llvm-project VS llvm-cbe

I forgot to say that I use this llvm build. Just download the release and point the clangd server to it.

Xtensa support (esp32). Will be interesting how this will be for Rust and Zig support for esp32

https://github.com/llvm/llvm-project/tree/main/llvm/lib/Targ...

https://www.phoronix.com/news/LLVM-Xtensa-Backend

https://github.com/espressif/llvm-project/issues/4#issuecomm...

https://github.com/ziglang/zig/issues/5467#issuecomment-1465...

Hopefully, in the future the installation will be simpler, as we are trying to upstream our LLVM changes (first 10 patches are already accepted!), and once we manage to upstream LLVM changes we will proceed with upstreaming our Rust fork changes.

The main discussion can be led back to this GitHub issue and this comment; fortunately, we don't need to build espressif's llvm fork anymore as they supply the clangd (this is the language server we need) and you can find the zip here. I'll briefly list down the steps required to set up vim with clangd to take advantage of clangd's features (auto-completion, linting, code refactoring ...)

In my case, it's pretty annoying that the Xtensa platform doesn't have official LLVM support. It's in progress but going very slowly.

The link to the espressive issue trackers: https://github.com/espressif/llvm-project/issues/4

Xtensa. They've got a fork of LLVM that supports it that they're working toward getting upstreamed. The community has a fork of rustc that uses it (and a quickstart crate) while we wait for it to get upstreamed.

https://github.com/espressif/llvm-project/issues/4 is a good example why updating llvm isn't easy and takes a lot of time.

Just to clarify - Gambit, Chicken, and Carp all compile to portable C.

I hadn't realized LLVM mainline doesn't support Xtensa. I'm surprised.

D does support Xtensa via LDC (https://forum.dlang.org/thread/[email protected]...). It looks like GDC also nearly supports it, requiring only a minor patch at present.

A functioning LLVM backend does exist (https://github.com/espressif/llvm-project/issues/4) and might be making very slow progress towards being merged. A quick search shows that it works for Rust. I suspect (but don't know) that it might work for Terra as well.

There's also the LLVM C backend (https://github.com/JuliaComputingOSS/llvm-cbe) but I've no idea how efficient such an approach is when applied to real world embedded tasks.

So how does the LLVM C backend work then?

https://github.com/JuliaHubOSS/llvm-cbe

One alternative worth mentioning, though, would be the LLVM C Backend maintained by the Julia community.

If you drop "easily" and "human" (/s) from your requirements list, then the C backend for LLVM might work. Then you can choose any programming language you want that has LLVM 10-compatible frontend.

If you really must have something that compiles in C (e.g. for a platform where you only have a C compiler) there's an LLVM backend that outputs C code: https://github.com/JuliaComputingOSS/llvm-cbe

You can convert llvm bitcode to C and then use C compiler, there is such project https://github.com/JuliaComputingOSS/llvm-cbe .

I'm really surprised that the LLVM C backends have continually been resurrected then abandoned over the years. It's a good solution to this sort of thing and would enable a lot of cool stuff like Rust to weird embedded platforms. The most recent one is the Julia backend: https://github.com/JuliaComputingOSS/llvm-cbe

Check this project out: https://github.com/JuliaComputingOSS/llvm-cbe.

Well IMO it can definitely be rewritten in Julia, and to an easier degree than python since Julia allows hooking into the compiler pipeline at many areas of the stack. It's lispy an built from the ground up for codegen, with libraries like (https://github.com/JuliaSymbolics/Metatheory.jl) that provide high level pattern matching with e-graphs. The question is whether it's worth your time to learn Julia to do so.

You could also do it at the LLVM level: https://github.com/JuliaComputingOSS/llvm-cbe

For interesting takes on that, you can see https://github.com/JuliaLinearAlgebra/Octavian.jl which relies on loopvectorization.jl to do transforms on Julia AST beyond what LLVM does. Because of that, Octavian.jl beats openblas on many linalg benchmarks

You can try your luck with the "resurrected" C backend: https://github.com/JuliaComputingOSS/llvm-cbe

I don't understand why I see so many requests for LLVM-based languages to change around their backend or IR, that seems to be a huge amount of work for comparatively little benefit. The correct thing to do there is to just add support for those to LLVM.