https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87873
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The vectorizer is confused by a LC PHI node with a constant argument. That's
indeed sth that usually doesn't happen.
It's simple to avoid this propagation being done but the question is whether
code should rather deal with this (given I do not remember other code
avoiding this kind of propagation). But then we should amend the LC-SSA
verifier appropriately.
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 43641916d52..d16b7ee2d8e 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -6171,6 +6171,13 @@ process_bb (rpo_elim &avail, basic_block bb,
exits PHIs. */
if (!iterate && eliminate)
FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ bool lc_phi_nodes = false;
+ if (loops_state_satisfies_p (LOOP_CLOSED_SSA)
+ && e->src->loop_father != e->dest->loop_father
+ && flow_loop_nested_p (e->dest->loop_father,
+ e->src->loop_father))
+ lc_phi_nodes = true;
for (gphi_iterator gsi = gsi_start_phis (e->dest);
!gsi_end_p (gsi); gsi_next (&gsi))
{
@@ -6197,9 +6204,12 @@ process_bb (rpo_elim &avail, basic_block bb,
arg);
if (sprime
&& sprime != arg
- && may_propagate_copy (arg, sprime))
+ && may_propagate_copy (arg, sprime)
+ /* Do not substitute constants into LC PHI node arguments. */
+ && (!lc_phi_nodes || TREE_CODE (sprime) == SSA_NAME))
propagate_value (use_p, sprime);
}
+ }
vn_context_bb = NULL;
return todo;
