When an alias-set is an already existing subset there is no need
to re-record its children as childs of the parent.
I noticed this when doing 1/2 as trivial opportunity to squeeze
back some performance for the non-caching recursion I added. The
whole thing is still quadratic in the depth of the structure, of course.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
Since I'm curious I'll test a variant which checks the children
are actually recorded before pushing this ... (OK, maybe I shouldn't
do this...)
Richard.
2020-01-14 Richard Biener <rguent...@suse.de>
* alias.c (record_alias_subset): Avoid redundant work when
subset is already recorded.
---
gcc/alias.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/gcc/alias.c b/gcc/alias.c
index 9629b5a9f48..3794f9b6a9e 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -1164,10 +1164,16 @@ record_alias_subset (alias_set_type superset,
alias_set_type subset)
superset_entry->has_zero_child = 1;
else
{
- subset_entry = get_alias_set_entry (subset);
if (!superset_entry->children)
superset_entry->children
= hash_map<alias_set_hash, int>::create_ggc (64);
+
+ /* Enter the SUBSET itself as a child of the SUPERSET. If it was
+ already there we're done. */
+ if (superset_entry->children->put (subset, 0))
+ return;
+
+ subset_entry = get_alias_set_entry (subset);
/* If there is an entry for the subset, enter all of its children
(if they are not already present) as children of the SUPERSET. */
if (subset_entry)
@@ -1185,9 +1191,6 @@ record_alias_subset (alias_set_type superset,
alias_set_type subset)
superset_entry->children->put ((*iter).first, (*iter).second);
}
}
-
- /* Enter the SUBSET itself as a child of the SUPERSET. */
- superset_entry->children->put (subset, 0);
}
}
--
2.16.4
