1 /*
   2  * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package java.lang.invoke;
  27 
  28 import java.lang.annotation.*;
  29 import java.lang.reflect.Method;
  30 import java.util.List;
  31 import java.util.Arrays;
  32 import java.util.HashMap;
  33 
  34 import sun.invoke.util.Wrapper;
  35 import java.lang.reflect.Field;
  36 
  37 import static java.lang.invoke.LambdaForm.BasicType.*;
  38 import static java.lang.invoke.MethodHandleStatics.*;
  39 import static java.lang.invoke.MethodHandleNatives.Constants.*;
  40 
  41 /**
  42  * The symbolic, non-executable form of a method handle's invocation semantics.
  43  * It consists of a series of names.
  44  * The first N (N=arity) names are parameters,
  45  * while any remaining names are temporary values.
  46  * Each temporary specifies the application of a function to some arguments.
  47  * The functions are method handles, while the arguments are mixes of
  48  * constant values and local names.
  49  * The result of the lambda is defined as one of the names, often the last one.
  50  * <p>
  51  * Here is an approximate grammar:
  52  * <blockquote><pre>{@code
  53  * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"
  54  * ArgName = "a" N ":" T
  55  * TempName = "t" N ":" T "=" Function "(" Argument* ");"
  56  * Function = ConstantValue
  57  * Argument = NameRef | ConstantValue
  58  * Result = NameRef | "void"
  59  * NameRef = "a" N | "t" N
  60  * N = (any whole number)
  61  * T = "L" | "I" | "J" | "F" | "D" | "V"
  62  * }</pre></blockquote>
  63  * Names are numbered consecutively from left to right starting at zero.
  64  * (The letters are merely a taste of syntax sugar.)
  65  * Thus, the first temporary (if any) is always numbered N (where N=arity).
  66  * Every occurrence of a name reference in an argument list must refer to
  67  * a name previously defined within the same lambda.
  68  * A lambda has a void result if and only if its result index is -1.
  69  * If a temporary has the type "V", it cannot be the subject of a NameRef,
  70  * even though possesses a number.
  71  * Note that all reference types are erased to "L", which stands for {@code Object}.
  72  * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.
  73  * The other types stand for the usual primitive types.
  74  * <p>
  75  * Function invocation closely follows the static rules of the Java verifier.
  76  * Arguments and return values must exactly match when their "Name" types are
  77  * considered.
  78  * Conversions are allowed only if they do not change the erased type.
  79  * <ul>
  80  * <li>L = Object: casts are used freely to convert into and out of reference types
  81  * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})
  82  * <li>J = long: no implicit conversions
  83  * <li>F = float: no implicit conversions
  84  * <li>D = double: no implicit conversions
  85  * <li>V = void: a function result may be void if and only if its Name is of type "V"
  86  * </ul>
  87  * Although implicit conversions are not allowed, explicit ones can easily be
  88  * encoded by using temporary expressions which call type-transformed identity functions.
  89  * <p>
  90  * Examples:
  91  * <blockquote><pre>{@code
  92  * (a0:J)=>{ a0 }
  93  *     == identity(long)
  94  * (a0:I)=>{ t1:V = System.out#println(a0); void }
  95  *     == System.out#println(int)
  96  * (a0:L)=>{ t1:V = System.out#println(a0); a0 }
  97  *     == identity, with printing side-effect
  98  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
  99  *                 t3:L = BoundMethodHandle#target(a0);
 100  *                 t4:L = MethodHandle#invoke(t3, t2, a1); t4 }
 101  *     == general invoker for unary insertArgument combination
 102  * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);
 103  *                 t3:L = MethodHandle#invoke(t2, a1);
 104  *                 t4:L = FilterMethodHandle#target(a0);
 105  *                 t5:L = MethodHandle#invoke(t4, t3); t5 }
 106  *     == general invoker for unary filterArgument combination
 107  * (a0:L, a1:L)=>{ ...(same as previous example)...
 108  *                 t5:L = MethodHandle#invoke(t4, t3, a1); t5 }
 109  *     == general invoker for unary/unary foldArgument combination
 110  * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }
 111  *     == invoker for identity method handle which performs i2l
 112  * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
 113  *                 t3:L = Class#cast(t2,a1); t3 }
 114  *     == invoker for identity method handle which performs cast
 115  * }</pre></blockquote>
 116  * <p>
 117  * @author John Rose, JSR 292 EG
 118  */
 119 class LambdaForm {
 120     final int arity;
 121     final int result;
 122     final boolean forceInline;
 123     @Stable 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     volatile Object transformCache;  // managed by LambdaFormEditor
 129 
 130     public static final int VOID_RESULT = -1, LAST_RESULT = -2;
 131 
 132     enum BasicType {
 133         L_TYPE('L', Object.class, Wrapper.OBJECT),  // all reference types
 134         I_TYPE('I', int.class,    Wrapper.INT),
 135         J_TYPE('J', long.class,   Wrapper.LONG),
 136         F_TYPE('F', float.class,  Wrapper.FLOAT),
 137         D_TYPE('D', double.class, Wrapper.DOUBLE),  // all primitive types
 138         V_TYPE('V', void.class,   Wrapper.VOID);    // not valid in all contexts
 139 
 140         static final BasicType[] ALL_TYPES = BasicType.values();
 141         static final BasicType[] ARG_TYPES = Arrays.copyOf(ALL_TYPES, ALL_TYPES.length-1);
 142 
 143         static final int ARG_TYPE_LIMIT = ARG_TYPES.length;
 144         static final int TYPE_LIMIT = ALL_TYPES.length;
 145 
 146         private final char btChar;
 147         private final Class<?> btClass;
 148         private final Wrapper btWrapper;
 149 
 150         private BasicType(char btChar, Class<?> btClass, Wrapper wrapper) {
 151             this.btChar = btChar;
 152             this.btClass = btClass;
 153             this.btWrapper = wrapper;
 154         }
 155 
 156         char basicTypeChar() {
 157             return btChar;
 158         }
 159         Class<?> basicTypeClass() {
 160             return btClass;
 161         }
 162         Wrapper basicTypeWrapper() {
 163             return btWrapper;
 164         }
 165         int basicTypeSlots() {
 166             return btWrapper.stackSlots();
 167         }
 168 
 169         static BasicType basicType(byte type) {
 170             return ALL_TYPES[type];
 171         }
 172         static BasicType basicType(char type) {
 173             switch (type) {
 174                 case 'L': return L_TYPE;
 175                 case 'I': return I_TYPE;
 176                 case 'J': return J_TYPE;
 177                 case 'F': return F_TYPE;
 178                 case 'D': return D_TYPE;
 179                 case 'V': return V_TYPE;
 180                 // all subword types are represented as ints
 181                 case 'Z':
 182                 case 'B':
 183                 case 'S':
 184                 case 'C':
 185                     return I_TYPE;
 186                 default:
 187                     throw newInternalError("Unknown type char: '"+type+"'");
 188             }
 189         }
 190         static BasicType basicType(Wrapper type) {
 191             char c = type.basicTypeChar();
 192             return basicType(c);
 193         }
 194         static BasicType basicType(Class<?> type) {
 195             if (!type.isPrimitive())  return L_TYPE;
 196             return basicType(Wrapper.forPrimitiveType(type));
 197         }
 198 
 199         static char basicTypeChar(Class<?> type) {
 200             return basicType(type).btChar;
 201         }
 202         static BasicType[] basicTypes(List<Class<?>> types) {
 203             BasicType[] btypes = new BasicType[types.size()];
 204             for (int i = 0; i < btypes.length; i++) {
 205                 btypes[i] = basicType(types.get(i));
 206             }
 207             return btypes;
 208         }
 209         static BasicType[] basicTypes(String types) {
 210             BasicType[] btypes = new BasicType[types.length()];
 211             for (int i = 0; i < btypes.length; i++) {
 212                 btypes[i] = basicType(types.charAt(i));
 213             }
 214             return btypes;
 215         }
 216         static byte[] basicTypesOrd(BasicType[] btypes) {
 217             byte[] ords = new byte[btypes.length];
 218             for (int i = 0; i < btypes.length; i++) {
 219                 ords[i] = (byte)btypes[i].ordinal();
 220             }
 221             return ords;
 222         }
 223         static boolean isBasicTypeChar(char c) {
 224             return "LIJFDV".indexOf(c) >= 0;
 225         }
 226         static boolean isArgBasicTypeChar(char c) {
 227             return "LIJFD".indexOf(c) >= 0;
 228         }
 229 
 230         static { assert(checkBasicType()); }
 231         private static boolean checkBasicType() {
 232             for (int i = 0; i < ARG_TYPE_LIMIT; i++) {
 233                 assert ARG_TYPES[i].ordinal() == i;
 234                 assert ARG_TYPES[i] == ALL_TYPES[i];
 235             }
 236             for (int i = 0; i < TYPE_LIMIT; i++) {
 237                 assert ALL_TYPES[i].ordinal() == i;
 238             }
 239             assert ALL_TYPES[TYPE_LIMIT - 1] == V_TYPE;
 240             assert !Arrays.asList(ARG_TYPES).contains(V_TYPE);
 241             return true;
 242         }
 243     }
 244 
 245     LambdaForm(String debugName,
 246                int arity, Name[] names, int result) {
 247         this(debugName, arity, names, result, true);
 248     }
 249     LambdaForm(String debugName,
 250                int arity, Name[] names, int result, boolean forceInline) {
 251         assert(namesOK(arity, names));
 252         this.arity = arity;
 253         this.result = fixResult(result, names);
 254         this.names = names.clone();
 255         this.debugName = fixDebugName(debugName);
 256         this.forceInline = forceInline;
 257         int maxOutArity = normalize();
 258         if (maxOutArity > MethodType.MAX_MH_INVOKER_ARITY) {
 259             // Cannot use LF interpreter on very high arity expressions.
