[PATCH] tree-optimization/97886 - deal with strange LC PHI nodes

[Richard Biener]

This makes vectorization properly assign vector types to PHI
nodes that copy from externals on loop exit edges.

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

2020-11-18  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/97886
        * tree-vect-loop.c (vectorizable_lc_phi): Properly assign
        vector types to invariants for SLP.
---
 gcc/tree-vect-loop.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index ecaaf0116d3..856bbfebf7c 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -7593,6 +7593,17 @@ vectorizable_lc_phi (loop_vec_info loop_vinfo,
 
   if (!vec_stmt) /* transformation not required.  */
     {
+      /* Deal with copies from externs or constants that disguise as
+        loop-closed PHI nodes (PR97886).  */
+      if (slp_node
+         && !vect_maybe_update_slp_op_vectype (SLP_TREE_CHILDREN (slp_node)[0],
+                                               SLP_TREE_VECTYPE (slp_node)))
+       {
+         if (dump_enabled_p ())
+           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                            "incompatible vector types for invariants\n");
+         return false;
+       }
       STMT_VINFO_TYPE (stmt_info) = lc_phi_info_type;
       return true;
     }
-- 
2.26.2