(":").append(basicTypeSignature());
 728             buf.append("/").append(vmentry);
 729         }
 730         return buf.toString();
 731     }
 732 
 733     /**
 734      * Apply immediate binding for a Name in this form indicated by its position relative to the form.
 735      * The first parameter to a LambdaForm, a0:L, always represents the form's method handle, so 0 is not
 736      * accepted as valid.
 737      */
 738     LambdaForm bindImmediate(int pos, char basicType, Object value) {
 739         // must be an argument, and the types must match
 740         assert pos > 0 && pos < arity && names[pos].type == basicType && Name.typesMatch(basicType, value);
 741 
 742         int arity2 = arity - 1;
 743         Name[] names2 = new Name[names.length - 1];
 744         for (int r = 0, w = 0; r < names.length; ++r, ++w) { // (r)ead from names, (w)rite to names2
 745             Name n = names[r];
 746             if (n.isParam()) {
 747                 if (n.index == pos) {
 748                     // do not copy over the argument that is to be replaced with a literal,
 749                     // but adjust the write index
 750                     --w;
 751                 } else {
 752                     names2[w] = new Name(w, n.type);
 753                 }
 754             } else {
 755                 Object[] arguments2 = new Object[n.arguments.length];
 756                 for (int i = 0; i < n.arguments.length; ++i) {
 757                     Object arg = n.arguments[i];
 758                     if (arg instanceof Name) {
 759                         int ni = ((Name) arg).index;
 760                         if (ni == pos) {
 761                             arguments2[i] = value;
 762                         } else if (ni < pos) {
 763                             // replacement position not yet passed
 764                             arguments2[i] = names2[ni];
 765                         } else {
 766                             // replacement position passed
 767                             arguments2[i] = names2[ni - 1];
 768                         }
 769                     } else {
 770                         arguments2[i] = arg;
 771                     }
 772                 }
 773                 names2[w] = new Name(n.function, arguments2);
 774                 names2[w].initIndex(w);
 775             }
 776         }
 777 
 778         int result2 = result == -1 ? -1 : result - 1;
 779         return new LambdaForm(debugName, arity2, names2, result2);
 780     }
 781 
 782     LambdaForm bind(int namePos, BoundMethodHandle.SpeciesData oldData) {
 783         Name name = names[namePos];
 784         BoundMethodHandle.SpeciesData newData = oldData.extendWithType(name.type);
 785         return bind(name, newData.getterName(names[0], oldData.fieldCount()), oldData, newData);
 786     }
 787     LambdaForm bind(Name name, Name binding,
 788                     BoundMethodHandle.SpeciesData oldData,
 789                     BoundMethodHandle.SpeciesData newData) {
 790         int pos = name.index;
 791         assert(name.isParam());
 792         assert(!binding.isParam());
 793         assert(name.type == binding.type);
 794         assert(0 <= pos && pos < arity && names[pos] == name);
 795         assert(binding.function.memberDeclaringClassOrNull() == newData.clazz);
 796         assert(oldData.getters.length == newData.getters.length-1);
 797         if (bindCache != null) {
 798             LambdaForm form = bindCache[pos];
 799             if (form != null) {
 800                 assert(form.contains(binding)) : "form << " + form + " >> does not contain binding << " + binding + " >>";
 801                 return form;
 802             }
 803         } else {
 804             bindCache = new LambdaForm[arity];
 805         }
 806         assert(nameRefsAreLegal());
 807         int arity2 = arity-1;
 808         Name[] names2 = names.clone();
 809         names2[pos] = binding;  // we might move this in a moment
 810 
 811         // The newly created LF will run with a different BMH.
 812         // Switch over any pre-existing BMH field references to the new BMH class.
 813         int firstOldRef = -1;
 814         for (int i = 0; i < names2.length; i++) {
 815             Name n = names[i];
 816             if (n.function != null &&
 817                 n.function.memberDeclaringClassOrNull() == oldData.clazz) {
 818                 MethodHandle oldGetter = n.function.resolvedHandle;
 819                 MethodHandle newGetter = null;
 820                 for (int j = 0; j < oldData.getters.length; j++) {
 821                     if (oldGetter == oldData.getters[j])
 822                         newGetter =  newData.getters[j];
 823                 }
 824                 if (newGetter != null) {
 825                     if (firstOldRef < 0)  firstOldRef = i;
 826                     Name n2 = new Name(newGetter, n.arguments);
 827                     names2[i] = n2;
 828                 }
 829             }
 830         }
 831 
 832         // Walk over the new list of names once, in forward order.
 833         // Replace references to 'name' with 'binding'.
 834         // Replace data structure references to the old BMH species with the new.
