Re: [PATCH] Support multi-versioning on self-recursive function (ipa/92133)

[Feng Xue OS <fxue@os.amperecomputing.com>]

Have no a complete idea for new cost model, but there are something we can try:
o.  adjust estimated profile for recursive function so that we can get a higher threshold.
o.  introduce a strength level for ipa-cp-clone, by default, it is same as current configuration,
and with larger number, ipa-cp works more aggressively.
o. integrate frequency information to computation of prop_time_benefit.

Feng

________________________________________
From: Jan Hubicka <hubicka@ucw.cz>
Sent: Wednesday, November 27, 2019 10:27 PM
To: Feng Xue OS
Cc: Martin Jambor; Richard Biener; luoxhu; gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Support multi-versioning on self-recursive function (ipa/92133)

> 2019-11-15  Feng Xue <fxue@os.amperecomputing.com>
>
>         PR ipa/92133
>         * doc/invoke.texi (ipa-cp-max-recursive-depth): Document new option.
>         (ipa-cp-min-recursive-probability): Likewise.
>         * params.opt (ipa-cp-max-recursive-depth): New.
>         (ipa-cp-min-recursive-probability): Likewise.
>         * ipa-cp.c (ipcp_lattice<valtype>::add_value): Add two new parameters
>         val_p and unlimited.
>         (self_recursively_generated_p): New function.
>         (get_val_across_arith_op): Likewise.
>         (propagate_vals_across_arith_jfunc): Add constant propagation for
>         self-recursive function.
>         (incorporate_penalties): Do not penalize pure self-recursive function.
>         (good_cloning_opportunity_p): Dump node_is_self_scc flag.
>         (propagate_constants_topo): Set node_is_self_scc flag for cgraph node.
>         (get_info_about_necessary_edges): Relax hotness check for edge to
>         self-recursive function.
>         * ipa-prop.h (ipa_node_params): Add new field node_is_self_scc.

OK, thanks!
do you have some plans on the better cost model for the recursive
cloning? Also it would be nice to have this info available in recursive
inliner and give it a higher priority when inlining is going to turn
previously recrusive call into non-recursive.

Honza