1 /*
2 * Copyright (c) 1998, 2023, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "cds/metaspaceShared.hpp"
27 #include "classfile/vmClasses.hpp"
28 #include "interpreter/bytecodes.hpp"
29 #include "interpreter/bytecodeStream.hpp"
30 #include "interpreter/interpreter.hpp"
31 #include "interpreter/rewriter.hpp"
32 #include "memory/metadataFactory.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "oops/generateOopMap.hpp"
35 #include "oops/resolvedIndyEntry.hpp"
36 #include "prims/methodHandles.hpp"
37 #include "runtime/arguments.hpp"
38 #include "runtime/fieldDescriptor.inline.hpp"
39 #include "runtime/handles.inline.hpp"
40
41 // Computes a CPC map (new_index -> original_index) for constant pool entries
42 // that are referred to by the interpreter at runtime via the constant pool cache.
43 // Also computes a CP map (original_index -> new_index).
44 // Marks entries in CP which require additional processing.
45 void Rewriter::compute_index_maps() {
46 const int length = _pool->length();
47 init_maps(length);
48 bool saw_mh_symbol = false;
49 for (int i = 0; i < length; i++) {
50 int tag = _pool->tag_at(i).value();
51 switch (tag) {
52 case JVM_CONSTANT_InterfaceMethodref:
53 case JVM_CONSTANT_Fieldref : // fall through
54 case JVM_CONSTANT_Methodref : // fall through
55 add_cp_cache_entry(i);
56 break;
57 case JVM_CONSTANT_Dynamic:
58 assert(_pool->has_dynamic_constant(), "constant pool's _has_dynamic_constant flag not set");
59 add_resolved_references_entry(i);
60 break;
61 case JVM_CONSTANT_String : // fall through
62 case JVM_CONSTANT_MethodHandle : // fall through
63 case JVM_CONSTANT_MethodType : // fall through
64 add_resolved_references_entry(i);
65 break;
66 case JVM_CONSTANT_Utf8:
67 if (_pool->symbol_at(i) == vmSymbols::java_lang_invoke_MethodHandle() ||
68 _pool->symbol_at(i) == vmSymbols::java_lang_invoke_VarHandle()) {
69 saw_mh_symbol = true;
70 }
71 break;
72 }
73 }
74
75 // Record limits of resolved reference map for constant pool cache indices
76 record_map_limits();
77
78 guarantee((int) _cp_cache_map.length() - 1 <= (int) ((u2)-1),
79 "all cp cache indexes fit in a u2");
80
81 if (saw_mh_symbol) {
82 _method_handle_invokers.at_grow(length, 0);
83 }
84 }
85
86 // Unrewrite the bytecodes if an error occurs.
87 void Rewriter::restore_bytecodes(Thread* thread) {
88 int len = _methods->length();
89 bool invokespecial_error = false;
90
91 for (int i = len-1; i >= 0; i--) {
92 Method* method = _methods->at(i);
93 scan_method(thread, method, true, &invokespecial_error);
94 assert(!invokespecial_error, "reversing should not get an invokespecial error");
95 }
96 }
97
98 // Creates a constant pool cache given a CPC map
99 void Rewriter::make_constant_pool_cache(TRAPS) {
100 ClassLoaderData* loader_data = _pool->pool_holder()->class_loader_data();
101 ConstantPoolCache* cache =
102 ConstantPoolCache::allocate(loader_data, _cp_cache_map,
103 _invokedynamic_references_map, _initialized_indy_entries, CHECK);
104
105 // initialize object cache in constant pool
106 _pool->set_cache(cache);
107 cache->set_constant_pool(_pool());
108
109 // _resolved_references is stored in pool->cache(), so need to be done after
110 // the above lines.
111 _pool->initialize_resolved_references(loader_data, _resolved_references_map,
112 _resolved_reference_limit,
113 THREAD);
114 #if INCLUDE_CDS
115 if (!HAS_PENDING_EXCEPTION && Arguments::is_dumping_archive()) {
116 if (_pool->pool_holder()->is_shared()) {
117 assert(DynamicDumpSharedSpaces, "must be");
118 // We are linking a shared class from the base archive. This
119 // class won't be written into the dynamic archive, so there's no
120 // need to save its CpCaches.
