[llvm] [FastISel][WebAssembly] Don't perform load folding for atomic load (PR #207728)

[Derek Schuff via llvm-commits]

dschuff wrote:

yeah I think this makes sense.

> we DO have a usable atomic zextload on Wasm (but not sextload apparantly?). 

Yeah, this is actually the reason that the standalone sext instructions were added. The committee didn't want to add atomic versions the whole zoo of existing sextload instructions, so we added standalone sext plus non-extending atomics.

https://github.com/llvm/llvm-project/pull/207728