[gcc r15-5338] tree-optimization/117605 - SLP with large negative single-element interleaving

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:4621b684aeb846a682de7e857d67b72eb94f458e

commit r15-5338-g4621b684aeb846a682de7e857d67b72eb94f458e
Author: Richard Biener <rguent...@suse.de>
Date:   Fri Nov 15 09:22:37 2024 +0100

    tree-optimization/117605 - SLP with large negative single-element 
interleaving
    
    We fail to demote this to VMAT_ELEMENTWISE and thus run into the three
    vector permutation limit (and would not consider to use strided loads
    or gathers).
    
    This resolves another bunch of SVE regressions with --param
    vect-force-slp=1
    
            PR tree-optimization/117605
            * tree-vect-stmts.cc (get_group_load_store_type): Also
            apply group size limit for single-element interleaving
            to VMAT_CONTIGUOUS_REVERSE.

Diff:
---
 gcc/tree-vect-stmts.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index f4a4d5a554c2..ab5ea038d1d4 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -2086,8 +2086,9 @@ get_group_load_store_type (vec_info *vinfo, stmt_vec_info 
stmt_info,
             at least create very sub-optimal code in that case (and
             blow up memory, see PR65518).  */
          if (loop_vinfo
-             && *memory_access_type == VMAT_CONTIGUOUS
              && single_element_p
+             && (*memory_access_type == VMAT_CONTIGUOUS
+                 || *memory_access_type == VMAT_CONTIGUOUS_REVERSE)
              && maybe_gt (group_size, TYPE_VECTOR_SUBPARTS (vectype)))
            {
              if (SLP_TREE_LANES (slp_node) == 1)