re PR middle-end/38729 (long time needed in tree canonical iv)

2009-06-21  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/38729
	* tree-ssa-loop-niter.c (find_loop_niter_by_eval): Restrict
	to loops with a single exit if -fno-expensive-optimizations.

From-SVN: r148761

gcc/ChangeLog

+2009-06-21  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38729
+	* tree-ssa-loop-niter.c (find_loop_niter_by_eval): Restrict
+	to loops with a single exit if -fno-expensive-optimizations.
+
 2009-06-21  Jakub Jelinek  <jakub@redhat.com>
 
 	* var-tracking.c (struct shared_hash_def, shared_hash): New types.

gcc/tree-ssa-loop-niter.c

@@ -2254,6 +2254,12 @@ find_loop_niter_by_eval (struct loop *loop, edge *exit)
   tree niter = NULL_TREE, aniter;
 
   *exit = NULL;
+
+  /* Loops with multiple exits are expensive to handle and less important.  */
+  if (!flag_expensive_optimizations
+      && VEC_length (edge, exits) > 1)
+    return chrec_dont_know;
+
   for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
     {
       if (!just_once_each_iteration_p (loop, ex->src))