[llvm] [LV] Vectorize uncountable early exit store loops with combined conditions (PR #205109)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

> It looks like with this patch we now reach tail folding/epilogue vectorization and guards need adjusting the avoid crashes (previously I think we just checked if the only exiting block is the latch and that rule out early exits; but not anymore)
> 
> foldTailByMasking assert: https://llvm.godbolt.org/z/Y3Er8aj8o
> 
> and I think something similar for epilogue vectorization when forced (or with something like AVX512)

I've added tests and bailouts for both.

https://github.com/llvm/llvm-project/pull/205109