Incremental LTO Project

Incremental LTO Project

[James Hu]

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Hi,

I noticed that adding incremental LTO was a GSoC project that was not
claimed this cycle (
https://summerofcode.withgoogle.com/programs/2023/organizations/gnu-compiler-collection-gcc).
I was curious about working on this project, but wanted to check on the
state of the project. Has it already been completed? Is someone actively
working on it? If not, what would be the appropriate method to contact the
mentor (Jan Hubička)?

Thanks!

Re: Incremental LTO Project

[Thomas Schwinge]

Hi!

On 2023-09-07T19:00:49-0400, James Hu via Gcc <gcc@gcc.gnu.org> wrote:
> I noticed that adding incremental LTO was a GSoC project that was not
> claimed this cycle (
> https://summerofcode.withgoogle.com/programs/2023/organizations/gnu-compiler-collection-gcc).
> I was curious about working on this project, but wanted to check on the
> state of the project.

Thanks for your interest!  (... as a potential contributor, I presume?)

> Has it already been completed? Is someone actively
> working on it?

Yesterday, when browsing the schedule of the GNU Tools Cauldron 2023,
<https://gcc.gnu.org/wiki/cauldron2023>, I noticed there's going to be a
presentation on "Incremental LTO in GCC" (Michal Jireš),
<https://gcc.gnu.org/wiki/cauldron2023#cauldron2023talks.incremental_lto_in_gcc>.

> If not, what would be the appropriate method to contact the
> mentor (Jan Hubička)?

He's reading this list, but I've now also put Honza in CC.


Grüße
 Thomas
-----------------
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Re: Incremental LTO Project

[James Hu]

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Ah, I see. I was interested as a contributor but outside of the official
GSoC program. But I'm assuming that because there is a talk on incremental
LTO, it has already been implemented, correct? Other than that, thanks for
your help!

On Fri, Sep 8, 2023 at 3:20 AM Thomas Schwinge <thomas@codesourcery.com>
wrote:

> Hi!
>
> On 2023-09-07T19:00:49-0400, James Hu via Gcc <gcc@gcc.gnu.org> wrote:
> > I noticed that adding incremental LTO was a GSoC project that was not
> > claimed this cycle (
> >
> https://summerofcode.withgoogle.com/programs/2023/organizations/gnu-compiler-collection-gcc
> ).
> > I was curious about working on this project, but wanted to check on the
> > state of the project.
>
> Thanks for your interest!  (... as a potential contributor, I presume?)
>
> > Has it already been completed? Is someone actively
> > working on it?
>
> Yesterday, when browsing the schedule of the GNU Tools Cauldron 2023,
> <https://gcc.gnu.org/wiki/cauldron2023>, I noticed there's going to be a
> presentation on "Incremental LTO in GCC" (Michal Jireš),
> <
> https://gcc.gnu.org/wiki/cauldron2023#cauldron2023talks.incremental_lto_in_gcc
> >.
>
> > If not, what would be the appropriate method to contact the
> > mentor (Jan Hubička)?
>
> He's reading this list, but I've now also put Honza in CC.
>
>
> Grüße
>  Thomas
> -----------------
> Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201,
> 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer:
> Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München;
> Registergericht München, HRB 106955
>

Re: Incremental LTO Project

[Jan Hubicka]

> Hi!
> 
> On 2023-09-07T19:00:49-0400, James Hu via Gcc <gcc@gcc.gnu.org> wrote:
> > I noticed that adding incremental LTO was a GSoC project that was not
> > claimed this cycle (
> > https://summerofcode.withgoogle.com/programs/2023/organizations/gnu-compiler-collection-gcc).
> > I was curious about working on this project, but wanted to check on the
> > state of the project.
> 
> Thanks for your interest!  (... as a potential contributor, I presume?)
> 
> > Has it already been completed? Is someone actively
> > working on it?
> 
> Yesterday, when browsing the schedule of the GNU Tools Cauldron 2023,
> <https://gcc.gnu.org/wiki/cauldron2023>, I noticed there's going to be a
> presentation on "Incremental LTO in GCC" (Michal Jireš),
> <https://gcc.gnu.org/wiki/cauldron2023#cauldron2023talks.incremental_lto_in_gcc>.