 835         // This might cause a ripple effect, but it will settle in one pass.
 836         assert(firstOldRef < 0 || firstOldRef > pos);
 837         for (int i = pos+1; i < names2.length; i++) {
 838             if (i <= arity2)  continue;
 839             names2[i] = names2[i].replaceNames(names, names2, pos, i);
 840         }
 841 
 842         //  (a0, a1, name=a2, a3, a4)  =>  (a0, a1, a3, a4, binding)
 843         int insPos = pos;
 844         for (; insPos+1 < names2.length; insPos++) {
 845             Name n = names2[insPos+1];
 846             if (n.isSiblingBindingBefore(binding)) {
 847                 names2[insPos] = n;
 848             } else {
 849                 break;
 850             }
 851         }
 852         names2[insPos] = binding;
 853 
 854         // Since we moved some stuff, maybe update the result reference:
 855         int result2 = result;
 856         if (result2 == pos)
 857             result2 = insPos;
 858         else if (result2 > pos && result2 <= insPos)
 859             result2 -= 1;
 860 
 861         return bindCache[pos] = new LambdaForm(debugName, arity2, names2, result2);
 862     }
 863 
 864     boolean contains(Name name) {
 865         int pos = name.index();
 866         if (pos >= 0) {
 867             return pos < names.length && name.equals(names[pos]);
 868         }
 869         for (int i = arity; i < names.length; i++) {
 870             if (name.equals(names[i]))
 871                 return true;
 872         }
 873         return false;
 874     }
 875 
 876     LambdaForm addArguments(int pos, char... types) {
 877         assert(pos <= arity);
 878         int length = names.length;
 879         int inTypes = types.length;
 880         Name[] names2 = Arrays.copyOf(names, length + inTypes);
 881         int arity2 = arity + inTypes;
 882         int result2 = result;
 883         if (result2 >= arity)
 884             result2 += inTypes;
 885         // names array has MH in slot 0; skip it.
 886         int argpos = pos + 1;
 887         // Note:  The LF constructor will rename names2[argpos...].
 888         // Make space for new arguments (shift temporaries).
 889         System.arraycopy(names, argpos, names2, argpos + inTypes, length - argpos);
 890         for (int i = 0; i < inTypes; i++) {
 891             names2[argpos + i] = new Name(types[i]);
 892         }
 893         return new LambdaForm(debugName, arity2, names2, result2);
 894     }
 895 
 896     LambdaForm addArguments(int pos, List<Class<?>> types) {
 897         char[] basicTypes = new char[types.size()];
 898         for (int i = 0; i < basicTypes.length; i++)
 899             basicTypes[i] = basicType(types.get(i));
 900         return addArguments(pos, basicTypes);
 901     }
 902 
 903     LambdaForm permuteArguments(int skip, int[] reorder, char[] types) {
 904         // Note:  When inArg = reorder[outArg], outArg is fed by a copy of inArg.
 905         // The types are the types of the new (incoming) arguments.
 906         int length = names.length;
 907         int inTypes = types.length;
 908         int outArgs = reorder.length;
 909         assert(skip+outArgs == arity);
 910         assert(permutedTypesMatch(reorder, types, names, skip));
 911         int pos = 0;
 912         // skip trivial first part of reordering:
 913         while (pos < outArgs && reorder[pos] == pos)  pos += 1;
 914         Name[] names2 = new Name[length - outArgs + inTypes];
 915         System.arraycopy(names, 0, names2, 0, skip+pos);
 916         // copy the body:
 917         int bodyLength = length - arity;
 918         System.arraycopy(names, skip+outArgs, names2, skip+inTypes, bodyLength);
 919         int arity2 = names2.length - bodyLength;
 920         int result2 = result;
 921         if (result2 >= 0) {
 922             if (result2 < skip+outArgs) {
 923                 // return the corresponding inArg
 924                 result2 = reorder[result2-skip];
 925             } else {
 926                 result2 = result2 - outArgs + inTypes;
 927             }
 928         }
 929         // rework names in the body:
 930         for (int j = pos; j < outArgs; j++) {
 931             Name n = names[skip+j];
 932             int i = reorder[j];
 933             // replace names[skip+j] by names2[skip+i]
 934             Name n2 = names2[skip+i];
 935             if (n2 == null)
 936                 names2[skip+i] = n2 = new Name(types[i]);
 937             else
 938                 assert(n2.type == types[i]);
 939             for (int k = arity2; k < names2.length; k++) {
 940                 names2[k] = names2[k].replaceName(n, n2);
