[Mlir-commits] [mlir] [vector][mlir] Canonicalize to shape_cast where possible (PR #140583)

[Oleksandr Alex Zinenko]

ftynse wrote:

A brief summary of the call:
 - There is consensus that patterns rewriting `extract` and `broadcast` to `shape_cast` belong to canonicalization. These can be factored out into a new PR and merged following the usual procedure.
 - There is no consensus on `transpose` to `shape_cast` rewriting.
   - A specific request is to show why it is undesirable to canonicalize in the other direction, that is, rewrite `shape_cast` into `transpose`. Alternatively, show where having `shape_cast` instead of transpose is beneficial.
   - The pattern itself may make sense as part of converting vector to LLVM dialect so it doesn't just sit there.
 - We will follow up separately on a collaborative definition of what makes something a canonicalization. Specifically, it was raised that, from systems perspective, it may not be desirable to have rewrites between two equivalent forms without deeming one of those directions canonical.

https://github.com/llvm/llvm-project/pull/140583