1 /*
2 * Copyright (c) 2011, 2017, 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 jdk.internal.perf.PerfCounter;
29 import jdk.internal.vm.annotation.DontInline;
30 import jdk.internal.vm.annotation.Stable;
31 import sun.invoke.util.Wrapper;
32
33 import java.lang.annotation.ElementType;
34 import java.lang.annotation.Retention;
35 import java.lang.annotation.RetentionPolicy;
36 import java.lang.annotation.Target;
37 import java.lang.reflect.Method;
38 import java.util.Arrays;
39 import java.util.HashMap;
40
41 import static java.lang.invoke.LambdaForm.BasicType.*;
42 import static java.lang.invoke.MethodHandleNatives.Constants.REF_invokeStatic;
43 import static java.lang.invoke.MethodHandleStatics.*;
44
45 /**
46 * The symbolic, non-executable form of a method handle's invocation semantics.
47 * It consists of a series of names.
48 * The first N (N=arity) names are parameters,
49 * while any remaining names are temporary values.
50 * Each temporary specifies the application of a function to some arguments.
51 * The functions are method handles, while the arguments are mixes of
52 * constant values and local names.
53 * The result of the lambda is defined as one of the names, often the last one.
54 * <p>
55 * Here is an approximate grammar:
56 * <blockquote><pre>{@code
57 * LambdaForm = "(" ArgName* ")=>{" TempName* Result "}"
58 * ArgName = "a" N ":" T
59 * TempName = "t" N ":" T "=" Function "(" Argument* ");"
60 * Function = ConstantValue
61 * Argument = NameRef | ConstantValue
62 * Result = NameRef | "void"
63 * NameRef = "a" N | "t" N
64 * N = (any whole number)
65 * T = "L" | "I" | "J" | "F" | "D" | "V"
66 * }</pre></blockquote>
67 * Names are numbered consecutively from left to right starting at zero.
68 * (The letters are merely a taste of syntax sugar.)
69 * Thus, the first temporary (if any) is always numbered N (where N=arity).
70 * Every occurrence of a name reference in an argument list must refer to
71 * a name previously defined within the same lambda.
72 * A lambda has a void result if and only if its result index is -1.
73 * If a temporary has the type "V", it cannot be the subject of a NameRef,
74 * even though possesses a number.
75 * Note that all reference types are erased to "L", which stands for {@code Object}.
76 * All subword types (boolean, byte, short, char) are erased to "I" which is {@code int}.
77 * The other types stand for the usual primitive types.
78 * <p>
79 * Function invocation closely follows the static rules of the Java verifier.
80 * Arguments and return values must exactly match when their "Name" types are
81 * considered.
82 * Conversions are allowed only if they do not change the erased type.
83 * <ul>
84 * <li>L = Object: casts are used freely to convert into and out of reference types
85 * <li>I = int: subword types are forcibly narrowed when passed as arguments (see {@code explicitCastArguments})
86 * <li>J = long: no implicit conversions
87 * <li>F = float: no implicit conversions
88 * <li>D = double: no implicit conversions
89 * <li>V = void: a function result may be void if and only if its Name is of type "V"
90 * </ul>
91 * Although implicit conversions are not allowed, explicit ones can easily be
92 * encoded by using temporary expressions which call type-transformed identity functions.
93 * <p>
94 * Examples:
95 * <blockquote><pre>{@code
96 * (a0:J)=>{ a0 }
97 * == identity(long)
98 * (a0:I)=>{ t1:V = System.out#println(a0); void }
99 * == System.out#println(int)
100 * (a0:L)=>{ t1:V = System.out#println(a0); a0 }
101 * == identity, with printing side-effect
102 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
103 * t3:L = BoundMethodHandle#target(a0);
104 * t4:L = MethodHandle#invoke(t3, t2, a1); t4 }
105 * == general invoker for unary insertArgument combination
106 * (a0:L, a1:L)=>{ t2:L = FilterMethodHandle#filter(a0);
107 * t3:L = MethodHandle#invoke(t2, a1);
108 * t4:L = FilterMethodHandle#target(a0);
109 * t5:L = MethodHandle#invoke(t4, t3); t5 }
110 * == general invoker for unary filterArgument combination
111 * (a0:L, a1:L)=>{ ...(same as previous example)...
112 * t5:L = MethodHandle#invoke(t4, t3, a1); t5 }
113 * == general invoker for unary/unary foldArgument combination
114 * (a0:L, a1:I)=>{ t2:I = identity(long).asType((int)->long)(a1); t2 }
115 * == invoker for identity method handle which performs i2l
116 * (a0:L, a1:L)=>{ t2:L = BoundMethodHandle#argument(a0);
117 * t3:L = Class#cast(t2,a1); t3 }
118 * == invoker for identity method handle which performs cast
119 * }</pre></blockquote>
120 * <p>
121 * @author John Rose, JSR 292 EG
122 */
123 class LambdaForm {
124 final int arity;
125 final int result;
126 final boolean forceInline;
127 final MethodHandle customized;
128 @Stable final Name[] names;
129 final Kind kind;
130 MemberName vmentry; // low-level behavior, or null if not yet prepared
131 private boolean isCompiled;
132
133 // Either a LambdaForm cache (managed by LambdaFormEditor) or a link to uncustomized version (for customized LF)
134 volatile Object transformCache;
135
136 public static final int VOID_RESULT = -1, LAST_RESULT = -2;
137
138 enum BasicType {
139 L_TYPE('L', Object.class, Wrapper.OBJECT), // all reference types
140 I_TYPE('I', int.class, Wrapper.INT),
141 J_TYPE('J', long.class, Wrapper.LONG),
142 F_TYPE('F', float.class, Wrapper.FLOAT),
143 D_TYPE('D', double.class, Wrapper.DOUBLE), // all primitive types
144 V_TYPE('V', void.class, Wrapper.VOID); // not valid in all contexts
145
146 static final BasicType[] ALL_TYPES = BasicType.values();
147 static final BasicType[] ARG_TYPES = Arrays.copyOf(ALL_TYPES, ALL_TYPES.length-1);
148
149 static final int ARG_TYPE_LIMIT = ARG_TYPES.length;
150 static final int TYPE_LIMIT = ALL_TYPES.length;
151
152 final char btChar;
153 final Class<?> btClass;
154 final Wrapper btWrapper;
155
156 private BasicType(char btChar, Class<?> btClass, Wrapper wrapper) {
157 this.btChar = btChar;
158 this.btClass = btClass;
159 this.btWrapper = wrapper;
160 }
161
162 char basicTypeChar() {
163 return btChar;
164 }
165 Class<?> basicTypeClass() {
166 return btClass;
167 }
168 Wrapper basicTypeWrapper() {
169 return btWrapper;
170 }
171 int basicTypeSlots() {
172 return btWrapper.stackSlots();
173 }
174
175 static BasicType basicType(byte type) {
176 return ALL_TYPES[type];
177 }
178 static BasicType basicType(char type) {
179 switch (type) {
180 case 'L': return L_TYPE;
181 case 'I': return I_TYPE;
182 case 'J': return J_TYPE;
183 case 'F': return F_TYPE;
184 case 'D': return D_TYPE;
185 case 'V': return V_TYPE;
186 // all subword types are represented as ints
187 case 'Z':
188 case 'B':
189 case 'S':
190 case 'C':
191 return I_TYPE;
192 default:
193 throw newInternalError("Unknown type char: '"+type+"'");
194 }
195 }
196 static BasicType basicType(Wrapper type) {
197 char c = type.basicTypeChar();
198 return basicType(c);
199 }
200 static BasicType basicType(Class<?> type) {
201 if (!type.isPrimitive()) return L_TYPE;
202 return basicType(Wrapper.forPrimitiveType(type));
203 }
204 static BasicType[] basicTypes(String types) {
205 BasicType[] btypes = new BasicType[types.length()];
