[llvm] LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (PR #112852)

[Matt Arsenault via llvm-commits]

================
@@ -16574,21 +16574,34 @@ type.
 
 Semantics:
 """"""""""
+Follows the semantics of mininumNumber in IEEE-754-2019, except for signaling NaNs. If either operand
+is an sNaN, the result is always a qNaN. This matches the recommended behavior for the libm
+function `fmin`, although not all implementations have implemented these recommended behaviors.
----------------
arsenm wrote:

Sorry, I got confused again and I'm wondering if it was clearer to describe the snan behavior in terms of 2008 minNum. The signed zero change is easier to explain. I think what's here is clear enough though, especially with the additional notes below

https://github.com/llvm/llvm-project/pull/112852