[PATCH] Avoid costing vector stmts with count == 0

[Richard Biener]

This avoids confusing the backends.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

Richard.

        * tree-vect-slp.cc (vectorizable_bb_reduc_epilogue): Do not
        cost zero remaining scalar stmts.
        (vectorizable_slp_permutation): Do not cost zero actual
        permutations.
        * tree-vect-stmts.cc (vectorizable_load): Likewise.
---
 gcc/tree-vect-slp.cc   | 7 ++++---
 gcc/tree-vect-stmts.cc | 5 +++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/gcc/tree-vect-slp.cc b/gcc/tree-vect-slp.cc
index 6258a8eb53d..59bca1dfce7 100644
--- a/gcc/tree-vect-slp.cc
+++ b/gcc/tree-vect-slp.cc
@@ -8701,8 +8701,9 @@ vectorizable_bb_reduc_epilogue (slp_instance instance,
 
   /* Since we replace all stmts of a possibly longer scalar reduction
      chain account for the extra scalar stmts for that.  */
-  record_stmt_cost (cost_vec, instance->remain_defs.length (), scalar_stmt,
-                   instance->root_stmts[0], 0, vect_body);
+  if (!instance->remain_defs.is_empty ())
+    record_stmt_cost (cost_vec, instance->remain_defs.length (), scalar_stmt,
+                     instance->root_stmts[0], 0, vect_body);
   return true;
 }
 
@@ -11370,7 +11371,7 @@ vectorizable_slp_permutation (vec_info *vinfo, 
gimple_stmt_iterator *gsi,
   if (nperms < 0)
     return false;
 
-  if (!gsi)
+  if (!gsi && nperms != 0)
     record_stmt_cost (cost_vec, nperms, vec_perm, node, vectype, 0, vect_body);
 
   return true;
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index edc669ba3e4..9fcc2fd0849 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -11387,8 +11387,9 @@ vectorizable_load (vec_info *vinfo,
        {
          vect_transform_slp_perm_load (vinfo, slp_node, vNULL, nullptr, vf,
                                        true, &n_perms, nullptr);
-         inside_cost = record_stmt_cost (cost_vec, n_perms, vec_perm,
-                                         slp_node, 0, vect_body);
+         if (n_perms != 0)
+           inside_cost = record_stmt_cost (cost_vec, n_perms, vec_perm,
+                                           slp_node, 0, vect_body);
        }
       else
        {
-- 
2.51.0