206 for (int i = 0; i < btypes.length; i++) {
207 btypes[i] = basicType(types.charAt(i));
208 }
209 return btypes;
210 }
211 static String basicTypeDesc(BasicType[] types) {
212 if (types == null) {
213 return null;
214 }
215 if (types.length == 0) {
216 return "";
217 }
218 StringBuilder sb = new StringBuilder();
219 for (BasicType bt : types) {
220 sb.append(bt.basicTypeChar());
221 }
222 return sb.toString();
223 }
224 static int[] basicTypeOrds(BasicType[] types) {
225 if (types == null) {
226 return null;
227 }
228 int[] a = new int[types.length];
229 for(int i = 0; i < types.length; ++i) {
230 a[i] = types[i].ordinal();
231 }
232 return a;
233 }
234
235 static char basicTypeChar(Class<?> type) {
236 return basicType(type).btChar;
237 }
238
239 static byte[] basicTypesOrd(Class<?>[] types) {
240 byte[] ords = new byte[types.length];
241 for (int i = 0; i < ords.length; i++) {
242 ords[i] = (byte)basicType(types[i]).ordinal();
243 }
244 return ords;
245 }
246
247 static boolean isBasicTypeChar(char c) {
248 return "LIJFDV".indexOf(c) >= 0;
249 }
250 static boolean isArgBasicTypeChar(char c) {
251 return "LIJFD".indexOf(c) >= 0;
252 }
253
254 static { assert(checkBasicType()); }
255 private static boolean checkBasicType() {
256 for (int i = 0; i < ARG_TYPE_LIMIT; i++) {
257 assert ARG_TYPES[i].ordinal() == i;
258 assert ARG_TYPES[i] == ALL_TYPES[i];
259 }
260 for (int i = 0; i < TYPE_LIMIT; i++) {
261 assert ALL_TYPES[i].ordinal() == i;
262 }
263 assert ALL_TYPES[TYPE_LIMIT - 1] == V_TYPE;
264 assert !Arrays.asList(ARG_TYPES).contains(V_TYPE);
265 return true;
266 }
267 }
268
269 enum Kind {
270 GENERIC("invoke"),
271 ZERO("zero"),
272 IDENTITY("identity"),
273 BOUND_REINVOKER("BMH.reinvoke", "reinvoke"),
274 REINVOKER("MH.reinvoke", "reinvoke"),
275 DELEGATE("MH.delegate", "delegate"),
276 EXACT_LINKER("MH.invokeExact_MT", "invokeExact_MT"),
277 EXACT_INVOKER("MH.exactInvoker", "exactInvoker"),
278 GENERIC_LINKER("MH.invoke_MT", "invoke_MT"),
279 GENERIC_INVOKER("MH.invoker", "invoker"),
280 LINK_TO_TARGET_METHOD("linkToTargetMethod"),
281 LINK_TO_CALL_SITE("linkToCallSite"),
282 DIRECT_INVOKE_VIRTUAL("DMH.invokeVirtual", "invokeVirtual"),
283 DIRECT_INVOKE_SPECIAL("DMH.invokeSpecial", "invokeSpecial"),
284 DIRECT_INVOKE_STATIC("DMH.invokeStatic", "invokeStatic"),
285 DIRECT_NEW_INVOKE_SPECIAL("DMH.newInvokeSpecial", "newInvokeSpecial"),
286 DIRECT_INVOKE_INTERFACE("DMH.invokeInterface", "invokeInterface"),
287 DIRECT_INVOKE_STATIC_INIT("DMH.invokeStaticInit", "invokeStaticInit"),
288 GET_OBJECT("getObject"),
289 PUT_OBJECT("putObject"),
290 GET_OBJECT_VOLATILE("getObjectVolatile"),
291 PUT_OBJECT_VOLATILE("putObjectVolatile"),
292 GET_INT("getInt"),
293 PUT_INT("putInt"),
294 GET_INT_VOLATILE("getIntVolatile"),
295 PUT_INT_VOLATILE("putIntVolatile"),
296 GET_BOOLEAN("getBoolean"),
297 PUT_BOOLEAN("putBoolean"),
298 GET_BOOLEAN_VOLATILE("getBooleanVolatile"),
299 PUT_BOOLEAN_VOLATILE("putBooleanVolatile"),
300 GET_BYTE("getByte"),
301 PUT_BYTE("putByte"),
302 GET_BYTE_VOLATILE("getByteVolatile"),
303 PUT_BYTE_VOLATILE("putByteVolatile"),
304 GET_CHAR("getChar"),
305 PUT_CHAR("putChar"),
306 GET_CHAR_VOLATILE("getCharVolatile"),
307 PUT_CHAR_VOLATILE("putCharVolatile"),
308 GET_SHORT("getShort"),
309 PUT_SHORT("putShort"),
310 GET_SHORT_VOLATILE("getShortVolatile"),
311 PUT_SHORT_VOLATILE("putShortVolatile"),
312 GET_LONG("getLong"),
313 PUT_LONG("putLong"),
314 GET_LONG_VOLATILE("getLongVolatile"),
315 PUT_LONG_VOLATILE("putLongVolatile"),
316 GET_FLOAT("getFloat"),
317 PUT_FLOAT("putFloat"),
318 GET_FLOAT_VOLATILE("getFloatVolatile"),
319 PUT_FLOAT_VOLATILE("putFloatVolatile"),
320 GET_DOUBLE("getDouble"),
321 PUT_DOUBLE("putDouble"),
322 GET_DOUBLE_VOLATILE("getDoubleVolatile"),
323 PUT_DOUBLE_VOLATILE("putDoubleVolatile"),
324 TRY_FINALLY("tryFinally"),
325 COLLECT("collect"),
326 CONVERT("convert"),
327 SPREAD("spread"),
328 LOOP("loop"),
329 FIELD("field"),
330 GUARD("guard"),
331 GUARD_WITH_CATCH("guardWithCatch"),
332 VARHANDLE_EXACT_INVOKER("VH.exactInvoker"),
333 VARHANDLE_INVOKER("VH.invoker", "invoker"),
334 VARHANDLE_LINKER("VH.invoke_MT", "invoke_MT");
335
336 final String defaultLambdaName;
337 final String methodName;
338
339 private Kind(String defaultLambdaName) {
340 this(defaultLambdaName, defaultLambdaName);
341 }
342
343 private Kind(String defaultLambdaName, String methodName) {
344 this.defaultLambdaName = defaultLambdaName;
345 this.methodName = methodName;
346 }
347 }
348
349 LambdaForm(int arity, Name[] names, int result) {
350 this(arity, names, result, /*forceInline=*/true, /*customized=*/null, Kind.GENERIC);
351 }
352 LambdaForm(int arity, Name[] names, int result, Kind kind) {
353 this(arity, names, result, /*forceInline=*/true, /*customized=*/null, kind);
354 }
355 LambdaForm(int arity, Name[] names, int result, boolean forceInline, MethodHandle customized) {
356 this(arity, names, result, forceInline, customized, Kind.GENERIC);
357 }
358 LambdaForm(int arity, Name[] names, int result, boolean forceInline, MethodHandle customized, Kind kind) {
359 assert(namesOK(arity, names));
360 this.arity = arity;
361 this.result = fixResult(result, names);
362 this.names = names.clone();
363 this.forceInline = forceInline;
364 this.customized = customized;
365 this.kind = kind;
366 int maxOutArity = normalize();
367 if (maxOutArity > MethodType.MAX_MH_INVOKER_ARITY) {
368 // Cannot use LF interpreter on very high arity expressions.
369 assert(maxOutArity <= MethodType.MAX_JVM_ARITY);
370 compileToBytecode();
371 }
372 }
373 LambdaForm(int arity, Name[] names) {
374 this(arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null, Kind.GENERIC);
375 }
376 LambdaForm(int arity, Name[] names, Kind kind) {
377 this(arity, names, LAST_RESULT, /*forceInline=*/true, /*customized=*/null, kind);
378 }
379 LambdaForm(int arity, Name[] names, boolean forceInline) {
380 this(arity, names, LAST_RESULT, forceInline, /*customized=*/null, Kind.GENERIC);
381 }
382 LambdaForm(int arity, Name[] names, boolean forceInline, Kind kind) {
383 this(arity, names, LAST_RESULT, forceInline, /*customized=*/null, kind);
384 }
385 LambdaForm(Name[] formals, Name[] temps, Name result) {
386 this(formals.length, buildNames(formals, temps, result), LAST_RESULT, /*forceInline=*/true, /*customized=*/null);
387 }
388 LambdaForm(Name[] formals, Name[] temps, Name result, boolean forceInline) {
389 this(formals.length, buildNames(formals, temps, result), LAST_RESULT, forceInline, /*customized=*/null);
390 }
391
392 private static Name[] buildNames(Name[] formals, Name[] temps, Name result) {
393 int arity = formals.length;
394 int length = arity + temps.length + (result == null ? 0 : 1);
395 Name[] names = Arrays.copyOf(formals, length);
396 System.arraycopy(temps, 0, names, arity, temps.length);
397 if (result != null)
398 names[length - 1] = result;
399 return names;
400 }
401
402 private LambdaForm(MethodType mt) {
403 // Make a blank lambda form, which returns a constant zero or null.
404 // It is used as a template for managing the invocation of similar forms that are non-empty.
405 // Called only from getPreparedForm.
