Re: Question on patch -fprofile-partial-training

["Martin Liška" <mliska@suse.cz>]

On 5/3/23 21:10, Qing Zhao via Gcc-patches wrote:
> Hi, Jan,
> 
> You added the following patch into gcc10:
> 
> From 34fbe3f0946f88828765184ed6581bda62cdf49f Mon Sep 17 00:00:00 2001
> From: Jan Hubicka <hubicka@ucw.cz>
> Date: Thu, 5 Dec 2019 19:12:51 +0100
> Subject: [PATCH] cgraphclones.c (localize_profile): New function.
> 
>         * cgraphclones.c (localize_profile): New function.
>         (cgraph_node::create_clone): Use it for partial profiles.
>         * common.opt (fprofile-partial-training): New flag.
>         * doc/invoke.texi (-fprofile-partial-training): Document.
>         * ipa-cp.c (update_profiling_info): For partial profiles do not
>         set function profile to zero.
>         * profile.c (compute_branch_probabilities): With partial profile
>         watch if edge count is zero and turn all probabilities to guessed.
>         (compute_branch_probabilities): For partial profiles do not apply
>         profile when entry count is zero.
>         * tree-profile.c (tree_profiling): Only do value_profile_transformations
>         when profile is read.
> 
> My question is:

Hello.

Why would anybody backport such change to unsupported code-stream of GCC 8?
Generally speaking, I discourage from doing that.

Martin

> 
> Can this patch be back ported to GCC8 easily? I am wondering any significant
> Change between GCC8 and GCC10 that might make the backporting very hard> 
> Thanks a lot for your help.
> 
> Qing