Do not dereference handles during relocation.

src/handles-inl.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 73 matching lines @@
   Object* object = *BitCast<T**>(location_);
   if (object->IsSmi()) return true;
   HeapObject* heap_object = HeapObject::cast(object);
   Isolate* isolate = heap_object->GetIsolate();
   Object** handle = reinterpret_cast<Object**>(location_);
   Object** roots_array_start = isolate->heap()->roots_array_start();
   if (roots_array_start <= handle &&
       handle < roots_array_start + Heap::kStrongRootListLength) {
     return true;
   }
+  if (isolate->optimizing_compiler_thread()->IsOptimizerThread() &&
+      !Heap::RelocationLock::IsLockedByOptimizerThread(isolate->heap())) {
+    return false;
+  }
   switch (isolate->HandleDereferenceGuardState()) {
     case HandleDereferenceGuard::ALLOW:
       return true;
     case HandleDereferenceGuard::DISALLOW:
       return false;
     case HandleDereferenceGuard::DISALLOW_DEFERRED:
       // Accessing maps and internalized strings is safe.
       if (heap_object->IsMap()) return true;
       if (heap_object->IsInternalizedString()) return true;
       return allow_deferred || !isolate->IsDeferredHandle(handle);
@@ skipping 109 matching lines @@
 
 HandleDereferenceGuard::~HandleDereferenceGuard() {
   isolate_->SetHandleDereferenceGuardState(old_state_);
 }
 
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_INL_H_