121 } else {
122 cache->save_for_archive(THREAD);
123 }
124 }
125 #endif
126
127 // Clean up constant pool cache if initialize_resolved_references() failed.
128 if (HAS_PENDING_EXCEPTION) {
129 MetadataFactory::free_metadata(loader_data, cache);
130 _pool->set_cache(nullptr); // so the verifier isn't confused
131 }
132 }
133
134
135
136 // The new finalization semantics says that registration of
137 // finalizable objects must be performed on successful return from the
138 // Object.<init> constructor. We could implement this trivially if
139 // <init> were never rewritten but since JVMTI allows this to occur, a
140 // more complicated solution is required. A special return bytecode
141 // is used only by Object.<init> to signal the finalization
142 // registration point. Additionally local 0 must be preserved so it's
143 // available to pass to the registration function. For simplicity we
144 // require that local 0 is never overwritten so it's available as an
145 // argument for registration.
146
147 void Rewriter::rewrite_Object_init(const methodHandle& method, TRAPS) {
148 RawBytecodeStream bcs(method);
149 while (!bcs.is_last_bytecode()) {
150 Bytecodes::Code opcode = bcs.raw_next();
151 switch (opcode) {
152 case Bytecodes::_return: *bcs.bcp() = Bytecodes::_return_register_finalizer; break;
153
154 case Bytecodes::_istore:
155 case Bytecodes::_lstore:
156 case Bytecodes::_fstore:
157 case Bytecodes::_dstore:
158 case Bytecodes::_astore:
159 if (bcs.get_index() != 0) continue;
160
161 // fall through
162 case Bytecodes::_istore_0:
163 case Bytecodes::_lstore_0:
164 case Bytecodes::_fstore_0:
165 case Bytecodes::_dstore_0:
166 case Bytecodes::_astore_0:
167 THROW_MSG(vmSymbols::java_lang_IncompatibleClassChangeError(),
168 "can't overwrite local 0 in Object.<init>");
169 break;
170
171 default:
172 break;
173 }
174 }
175 }
176
177
178 // Rewrite a classfile-order CP index into a native-order CPC index.
179 void Rewriter::rewrite_member_reference(address bcp, int offset, bool reverse) {
180 address p = bcp + offset;
181 if (!reverse) {
182 int cp_index = Bytes::get_Java_u2(p);
183 int cache_index = cp_entry_to_cp_cache(cp_index);
184 Bytes::put_native_u2(p, (u2)cache_index);
185 if (!_method_handle_invokers.is_empty())
186 maybe_rewrite_invokehandle(p - 1, cp_index, cache_index, reverse);
187 } else {
188 int cache_index = Bytes::get_native_u2(p);
189 int pool_index = cp_cache_entry_pool_index(cache_index);
190 Bytes::put_Java_u2(p, (u2)pool_index);
191 if (!_method_handle_invokers.is_empty())
192 maybe_rewrite_invokehandle(p - 1, pool_index, cache_index, reverse);
193 }
194 }
195
196 // If the constant pool entry for invokespecial is InterfaceMethodref,
197 // we need to add a separate cpCache entry for its resolution, because it is
198 // different than the resolution for invokeinterface with InterfaceMethodref.
199 // These cannot share cpCache entries.
200 void Rewriter::rewrite_invokespecial(address bcp, int offset, bool reverse, bool* invokespecial_error) {
201 address p = bcp + offset;
202 if (!reverse) {
203 int cp_index = Bytes::get_Java_u2(p);
204 if (_pool->tag_at(cp_index).is_interface_method()) {
205 int cache_index = add_invokespecial_cp_cache_entry(cp_index);
206 if (cache_index != (int)(jushort) cache_index) {
207 *invokespecial_error = true;
208 }
209 Bytes::put_native_u2(p, (u2)cache_index);
210 } else {
211 rewrite_member_reference(bcp, offset, reverse);
212 }
213 } else {
214 rewrite_member_reference(bcp, offset, reverse);
215 }
216 }
217
218
219 // Adjust the invocation bytecode for a signature-polymorphic method (MethodHandle.invoke, etc.)
