1 /*
  2  * Copyright (c) 2015, 2021, 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 "code/compiledIC.hpp"
 27 #include "code/compiledMethod.inline.hpp"
 28 #include "code/exceptionHandlerTable.hpp"
 29 #include "code/scopeDesc.hpp"
 30 #include "code/codeCache.hpp"
 31 #include "code/icBuffer.hpp"
 32 #include "gc/shared/barrierSet.hpp"
 33 #include "gc/shared/barrierSetNMethod.hpp"
 34 #include "gc/shared/gcBehaviours.hpp"
 35 #include "interpreter/bytecode.inline.hpp"
 36 #include "logging/log.hpp"
 37 #include "logging/logTag.hpp"
 38 #include "memory/resourceArea.hpp"
 39 #include "oops/compiledICHolder.inline.hpp"
 40 #include "oops/klass.inline.hpp"
 41 #include "oops/methodData.hpp"
 42 #include "oops/method.inline.hpp"
 43 #include "oops/weakHandle.inline.hpp"
 44 #include "prims/methodHandles.hpp"
 45 #include "runtime/atomic.hpp"
 46 #include "runtime/deoptimization.hpp"
 47 #include "runtime/frame.inline.hpp"
 48 #include "runtime/jniHandles.inline.hpp"
 49 #include "runtime/handles.inline.hpp"
 50 #include "runtime/mutexLocker.hpp"
 51 #include "runtime/sharedRuntime.hpp"
 52 
 53 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, const CodeBlobLayout& layout,
 54                                int frame_complete_offset, int frame_size, ImmutableOopMapSet* oop_maps,
 55                                bool caller_must_gc_arguments, bool compiled)
 56   : CodeBlob(name, type, layout, frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments, compiled),
 57     _mark_for_deoptimization_status(not_marked),
 58     _method(method),
 59     _gc_data(NULL)
 60 {
 61   init_defaults();
 62 }
 63 
 64 CompiledMethod::CompiledMethod(Method* method, const char* name, CompilerType type, int size,
 65                                int header_size, CodeBuffer* cb, int frame_complete_offset, int frame_size,
 66                                OopMapSet* oop_maps, bool caller_must_gc_arguments, bool compiled)
 67   : CodeBlob(name, type, CodeBlobLayout((address) this, size, header_size, cb), cb,
 68              frame_complete_offset, frame_size, oop_maps, caller_must_gc_arguments, compiled),
 69     _mark_for_deoptimization_status(not_marked),
 70     _method(method),
 71     _gc_data(NULL)
 72 {
 73   init_defaults();
 74 }
 75 
 76 void CompiledMethod::init_defaults() {
 77   { // avoid uninitialized fields, even for short time periods
 78     _scopes_data_begin          = NULL;
 79     _deopt_handler_begin        = NULL;
 80     _deopt_mh_handler_begin     = NULL;
 81     _exception_cache            = NULL;
 82   }
 83   _has_unsafe_access          = 0;
 84   _has_method_handle_invokes  = 0;
 85   _has_wide_vectors           = 0;
 86   _has_monitors               = 0;
 87 }
 88 
 89 bool CompiledMethod::is_method_handle_return(address return_pc) {
 90   if (!has_method_handle_invokes())  return false;
 91   PcDesc* pd = pc_desc_at(return_pc);
 92   if (pd == NULL)
 93     return false;
 94   return pd->is_method_handle_invoke();
 95 }
 96 
 97 // Returns a string version of the method state.
 98 const char* CompiledMethod::state() const {
 99   int state = get_state();
100   switch (state) {
101   case not_installed:
102     return "not installed";
103   case in_use:
104     return "in use";
105   case not_used:
106     return "not_used";
107   case not_entrant:
108     return "not_entrant";
109   case zombie:
110     return "zombie";
111   case unloaded:
112     return "unloaded";
113   default:
114     fatal("unexpected method state: %d", state);
115     return NULL;
116   }
117 }
118 
119 //-----------------------------------------------------------------------------
120 void CompiledMethod::mark_for_deoptimization(bool inc_recompile_counts) {
121   // assert (can_be_deoptimized(), ""); // in some places we check before marking, in others not.
