search for: va_list_tag

I would like to be able to instrument va_arg, but when I generate a bc file for a test case using: llvm-gcc -O3 -emit-llvm vararg.c -c -o vararg.bc I do not see va_arg. Instead, it seems the args are accessed through %struct.__va_list_tag, which makes things a bit trickier to instrument. Is there a way to force llvm-gcc to use va_arg? Perhaps there is some documentation about va_list_tag or llvm's use of stdarg that would help me understand what is going on? Here is the C code... int sum(int n, ...) { int sum = 0; va_lis...