Indeed Michal Jires (who is my student at Charles University) did a lot
of work on incremental LTO.  He is finishing his second bachelor in
physics and then we plan to start working towards contributing it to the
mainline.
His imlementation is described in thesis
https://dspace.cuni.cz/bitstream/handle/20.500.11956/183051/130360194.pdf?sequence=1

This is just a start of the project, further improvemnts will be welcome

Honza
> 
> > If not, what would be the appropriate method to contact the
> > mentor (Jan Hubička)?
> 
> He's reading this list, but I've now also put Honza in CC.
> 
> 
> Grüße
>  Thomas
> -----------------
> Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955

Re: Incremental LTO Project

[Thomas Schwinge]

Hi!

Four things:

On 2023-09-10T23:25:06+0200, Jan Hubicka via Gcc <gcc@gcc.gnu.org> wrote:
>> On 2023-09-07T19:00:49-0400, James Hu via Gcc <gcc@gcc.gnu.org> wrote:
>> > I noticed that adding incremental LTO was a GSoC project that was not
>> > claimed this cycle (
>> > https://summerofcode.withgoogle.com/programs/2023/organizations/gnu-compiler-collection-gcc).
>> > I was curious about working on this project, but wanted to check on the
>> > state of the project.
>>
>> Thanks for your interest!  (... as a potential contributor, I presume?)
>>
>> > Has it already been completed? Is someone actively
>> > working on it?
>>
>> Yesterday, when browsing the schedule of the GNU Tools Cauldron 2023,
>> <https://gcc.gnu.org/wiki/cauldron2023>, I noticed there's going to be a
>> presentation on "Incremental LTO in GCC" (Michal Jireš),
>> <https://gcc.gnu.org/wiki/cauldron2023#cauldron2023talks.incremental_lto_in_gcc>.

1. Was nice to meet you (Honza, Michal) at the Cauldron, attending the
"Incremental LTO in GCC" presentation.  (James: recording should become
available soonish.)

> Indeed Michal Jires (who is my student at Charles University) did a lot
> of work on incremental LTO.  He is finishing his second bachelor in
> physics and then we plan to start working towards contributing it to the
> mainline.

Great!

> His imlementation is described in thesis
> https://dspace.cuni.cz/bitstream/handle/20.500.11956/183051/130360194.pdf?sequence=1

2. Talking to you after the presentation, I had mentioned that I had
failed to understand how the new partitioning scheme works, when reading
Michal's thesis on my way to the Cauldron.  I'm happy to report that upon
re-reading it on my way back home, I then did manage to understand it.
;-)

3. I had suggested that in addition to compilation flags (which you have
covered, per my understanding) also the specific compiler builds should
probably be taken into account (by means of 'cc1' etc. checksums, for
example?), so that the cache doesn't return out-of-date results in that
regard.  Now I had the idea whether we maybe could simply use/modify
'ccache' for that chaching aspect, as it does exactly that: maintain a
persistent cache, with user-configurable size, stale objects pruning,
etc., and takes care that no stale cached objects are returned to the
user.  I've not spent any more detailed thoughts on that, however.

> This is just a start of the project, further improvemnts will be welcome

Which brings us to 4.:

On 2023-09-08T07:26:20-0400, James Hu via Gcc <gcc@gcc.gnu.org> wrote:
> Ah, I see. I was interested as a contributor but outside of the official
> GSoC program. But I'm assuming that because there is a talk on incremental
> LTO, it has already been implemented, correct?

Is there anything that James could work on -- without conflicting with
Michal's ongoing work?  (Note that I'm just the hopefully helpful
messenger here; don't know James personally.)

James, I suppose it'd help if you sketched what's interesting to you in a
bit more detail than just "incremental LTO", and the amount of work/time
you'll be able to invest, roughly.


Grüße
 Thomas


>> > If not, what would be the appropriate method to contact the
>> > mentor (Jan Hubička)?
>>
>> He's reading this list, but I've now also put Honza in CC.
>>
>>
>> Grüße
>>  Thomas
-----------------
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