[llvm] [Aarch64] [ISel] Don't save vaargs registers if vaargs are unused (PR #126780)

[Pavel Skripkin via llvm-commits]

================
@@ -8189,7 +8189,7 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
   }
 
   // varargs
-  if (isVarArg) {
+  if (isVarArg && DAG.getMachineFunction().getFrameInfo().hasVAStart()) {
----------------
pskrgag wrote:

Thanks! Added `-global-isel-abort=0` to failing test.

https://github.com/llvm/llvm-project/pull/126780