[clang] [llvm] [AMDGPU] Implement variadic functions by IR lowering (PR #93362)

[Jon Chesterfield via cfe-commits]

================
@@ -103,19 +104,27 @@ void AMDGPUABIInfo::computeInfo(CGFunctionInfo &FI) const {
   if (!getCXXABI().classifyReturnType(FI))
     FI.getReturnInfo() = classifyReturnType(FI.getReturnType());
 
+  unsigned ArgumentIndex = 0;
+  const unsigned numFixedArguments = FI.getNumRequiredArgs();
----------------
JonChesterfield wrote:

Yes, I think I can do - the ABI change only affects variadic functions, which currently fatal_error anyway - but I think the C to IR tests will succeed as long as nothing calls va_arg and it stops before codegen.

https://github.com/llvm/llvm-project/pull/93362