[llvm-dev] Fwd: Re: [RFC] Goals for VPlan-based cost modelling

[Anna Sophia Welker via llvm-dev]

   + llvm-dev, which got accidentally dropped - sorry for any duplication

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Hi Sjoerd,

> There was a VPlan round-table at the US LLVM dev conference just a few 
> weeks ago, and I have linked in the people who were involved in this 
> as cost-modeling was one of the topics that was discussed. You may 
> have seen this already, but Dave started doing some work in this area 
> recently:
>
> https://reviews.llvm.org/D89322
> https://reviews.llvm.org/D89323
That's good to know, thanks for linking the experts!
> Just some first high-level remarks on your proposal: I think work in 
> this area would be very valuable and solve a real problem that we 
> currently have. If you plan to choose this as a subject for a master's 
> thesis, you probably need to think about how big of a task this is and 
> having some motivating examples would be good too (but you mentioned 
> some already). To me it sounds like a big task that needs a lot of 
> plumbing in VPlan, but that's why having this discussion here is 
> interesting and hopefully people with more VPlan experience can 
> provide insights.

You are right and I am fully aware that building a fully functional cost 
model for VPlan might be a very big task, well beyond the scope of a 
master thesis. But right now there isn't even clear documentation of how 
exactly such a cost model should look like, and I think it is an 
interesting and important topic to explore. If I end up with a good idea 
, a thesis that discusses the topic so there finally is some 
documentation, and a proof-of-concept implementation, I hope that would 
already be of some value and interest to the community.

But yes, good examples are needed - that's one reason for this RFC, as 
of course my experience in the matter is very localised to a specific 
kind of instructions, and I am sure many members of the community have 
met other issues that could help painting a better picture of what 
should be done.

Best,
Anna

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