Reland: Preprocess structured stack trace on GC to get rid of code reference.

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 688 matching lines @@
 #ifdef DEBUG
   ReportStatisticsAfterGC();
 #endif  // DEBUG
 
   // Remember the last top pointer so that we can later find out
   // whether we allocated in new space since the last GC.
   new_space_top_after_last_gc_ = new_space()->top();
 }
 
 
+void Heap::PreprocessStackTraces() {
+  if (!weak_stack_trace_list()->IsWeakFixedArray()) return;
+  WeakFixedArray* array = WeakFixedArray::cast(weak_stack_trace_list());
+  int length = array->Length();
+  for (int i = 0; i < length; i++) {
+    if (array->IsEmptySlot(i)) continue;
+    FixedArray* elements = FixedArray::cast(array->Get(i));
+    for (int j = 1; j < elements->length(); j += 4) {
+      Object* maybe_code = elements->get(j + 2);
+      // If GC happens while adding a stack trace to the weak fixed array,
+      // which has been copied into a larger backing store, we may run into
+      // a stack trace that has already been preprocessed. Guard against this.
+      if (!maybe_code->IsCode()) break;
+      Code* code = Code::cast(maybe_code);
+      int offset = Smi::cast(elements->get(j + 3))->value();
+      Address pc = code->address() + offset;
+      int pos = code->SourcePosition(pc);
+      elements->set(j + 2, Smi::FromInt(pos));
+    }
+  }
+  // We must not compact the weak fixed list here, as we may be in the middle
+  // of writing to it, when the GC triggered. Instead, we reset the root value.
+  set_weak_stack_trace_list(Smi::FromInt(0));
+}
+
+
 void Heap::HandleGCRequest() {
   if (incremental_marking()->request_type() ==
       IncrementalMarking::COMPLETE_MARKING) {
     CollectAllGarbage(Heap::kNoGCFlags, "GC interrupt");
     return;
   }
   DCHECK(FLAG_overapproximate_weak_closure);
   if (!incremental_marking()->weak_closure_was_overapproximated()) {
     OverApproximateWeakClosure("GC interrupt");
   }
@@ skipping 546 matching lines @@
   }
 }
 
 
 void Heap::MarkCompactEpilogue() {
   gc_state_ = NOT_IN_GC;
 
   isolate_->counters()->objs_since_last_full()->Set(0);
 
   incremental_marking()->Epilogue();
+
+  PreprocessStackTraces();
 }
 
 
 void Heap::MarkCompactPrologue() {
   // At any old GC clear the keyed lookup cache to enable collection of unused
   // maps.
   isolate_->keyed_lookup_cache()->Clear();
   isolate_->context_slot_cache()->Clear();
   isolate_->descriptor_lookup_cache()->Clear();
   RegExpResultsCache::Clear(string_split_cache());
@@ skipping 1790 matching lines @@
 
   set_materialized_objects(*factory->NewFixedArray(0, TENURED));
 
   // Handling of script id generation is in Factory::NewScript.
   set_last_script_id(Smi::FromInt(v8::UnboundScript::kNoScriptId));
 
   Handle<PropertyCell> cell = factory->NewPropertyCell();
   cell->set_value(Smi::FromInt(Isolate::kArrayProtectorValid));
   set_array_protector(*cell);
 
+  set_weak_stack_trace_list(Smi::FromInt(0));
+
   set_allocation_sites_scratchpad(
       *factory->NewFixedArray(kAllocationSiteScratchpadSize, TENURED));
   InitializeAllocationSitesScratchpad();
 
   // Initialize keyed lookup cache.
   isolate_->keyed_lookup_cache()->Clear();
 
   // Initialize context slot cache.
   isolate_->context_slot_cache()->Clear();
 
@@ skipping 16 matching lines @@
     case kNonMonomorphicCacheRootIndex:
     case kPolymorphicCodeCacheRootIndex:
     case kEmptyScriptRootIndex:
     case kSymbolRegistryRootIndex:
     case kMaterializedObjectsRootIndex:
     case kAllocationSitesScratchpadRootIndex:
     case kMicrotaskQueueRootIndex:
     case kDetachedContextsRootIndex:
     case kWeakObjectToCodeTableRootIndex:
     case kRetainedMapsRootIndex:
+    case kWeakStackTraceListRootIndex:
 // Smi values
 #define SMI_ENTRY(type, name, Name) case k##Name##RootIndex:
       SMI_ROOT_LIST(SMI_ENTRY)
 #undef SMI_ENTRY
     // String table
     case kStringTableRootIndex:
       return true;
 
     default:
       return false;
@@ skipping 3250 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal