https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121536
--- Comment #5 from Tamar Christina <tnfchris at gcc dot gnu.org> --- (In reply to rguent...@suse.de from comment #4) > On Thu, 14 Aug 2025, tnfchris at gcc dot gnu.org wrote: > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121536 > > > > --- Comment #3 from Tamar Christina <tnfchris at gcc dot gnu.org> --- > > Richi: g:fb59c5719c17a04ecfd58b5e566eccd6d2ac583a is problematic for us > > because > > without the type we can't tell which one of our scalar register file the > > operation is working on. > > > > e.g. a + b has different costing between int and float. > > > > So we need either the GIMPLE statement of the type of the statement being > > costed otherwise we can't distinguish between them. e.g. just `scalar_stmt` > > does not give us enough information. > > See how x86 solves this issue: > > unsigned > ix86_vector_costs::add_stmt_cost (int count, vect_cost_for_stmt kind, > stmt_vec_info stmt_info, slp_tree node, > tree vectype, int, > vect_cost_model_location where) > { > unsigned retval = 0; > bool scalar_p > = (kind == scalar_stmt || kind == scalar_load || kind == > scalar_store); > int stmt_cost = - 1; > > bool fp = false; > machine_mode mode = scalar_p ? SImode : TImode; > > if (vectype != NULL) > { > fp = FLOAT_TYPE_P (vectype); > mode = TYPE_MODE (vectype); > if (scalar_p) > mode = TYPE_MODE (TREE_TYPE (vectype)); > } > /* When we are costing a scalar stmt use the scalar stmt to get at the > type of the operation. */ > else if (scalar_p && stmt_info) > if (tree lhs = gimple_get_lhs (stmt_info->stmt)) > { > fp = FLOAT_TYPE_P (TREE_TYPE (lhs)); > mode = TYPE_MODE (TREE_TYPE (lhs)); Wrong costing hook, you're looking at the costing hook when comparing vector vs scalar, not the one that sets the initial scalar cost. x86 has the same problem here now: #undef TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST #define TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST \ ix86_builtin_vectorization_cost /* Implement targetm.vectorize.builtin_vectorization_cost. */ static int ix86_builtin_vectorization_cost (enum vect_cost_for_stmt type_of_cost, tree vectype, int) { machine_mode mode = TImode; if (vectype != NULL) mode = TYPE_MODE (vectype); return ix86_default_vector_cost (type_of_cost, mode); } /* Worker for ix86_builtin_vectorization_cost and the fallback calls from ix86_vector_costs::add_stmt_cost. */ static int ix86_default_vector_cost (enum vect_cost_for_stmt type_of_cost, machine_mode mode) { bool fp = FLOAT_MODE_P (mode); int index; switch (type_of_cost) { case scalar_stmt: return fp ? ix86_cost->addss : COSTS_N_INSNS (1); ... so exact same problem, TARGET_VECTORIZE_BUILTIN_VECTORIZATION_COST is no longer able to distinguish between the scalar types.
