dump reason for throwing away SLP instance

This adds dumping to vect_slp_analyze_node_alignment when it fails
an SLP instance due to shared vector type conflicts.

2020-10-28  Richard Biener  <rguenther@suse.de>

	* tree-vect-data-refs.c (vect_slp_analyze_node_alignment):
	Dump when vect_update_shared_vectype fails.

diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 4abd27e..fd14b48 100644 (file)
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -2428,7 +2428,13 @@ vect_slp_analyze_node_alignment (vec_info *vinfo, slp_tree node)
   /* We need to commit to a vector type for the group now.  */
   if (is_a <bb_vec_info> (vinfo)
       && !vect_update_shared_vectype (first_stmt_info, SLP_TREE_VECTYPE (node)))
-    return false;
+    {
+      if (dump_enabled_p ())
+       dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                        "desired vector type conflicts with earlier one "
+                        "for %G", first_stmt_info->stmt);
+      return false;
+    }
 
   dr_vec_info *dr_info = STMT_VINFO_DR_INFO (first_stmt_info);
   vect_compute_data_ref_alignment (vinfo, dr_info);