 260             assert(maxOutArity <= MethodType.MAX_JVM_ARITY);
 261             compileToBytecode();
 262         }
 263     }
 264     LambdaForm(String debugName,
 265                int arity, Name[] names) {
 266         this(debugName, arity, names, LAST_RESULT, true);
 267     }
 268     LambdaForm(String debugName,
 269                int arity, Name[] names, boolean forceInline) {
 270         this(debugName, arity, names, LAST_RESULT, forceInline);
 271     }
 272     LambdaForm(String debugName,
 273                Name[] formals, Name[] temps, Name result) {
 274         this(debugName,
 275              formals.length, buildNames(formals, temps, result), LAST_RESULT, true);
 276     }
 277     LambdaForm(String debugName,
 278                Name[] formals, Name[] temps, Name result, boolean forceInline) {
 279         this(debugName,
 280              formals.length, buildNames(formals, temps, result), LAST_RESULT, forceInline);
 281     }
 282 
 283     private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {
 284         int arity = formals.length;
 285         int length = arity + temps.length + (result == null ? 0 : 1);
 286         Name[] names = Arrays.copyOf(formals, length);
 287         System.arraycopy(temps, 0, names, arity, temps.length);
 288         if (result != null)
 289             names[length - 1] = result;
 290         return names;
 291     }
 292 
 293     private LambdaForm(String sig) {
 294         this(sig, true);
 295     }
 296 
 297     private LambdaForm(String sig, boolean forceInline) {
 298         // Make a blank lambda form, which returns a constant zero or null.
 299         // It is used as a template for managing the invocation of similar forms that are non-empty.
 300         // Called only from getPreparedForm.
 301         assert(isValidSignature(sig));
 302         this.arity = signatureArity(sig);
 303         this.result = (signatureReturn(sig) == V_TYPE ? -1 : arity);
 304         this.names = buildEmptyNames(arity, sig);
 305         this.debugName = "LF.zero";
 306         this.forceInline = forceInline;
 307         assert(nameRefsAreLegal());
 308         assert(isEmpty());
 309         assert(sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();
 310     }
 311 
 312     private static Name[] buildEmptyNames(int arity, String basicTypeSignature) {
 313         assert(isValidSignature(basicTypeSignature));
 314         int resultPos = arity + 1;  // skip '_'
 315         if (arity < 0 || basicTypeSignature.length() != resultPos+1)
 316             throw new IllegalArgumentException("bad arity for "+basicTypeSignature);
 317         int numRes = (basicType(basicTypeSignature.charAt(resultPos)) == V_TYPE ? 0 : 1);
 318         Name[] names = arguments(numRes, basicTypeSignature.substring(0, arity));
 319         for (int i = 0; i < numRes; i++) {
 320             Name zero = new Name(constantZero(basicType(basicTypeSignature.charAt(resultPos + i))));
 321             names[arity + i] = zero.newIndex(arity + i);
 322         }
 323         return names;
 324     }
 325 
 326     private static int fixResult(int result, Name[] names) {
 327         if (result == LAST_RESULT)
 328             result = names.length - 1;  // might still be void
 329         if (result >= 0 && names[result].type == V_TYPE)
 330             result = VOID_RESULT;
 331         return result;
 332     }
 333 
 334     private static String fixDebugName(String debugName) {
 335         if (DEBUG_NAME_COUNTERS != null) {
 336             int under = debugName.indexOf('_');
 337             int length = debugName.length();
 338             if (under < 0)  under = length;
 339             String debugNameStem = debugName.substring(0, under);
 340             Integer ctr;
 341             synchronized (DEBUG_NAME_COUNTERS) {
 342                 ctr = DEBUG_NAME_COUNTERS.get(debugNameStem);
 343                 if (ctr == null)  ctr = 0;
 344                 DEBUG_NAME_COUNTERS.put(debugNameStem, ctr+1);
 345             }
 346             StringBuilder buf = new StringBuilder(debugNameStem);
 347             buf.append('_');
 348             int leadingZero = buf.length();
 349             buf.append((int) ctr);
 350             for (int i = buf.length() - leadingZero; i < 3; i++)
 351                 buf.insert(leadingZero, '0');
 352             if (under < length) {
 353                 ++under;    // skip "_"
 354                 while (under < length && Character.isDigit(debugName.charAt(under))) {
 355                     ++under;
 356                 }
 357                 if (under < length && debugName.charAt(under) == '_')  ++under;
 358                 if (under < length)
 359                     buf.append('_').append(debugName, under, length);
 360             }
 361             return buf.toString();
 362         }
 363         return debugName;
 364     }
 365 
 366     private static boolean namesOK(int arity, Name[] names) {
 367         for (int i = 0; i < names.length; i++) {
 368             Name n = names[i];
 369             assert(n != null) : "n is null";
 370             if (i < arity)
 371                 assert( n.isParam()) : n + " is not param at " + i;
 372             else
 373                 assert(!n.isParam()) : n + " is param at " + i;
 374         }
 375         return true;
 376     }
 377 
 378     /** Renumber and/or replace params so that they are interned and canonically numbered.
 379      *  @return maximum argument list length among the names (since we have to pass over them anyway)
 380      */
 381     private int normalize() {
 382         Name[] oldNames = null;
 383         int maxOutArity = 0;
 384         int changesStart = 0;
 385         for (int i = 0; i < names.length; i++) {
 386             Name n = names[i];
 387             if (!n.initIndex(i)) {
 388                 if (oldNames == null) {
 389                     oldNames = names.clone();
 390                     changesStart = i;
 391                 }
 392                 names[i] = n.cloneWithIndex(i);
 393             }
 394             if (n.arguments != null && maxOutArity < n.arguments.length)
 395                 maxOutArity = n.arguments.length;
 396         }
 397         if (oldNames != null) {
 398             int startFixing = arity;
 399             if (startFixing <= changesStart)
 400                 startFixing = changesStart+1;
 401             for (int i = startFixing; i < names.length; i++) {
 402                 Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);
 403                 names[i] = fixed.newIndex(i);
 404             }
 405         }
 406         assert(nameRefsAreLegal());
 407         int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);
 408         boolean needIntern = false;
 409         for (int i = 0; i < maxInterned; i++) {
 410             Name n = names[i], n2 = internArgument(n);
 411             if (n != n2) {
 412                 names[i] = n2;
 413                 needIntern = true;
 414             }
 415         }
 416         if (needIntern) {
 417             for (int i = arity; i < names.length; i++) {
 418                 names[i].internArguments();
 419             }
 420             assert(nameRefsAreLegal());
 421         }
 422         return maxOutArity;
 423     }
 424 
 425     /**
 426      * Check that all embedded Name references are localizable to this lambda,
 427      * and are properly ordered after their corresponding definitions.
 428      * <p>
 429      * Note that a Name can be local to multiple lambdas, as long as
 430      * it possesses the same index in each use site.
 431      * This allows Name references to be freely reused to construct
 432      * fresh lambdas, without confusion.
 433      */
 434     boolean nameRefsAreLegal() {
 435         assert(arity >= 0 && arity <= names.length);
 436         assert(result >= -1 && result < names.length);
 437         // Do all names possess an index consistent with their local definition order?
 438         for (int i = 0; i < arity; i++) {
 439             Name n = names[i];
 440             assert(n.index() == i) : Arrays.asList(n.index(), i);
 441             assert(n.isParam());
 442         }
 443         // Also, do all local name references
 444         for (int i = arity; i < names.length; i++) {
 445             Name n = names[i];
 446             assert(n.index() == i);
 447             for (Object arg : n.arguments) {
 448                 if (arg instanceof Name) {
 449                     Name n2 = (Name) arg;
 450                     int i2 = n2.index;
 451                     assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;
 452                     assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);
 453                     assert(i2 < i);  // ref must come after def!
 454                 }
 455             }
 456         }
 457         return true;
 458     }
 459 
 460     /** Invoke this form on the given arguments. */
 461     // final Object invoke(Object... args) throws Throwable {
 462     //     // NYI: fit this into the fast path?
