[llvm] [mlir] [mlir][vector] Add a pass to infer the in_bounds attribute (PR #215340)

[Dhairyashil R G via llvm-commits]

dhairyashilRG wrote:

Closing this. The RFC discourse thread (posts 15-17) settled on removing `in_bounds` rather than inferring it, so a pass whose job is to infer the attribute no longer fits the direction: the agreed order is to prove masks all-true instead.

Nothing here is wasted. The bounds query this pass uses is the same one `eliminateVectorMasks` makes on a `vector.create_mask` operand, and #221595 (merged) made that work for fixed-size masks. I'll reuse this pass scaffolding for a `-vector-eliminate-masks` pass, which gives that utility its first in-tree caller and is the next step in the order agreed in the RFC.

Thanks for the reviews on the earlier revisions, @banach-space and @matthias-springer.

https://github.com/llvm/llvm-project/pull/215340