Comment # 27 on bug 110897 from Richard Thier

This is also always happening:

  434     /* Enable fastfill and/or hiz.
  435      *
  436      * If we cleared zmask/hiz, it's in use now. The Hyper-Z state update
  437      * looks if zmask/hiz is in use and programs hardware accordingly. */
  438     if (r300->zmask_in_use || r300->hiz_in_use) {
  439         r300_mark_atom_dirty(r300, &r300->hyperz_state);
  440     }

So we do get into the body of the if as zmasn_in_use is true here.