* tree-ssa-loop-niter.c (compute_estimated_nb_iterations): Fix

	off-by-one error.
	(array_at_struct_end_p): New function.
	(idx_infer_loop_bounds): Use it.
	(estimate_numbers_of_iterations_loop): Export.
	* predict.c (predict_loops): Use estimated_loop_iterations_int.
	Do not use PRED_LOOP_EXIT on exits predicted by # of iterations.
	(tree_estimate_probability): Call record_loop_exits.
	* tree-data-ref.c (get_number_of_iters_for_loop): Replaced by ...
	(estimated_loop_iterations, estimated_loop_iterations_int,
	estimated_loop_iterations_tree): New functions.
	(analyze_siv_subscript_cst_affine,
	compute_overlap_steps_for_affine_1_2,
	analyze_subscript_affine_affine): Use estimated_loop_iterations_int.
	(analyze_miv_subscript): Use estimated_loop_iterations_tree.
	* predict.def (PRED_LOOP_ITERATIONS): Update comment.
	(PRED_LOOP_ITERATIONS_GUESSED): New.
	* cfgloop.c (record_loop_exits): Do nothing if there are no loops.
	* cfgloop.h (estimate_numbers_of_iterations_loop,
	estimated_loop_iterations_int): Declare.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@122316 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 30 insertions, 10 deletions

diff --git a/gcc/predict.c b/gcc/predict.c
index df5d3105953..0e86c527238 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -650,6 +650,10 @@ predict_loops (void)
       for (j = 0; VEC_iterate (edge, exits, j, ex); j++)
 	{
 	  tree niter = NULL;
+	  HOST_WIDE_INT nitercst;
+	  int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
+	  int probability;
+	  enum br_predictor predictor;
 
 	  if (number_of_iterations_exit (loop, ex, &niter_desc, false))
 	    niter = niter_desc.niter;
@@ -658,20 +662,31 @@ predict_loops (void)
 
 	  if (TREE_CODE (niter) == INTEGER_CST)
 	    {
-	      int probability;
-	      int max = PARAM_VALUE (PARAM_MAX_PREDICTED_ITERATIONS);
 	      if (host_integerp (niter, 1)
 		  && compare_tree_int (niter, max-1) == -1)
-		{
-		  HOST_WIDE_INT nitercst = tree_low_cst (niter, 1) + 1;
-		  probability = ((REG_BR_PROB_BASE + nitercst / 2)
-				 / nitercst);
-		}
+		nitercst = tree_low_cst (niter, 1) + 1;
 	      else
-		probability = ((REG_BR_PROB_BASE + max / 2) / max);
+		nitercst = max;
+	      predictor = PRED_LOOP_ITERATIONS;
+	    }
+	  /* If we have just one exit and we can derive some information about
+	     the number of iterations of the loop from the statements inside
+	     the loop, use it to predict this exit.  */
+	  else if (n_exits == 1)
+	    {
+	      nitercst = estimated_loop_iterations_int (loop, false);
+	      if (nitercst < 0)
+		continue;
+	      if (nitercst > max)
+		nitercst = max;
 
-	      predict_edge (ex, PRED_LOOP_ITERATIONS, probability);
+	      predictor = PRED_LOOP_ITERATIONS_GUESSED;
 	    }
+	  else
+	    continue;
+
+	  probability = ((REG_BR_PROB_BASE + nitercst / 2) / nitercst);
+	  predict_edge (ex, predictor, probability);
 	}
       VEC_free (edge, heap, exits);
 
@@ -706,7 +721,11 @@ predict_loops (void)
 
 	  /* Loop exit heuristics - predict an edge exiting the loop if the
 	     conditional has no loop header successors as not taken.  */
-	  if (!header_found)
+	  if (!header_found
+	      /* If we already used more reliable loop exit predictors, do not
+		 bother with PRED_LOOP_EXIT.  */
+	      && !predicted_by_p (bb, PRED_LOOP_ITERATIONS_GUESSED)
+	      && !predicted_by_p (bb, PRED_LOOP_ITERATIONS))
 	    {
 	      /* For loop with many exits we don't want to predict all exits
 	         with the pretty large probability, because if all exits are
@@ -1258,6 +1277,7 @@ tree_estimate_probability (void)
   tree_bb_level_predictions ();
 
   mark_irreducible_loops ();
+  record_loop_exits ();
   if (current_loops)
     predict_loops ();