 463     //     return interpretWithArguments(args);
 464     // }
 465 
 466     /** Report the return type. */
 467     BasicType returnType() {
 468         if (result < 0)  return V_TYPE;
 469         Name n = names[result];
 470         return n.type;
 471     }
 472 
 473     /** Report the N-th argument type. */
 474     BasicType parameterType(int n) {
 475         return parameter(n).type;
 476     }
 477 
 478     /** Report the N-th argument name. */
 479     Name parameter(int n) {
 480         assert(n < arity);
 481         Name param = names[n];
 482         assert(param.isParam());
 483         return param;
 484     }
 485 
 486     /** Report the N-th argument type constraint. */
 487     Object parameterConstraint(int n) {
 488         return parameter(n).constraint;
 489     }
 490 
 491     /** Report the arity. */
 492     int arity() {
 493         return arity;
 494     }
 495 
 496     /** Report the number of expressions (non-parameter names). */
 497     int expressionCount() {
 498         return names.length - arity;
 499     }
 500 
 501     /** Return the method type corresponding to my basic type signature. */
 502     MethodType methodType() {
 503         return signatureType(basicTypeSignature());
 504     }
 505     /** Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character. */
 506     final String basicTypeSignature() {
 507         StringBuilder buf = new StringBuilder(arity() + 3);
 508         for (int i = 0, a = arity(); i < a; i++)
 509             buf.append(parameterType(i).basicTypeChar());
 510         return buf.append('_').append(returnType().basicTypeChar()).toString();
 511     }
 512     static int signatureArity(String sig) {
 513         assert(isValidSignature(sig));
 514         return sig.indexOf('_');
 515     }
 516     static BasicType signatureReturn(String sig) {
 517         return basicType(sig.charAt(signatureArity(sig) + 1));
 518     }
 519     static boolean isValidSignature(String sig) {
 520         int arity = sig.indexOf('_');
 521         if (arity < 0)  return false;  // must be of the form *_*
 522         int siglen = sig.length();
 523         if (siglen != arity + 2)  return false;  // *_X
 524         for (int i = 0; i < siglen; i++) {
 525             if (i == arity)  continue;  // skip '_'
 526             char c = sig.charAt(i);
 527             if (c == 'V')
 528                 return (i == siglen - 1 && arity == siglen - 2);
 529             if (!isArgBasicTypeChar(c))  return false; // must be [LIJFD]
 530         }
 531         return true;  // [LIJFD]*_[LIJFDV]
 532     }
 533     static MethodType signatureType(String sig) {
 534         Class<?>[] ptypes = new Class<?>[signatureArity(sig)];
 535         for (int i = 0; i < ptypes.length; i++)
 536             ptypes[i] = basicType(sig.charAt(i)).btClass;
 537         Class<?> rtype = signatureReturn(sig).btClass;
 538         return MethodType.methodType(rtype, ptypes);
 539     }
 540 
 541     /*
 542      * Code generation issues:
 543      *
 544      * Compiled LFs should be reusable in general.
 545      * The biggest issue is how to decide when to pull a name into
 546      * the bytecode, versus loading a reified form from the MH data.
 547      *
 548      * For example, an asType wrapper may require execution of a cast
 549      * after a call to a MH.  The target type of the cast can be placed
 550      * as a constant in the LF itself.  This will force the cast type
 551      * to be compiled into the bytecodes and native code for the MH.
 552      * Or, the target type of the cast can be erased in the LF, and
 553      * loaded from the MH data.  (Later on, if the MH as a whole is
 554      * inlined, the data will flow into the inlined instance of the LF,
 555      * as a constant, and the end result will be an optimal cast.)
 556      *
 557      * This erasure of cast types can be done with any use of
 558      * reference types.  It can also be done with whole method
 559      * handles.  Erasing a method handle might leave behind
 560      * LF code that executes correctly for any MH of a given
 561      * type, and load the required MH from the enclosing MH's data.
 562      * Or, the erasure might even erase the expected MT.
 563      *
 564      * Also, for direct MHs, the MemberName of the target
 565      * could be erased, and loaded from the containing direct MH.
 566      * As a simple case, a LF for all int-valued non-static
 567      * field getters would perform a cast on its input argument
 568      * (to non-constant base type derived from the MemberName)
 569      * and load an integer value from the input object
 570      * (at a non-constant offset also derived from the MemberName).
 571      * Such MN-erased LFs would be inlinable back to optimized
 572      * code, whenever a constant enclosing DMH is available
 573      * to supply a constant MN from its data.
 574      *
 575      * The main problem here is to keep LFs reasonably generic,
 576      * while ensuring that hot spots will inline good instances.
 577      * "Reasonably generic" means that we don't end up with
 578      * repeated versions of bytecode or machine code that do
 579      * not differ in their optimized form.  Repeated versions
 580      * of machine would have the undesirable overheads of
 581      * (a) redundant compilation work and (b) extra I$ pressure.
 582      * To control repeated versions, we need to be ready to
 583      * erase details from LFs and move them into MH data,
 584      * whevener those details are not relevant to significant
 585      * optimization.  "Significant" means optimization of
 586      * code that is actually hot.
 587      *
 588      * Achieving this may require dynamic splitting of MHs, by replacing
 589      * a generic LF with a more specialized one, on the same MH,
 590      * if (a) the MH is frequently executed and (b) the MH cannot
 591      * be inlined into a containing caller, such as an invokedynamic.
 592      *
 593      * Compiled LFs that are no longer used should be GC-able.
 594      * If they contain non-BCP references, they should be properly
 595      * interlinked with the class loader(s) that their embedded types
 596      * depend on.  This probably means that reusable compiled LFs
 597      * will be tabulated (indexed) on relevant class loaders,
 598      * or else that the tables that cache them will have weak links.
 599      */
 600 
 601     /**
 602      * Make this LF directly executable, as part of a MethodHandle.
 603      * Invariant:  Every MH which is invoked must prepare its LF
 604      * before invocation.
 605      * (In principle, the JVM could do this very lazily,
 606      * as a sort of pre-invocation linkage step.)
 607      */
 608     public void prepare() {
 609         if (COMPILE_THRESHOLD == 0) {
 610             compileToBytecode();
 611         }
 612         if (this.vmentry != null) {
 613             // already prepared (e.g., a primitive DMH invoker form)
 614             return;
 615         }
 616         LambdaForm prep = getPreparedForm(basicTypeSignature());
 617         this.vmentry = prep.vmentry;
 618         // TO DO: Maybe add invokeGeneric, invokeWithArguments
 619     }
 620 
 621     /** Generate optimizable bytecode for this form. */
 622     MemberName compileToBytecode() {
 623         MethodType invokerType = methodType();
 624         assert(vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));
 625         if (vmentry != null && isCompiled) {
 626             return vmentry;  // already compiled somehow
 627         }
 628         try {
 629             vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);
 630             if (TRACE_INTERPRETER)
 631                 traceInterpreter("compileToBytecode", this);
 632             isCompiled = true;
 633             return vmentry;
 634         } catch (Error | Exception ex) {
 635             throw newInternalError(this.toString(), ex);
 636         }
 637     }
 638 
 639     private static void computeInitialPreparedForms() {
 640         // Find all predefined invokers and associate them with canonical empty lambda forms.
 641         for (MemberName m : MemberName.getFactory().getMethods(LambdaForm.class, false, null, null, null)) {
 642             if (!m.isStatic() || !m.isPackage())  continue;
 643             MethodType mt = m.getMethodType();
 644             if (mt.parameterCount() > 0 &&
 645                 mt.parameterType(0) == MethodHandle.class &&
 646                 m.getName().startsWith("interpret_")) {
 647                 String sig = basicTypeSignature(mt);
 648                 assert(m.getName().equals("interpret" + sig.substring(sig.indexOf('_'))));
 649                 LambdaForm form = new LambdaForm(sig);
 650                 form.vmentry = m;
 651                 form = mt.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, form);
 652             }
 653         }
 654     }
 655 
 656     // Set this false to disable use of the interpret_L methods defined in this file.
 657     private static final boolean USE_PREDEFINED_INTERPRET_METHODS = true;
 658 
 659     // The following are predefined exact invokers.  The system must build
 660     // a separate invoker for each distinct signature.
 661     static Object interpret_L(MethodHandle mh) throws Throwable {
 662         Object[] av = {mh};
 663         String sig = null;
 664         assert(argumentTypesMatch(sig = "L_L", av));
 665         Object res = mh.form.interpretWithArguments(av);
 666         assert(returnTypesMatch(sig, av, res));
 667         return res;
 668     }
 669     static Object interpret_L(MethodHandle mh, Object x1) throws Throwable {
 670         Object[] av = {mh, x1};
 671         String sig = null;
 672         assert(argumentTypesMatch(sig = "LL_L", av));
 673         Object res = mh.form.interpretWithArguments(av);
 674         assert(returnTypesMatch(sig, av, res));
 675         return res;
 676     }
 677     static Object interpret_L(MethodHandle mh, Object x1, Object x2) throws Throwable {
 678         Object[] av = {mh, x1, x2};
 679         String sig = null;
 680         assert(argumentTypesMatch(sig = "LLL_L", av));
 681         Object res = mh.form.interpretWithArguments(av);
 682         assert(returnTypesMatch(sig, av, res));
 683         return res;
 684     }
 685     private static LambdaForm getPreparedForm(String sig) {
 686         MethodType mtype = signatureType(sig);
 687         LambdaForm prep =  mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);
 688         if (prep != null)  return prep;
 689         assert(isValidSignature(sig));
 690         prep = new LambdaForm(sig);
 691         prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(sig);
 692         return mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);
 693     }
 694 
 695     // The next few routines are called only from assert expressions
 696     // They verify that the built-in invokers process the correct raw data types.
