[PATCH] vect: Do not use grouped gather for single pieces.

[Robin Dapp]

Hi,

Right now, we even use a grouped gather/scatter for single pieces, i.e.
when there is no stride involved.  This patch guards grouped gather
with >= 2 pieces.

Bootstrapped and regtested on x86, power10, and aarch64.
Regtested on riscv64.

Regards
 Robin

gcc/ChangeLog:

        * tree-vect-stmts.cc (vect_use_grouped_gather): Only use when
        there are at least two pieces.
---
 gcc/tree-vect-stmts.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index da87b329715..50a0acb4214 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -1749,7 +1749,7 @@ vect_use_grouped_gather (dr_vec_info *dr_info, tree 
vectype,
   tree tmp;
   unsigned int pieces;
   if (!can_div_trunc_p (TYPE_VECTOR_SUBPARTS (vectype), nelts, &pieces)
-      || !pieces)
+      || pieces <= 1)
     return false;
 
   *pun_vectype = vector_vector_composition_type (vectype, pieces, &tmp, true);
-- 
2.53.0