re PR tree-optimization/81303 (410.bwaves regression caused by r249919)

2016-07-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/81303
	* tree-vect-loop.c (vect_estimate_min_profitable_iters): Take
	into account prologue and epilogue iterations when raising
	min_profitable_iters to sth at least covering one vector iteration.

From-SVN: r250416

gcc/ChangeLog

+2016-07-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81303
+	* tree-vect-loop.c (vect_estimate_min_profitable_iters): Take
+	into account prologue and epilogue iterations when raising
+	min_profitable_iters to sth at least covering one vector iteration.
+
 2017-07-21  Tamar Christina  <tamar.christina@arm.com>
 
 	* config/arm/arm.c (arm_test_cpu_arch_dat):

gcc/tree-vect-loop.c

@@ -3702,8 +3702,9 @@ vect_estimate_min_profitable_iters (loop_vec_info loop_vinfo,
 	       "  Calculated minimum iters for profitability: %d\n",
 	       min_profitable_iters);
 
-  min_profitable_iters =
-	min_profitable_iters < vf ? vf : min_profitable_iters;
+  /* We want the vectorized loop to execute at least once.  */
+  if (min_profitable_iters < (vf + peel_iters_prologue + peel_iters_epilogue))
+    min_profitable_iters = vf + peel_iters_prologue + peel_iters_epilogue;
 
   if (dump_enabled_p ())
     dump_printf_loc (MSG_NOTE, vect_location,