[llvm] [LoopUnroll] Add flag to enable expensive trip counts for runtime unroll. (PR #171735)

[via llvm-commits]

carlobertolli wrote:

this PR has been replaced by
https://github.com/llvm/llvm-project/pull/181267
and follow ups. It enables runtime unrolling when a #pragma unroll is present (i.e. opts out of checks), which is the right way forward.

https://github.com/llvm/llvm-project/pull/171735