 941             }
 942         }
 943         // some names are unused, but must be filled in
 944         for (int i = skip+pos; i < arity2; i++) {
 945             if (names2[i] == null)
 946                 names2[i] = argument(i, types[i - skip]);
 947         }
 948         for (int j = arity; j < names.length; j++) {
 949             int i = j - arity + arity2;
 950             // replace names2[i] by names[j]
 951             Name n = names[j];
 952             Name n2 = names2[i];
 953             if (n != n2) {
 954                 for (int k = i+1; k < names2.length; k++) {
 955                     names2[k] = names2[k].replaceName(n, n2);
 956                 }
 957             }
 958         }
 959         return new LambdaForm(debugName, arity2, names2, result2);
 960     }
 961 
 962     static boolean permutedTypesMatch(int[] reorder, char[] types, Name[] names, int skip) {
 963         int inTypes = types.length;
 964         int outArgs = reorder.length;
 965         for (int i = 0; i < outArgs; i++) {
 966             assert(names[skip+i].isParam());
 967             assert(names[skip+i].type == types[reorder[i]]);
 968         }
 969         return true;
 970     }
 971 
 972     static class NamedFunction {
 973         final MemberName member;
 974         MethodHandle resolvedHandle;
 975         MethodHandle invoker;
 976 
 977         NamedFunction(MethodHandle resolvedHandle) {
 978             this(resolvedHandle.internalMemberName(), resolvedHandle);
 979         }
 980         NamedFunction(MemberName member, MethodHandle resolvedHandle) {
 981             this.member = member;
 982             //resolvedHandle = eraseSubwordTypes(resolvedHandle);
 983             this.resolvedHandle = resolvedHandle;
 984         }
 985 
 986         // The next 3 constructors are used to break circular dependencies on MH.invokeStatic, etc.
 987         // Any LambdaForm containing such a member is not interpretable.
 988         // This is OK, since all such LFs are prepared with special primitive vmentry points.
 989         // And even without the resolvedHandle, the name can still be compiled and optimized.
 990         NamedFunction(Method method) {
 991             this(new MemberName(method));
 992         }
 993         NamedFunction(Field field) {
 994             this(new MemberName(field));
 995         }
 996         NamedFunction(MemberName member) {
 997             this.member = member;
 998             this.resolvedHandle = null;
 999         }
1000 
1001         MethodHandle resolvedHandle() {
1002             if (resolvedHandle == null)  resolve();
1003             return resolvedHandle;
1004         }
1005 
1006         void resolve() {
1007             resolvedHandle = DirectMethodHandle.make(member);
1008         }
1009 
1010         @Override
1011         public boolean equals(Object other) {
1012             if (this == other) return true;
1013             if (other == null) return false;
1014             if (!(other instanceof NamedFunction)) return false;
1015             NamedFunction that = (NamedFunction) other;
1016             return this.member != null && this.member.equals(that.member);
1017         }
1018 
1019         @Override
1020         public int hashCode() {
1021             if (member != null)
1022                 return member.hashCode();
1023             return super.hashCode();
1024         }
1025 
1026         // Put the predefined NamedFunction invokers into the table.
1027         static void initializeInvokers() {
1028             for (MemberName m : MemberName.getFactory().getMethods(NamedFunction.class, false, null, null, null)) {
1029                 if (!m.isStatic() || !m.isPackage())  continue;
1030                 MethodType type = m.getMethodType();
1031                 if (type.equals(INVOKER_METHOD_TYPE) &&
1032                     m.getName().startsWith("invoke_")) {
1033                     String sig = m.getName().substring("invoke_".length());
1034                     int arity = LambdaForm.signatureArity(sig);
1035                     MethodType srcType = MethodType.genericMethodType(arity);
1036                     if (LambdaForm.signatureReturn(sig) == 'V')
1037                         srcType = srcType.changeReturnType(void.class);
1038                     MethodTypeForm typeForm = srcType.form();
1039                     typeForm.namedFunctionInvoker = DirectMethodHandle.make(m);
1040                 }
1041             }
1042         }
1043 
1044         // The following are predefined NamedFunction invokers.  The system must build
1045         // a separate invoker for each distinct signature.
