[llvm] [IVDescriptors] Don't require nsz/nnan for (min|max)num. (PR #137003)

[David Green via llvm-commits]

davemgreen wrote:

> For the vector-reduction case, we will need to generate one extra op to silence the NaN, as the reduction value is guaranteed no-snan, if the start value isnt' snan.

Do you have a motivating case? Does it look like `maxnum(reduct_iv, load)` or something more complex like `maxnum(reduct_iv, fp_op(..))`. With the second, if you know it is not snan, then I was wondering if it generating the reduction could still be valid.

https://github.com/llvm/llvm-project/pull/137003