I love MLIR. The modularity and friendly abstractions make it incredibly flexible. I've now used it to write _multiple_ domain-specific optimizations and transformations for some of my recent research! It truly bridges the gap between different devices (CPUs, GPUs, TPUs, etc.). I pray more people adopt it so it doesn't end up abandoned!
It’s so hard to get a complete environment up and running. I had a 700-level project that was ripe for MLIR, and I just couldn’t figure out all the tools. I ended up managing with just clang.
Much of MLIR requires compiling from source, from what I can tell, and I just could’ve figure out exactly what to build so that I had access to all of the tool chain from clang to MLIR.
It definitely seems like an active and vibrant community.
Saw the notes about putting distributions together while I was putzing around.
Part of the issue is that I couldn’t find MLIR-specific packages on Ubuntu jammy. Built-from-source was a different version than the packaged LLVM and clang. I couldn’t find a way to get mlir-translate, for example, without compiling from source.
I’m sure I could have figured it out with enough time, but I was short on time. Hopefully graduate with my master’s on Thursday actually.
LLVM IR is just one IR dialect in the MLIR ecosystem, and there are a bunch of (included) higher-level IR dialects that can be transformed (usually, automatically) into the LLVM IR dialect, and from there, the normal LLVM compiler can take over and produce runnable machine code.
Your own languages can target the higher-level IR dialects in MLIR, or directly target the LLVM IR dialect, or both: MLIR is unique in that multiple IR dialects are allowed to be "live" at any time in the compiler, there are no strict "phases" where one IR is lowered, one-shot, into a lower-lever IR, like most compilers require (and compiler books teach).
In the transition, traditional LLVM IR isn’t being left behind. It’s simply a later step in the compilation process. All MLIR is (eventually) translated through LLLVM IR before machine code.
>As I understand it, MLIR is the new subsystem that the LLVM project is transitioning to in the long term, and LLVM IR is the old.
this is very much not a forgone conclusion and many people in LLVM would boo vociferously at the idea (see last year's LLVM US meeting where Johannes Doerfert actually argued the exact opposite - extending LLVM IR to do some/many of the things that MLIR does).
It depends what you mean by "new subsystem" and "transitioning to": what seems like a given is that the notion of "one size fits all" of LLVM IR is behind us and the need to multi-level IR is embraced.
LLVM IR is evolving to accommodate this better, within reason (that is: it stay organized around a pretty well defined core instruction set and type system), and MLIR is just the fully extensible framework beyond this.
It is to be seen if anyone would have the appetite to port LLVM IR (and the LLVM framework) to be a dialect, I think there are challenges for this.
That's something I have thinking about lately. It would be interesting to know if there's any prior work of implementing delimited continuations on MLIR.
I say programs are digraphs and any compiler/compiler-ish library which represents them as serialized textual statements (other than as the final backend output) is just doing it all wrong.