1046         /** void return type invokers. */
1047         @Hidden
1048         static Object invoke__V(MethodHandle mh, Object[] a) throws Throwable {
1049             assert(a.length == 0);
1050             mh.invokeBasic();
1051             return null;
1052         }
1053         @Hidden
1054         static Object invoke_L_V(MethodHandle mh, Object[] a) throws Throwable {
1055             assert(a.length == 1);
1056             mh.invokeBasic(a[0]);
1057             return null;
1058         }
1059         @Hidden
1060         static Object invoke_LL_V(MethodHandle mh, Object[] a) throws Throwable {
1061             assert(a.length == 2);
1062             mh.invokeBasic(a[0], a[1]);
1063             return null;
1064         }
1065         @Hidden
1066         static Object invoke_LLL_V(MethodHandle mh, Object[] a) throws Throwable {
1067             assert(a.length == 3);
1068             mh.invokeBasic(a[0], a[1], a[2]);
1069             return null;
1070         }
1071         @Hidden
1072         static Object invoke_LLLL_V(MethodHandle mh, Object[] a) throws Throwable {
1073             assert(a.length == 4);
1074             mh.invokeBasic(a[0], a[1], a[2], a[3]);
1075             return null;
1076         }
1077         @Hidden
1078         static Object invoke_LLLLL_V(MethodHandle mh, Object[] a) throws Throwable {
1079             assert(a.length == 5);
1080             mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
1081             return null;
1082         }
1083         /** Object return type invokers. */
1084         @Hidden
1085         static Object invoke__L(MethodHandle mh, Object[] a) throws Throwable {
1086             assert(a.length == 0);
1087             return mh.invokeBasic();
1088         }
1089         @Hidden
1090         static Object invoke_L_L(MethodHandle mh, Object[] a) throws Throwable {
1091             assert(a.length == 1);
1092             return mh.invokeBasic(a[0]);
1093         }
1094         @Hidden
1095         static Object invoke_LL_L(MethodHandle mh, Object[] a) throws Throwable {
1096             assert(a.length == 2);
1097             return mh.invokeBasic(a[0], a[1]);
1098         }
1099         @Hidden
1100         static Object invoke_LLL_L(MethodHandle mh, Object[] a) throws Throwable {
1101             assert(a.length == 3);
1102             return mh.invokeBasic(a[0], a[1], a[2]);
1103         }
1104         @Hidden
1105         static Object invoke_LLLL_L(MethodHandle mh, Object[] a) throws Throwable {
1106             assert(a.length == 4);
1107             return mh.invokeBasic(a[0], a[1], a[2], a[3]);
1108         }
1109         @Hidden
1110         static Object invoke_LLLLL_L(MethodHandle mh, Object[] a) throws Throwable {
1111             assert(a.length == 5);
1112             return mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
1113         }
1114 
1115         static final MethodType INVOKER_METHOD_TYPE =
1116             MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1117 
1118         private static MethodHandle computeInvoker(MethodTypeForm typeForm) {
1119             MethodHandle mh = typeForm.namedFunctionInvoker;
1120             if (mh != null)  return mh;
1121             MemberName invoker = InvokerBytecodeGenerator.generateNamedFunctionInvoker(typeForm);  // this could take a while
1122             mh = DirectMethodHandle.make(invoker);
1123             MethodHandle mh2 = typeForm.namedFunctionInvoker;
1124             if (mh2 != null)  return mh2;  // benign race
1125             if (!mh.type().equals(INVOKER_METHOD_TYPE))
1126                 throw new InternalError(mh.debugString());
1127             return typeForm.namedFunctionInvoker = mh;
1128         }
1129 
1130         @Hidden
1131         Object invokeWithArguments(Object... arguments) throws Throwable {
1132             // If we have a cached invoker, call it right away.
1133             // NOTE: The invoker always returns a reference value.
1134             if (TRACE_INTERPRETER)  return invokeWithArgumentsTracing(arguments);
1135             assert(checkArgumentTypes(arguments, methodType()));
1136             return invoker().invokeBasic(resolvedHandle(), arguments);
1137         }
1138 
1139         @Hidden
1140         Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {
1141             Object rval;
1142             try {
1143                 traceInterpreter("[ call", this, arguments);
1144                 if (invoker == null) {
1145                     traceInterpreter("| getInvoker", this);
1146                     invoker();
1147                 }
1148                 if (resolvedHandle == null) {
1149                     traceInterpreter("| resolve", this);
1150                     resolvedHandle();
1151                 }
1152                 assert(checkArgumentTypes(arguments, methodType()));
1153                 rval = invoker().invokeBasic(resolvedHandle(), arguments);
1154             } catch (Throwable ex) {
1155                 traceInterpreter("] throw =>", ex);
1156                 throw ex;
1157             }
1158             traceInterpreter("] return =>", rval);
1159             return rval;
1160         }
1161 
1162         private MethodHandle invoker() {
1163             if (invoker != null)  return invoker;
1164             // Get an invoker and cache it.
