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

[Matt Arsenault via llvm-commits]

================
@@ -16464,8 +16464,8 @@ type.
 
 Semantics:
 """"""""""
-Follows the IEEE754 2008 semantics for minNum, except for handling of
-+0.0 vs -0.0. This matches the behavior of libm's fmin.
+Follows the IEEE754 2008 semantics for minNum.
+This also matches the behavior of libm's fmin.
----------------
arsenm wrote:

I actually think we should change the intrinsic to match the stricter 2019 signed zero behavior. The old behavior is equivalent to a stricter behavior with the nsz flag. 

This note about "libm's fmin" is too simple given the history of broken libms. 

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