https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113441
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #9)
> There is a weird costing going on in the PHI nodes though:
>
> m_108 = PHI <m_92(16), m_111(5)> 1 times vector_stmt costs 0 in body
> m_108 = PHI <m_92(16), m_111(5)> 2 times scalar_to_vec costs 0 in prologue
>
> they have collapsed to 0. which can't be right..
Note this is likely because of the backend going wrong.
bool
vectorizable_phi (vec_info *,
stmt_vec_info stmt_info, gimple **vec_stmt,
slp_tree slp_node, stmt_vector_for_cost *cost_vec)
{
..
/* For single-argument PHIs assume coalescing which means zero cost
for the scalar and the vector PHIs. This avoids artificially
favoring the vector path (but may pessimize it in some cases). */
if (gimple_phi_num_args (as_a <gphi *> (stmt_info->stmt)) > 1)
record_stmt_cost (cost_vec, SLP_TREE_NUMBER_OF_VEC_STMTS (slp_node),
vector_stmt, stmt_info, vectype, 0, vect_body);
You could check if we call this with sane values.
