[llvm] [LV][NFC] Query UnrollVectorizedLoop before executing the plan (PR #208500)

[David Sherwood via llvm-commits]

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

LGTM. This is fixing an underlying bug with the vectoriser. Once we've started executing the vplan we tell ScalarEvolution to forget the loop and dispositions. It doesn't sound very safe (or at the worst case efficient) to pass the pointer around to external functions that may query the original loop that we've just forgotten.

https://github.com/llvm/llvm-project/pull/208500