[clang] [llvm] [WIP] Expand variadic functions in IR (PR #89007)

[Matt Arsenault via cfe-commits]

================
@@ -115,7 +115,13 @@ void AMDGPUABIInfo::computeInfo(CGFunctionInfo &FI) const {
 
 Address AMDGPUABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
                                  QualType Ty) const {
-  llvm_unreachable("AMDGPU does not support varargs");
+  const bool IsIndirect = false;
+  const bool AllowHigherAlign = true;
+  // Would rather not naturally align values
+  // Splitting {char, short} into two separate arguments makes that difficult.
----------------
arsenm wrote:

I thought all structs under 8 bytes were packed into i32/i64

https://github.com/llvm/llvm-project/pull/89007