 697     private static boolean argumentTypesMatch(String sig, Object[] av) {
 698         int arity = signatureArity(sig);
 699         assert(av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;
 700         assert(av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];
 701         MethodHandle mh = (MethodHandle) av[0];
 702         MethodType mt = mh.type();
 703         assert(mt.parameterCount() == arity-1);
 704         for (int i = 0; i < av.length; i++) {
 705             Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i-1));
 706             assert(valueMatches(basicType(sig.charAt(i)), pt, av[i]));
 707         }
 708         return true;
 709     }
 710     private static boolean valueMatches(BasicType tc, Class<?> type, Object x) {
 711         // The following line is needed because (...)void method handles can use non-void invokers
 712         if (type == void.class)  tc = V_TYPE;   // can drop any kind of value
 713         assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);
 714         switch (tc) {
 715         case I_TYPE: assert checkInt(type, x)   : "checkInt(" + type + "," + x +")";   break;
 716         case J_TYPE: assert x instanceof Long   : "instanceof Long: " + x;             break;
 717         case F_TYPE: assert x instanceof Float  : "instanceof Float: " + x;            break;
 718         case D_TYPE: assert x instanceof Double : "instanceof Double: " + x;           break;
 719         case L_TYPE: assert checkRef(type, x)   : "checkRef(" + type + "," + x + ")";  break;
 720         case V_TYPE: break;  // allow anything here; will be dropped
 721         default:  assert(false);
 722         }
 723         return true;
 724     }
 725     private static boolean returnTypesMatch(String sig, Object[] av, Object res) {
 726         MethodHandle mh = (MethodHandle) av[0];
 727         return valueMatches(signatureReturn(sig), mh.type().returnType(), res);
 728     }
 729     private static boolean checkInt(Class<?> type, Object x) {
 730         assert(x instanceof Integer);
 731         if (type == int.class)  return true;
 732         Wrapper w = Wrapper.forBasicType(type);
 733         assert(w.isSubwordOrInt());
 734         Object x1 = Wrapper.INT.wrap(w.wrap(x));
 735         return x.equals(x1);
 736     }
 737     private static boolean checkRef(Class<?> type, Object x) {
 738         assert(!type.isPrimitive());
 739         if (x == null)  return true;
 740         if (type.isInterface())  return true;
 741         return type.isInstance(x);
 742     }
 743 
 744     /** If the invocation count hits the threshold we spin bytecodes and call that subsequently. */
 745     private static final int COMPILE_THRESHOLD;
 746     static {
 747         COMPILE_THRESHOLD = Math.max(-1, MethodHandleStatics.COMPILE_THRESHOLD);
 748     }
 749     private int invocationCounter = 0;
 750 
 751     @Hidden
 752     @DontInline
 753     /** Interpretively invoke this form on the given arguments. */
 754     Object interpretWithArguments(Object... argumentValues) throws Throwable {
 755         if (TRACE_INTERPRETER)
 756             return interpretWithArgumentsTracing(argumentValues);
 757         checkInvocationCounter();
 758         assert(arityCheck(argumentValues));
 759         Object[] values = Arrays.copyOf(argumentValues, names.length);
 760         for (int i = argumentValues.length; i < values.length; i++) {
 761             values[i] = interpretName(names[i], values);
 762         }
 763         Object rv = (result < 0) ? null : values[result];
 764         assert(resultCheck(argumentValues, rv));
 765         return rv;
 766     }
 767 
 768     @Hidden
 769     @DontInline
 770     /** Evaluate a single Name within this form, applying its function to its arguments. */
 771     Object interpretName(Name name, Object[] values) throws Throwable {
 772         if (TRACE_INTERPRETER)
 773             traceInterpreter("| interpretName", name.debugString(), (Object[]) null);
 774         Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);
 775         for (int i = 0; i < arguments.length; i++) {
 776             Object a = arguments[i];
 777             if (a instanceof Name) {
 778                 int i2 = ((Name)a).index();
 779                 assert(names[i2] == a);
 780                 a = values[i2];
 781                 arguments[i] = a;
 782             }
 783         }
 784         return name.function.invokeWithArguments(arguments);
 785     }
 786 
 787     private void checkInvocationCounter() {
 788         if (COMPILE_THRESHOLD != 0 &&
 789             invocationCounter < COMPILE_THRESHOLD) {
 790             invocationCounter++;  // benign race
 791             if (invocationCounter >= COMPILE_THRESHOLD) {
 792                 // Replace vmentry with a bytecode version of this LF.
 793                 compileToBytecode();
 794             }
 795         }
 796     }
 797     Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {
 798         traceInterpreter("[ interpretWithArguments", this, argumentValues);
 799         if (invocationCounter < COMPILE_THRESHOLD) {
 800             int ctr = invocationCounter++;  // benign race
 801             traceInterpreter("| invocationCounter", ctr);
 802             if (invocationCounter >= COMPILE_THRESHOLD) {
 803                 compileToBytecode();
 804             }
 805         }
 806         Object rval;
 807         try {
 808             assert(arityCheck(argumentValues));
 809             Object[] values = Arrays.copyOf(argumentValues, names.length);
 810             for (int i = argumentValues.length; i < values.length; i++) {
 811                 values[i] = interpretName(names[i], values);
 812             }
 813             rval = (result < 0) ? null : values[result];
 814         } catch (Throwable ex) {
 815             traceInterpreter("] throw =>", ex);
 816             throw ex;
 817         }
 818         traceInterpreter("] return =>", rval);
 819         return rval;
 820     }
 821 
 822     static void traceInterpreter(String event, Object obj, Object... args) {
 823         if (TRACE_INTERPRETER) {
 824             System.out.println("LFI: "+event+" "+(obj != null ? obj : "")+(args != null && args.length != 0 ? Arrays.asList(args) : ""));
 825         }
 826     }
 827     static void traceInterpreter(String event, Object obj) {
 828         traceInterpreter(event, obj, (Object[])null);
 829     }
 830     private boolean arityCheck(Object[] argumentValues) {
 831         assert(argumentValues.length == arity) : arity+"!="+Arrays.asList(argumentValues)+".length";
 832         // also check that the leading (receiver) argument is somehow bound to this LF:
 833         assert(argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];
 834         MethodHandle mh = (MethodHandle) argumentValues[0];
 835         assert(mh.internalForm() == this);
 836         // note:  argument #0 could also be an interface wrapper, in the future
 837         argumentTypesMatch(basicTypeSignature(), argumentValues);
 838         return true;
 839     }
 840     private boolean resultCheck(Object[] argumentValues, Object result) {
 841         MethodHandle mh = (MethodHandle) argumentValues[0];
 842         MethodType mt = mh.type();
 843         assert(valueMatches(returnType(), mt.returnType(), result));
 844         return true;
 845     }
 846 
 847     private boolean isEmpty() {
 848         if (result < 0)
 849             return (names.length == arity);
 850         else if (result == arity && names.length == arity + 1)
 851             return names[arity].isConstantZero();
 852         else
 853             return false;
 854     }
 855 
 856     public String toString() {
 857         StringBuilder buf = new StringBuilder(debugName+"=Lambda(");
 858         for (int i = 0; i < names.length; i++) {
 859             if (i == arity)  buf.append(")=>{");
 860             Name n = names[i];
 861             if (i >= arity)  buf.append("\n    ");
 862             buf.append(n.paramString());
 863             if (i < arity) {
 864                 if (i+1 < arity)  buf.append(",");
 865                 continue;
 866             }
 867             buf.append("=").append(n.exprString());
 868             buf.append(";");
 869         }
 870         if (arity == names.length)  buf.append(")=>{");
 871         buf.append(result < 0 ? "void" : names[result]).append("}");
 872         if (TRACE_INTERPRETER) {
 873             // Extra verbosity:
 874             buf.append(":").append(basicTypeSignature());
 875             buf.append("/").append(vmentry);
 876         }
 877         return buf.toString();
 878     }
 879 
 880     @Override
 881     public boolean equals(Object obj) {
 882         return obj instanceof LambdaForm && equals((LambdaForm)obj);
 883     }
 884     public boolean equals(LambdaForm that) {
 885         if (this.result != that.result)  return false;
 886         return Arrays.equals(this.names, that.names);
 887     }
 888     public int hashCode() {
 889         return result + 31 * Arrays.hashCode(names);
 890     }
 891     LambdaFormEditor editor() {
 892         return LambdaFormEditor.lambdaFormEditor(this);
 893     }
 894 
 895     boolean contains(Name name) {
 896         int pos = name.index();
 897         if (pos >= 0) {
 898             return pos < names.length && name.equals(names[pos]);
 899         }
 900         for (int i = arity; i < names.length; i++) {
 901             if (name.equals(names[i]))
 902                 return true;
 903         }
 904         return false;
 905     }
 906 
 907     LambdaForm addArguments(int pos, BasicType... types) {
 908         // names array has MH in slot 0; skip it.
 909         int argpos = pos + 1;
 910         assert(argpos <= arity);
 911         int length = names.length;
 912         int inTypes = types.length;
 913         Name[] names2 = Arrays.copyOf(names, length + inTypes);
 914         int arity2 = arity + inTypes;
 915         int result2 = result;
 916         if (result2 >= argpos)
 917             result2 += inTypes;
 918         // Note:  The LF constructor will rename names2[argpos...].
 919         // Make space for new arguments (shift temporaries).