1165             return invoker = computeInvoker(methodType().form());
1166         }
1167 
1168         private static boolean checkArgumentTypes(Object[] arguments, MethodType methodType) {
1169             if (true)  return true;  // FIXME
1170             MethodType dstType = methodType.form().erasedType();
1171             MethodType srcType = dstType.basicType().wrap();
1172             Class<?>[] ptypes = new Class<?>[arguments.length];
1173             for (int i = 0; i < arguments.length; i++) {
1174                 Object arg = arguments[i];
1175                 Class<?> ptype = arg == null ? Object.class : arg.getClass();
1176                 // If the dest. type is a primitive we keep the
1177                 // argument type.
1178                 ptypes[i] = dstType.parameterType(i).isPrimitive() ? ptype : Object.class;
1179             }
1180             MethodType argType = MethodType.methodType(srcType.returnType(), ptypes).wrap();
1181             assert(argType.isConvertibleTo(srcType)) : "wrong argument types: cannot convert " + argType + " to " + srcType;
1182             return true;
1183         }
1184 
1185         String basicTypeSignature() {
1186             //return LambdaForm.basicTypeSignature(resolvedHandle.type());
1187             return LambdaForm.basicTypeSignature(methodType());
1188         }
1189 
1190         MethodType methodType() {
1191             if (resolvedHandle != null)
1192                 return resolvedHandle.type();
1193             else
1194                 // only for certain internal LFs during bootstrapping
1195                 return member.getInvocationType();
1196         }
1197 
1198         MemberName member() {
1199             assert(assertMemberIsConsistent());
1200             return member;
1201         }
1202 
1203         // Called only from assert.
1204         private boolean assertMemberIsConsistent() {
1205             if (resolvedHandle instanceof DirectMethodHandle) {
1206                 MemberName m = resolvedHandle.internalMemberName();
1207                 assert(m.equals(member));
1208             }
1209             return true;
1210         }
1211 
1212         Class<?> memberDeclaringClassOrNull() {
1213             return (member == null) ? null : member.getDeclaringClass();
1214         }
1215 
1216         char returnType() {
1217             return basicType(methodType().returnType());
1218         }
1219 
1220         char parameterType(int n) {
1221             return basicType(methodType().parameterType(n));
1222         }
1223 
1224         int arity() {
1225             //int siglen = member.getMethodType().parameterCount();
1226             //if (!member.isStatic())  siglen += 1;
1227             //return siglen;
1228             return methodType().parameterCount();
1229         }
1230 
1231         public String toString() {
1232             if (member == null)  return resolvedHandle.toString();
1233             return member.getDeclaringClass().getSimpleName()+"."+member.getName();
1234         }
1235     }
1236 
1237     void resolve() {
1238         for (Name n : names) n.resolve();
1239     }
1240 
1241     public static char basicType(Class<?> type) {
1242         char c = Wrapper.basicTypeChar(type);
1243         if ("ZBSC".indexOf(c) >= 0)  c = 'I';
1244         assert("LIJFDV".indexOf(c) >= 0);
1245         return c;
1246     }
1247     public static char[] basicTypes(List<Class<?>> types) {
1248         char[] btypes = new char[types.size()];
1249         for (int i = 0; i < btypes.length; i++) {
1250             btypes[i] = basicType(types.get(i));
1251         }
1252         return btypes;
1253     }
1254     public static String basicTypeSignature(MethodType type) {
1255         char[] sig = new char[type.parameterCount() + 2];
1256         int sigp = 0;
1257         for (Class<?> pt : type.parameterList()) {
1258             sig[sigp++] = basicType(pt);
1259         }
1260         sig[sigp++] = '_';
1261         sig[sigp++] = basicType(type.returnType());
1262         assert(sigp == sig.length);
1263         return String.valueOf(sig);
1264     }
1265 
1266     static final class Name {
1267         final char type;
1268         private short index;
1269         final NamedFunction function;
1270         final Object[] arguments;
1271 
1272         private Name(int index, char type, NamedFunction function, Object[] arguments) {
1273             this.index = (short)index;
1274             this.type = type;
1275             this.function = function;
1276             this.arguments = arguments;
1277             assert(this.index == index);
1278         }
1279         Name(MethodHandle function, Object... arguments) {
1280             this(new NamedFunction(function), arguments);
1281         }
1282         Name(MemberName function, Object... arguments) {
1283             this(new NamedFunction(function), arguments);
1284         }
1285         Name(NamedFunction function, Object... arguments) {
1286             this(-1, function.returnType(), function, arguments = arguments.clone());
1287             assert(arguments.length == function.arity()) : "arity mismatch: arguments.length=" + arguments.length + " == function.arity()=" + function.arity() + " in " + debugString();
1288             for (int i = 0; i < arguments.length; i++)
1289                 assert(typesMatch(function.parameterType(i), arguments[i])) : "types don't match: function.parameterType(" + i + ")=" + function.parameterType(i) + ", arguments[" + i + "]=" + arguments[i] + " in " + debugString();
1290         }
1291         Name(int index, char type) {
1292             this(index, type, null, null);
1293         }
1294         Name(char type) {
1295             this(-1, type);
1296         }
1297 