406 this.arity = mt.parameterCount();
407 this.result = (mt.returnType() == void.class || mt.returnType() == Void.class) ? -1 : arity;
408 this.names = buildEmptyNames(arity, mt, result == -1);
409 this.forceInline = true;
410 this.customized = null;
411 this.kind = Kind.ZERO;
412 assert(nameRefsAreLegal());
413 assert(isEmpty());
414 String sig = null;
415 assert(isValidSignature(sig = basicTypeSignature()));
416 assert(sig.equals(basicTypeSignature())) : sig + " != " + basicTypeSignature();
417 }
418
419 private static Name[] buildEmptyNames(int arity, MethodType mt, boolean isVoid) {
420 Name[] names = arguments(isVoid ? 0 : 1, mt);
421 if (!isVoid) {
422 Name zero = new Name(constantZero(basicType(mt.returnType())));
423 names[arity] = zero.newIndex(arity);
424 }
425 return names;
426 }
427
428 private static int fixResult(int result, Name[] names) {
429 if (result == LAST_RESULT)
430 result = names.length - 1; // might still be void
431 if (result >= 0 && names[result].type == V_TYPE)
432 result = VOID_RESULT;
433 return result;
434 }
435
436 static boolean debugNames() {
437 return DEBUG_NAME_COUNTERS != null;
438 }
439
440 static void associateWithDebugName(LambdaForm form, String name) {
441 assert (debugNames());
442 synchronized (DEBUG_NAMES) {
443 DEBUG_NAMES.put(form, name);
444 }
445 }
446
447 String lambdaName() {
448 if (DEBUG_NAMES != null) {
449 synchronized (DEBUG_NAMES) {
450 String name = DEBUG_NAMES.get(this);
451 if (name == null) {
452 name = generateDebugName();
453 }
454 return name;
455 }
456 }
457 return kind.defaultLambdaName;
458 }
459
460 private String generateDebugName() {
461 assert (debugNames());
462 String debugNameStem = kind.defaultLambdaName;
463 Integer ctr = DEBUG_NAME_COUNTERS.getOrDefault(debugNameStem, 0);
464 DEBUG_NAME_COUNTERS.put(debugNameStem, ctr + 1);
465 StringBuilder buf = new StringBuilder(debugNameStem);
466 int leadingZero = buf.length();
467 buf.append((int) ctr);
468 for (int i = buf.length() - leadingZero; i < 3; i++) {
469 buf.insert(leadingZero, '0');
470 }
471 buf.append('_');
472 buf.append(basicTypeSignature());
473 String name = buf.toString();
474 associateWithDebugName(this, name);
475 return name;
476 }
477
478 private static boolean namesOK(int arity, Name[] names) {
479 for (int i = 0; i < names.length; i++) {
480 Name n = names[i];
481 assert(n != null) : "n is null";
482 if (i < arity)
483 assert( n.isParam()) : n + " is not param at " + i;
484 else
485 assert(!n.isParam()) : n + " is param at " + i;
486 }
487 return true;
488 }
489
490 /** Customize LambdaForm for a particular MethodHandle */
491 LambdaForm customize(MethodHandle mh) {
492 LambdaForm customForm = new LambdaForm(arity, names, result, forceInline, mh, kind);
493 if (COMPILE_THRESHOLD >= 0 && isCompiled) {
494 // If shared LambdaForm has been compiled, compile customized version as well.
495 customForm.compileToBytecode();
496 }
497 customForm.transformCache = this; // LambdaFormEditor should always use uncustomized form.
498 return customForm;
499 }
500
501 /** Get uncustomized flavor of the LambdaForm */
502 LambdaForm uncustomize() {
503 if (customized == null) {
504 return this;
505 }
506 assert(transformCache != null); // Customized LambdaForm should always has a link to uncustomized version.
507 LambdaForm uncustomizedForm = (LambdaForm)transformCache;
508 if (COMPILE_THRESHOLD >= 0 && isCompiled) {
509 // If customized LambdaForm has been compiled, compile uncustomized version as well.
510 uncustomizedForm.compileToBytecode();
511 }
512 return uncustomizedForm;
513 }
514
515 /** Renumber and/or replace params so that they are interned and canonically numbered.
516 * @return maximum argument list length among the names (since we have to pass over them anyway)
517 */
518 private int normalize() {
519 Name[] oldNames = null;
520 int maxOutArity = 0;
521 int changesStart = 0;
522 for (int i = 0; i < names.length; i++) {
523 Name n = names[i];
524 if (!n.initIndex(i)) {
525 if (oldNames == null) {
526 oldNames = names.clone();
527 changesStart = i;
528 }
529 names[i] = n.cloneWithIndex(i);
530 }
531 if (n.arguments != null && maxOutArity < n.arguments.length)
532 maxOutArity = n.arguments.length;
533 }
534 if (oldNames != null) {
535 int startFixing = arity;
536 if (startFixing <= changesStart)
537 startFixing = changesStart+1;
538 for (int i = startFixing; i < names.length; i++) {
539 Name fixed = names[i].replaceNames(oldNames, names, changesStart, i);
540 names[i] = fixed.newIndex(i);
541 }
542 }
543 assert(nameRefsAreLegal());
544 int maxInterned = Math.min(arity, INTERNED_ARGUMENT_LIMIT);
545 boolean needIntern = false;
546 for (int i = 0; i < maxInterned; i++) {
547 Name n = names[i], n2 = internArgument(n);
548 if (n != n2) {
549 names[i] = n2;
550 needIntern = true;
551 }
552 }
553 if (needIntern) {
554 for (int i = arity; i < names.length; i++) {
555 names[i].internArguments();
556 }
557 }
558 assert(nameRefsAreLegal());
559 return maxOutArity;
560 }
561
562 /**
563 * Check that all embedded Name references are localizable to this lambda,
564 * and are properly ordered after their corresponding definitions.
565 * <p>
566 * Note that a Name can be local to multiple lambdas, as long as
567 * it possesses the same index in each use site.
568 * This allows Name references to be freely reused to construct
569 * fresh lambdas, without confusion.
570 */
571 boolean nameRefsAreLegal() {
572 assert(arity >= 0 && arity <= names.length);
573 assert(result >= -1 && result < names.length);
574 // Do all names possess an index consistent with their local definition order?
575 for (int i = 0; i < arity; i++) {
576 Name n = names[i];
577 assert(n.index() == i) : Arrays.asList(n.index(), i);
578 assert(n.isParam());
579 }
580 // Also, do all local name references
581 for (int i = arity; i < names.length; i++) {
582 Name n = names[i];
583 assert(n.index() == i);
584 for (Object arg : n.arguments) {
585 if (arg instanceof Name) {
586 Name n2 = (Name) arg;
587 int i2 = n2.index;
588 assert(0 <= i2 && i2 < names.length) : n.debugString() + ": 0 <= i2 && i2 < names.length: 0 <= " + i2 + " < " + names.length;
589 assert(names[i2] == n2) : Arrays.asList("-1-", i, "-2-", n.debugString(), "-3-", i2, "-4-", n2.debugString(), "-5-", names[i2].debugString(), "-6-", this);
590 assert(i2 < i); // ref must come after def!
591 }
592 }
593 }
594 return true;
595 }
596
597 /** Invoke this form on the given arguments. */
598 // final Object invoke(Object... args) throws Throwable {
599 // // NYI: fit this into the fast path?
600 // return interpretWithArguments(args);
601 // }
602
603 /** Report the return type. */
604 BasicType returnType() {
605 if (result < 0) return V_TYPE;
606 Name n = names[result];
607 return n.type;
608 }
609
610 /** Report the N-th argument type. */
611 BasicType parameterType(int n) {
612 return parameter(n).type;
613 }
614
615 /** Report the N-th argument name. */
616 Name parameter(int n) {
617 assert(n < arity);
618 Name param = names[n];
619 assert(param.isParam());
620 return param;
621 }
622
623 /** Report the N-th argument type constraint. */
624 Object parameterConstraint(int n) {
625 return parameter(n).constraint;
626 }
627
628 /** Report the arity. */
629 int arity() {
630 return arity;
631 }
632
633 /** Report the number of expressions (non-parameter names). */
634 int expressionCount() {
635 return names.length - arity;
636 }
637
638 /** Return the method type corresponding to my basic type signature. */
639 MethodType methodType() {
640 Class<?>[] ptypes = new Class<?>[arity];
641 for (int i = 0; i < arity; ++i) {
642 ptypes[i] = parameterType(i).btClass;
643 }
644 return MethodType.makeImpl(returnType().btClass, ptypes, true);
645 }
646
647 /** Return ABC_Z, where the ABC are parameter type characters, and Z is the return type character. */
648 final String basicTypeSignature() {
649 StringBuilder buf = new StringBuilder(arity() + 3);
650 for (int i = 0, a = arity(); i < a; i++)
651 buf.append(parameterType(i).basicTypeChar());
652 return buf.append('_').append(returnType().basicTypeChar()).toString();
653 }
654 static int signatureArity(String sig) {
655 assert(isValidSignature(sig));
656 return sig.indexOf('_');
657 }
658 static BasicType signatureReturn(String sig) {
659 return basicType(sig.charAt(signatureArity(sig) + 1));
660 }
661 static boolean isValidSignature(String sig) {
662 int arity = sig.indexOf('_');
663 if (arity < 0) return false; // must be of the form *_*
664 int siglen = sig.length();
665 if (siglen != arity + 2) return false; // *_X
666 for (int i = 0; i < siglen; i++) {
667 if (i == arity) continue; // skip '_'
668 char c = sig.charAt(i);
669 if (c == 'V')
670 return (i == siglen - 1 && arity == siglen - 2);
671 if (!isArgBasicTypeChar(c)) return false; // must be [LIJFD]
672 }
673 return true; // [LIJFD]*_[LIJFDV]
674 }
675 static MethodType signatureType(String sig) {
676 Class<?>[] ptypes = new Class<?>[signatureArity(sig)];
677 for (int i = 0; i < ptypes.length; i++)
678 ptypes[i] = basicType(sig.charAt(i)).btClass;
679 Class<?> rtype = signatureReturn(sig).btClass;
680 return MethodType.makeImpl(rtype, ptypes, true);
681 }
682
683 /**
684 * Check if i-th name is a call to MethodHandleImpl.selectAlternative.
685 */
686 boolean isSelectAlternative(int pos) {
687 // selectAlternative idiom:
688 // t_{n}:L=MethodHandleImpl.selectAlternative(...)
689 // t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)
690 if (pos+1 >= names.length) return false;
691 Name name0 = names[pos];
692 Name name1 = names[pos+1];
693 return name0.refersTo(MethodHandleImpl.class, "selectAlternative") &&
694 name1.isInvokeBasic() &&
695 name1.lastUseIndex(name0) == 0 && // t_{n+1}:?=MethodHandle.invokeBasic(t_{n}, ...)
