diff -r 92383597fa21 -r 1aa9beac610e src/hotspot/share/oops/oop.cpp
--- a/src/hotspot/share/oops/oop.cpp	Thu Oct 04 14:03:13 2018 +0200
+++ b/src/hotspot/share/oops/oop.cpp	Thu Oct 04 16:39:07 2018 +0200
@@ -171,6 +171,63 @@
   return UseCompressedClassPointers;
 }
 
+oop oopDesc::decode_oop_raw(narrowOop narrow_oop) {
+  return (oop)(void*)( (uintptr_t)Universe::narrow_oop_base() +
+                      ((uintptr_t)narrow_oop << Universe::narrow_oop_shift()));
+}
+
+void* oopDesc::load_klass_raw(oop obj) {
+  if (UseCompressedClassPointers) {
+    narrowKlass narrow_klass = *(obj->compressed_klass_addr());
+    if (narrow_klass == 0) return NULL;
+    return (void*)Klass::decode_klass_raw(narrow_klass);
+  } else {
+    return *(void**)(obj->klass_addr());
+  }
+}
+
+void* oopDesc::load_oop_raw(oop obj, int offset) {
+  uintptr_t addr = (uintptr_t)(void*)obj + (uint)offset;
+  if (UseCompressedOops) {
+    narrowOop narrow_oop = *(narrowOop*)addr;
+    if (narrow_oop == 0) return NULL;
+    return (void*)decode_oop_raw(narrow_oop);
+  } else {
+    return *(void**)addr;
+  }
+}
+
+bool oopDesc::is_valid(oop obj) {
+  if (!is_object_aligned(obj)) return false;
+  if ((size_t)(oopDesc*)obj < os::min_page_size()) return false;
+
+  // We need at least the mark and the klass word in the committed region.
+  if (!os::is_readable_range(obj, (oopDesc*)obj + 1)) return false;
+  if (!Universe::heap()->is_in(obj)) return false;
+
+  Klass* k = (Klass*)load_klass_raw(obj);
+
+  if (!os::is_readable_range(k, k + 1)) return false;
+  return MetaspaceUtils::is_range_in_committed(k, k + 1);
+}
+
+oop oopDesc::oop_or_null(address addr) {
+  if (is_valid(oop(addr))) {
+    // We were just given an oop directly.
+    return oop(addr);
+  }
+
+  // Try to find addr using block_start.
+  HeapWord* p = Universe::heap()->block_start(addr);
+  if (p != NULL && Universe::heap()->block_is_obj(p)) {
+    if (!is_valid(oop(p))) return NULL;
+    return oop(p);
+  }
+
+  // If we can't find it it just may mean that heap wasn't parsable.
+  return NULL;
+}
+
 oop oopDesc::obj_field_acquire(int offset) const                      { return HeapAccess<MO_ACQUIRE>::oop_load_at(as_oop(), offset); }
 
 void oopDesc::obj_field_put_raw(int offset, oop value)                { RawAccess<>::oop_store_at(as_oop(), offset, value); }