@Hotaman, there is a purpose for the checks in the regular GPIO wiring functions. Having the fast_pin functions available gives advanced programmers an extra toolset they can use beyond that. The Photon’s pin mapping does not lend itself to whole-port operations and digitalWriteFast() uses pinSetFast/PinResetFast to do a single command regardless of the target pin state. It is assumed that pinMode() was used prior to using the fast_pin functions.
I believe you are referring to an Arduino register which is not present in the STM32. Furthermore, the GPIO architecture on the STM32 is different. There are several registers in the STM32 for setting a pin’s mode. Can you explain a scenario where fast pinMode() is required?