 920         System.arraycopy(names, argpos, names2, argpos + inTypes, length - argpos);
 921         for (int i = 0; i < inTypes; i++) {
 922             names2[argpos + i] = new Name(types[i]);
 923         }
 924         return new LambdaForm(debugName, arity2, names2, result2);
 925     }
 926 
 927     LambdaForm addArguments(int pos, List<Class<?>> types) {
 928         return addArguments(pos, basicTypes(types));
 929     }
 930 
 931     LambdaForm permuteArguments(int skip, int[] reorder, BasicType[] types) {
 932         // Note:  When inArg = reorder[outArg], outArg is fed by a copy of inArg.
 933         // The types are the types of the new (incoming) arguments.
 934         int length = names.length;
 935         int inTypes = types.length;
 936         int outArgs = reorder.length;
 937         assert(skip+outArgs == arity);
 938         assert(permutedTypesMatch(reorder, types, names, skip));
 939         int pos = 0;
 940         // skip trivial first part of reordering:
 941         while (pos < outArgs && reorder[pos] == pos)  pos += 1;
 942         Name[] names2 = new Name[length - outArgs + inTypes];
 943         System.arraycopy(names, 0, names2, 0, skip+pos);
 944         // copy the body:
 945         int bodyLength = length - arity;
 946         System.arraycopy(names, skip+outArgs, names2, skip+inTypes, bodyLength);
 947         int arity2 = names2.length - bodyLength;
 948         int result2 = result;
 949         if (result2 >= 0) {
 950             if (result2 < skip+outArgs) {
 951                 // return the corresponding inArg
 952                 result2 = reorder[result2-skip];
 953             } else {
 954                 result2 = result2 - outArgs + inTypes;
 955             }
 956         }
 957         // rework names in the body:
 958         for (int j = pos; j < outArgs; j++) {
 959             Name n = names[skip+j];
 960             int i = reorder[j];
 961             // replace names[skip+j] by names2[skip+i]
 962             Name n2 = names2[skip+i];
 963             if (n2 == null)
 964                 names2[skip+i] = n2 = new Name(types[i]);
 965             else
 966                 assert(n2.type == types[i]);
 967             for (int k = arity2; k < names2.length; k++) {
 968                 names2[k] = names2[k].replaceName(n, n2);
 969             }
 970         }
 971         // some names are unused, but must be filled in
 972         for (int i = skip+pos; i < arity2; i++) {
 973             if (names2[i] == null)
 974                 names2[i] = argument(i, types[i - skip]);
 975         }
 976         for (int j = arity; j < names.length; j++) {
 977             int i = j - arity + arity2;
 978             // replace names2[i] by names[j]
 979             Name n = names[j];
 980             Name n2 = names2[i];
 981             if (n != n2) {
 982                 for (int k = i+1; k < names2.length; k++) {
 983                     names2[k] = names2[k].replaceName(n, n2);
 984                 }
 985             }
 986         }
 987         return new LambdaForm(debugName, arity2, names2, result2);
 988     }
 989 
 990     static boolean permutedTypesMatch(int[] reorder, BasicType[] types, Name[] names, int skip) {
 991         int inTypes = types.length;
 992         int outArgs = reorder.length;
 993         for (int i = 0; i < outArgs; i++) {
 994             assert(names[skip+i].isParam());
 995             assert(names[skip+i].type == types[reorder[i]]);
 996         }
 997         return true;
 998     }
 999 
1000     static class NamedFunction {
1001         final MemberName member;
1002         @Stable MethodHandle resolvedHandle;
1003         @Stable MethodHandle invoker;
1004 
1005         NamedFunction(MethodHandle resolvedHandle) {
1006             this(resolvedHandle.internalMemberName(), resolvedHandle);
1007         }
1008         NamedFunction(MemberName member, MethodHandle resolvedHandle) {
1009             this.member = member;
1010             this.resolvedHandle = resolvedHandle;
1011              // The following assert is almost always correct, but will fail for corner cases, such as PrivateInvokeTest.
1012              //assert(!isInvokeBasic());
1013         }
1014         NamedFunction(MethodType basicInvokerType) {
1015             assert(basicInvokerType == basicInvokerType.basicType()) : basicInvokerType;
1016             if (basicInvokerType.parameterSlotCount() < MethodType.MAX_MH_INVOKER_ARITY) {
1017                 this.resolvedHandle = basicInvokerType.invokers().basicInvoker();
1018                 this.member = resolvedHandle.internalMemberName();
1019             } else {
1020                 // necessary to pass BigArityTest
1021                 this.member = Invokers.invokeBasicMethod(basicInvokerType);
1022             }
1023             assert(isInvokeBasic());
1024         }
1025 
1026         private boolean isInvokeBasic() {
1027             return member != null &&
1028                    member.isMethodHandleInvoke() &&
1029                    "invokeBasic".equals(member.getName());
1030         }
1031 
1032         // The next 3 constructors are used to break circular dependencies on MH.invokeStatic, etc.
1033         // Any LambdaForm containing such a member is not interpretable.
1034         // This is OK, since all such LFs are prepared with special primitive vmentry points.
1035         // And even without the resolvedHandle, the name can still be compiled and optimized.
1036         NamedFunction(Method method) {
1037             this(new MemberName(method));
1038         }
1039         NamedFunction(Field field) {
1040             this(new MemberName(field));
1041         }
1042         NamedFunction(MemberName member) {
1043             this.member = member;
1044             this.resolvedHandle = null;
1045         }
1046 
1047         MethodHandle resolvedHandle() {
1048             if (resolvedHandle == null)  resolve();
1049             return resolvedHandle;
1050         }
1051 
1052         void resolve() {
1053             resolvedHandle = DirectMethodHandle.make(member);
1054         }
1055 
1056         @Override
1057         public boolean equals(Object other) {
1058             if (this == other) return true;
1059             if (other == null) return false;
1060             if (!(other instanceof NamedFunction)) return false;
1061             NamedFunction that = (NamedFunction) other;
1062             return this.member != null && this.member.equals(that.member);
1063         }
1064 
1065         @Override
1066         public int hashCode() {
1067             if (member != null)
1068                 return member.hashCode();
1069             return super.hashCode();
1070         }
1071 
1072         // Put the predefined NamedFunction invokers into the table.
1073         static void initializeInvokers() {
1074             for (MemberName m : MemberName.getFactory().getMethods(NamedFunction.class, false, null, null, null)) {
1075                 if (!m.isStatic() || !m.isPackage())  continue;
1076                 MethodType type = m.getMethodType();
1077                 if (type.equals(INVOKER_METHOD_TYPE) &&
1078                     m.getName().startsWith("invoke_")) {
1079                     String sig = m.getName().substring("invoke_".length());
1080                     int arity = LambdaForm.signatureArity(sig);
1081                     MethodType srcType = MethodType.genericMethodType(arity);
1082                     if (LambdaForm.signatureReturn(sig) == V_TYPE)
1083                         srcType = srcType.changeReturnType(void.class);
1084                     MethodTypeForm typeForm = srcType.form();
1085                     typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, DirectMethodHandle.make(m));
1086                 }
1087             }
1088         }
1089 
1090         // The following are predefined NamedFunction invokers.  The system must build
1091         // a separate invoker for each distinct signature.
