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

[YunQiang Su via llvm-commits]

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@@ -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.
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wzssyqa wrote:

Since C23 doesn't require it and libc implementions doesn't do it.
For some architectures, such as X86/ARM-preV8/MIPS-prer6, it will need more work to archive +0.0>-0.0.
So I think that we should have a intrinsic just suite for libc's fmin/fmax.

Of course, for architectures that have FMINNUM_IEEE/FMAXNUM_IEEE, we can map FMINNUM/FMAXNUM to the _IEEE  ones, just as we did for ARMv8 and MIPSr6. 

I will add more clairification about the history of libm.

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