[PATCH] tree-optimization/101154 - fix out-of bound access in SLP

[Richard Biener]

This fixes an out-of-bound access of matches.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

2021-06-22  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/101154
        * tree-vect-slp.c (vect_build_slp_tree_2): Fix out-of-bound access.
---
 gcc/tree-vect-slp.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
index a32f86b8bc7..b9f91e7c7ba 100644
--- a/gcc/tree-vect-slp.c
+++ b/gcc/tree-vect-slp.c
@@ -1963,15 +1963,15 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
              if (dt == vect_constant_def
                  || dt == vect_external_def)
                {
-               /* We can always build those.  Might want to sort last
-                  or defer building.  */
-                  vec<tree> ops;
-                  ops.create (group_size);
-                  for (lane = 0; lane < group_size; ++lane)
-                    ops.quick_push (chains[lane][n].op);
-                  slp_tree child = vect_create_new_slp_node (ops);
-                  SLP_TREE_DEF_TYPE (child) = dt;
-                  children.safe_push (child);
+                 /* We can always build those.  Might want to sort last
+                    or defer building.  */
+                 vec<tree> ops;
+                 ops.create (group_size);
+                 for (lane = 0; lane < group_size; ++lane)
+                   ops.quick_push (chains[lane][n].op);
+                 slp_tree child = vect_create_new_slp_node (ops);
+                 SLP_TREE_DEF_TYPE (child) = dt;
+                 children.safe_push (child);
                }
              else if (dt != vect_internal_def)
                {
@@ -2036,9 +2036,10 @@ vect_build_slp_tree_2 (vec_info *vinfo, slp_tree node,
                        dump_printf_loc (MSG_NOTE, vect_location,
                                         "failed to match up op %d\n", n);
                      op_stmts.release ();
-                     matches[lane] = false;
                      if (lane != group_size - 1)
                        matches[0] = false;
+                     else
+                       matches[lane] = false;
                      goto out;
                    }
                  if (dump_enabled_p ())
-- 
2.26.2