The point is not to know the actual assembly. The point is that you'll never run an operation that might take a non-deterministic amount of time to run.
Contrast to, say, Python (as an obviously exaggerated counterexample). Just calling a function in Python means performing a lookup in a hash table.
Contrast to, say, Python (as an obviously exaggerated counterexample). Just calling a function in Python means performing a lookup in a hash table.