[clang] [llvm] [CodeGen][i386] Move -mregparm storage earlier and fix Runtime calls (PR #89707)

[Kees Cook via cfe-commits]

================
@@ -4781,6 +4782,7 @@ CodeGenModule::CreateRuntimeFunction(llvm::FunctionType *FTy, StringRef Name,
         }
       }
       setDSOLocal(F);
+      markRegisterParameterAttributes(F);
----------------
kees wrote:

Oh, I think I see what you mean -- this is the common place where all functions should get their attributes set. Can the libcall code use this? (As in, can we remove `markRegisterParameterAttributes()` entirely and move the logic into `SetLLVMFunctionAttributes()` or is that just fantastic overkill?

https://github.com/llvm/llvm-project/pull/89707