122   MutexLocker ml(CompiledMethod_lock->owned_by_self() ? NULL : CompiledMethod_lock,
123                  Mutex::_no_safepoint_check_flag);
124   if (_mark_for_deoptimization_status != deoptimize_done) { // can't go backwards
125      _mark_for_deoptimization_status = (inc_recompile_counts ? deoptimize : deoptimize_noupdate);
126   }
127 }
128 
129 //-----------------------------------------------------------------------------
130 
131 ExceptionCache* CompiledMethod::exception_cache_acquire() const {
132   return Atomic::load_acquire(&_exception_cache);
133 }
134 
135 void CompiledMethod::add_exception_cache_entry(ExceptionCache* new_entry) {
136   assert(ExceptionCache_lock->owned_by_self(),"Must hold the ExceptionCache_lock");
137   assert(new_entry != NULL,"Must be non null");
138   assert(new_entry->next() == NULL, "Must be null");
139 
140   for (;;) {
141     ExceptionCache *ec = exception_cache();
142     if (ec != NULL) {
143       Klass* ex_klass = ec->exception_type();
144       if (!ex_klass->is_loader_alive()) {
145         // We must guarantee that entries are not inserted with new next pointer
146         // edges to ExceptionCache entries with dead klasses, due to bad interactions
147         // with concurrent ExceptionCache cleanup. Therefore, the inserts roll
148         // the head pointer forward to the first live ExceptionCache, so that the new
149         // next pointers always point at live ExceptionCaches, that are not removed due
150         // to concurrent ExceptionCache cleanup.
151         ExceptionCache* next = ec->next();
152         if (Atomic::cmpxchg(&_exception_cache, ec, next) == ec) {
153           CodeCache::release_exception_cache(ec);
154         }
155         continue;
156       }
157       ec = exception_cache();
158       if (ec != NULL) {
159         new_entry->set_next(ec);
160       }
161     }
162     if (Atomic::cmpxchg(&_exception_cache, ec, new_entry) == ec) {
163       return;
164     }
165   }
166 }
167 
168 void CompiledMethod::clean_exception_cache() {
169   // For each nmethod, only a single thread may call this cleanup function
170   // at the same time, whether called in STW cleanup or concurrent cleanup.
171   // Note that if the GC is processing exception cache cleaning in a concurrent phase,
172   // then a single writer may contend with cleaning up the head pointer to the
173   // first ExceptionCache node that has a Klass* that is alive. That is fine,
174   // as long as there is no concurrent cleanup of next pointers from concurrent writers.
175   // And the concurrent writers do not clean up next pointers, only the head.
176   // Also note that concurent readers will walk through Klass* pointers that are not
177   // alive. That does not cause ABA problems, because Klass* is deleted after
178   // a handshake with all threads, after all stale ExceptionCaches have been
179   // unlinked. That is also when the CodeCache::exception_cache_purge_list()
180   // is deleted, with all ExceptionCache entries that were cleaned concurrently.
181   // That similarly implies that CAS operations on ExceptionCache entries do not
182   // suffer from ABA problems as unlinking and deletion is separated by a global
183   // handshake operation.
184   ExceptionCache* prev = NULL;
185   ExceptionCache* curr = exception_cache_acquire();
186 
187   while (curr != NULL) {
188     ExceptionCache* next = curr->next();
189 
190     if (!curr->exception_type()->is_loader_alive()) {
191       if (prev == NULL) {
192         // Try to clean head; this is contended by concurrent inserts, that
193         // both lazily clean the head, and insert entries at the head. If
194         // the CAS fails, the operation is restarted.
195         if (Atomic::cmpxchg(&_exception_cache, curr, next) != curr) {
196           prev = NULL;
197           curr = exception_cache_acquire();
198           continue;
199         }
200       } else {
201         // It is impossible to during cleanup connect the next pointer to
202         // an ExceptionCache that has not been published before a safepoint
203         // prior to the cleanup. Therefore, release is not required.
204         prev->set_next(next);
205       }
206       // prev stays the same.