220 void Rewriter::maybe_rewrite_invokehandle(address opc, int cp_index, int cache_index, bool reverse) {
221 if (!reverse) {
222 if ((*opc) == (u1)Bytecodes::_invokevirtual ||
223 // allow invokespecial as an alias, although it would be very odd:
224 (*opc) == (u1)Bytecodes::_invokespecial) {
225 assert(_pool->tag_at(cp_index).is_method(), "wrong index");
226 // Determine whether this is a signature-polymorphic method.
227 if (cp_index >= _method_handle_invokers.length()) return;
228 int status = _method_handle_invokers.at(cp_index);
229 assert(status >= -1 && status <= 1, "oob tri-state");
230 if (status == 0) {
231 if (_pool->uncached_klass_ref_at_noresolve(cp_index) == vmSymbols::java_lang_invoke_MethodHandle() &&
232 MethodHandles::is_signature_polymorphic_name(vmClasses::MethodHandle_klass(),
233 _pool->uncached_name_ref_at(cp_index))) {
234 // we may need a resolved_refs entry for the appendix
235 add_invokedynamic_resolved_references_entry(cp_index, cache_index);
236 status = +1;
237 } else if (_pool->uncached_klass_ref_at_noresolve(cp_index) == vmSymbols::java_lang_invoke_VarHandle() &&
238 MethodHandles::is_signature_polymorphic_name(vmClasses::VarHandle_klass(),
239 _pool->uncached_name_ref_at(cp_index))) {
240 // we may need a resolved_refs entry for the appendix
241 add_invokedynamic_resolved_references_entry(cp_index, cache_index);
242 status = +1;
243 } else {
244 status = -1;
245 }
246 _method_handle_invokers.at(cp_index) = status;
247 }
248 // We use a special internal bytecode for such methods (if non-static).
249 // The basic reason for this is that such methods need an extra "appendix" argument
250 // to transmit the call site's intended call type.
251 if (status > 0) {
252 (*opc) = (u1)Bytecodes::_invokehandle;
253 }
254 }
255 } else {
256 // Do not need to look at cp_index.
257 if ((*opc) == (u1)Bytecodes::_invokehandle) {
258 (*opc) = (u1)Bytecodes::_invokevirtual;
259 // Ignore corner case of original _invokespecial instruction.
260 // This is safe because (a) the signature polymorphic method was final, and
261 // (b) the implementation of MethodHandle will not call invokespecial on it.
262 }
263 }
264 }
265
266
267 void Rewriter::rewrite_invokedynamic(address bcp, int offset, bool reverse) {
268 address p = bcp + offset;
269 assert(p[-1] == Bytecodes::_invokedynamic, "not invokedynamic bytecode");
270 if (!reverse) {
271 int cp_index = Bytes::get_Java_u2(p);
272 int resolved_index = add_invokedynamic_resolved_references_entry(cp_index, -1); // Indy no longer has a CPCE
273 // Replace the trailing four bytes with an index to the array of
274 // indy resolution information in the CPC. There is one entry for
275 // each bytecode, even if they make the same call. In other words,
276 // the CPC-to-CP relation is many-to-one for invokedynamic entries.
277 // This means we must use a larger index size than u2 to address
278 // all these entries. That is the main reason invokedynamic
279 // must have a five-byte instruction format. (Of course, other JVM
280 // implementations can use the bytes for other purposes.)
281 // Note: We use native_u4 format exclusively for 4-byte indexes.
