[Mlir-commits] [mlir] [MLIR][Tensor] Canonicalize fully covering slice insertions into tensors with unit prefixes (PR #92912)

[Renato Golin]

rengolin wrote:

> * Various tiling/fusion transformations look for `extract_slice` ops.

I was going to mention that. We use them and we run canonicalizations in between passes to avoid surprises, but this particular (type of) canonicalization would be the ones causing surprise.

I'm not against a canonical form, far from it, but the points raised here regarding the infrastructure to actually have a canonical form that we can actually use are very pertinent.

We have similar issues in LLVM, where what's considered "canonical" is not absolute to the IR or the target, but relative to the actual pass running on it: what patterns do they recognise, what matchers are available, what you really mean by redundant information.

> You probably should re-read https://sunfishcode.github.io/blog/2018/10/22/Canonicalization.html which is the underlying reference in our documentation: https://mlir.llvm.org/docs/Canonicalization/

On the original document, please refer to the `Excessive canonicalization` section.

https://github.com/llvm/llvm-project/pull/92912