1298         char type() { return type; }
1299         int index() { return index; }
1300         boolean initIndex(int i) {
1301             if (index != i) {
1302                 if (index != -1)  return false;
1303                 index = (short)i;
1304             }
1305             return true;
1306         }
1307 
1308 
1309         void resolve() {
1310             if (function != null)
1311                 function.resolve();
1312         }
1313 
1314         Name newIndex(int i) {
1315             if (initIndex(i))  return this;
1316             return cloneWithIndex(i);
1317         }
1318         Name cloneWithIndex(int i) {
1319             Object[] newArguments = (arguments == null) ? null : arguments.clone();
1320             return new Name(i, type, function, newArguments);
1321         }
1322         Name replaceName(Name oldName, Name newName) {  // FIXME: use replaceNames uniformly
1323             if (oldName == newName)  return this;
1324             @SuppressWarnings("LocalVariableHidesMemberVariable")
1325             Object[] arguments = this.arguments;
1326             if (arguments == null)  return this;
1327             boolean replaced = false;
1328             for (int j = 0; j < arguments.length; j++) {
1329                 if (arguments[j] == oldName) {
1330                     if (!replaced) {
1331                         replaced = true;
1332                         arguments = arguments.clone();
1333                     }
1334                     arguments[j] = newName;
1335                 }
1336             }
1337             if (!replaced)  return this;
1338             return new Name(function, arguments);
1339         }
1340         Name replaceNames(Name[] oldNames, Name[] newNames, int start, int end) {
1341             @SuppressWarnings("LocalVariableHidesMemberVariable")
1342             Object[] arguments = this.arguments;
1343             boolean replaced = false;
1344         eachArg:
1345             for (int j = 0; j < arguments.length; j++) {
1346                 if (arguments[j] instanceof Name) {
1347                     Name n = (Name) arguments[j];
1348                     int check = n.index;
1349                     // harmless check to see if the thing is already in newNames:
1350                     if (check >= 0 && check < newNames.length && n == newNames[check])
1351                         continue eachArg;
1352                     // n might not have the correct index: n != oldNames[n.index].
1353                     for (int i = start; i < end; i++) {
1354                         if (n == oldNames[i]) {
1355                             if (n == newNames[i])
1356                                 continue eachArg;
1357                             if (!replaced) {
1358                                 replaced = true;
1359                                 arguments = arguments.clone();
1360                             }
1361                             arguments[j] = newNames[i];
1362                             continue eachArg;
1363                         }
1364                     }
1365                 }
1366             }
1367             if (!replaced)  return this;
1368             return new Name(function, arguments);
1369         }
1370         void internArguments() {
1371             @SuppressWarnings("LocalVariableHidesMemberVariable")
1372             Object[] arguments = this.arguments;
1373             for (int j = 0; j < arguments.length; j++) {
1374                 if (arguments[j] instanceof Name) {
1375                     Name n = (Name) arguments[j];
1376                     if (n.isParam() && n.index < INTERNED_ARGUMENT_LIMIT)
1377                         arguments[j] = internArgument(n);
1378                 }
1379             }
1380         }
1381         boolean isParam() {
1382             return function == null;
1383         }
1384         boolean isConstantZero() {
1385             return !isParam() && arguments.length == 0 && function.equals(constantZero(0, type).function);
1386         }
1387 
1388         public String toString() {
1389             return (isParam()?"a":"t")+(index >= 0 ? index : System.identityHashCode(this))+":"+type;
1390         }
1391         public String debugString() {
1392             String s = toString();
1393             return (function == null) ? s : s + "=" + exprString();
1394         }
1395         public String exprString() {
1396             if (function == null)  return "null";
1397             StringBuilder buf = new StringBuilder(function.toString());
1398             buf.append("(");
1399             String cma = "";
1400             for (Object a : arguments) {
1401                 buf.append(cma); cma = ",";
1402                 if (a instanceof Name || a instanceof Integer)
1403                     buf.append(a);
1404                 else
1405                     buf.append("(").append(a).append(")");
1406             }
1407             buf.append(")");
1408             return buf.toString();
1409         }
1410 
1411         private static boolean typesMatch(char parameterType, Object object) {
1412             if (object instanceof Name) {
1413                 return ((Name)object).type == parameterType;
1414             }
1415             switch (parameterType) {
1416                 case 'I':  return object instanceof Integer;
1417                 case 'J':  return object instanceof Long;
1418                 case 'F':  return object instanceof Float;
1419                 case 'D':  return object instanceof Double;
1420             }
1421             assert(parameterType == 'L');
1422             return true;
1423         }
1424 
1425         /**
1426          * Does this Name precede the given binding node in some canonical order?