282 Bytes::put_native_u4(p, ConstantPool::encode_invokedynamic_index(_invokedynamic_index));
283 _invokedynamic_index++;
284
285 // Collect invokedynamic information before creating ResolvedInvokeDynamicInfo array
286 _initialized_indy_entries.push(ResolvedIndyEntry((u2)resolved_index, (u2)cp_index));
287 } else {
288 // Should do nothing since we are not patching this bytecode
289 int cache_index = ConstantPool::decode_invokedynamic_index(
290 Bytes::get_native_u4(p));
291 int cp_index = _initialized_indy_entries.at(cache_index).constant_pool_index();
292 assert(_pool->tag_at(cp_index).is_invoke_dynamic(), "wrong index");
293 // zero out 4 bytes
294 Bytes::put_Java_u4(p, 0);
295 Bytes::put_Java_u2(p, (u2)cp_index);
296 }
297 }
298
299 // Rewrite some ldc bytecodes to _fast_aldc
300 void Rewriter::maybe_rewrite_ldc(address bcp, int offset, bool is_wide,
301 bool reverse) {
302 if (!reverse) {
303 assert((*bcp) == (is_wide ? Bytecodes::_ldc_w : Bytecodes::_ldc), "not ldc bytecode");
304 address p = bcp + offset;
305 int cp_index = is_wide ? Bytes::get_Java_u2(p) : (u1)(*p);
306 constantTag tag = _pool->tag_at(cp_index).value();
307
308 if (tag.is_method_handle() ||
309 tag.is_method_type() ||
310 tag.is_string() ||
311 (tag.is_dynamic_constant() &&
312 // keep regular ldc interpreter logic for condy primitives
313 is_reference_type(Signature::basic_type(_pool->uncached_signature_ref_at(cp_index))))
314 ) {
315 int ref_index = cp_entry_to_resolved_references(cp_index);
316 if (is_wide) {
317 (*bcp) = Bytecodes::_fast_aldc_w;
318 assert(ref_index == (u2)ref_index, "index overflow");
319 Bytes::put_native_u2(p, (u2)ref_index);
320 } else {
321 (*bcp) = Bytecodes::_fast_aldc;
322 assert(ref_index == (u1)ref_index, "index overflow");
323 (*p) = (u1)ref_index;
324 }
325 }
326 } else {
327 Bytecodes::Code rewritten_bc =
328 (is_wide ? Bytecodes::_fast_aldc_w : Bytecodes::_fast_aldc);
329 if ((*bcp) == rewritten_bc) {
330 address p = bcp + offset;
331 int ref_index = is_wide ? Bytes::get_native_u2(p) : (u1)(*p);
332 int pool_index = resolved_references_entry_to_pool_index(ref_index);
333 if (is_wide) {
334 (*bcp) = Bytecodes::_ldc_w;
335 assert(pool_index == (u2)pool_index, "index overflow");
336 Bytes::put_Java_u2(p, (u2)pool_index);
337 } else {
338 (*bcp) = Bytecodes::_ldc;
339 assert(pool_index == (u1)pool_index, "index overflow");
340 (*p) = (u1)pool_index;
341 }
342 }
343 }
344 }
345
346
347 // Rewrites a method given the index_map information
348 void Rewriter::scan_method(Thread* thread, Method* method, bool reverse, bool* invokespecial_error) {
349
350 int nof_jsrs = 0;
351 bool has_monitor_bytecodes = false;
352 Bytecodes::Code c;
353
354 // Bytecodes and their length
355 const address code_base = method->code_base();
356 const int code_length = method->code_size();
357
358 int bc_length;
359 for (int bci = 0; bci < code_length; bci += bc_length) {
360 address bcp = code_base + bci;
361 int prefix_length = 0;
362 c = (Bytecodes::Code)(*bcp);
363
364 // Since we have the code, see if we can get the length
365 // directly. Some more complicated bytecodes will report
366 // a length of zero, meaning we need to make another method
367 // call to calculate the length.
368 bc_length = Bytecodes::length_for(c);
369 if (bc_length == 0) {
370 bc_length = Bytecodes::length_at(method, bcp);
371
372 // length_at will put us at the bytecode after the one modified
373 // by 'wide'. We don't currently examine any of the bytecodes
374 // modified by wide, but in case we do in the future...
375 if (c == Bytecodes::_wide) {
376 prefix_length = 1;
377 c = (Bytecodes::Code)bcp[1];
378 }
379 }
380
381 // Continuing with an invalid bytecode will fail in the loop below.
382 // So guarantee here.
