[clang] [llvm] [clang-tools-extra] Add out-of-line-atomics support to GlobalISel (PR #74588)

[Thomas Preud'homme via cfe-commits]

RoboTux wrote:

> > Not an expert on atomics, but why would we have a libcall for -O0 but not for O1 in the tests?
> 
> I looked at it for the u?(min|max) and it seemed to boil down to the atomic expand pass being run at -O1 and above.

No sorry, it's not that it's only run at O1 and above, it's that the output is different. At O0 it keeps the cmpxchg whereas at O1 it changes the cmpxchg into a ldxr + stlxr intrinsics.

https://github.com/llvm/llvm-project/pull/74588