I'm not sure what you're asking here. Nothing stops you from turning on the il0 dump when -openmp is set, if you think that will be helpful. OpenMP debug dumps are available only with a debug compiler of severely restricted availability. The experts, of whom I'm not one, can learn a great deal from the dumps which are available in the standard compiler. As you can see in the -S listing, OpenMP parallel code generally consists of calls to the OpenMP run-time library and a function version of the parallel region which is called by each thread. This will show, for example, whether vectorized code, should that be applicable, is present in both the serial and threaded versions.