383 guarantee(bc_length > 0, "Verifier should have caught this invalid bytecode");
384
385 switch (c) {
386 case Bytecodes::_lookupswitch : {
387 #ifndef ZERO
388 Bytecode_lookupswitch bc(method, bcp);
389 (*bcp) = (
390 bc.number_of_pairs() < BinarySwitchThreshold
391 ? Bytecodes::_fast_linearswitch
392 : Bytecodes::_fast_binaryswitch
393 );
394 #endif
395 break;
396 }
397 case Bytecodes::_fast_linearswitch:
398 case Bytecodes::_fast_binaryswitch: {
399 #ifndef ZERO
400 (*bcp) = Bytecodes::_lookupswitch;
401 #endif
402 break;
403 }
404
405 case Bytecodes::_invokespecial : {
406 rewrite_invokespecial(bcp, prefix_length+1, reverse, invokespecial_error);
407 break;
408 }
409
410 case Bytecodes::_putstatic :
411 case Bytecodes::_putfield : {
412 if (!reverse) {
413 // Check if any final field of the class given as parameter is modified
414 // outside of initializer methods of the class. Fields that are modified
415 // are marked with a flag. For marked fields, the compilers do not perform
416 // constant folding (as the field can be changed after initialization).
417 //
418 // The check is performed after verification and only if verification has
419 // succeeded. Therefore, the class is guaranteed to be well-formed.
420 InstanceKlass* klass = method->method_holder();
421 u2 bc_index = Bytes::get_Java_u2(bcp + prefix_length + 1);
422 constantPoolHandle cp(thread, method->constants());
423 Symbol* ref_class_name = cp->klass_name_at(cp->uncached_klass_ref_index_at(bc_index));
424
425 if (klass->name() == ref_class_name) {
426 Symbol* field_name = cp->uncached_name_ref_at(bc_index);
427 Symbol* field_sig = cp->uncached_signature_ref_at(bc_index);
428
429 fieldDescriptor fd;
430 if (klass->find_field(field_name, field_sig, &fd) != nullptr) {
431 if (fd.access_flags().is_final()) {
432 if (fd.access_flags().is_static()) {
433 if (!method->is_static_initializer()) {
434 fd.set_has_initialized_final_update(true);
435 }
436 } else {
437 if (!method->is_object_initializer()) {
438 fd.set_has_initialized_final_update(true);
439 }
440 }
441 }
442 }
443 }
444 }
445 }
446 // fall through
447 case Bytecodes::_getstatic : // fall through
448 case Bytecodes::_getfield : // fall through
449 case Bytecodes::_invokevirtual : // fall through
450 case Bytecodes::_invokestatic :
451 case Bytecodes::_invokeinterface:
452 case Bytecodes::_invokehandle : // if reverse=true
453 rewrite_member_reference(bcp, prefix_length+1, reverse);
454 break;
455 case Bytecodes::_invokedynamic:
456 rewrite_invokedynamic(bcp, prefix_length+1, reverse);
457 break;
458 case Bytecodes::_ldc:
459 case Bytecodes::_fast_aldc: // if reverse=true
460 maybe_rewrite_ldc(bcp, prefix_length+1, false, reverse);
461 break;
462 case Bytecodes::_ldc_w:
463 case Bytecodes::_fast_aldc_w: // if reverse=true
464 maybe_rewrite_ldc(bcp, prefix_length+1, true, reverse);
465 break;
466 case Bytecodes::_jsr : // fall through
467 case Bytecodes::_jsr_w : nof_jsrs++; break;
468 case Bytecodes::_monitorenter : // fall through
469 case Bytecodes::_monitorexit : has_monitor_bytecodes = true; break;
470
471 default: break;
472 }
473 }
474
475 // Update flags
476 if (has_monitor_bytecodes) {
477 method->set_has_monitor_bytecodes();
478 }
479
480 // The present of a jsr bytecode implies that the method might potentially
481 // have to be rewritten, so we run the oopMapGenerator on the method
482 if (nof_jsrs > 0) {
483 method->set_has_jsrs();
484 }
485 }
486
487 // After constant pool is created, revisit methods containing jsrs.
488 methodHandle Rewriter::rewrite_jsrs(const methodHandle& method, TRAPS) {
489 ResourceMark rm(THREAD);
490 ResolveOopMapConflicts romc(method);
491 methodHandle new_method = romc.do_potential_rewrite(CHECK_(methodHandle()));
492 // Update monitor matching info.
