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

[Stephen Canon via llvm-commits]

stephentyrone wrote:

I mentioned this to Florian in another channel, but:
1. yes, fmaxnm/fminnm have always been fundamentally busted
2. we can avoid the problem for the purposes of lowering C's fmax/fmin without no-honor-nans by multiplying by 1.0 before doing fmaxnm (the multiplication sends sNaN to qNaN, which will then be dropped when the other operand is a number).

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