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

[Matt Arsenault via llvm-commits]

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@@ -16723,21 +16723,29 @@ type.
 
 Semantics:
 """"""""""
+Follows the semantics of minimumNumber 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
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arsenm wrote:

I can't decide if this is the correct way to describe it, relative to IEEE. It's IEEE-754-2008 minNum with stronger -0 behavior. This is probably clearer, given this is where the intrinsic got its name from

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