696 lastUseIndex(name0) == pos+1; // t_{n} is local: used only in t_{n+1}
697 }
698
699 private boolean isMatchingIdiom(int pos, String idiomName, int nArgs) {
700 if (pos+2 >= names.length) return false;
701 Name name0 = names[pos];
702 Name name1 = names[pos+1];
703 Name name2 = names[pos+2];
704 return name1.refersTo(MethodHandleImpl.class, idiomName) &&
705 name0.isInvokeBasic() &&
706 name2.isInvokeBasic() &&
707 name1.lastUseIndex(name0) == nArgs && // t_{n+1}:L=MethodHandleImpl.<invoker>(<args>, t_{n});
708 lastUseIndex(name0) == pos+1 && // t_{n} is local: used only in t_{n+1}
709 name2.lastUseIndex(name1) == 1 && // t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})
710 lastUseIndex(name1) == pos+2; // t_{n+1} is local: used only in t_{n+2}
711 }
712
713 /**
714 * Check if i-th name is a start of GuardWithCatch idiom.
715 */
716 boolean isGuardWithCatch(int pos) {
717 // GuardWithCatch idiom:
718 // t_{n}:L=MethodHandle.invokeBasic(...)
719 // t_{n+1}:L=MethodHandleImpl.guardWithCatch(*, *, *, t_{n});
720 // t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})
721 return isMatchingIdiom(pos, "guardWithCatch", 3);
722 }
723
724 /**
725 * Check if i-th name is a start of the tryFinally idiom.
726 */
727 boolean isTryFinally(int pos) {
728 // tryFinally idiom:
729 // t_{n}:L=MethodHandle.invokeBasic(...)
730 // t_{n+1}:L=MethodHandleImpl.tryFinally(*, *, t_{n})
731 // t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})
732 return isMatchingIdiom(pos, "tryFinally", 2);
733 }
734
735 /**
736 * Check if i-th name is a start of the loop idiom.
737 */
738 boolean isLoop(int pos) {
739 // loop idiom:
740 // t_{n}:L=MethodHandle.invokeBasic(...)
741 // t_{n+1}:L=MethodHandleImpl.loop(types, *, t_{n})
742 // t_{n+2}:?=MethodHandle.invokeBasic(*, t_{n+1})
743 return isMatchingIdiom(pos, "loop", 2);
744 }
745
746 /*
747 * Code generation issues:
748 *
749 * Compiled LFs should be reusable in general.
750 * The biggest issue is how to decide when to pull a name into
751 * the bytecode, versus loading a reified form from the MH data.
752 *
753 * For example, an asType wrapper may require execution of a cast
754 * after a call to a MH. The target type of the cast can be placed
755 * as a constant in the LF itself. This will force the cast type
756 * to be compiled into the bytecodes and native code for the MH.
757 * Or, the target type of the cast can be erased in the LF, and
758 * loaded from the MH data. (Later on, if the MH as a whole is
759 * inlined, the data will flow into the inlined instance of the LF,
760 * as a constant, and the end result will be an optimal cast.)
761 *
762 * This erasure of cast types can be done with any use of
763 * reference types. It can also be done with whole method
764 * handles. Erasing a method handle might leave behind
765 * LF code that executes correctly for any MH of a given
766 * type, and load the required MH from the enclosing MH's data.
767 * Or, the erasure might even erase the expected MT.
768 *
769 * Also, for direct MHs, the MemberName of the target
770 * could be erased, and loaded from the containing direct MH.
771 * As a simple case, a LF for all int-valued non-static
772 * field getters would perform a cast on its input argument
773 * (to non-constant base type derived from the MemberName)
774 * and load an integer value from the input object
775 * (at a non-constant offset also derived from the MemberName).
776 * Such MN-erased LFs would be inlinable back to optimized
777 * code, whenever a constant enclosing DMH is available
778 * to supply a constant MN from its data.
779 *
780 * The main problem here is to keep LFs reasonably generic,
781 * while ensuring that hot spots will inline good instances.
782 * "Reasonably generic" means that we don't end up with
783 * repeated versions of bytecode or machine code that do
784 * not differ in their optimized form. Repeated versions
785 * of machine would have the undesirable overheads of
786 * (a) redundant compilation work and (b) extra I$ pressure.
787 * To control repeated versions, we need to be ready to
788 * erase details from LFs and move them into MH data,
789 * whevener those details are not relevant to significant
790 * optimization. "Significant" means optimization of
791 * code that is actually hot.
792 *
793 * Achieving this may require dynamic splitting of MHs, by replacing
794 * a generic LF with a more specialized one, on the same MH,
795 * if (a) the MH is frequently executed and (b) the MH cannot
796 * be inlined into a containing caller, such as an invokedynamic.
797 *
798 * Compiled LFs that are no longer used should be GC-able.
799 * If they contain non-BCP references, they should be properly
800 * interlinked with the class loader(s) that their embedded types
801 * depend on. This probably means that reusable compiled LFs
802 * will be tabulated (indexed) on relevant class loaders,
803 * or else that the tables that cache them will have weak links.
804 */
805
806 /**
807 * Make this LF directly executable, as part of a MethodHandle.
808 * Invariant: Every MH which is invoked must prepare its LF
809 * before invocation.
810 * (In principle, the JVM could do this very lazily,
811 * as a sort of pre-invocation linkage step.)
812 */
813 public void prepare() {
814 if (COMPILE_THRESHOLD == 0 && !forceInterpretation() && !isCompiled) {
815 compileToBytecode();
816 }
817 if (this.vmentry != null) {
818 // already prepared (e.g., a primitive DMH invoker form)
819 return;
820 }
821 MethodType mtype = methodType();
822 LambdaForm prep = mtype.form().cachedLambdaForm(MethodTypeForm.LF_INTERPRET);
823 if (prep == null) {
824 assert (isValidSignature(basicTypeSignature()));
825 prep = new LambdaForm(mtype);
826 prep.vmentry = InvokerBytecodeGenerator.generateLambdaFormInterpreterEntryPoint(mtype);
827 prep = mtype.form().setCachedLambdaForm(MethodTypeForm.LF_INTERPRET, prep);
828 }
829 this.vmentry = prep.vmentry;
830 // TO DO: Maybe add invokeGeneric, invokeWithArguments
831 }
832
833 private static @Stable PerfCounter LF_FAILED;
834
835 private static PerfCounter failedCompilationCounter() {
836 if (LF_FAILED == null) {
837 LF_FAILED = PerfCounter.newPerfCounter("java.lang.invoke.failedLambdaFormCompilations");
838 }
839 return LF_FAILED;
840 }
841
842 /** Generate optimizable bytecode for this form. */
843 void compileToBytecode() {
844 if (forceInterpretation()) {
845 return; // this should not be compiled
846 }
847 if (vmentry != null && isCompiled) {
848 return; // already compiled somehow
849 }
850
851 // Obtain the invoker MethodType outside of the following try block.
852 // This ensures that an IllegalArgumentException is directly thrown if the
853 // type would have 256 or more parameters
854 MethodType invokerType = methodType();
855 assert(vmentry == null || vmentry.getMethodType().basicType().equals(invokerType));
856 try {
857 vmentry = InvokerBytecodeGenerator.generateCustomizedCode(this, invokerType);
858 if (TRACE_INTERPRETER)
859 traceInterpreter("compileToBytecode", this);
860 isCompiled = true;
861 } catch (InvokerBytecodeGenerator.BytecodeGenerationException bge) {
862 // bytecode generation failed - mark this LambdaForm as to be run in interpretation mode only
863 invocationCounter = -1;
864 failedCompilationCounter().increment();
865 if (LOG_LF_COMPILATION_FAILURE) {
866 System.out.println("LambdaForm compilation failed: " + this);
867 bge.printStackTrace(System.out);
868 }
869 } catch (Error e) {
870 // Pass through any error
871 throw e;
872 } catch (Exception e) {
873 // Wrap any exception
874 throw newInternalError(this.toString(), e);
875 }
876 }
877
878 // The next few routines are called only from assert expressions
879 // They verify that the built-in invokers process the correct raw data types.
