Do not give realistic estimates for loop with array accesses

[Jan Hubicka]

> 
> You are only changing one place in this file.

You are right. I am attaching the updated patch which I am re-testing now.
> 
> The vectorizer already checks this (albeit indirectly):
> 
>   HOST_WIDE_INT max_niter
>     = max_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
>   if ((LOOP_VINFO_NITERS_KNOWN_P (loop_vinfo)
>        && (LOOP_VINFO_INT_NITERS (loop_vinfo) < vectorization_factor))
>       || (max_niter != -1
>           && (unsigned HOST_WIDE_INT) max_niter < vectorization_factor))
>     {
>       if (dump_enabled_p ())
>         dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
>                          "not vectorized: iteration count smaller than "
>                          "vectorization factor.\n");
>       return false;
>     }

Yes, but one tests only vectorization_factor and other min_profitable_estimate
which probably should be greater than vectorization_factor.

The check above should therefore become redundant.  My reading of the code is
that min_profiltable_estimate is computed after the check above, so it is
probably an useful shortcut and the message is also bit more informative.
I updated the later test to use max_niter variable once it is computed.

OK with those changes assuming testing passes?

Honza

	* tree-ssa-loop-niter.c (idx_infer_loop_bounds): We can't get realistic
	estimates here.
	* tree-ssa-loop-unswitch.c (tree_unswitch_single_loop): Use also
	max_loop_iterations_int.
	(tree_unswitch_outer_loop): Likewise.
	* tree-ssa-loop-ivopts.c (avg_loop_niter): Likewise.
	* tree-vect-loop.c (vect_analyze_loop_2): Likewise.
Index: tree-ssa-loop-ivopts.c
===================================================================
--- tree-ssa-loop-ivopts.c	(revision 234516)
+++ tree-ssa-loop-ivopts.c	(working copy)
@@ -121,7 +121,11 @@ avg_loop_niter (struct loop *loop)
 {
   HOST_WIDE_INT niter = estimated_stmt_executions_int (loop);
   if (niter == -1)
-    return AVG_LOOP_NITER (loop);
+    {
+      niter = max_stmt_executions_int (loop);
+      if (niter == -1 || niter > AVG_LOOP_NITER (loop))
+        return AVG_LOOP_NITER (loop);
+    }
 
   return niter;
 }
Index: tree-ssa-loop-niter.c
===================================================================
--- tree-ssa-loop-niter.c	(revision 234516)
+++ tree-ssa-loop-niter.c	(working copy)
@@ -3115,7 +3115,6 @@ idx_infer_loop_bounds (tree base, tree *
   tree low, high, type, next;
   bool sign, upper = true, at_end = false;
   struct loop *loop = data->loop;
-  bool reliable = true;
 
   if (TREE_CODE (base) != ARRAY_REF)
     return true;
@@ -3187,14 +3186,14 @@ idx_infer_loop_bounds (tree base, tree *
       && tree_int_cst_compare (next, high) <= 0)
     return true;
 
-  /* If access is not executed on every iteration, we must ensure that overlow may
-     not make the access valid later.  */
+  /* If access is not executed on every iteration, we must ensure that overlow
+     may not make the access valid later.  */
   if (!dominated_by_p (CDI_DOMINATORS, loop->latch, gimple_bb (data->stmt))
       && scev_probably_wraps_p (initial_condition_in_loop_num (ev, loop->num),
 				step, data->stmt, loop, true))
-    reliable = false;
+    upper = false;
 
-  record_nonwrapping_iv (loop, init, step, data->stmt, low, high, reliable, upper);
+  record_nonwrapping_iv (loop, init, step, data->stmt, low, high, false, upper);
   return true;
 }
 
Index: tree-ssa-loop-unswitch.c
===================================================================
--- tree-ssa-loop-unswitch.c	(revision 234516)
+++ tree-ssa-loop-unswitch.c	(working copy)
@@ -223,6 +223,8 @@ tree_unswitch_single_loop (struct loop *
       /* If the loop is not expected to iterate, there is no need
 	 for unswitching.  */
       iterations = estimated_loop_iterations_int (loop);
+      if (iterations < 0)
+        iterations = max_loop_iterations_int (loop);
       if (iterations >= 0 && iterations <= 1)
 	{
 	  if (dump_file && (dump_flags & TDF_DETAILS))
@@ -439,6 +441,8 @@ tree_unswitch_outer_loop (struct loop *l
   /* If the loop is not expected to iterate, there is no need
       for unswitching.  */
   iterations = estimated_loop_iterations_int (loop);
+  if (iterations < 0)
+    iterations = max_loop_iterations_int (loop);
   if (iterations >= 0 && iterations <= 1)
     {
       if (dump_file && (dump_flags & TDF_DETAILS))
Index: tree-vect-loop.c
===================================================================
--- tree-vect-loop.c	(revision 234516)
+++ tree-vect-loop.c	(working copy)
@@ -2063,6 +2063,8 @@ start_over:
 
   estimated_niter
     = estimated_stmt_executions_int (LOOP_VINFO_LOOP (loop_vinfo));
+  if (estimated_niter != -1)
+    estimated_niter = max_niter;
   if (estimated_niter != -1
       && ((unsigned HOST_WIDE_INT) estimated_niter
           <= MAX (th, (unsigned)min_profitable_estimate)))