autoload-do-load is a built-in function in `C source code'.

(autoload-do-load FUNDEF &optional FUNNAME MACRO-ONLY)

Load FUNDEF which should be an autoload.
If non-nil, FUNNAME should be the symbol whose function value is FUNDEF,
in which case the function returns the new autoloaded function value.
If equal to `macro', MACRO-ONLY specifies that FUNDEF should only be loaded if
it defines a macro.