880 private static boolean argumentTypesMatch(String sig, Object[] av) {
881 int arity = signatureArity(sig);
882 assert(av.length == arity) : "av.length == arity: av.length=" + av.length + ", arity=" + arity;
883 assert(av[0] instanceof MethodHandle) : "av[0] not instace of MethodHandle: " + av[0];
884 MethodHandle mh = (MethodHandle) av[0];
885 MethodType mt = mh.type();
886 assert(mt.parameterCount() == arity-1);
887 for (int i = 0; i < av.length; i++) {
888 Class<?> pt = (i == 0 ? MethodHandle.class : mt.parameterType(i-1));
889 assert(valueMatches(basicType(sig.charAt(i)), pt, av[i]));
890 }
891 return true;
892 }
893 private static boolean valueMatches(BasicType tc, Class<?> type, Object x) {
894 // The following line is needed because (...)void method handles can use non-void invokers
895 if (type == void.class) tc = V_TYPE; // can drop any kind of value
896 assert tc == basicType(type) : tc + " == basicType(" + type + ")=" + basicType(type);
897 switch (tc) {
898 case I_TYPE: assert checkInt(type, x) : "checkInt(" + type + "," + x +")"; break;
899 case J_TYPE: assert x instanceof Long : "instanceof Long: " + x; break;
900 case F_TYPE: assert x instanceof Float : "instanceof Float: " + x; break;
901 case D_TYPE: assert x instanceof Double : "instanceof Double: " + x; break;
902 case L_TYPE: assert checkRef(type, x) : "checkRef(" + type + "," + x + ")"; break;
903 case V_TYPE: break; // allow anything here; will be dropped
904 default: assert(false);
905 }
906 return true;
907 }
908 private static boolean checkInt(Class<?> type, Object x) {
909 assert(x instanceof Integer);
910 if (type == int.class) return true;
911 Wrapper w = Wrapper.forBasicType(type);
912 assert(w.isSubwordOrInt());
913 Object x1 = Wrapper.INT.wrap(w.wrap(x));
914 return x.equals(x1);
915 }
916 private static boolean checkRef(Class<?> type, Object x) {
917 assert(!type.isPrimitive());
918 if (x == null) return true;
919 if (type.isInterface()) return true;
920 return type.isInstance(x);
921 }
922
923 /** If the invocation count hits the threshold we spin bytecodes and call that subsequently. */
924 private static final int COMPILE_THRESHOLD;
925 static {
926 COMPILE_THRESHOLD = Math.max(-1, MethodHandleStatics.COMPILE_THRESHOLD);
927 }
928 private int invocationCounter = 0; // a value of -1 indicates LambdaForm interpretation mode forever
929
930 private boolean forceInterpretation() {
931 return invocationCounter == -1;
932 }
933
934 @Hidden
935 @DontInline
936 /** Interpretively invoke this form on the given arguments. */
937 Object interpretWithArguments(Object... argumentValues) throws Throwable {
938 if (TRACE_INTERPRETER)
939 return interpretWithArgumentsTracing(argumentValues);
940 checkInvocationCounter();
941 assert(arityCheck(argumentValues));
942 Object[] values = Arrays.copyOf(argumentValues, names.length);
943 for (int i = argumentValues.length; i < values.length; i++) {
944 values[i] = interpretName(names[i], values);
945 }
946 Object rv = (result < 0) ? null : values[result];
947 assert(resultCheck(argumentValues, rv));
948 return rv;
949 }
950
951 @Hidden
952 @DontInline
953 /** Evaluate a single Name within this form, applying its function to its arguments. */
954 Object interpretName(Name name, Object[] values) throws Throwable {
955 if (TRACE_INTERPRETER)
956 traceInterpreter("| interpretName", name.debugString(), (Object[]) null);
957 Object[] arguments = Arrays.copyOf(name.arguments, name.arguments.length, Object[].class);
958 for (int i = 0; i < arguments.length; i++) {
959 Object a = arguments[i];
960 if (a instanceof Name) {
961 int i2 = ((Name)a).index();
962 assert(names[i2] == a);
963 a = values[i2];
964 arguments[i] = a;
965 }
966 }
967 return name.function.invokeWithArguments(arguments);
968 }
969
970 private void checkInvocationCounter() {
971 if (COMPILE_THRESHOLD != 0 &&
972 !forceInterpretation() && invocationCounter < COMPILE_THRESHOLD) {
973 invocationCounter++; // benign race
974 if (invocationCounter >= COMPILE_THRESHOLD) {
975 // Replace vmentry with a bytecode version of this LF.
976 compileToBytecode();
977 }
978 }
979 }
980 Object interpretWithArgumentsTracing(Object... argumentValues) throws Throwable {
981 traceInterpreter("[ interpretWithArguments", this, argumentValues);
982 if (!forceInterpretation() && invocationCounter < COMPILE_THRESHOLD) {
983 int ctr = invocationCounter++; // benign race
984 traceInterpreter("| invocationCounter", ctr);
985 if (invocationCounter >= COMPILE_THRESHOLD) {
986 compileToBytecode();
987 }
988 }
989 Object rval;
990 try {
991 assert(arityCheck(argumentValues));
992 Object[] values = Arrays.copyOf(argumentValues, names.length);
993 for (int i = argumentValues.length; i < values.length; i++) {
994 values[i] = interpretName(names[i], values);
995 }
996 rval = (result < 0) ? null : values[result];
997 } catch (Throwable ex) {
998 traceInterpreter("] throw =>", ex);
999 throw ex;
1000 }
1001 traceInterpreter("] return =>", rval);
1002 return rval;
1003 }
1004
1005 static void traceInterpreter(String event, Object obj, Object... args) {
1006 if (TRACE_INTERPRETER) {
1007 System.out.println("LFI: "+event+" "+(obj != null ? obj : "")+(args != null && args.length != 0 ? Arrays.asList(args) : ""));
1008 }
1009 }
1010 static void traceInterpreter(String event, Object obj) {
1011 traceInterpreter(event, obj, (Object[])null);
1012 }
1013 private boolean arityCheck(Object[] argumentValues) {
1014 assert(argumentValues.length == arity) : arity+"!="+Arrays.asList(argumentValues)+".length";
1015 // also check that the leading (receiver) argument is somehow bound to this LF:
1016 assert(argumentValues[0] instanceof MethodHandle) : "not MH: " + argumentValues[0];
1017 MethodHandle mh = (MethodHandle) argumentValues[0];
1018 assert(mh.internalForm() == this);
1019 // note: argument #0 could also be an interface wrapper, in the future
1020 argumentTypesMatch(basicTypeSignature(), argumentValues);
1021 return true;
1022 }
1023 private boolean resultCheck(Object[] argumentValues, Object result) {
1024 MethodHandle mh = (MethodHandle) argumentValues[0];
1025 MethodType mt = mh.type();
1026 assert(valueMatches(returnType(), mt.returnType(), result));
1027 return true;
1028 }
1029
1030 private boolean isEmpty() {
1031 if (result < 0)
1032 return (names.length == arity);
1033 else if (result == arity && names.length == arity + 1)
1034 return names[arity].isConstantZero();
1035 else
1036 return false;
1037 }
1038
1039 public String toString() {
1040 String lambdaName = lambdaName();
1041 StringBuilder buf = new StringBuilder(lambdaName + "=Lambda(");
1042 for (int i = 0; i < names.length; i++) {
1043 if (i == arity) buf.append(")=>{");
1044 Name n = names[i];
1045 if (i >= arity) buf.append("\n ");
1046 buf.append(n.paramString());
1047 if (i < arity) {
1048 if (i+1 < arity) buf.append(",");
1049 continue;
1050 }
1051 buf.append("=").append(n.exprString());
1052 buf.append(";");
1053 }
1054 if (arity == names.length) buf.append(")=>{");
1055 buf.append(result < 0 ? "void" : names[result]).append("}");
1056 if (TRACE_INTERPRETER) {
1057 // Extra verbosity:
1058 buf.append(":").append(basicTypeSignature());
1059 buf.append("/").append(vmentry);
1060 }
1061 return buf.toString();
1062 }
1063
1064 @Override
1065 public boolean equals(Object obj) {
1066 return obj instanceof LambdaForm && equals((LambdaForm)obj);
1067 }
1068 public boolean equals(LambdaForm that) {
1069 if (this.result != that.result) return false;
1070 return Arrays.equals(this.names, that.names);
1071 }
1072 public int hashCode() {
1073 return result + 31 * Arrays.hashCode(names);
1074 }
1075 LambdaFormEditor editor() {
1076 return LambdaFormEditor.lambdaFormEditor(this);
1077 }
1078
1079 boolean contains(Name name) {
1080 int pos = name.index();
1081 if (pos >= 0) {
1082 return pos < names.length && name.equals(names[pos]);
1083 }
1084 for (int i = arity; i < names.length; i++) {
1085 if (name.equals(names[i]))
1086 return true;
1087 }
1088 return false;
1089 }
1090
1091 static class NamedFunction {
1092 final MemberName member;
1093 private @Stable MethodHandle resolvedHandle;
1094 @Stable MethodHandle invoker;
1095 private final MethodHandleImpl.Intrinsic intrinsicName;
1096
1097 NamedFunction(MethodHandle resolvedHandle) {
1098 this(resolvedHandle.internalMemberName(), resolvedHandle, MethodHandleImpl.Intrinsic.NONE);
1099 }
1100 NamedFunction(MethodHandle resolvedHandle, MethodHandleImpl.Intrinsic intrinsic) {
1101 this(resolvedHandle.internalMemberName(), resolvedHandle, intrinsic);
1102 }
1103 NamedFunction(MemberName member, MethodHandle resolvedHandle) {
1104 this(member, resolvedHandle, MethodHandleImpl.Intrinsic.NONE);
1105 }
1106 NamedFunction(MemberName member, MethodHandle resolvedHandle, MethodHandleImpl.Intrinsic intrinsic) {
1107 this.member = member;
1108 this.resolvedHandle = resolvedHandle;
1109 this.intrinsicName = intrinsic;
1110 assert(resolvedHandle == null ||
1111 resolvedHandle.intrinsicName() == MethodHandleImpl.Intrinsic.NONE ||
1112 resolvedHandle.intrinsicName() == intrinsic) : resolvedHandle.intrinsicName() + " != " + intrinsic;
1113 // The following assert is almost always correct, but will fail for corner cases, such as PrivateInvokeTest.
