Developer's guide for Chisel?

Question

Basically I would like to start hacking on the internals of Chisel/FIRRTL. It would help if someone could point me to where I could start looking at.

I have been reading through the source code. I so far understand that Chisel has been implemented as Scala library. Each Chisel object has some methods for emitting FIRRTL. After a particular Scala program is run, the objects are traversed and FIRRTL is generated.

What I wanted to know is if I have been looking in the right direction. I still haven't figured where the AST formation for the Chisel modules and the type inference happens. Eventually I will get there, but it would be great if someone could summarize to me places that I should look.

Of course, this is too much of an ask from the Chisel developers, but even some basic information would help!

Anmol, welcome! - introduce yourself - [here](https://stackoverflow.com/users/10114851/anmol-sahoo) — user10186832, Apr 02 '21 at 06:02

Chick Markley · Accepted Answer · 2019-10-22T21:23:16.343

3

I'd say there are two basic places to start. Firrtl is a good start because it's newer than chisel and overall the code base is newer. Firrtl is a parser, transforms and emitters, and those are pretty straightforward. The transforms encapsulate most operations quite nicely

Chisel as an EDSL is much more complicated and quirky. The place to start is in chiselFrontend. The Builder class is the root of the magic for constructing the internal graph that is used to emit chirrtl/high-firrtl. It uses a dynamic variable to provide a place where modules and their components register their creation and connections to the graph.

Hope that helps you get started, happy sleuthing

edited Oct 22 '19 at 21:23

answered Oct 22 '19 at 18:56

Chick Markley

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Thank you. Unfortunately do not have enough reputation to upvote, but I think you have pointer me in the right direction! – Anmol Sahoo Oct 22 '19 at 19:31
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Two videos which may help that get into Chisel and FIRRTL internals: [Chisel Breakdown](https://www.youtube.com/watch?v=2-ZiXNd9wbc) and [FIRRTL Breakdown](https://www.youtube.com/watch?v=qM9G0jr3rLY&t=1325s). – seldridge Oct 22 '19 at 19:52
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Thanks, Glad to hear it. And Checkout @selridge's suggestion too. – Chick Markley Oct 22 '19 at 21:24
Did! Those videos were really helpful! – Anmol Sahoo Oct 28 '19 at 20:37

Developer's guide for Chisel?

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