[llvm] [LV] Stop using the legacy cost model for udiv + friends (PR #152707)

[David Sherwood via llvm-commits]

david-arm wrote:

> I think the test that showed a crash should be https://github.com/llvm/llvm-project/blob/main/llvm/test/Transforms/LoopVectorize/AArch64/conditional-branches-cost.ll#L1359.
> 
> There were a few others I think, but probably the same root cause for all of them

OK I didn't see any crashes when I tested this, so perhaps something has changed?

https://github.com/llvm/llvm-project/pull/152707