1114 //assert(!isInvokeBasic(member));
1115 }
1116 NamedFunction(MethodType basicInvokerType) {
1117 assert(basicInvokerType == basicInvokerType.basicType()) : basicInvokerType;
1118 if (basicInvokerType.parameterSlotCount() < MethodType.MAX_MH_INVOKER_ARITY) {
1119 this.resolvedHandle = basicInvokerType.invokers().basicInvoker();
1120 this.member = resolvedHandle.internalMemberName();
1121 } else {
1122 // necessary to pass BigArityTest
1123 this.member = Invokers.invokeBasicMethod(basicInvokerType);
1124 }
1125 this.intrinsicName = MethodHandleImpl.Intrinsic.NONE;
1126 assert(isInvokeBasic(member));
1127 }
1128
1129 private static boolean isInvokeBasic(MemberName member) {
1130 return member != null &&
1131 member.getDeclaringClass() == MethodHandle.class &&
1132 "invokeBasic".equals(member.getName());
1133 }
1134
1135 // The next 2 constructors are used to break circular dependencies on MH.invokeStatic, etc.
1136 // Any LambdaForm containing such a member is not interpretable.
1137 // This is OK, since all such LFs are prepared with special primitive vmentry points.
1138 // And even without the resolvedHandle, the name can still be compiled and optimized.
1139 NamedFunction(Method method) {
1140 this(new MemberName(method));
1141 }
1142 NamedFunction(MemberName member) {
1143 this(member, null);
1144 }
1145
1146 MethodHandle resolvedHandle() {
1147 if (resolvedHandle == null) resolve();
1148 return resolvedHandle;
1149 }
1150
1151 synchronized void resolve() {
1152 if (resolvedHandle == null) {
1153 resolvedHandle = DirectMethodHandle.make(member);
1154 }
1155 }
1156
1157 @Override
1158 public boolean equals(Object other) {
1159 if (this == other) return true;
1160 if (other == null) return false;
1161 if (!(other instanceof NamedFunction)) return false;
1162 NamedFunction that = (NamedFunction) other;
1163 return this.member != null && this.member.equals(that.member);
1164 }
1165
1166 @Override
1167 public int hashCode() {
1168 if (member != null)
1169 return member.hashCode();
1170 return super.hashCode();
1171 }
1172
1173 static final MethodType INVOKER_METHOD_TYPE =
1174 MethodType.methodType(Object.class, MethodHandle.class, Object[].class);
1175
1176 private static MethodHandle computeInvoker(MethodTypeForm typeForm) {
1177 typeForm = typeForm.basicType().form(); // normalize to basic type
1178 MethodHandle mh = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
1179 if (mh != null) return mh;
1180 MemberName invoker = InvokerBytecodeGenerator.generateNamedFunctionInvoker(typeForm); // this could take a while
1181 mh = DirectMethodHandle.make(invoker);
1182 MethodHandle mh2 = typeForm.cachedMethodHandle(MethodTypeForm.MH_NF_INV);
1183 if (mh2 != null) return mh2; // benign race
1184 if (!mh.type().equals(INVOKER_METHOD_TYPE))
1185 throw newInternalError(mh.debugString());
1186 return typeForm.setCachedMethodHandle(MethodTypeForm.MH_NF_INV, mh);
1187 }
1188
1189 @Hidden
1190 Object invokeWithArguments(Object... arguments) throws Throwable {
1191 // If we have a cached invoker, call it right away.
1192 // NOTE: The invoker always returns a reference value.
1193 if (TRACE_INTERPRETER) return invokeWithArgumentsTracing(arguments);
1194 return invoker().invokeBasic(resolvedHandle(), arguments);
1195 }
1196
1197 @Hidden
1198 Object invokeWithArgumentsTracing(Object[] arguments) throws Throwable {
1199 Object rval;
1200 try {
1201 traceInterpreter("[ call", this, arguments);
1202 if (invoker == null) {
1203 traceInterpreter("| getInvoker", this);
1204 invoker();
1205 }
1206 // resolvedHandle might be uninitialized, ok for tracing
1207 if (resolvedHandle == null) {
1208 traceInterpreter("| resolve", this);
1209 resolvedHandle();
1210 }
1211 rval = invoker().invokeBasic(resolvedHandle(), arguments);
1212 } catch (Throwable ex) {
1213 traceInterpreter("] throw =>", ex);
1214 throw ex;
1215 }
1216 traceInterpreter("] return =>", rval);
1217 return rval;
1218 }
1219
1220 private MethodHandle invoker() {
1221 if (invoker != null) return invoker;
1222 // Get an invoker and cache it.
1223 return invoker = computeInvoker(methodType().form());
1224 }
1225
1226 MethodType methodType() {
1227 if (resolvedHandle != null)
1228 return resolvedHandle.type();
1229 else
1230 // only for certain internal LFs during bootstrapping
1231 return member.getInvocationType();
1232 }
1233
1234 MemberName member() {
1235 assert(assertMemberIsConsistent());
1236 return member;
1237 }
1238
1239 // Called only from assert.
1240 private boolean assertMemberIsConsistent() {
1241 if (resolvedHandle instanceof DirectMethodHandle) {
1242 MemberName m = resolvedHandle.internalMemberName();
1243 assert(m.equals(member));
1244 }
1245 return true;
1246 }
1247
1248 Class<?> memberDeclaringClassOrNull() {
1249 return (member == null) ? null : member.getDeclaringClass();
1250 }
1251
1252 BasicType returnType() {
1253 return basicType(methodType().returnType());
1254 }
1255
1256 BasicType parameterType(int n) {
1257 return basicType(methodType().parameterType(n));
1258 }
1259
1260 int arity() {
1261 return methodType().parameterCount();
1262 }
1263
1264 public String toString() {
1265 if (member == null) return String.valueOf(resolvedHandle);
1266 return member.getDeclaringClass().getSimpleName()+"."+member.getName();
1267 }
1268
1269 public boolean isIdentity() {
1270 return this.equals(identity(returnType()));
1271 }
1272
1273 public boolean isConstantZero() {
1274 return this.equals(constantZero(returnType()));
1275 }
1276
1277 public MethodHandleImpl.Intrinsic intrinsicName() {
1278 return intrinsicName;
1279 }
1280 }
1281
1282 public static String basicTypeSignature(MethodType type) {
1283 int params = type.parameterCount();
1284 char[] sig = new char[params + 2];
1285 int sigp = 0;
1286 while (sigp < params) {
1287 sig[sigp] = basicTypeChar(type.parameterType(sigp++));
1288 }
1289 sig[sigp++] = '_';
1290 sig[sigp++] = basicTypeChar(type.returnType());
1291 assert(sigp == sig.length);
1292 return String.valueOf(sig);
1293 }
1294 public static String shortenSignature(String signature) {
1295 // Hack to make signatures more readable when they show up in method names.
1296 final int NO_CHAR = -1, MIN_RUN = 3;
1297 int c0, c1 = NO_CHAR, c1reps = 0;
1298 StringBuilder buf = null;
1299 int len = signature.length();
1300 if (len < MIN_RUN) return signature;
1301 for (int i = 0; i <= len; i++) {
1302 // shift in the next char:
1303 c0 = c1; c1 = (i == len ? NO_CHAR : signature.charAt(i));
1304 if (c1 == c0) { ++c1reps; continue; }
1305 // shift in the next count:
1306 int c0reps = c1reps; c1reps = 1;
1307 // end of a character run
1308 if (c0reps < MIN_RUN) {
1309 if (buf != null) {
1310 while (--c0reps >= 0)
1311 buf.append((char)c0);
1312 }
1313 continue;
1314 }
1315 // found three or more in a row
1316 if (buf == null)
1317 buf = new StringBuilder().append(signature, 0, i - c0reps);
1318 buf.append((char)c0).append(c0reps);
1319 }
1320 return (buf == null) ? signature : buf.toString();
1321 }
1322
1323 static final class Name {
1324 final BasicType type;
1325 @Stable short index;
1326 final NamedFunction function;
1327 final Object constraint; // additional type information, if not null
1328 @Stable final Object[] arguments;
1329
1330 private Name(int index, BasicType type, NamedFunction function, Object[] arguments) {
1331 this.index = (short)index;
1332 this.type = type;
1333 this.function = function;
1334 this.arguments = arguments;
1335 this.constraint = null;
1336 assert(this.index == index);
1337 }
1338 private Name(Name that, Object constraint) {
1339 this.index = that.index;
1340 this.type = that.type;
1341 this.function = that.function;
1342 this.arguments = that.arguments;
1343 this.constraint = constraint;
1344 assert(constraint == null || isParam()); // only params have constraints
1345 assert(constraint == null || constraint instanceof BoundMethodHandle.SpeciesData || constraint instanceof Class);
1346 }
1347 Name(MethodHandle function, Object... arguments) {
1348 this(new NamedFunction(function), arguments);
1349 }
1350 Name(MethodType functionType, Object... arguments) {
1351 this(new NamedFunction(functionType), arguments);
1352 assert(arguments[0] instanceof Name && ((Name)arguments[0]).type == L_TYPE);
1353 }
1354 Name(MemberName function, Object... arguments) {
1355 this(new NamedFunction(function), arguments);
1356 }
1357 Name(NamedFunction function, Object... arguments) {
1358 this(-1, function.returnType(), function, arguments = Arrays.copyOf(arguments, arguments.length, Object[].class));
1359 assert(typesMatch(function, arguments));
1360 }
1361 /** Create a raw parameter of the given type, with an expected index. */
1362 Name(int index, BasicType type) {
1363 this(index, type, null, null);
1364 }
1365 /** Create a raw parameter of the given type. */
1366 Name(BasicType type) { this(-1, type); }
1367
1368 BasicType type() { return type; }
1369 int index() { return index; }
1370 boolean initIndex(int i) {
1371 if (index != i) {
1372 if (index != -1) return false;
1373 index = (short)i;
1374 }
1375 return true;
1376 }
1377 char typeChar() {
1378 return type.btChar;
1379 }
1380
1381 void resolve() {
1382 if (function != null)
1383 function.resolve();
1384 }
1385
1386 Name newIndex(int i) {
1387 if (initIndex(i)) return this;
1388 return cloneWithIndex(i);
1389 }
1390 Name cloneWithIndex(int i) {
1391 Object[] newArguments = (arguments == null) ? null : arguments.clone();
1392 return new Name(i, type, function, newArguments).withConstraint(constraint);
1393 }
1394 Name withConstraint(Object constraint) {
1395 if (constraint == this.constraint) return this;
1396 return new Name(this, constraint);
1397 }
1398 Name replaceName(Name oldName, Name newName) { // FIXME: use replaceNames uniformly
1399 if (oldName == newName) return this;
1400 @SuppressWarnings("LocalVariableHidesMemberVariable")
1401 Object[] arguments = this.arguments;
1402 if (arguments == null) return this;
1403 boolean replaced = false;
1404 for (int j = 0; j < arguments.length; j++) {
1405 if (arguments[j] == oldName) {
1406 if (!replaced) {
1407 replaced = true;
1408 arguments = arguments.clone();
1409 }
1410 arguments[j] = newName;
1411 }
1412 }
1413 if (!replaced) return this;
1414 return new Name(function, arguments);
1415 }
1416 /** In the arguments of this Name, replace oldNames[i] pairwise by newNames[i].
