[llvm] [SystemZ] Don't lower float/double ATOMIC_[LOAD|STORE] to [LOAD|STORE] (PR #75879)

[Philip Reames via llvm-commits]

preames wrote:

> I don't really know what arsenm or @preames has/had in mind,

I was only getting the code back into the state it was in before I'd added complexity which never became worthwhile.  I have no strong opinions on how SystemZ should or should not implement this.  Having atomic loads represented by a normal load with the appropriate MMO isn't a bad idea, it just requires a lot more work through generic DAG than I had time to ever finish.  If SystemZ is lowering late enough to avoid those problems (in practice..), then so be it.  

https://github.com/llvm/llvm-project/pull/75879