[gcc r11-3810] More consistently split SLP groups

[gcc r11-3810] More consistently split SLP groups

[Richard Biener]

https://gcc.gnu.org/g:6d42d1e223deaf866062e11bd51ee99441ad8871

commit r11-3810-g6d42d1e223deaf866062e11bd51ee99441ad8871
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Oct 12 09:31:16 2020 +0200

    More consistently split SLP groups
    
    This appropriately makes matches all true after successful SLP discovery
    to reliably succeed splitting.  We were picking up an eventual all
    false built-up from scalars state in some cases.
    
    2020-10-12  Richard Biener  <rguenther@suse.de>
    
            * tree-vect-slp.c (vect_analyze_slp_instance): Set matches to true
            after successful discovery but forced split.

Diff:
---
 gcc/tree-vect-slp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index 495fb970e24..dd2042a4db5 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -2283,7 +2283,7 @@ vect_analyze_slp_instance (vec_info *vinfo,
 	    dump_printf_loc (MSG_NOTE, vect_location,
 			     "SLP discovery succeeded but node needs "
 			     "splitting\n");
-	  matches[0] = true;
+	  memset (matches, true, group_size);
 	  matches[group_size / const_max_nunits * const_max_nunits] = false;
 	  vect_free_slp_tree (node);
 	}