1417 * Limit such replacements to {@code start<=i<end}. Return possibly changed self.
1418 */
1419 Name replaceNames(Name[] oldNames, Name[] newNames, int start, int end) {
1420 if (start >= end) return this;
1421 @SuppressWarnings("LocalVariableHidesMemberVariable")
1422 Object[] arguments = this.arguments;
1423 boolean replaced = false;
1424 eachArg:
1425 for (int j = 0; j < arguments.length; j++) {
1426 if (arguments[j] instanceof Name) {
1427 Name n = (Name) arguments[j];
1428 int check = n.index;
1429 // harmless check to see if the thing is already in newNames:
1430 if (check >= 0 && check < newNames.length && n == newNames[check])
1431 continue eachArg;
1432 // n might not have the correct index: n != oldNames[n.index].
1433 for (int i = start; i < end; i++) {
1434 if (n == oldNames[i]) {
1435 if (n == newNames[i])
1436 continue eachArg;
1437 if (!replaced) {
1438 replaced = true;
1439 arguments = arguments.clone();
1440 }
1441 arguments[j] = newNames[i];
1442 continue eachArg;
1443 }
1444 }
1445 }
1446 }
1447 if (!replaced) return this;
1448 return new Name(function, arguments);
1449 }
1450 void internArguments() {
1451 @SuppressWarnings("LocalVariableHidesMemberVariable")
1452 Object[] arguments = this.arguments;
1453 for (int j = 0; j < arguments.length; j++) {
1454 if (arguments[j] instanceof Name) {
1455 Name n = (Name) arguments[j];
1456 if (n.isParam() && n.index < INTERNED_ARGUMENT_LIMIT)
1457 arguments[j] = internArgument(n);
1458 }
1459 }
1460 }
1461 boolean isParam() {
1462 return function == null;
1463 }
1464 boolean isConstantZero() {
1465 return !isParam() && arguments.length == 0 && function.isConstantZero();
1466 }
1467
1468 boolean refersTo(Class<?> declaringClass, String methodName) {
1469 return function != null &&
1470 function.member() != null && function.member().refersTo(declaringClass, methodName);
1471 }
1472
1473 /**
1474 * Check if MemberName is a call to MethodHandle.invokeBasic.
1475 */
1476 boolean isInvokeBasic() {
1477 if (function == null)
1478 return false;
1479 if (arguments.length < 1)
1480 return false; // must have MH argument
1481 MemberName member = function.member();
1482 return member != null && member.refersTo(MethodHandle.class, "invokeBasic") &&
1483 !member.isPublic() && !member.isStatic();
1484 }
1485
1486 /**
1487 * Check if MemberName is a call to MethodHandle.linkToStatic, etc.
1488 */
1489 boolean isLinkerMethodInvoke() {
1490 if (function == null)
1491 return false;
1492 if (arguments.length < 1)
1493 return false; // must have MH argument
1494 MemberName member = function.member();
1495 return member != null &&
1496 member.getDeclaringClass() == MethodHandle.class &&
1497 !member.isPublic() && member.isStatic() &&
1498 member.getName().startsWith("linkTo");
1499 }
1500
1501 public String toString() {
1502 return (isParam()?"a":"t")+(index >= 0 ? index : System.identityHashCode(this))+":"+typeChar();
1503 }
1504 public String debugString() {
1505 String s = paramString();
1506 return (function == null) ? s : s + "=" + exprString();
1507 }
1508 public String paramString() {
1509 String s = toString();
1510 Object c = constraint;
1511 if (c == null)
1512 return s;
1513 if (c instanceof Class) c = ((Class<?>)c).getSimpleName();
1514 return s + "/" + c;
1515 }
1516 public String exprString() {
1517 if (function == null) return toString();
1518 StringBuilder buf = new StringBuilder(function.toString());
1519 buf.append("(");
1520 String cma = "";
1521 for (Object a : arguments) {
1522 buf.append(cma); cma = ",";
1523 if (a instanceof Name || a instanceof Integer)
1524 buf.append(a);
1525 else
1526 buf.append("(").append(a).append(")");
1527 }
1528 buf.append(")");
1529 return buf.toString();
1530 }
1531
1532 private boolean typesMatch(NamedFunction function, Object ... arguments) {
1533 assert(arguments.length == function.arity()) : "arity mismatch: arguments.length=" + arguments.length + " == function.arity()=" + function.arity() + " in " + debugString();
1534 for (int i = 0; i < arguments.length; i++) {
1535 assert (typesMatch(function.parameterType(i), arguments[i])) : "types don't match: function.parameterType(" + i + ")=" + function.parameterType(i) + ", arguments[" + i + "]=" + arguments[i] + " in " + debugString();
1536 }
1537 return true;
1538 }
1539
1540 private static boolean typesMatch(BasicType parameterType, Object object) {
1541 if (object instanceof Name) {
1542 return ((Name)object).type == parameterType;
1543 }
1544 switch (parameterType) {
1545 case I_TYPE: return object instanceof Integer;
1546 case J_TYPE: return object instanceof Long;
1547 case F_TYPE: return object instanceof Float;
1548 case D_TYPE: return object instanceof Double;
1549 }
1550 assert(parameterType == L_TYPE);
1551 return true;
1552 }
1553
1554 /** Return the index of the last occurrence of n in the argument array.
1555 * Return -1 if the name is not used.
1556 */
1557 int lastUseIndex(Name n) {
1558 if (arguments == null) return -1;
1559 for (int i = arguments.length; --i >= 0; ) {
1560 if (arguments[i] == n) return i;
1561 }
1562 return -1;
1563 }
1564
1565 /** Return the number of occurrences of n in the argument array.
1566 * Return 0 if the name is not used.
1567 */
1568 int useCount(Name n) {
1569 if (arguments == null) return 0;
1570 int count = 0;
1571 for (int i = arguments.length; --i >= 0; ) {
1572 if (arguments[i] == n) ++count;
1573 }
1574 return count;
1575 }
1576
1577 boolean contains(Name n) {
1578 return this == n || lastUseIndex(n) >= 0;
1579 }
1580
1581 public boolean equals(Name that) {
1582 if (this == that) return true;
1583 if (isParam())
1584 // each parameter is a unique atom
1585 return false; // this != that
1586 return
1587 //this.index == that.index &&
1588 this.type == that.type &&
1589 this.function.equals(that.function) &&
1590 Arrays.equals(this.arguments, that.arguments);
1591 }
1592 @Override
1593 public boolean equals(Object x) {
1594 return x instanceof Name && equals((Name)x);
1595 }
1596 @Override
1597 public int hashCode() {
1598 if (isParam())
1599 return index | (type.ordinal() << 8);
1600 return function.hashCode() ^ Arrays.hashCode(arguments);
1601 }
1602 }
1603
1604 /** Return the index of the last name which contains n as an argument.
1605 * Return -1 if the name is not used. Return names.length if it is the return value.
