re PR tree-optimization/40062 (high memory usage and compile time in SCEV cprop with -O3)

2009-05-08  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/40062
	* tree-scalar-evolution.c (follow_ssa_edge_in_condition_phi):
	Avoid exponential behavior.

From-SVN: r147283

gcc/ChangeLog

+2009-05-08  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/40062
+	* tree-scalar-evolution.c (follow_ssa_edge_in_condition_phi):
+	Avoid exponential behavior.
+
 2009-05-08  Paolo Bonzini  <bonzini@gnu.org>
 
 	PR rtl-optimization/33928

gcc/tree-scalar-evolution.c

@@ -1319,11 +1319,7 @@ follow_ssa_edge_in_condition_phi (struct loop *loop,
 
   *evolution_of_loop = evolution_of_branch;
 
-  /* If the phi node is just a copy, do not increase the limit.  */
   n = gimple_phi_num_args (condition_phi);
-  if (n > 1)
-    limit++;
-
   for (i = 1; i < n; i++)
     {
       /* Quickly give up when the evolution of one of the branches is
@@ -1331,10 +1327,12 @@ follow_ssa_edge_in_condition_phi (struct loop *loop,
       if (*evolution_of_loop == chrec_dont_know)
 	return t_true;
 
+      /* Increase the limit by the PHI argument number to avoid exponential
+	 time and memory complexity.  */
       res = follow_ssa_edge_in_condition_phi_branch (i, loop, condition_phi,
 						     halting_phi,
 						     &evolution_of_branch,
-						     init, limit);
+						     init, limit + i);
       if (res == t_false || res == t_dont_know)
 	return res;