In practice it seems to be better not to cost a vector induction. The scalar code generally needs the same induction but doesn't cost it, making an apples-for-apples comparison harder. Most inductions also have a low latency and their cost usually gets hidden by other operations.
Like with the previous patches, this one only becomes active if a CPU selects use_new_vector_costs. It should therefore have a very low impact on other CPUs. gcc/ * config/aarch64/aarch64.c (aarch64_detect_vector_stmt_subtype): Assume a zero cost for induction phis. --- gcc/config/aarch64/aarch64.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index e97e71b6e3d..6d18d82079c 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -14541,6 +14541,12 @@ aarch64_detect_vector_stmt_subtype (vec_info *vinfo, vect_cost_for_stmt kind, if (aarch64_sve_mode_p (TYPE_MODE (vectype))) sve_costs = aarch64_tune_params.vec_costs->sve; + /* It's generally better to avoid costing inductions, since the induction + will usually be hidden by other operations. This is particularly true + for things like COND_REDUCTIONS. */ + if (is_a<gphi *> (stmt_info->stmt)) + return 0; + /* Detect cases in which vec_to_scalar is describing the extraction of a vector element in preparation for a scalar store. The store itself is costed separately. */ -- 2.17.1