[llvm-dev] Beginning developer questions

[Stefanos Baziotis via llvm-dev]

Hi Deep,

1) Kind of. There's Doxygen generated from source automatically, which
shows you many things e.g., members of a type along with some short
documentation (which is taken from the code). It also shows you the
inheritance tree related to this type
Here's an example: https://llvm.org/doxygen/classllvm_1_1LoopInfo.html
It doesn't really matter what this is for now, but you can see e.g., that
LoopInfo inherits from LoopInfoBase. If you scroll down, you can click to
different members and go to a more detailed description further down. You
can open the dropdown menus (e.g., public
functions inherited). And finally, at the top, you can see the file it
appears at. In general, I think that if you start clicking stuff, it's
going to make sense, it's relatively intuitive.

2) Try minimizing the number of parallel threads used. I think by default
Ninja uses all the available threads which in most machines will fill up
the RAM. To limit them, use the -j argument like this: ninja -j8
Another thing that will probably be useful in general is that you can
choose to build specific sub-projects instead of building the whole thing,
like this: ninja -j8 opt

3) Ok, first of all, if you only care about editing and not debugging LLVM
(i.e. launching it with a debugger like gdb), then editors like Vim, Emacs,
4coder, maybe Sublime Text should do the job. I think most people
developing LLVM on Linux use something like this.

Now, if you're interested in IDEs and / or debuggers, well, the news in
Linux is bad IMHO. For example, in my machine, GDB takes _30 seconds_ to
launch the debug build of opt.
So, I couldn't use any IDE because virtually all use GDB under the hood.
Personally, I switched to Windows + Visual Studio just for this reason.
That was an insane productivity boost for me.
But if you need something that works in Linux, you can maybe try LLDB.
Hopefully it will be faster. If yes, you can maybe try hooking it in an
IDE, which I guess won't be trivial.

That said, as I don't develop LLVM in Linux, other people might have better
suggestions.

Best,
Stefanos

Στις Τρί, 12 Ιαν 2021 στις 5:43 π.μ., ο/η Deep Majumder via llvm-dev <
llvm-dev at lists.llvm.org> έγραψε:

> Hello everyone,
> I have been studying the LLVM IR and now want to get into LLVM
> development. I have a few questions regarding that and I would be really
> grateful to get answers for:
>
> 1) The LangRef is an excellent guide/reference to the IR. Is there
> something similar for the codebase (the core llvm to be specific)? Or do I
> have to generate that from the source, in which case how do I do that?
> 2) I tried building just the llvm sub-project, and that is filling up my
> RAM completely during the linking stages, and sends my laptop thrashing. I
> am using Ninja. Is there a way to mitigate this? (I am on Ubuntu 20.04
> Linux, 8 GM RAM, 8 GM swap on an HDD).
> 3) VSCode, at least on my laptop, is very sluggish with such large a
> project. Is there any recommended development environment for Linux (or at
> least something that has been found to work well)?
>
> Thank you for your time!
> Regards,
> Deep
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