From 315848246657607d5acd9bca29d64d98a4c5f042 Mon Sep 17 00:00:00 2001 From: Martin Jambor Date: Fri, 2 Oct 2020 18:41:35 +0200 Subject: [PATCH] ipa-cp: Separate and increase the large-unit parameter A previous patch in the series has taught IPA-CP to identify the important cloning opportunities in 548.exchange2_r as worthwhile on their own, but the optimization is still prevented from taking place because of the overall unit-growh limit. This patches raises that limit so that it takes place and the benchmark runs 30% faster (on AMD Zen2 CPU at least). Before this patch, IPA-CP uses the following formulae to arrive at the overall_size limit: base = MAX(orig_size, param_large_unit_insns) unit_growth_limit = base + base * param_ipa_cp_unit_growth / 100 since param_ipa_cp_unit_growth has default 10, param_large_unit_insns has default value 10000. The problem with exchange2 (at least on zen2 but I have had a quick look on aarch64 too) is that the original estimated unit size is 10513 and so param_large_unit_insns does not apply and the default limit is therefore 11564 which is good enough only for one of the ideal 8 clonings, we need the limit to be at least 16291. I would like to raise param_ipa_cp_unit_growth a little bit more soon too, but most certainly not to 55. Therefore, the large_unit must be increased. In this patch, I decided to decouple the inlining and ipa-cp large-unit parameters. It also makes sense because IPA-CP uses it only at -O3 while inlining also at -O2 (IIUC). But if we agree we can try raising param_large_unit_insns to 13-14 thousand "instructions," perhaps it is not necessary. But then again, it may make sense to actually increase the IPA-CP limit further. I plan to experiment with IPA-CP tuning on a larger set of programs. Meanwhile, mainly to address the 548.exchange2_r regression, I'm suggesting this simple change. gcc/ChangeLog: 2020-09-07 Martin Jambor * params.opt (ipa-cp-large-unit-insns): New parameter. * ipa-cp.c (get_max_overall_size): Use the new parameter. --- gcc/ipa-cp.c | 2 +- gcc/params.opt | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c index 12acf24c553..2152f9e5876 100644 --- a/gcc/ipa-cp.c +++ b/gcc/ipa-cp.c @@ -3448,7 +3448,7 @@ static long get_max_overall_size (cgraph_node *node) { long max_new_size = orig_overall_size; - long large_unit = opt_for_fn (node->decl, param_large_unit_insns); + long large_unit = opt_for_fn (node->decl, param_ipa_cp_large_unit_insns); if (max_new_size < large_unit) max_new_size = large_unit; int unit_growth = opt_for_fn (node->decl, param_ipa_cp_unit_growth); diff --git a/gcc/params.opt b/gcc/params.opt index c0b94bbb96c..6f308a10da0 100644 --- a/gcc/params.opt +++ b/gcc/params.opt @@ -214,6 +214,10 @@ Percentage penalty functions containing a single call to another function will r Common Joined UInteger Var(param_ipa_cp_unit_growth) Init(10) Param Optimization How much can given compilation unit grow because of the interprocedural constant propagation (in percent). +-param=ipa-cp-large-unit-insns= +Common Joined UInteger Var(param_ipa_cp_large_unit_insns) Optimization Init(16000) Param +The size of translation unit that IPA-CP pass considers large. + -param=ipa-cp-value-list-size= Common Joined UInteger Var(param_ipa_cp_value_list_size) Init(8) Param Optimization Maximum size of a list of values associated with each parameter for interprocedural constant propagation. -- 2.30.2