Support for LLVM 8/9 (LLVM-51)

[sapir]

I'd like to use this with the current Rust compiler, but Rust currently depends on LLVM 8 or 9.

I got this fork compiling with LLVM 8 here:
https://github.com/sapir/llvm-project/tree/llvm-8-xtensa

I think it works, as I managed to use it to compile an example Rust project as described here, although I haven't actually run the resulting binary on an ESP32 yet.

[sapir]

I think it's working.

At first I got a crash ("Guru Meditation Error") but it's gone now, the example code is working.

[andreisfr]

Hi @sapir , thank you for sharing results of your work. We also ported Xtensa backend to LLVM 8 release and shared patches for upstream. We will soon upload new improvements in current Xtensa backend to github and also we have plans to migrate on LLVM 8/9 release in our repository.

[beriberikix]

LLVM 9 was just announced. Is the new goal to target LLVM 10? https://lists.llvm.org/pipermail/llvm-announce/2019-September/000085.html

[jeandudey]

Any updates on this?

[andreisfr]

Hi,

The Xtensa backend is ported now release 9.0 of the llvm-project, now it is under verification, this version will be uploaded soon.

[aykevl]

Great!

@andreisfr any idea on how/when to continue upstreaming this work? While it's great that the Espressif fork of LLVM is available and at a recent version, it would be far more usable if it was upstream. As a compiler maintainer (for TinyGo), using a fork is impractical as it means depending on speedy updates from Espressif. If we had used your LLVM 7 fork, that would mean we would still have incomplete support for RISC-V and WebAssembly today - which are upstream.

Honestly I think it's best to ping llvm-dev more, especially with the patch series you have published so people have something to look and comment at. Having some sort of green light from LLVM maintainers also helps give some confidence that it's fine to merge these patches.

I would gladly help review patches myself, but I feel too inexperienced with the LLVM backend to give good reviews unfortunately.

[andreisfr]

Hi @sapir , @beriberikix , @jeandudey , @aykevl ! Now current version of the LLVM Xtensa backend is based on release 9.0.1 (default branch in https://github.com/espressif/llvm-project).

[james-callahan]

@andreisfr sounds like this issue can be closed then?