src/hotspot/share/classfile/fieldLayoutBuilder.cpp

@@ -559,12 +559,14 @@
             SystemDictionary::resolve_flattenable_field_or_fail(&fs,
                 Handle(THREAD, _cfp->_loader_data->class_loader()),
                 _cfp->_protection_domain, true, CHECK);
         assert(klass != NULL, "Sanity check");
         ValueKlass* vk = ValueKlass::cast(klass);
-        bool flattened = (ValueFieldMaxFlatSize < 0)
+        bool has_flattenable_size = (ValueFieldMaxFlatSize < 0)
                          || (vk->size_helper() * HeapWordSize) <= ValueFieldMaxFlatSize;
+        // volatile fields are currently never flattened, this could change in the future
+        bool flattened = !fs.access_flags().is_volatile() && has_flattenable_size;
         if (flattened) {
           group->add_flattened_field(fs, vk);
           _nonstatic_oopmap_count += vk->nonstatic_oop_map_count();
           fs.set_flattened(true);
         } else {