207 
208       CodeCache::release_exception_cache(curr);
209     } else {
210       prev = curr;
211     }
212 
213     curr = next;
214   }
215 }
216 
217 // public method for accessing the exception cache
218 // These are the public access methods.
219 address CompiledMethod::handler_for_exception_and_pc(Handle exception, address pc) {
220   // We never grab a lock to read the exception cache, so we may
221   // have false negatives. This is okay, as it can only happen during
222   // the first few exception lookups for a given nmethod.
223   ExceptionCache* ec = exception_cache_acquire();
224   while (ec != NULL) {
225     address ret_val;
226     if ((ret_val = ec->match(exception,pc)) != NULL) {
227       return ret_val;
228     }
229     ec = ec->next();
230   }
231   return NULL;
232 }
233 
234 void CompiledMethod::add_handler_for_exception_and_pc(Handle exception, address pc, address handler) {
235   // There are potential race conditions during exception cache updates, so we
236   // must own the ExceptionCache_lock before doing ANY modifications. Because
237   // we don't lock during reads, it is possible to have several threads attempt
238   // to update the cache with the same data. We need to check for already inserted
239   // copies of the current data before adding it.
240 
241   MutexLocker ml(ExceptionCache_lock);
242   ExceptionCache* target_entry = exception_cache_entry_for_exception(exception);
243 
244   if (target_entry == NULL || !target_entry->add_address_and_handler(pc,handler)) {
245     target_entry = new ExceptionCache(exception,pc,handler);
246     add_exception_cache_entry(target_entry);
247   }
248 }
249 
250 // private method for handling exception cache
251 // These methods are private, and used to manipulate the exception cache
252 // directly.
253 ExceptionCache* CompiledMethod::exception_cache_entry_for_exception(Handle exception) {
254   ExceptionCache* ec = exception_cache_acquire();
255   while (ec != NULL) {
256     if (ec->match_exception_with_space(exception)) {
257       return ec;
258     }
259     ec = ec->next();
260   }
261   return NULL;
262 }
263 
264 //-------------end of code for ExceptionCache--------------
265 
266 bool CompiledMethod::is_at_poll_return(address pc) {
267   RelocIterator iter(this, pc, pc+1);
268   while (iter.next()) {
269     if (iter.type() == relocInfo::poll_return_type)
270       return true;
271   }
272   return false;
273 }
274 
275 
276 bool CompiledMethod::is_at_poll_or_poll_return(address pc) {
277   RelocIterator iter(this, pc, pc+1);
278   while (iter.next()) {
279     relocInfo::relocType t = iter.type();
280     if (t == relocInfo::poll_return_type || t == relocInfo::poll_type)
281       return true;
282   }
283   return false;
284 }
285 
286 void CompiledMethod::verify_oop_relocations() {
287   // Ensure sure that the code matches the current oop values
288   RelocIterator iter(this, NULL, NULL);
289   while (iter.next()) {
290     if (iter.type() == relocInfo::oop_type) {
291       oop_Relocation* reloc = iter.oop_reloc();
292       if (!reloc->oop_is_immediate()) {
293         reloc->verify_oop_relocation();
294       }
295     }
296   }
297 }
298 
299 
300 ScopeDesc* CompiledMethod::scope_desc_at(address pc) {
301   PcDesc* pd = pc_desc_at(pc);
302   guarantee(pd != NULL, "scope must be present");
303   return new ScopeDesc(this, pd);
304 }
305 
306 ScopeDesc* CompiledMethod::scope_desc_near(address pc) {
307   PcDesc* pd = pc_desc_near(pc);
308   guarantee(pd != NULL, "scope must be present");
309   return new ScopeDesc(this, pd);
310 }
311 
312 address CompiledMethod::oops_reloc_begin() const {
313   // If the method is not entrant or zombie then a JMP is plastered over the
314   // first few bytes.  If an oop in the old code was there, that oop
315   // should not get GC'd.  Skip the first few bytes of oops on
316   // not-entrant methods.
