[llvm] [clang] [SystemZ] Properly support 16 byte atomic int/fp types and ops. (PR #73134)

[Jonas Paulsson via cfe-commits]

JonPsson1 wrote:

Sorry for the confusion of the files: the tests for __atomic_is_lock_free() and friends are now in back a single file atomic_is_lock_free-i128.c. The C library call is also included as it also changes behavior with this patch.
Current test output in CHECKs, with previous problems remaining.
I see that these can be called for `long double / Atomic` as well, and clang is now changing output with the patch. GCC however seems to return 'true' for any such calls, regardless of alignment / type, so I suspect this is not really expected to work. IIUC, the builtins are only intended for use with integral types. The library call may not be limited to ints. Waiting with these until later.

https://github.com/llvm/llvm-project/pull/73134