1092         /** void return type invokers. */
1093         @Hidden
1094         static Object invoke__V(MethodHandle mh, Object[] a) throws Throwable {
1095             assert(arityCheck(0, void.class, mh, a));
1096             mh.invokeBasic();
1097             return null;
1098         }
1099         @Hidden
1100         static Object invoke_L_V(MethodHandle mh, Object[] a) throws Throwable {
1101             assert(arityCheck(1, void.class, mh, a));
1102             mh.invokeBasic(a[0]);
1103             return null;
1104         }
1105         @Hidden
1106         static Object invoke_LL_V(MethodHandle mh, Object[] a) throws Throwable {
1107             assert(arityCheck(2, void.class, mh, a));
1108             mh.invokeBasic(a[0], a[1]);
1109             return null;
1110         }
1111         @Hidden
1112         static Object invoke_LLL_V(MethodHandle mh, Object[] a) throws Throwable {
1113             assert(arityCheck(3, void.class, mh, a));
1114             mh.invokeBasic(a[0], a[1], a[2]);
1115             return null;
1116         }
1117         @Hidden
1118         static Object invoke_LLLL_V(MethodHandle mh, Object[] a) throws Throwable {
1119             assert(arityCheck(4, void.class, mh, a));
1120             mh.invokeBasic(a[0], a[1], a[2], a[3]);
1121             return null;
1122         }
1123         @Hidden
1124         static Object invoke_LLLLL_V(MethodHandle mh, Object[] a) throws Throwable {
1125             assert(arityCheck(5, void.class, mh, a));
1126             mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
1127             return null;
1128         }
1129         /** Object return type invokers. */
1130         @Hidden
1131         static Object invoke__L(MethodHandle mh, Object[] a) throws Throwable {
1132             assert(arityCheck(0, mh, a));
1133             return mh.invokeBasic();
1134         }
1135         @Hidden
1136         static Object invoke_L_L(MethodHandle mh, Object[] a) throws Throwable {
1137             assert(arityCheck(1, mh, a));
1138             return mh.invokeBasic(a[0]);
1139         }
1140         @Hidden
1141         static Object invoke_LL_L(MethodHandle mh, Object[] a) throws Throwable {
1142             assert(arityCheck(2, mh, a));
1143             return mh.invokeBasic(a[0], a[1]);
1144         }
1145         @Hidden
1146         static Object invoke_LLL_L(MethodHandle mh, Object[] a) throws Throwable {
1147             assert(arityCheck(3, mh, a));
1148             return mh.invokeBasic(a[0], a[1], a[2]);
1149         }
1150         @Hidden
1151         static Object invoke_LLLL_L(MethodHandle mh, Object[] a) throws Throwable {
1152             assert(arityCheck(4, mh, a));
1153             return mh.invokeBasic(a[0], a[1], a[2], a[3]);
1154         }
1155         @Hidden
1156         static Object invoke_LLLLL_L(MethodHandle mh, Object[] a) throws Throwable {
1157             assert(arityCheck(5, mh, a));
1158             return mh.invokeBasic(a[0], a[1], a[2], a[3], a[4]);
1159         }
1160         private static boolean arityCheck(int arity, MethodHandle mh, Object[] a) {
1161             return arityCheck(arity, Object.class, mh, a);
1162         }
1163         private static boolean arityCheck(int arity, Class<?> rtype, MethodHandle mh, Object[] a) {
1164             assert(a.length == arity)
1165                     : Arrays.asList(a.length, arity);
1166             assert(mh.type().basicType() == MethodType.genericMethodType(arity).changeReturnType(rtype))
1167                     : Arrays.asList(mh, rtype, arity);
1168             MemberName member = mh.internalMemberName();
1169             if (member != null && member.getName().equals("invokeBasic") && member.isMethodHandleInvoke()) {
1170                 assert(arity > 0);
1171                 assert(a[0] instanceof MethodHandle);
1172                 MethodHandle mh2 = (MethodHandle) a[0];
1173                 assert(mh2.type().basicType() == MethodType.genericMethodType(arity-1).changeReturnType(rtype))
1174                         : Arrays.asList(member, mh2, rtype, arity);
1175             }
1176             return true;
1177         }
1178 
1179         static final MethodType INVOKER_METHOD_TYPE =
1180             MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1181 
1182         private static MethodHandle computeInvoker(MethodTypeForm typeForm) {
1183             typeForm = typeForm.basicType().form();  // normalize to basic type
1184             MethodHandle mh = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
1185             if (mh != null)  return mh;
1186             MemberName invoker = InvokerBytecodeGenerator.generateNamedFunctionInvoker(typeForm);  // this could take a while
1187             mh = DirectMethodHandle.make(invoker);
1188             MethodHandle mh2 = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
1189             if (mh2 != null)  return mh2;  // benign race
1190             if (!mh.type().equals(INVOKER_METHOD_TYPE))
1191                 throw newInternalError(mh.debugString());
1192             return typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, mh);
1193         }
1194 
1195         @Hidden
1196         Object invokeWithArguments(Object... arguments) throws Throwable {
1197             // If we have a cached invoker, call it right away.
1198             // NOTE: The invoker always returns a reference value.
1199             if (TRACE_INTERPRETER)  return invokeWithArgumentsTracing(arguments);
1200             assert(checkArgumentTypes(arguments, methodType()));
1201             return invoker().invokeBasic(resolvedHandle(), arguments);
1202         }
1203 
1204         @Hidden
1205         Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {
1206             Object rval;
1207             try {
1208                 traceInterpreter("[ call", this, arguments);
1209                 if (invoker == null) {
1210                     traceInterpreter("| getInvoker", this);
1211                     invoker();
1212                 }
1213                 if (resolvedHandle == null) {
1214                     traceInterpreter("| resolve", this);
1215                     resolvedHandle();
1216                 }
1217                 assert(checkArgumentTypes(arguments, methodType()));
1218                 rval = invoker().invokeBasic(resolvedHandle(), arguments);
1219             } catch (Throwable ex) {
1220                 traceInterpreter("] throw =>", ex);
1221                 throw ex;
1222             }
1223             traceInterpreter("] return =>", rval);
1224             return rval;
1225         }
1226 
1227         private MethodHandle invoker() {
1228             if (invoker != null)  return invoker;
1229             // Get an invoker and cache it.
1230             return invoker = computeInvoker(methodType().form());
1231         }
1232 
1233         private static boolean checkArgumentTypes(Object[] arguments, MethodType methodType) {
1234             if (true)  return true;  // FIXME
1235             MethodType dstType = methodType.form().erasedType();
1236             MethodType srcType = dstType.basicType().wrap();
1237             Class<?>[] ptypes = new Class<?>[arguments.length];
1238             for (int i = 0; i < arguments.length; i++) {
1239                 Object arg = arguments[i];
1240                 Class<?> ptype = arg == null ? Object.class : arg.getClass();
1241                 // If the dest. type is a primitive we keep the
1242                 // argument type.
1243                 ptypes[i] = dstType.parameterType(i).isPrimitive() ? ptype : Object.class;
1244             }
1245             MethodType argType = MethodType.methodType(srcType.returnType(), ptypes).wrap();
1246             assert(argType.isConvertibleTo(srcType)) : "wrong argument types: cannot convert " + argType + " to " + srcType;
1247             return true;
1248         }
1249 
1250         MethodType methodType() {
1251             if (resolvedHandle != null)
1252                 return resolvedHandle.type();
1253             else
1254                 // only for certain internal LFs during bootstrapping
1255                 return member.getInvocationType();
1256         }
1257 
1258         MemberName member() {
1259             assert(assertMemberIsConsistent());
1260             return member;
1261         }
1262 
1263         // Called only from assert.
1264         private boolean assertMemberIsConsistent() {
1265             if (resolvedHandle instanceof DirectMethodHandle) {
1266                 MemberName m = resolvedHandle.internalMemberName();
1267                 assert(m.equals(member));
1268             }
1269             return true;
1270         }
1271 
1272         Class<?> memberDeclaringClassOrNull() {
1273             return (member == null) ? null : member.getDeclaringClass();
1274         }
1275 
1276         BasicType returnType() {
1277             return basicType(methodType().returnType());
1278         }
1279 
1280         BasicType parameterType(int n) {
1281             return basicType(methodType().parameterType(n));
1282         }
1283 
1284         int arity() {
1285             return methodType().parameterCount();
1286         }
1287 
1288         public String toString() {
1289             if (member == null)  return String.valueOf(resolvedHandle);
1290             return member.getDeclaringClass().getSimpleName()+"."+member.getName();
1291         }
1292 
1293         public boolean isIdentity() {
1294             return this.equals(identity(returnType()));
1295         }
1296 
1297         public boolean isConstantZero() {
1298             return this.equals(constantZero(returnType()));
1299         }
1300 
1301         public MethodHandleImpl.Intrinsic intrinsicName() {
1302             return resolvedHandle == null ? MethodHandleImpl.Intrinsic.NONE
1303                                           : resolvedHandle.intrinsicName();
1304         }
1305     }
1306 
1307     public static String basicTypeSignature(MethodType type) {
1308         char[] sig = new char[type.parameterCount() + 2];
1309         int sigp = 0;
1310         for (Class<?> pt : type.parameterList()) {
1311             sig[sigp++] = basicTypeChar(pt);
1312         }
1313         sig[sigp++] = '_';
1314         sig[sigp++] = basicTypeChar(type.returnType());
1315         assert(sigp == sig.length);
1316         return String.valueOf(sig);
1317     }
1318     public static String shortenSignature(String signature) {
1319         // Hack to make signatures more readable when they show up in method names.