1427          * This predicate is used to order data bindings (via insertion sort)
1428          * with some stability.
1429          * @param binding
1430          * @return
1431          */
1432         boolean isSiblingBindingBefore(Name binding) {
1433             assert(!binding.isParam());
1434             if (isParam())  return true;
1435             if (function.equals(binding.function) &&
1436                 arguments.length == binding.arguments.length) {
1437                 boolean sawInt = false;
1438                 for (int i = 0; i < arguments.length; i++) {
1439                     Object a1 = arguments[i];
1440                     Object a2 = binding.arguments[i];
1441                     if (!a1.equals(a2)) {
1442                         if (a1 instanceof Integer && a2 instanceof Integer) {
1443                             if (sawInt)  continue;
1444                             sawInt = true;
1445                             if ((int)a1 < (int)a2)  continue;  // still might be true
1446                         }
1447                         return false;
1448                     }
1449                 }
1450                 return sawInt;
1451             }
1452             return false;
1453         }
1454 
1455         public boolean equals(Name that) {
1456             if (this == that)  return true;
1457             if (isParam())
1458                 // each parameter is a unique atom
1459                 return false;  // this != that
1460             return
1461                 //this.index == that.index &&
1462                 this.type == that.type &&
1463                 this.function.equals(that.function) &&
1464                 Arrays.equals(this.arguments, that.arguments);
1465         }
1466         @Override
1467         public boolean equals(Object x) {
1468             return x instanceof Name && equals((Name)x);
1469         }
1470         @Override
1471         public int hashCode() {
1472             if (isParam())
1473                 return index | (type << 8);
1474             return function.hashCode() ^ Arrays.hashCode(arguments);
1475         }
1476     }
1477 
1478     static Name argument(int which, char type) {
1479         int tn = ALL_TYPES.indexOf(type);
1480         if (tn < 0 || which >= INTERNED_ARGUMENT_LIMIT)
1481             return new Name(which, type);
1482         return INTERNED_ARGUMENTS[tn][which];
1483     }
1484     static Name internArgument(Name n) {
1485         assert(n.isParam()) : "not param: " + n;
1486         assert(n.index < INTERNED_ARGUMENT_LIMIT);
1487         return argument(n.index, n.type);
1488     }
1489     static Name[] arguments(int extra, String types) {
1490         int length = types.length();
1491         Name[] names = new Name[length + extra];
1492         for (int i = 0; i < length; i++)
1493             names[i] = argument(i, types.charAt(i));
1494         return names;
1495     }
1496     static Name[] arguments(int extra, char... types) {
1497         int length = types.length;
1498         Name[] names = new Name[length + extra];
1499         for (int i = 0; i < length; i++)
1500             names[i] = argument(i, types[i]);
1501         return names;
1502     }
1503     static Name[] arguments(int extra, List<Class<?>> types) {
1504         int length = types.size();
1505         Name[] names = new Name[length + extra];
1506         for (int i = 0; i < length; i++)
1507             names[i] = argument(i, basicType(types.get(i)));
1508         return names;
1509     }
1510     static Name[] arguments(int extra, Class<?>... types) {
1511         int length = types.length;
1512         Name[] names = new Name[length + extra];
1513         for (int i = 0; i < length; i++)
1514             names[i] = argument(i, basicType(types[i]));
1515         return names;
1516     }
1517     static Name[] arguments(int extra, MethodType types) {
1518         int length = types.parameterCount();
1519         Name[] names = new Name[length + extra];
1520         for (int i = 0; i < length; i++)
1521             names[i] = argument(i, basicType(types.parameterType(i)));
1522         return names;
1523     }
1524     static final String ALL_TYPES = "LIJFD";  // omit V, not an argument type
1525     static final int INTERNED_ARGUMENT_LIMIT = 10;
1526     private static final Name[][] INTERNED_ARGUMENTS
1527             = new Name[ALL_TYPES.length()][INTERNED_ARGUMENT_LIMIT];
1528     static {
1529         for (int tn = 0; tn < ALL_TYPES.length(); tn++) {
1530             for (int i = 0; i < INTERNED_ARGUMENTS[tn].length; i++) {
