[llvm] [LangRef] No target-specific size limit for atomics (PR #136864)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

We have a mechanism for backend diagnostics, so they can report errors on IR they can't support.

If a frontend wants to generate different code sequences depending on whether the target has atomics of a given width, and we have some targets that don't support arbitrary atomics, then yes, we're stuck with some kind of target-specific check.

https://github.com/llvm/llvm-project/pull/136864