Stable MIR project - open

[nihalpasham]

Hi,

I don’t know if this is old news but just wanted to drop this here for discussion. Rustlang now has an initiative to provide a stable API for Rust’s MIR that can be used as the foundation for the development of tools that want to perform sophisticated analyses. -https://github.com/rust-lang/project-stable-mir

Stable MIR has been one of my main concerns when working on bringing Rust to different kinds of hardware.

[vaivaswatha]

This is definitely exciting. We can, theoretically, have Rust code pass through pliron!

[nihalpasham]

Exactly, that was my first thought. I'm wondering how much of an effort it would be to lower Rust MIR to NVVM IR (Nvidia's fork of LLVM IR + collection of intrinsics - llvm.nvvm.*), especially since pliron already has an llvm dialect.

[vaivaswatha]

pliron's LLVM dialect doesn't yet support intrinsics but will soon (it's the next item on my to-do list).

But the MIR part needs looking into. We might need an equivalent MIR dialect to behind with.

[nihalpasham]

But the MIR part needs looking into. We might need an equivalent MIR dialect to behind with.

Yeah, I think I can finally get on this with stable-mir.

[vaivaswatha]

pliron's LLVM dialect doesn't yet support intrinsics

Intrinsics should work fine now.

[vaivaswatha]

I'm just trying some experiments, introducing pliron as a backend for rustc: https://github.com/vaivaswatha/rustc_codegen_pliron. This doesn't use the stable MIR API though. It just does what rustc_codegen_cranelift or rustc_codegen_gcc does.

[nihalpasham]

Cool.

If it helps with what you're working on. There's two other custom backends— rustc_codegen_spirv and rustc_codegen_nvvm— maintained as part of the rust-gpu and rust-cuda crates. They are a bit simpler (i.e. I mean much smaller) than the Cranelift or gcc backends and may find it useful for quick experiments. But of course, the flip side is they both focus on producing GPU code, not CPU.

[vaivaswatha]

Yes, I just came across them yesterday. I'm looking at them all, but at the moment, just getting a feel of rustc, and in what way pliron's plugging in can add value.