[gcc(refs/users/rguenth/heads/vect-force-slp)] Handle unused-only-live stmts in SLP discovery

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:d0b1eaaf0ba4b9e6fd2b18ef597bde3eb7bd018b

commit d0b1eaaf0ba4b9e6fd2b18ef597bde3eb7bd018b
Author: Richard Biener <rguent...@suse.de>
Date:   Thu Mar 7 15:13:33 2024 +0100

    Handle unused-only-live stmts in SLP discovery
    
    The following adds SLP discovery for roots that are only live but
    otherwise unused.
    
            * tree-vect-slp.cc (vect_analyze_slp): Analyze SLP for live
            but otherwise unused defs.

Diff:
---
 gcc/tree-vect-slp.cc | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 6cc544057115..3138a815da7a 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -3985,6 +3985,40 @@ vect_analyze_slp (vec_info *vinfo, unsigned 
max_tree_size)
              saved_stmts.release ();
            }
        }
+
+      if (param_vect_single_lane_slp != 0)
+       {
+         /* Make sure to vectorize only-live stmts, usually inductions.  */
+         for (edge e : get_loop_exit_edges (LOOP_VINFO_LOOP (loop_vinfo)))
+           for (auto gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);
+                gsi_next (&gsi))
+             {
+               gphi *lc_phi = *gsi;
+               tree def = gimple_phi_arg_def_from_edge (lc_phi, e);
+               stmt_vec_info stmt_info;
+               if (TREE_CODE (def) == SSA_NAME
+                   && !virtual_operand_p (def)
+                   && (stmt_info = loop_vinfo->lookup_def (def))
+                   && STMT_VINFO_RELEVANT (stmt_info) == vect_used_only_live
+                   && STMT_VINFO_LIVE_P (stmt_info)
+                   && (STMT_VINFO_DEF_TYPE (stmt_info) == vect_induction_def
+                       || (STMT_VINFO_DEF_TYPE (stmt_info) == vect_internal_def
+                           && STMT_VINFO_REDUC_IDX (stmt_info) == -1)))
+                 {
+                   vec<stmt_vec_info> stmts;
+                   vec<stmt_vec_info> roots = vNULL;
+                   vec<tree> remain = vNULL;
+                   stmts.create (1);
+                   stmts.quick_push (vect_stmt_to_vectorize (stmt_info));
+                   bool res = vect_build_slp_instance (vinfo,
+                                                       
slp_inst_kind_reduc_group,
+                                                       stmts, roots, remain,
+                                                       max_tree_size, &limit,
+                                                       bst_map, NULL);
+                   gcc_assert (res);
+                 }
+             }
+       }
     }
 
   hash_set<slp_tree> visited_patterns;