1320         final int NO_CHAR = -1, MIN_RUN = 3;
1321         int c0, c1 = NO_CHAR, c1reps = 0;
1322         StringBuilder buf = null;
1323         int len = signature.length();
1324         if (len < MIN_RUN)  return signature;
1325         for (int i = 0; i <= len; i++) {
1326             // shift in the next char:
1327             c0 = c1; c1 = (i == len ? NO_CHAR : signature.charAt(i));
1328             if (c1 == c0) { ++c1reps; continue; }
1329             // shift in the next count:
1330             int c0reps = c1reps; c1reps = 1;
1331             // end of a  character run
1332             if (c0reps < MIN_RUN) {
1333                 if (buf != null) {
1334                     while (--c0reps >= 0)
1335                         buf.append((char)c0);
1336                 }
1337                 continue;
1338             }
1339             // found three or more in a row
1340             if (buf == null)
1341                 buf = new StringBuilder().append(signature, 0, i - c0reps);
1342             buf.append((char)c0).append(c0reps);
1343         }
1344         return (buf == null) ? signature : buf.toString();
1345     }
1346 
1347     static final class Name {
1348         final BasicType type;
1349         private short index;
1350         final NamedFunction function;
1351         final Object constraint;  // additional type information, if not null
1352         @Stable final Object[] arguments;
1353 
1354         private Name(int index, BasicType type, NamedFunction function, Object[] arguments) {
1355             this.index = (short)index;
1356             this.type = type;
1357             this.function = function;
1358             this.arguments = arguments;
1359             this.constraint = null;
1360             assert(this.index == index);
1361         }
1362         private Name(Name that, Object constraint) {
1363             this.index = that.index;
1364             this.type = that.type;
1365             this.function = that.function;
1366             this.arguments = that.arguments;
1367             this.constraint = constraint;
1368             assert(constraint == null || isParam());  // only params have constraints
1369             assert(constraint == null || constraint instanceof BoundMethodHandle.SpeciesData || constraint instanceof Class);
1370         }
1371         Name(MethodHandle function, Object... arguments) {
1372             this(new NamedFunction(function), arguments);
1373         }
1374         Name(MethodType functionType, Object... arguments) {
1375             this(new NamedFunction(functionType), arguments);
1376             assert(arguments[0] instanceof Name && ((Name)arguments[0]).type == L_TYPE);
1377         }
1378         Name(MemberName function, Object... arguments) {
1379             this(new NamedFunction(function), arguments);
1380         }
1381         Name(NamedFunction function, Object... arguments) {
1382             this(-1, function.returnType(), function, arguments = Arrays.copyOf(arguments, arguments.length, Object[].class));
1383             assert(arguments.length == function.arity()) : "arity mismatch: arguments.length=" + arguments.length + " == function.arity()=" + function.arity() + " in " + debugString();
1384             for (int i = 0; i < arguments.length; i++)
1385                 assert(typesMatch(function.parameterType(i), arguments[i])) : "types don't match: function.parameterType(" + i + ")=" + function.parameterType(i) + ", arguments[" + i + "]=" + arguments[i] + " in " + debugString();
1386         }
1387         /** Create a raw parameter of the given type, with an expected index. */
1388         Name(int index, BasicType type) {
1389             this(index, type, null, null);
1390         }
1391         /** Create a raw parameter of the given type. */
1392         Name(BasicType type) { this(-1, type); }
1393 
1394         BasicType type() { return type; }
1395         int index() { return index; }
1396         boolean initIndex(int i) {
1397             if (index != i) {
1398                 if (index != -1)  return false;
1399                 index = (short)i;
1400             }
1401             return true;
1402         }
1403         char typeChar() {
1404             return type.btChar;
1405         }
1406 
1407         void resolve() {
1408             if (function != null)
1409                 function.resolve();
1410         }
1411 
1412         Name newIndex(int i) {
1413             if (initIndex(i))  return this;
1414             return cloneWithIndex(i);
1415         }
1416         Name cloneWithIndex(int i) {
1417             Object[] newArguments = (arguments == null) ? null : arguments.clone();
1418             return new Name(i, type, function, newArguments).withConstraint(constraint);
1419         }
1420         Name withConstraint(Object constraint) {
1421             if (constraint == this.constraint)  return this;
1422             return new Name(this, constraint);
1423         }
1424         Name replaceName(Name oldName, Name newName) {  // FIXME: use replaceNames uniformly
1425             if (oldName == newName)  return this;
1426             @SuppressWarnings("LocalVariableHidesMemberVariable")
1427             Object[] arguments = this.arguments;
1428             if (arguments == null)  return this;
1429             boolean replaced = false;
1430             for (int j = 0; j < arguments.length; j++) {
1431                 if (arguments[j] == oldName) {
1432                     if (!replaced) {
1433                         replaced = true;
1434                         arguments = arguments.clone();
1435                     }
1436                     arguments[j] = newName;
1437                 }
1438             }
1439             if (!replaced)  return this;
1440             return new Name(function, arguments);
1441         }
1442         /** In the arguments of this Name, replace oldNames[i] pairwise by newNames[i].
1443          *  Limit such replacements to {@code start<=i<end}.  Return possibly changed self.
1444          */
1445         Name replaceNames(Name[] oldNames, Name[] newNames, int start, int end) {
1446             if (start >= end)  return this;
1447             @SuppressWarnings("LocalVariableHidesMemberVariable")
1448             Object[] arguments = this.arguments;
1449             boolean replaced = false;
1450         eachArg:
1451             for (int j = 0; j < arguments.length; j++) {
1452                 if (arguments[j] instanceof Name) {
1453                     Name n = (Name) arguments[j];
1454                     int check = n.index;
1455                     // harmless check to see if the thing is already in newNames:
1456                     if (check >= 0 && check < newNames.length && n == newNames[check])
1457                         continue eachArg;
1458                     // n might not have the correct index: n != oldNames[n.index].
1459                     for (int i = start; i < end; i++) {
1460                         if (n == oldNames[i]) {
1461                             if (n == newNames[i])
1462                                 continue eachArg;
1463                             if (!replaced) {
1464                                 replaced = true;
1465                                 arguments = arguments.clone();
1466                             }
1467                             arguments[j] = newNames[i];
1468                             continue eachArg;
1469                         }
1470                     }
1471                 }
1472             }
1473             if (!replaced)  return this;
1474             return new Name(function, arguments);
1475         }
1476         void internArguments() {
1477             @SuppressWarnings("LocalVariableHidesMemberVariable")
1478             Object[] arguments = this.arguments;
1479             for (int j = 0; j < arguments.length; j++) {
1480                 if (arguments[j] instanceof Name) {
1481                     Name n = (Name) arguments[j];
1482                     if (n.isParam() && n.index < INTERNED_ARGUMENT_LIMIT)
1483                         arguments[j] = internArgument(n);
1484                 }
1485             }
1486         }
1487         boolean isParam() {
1488             return function == null;
1489         }
1490         boolean isConstantZero() {
1491             return !isParam() && arguments.length == 0 && function.isConstantZero();
1492         }
1493 
1494         public String toString() {
1495             return (isParam()?"a":"t")+(index >= 0 ? index : System.identityHashCode(this))+":"+typeChar();
1496         }
1497         public String debugString() {
1498             String s = paramString();
1499             return (function == null) ? s : s + "=" + exprString();
1500         }
1501         public String paramString() {
1502             String s = toString();
1503             Object c = constraint;
1504             if (c == null)
1505                 return s;
1506             if (c instanceof Class)  c = ((Class<?>)c).getSimpleName();
1507             return s + "/" + c;
1508         }
1509         public String exprString() {
1510             if (function == null)  return toString();
1511             StringBuilder buf = new StringBuilder(function.toString());
1512             buf.append("(");
1513             String cma = "";
1514             for (Object a : arguments) {
1515                 buf.append(cma); cma = ",";
1516                 if (a instanceof Name || a instanceof Integer)
1517                     buf.append(a);
1518                 else
1519                     buf.append("(").append(a).append(")");
1520             }
1521             buf.append(")");
1522             return buf.toString();
1523         }
1524 
1525         static boolean typesMatch(BasicType parameterType, Object object) {
1526             if (object instanceof Name) {
1527                 return ((Name)object).type == parameterType;
1528             }
1529             switch (parameterType) {
1530                 case I_TYPE:  return object instanceof Integer;
1531                 case J_TYPE:  return object instanceof Long;
1532                 case F_TYPE:  return object instanceof Float;
1533                 case D_TYPE:  return object instanceof Double;
1534             }
1535             assert(parameterType == L_TYPE);
1536             return true;
1537         }
1538 
1539         /** Return the index of the last occurrence of n in the argument array.
1540          *  Return -1 if the name is not used.
1541          */
1542         int lastUseIndex(Name n) {
1543             if (arguments == null)  return -1;
1544             for (int i = arguments.length; --i >= 0; ) {
1545                 if (arguments[i] == n)  return i;
1546             }
1547             return -1;
1548         }
1549 
1550         /** Return the number of occurrences of n in the argument array.
1551          *  Return 0 if the name is not used.
1552          */
1553         int useCount(Name n) {
1554             if (arguments == null)  return 0;
1555             int count = 0;
1556             for (int i = arguments.length; --i >= 0; ) {
1557                 if (arguments[i] == n)  ++count;
1558             }
1559             return count;
1560         }
1561 
1562         boolean contains(Name n) {
1563             return this == n || lastUseIndex(n) >= 0;
1564         }
1565 
1566         public boolean equals(Name that) {
1567             if (this == that)  return true;
1568             if (isParam())
1569                 // each parameter is a unique atom
1570                 return false;  // this != that
1571             return
1572                 //this.index == that.index &&
1573                 this.type == that.type &&
1574                 this.function.equals(that.function) &&
1575                 Arrays.equals(this.arguments, that.arguments);
1576         }
1577         @Override
1578         public boolean equals(Object x) {
1579             return x instanceof Name && equals((Name)x);
1580         }
1581         @Override
1582         public int hashCode() {
1583             if (isParam())
1584                 return index | (type.ordinal() << 8);
1585             return function.hashCode() ^ Arrays.hashCode(arguments);
1586         }
1587     }
1588 
1589     /** Return the index of the last name which contains n as an argument.
1590      *  Return -1 if the name is not used.  Return names.length if it is the return value.
