[llvm-dev] Reach Out about Module Infrastructure Multi-Threading
Nicholas Krause via llvm-dev
llvm-dev at lists.llvm.org
Tue Mar 17 21:07:06 PDT 2020
On 3/17/20 6:16 PM, Johannes Doerfert wrote:
> Apologies for the wait, everything right now is going crazy..
Compiler Folks are very busy people as there aren't as much of us
unfortunately so no need to
apologize. I've yet to heard from someone on the GCC side and will wait
until after GCC 11
is released due to this. Also not to mention the health issues of
> I think we should early in move this conversation on the llvm Dev list
> but generally speaking we can see three options here:
> 1) parallelize single passes or a subset of passes that are known to
> not interfer, e.g. the attributor,
> 2) parallelize analysis pass execution before a transformation that
> needs them,
> 3) investigate what needs to be done for a parallel execution of many
> passes, e.g. How can we avoid races on shared structure such as the
> constant pool.
I was researching this on and off for the last few months in terms of
figuring out how to make the pass manager itself async. Its not easy and
I'm not even
sure if that's possible. Not sure about GIMPLE as I would have to ask
the middle end maintainer on the GCC side but LLVM IR does not seem to
state detection or the core classes and same for the back ends. So yes
this would interest me.
The first place to start with is which data structures are shared for
sure. The biggest ones seem to be basic blocks and function definitions
in terms of shared state, as
those would be shared by passes running on each function. We should
start looking at implementing here locks or ref counting here first if
your OK with that.
It also allows me to understand a little more concrete the linkage
between the core classes as would be required for multi threading LLVM.
it allows us to look into partitioning issues with threads at the same
thing in terms of how to do it.
If others want to chip it as I've CCed the list, that's fine as well and
this should be up for discussion with the whole community.
I've given up on the idea of a async pass manager as it seems to require
IR level detection of changed state between passes but maybe I'm wrong,
> What sounds interesting to you?
> On Tue, Mar 17, 2020, 08:09 Nicholas Krause <xerofoify at gmail.com
> <mailto:xerofoify at gmail.com>> wrote:
> I'm assuming you've been busy as so have I am so I'm pinging this
> On 3/6/20 7:57 PM, Nicholas Krause wrote:
> > Greetings Johannes,
> > I'm pinging you as you wanted to discuss the ModulePass and related
> > infrastructure in terms of
> > making it either multi-threading or preparing for that. You
> stated to
> > wait to this week so now
> > seems a good time.
> > Regards,
> > Nick
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