1606 */
1607 int lastUseIndex(Name n) {
1608 int ni = n.index, nmax = names.length;
1609 assert(names[ni] == n);
1610 if (result == ni) return nmax; // live all the way beyond the end
1611 for (int i = nmax; --i > ni; ) {
1612 if (names[i].lastUseIndex(n) >= 0)
1613 return i;
1614 }
1615 return -1;
1616 }
1617
1618 /** Return the number of times n is used as an argument or return value. */
1619 int useCount(Name n) {
1620 int nmax = names.length;
1621 int end = lastUseIndex(n);
1622 if (end < 0) return 0;
1623 int count = 0;
1624 if (end == nmax) { count++; end--; }
1625 int beg = n.index() + 1;
1626 if (beg < arity) beg = arity;
1627 for (int i = beg; i <= end; i++) {
1628 count += names[i].useCount(n);
1629 }
1630 return count;
1631 }
1632
1633 static Name argument(int which, BasicType type) {
1634 if (which >= INTERNED_ARGUMENT_LIMIT)
1635 return new Name(which, type);
1636 return INTERNED_ARGUMENTS[type.ordinal()][which];
1637 }
1638 static Name internArgument(Name n) {
1639 assert(n.isParam()) : "not param: " + n;
1640 assert(n.index < INTERNED_ARGUMENT_LIMIT);
1641 if (n.constraint != null) return n;
1642 return argument(n.index, n.type);
1643 }
1644 static Name[] arguments(int extra, MethodType types) {
1645 int length = types.parameterCount();
1646 Name[] names = new Name[length + extra];
1647 for (int i = 0; i < length; i++)
1648 names[i] = argument(i, basicType(types.parameterType(i)));
1649 return names;
1650 }
1651 static final int INTERNED_ARGUMENT_LIMIT = 10;
1652 private static final Name[][] INTERNED_ARGUMENTS
1653 = new Name[ARG_TYPE_LIMIT][INTERNED_ARGUMENT_LIMIT];
1654 static {
1655 for (BasicType type : BasicType.ARG_TYPES) {
1656 int ord = type.ordinal();
1657 for (int i = 0; i < INTERNED_ARGUMENTS[ord].length; i++) {
1658 INTERNED_ARGUMENTS[ord][i] = new Name(i, type);
1659 }
1660 }
1661 }
1662
1663 private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
1664
1665 static LambdaForm identityForm(BasicType type) {
1666 int ord = type.ordinal();
1667 LambdaForm form = LF_identity[ord];
1668 if (form != null) {
1669 return form;
1670 }
1671 createFormsFor(type);
1672 return LF_identity[ord];
1673 }
1674
1675 static LambdaForm zeroForm(BasicType type) {
1676 int ord = type.ordinal();
1677 LambdaForm form = LF_zero[ord];
1678 if (form != null) {
1679 return form;
1680 }
1681 createFormsFor(type);
1682 return LF_zero[ord];
1683 }
1684
1685 static NamedFunction identity(BasicType type) {
1686 int ord = type.ordinal();
1687 NamedFunction function = NF_identity[ord];
1688 if (function != null) {
1689 return function;
1690 }
1691 createFormsFor(type);
1692 return NF_identity[ord];
1693 }
1694
1695 static NamedFunction constantZero(BasicType type) {
1696 int ord = type.ordinal();
1697 NamedFunction function = NF_zero[ord];
1698 if (function != null) {
1699 return function;
1700 }
1701 createFormsFor(type);
1702 return NF_zero[ord];
1703 }
1704
1705 private static final @Stable LambdaForm[] LF_identity = new LambdaForm[TYPE_LIMIT];
1706 private static final @Stable LambdaForm[] LF_zero = new LambdaForm[TYPE_LIMIT];
1707 private static final @Stable NamedFunction[] NF_identity = new NamedFunction[TYPE_LIMIT];
1708 private static final @Stable NamedFunction[] NF_zero = new NamedFunction[TYPE_LIMIT];
1709
1710 private static synchronized void createFormsFor(BasicType type) {
1711 final int ord = type.ordinal();
1712 LambdaForm idForm = LF_identity[ord];
1713 if (idForm != null) {
1714 return;
1715 }
1716 char btChar = type.basicTypeChar();
1717 boolean isVoid = (type == V_TYPE);
1718 Class<?> btClass = type.btClass;
1719 MethodType zeType = MethodType.methodType(btClass);
1720 MethodType idType = (isVoid) ? zeType : MethodType.methodType(btClass, btClass);
1721
1722 // Look up symbolic names. It might not be necessary to have these,
1723 // but if we need to emit direct references to bytecodes, it helps.
1724 // Zero is built from a call to an identity function with a constant zero input.
1725 MemberName idMem = new MemberName(LambdaForm.class, "identity_"+btChar, idType, REF_invokeStatic);
1726 MemberName zeMem = null;
1727 try {
1728 idMem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, idMem, null, NoSuchMethodException.class);
1729 if (!isVoid) {
1730 zeMem = new MemberName(LambdaForm.class, "zero_"+btChar, zeType, REF_invokeStatic);
1731 zeMem = IMPL_NAMES.resolveOrFail(REF_invokeStatic, zeMem, null, NoSuchMethodException.class);
1732 }
1733 } catch (IllegalAccessException|NoSuchMethodException ex) {
1734 throw newInternalError(ex);
1735 }
1736
1737 NamedFunction idFun;
1738 LambdaForm zeForm;
1739 NamedFunction zeFun;
1740
1741 // Create the LFs and NamedFunctions. Precompiling LFs to byte code is needed to break circular
1742 // bootstrap dependency on this method in case we're interpreting LFs
1743 if (isVoid) {
1744 Name[] idNames = new Name[] { argument(0, L_TYPE) };
1745 idForm = new LambdaForm(1, idNames, VOID_RESULT, Kind.IDENTITY);
1746 idForm.compileToBytecode();
1747 idFun = new NamedFunction(idMem, SimpleMethodHandle.make(idMem.getInvocationType(), idForm));
1748
1749 zeForm = idForm;
1750 zeFun = idFun;
1751 } else {
1752 Name[] idNames = new Name[] { argument(0, L_TYPE), argument(1, type) };
1753 idForm = new LambdaForm(2, idNames, 1, Kind.IDENTITY);
1754 idForm.compileToBytecode();
1755 idFun = new NamedFunction(idMem, SimpleMethodHandle.make(idMem.getInvocationType(), idForm),
1756 MethodHandleImpl.Intrinsic.IDENTITY);
1757
1758 Object zeValue = Wrapper.forBasicType(btChar).zero();
1759 Name[] zeNames = new Name[] { argument(0, L_TYPE), new Name(idFun, zeValue) };
1760 zeForm = new LambdaForm(1, zeNames, 1, Kind.ZERO);
1761 zeForm.compileToBytecode();
1762 zeFun = new NamedFunction(zeMem, SimpleMethodHandle.make(zeMem.getInvocationType(), zeForm),
1763 MethodHandleImpl.Intrinsic.ZERO);
1764 }
1765
1766 LF_zero[ord] = zeForm;
1767 NF_zero[ord] = zeFun;
1768 LF_identity[ord] = idForm;
1769 NF_identity[ord] = idFun;
1770
1771 assert(idFun.isIdentity());
1772 assert(zeFun.isConstantZero());
1773 assert(new Name(zeFun).isConstantZero());
1774 }
1775
1776 // Avoid appealing to ValueConversions at bootstrap time:
1777 private static int identity_I(int x) { return x; }
1778 private static long identity_J(long x) { return x; }
1779 private static float identity_F(float x) { return x; }
1780 private static double identity_D(double x) { return x; }
1781 private static Object identity_L(Object x) { return x; }
1782 private static void identity_V() { return; }
1783 private static int zero_I() { return 0; }
1784 private static long zero_J() { return 0; }
1785 private static float zero_F() { return 0; }
1786 private static double zero_D() { return 0; }
1787 private static Object zero_L() { return null; }
1788
1789 /**
1790 * Internal marker for byte-compiled LambdaForms.
1791 */
1792 /*non-public*/
1793 @Target(ElementType.METHOD)
1794 @Retention(RetentionPolicy.RUNTIME)
1795 @interface Compiled {
1796 }
1797
1798 /**
1799 * Internal marker for LambdaForm interpreter frames.
1800 */
1801 /*non-public*/
1802 @Target(ElementType.METHOD)
1803 @Retention(RetentionPolicy.RUNTIME)
1804 @interface Hidden {
1805 }
1806
1807 private static final HashMap<String,Integer> DEBUG_NAME_COUNTERS;
1808 private static final HashMap<LambdaForm,String> DEBUG_NAMES;
1809 static {
1810 if (debugEnabled()) {
1811 DEBUG_NAME_COUNTERS = new HashMap<>();
1812 DEBUG_NAMES = new HashMap<>();
1813 } else {
1814 DEBUG_NAME_COUNTERS = null;
1815 DEBUG_NAMES = null;
1816 }
1817 }
1818
1819 static {
1820 // The Holder class will contain pre-generated forms resolved
1821 // using MemberName.getFactory(). However, that doesn't initialize the
1822 // class, which subtly breaks inlining etc. By forcing
1823 // initialization of the Holder class we avoid these issues.
1824 UNSAFE.ensureClassInitialized(Holder.class);
1825 }
1826
1827 /* Placeholder class for zero and identity forms generated ahead of time */
1828 final class Holder {}
1829
1830 // The following hack is necessary in order to suppress TRACE_INTERPRETER
1831 // during execution of the static initializes of this class.
1832 // Turning on TRACE_INTERPRETER too early will cause
1833 // stack overflows and other misbehavior during attempts to trace events
1834 // that occur during LambdaForm.<clinit>.
1835 // Therefore, do not move this line higher in this file, and do not remove.
1836 private static final boolean TRACE_INTERPRETER = MethodHandleStatics.TRACE_INTERPRETER;
1837 }