[Bug tree-optimization/66510] [6 Regression] gcc.target/arm/pr53636.c FAILs after r224221

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66510

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so we don't limit group sizes to multiples of nunits which means
vect_transform_slp_perm_load misses an early out.  This is then also a missed
optimization as we don't consider the three SLP loads permutes of the single
group load.

Index: gcc/tree-vect-slp.c
===================================================================
--- gcc/tree-vect-slp.c (revision 224514)
+++ gcc/tree-vect-slp.c (working copy)
@@ -3306,6 +3276,10 @@ vect_transform_slp_perm_load (slp_tree n
                      return false;
                    }

+                 if (need_next_vector
+                     && vec_index >= (vf * group_size) / nunits)
+                   return false;
+
                   if (!analyze_only)
                     {
                      int l;