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

[Thomas Preud'homme via cfe-commits]

RoboTux wrote:

> > // At -O0, fast-regalloc cannot cope with the live vregs necessary to
> 
> This sounds extremely unsound

Just to clarify, is the expectation for me to solve this in this patch or can this be done in a separate patch? Note that this is existing code exercised when compiling at -O1 or above (i.e. when not using GlobalISel) for some of the atomics.

Best regards,
Thomas

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