Re: GSOC

[David Malcolm <dmalcolm at redhat dot com>]

On Mon, 2019-03-25 at 19:51 -0400, nick wrote:
> Greetings All,
> 
> I would like to take up parallelize compilation using threads or make
> c++/c 
> memory issues not automatically promote. I did ask about this before
> but
> not get a reply. When someone replies I'm just a little concerned as 
> my writing for proposals has never been great so if someone just
> reviews
> and doubt checks that's fine.
> 
> As for the other things building gcc and running the testsuite is
> fine. Plus
> I already working on gcc so I've pretty aware of most things and this
> would
> be a great steeping stone into more serious gcc development work.
> 
> If sample code is required that's in mainline gcc I sent out a trial
> patch
> for this issue: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88395
> 
> Cheers,
> 
> Nick

It's good to see that you've gotten as far as attaching a patch to BZ
[1]

I think someone was going to attempt the "parallelize compilation using
threads" idea last year, but then pulled out before the summer; you may
want to check the archives (or was that you?)

IIRC Richard [CCed] was going to mentor, with me co-mentoring [2] - but
I don't know if he's still interested/able to spare the cycles.

That said, the parallel compilation one strikes me as very ambitious;
it's not clear to me what could realistically be done as a GSoC
project.  I think a good proposal on that would come up with some
subset of the problem that's doable over a summer, whilst also being
useful to the project.  The RTL infrastructure has a lot of global
state, so maybe either focus on the gimple passes, or on fixing global
state on the RTL side?  (I'm not sure)   Or maybe a project to be more
explicit about regions of the code that assume that the garbage-
collector can't run within them?[3] (since the GC is state that would
be shared by the threads).

Hope this is constructive/helpful
Dave

[1] though typically our workflow involved sending patches to the gcc-
patches mailing list
[2] as libgccjit maintainer I have an interest in global state within
the compiler
[3] I posted some ideas about this back in 2013 IIRC; probably
massively bit-rotted since then.  I also gave a talk at Cauldron 2013
about global state in the compiler (with a view to gcc-as-a-shared-
library); likewise I expect much of the ideas there to be out-of-date); 
for libgccjit I went with a different approach