[llvm] [SystemZ] XPLINK64: emit narrow sign/zero-extend instructions for sub-i32 formal args (PR #206833)

[Ulrich Weigand via llvm-commits]

================
@@ -91,7 +91,7 @@ inline bool CC_XPLINK64_Pointer(unsigned &ValNo, MVT &ValVT, MVT &LocVT,
                                 ISD::ArgFlagsTy &ArgFlags, CCState &State) {
   if (LocVT != MVT::i64) {
     LocVT = MVT::i64;
-    LocInfo = CCValAssign::ZExt;
+    LocInfo = CCValAssign::AExt;
----------------
uweigand wrote:

It would be preferable to extract this into its own PR as well.  It is a logically independent change, and having a separate PR would be a good place to explain this change; and it also might make reverting - if necessary - or backporting either of the PRs easier.

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