[llvm] [LAA] Add stencil group merging to reduce runtime pointer checks (PR #187252)

[David Sherwood via llvm-commits]

https://github.com/david-arm approved this pull request.

LGTM. I think you've addressed all the comments here, but perhaps @fhahn would like to see the vectoriser tests in the LLVM test suite land first?

https://github.com/llvm/llvm-project/pull/187252