317   if (frame_complete_offset() != CodeOffsets::frame_never_safe &&
318       code_begin() + frame_complete_offset() >
319       verified_entry_point() + NativeJump::instruction_size)
320   {
321     // If we have a frame_complete_offset after the native jump, then there
322     // is no point trying to look for oops before that. This is a requirement
323     // for being allowed to scan oops concurrently.
324     return code_begin() + frame_complete_offset();
325   }
326 
327   // It is not safe to read oops concurrently using entry barriers, if their
328   // location depend on whether the nmethod is entrant or not.
329   // assert(BarrierSet::barrier_set()->barrier_set_nmethod() == NULL, "Not safe oop scan");
330 
331   address low_boundary = verified_entry_point();
332   if (!is_in_use() && is_nmethod()) {
333     low_boundary += NativeJump::instruction_size;
334     // %%% Note:  On SPARC we patch only a 4-byte trap, not a full NativeJump.
335     // This means that the low_boundary is going to be a little too high.
336     // This shouldn't matter, since oops of non-entrant methods are never used.
337     // In fact, why are we bothering to look at oops in a non-entrant method??
338   }
339   return low_boundary;
340 }
341 
342 int CompiledMethod::verify_icholder_relocations() {
343   ResourceMark rm;
344   int count = 0;
345 
346   RelocIterator iter(this);
347   while(iter.next()) {
348     if (iter.type() == relocInfo::virtual_call_type) {
349       if (CompiledIC::is_icholder_call_site(iter.virtual_call_reloc(), this)) {
350         CompiledIC *ic = CompiledIC_at(&iter);
351         if (TraceCompiledIC) {
352           tty->print("noticed icholder " INTPTR_FORMAT " ", p2i(ic->cached_icholder()));
353           ic->print();
354         }
355         assert(ic->cached_icholder() != NULL, "must be non-NULL");
356         count++;
357       }
358     }
359   }
360 
361   return count;
362 }
363 
364 // Method that knows how to preserve outgoing arguments at call. This method must be
365 // called with a frame corresponding to a Java invoke
366 void CompiledMethod::preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map, OopClosure* f) {
367   if (method() != NULL) {
368     // handle the case of an anchor explicitly set in continuation code that doesn't have a callee
369     JavaThread* thread = reg_map->thread();
370     if (thread->has_last_Java_frame() && fr.sp() == thread->last_Java_sp()) {
371       // if (!method()->is_native()) fr.print_on(tty);
372       // assert (method()->is_native(), "");
373       return;
374     }
375 
376     if (!method()->is_native()) {
377       address pc = fr.pc();
378       bool has_receiver, has_appendix;
379       Symbol* signature;
380 
381       // The method attached by JIT-compilers should be used, if present.
382       // Bytecode can be inaccurate in such case.
383       Method* callee = attached_method_before_pc(pc);
384       if (callee != NULL) {
385         has_receiver = !(callee->access_flags().is_static());
386         has_appendix = false;
387         signature    = callee->signature();
388       } else {
389         SimpleScopeDesc ssd(this, pc);
390         if (ssd.is_optimized_linkToNative()) return; // call was replaced
391         Bytecode_invoke call(methodHandle(Thread::current(), ssd.method()), ssd.bci());
392         has_receiver = call.has_receiver();
393         has_appendix = call.has_appendix();
394         signature    = call.signature();
395       }
396 
397       fr.oops_compiled_arguments_do(signature, has_receiver, has_appendix, reg_map, f);
398     } else if (method()->is_continuation_enter_intrinsic()) {
399       // This method only calls Continuation.enter()
400       Symbol* signature = vmSymbols::continuationEnter_signature();
401       fr.oops_compiled_arguments_do(signature, false, false, reg_map, f);
402     }
403   }
404 }
405 
406 Method* CompiledMethod::attached_method(address call_instr) {
407   assert(code_contains(call_instr), "not part of the nmethod");
408   RelocIterator iter(this, call_instr, call_instr + 1);
409   while (iter.next()) {
410     if (iter.addr() == call_instr) {
411       switch(iter.type()) {
412         case relocInfo::static_call_type:      return iter.static_call_reloc()->method_value();
413         case relocInfo::opt_virtual_call_type: return iter.opt_virtual_call_reloc()->method_value();
414         case relocInfo::virtual_call_type:     return iter.virtual_call_reloc()->method_value();
415         default:                               break;
416       }
417     }
418   }
419   return NULL; // not found
420 }
421 
422 Method* CompiledMethod::attached_method_before_pc(address pc) {
423   if (NativeCall::is_call_before(pc)) {
424     NativeCall* ncall = nativeCall_before(pc);
425     return attached_method(ncall->instruction_address());
426   }
427   return NULL; // not a call
428 }
429 
430 void CompiledMethod::clear_inline_caches() {
431   assert(SafepointSynchronize::is_at_safepoint(), "cleaning of IC's only allowed at safepoint");
432   if (is_zombie()) {
433     return;
434   }
435 
436   RelocIterator iter(this);
437   while (iter.next()) {
438     iter.reloc()->clear_inline_cache();
439   }
440 }
441 
442 // Clear IC callsites, releasing ICStubs of all compiled ICs
443 // as well as any associated CompiledICHolders.
