8357525: Default CDS archive becomes non-deterministic after JDK-8305895

Reviewed-by: shade, coleenp

Author: iklam

src/hotspot/share/oops/klass.cpp

@@ -810,10 +810,18 @@ void Klass::remove_unshareable_info() {
   set_class_loader_data(nullptr);
   set_is_shared();
 
-  // FIXME: validation in Klass::hash_secondary_supers() may fail for shared klasses.
-  // Even though the bitmaps always match, the canonical order of elements in the table
-  // is not guaranteed to stay the same (see tie breaker during Robin Hood hashing in Klass::hash_insert).
-  //assert(compute_secondary_supers_bitmap(secondary_supers()) == _secondary_supers_bitmap, "broken table");
+  if (CDSConfig::is_dumping_classic_static_archive()) {
+    // "Classic" static archives are required to have deterministic contents.
+    // The elements in _secondary_supers are addresses in the ArchiveBuilder
+    // output buffer, so they should have deterministic values. If we rehash
+    // _secondary_supers, its elements will appear in a deterministic order.
+    //
+    // Note that the bitmap is guaranteed to be deterministic, regardless of the
+    // actual addresses of the elements in _secondary_supers. So rehashing shouldn't
+    // change it.
+    uintx bitmap = hash_secondary_supers(secondary_supers(), true);
+    assert(bitmap == _secondary_supers_bitmap, "bitmap should not be changed due to rehashing");
+  }
 }
 
 void Klass::remove_java_mirror() {