[llvm] Revert "LangRef: Clarify llvm.minnum and llvm.maxnum about sNaN and signed zero (#112852)" (PR #138451)

[Matt Arsenault via llvm-commits]

arsenm wrote:

I am a hard no this. We've never been in a consistent state on this and this makes negative progress towards getting into a sensible state. Reverting the langref doesn't address any of the open bugs.

TLDR:
1. Most code introducing minnum / maxnum should really be emitting minimumnum/maximumnum. Just find and replacing all of these probably addresses most of the open issues. This was the effective behavior on some, but not all targets
2. All code referring to "fmin" or "fmax" should stop doing so and use one of the IEEE derived names. These only cause confusion.
3. CodeGen is still a mixed bag of inconsistency, the current langref establishes the trajectory


https://github.com/llvm/llvm-project/pull/138451