493 if (romc.monitor_safe()) {
494 new_method->set_guaranteed_monitor_matching();
495 }
496
497 return new_method;
498 }
499
500 void Rewriter::rewrite_bytecodes(TRAPS) {
501 assert(_pool->cache() == nullptr, "constant pool cache must not be set yet");
502
503 // determine index maps for Method* rewriting
504 compute_index_maps();
505
506 if (RegisterFinalizersAtInit && _klass->name() == vmSymbols::java_lang_Object()) {
507 bool did_rewrite = false;
508 int i = _methods->length();
509 while (i-- > 0) {
510 Method* method = _methods->at(i);
511 if (method->intrinsic_id() == vmIntrinsics::_Object_init) {
512 // rewrite the return bytecodes of Object.<init> to register the
513 // object for finalization if needed.
514 methodHandle m(THREAD, method);
515 rewrite_Object_init(m, CHECK);
516 did_rewrite = true;
517 break;
518 }
519 }
520 assert(did_rewrite, "must find Object::<init> to rewrite it");
521 }
522
523 // rewrite methods, in two passes
524 int len = _methods->length();
525 bool invokespecial_error = false;
526
527 for (int i = len-1; i >= 0; i--) {
528 Method* method = _methods->at(i);
529 scan_method(THREAD, method, false, &invokespecial_error);
530 if (invokespecial_error) {
531 // If you get an error here, there is no reversing bytecodes
532 // This exception is stored for this class and no further attempt is
533 // made at verifying or rewriting.
534 THROW_MSG(vmSymbols::java_lang_InternalError(),
535 "This classfile overflows invokespecial for interfaces "
536 "and cannot be loaded");
537 return;
538 }
539 }
540 }
541
542 void Rewriter::rewrite(InstanceKlass* klass, TRAPS) {
543 #if INCLUDE_CDS
544 if (klass->is_shared()) {
545 assert(!klass->is_rewritten(), "rewritten shared classes cannot be rewritten again");
546 }
547 #endif // INCLUDE_CDS
548 ResourceMark rm(THREAD);
549 constantPoolHandle cpool(THREAD, klass->constants());
550 Rewriter rw(klass, cpool, klass->methods(), CHECK);
551 // (That's all, folks.)
552 }
553
554 Rewriter::Rewriter(InstanceKlass* klass, const constantPoolHandle& cpool, Array<Method*>* methods, TRAPS)
555 : _klass(klass),
556 _pool(cpool),
557 _methods(methods),
558 _cp_map(cpool->length()),
559 _cp_cache_map(cpool->length() / 2),
560 _reference_map(cpool->length()),
561 _resolved_references_map(cpool->length() / 2),
562 _invokedynamic_references_map(cpool->length() / 2),
563 _method_handle_invokers(cpool->length()),
564 _invokedynamic_index(0)
565 {
566
567 // Rewrite bytecodes - exception here exits.
568 rewrite_bytecodes(CHECK);
569
570 // Stress restoring bytecodes
571 if (StressRewriter) {
572 restore_bytecodes(THREAD);
573 rewrite_bytecodes(CHECK);
574 }
575
576 // allocate constant pool cache, now that we've seen all the bytecodes
577 make_constant_pool_cache(THREAD);
578
579 // Restore bytecodes to their unrewritten state if there are exceptions
580 // rewriting bytecodes or allocating the cpCache
581 if (HAS_PENDING_EXCEPTION) {
582 restore_bytecodes(THREAD);
583 return;
584 }
585
586 // Relocate after everything, but still do this under the is_rewritten flag,
587 // so methods with jsrs in custom class lists in aren't attempted to be
588 // rewritten in the RO section of the shared archive.
589 // Relocated bytecodes don't have to be restored, only the cp cache entries
590 int len = _methods->length();
591 for (int i = len-1; i >= 0; i--) {
592 methodHandle m(THREAD, _methods->at(i));
593
594 if (m->has_jsrs()) {
595 m = rewrite_jsrs(m, THREAD);
596 // Restore bytecodes to their unrewritten state if there are exceptions
597 // relocating bytecodes. If some are relocated, that is ok because that
598 // doesn't affect constant pool to cpCache rewriting.
599 if (HAS_PENDING_EXCEPTION) {
600 restore_bytecodes(THREAD);
601 return;
602 }
603 // Method might have gotten rewritten.
604 methods->at_put(i, m());
605 }
606 }
607 }