Re: GSoC project idea: Separate Host Process Offloading

[Thomas Schwinge <thomas@codesourcery.com>]

Hi!

On 2023-02-02T22:13:20+0100, I wrote:
> On 2023-02-01T16:12:07+0100, Martin Jambor <mjambor@suse.cz> wrote:
>> On Thu, Oct 20 2022, Richard Biener via Gcc-patches wrote:
>>>> Am 20.10.2022 um 14:41 schrieb Jakub Jelinek via Gcc-patches <gcc-patches@gcc.gnu.org>:
>>>> On Thu, Oct 20, 2022 at 12:33:28PM +0000, Michael Matz wrote:
>>>>>> On Thu, 20 Oct 2022, Thomas Schwinge wrote:
>>>>>> This had been done in
>>>>>> wwwdocs commit 5c7ecfb5627e412a3d142d8dc212f4cd39b3b73f
>>>>>> "Document deprecation of OpenMP MIC offloading in GCC 12".
>>>>>>
>>>>>> I'm sad about this, because -- in theory -- such a plugin is very useful
>>>>>> for offloading simulation/debugging (separate host/device memory spaces,
>>>>>> allow sanitizers to run on offloaded code
>>>>>
>>>>> Yeah, I think that's a _very_ useful feature, but indeed ...
>>>>>
>>>>>> (like LLVM a while ago
>>>>>> implemented), and so on), but all that doesn't help -- in practice -- if
>>>>>> nobody is maintaining that code.
>>>>>
>>>>> ... it should then be somewhat maintained properly.  Maybe the
>>>>> MIC-specifics could be removed from the code, and it could be transformed
>>>>> into a "null"-offload target, as example and testing vehicle (and implying
>>>>> that such new liboffloadmic^H^H^Hnull would have its upstream in the GCC
>>>>> repo).  Alas, if noone is going to do that work removing is the right
>>>>> choice.
>>>>
>>>> Yeah.  But we really shouldn't need a large MIC specific library for that,
>>>> everything should be implementable with a simple portable plugin that just
>>>> forks + execs the offloading ELF and transfers data to/out of it etc.
>>>> And the config/i386/intelmic-mkoffload etc. stuff would need to be done
>>>> somewhere in generic code, such that we can do it for all targets.
>>>> Also ideally by using just the normal lto1 with some special option that
>>>> it acts as an offloading compiler, so that we don't need to bother with
>>>> building a separate offloading compiler for it.
>>>> True, everything guarded with #ifdef ACCEL_COMPILER etc. would need to
>>>> change into code guarded with some option.
>>>
>>> Might be a nice GSoC project …
>>
>> I really think it could be.
>
> Agreed!  Something like: "Separate Host Process Offloading"!  (Back
> in October, I actually had made a TODO note to put this one onto
> <https://gcc.gnu.org/wiki/SummerOfCode>, but so far...)
>
>> Would any one of those involved in this
>> thread be willing to mentor it?
>
> I'd offer to co-mentor, but I'd rather not be the only one.

Still looking for someone to join, please!  :-)

> I'm now off for FOSDEM, but unless someone gets it done before, I'll cook
> up a GSoC project idea text when I'm back, on Tuesday.

Here it is:
<https://gcc.gnu.org/wiki/SummerOfCode#Separate_Host_Process_Offloading>.
Please have a look, and fix up if necessary.


Grüße
 Thomas
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