===================================================================
@@ -628,8 +628,15 @@ compute_dom_fast_query (enum cdi_direction dir)
}
/* The main entry point into this module. DIR is set depending on whether
- we want to compute dominators or postdominators. */
+ we want to compute dominators or postdominators.
+ We try to keep dominance info alive as long as possible (to avoid
+ recomputing it often). It has to be freed with free_dominance_info when CFG
+ transformation makes it invalide.
+
+ post_dominance info is less often used, and should be freed after each use.
+*/
+
void
calculate_dominance_info (enum cdi_direction dir)
{