[gcc r16-5565] vect: Add vect-scalar-cost-multiplier for SLP.

[Robin Dapp]

https://gcc.gnu.org/g:a2f4b0466be29c853c32498ae49c1acfa1594f30

commit r16-5565-ga2f4b0466be29c853c32498ae49c1acfa1594f30
Author: Robin Dapp <rdapp@ventanamicro.com>
Date:   Sun Nov 16 18:43:15 2025 +0100

    vect: Add vect-scalar-cost-multiplier for SLP.
    
    This adds the same vect-scalar-cost-multiplier to SLP costing that loop
    costing already has.
    
    gcc/ChangeLog:
    
            * tree-vect-slp.cc (vect_bb_vectorization_profitable_p):
            Multiply scalar cost by vect-scalar-cost-multiplier.

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

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index fbaff2f7e16c..23098238b124 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -9811,7 +9811,8 @@ vect_bb_vectorization_profitable_p (bb_vec_info bb_vinfo,
       while (si < li_scalar_costs.length ()
 	     && li_scalar_costs[si].first == sl);
       scalar_target_cost_data->finish_cost (nullptr);
-      scalar_cost = scalar_target_cost_data->body_cost ();
+      scalar_cost = (scalar_target_cost_data->body_cost ()
+		     * param_vect_scalar_cost_multiplier) / 100;
 
       /* Complete the target-specific vector cost calculation.  */
       class vector_costs *vect_target_cost_data = init_cost (bb_vinfo, false);