444 void CompiledMethod::clear_ic_callsites() {
445   assert(CompiledICLocker::is_safe(this), "mt unsafe call");
446   ResourceMark rm;
447   RelocIterator iter(this);
448   while(iter.next()) {
449     if (iter.type() == relocInfo::virtual_call_type) {
450       CompiledIC* ic = CompiledIC_at(&iter);
451       ic->set_to_clean(false);
452     }
453   }
454 }
455 
456 #ifdef ASSERT
457 // Check class_loader is alive for this bit of metadata.
458 class CheckClass : public MetadataClosure {
459   void do_metadata(Metadata* md) {
460     Klass* klass = NULL;
461     if (md->is_klass()) {
462       klass = ((Klass*)md);
463     } else if (md->is_method()) {
464       klass = ((Method*)md)->method_holder();
465     } else if (md->is_methodData()) {
466       klass = ((MethodData*)md)->method()->method_holder();
467     } else {
468       md->print();
469       ShouldNotReachHere();
470     }
471     assert(klass->is_loader_alive(), "must be alive");
472   }
473 };
474 #endif // ASSERT
475 
476 
477 bool CompiledMethod::clean_ic_if_metadata_is_dead(CompiledIC *ic) {
478   if (ic->is_clean()) {
479     return true;
480   }
481   if (ic->is_icholder_call()) {
482     // The only exception is compiledICHolder metdata which may
483     // yet be marked below. (We check this further below).
484     CompiledICHolder* cichk_metdata = ic->cached_icholder();
485 
486     if (cichk_metdata->is_loader_alive()) {
487       return true;
488     }
489   } else {
490     Metadata* ic_metdata = ic->cached_metadata();
491     if (ic_metdata != NULL) {
492       if (ic_metdata->is_klass()) {
493         if (((Klass*)ic_metdata)->is_loader_alive()) {
494           return true;
495         }
496       } else if (ic_metdata->is_method()) {
497         Method* method = (Method*)ic_metdata;
498         assert(!method->is_old(), "old method should have been cleaned");
499         if (method->method_holder()->is_loader_alive()) {
500           return true;
501         }
502       } else {
503         ShouldNotReachHere();
504       }
505     } else {
506       // This inline cache is a megamorphic vtable call. Those ICs never hold
507       // any Metadata and should therefore never be cleaned by this function.
508       return true;
509     }
510   }
511 
512   return ic->set_to_clean();
513 }
514 
515 // Clean references to unloaded nmethods at addr from this one, which is not unloaded.
