[llvm-dev] [Beginner] Understanding Tablegen language

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Thanks Matt and Thomas. I will go through them.

On Tue, Jul 14, 2020, 1:35 PM Matt P. Dziubinski <matdzb at gmail.com> wrote:

> On 7/13/2020 21:30, Thomas Lively via llvm-dev wrote:
> > Part of the problem is that ISel patterns are like their own DSL inside
> > the TableGen DSL, so keywords like "ins", "outs", and "ops" aren't
> > keywords at the TableGen level, but rather at the level of the ISel
> > system implemented with TableGen. Copying existing patterns and reading
> > the comments in Target.td and TargetSelectionDAG.td are the best ways I
> > know of learning how this works. I haven't seen a separate guide,
> > although it would be very cool if one existed.
>
> FWIW, there are also some third-party resources that may be of help:
>
> "Lessons in TableGen"
> FOSDEM 2019; Nicolai Hähnle
> https://fosdem.org/2019/schedule/event/llvm_tablegen/
> Slides:
>
> https://archive.fosdem.org/2019/schedule/event/llvm_tablegen/attachments/slides/3304/export/events/attachments/llvm_tablegen/slides/3304/tablegen.pdf
>
> Series:
> - What has TableGen ever done for us?:
>
> http://nhaehnle.blogspot.com/2018/02/tablegen-1-what-has-tablegen-ever-done.html
> - Functional Programming:
> http://nhaehnle.blogspot.com/2018/02/tablegen-2-functional-programming.html
> - Bits: http://nhaehnle.blogspot.com/2018/02/tablegen-3-bits.html
> - Resolving variables:
> http://nhaehnle.blogspot.com/2018/03/tablegen-4-resolving-variables.html
> - DAGs: http://nhaehnle.blogspot.com/2018/03/tablegen-5-dags.html
>
> Some of the parts of TableGen used in SelectionDAG are in the backend
> docs (e.g., the keywords OP asked about):
> https://llvm.org/docs/WritingAnLLVMBackend.html#instruction-set
> & https://llvm.org/docs/WritingAnLLVMBackend.html#instruction-selector
> (has a simple example of `PatFrag` for `store`).
>
> There are a few examples of simple .td files an LLVM backend in the
> following:
>
> LLVM backend development by example (RISC-V)
> 2018 LLVM Developers’ Meeting; Alex Bradbury
> https://www.youtube.com/watch?v=AFaIP-dF-RA
>
> 2014 - Building an LLVM Backend - LLVM Developer's Meeting
> https://llvm.org/devmtg/2014-10/#tutorial1
> https://llvm.org/devmtg/2014-10/Slides/Cormack-BuildingAnLLVMBackend.pdf
>
> https://llvm.org/devmtg/2014-04/PDFs/Talks/Building%20an%20LLVM%20backend.pdf
>
> http://web.archive.org/http://llvm.org/devmtg/2014-10/Videos/Building%20an%20LLVM%20backend-720.mov
> http://llvm.org/devmtg/2014-10/#tutorial1
>
> http://www.inf.ed.ac.uk/teaching/courses/ct/other/LLVMBackend-2015-03-26_v2.pdf
>
> llvm-leg: LEG Example Backend
> LEG Example Backend: a simple example LLVM backend for an ARM-like
> architecture: 'LEG'.
> https://github.com/frasercrmck/llvm-leg
>
> Best,
> Matt
>
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