Minor fixes to niter and ivcanon

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
while proofreading niter and ivcanon code I noticed that we give up on exits in inner
loops.  I discussed this with Zdenek and it was done only because at the time
it was implemented we did nothing useful on outer loops.  We can now unloop them, so
I removed the restriction.

I also noticed that not_executed_last_iteration is initialized tice and we can record
realistic upper bound in ivcanon for loop with only one likely exit.

Bootstrapped/regtested x86_64-linux, comitted as obvious.

	* tree-ssa-loop-niter.c (find_loop_niter): Remove just_once_each_iteration_p.
	(maybe_lower_iteration_bound): Initialize not_executed_last_iteration to  NULL
	* tree-ssa-loop-ivcanon.c (canonicalize_loop_induction_variables): Skip
	just_once_each_iteration_p; record estimated bound when loop has only one
	likely exit; test just_once_each_iteration_p before IV canon itself.
	
Index: tree-ssa-loop-niter.c
===================================================================
--- tree-ssa-loop-niter.c	(revision 193155)
+++ tree-ssa-loop-niter.c	(working copy)
@@ -1941,9 +1941,6 @@ find_loop_niter (struct loop *loop, edge
   *exit = NULL;
   FOR_EACH_VEC_ELT (edge, exits, i, ex)
     {
-      if (!just_once_each_iteration_p (loop, ex->src))
-	continue;
-
       if (!number_of_iterations_exit (loop, ex, &desc, false))
 	continue;
 
@@ -3186,7 +3183,7 @@ discover_iteration_bound_by_body_walk (s
 static void
 maybe_lower_iteration_bound (struct loop *loop)
 {
-  pointer_set_t *not_executed_last_iteration = pointer_set_create ();
+  pointer_set_t *not_executed_last_iteration = NULL;
   struct nb_iter_bound *elt;
   bool found_exit = false;
   VEC (basic_block, heap) *queue = NULL;
Index: tree-ssa-loop-ivcanon.c
===================================================================
--- tree-ssa-loop-ivcanon.c	(revision 193155)
+++ tree-ssa-loop-ivcanon.c	(working copy)
@@ -760,11 +760,7 @@ canonicalize_loop_induction_variables (s
 
   niter = number_of_latch_executions (loop);
   if (TREE_CODE (niter) == INTEGER_CST)
-    {
-      exit = single_exit (loop);
-      if (!just_once_each_iteration_p (loop, exit->src))
-	return false;
-    }
+    exit = single_exit (loop);
   else
     {
       /* If the loop has more than one exit, try checking all of them
@@ -785,7 +781,10 @@ canonicalize_loop_induction_variables (s
   /* We work exceptionally hard here to estimate the bound
      by find_loop_niter_by_eval.  Be sure to keep it for future.  */
   if (niter && TREE_CODE (niter) == INTEGER_CST)
-    record_niter_bound (loop, tree_to_double_int (niter), false, true);
+    {
+      record_niter_bound (loop, tree_to_double_int (niter),
+			  exit == single_likely_exit (loop), true);
+    }
 
   /* Force re-computation of loop bounds so we can remove redundant exits.  */
   maxiter = max_loop_iterations_int (loop);
@@ -813,7 +812,8 @@ canonicalize_loop_induction_variables (s
     return true;
 
   if (create_iv
-      && niter && !chrec_contains_undetermined (niter))
+      && niter && !chrec_contains_undetermined (niter)
+      && exit && just_once_each_iteration_p (loop, exit->src))
     create_canonical_iv (loop, exit, niter);
 
   return modified;