[llvm-branch-commits] [mlir] [MLIR][ArmSVE] Add initial lowering of vector.contract to SVE `*MMLA` instructions (PR #135636)

[Andrzej Warzyński via llvm-branch-commits]

https://github.com/banach-space commented:

Thanks Momchil - this is great!

I skimmed through the pattern logic, and it's very neatly written. It's actually quite easy to follow, despite the underlying logic being a bit convoluted - well done! I've left a few minor suggestions, but nothing major.

Also, it seems like we should be able to extend this fairly easily to support NEON as well. Worth thinking about 🙂

Now, overall this patch is quite large, and I’d suggest extracting the end-to-end / integration tests into a separate PR. Additionally, the remaining tests currently use `--convert-vector-to-llvm=`, which lowers all the way to LLVM (i.e., it exercises a lot of patterns). Instead, I’d recommend testing `LowerContractionToSVEI8MMPattern` in isolation and only verifying that the correct sequence of ArmSVE ops (plus some Vector ops) is generated - for example:

```mlir
    (...)
    %33 = arm_sve.smmla %23, %7, %15 : vector<[16]xi8> to vector<[4]xi32>
    %34 = arm_sve.smmla %24, %7, %16 : vector<[16]xi8> to vector<[4]xi32>
    %35 = arm_sve.smmla %31, %13, %15 : vector<[16]xi8> to vector<[4]xi32>
    %36 = arm_sve.smmla %32, %13, %16 : vector<[16]xi8> to vector<[4]xi32>
```

That way, we will:
* reduce noise in the test output (by focusing on a single pattern),
* simplify expected output (fewer ops to match),
* avoid re-testing functionality already covered elsewhere (e.g., `arm_sve.smmla` → `arm_sve.intr.smmla` lowering).

Btw, this is already looking great, and I know I’m asking for a bit of a rewrite (especially around the tests), but I really think it’ll help with long-term maintainability.

https://github.com/llvm/llvm-project/pull/135636