[llvm] [LoopVectorize] Perform loop versioning for some early exit loops (PR #120603)

[David Sherwood via llvm-commits]

https://github.com/david-arm commented:

Updated the patch to deal with review comments and also fix a bug I spotted where I treated loads as being unconditionally dereferenceable after the early exit - see the new test `same_exit_block_no_live_outs_faulting_load_after_early_exit`. This is not true because the first lane of the vector load could be faulting, which would not have happened with the scalar loop.

https://github.com/llvm/llvm-project/pull/120603