1591      */
1592     int lastUseIndex(Name n) {
1593         int ni = n.index, nmax = names.length;
1594         assert(names[ni] == n);
1595         if (result == ni)  return nmax;  // live all the way beyond the end
1596         for (int i = nmax; --i > ni; ) {
1597             if (names[i].lastUseIndex(n) >= 0)
1598                 return i;
1599         }
1600         return -1;
1601     }
1602 
1603     /** Return the number of times n is used as an argument or return value. */
1604     int useCount(Name n) {
1605         int ni = n.index, nmax = names.length;
1606         int end = lastUseIndex(n);
1607         if (end < 0)  return 0;
1608         int count = 0;
1609         if (end == nmax) { count++; end--; }
1610         int beg = n.index() + 1;
1611         if (beg < arity)  beg = arity;
1612         for (int i = beg; i <= end; i++) {
1613             count += names[i].useCount(n);
1614         }
1615         return count;
1616     }
1617 
1618     static Name argument(int which, char type) {
1619         return argument(which, basicType(type));
1620     }
1621     static Name argument(int which, BasicType type) {
1622         if (which >= INTERNED_ARGUMENT_LIMIT)
1623             return new Name(which, type);
1624         return INTERNED_ARGUMENTS[type.ordinal()][which];
1625     }
1626     static Name internArgument(Name n) {
1627         assert(n.isParam()) : "not param: " + n;
1628         assert(n.index < INTERNED_ARGUMENT_LIMIT);
1629         if (n.constraint != null)  return n;
1630         return argument(n.index, n.type);
1631     }
1632     static Name[] arguments(int extra, String types) {
1633         int length = types.length();
1634         Name[] names = new Name[length + extra];
1635         for (int i = 0; i < length; i++)
1636             names[i] = argument(i, types.charAt(i));
1637         return names;
1638     }
1639     static Name[] arguments(int extra, char... types) {
1640         int length = types.length;
1641         Name[] names = new Name[length + extra];
1642         for (int i = 0; i < length; i++)
1643             names[i] = argument(i, types[i]);
1644         return names;
1645     }
1646     static Name[] arguments(int extra, List<Class<?>> types) {
1647         int length = types.size();
1648         Name[] names = new Name[length + extra];
1649         for (int i = 0; i < length; i++)
1650             names[i] = argument(i, basicType(types.get(i)));
1651         return names;
1652     }
1653     static Name[] arguments(int extra, Class<?>... types) {
1654         int length = types.length;
1655         Name[] names = new Name[length + extra];
1656         for (int i = 0; i < length; i++)
1657             names[i] = argument(i, basicType(types[i]));
1658         return names;
1659     }
1660     static Name[] arguments(int extra, MethodType types) {
1661         int length = types.parameterCount();
1662         Name[] names = new Name[length + extra];
1663         for (int i = 0; i < length; i++)
1664             names[i] = argument(i, basicType(types.parameterType(i)));
1665         return names;
1666     }
1667     static final int INTERNED_ARGUMENT_LIMIT = 10;
1668     private static final Name[][] INTERNED_ARGUMENTS
1669             = new Name[ARG_TYPE_LIMIT][INTERNED_ARGUMENT_LIMIT];
1670     static {
1671         for (BasicType type : BasicType.ARG_TYPES) {
1672             int ord = type.ordinal();
1673             for (int i = 0; i < INTERNED_ARGUMENTS[ord].length; i++) {
1674                 INTERNED_ARGUMENTS[ord][i] = new Name(i, type);
1675             }
1676         }
1677     }
1678 
1679     private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
1680 
1681     static LambdaForm identityForm(BasicType type) {
1682         return LF_identityForm[type.ordinal()];
1683     }
1684     static LambdaForm zeroForm(BasicType type) {
1685         return LF_zeroForm[type.ordinal()];
1686     }
1687     static NamedFunction identity(BasicType type) {
1688         return NF_identity[type.ordinal()];
1689     }
1690     static NamedFunction constantZero(BasicType type) {
1691         return NF_zero[type.ordinal()];
1692     }
1693     private static final LambdaForm[] LF_identityForm = new LambdaForm[TYPE_LIMIT];
1694     private static final LambdaForm[] LF_zeroForm = new LambdaForm[TYPE_LIMIT];
1695     private static final NamedFunction[] NF_identity = new NamedFunction[TYPE_LIMIT];
1696     private static final NamedFunction[] NF_zero = new NamedFunction[TYPE_LIMIT];
1697     private static void createIdentityForms() {
1698         for (BasicType type : BasicType.ALL_TYPES) {
1699             int ord = type.ordinal();
1700             char btChar = type.basicTypeChar();
1701             boolean isVoid = (type == V_TYPE);
1702             Class<?> btClass = type.btClass;
1703             MethodType zeType = MethodType.methodType(btClass);
1704             MethodType idType = isVoid ? zeType : zeType.appendParameterTypes(btClass);
1705 
1706             // Look up some symbolic names.  It might not be necessary to have these,
1707             // but if we need to emit direct references to bytecodes, it helps.
1708             // Zero is built from a call to an identity function with a constant zero input.
1709             MemberName idMem = new MemberName(LambdaForm.class, "identity_"+btChar, idType, REF_invokeStatic);
1710             MemberName zeMem = new MemberName(LambdaForm.class, "zero_"+btChar, zeType, REF_invokeStatic);
1711             try {
1712                 zeMem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, zeMem, null, NoSuchMethodException.class);
1713                 idMem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, idMem, null, NoSuchMethodException.class);
1714             } catch (IllegalAccessException|NoSuchMethodException ex) {
1715                 throw newInternalError(ex);
1716             }
1717 
1718             NamedFunction idFun = new NamedFunction(idMem);
1719             LambdaForm idForm;
1720             if (isVoid) {
1721                 Name[] idNames = new Name[] { argument(0, L_TYPE) };
1722                 idForm = new LambdaForm(idMem.getName(), 1, idNames, VOID_RESULT);
1723             } else {
1724                 Name[] idNames = new Name[] { argument(0, L_TYPE), argument(1, type) };
1725                 idForm = new LambdaForm(idMem.getName(), 2, idNames, 1);
1726             }
1727             LF_identityForm[ord] = idForm;
1728             NF_identity[ord] = idFun;
1729 
1730             NamedFunction zeFun = new NamedFunction(zeMem);
1731             LambdaForm zeForm;
1732             if (isVoid) {
1733                 zeForm = idForm;
1734             } else {
1735                 Object zeValue = Wrapper.forBasicType(btChar).zero();
1736                 Name[] zeNames = new Name[] { argument(0, L_TYPE), new Name(idFun, zeValue) };
1737                 zeForm = new LambdaForm(zeMem.getName(), 1, zeNames, 1);
1738             }
1739             LF_zeroForm[ord] = zeForm;
1740             NF_zero[ord] = zeFun;
1741 
1742             assert(idFun.isIdentity());
1743             assert(zeFun.isConstantZero());
1744             assert(new Name(zeFun).isConstantZero());
1745         }
1746 
1747         // Do this in a separate pass, so that SimpleMethodHandle.make can see the tables.
1748         for (BasicType type : BasicType.ALL_TYPES) {
1749             int ord = type.ordinal();
1750             NamedFunction idFun = NF_identity[ord];
1751             LambdaForm idForm = LF_identityForm[ord];
1752             MemberName idMem = idFun.member;
1753             idFun.resolvedHandle = SimpleMethodHandle.make(idMem.getInvocationType(), idForm);
1754 
1755             NamedFunction zeFun = NF_zero[ord];
1756             LambdaForm zeForm = LF_zeroForm[ord];
1757             MemberName zeMem = zeFun.member;
1758             zeFun.resolvedHandle = SimpleMethodHandle.make(zeMem.getInvocationType(), zeForm);
1759 
1760             assert(idFun.isIdentity());
1761             assert(zeFun.isConstantZero());
1762             assert(new Name(zeFun).isConstantZero());
1763         }
1764     }
1765 
1766     // Avoid appealing to ValueConversions at bootstrap time:
1767     private static int identity_I(int x) { return x; }
1768     private static long identity_J(long x) { return x; }
1769     private static float identity_F(float x) { return x; }
1770     private static double identity_D(double x) { return x; }
1771     private static Object identity_L(Object x) { return x; }
1772     private static void identity_V() { return; }  // same as zeroV, but that's OK
1773     private static int zero_I() { return 0; }
1774     private static long zero_J() { return 0; }
1775     private static float zero_F() { return 0; }
1776     private static double zero_D() { return 0; }
1777     private static Object zero_L() { return null; }
1778     private static void zero_V() { return; }
1779 
1780     /**
1781      * Internal marker for byte-compiled LambdaForms.
1782      */
1783     /*non-public*/
1784     @Target(ElementType.METHOD)
1785     @Retention(RetentionPolicy.RUNTIME)
1786     @interface Compiled {
1787     }
1788 
1789     /**
1790      * Internal marker for LambdaForm interpreter frames.
1791      */
1792     /*non-public*/
1793     @Target(ElementType.METHOD)
1794     @Retention(RetentionPolicy.RUNTIME)
1795     @interface Hidden {
1796     }
1797 
1798     private static final HashMap<String,Integer> DEBUG_NAME_COUNTERS;
1799     static {
1800         if (debugEnabled())
1801             DEBUG_NAME_COUNTERS = new HashMap<>();
1802         else
1803             DEBUG_NAME_COUNTERS = null;
1804     }
1805 
1806     // Put this last, so that previous static inits can run before.
1807     static {
1808         createIdentityForms();
1809         if (USE_PREDEFINED_INTERPRET_METHODS)
1810             computeInitialPreparedForms();
1811         NamedFunction.initializeInvokers();
1812     }
1813 
1814     // The following hack is necessary in order to suppress TRACE_INTERPRETER
1815     // during execution of the static initializes of this class.
1816     // Turning on TRACE_INTERPRETER too early will cause
1817     // stack overflows and other misbehavior during attempts to trace events
1818     // that occur during LambdaForm.<clinit>.
1819     // Therefore, do not move this line higher in this file, and do not remove.
1820     private static final boolean TRACE_INTERPRETER = MethodHandleStatics.TRACE_INTERPRETER;
1821 }