[gcc r17-3492] Add fixme comment to vect_slp_node_weight and containing_loop

https://gcc.gnu.org/g:de8bbe99481216b1b44ae9cbbbd5057ed5a62506

commit r17-3492-gde8bbe99481216b1b44ae9cbbbd5057ed5a62506
Author: Richard Biener <[email protected]>
Date:   Fri Aug 21 08:41:08 2026 +0200

    Add fixme comment to vect_slp_node_weight and containing_loop
    
    As discussed.
    
            * tree-vect-slp.cc (vect_slp_node_weight): Add comment
            indicating bbs[0] fallback is imprecise.
            (vect_optimize_slp_pass::containing_loop): Likewise.

Diff:
---
 gcc/tree-vect-slp.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index ed0ebad744e1..9dce9208626e 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -350,6 +350,8 @@ vect_slp_node_weight (vec_info *vinfo, slp_tree node)
 {
   stmt_vec_info stmt_info = SLP_TREE_REPRESENTATIVE (node);
   basic_block bb;
+  /* ???  This is imprecise, VEC_PERM nodes do not have a representative
+     but are laid out close to their children.  */
   if (!stmt_info)
     bb = vinfo->bbs[0];
   else
@@ -6774,6 +6776,8 @@ struct loop *
 vect_optimize_slp_pass::containing_loop (slp_tree node)
 {
   stmt_vec_info rep = SLP_TREE_REPRESENTATIVE (node);
+  /* ???  This is imprecise, VEC_PERM nodes do not have a representative
+     but are laid out close to their children.  */
   if (!rep)
     return m_vinfo->bbs[0]->loop_father;
   return gimple_bb (vect_orig_stmt (rep)->stmt)->loop_father;