1531                 char type = ALL_TYPES.charAt(tn);
1532                 INTERNED_ARGUMENTS[tn][i] = new Name(i, type);
1533             }
1534         }
1535     }
1536 
1537     private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
1538 
1539     static Name constantZero(int which, char type) {
1540         return CONSTANT_ZERO[ALL_TYPES.indexOf(type)].newIndex(which);
1541     }
1542     private static final Name[] CONSTANT_ZERO
1543             = new Name[ALL_TYPES.length()];
1544     static {
1545         for (int tn = 0; tn < ALL_TYPES.length(); tn++) {
1546             char bt = ALL_TYPES.charAt(tn);
1547             Wrapper wrap = Wrapper.forBasicType(bt);
1548             MemberName zmem = new MemberName(LambdaForm.class, "zero"+bt, MethodType.methodType(wrap.primitiveType()), REF_invokeStatic);
1549             try {
1550                 zmem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, zmem, null, NoSuchMethodException.class);
1551             } catch (IllegalAccessException|NoSuchMethodException ex) {
1552                 throw newInternalError(ex);
1553             }
1554             NamedFunction zcon = new NamedFunction(zmem);
1555             Name n = new Name(zcon).newIndex(0);
1556             assert(n.type == ALL_TYPES.charAt(tn));
1557             CONSTANT_ZERO[tn] = n;
1558             assert(n.isConstantZero());
1559         }
1560     }
1561 
1562     // Avoid appealing to ValueConversions at bootstrap time:
1563     private static int zeroI() { return 0; }
1564     private static long zeroJ() { return 0; }
1565     private static float zeroF() { return 0; }
1566     private static double zeroD() { return 0; }
1567     private static Object zeroL() { return null; }
1568 
1569     // Put this last, so that previous static inits can run before.
1570     static {
1571         if (USE_PREDEFINED_INTERPRET_METHODS)
1572             PREPARED_FORMS.putAll(computeInitialPreparedForms());
1573     }
1574 
1575     /**
1576      * Internal marker for byte-compiled LambdaForms.
1577      */
1578     /*non-public*/
1579     @Target(ElementType.METHOD)
1580     @Retention(RetentionPolicy.RUNTIME)
1581     @interface Compiled {
1582     }
1583 
1584     /**
1585      * Internal marker for LambdaForm interpreter frames.
1586      */
1587     /*non-public*/
1588     @Target(ElementType.METHOD)
1589     @Retention(RetentionPolicy.RUNTIME)
1590     @interface Hidden {
1591     }
1592 
1593 
1594 /*
1595     // Smoke-test for the invokers used in this file.
1596     static void testMethodHandleLinkers() throws Throwable {
1597         MemberName.Factory lookup = MemberName.getFactory();
1598         MemberName asList_MN = new MemberName(Arrays.class, "asList",
1599                                               MethodType.methodType(List.class, Object[].class),
1600                                               REF_invokeStatic);
1601         //MethodHandleNatives.resolve(asList_MN, null);
1602         asList_MN = lookup.resolveOrFail(asList_MN, REF_invokeStatic, null, NoSuchMethodException.class);
1603         System.out.println("about to call "+asList_MN);
1604         Object[] abc = { "a", "bc" };
1605         List<?> lst = (List<?>) MethodHandle.linkToStatic(abc, asList_MN);
1606         System.out.println("lst="+lst);
1607         MemberName toString_MN = new MemberName(Object.class.getMethod("toString"));
1608         String s1 = (String) MethodHandle.linkToVirtual(lst, toString_MN);
1609         toString_MN = new MemberName(Object.class.getMethod("toString"), true);
1610         String s2 = (String) MethodHandle.linkToSpecial(lst, toString_MN);
1611         System.out.println("[s1,s2,lst]="+Arrays.asList(s1, s2, lst.toString()));
1612         MemberName toArray_MN = new MemberName(List.class.getMethod("toArray"));
1613         Object[] arr = (Object[]) MethodHandle.linkToInterface(lst, toArray_MN);
1614         System.out.println("toArray="+Arrays.toString(arr));
1615     }
1616     static { try { testMethodHandleLinkers(); } catch (Throwable ex) { throw new RuntimeException(ex); } }
1617     // Requires these definitions in MethodHandle:
1618     static final native Object linkToStatic(Object x1, MemberName mn) throws Throwable;
1619     static final native Object linkToVirtual(Object x1, MemberName mn) throws Throwable;
1620     static final native Object linkToSpecial(Object x1, MemberName mn) throws Throwable;
1621     static final native Object linkToInterface(Object x1, MemberName mn) throws Throwable;
1622  */
1623 
1624     static { NamedFunction.initializeInvokers(); }
1625 }