516 template <class CompiledICorStaticCall>
517 static bool clean_if_nmethod_is_unloaded(CompiledICorStaticCall *ic, address addr, CompiledMethod* from,
518                                          bool clean_all) {
519   // Ok, to lookup references to zombies here
520   CodeBlob *cb = CodeCache::find_blob_unsafe(addr);
521   CompiledMethod* nm = (cb != NULL) ? cb->as_compiled_method_or_null() : NULL;
522   if (nm != NULL) {
523     // Clean inline caches pointing to both zombie and not_entrant methods
524     if (clean_all || !nm->is_in_use() || nm->is_unloading() || (nm->method()->code() != nm)) {
525       // Inline cache cleaning should only be initiated on CompiledMethods that have been
526       // observed to be is_alive(). However, with concurrent code cache unloading, it is
527       // possible that by now, the state has become !is_alive. This can happen in two ways:
528       // 1) It can be racingly flipped to unloaded if the nmethod // being cleaned (from the
529       // sweeper) is_unloading(). This is fine, because if that happens, then the inline
530       // caches have already been cleaned under the same CompiledICLocker that we now hold during
531       // inline cache cleaning, and we will simply walk the inline caches again, and likely not
532       // find much of interest to clean. However, this race prevents us from asserting that the
533       // nmethod is_alive(). The is_unloading() function is completely monotonic; once set due
534       // to an oop dying, it remains set forever until freed. Because of that, all unloaded
535       // nmethods are is_unloading(), but notably, an unloaded nmethod may also subsequently
536       // become zombie (when the sweeper converts it to zombie).
537       // 2) It can be racingly flipped to zombie if the nmethod being cleaned (by the concurrent
538       // GC) cleans a zombie nmethod that is concurrently made zombie by the sweeper. In this
539       // scenario, the sweeper will first transition the nmethod to zombie, and then when
540       // unregistering from the GC, it will wait until the GC is done. The GC will then clean
541       // the inline caches *with IC stubs*, even though no IC stubs are needed. This is fine,
542       // as long as the IC stubs are guaranteed to be released until the next safepoint, where
543       // IC finalization requires live IC stubs to not be associated with zombie nmethods.
544       // This is guaranteed, because the sweeper does not have a single safepoint check until
545       // after it completes the whole transition function; it will wake up after the GC is
546       // done with concurrent code cache cleaning (which blocks out safepoints using the
547       // suspendible threads set), and then call clear_ic_callsites, which will release the
548       // associated IC stubs, before a subsequent safepoint poll can be reached. This
549       // guarantees that the spuriously created IC stubs are released appropriately before
550       // IC finalization in a safepoint gets to run. Therefore, this race is fine. This is also
551       // valid in a scenario where an inline cache of a zombie nmethod gets a spurious IC stub,
552       // and then when cleaning another inline cache, fails to request an IC stub because we
553       // exhausted the IC stub buffer. In this scenario, the GC will request a safepoint after
554       // yielding the suspendible therad set, effectively unblocking safepoints. Before such
555       // a safepoint can be reached, the sweeper similarly has to wake up, clear the IC stubs,
556       // and reach the next safepoint poll, after the whole transition function has completed.
557       // Due to the various races that can cause an nmethod to first be is_alive() and then
558       // racingly become !is_alive(), it is unfortunately not possible to assert the nmethod
559       // is_alive(), !is_unloaded() or !is_zombie() here.
560       if (!ic->set_to_clean(!from->is_unloading())) {
561         return false;
562       }
563       assert(ic->is_clean(), "nmethod " PTR_FORMAT "not clean %s", p2i(from), from->method()->name_and_sig_as_C_string());
564     }
565   }
566   return true;
567 }
568 
569 static bool clean_if_nmethod_is_unloaded(CompiledIC *ic, CompiledMethod* from,
570                                          bool clean_all) {
571   return clean_if_nmethod_is_unloaded(ic, ic->ic_destination(), from, clean_all);
572 }
573 
574 static bool clean_if_nmethod_is_unloaded(CompiledStaticCall *csc, CompiledMethod* from,
575                                          bool clean_all) {
576   return clean_if_nmethod_is_unloaded(csc, csc->destination(), from, clean_all);
577 }
578 
579 // Cleans caches in nmethods that point to either classes that are unloaded
580 // or nmethods that are unloaded.
581 //
582 // Can be called either in parallel by G1 currently or after all
583 // nmethods are unloaded.  Return postponed=true in the parallel case for
584 // inline caches found that point to nmethods that are not yet visited during
585 // the do_unloading walk.
