------- Comment #2 from rguenth at gcc dot gnu dot org 2009-05-08 09:47 -------
The issue is that with follow_ssa_edge_in_condition_phi we end up with
exponential time and space complexity because we have several PHI nodes
in our chain that have a large number of PHI arguments.
The following fixes it
Index: tree-scalar-evolution.c
===================================================================
--- tree-scalar-evolution.c (revision 147237)
+++ tree-scalar-evolution.c (working copy)
@@ -1320,10 +1320,12 @@ follow_ssa_edge_in_condition_phi (struct
*evolution_of_loop = evolution_of_branch;
- /* If the phi node is just a copy, do not increase the limit. */
+ /* If the phi node is just a copy, do not increase the limit, otherwise
+ increase it by the number of PHI arguments to avoid exponential
+ complexity. */
n = gimple_phi_num_args (condition_phi);
- if (n > 1)
- limit++;
+ limit += n - 1;
+
for (i = 1; i < n; i++)
{
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |spop at gcc dot gnu dot org
Target Milestone|--- |4.3.4
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40062
