[clang] [llvm] [SystemZ] Do not extend integer arguments in z/OS XPLINK64 ABI (PR #206833)

[Ulrich Weigand via cfe-commits]

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uweigand wrote:

As @redstar suggested, that should work.   I've now re-checked the tablegen code, and it seems that `CCPromoteToType` still checks the sext/zext flags, and if they are not present, it will actually just implement "anyext".  So this should in fact also be correct after all.

https://github.com/llvm/llvm-project/pull/206833