[backport gcc-4.8/trunk r186566, fixes PR56407 <mikpe@it.uu.se>]

gcc/

2012-04-18  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/44688
	* cfgloop.h (record_niter_bound): Declare.
	* tree-ssa-loop-niter.c (record_niter_bound): Export.
	Update the estimation with the upper bound here...
	(estimate_numbers_of_iterations_loop): ... instead of here.
	Do not forcefully reset a recorded upper bound.
	* tree-vect-loop-manip.c (vect_do_peeling_for_alignment):
	Record the maximum number of loop iterations of the
	prologue loop.

--- gcc-4.7.3/gcc/cfgloop.h.~1~	2012-08-21 15:34:19.000000000 +0200
+++ gcc-4.7.3/gcc/cfgloop.h	2013-05-19 15:54:09.401882878 +0200
@@ -279,6 +279,7 @@ extern unsigned expected_loop_iterations
 extern rtx doloop_condition_get (rtx);
 
 void estimate_numbers_of_iterations_loop (struct loop *, bool);
+void record_niter_bound (struct loop *, double_int, bool, bool);
 HOST_WIDE_INT estimated_loop_iterations_int (struct loop *, bool);
 HOST_WIDE_INT max_stmt_executions_int (struct loop *, bool);
 bool estimated_loop_iterations (struct loop *, bool, double_int *);
--- gcc-4.7.3/gcc/tree-ssa-loop-niter.c.~1~	2012-08-21 15:34:19.000000000 +0200
+++ gcc-4.7.3/gcc/tree-ssa-loop-niter.c	2013-05-19 15:53:05.212044190 +0200
@@ -2498,12 +2498,12 @@ derive_constant_upper_bound_ops (tree ty
    of iterations.  UPPER is true if we are sure the loop iterates at most
    I_BOUND times.  */
 
-static void
+void
 record_niter_bound (struct loop *loop, double_int i_bound, bool realistic,
 		    bool upper)
 {
-  /* Update the bounds only when there is no previous estimation, or when the current
-     estimation is smaller.  */
+  /* Update the bounds only when there is no previous estimation, or when the
+     current estimation is smaller.  */
   if (upper
       && (!loop->any_upper_bound
 	  || double_int_ucmp (i_bound, loop->nb_iterations_upper_bound) < 0))
@@ -2518,6 +2518,14 @@ record_niter_bound (struct loop *loop, d
       loop->any_estimate = true;
       loop->nb_iterations_estimate = i_bound;
     }
+
+  /* If an upper bound is smaller than the realistic estimate of the
+     number of iterations, use the upper bound instead.  */
+  if (loop->any_upper_bound
+      && loop->any_estimate
+      && double_int_ucmp (loop->nb_iterations_upper_bound,
+			  loop->nb_iterations_estimate) < 0)
+    loop->nb_iterations_estimate = loop->nb_iterations_upper_bound;
 }
 
 /* Records that AT_STMT is executed at most BOUND + 1 times in LOOP.  IS_EXIT
@@ -3007,8 +3015,9 @@ estimate_numbers_of_iterations_loop (str
   /* Give up if we already have tried to compute an estimation.  */
   if (loop->estimate_state != EST_NOT_COMPUTED)
     return;
+
   loop->estimate_state = EST_AVAILABLE;
-  loop->any_upper_bound = false;
+  /* Force estimate compuation but leave any existing upper bound in place.  */
   loop->any_estimate = false;
 
   exits = get_loop_exit_edges (loop);
@@ -3040,14 +3049,6 @@ estimate_numbers_of_iterations_loop (str
       bound = gcov_type_to_double_int (nit);
       record_niter_bound (loop, bound, true, false);
     }
-
-  /* If an upper bound is smaller than the realistic estimate of the
-     number of iterations, use the upper bound instead.  */
-  if (loop->any_upper_bound
-      && loop->any_estimate
-      && double_int_ucmp (loop->nb_iterations_upper_bound,
-			  loop->nb_iterations_estimate) < 0)
-    loop->nb_iterations_estimate = loop->nb_iterations_upper_bound;
 }
 
 /* Sets NIT to the estimated number of executions of the latch of the
--- gcc-4.7.3/gcc/tree-vect-loop-manip.c.~1~	2012-08-10 15:21:31.000000000 +0200
+++ gcc-4.7.3/gcc/tree-vect-loop-manip.c	2013-05-19 15:53:05.212044190 +0200
@@ -2170,6 +2170,7 @@ vect_do_peeling_for_alignment (loop_vec_
   struct loop *new_loop;
   unsigned int th = 0;
   int min_profitable_iters;
+  int max_iter;
 
   if (vect_print_dump_info (REPORT_DETAILS))
     fprintf (vect_dump, "=== vect_do_peeling_for_alignment ===");
@@ -2195,6 +2196,11 @@ vect_do_peeling_for_alignment (loop_vec_
 #ifdef ENABLE_CHECKING
   slpeel_verify_cfg_after_peeling (new_loop, loop);
 #endif
+  max_iter = MAX (LOOP_VINFO_VECT_FACTOR (loop_vinfo) - 1, (int) th);
+  record_niter_bound (new_loop, shwi_to_double_int (max_iter), false, true);
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, "Setting upper bound of nb iterations for prologue "
+	     "loop to %d\n", max_iter);
 
   /* Update number of times loop executes.  */
   n_iters = LOOP_VINFO_NITERS (loop_vinfo);