[llvm] Revert "LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (#112852)" (PR #168838)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> This is confused. The new definition better matches IEEE, which is what was actually built into hardware. We need the IEEE operation to avoid un-elidable canonicalizes deeper in the backend. You cannot hand wave away signaling nan behavior on these like other operations

The point is since all targets share the same defination, a change on that needs consensus made through all targets. The hardware details (especially there are differences among different targets) are not the only consideration for the defination. And I explained them in details in the following 2 bullets.

https://github.com/llvm/llvm-project/pull/168838