[llvm] [LV] Amend check for IV increments in collectUsersInEntryBlock (PR #108020)

[Hari Limaye via llvm-commits]

hazzlim wrote:

> (looks like the title line of the PR overflowed to the description. Might be good to shorten the title, e.g. `LoopVectorize -> LV` to avoid the too long title)

Nice - done.

Thank you for reviewing - I will land this once checks have passed.

https://github.com/llvm/llvm-project/pull/108020