586 bool CompiledMethod::unload_nmethod_caches(bool unloading_occurred) {
587   ResourceMark rm;
588 
589   // Exception cache only needs to be called if unloading occurred
590   if (unloading_occurred) {
591     clean_exception_cache();
592   }
593 
594   if (!cleanup_inline_caches_impl(unloading_occurred, false)) {
595     return false;
596   }
597 
598 #ifdef ASSERT
599   // Check that the metadata embedded in the nmethod is alive
600   CheckClass check_class;
601   metadata_do(&check_class);
602 #endif
603   return true;
604 }
605 
606 void CompiledMethod::run_nmethod_entry_barrier() {
607   BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
608   if (bs_nm != NULL) {
609     // We want to keep an invariant that nmethods found through iterations of a Thread's
610     // nmethods found in safepoints have gone through an entry barrier and are not armed.
611     // By calling this nmethod entry barrier, it plays along and acts
612     // like any other nmethod found on the stack of a thread (fewer surprises).
613     nmethod* nm = as_nmethod_or_null();
614     if (nm != NULL && bs_nm->is_armed(nm)) {
615       bool alive = bs_nm->nmethod_entry_barrier(nm);
616       assert(alive, "should be alive");
617     }
618   }
619 }
620 
621 void CompiledMethod::cleanup_inline_caches(bool clean_all) {
622   for (;;) {
623     ICRefillVerifier ic_refill_verifier;
624     { CompiledICLocker ic_locker(this);
625       if (cleanup_inline_caches_impl(false, clean_all)) {
626         return;
627       }
628     }
629     // Call this nmethod entry barrier from the sweeper.
630     run_nmethod_entry_barrier();
631     InlineCacheBuffer::refill_ic_stubs();
632   }
633 }
634 
635 address* CompiledMethod::orig_pc_addr(const frame* fr) {
636   return (address*) ((address)fr->unextended_sp() + orig_pc_offset());
637 }
638 
639 // Called to clean up after class unloading for live nmethods and from the sweeper
640 // for all methods.
641 bool CompiledMethod::cleanup_inline_caches_impl(bool unloading_occurred, bool clean_all) {
642   assert(CompiledICLocker::is_safe(this), "mt unsafe call");
643   ResourceMark rm;
644 
645   // Find all calls in an nmethod and clear the ones that point to non-entrant,
646   // zombie and unloaded nmethods.
647   RelocIterator iter(this, oops_reloc_begin());
648   bool is_in_static_stub = false;
649   while(iter.next()) {
650 
651     switch (iter.type()) {
652 
653     case relocInfo::virtual_call_type:
654       if (unloading_occurred) {
655         // If class unloading occurred we first clear ICs where the cached metadata
656         // is referring to an unloaded klass or method.
657         if (!clean_ic_if_metadata_is_dead(CompiledIC_at(&iter))) {
658           return false;
659         }
660       }
661 
662       if (!clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all)) {
663         return false;
664       }
665       break;
666 
667     case relocInfo::opt_virtual_call_type:
668       if (!clean_if_nmethod_is_unloaded(CompiledIC_at(&iter), this, clean_all)) {
669         return false;
670       }
671       break;
672 
673     case relocInfo::static_call_type:
674       if (!clean_if_nmethod_is_unloaded(compiledStaticCall_at(iter.reloc()), this, clean_all)) {
675         return false;
676       }
677       break;
678 
679     case relocInfo::static_stub_type: {
680       is_in_static_stub = true;
681       break;
682     }
683 
684     case relocInfo::metadata_type: {
685       // Only the metadata relocations contained in static/opt virtual call stubs
686       // contains the Method* passed to c2i adapters. It is the only metadata
687       // relocation that needs to be walked, as it is the one metadata relocation
688       // that violates the invariant that all metadata relocations have an oop
689       // in the compiled method (due to deferred resolution and code patching).
690 
691       // This causes dead metadata to remain in compiled methods that are not
692       // unloading. Unless these slippery metadata relocations of the static
693       // stubs are at least cleared, subsequent class redefinition operations
694       // will access potentially free memory, and JavaThread execution
695       // concurrent to class unloading may call c2i adapters with dead methods.
