Proposal:

[1] SystemDictionaryShared::{_dumptime_table, _dumptime_lambda_proxy_class_dictionary} should be allocated at VM bootstrap to so:

+ We don't need to allocate these tables dynamically
+ We don't need to check if these tables exist when writing the archive

[2] The current implementation guarantees that SystemDictionaryShared::_dumptime_table always contains a DumpTimeClassInfo for each InstanceKlass that's being considered for inclusion in the CDS archive. We can simplify the old SystemDictionaryShared::find_or_allocate_info_for() API to

    // Guaranteed to return non-NULL value for non-shared classes.
    // k must not be a shared class.
    DumpTimeClassInfo* SystemDictionaryShared::get_info(InstanceKlass* k)


=========================================
Background:

The API for SystemDictionaryShared::find_or_allocate_info_for() is too loose and potentially unreliable. By definition, it will allocate a new DumpTimeClassInfo if one doesn't already exist. It's used in places like this:

https://github.com/openjdk/jdk/blob/b1817a30a00d74f70b247c783047bfbb49515dda/src/hotspot/share/classfile/systemDictionaryShared.cpp#L673-L679

bool SystemDictionaryShared::is_excluded_class(InstanceKlass* k) {
  assert(_no_class_loading_should_happen, "sanity");
  assert_lock_strong(DumpTimeTable_lock);
  Arguments::assert_is_dumping_archive();
  DumpTimeClassInfo* p = find_or_allocate_info_for_locked(k);
  return (p == NULL) ? true : p->is_excluded();
}

However, the implementation will not allocate under some circumstances. The behavior depends on many external states, making the code hard to understand:

https://github.com/openjdk/jdk/blob/master/src/hotspot/share/cds/dumpTimeClassInfo.cpp#L172-L190

DumpTimeClassInfo* DumpTimeSharedClassTable::find_or_allocate_info_for(InstanceKlass* k, bool dump_in_progress) {
  bool created = false;
  DumpTimeClassInfo* p;
  if (!dump_in_progress) {
    p = put_if_absent(k, &created);
  } else {
    p = get(k);
  }
  if (created) {
    assert(!SystemDictionaryShared::no_class_loading_should_happen(),
           "no new classes can be loaded while dumping archive");
    p->_klass = k;
  } else {
    if (!dump_in_progress) {
      assert(p->_klass == k, "Sanity");
    }
  }
  return p;
}