[clang] [llvm] Add support for flag output operand "=@cc" for SystemZ. (PR #125970)

[Ulrich Weigand via cfe-commits]

https://github.com/uweigand commented:

More comments on just the CC optimization part - this is looking really good now, just a few minor issue and some suggestions for further enhancement.   I'll start looking at the rest of the patch again as well.

https://github.com/llvm/llvm-project/pull/125970