696       if (!is_in_static_stub) {
697         // The first metadata relocation after a static stub relocation is the
698         // metadata relocation of the static stub used to pass the Method* to
699         // c2i adapters.
700         continue;
701       }
702       is_in_static_stub = false;
703       if (is_unloading()) {
704         // If the nmethod itself is dying, then it may point at dead metadata.
705         // Nobody should follow that metadata; it is strictly unsafe.
706         continue;
707       }
708       metadata_Relocation* r = iter.metadata_reloc();
709       Metadata* md = r->metadata_value();
710       if (md != NULL && md->is_method()) {
711         Method* method = static_cast<Method*>(md);
712         if (!method->method_holder()->is_loader_alive()) {
713           Atomic::store(r->metadata_addr(), (Method*)NULL);
714 
715           if (!r->metadata_is_immediate()) {
716             r->fix_metadata_relocation();
717           }
718         }
719       }
720       break;
721     }
722 
723     default:
724       break;
725     }
726   }
727 
728   return true;
729 }
730 
731 address CompiledMethod::continuation_for_implicit_exception(address pc, bool for_div0_check) {
732   // Exception happened outside inline-cache check code => we are inside
733   // an active nmethod => use cpc to determine a return address
734   int exception_offset = pc - code_begin();
735   int cont_offset = ImplicitExceptionTable(this).continuation_offset( exception_offset );
736 #ifdef ASSERT
737   if (cont_offset == 0) {
738     Thread* thread = Thread::current();
739     ResourceMark rm(thread);
740     CodeBlob* cb = CodeCache::find_blob(pc);
741     assert(cb != NULL && cb == this, "");
742     ttyLocker ttyl;
743     tty->print_cr("implicit exception happened at " INTPTR_FORMAT, p2i(pc));
744     print();
745     method()->print_codes();
746     print_code();
747     print_pcs();
748   }
749 #endif
750   if (cont_offset == 0) {
751     // Let the normal error handling report the exception
752     return NULL;
753   }
754   if (cont_offset == exception_offset) {
755 #if INCLUDE_JVMCI
756     Deoptimization::DeoptReason deopt_reason = for_div0_check ? Deoptimization::Reason_div0_check : Deoptimization::Reason_null_check;
757     JavaThread *thread = JavaThread::current();
758     thread->set_jvmci_implicit_exception_pc(pc);
759     thread->set_pending_deoptimization(Deoptimization::make_trap_request(deopt_reason,
760                                                                          Deoptimization::Action_reinterpret));
761     return (SharedRuntime::deopt_blob()->implicit_exception_uncommon_trap());
762 #else
763     ShouldNotReachHere();
764 #endif
765   }
766   return code_begin() + cont_offset;
767 }
768 
769 class HasEvolDependency : public MetadataClosure {
770   bool _has_evol_dependency;
771  public:
772   HasEvolDependency() : _has_evol_dependency(false) {}
773   void do_metadata(Metadata* md) {
774     if (md->is_method()) {
775       Method* method = (Method*)md;
776       if (method->is_old()) {
777         _has_evol_dependency = true;
778       }
779     }
780   }
781   bool has_evol_dependency() const { return _has_evol_dependency; }
782 };
783 
784 bool CompiledMethod::has_evol_metadata() {
785   // Check the metadata in relocIter and CompiledIC and also deoptimize
786   // any nmethod that has reference to old methods.
787   HasEvolDependency check_evol;
788   metadata_do(&check_evol);
789   if (check_evol.has_evol_dependency() && log_is_enabled(Debug, redefine, class, nmethod)) {
790     ResourceMark rm;
791     log_debug(redefine, class, nmethod)
792             ("Found evol dependency of nmethod %s.%s(%s) compile_id=%d on in nmethod metadata",
793              _method->method_holder()->external_name(),
794              _method->name()->as_C_string(),
795              _method->signature()->as_C_string(),
796              compile_id());
797   }
798   return check_evol.has_evol_dependency();
799 }