PR rtl-optimization/28071

	* cselib.c (cselib_process_insn): Don't remove useless values too
	often for very large hashtables.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@115777 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4ebe39f..c5c0d6f 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,6 +1,12 @@
 2006-07-27  Jan Hubicka  <jh@suse.cz>
 
        PR rtl-optimization/28071
+       * cselib.c (cselib_process_insn): Don't remove useless values too
+       often for very large hashtables.
+
+2006-07-27  Jan Hubicka  <jh@suse.cz>
+
+       PR rtl-optimization/28071
        * global.c (greg_obstack): New obstack.
        (allocate_bb_info): Use it.
        (free_bb_info): Likewise.

diff --git a/gcc/cselib.c b/gcc/cselib.c
index 0fc8aee..edfc328 100644 (file)
--- a/gcc/cselib.c
+++ b/gcc/cselib.c
@@ -1437,7 +1437,11 @@ cselib_process_insn (rtx insn)
     cselib_current_insn_in_libcall = false;
   cselib_current_insn = 0;
 
-  if (n_useless_values > MAX_USELESS_VALUES)
+  if (n_useless_values > MAX_USELESS_VALUES
+      /* remove_useless_values is linear in the hash table size.  Avoid
+         quadratic behaviour for very large hashtables with very few
+        useless elements.  */
+      && (unsigned int)n_useless_values > cselib_hash_table->n_elements / 4)
     remove_useless_values ();
 }