No, the regenerate is creating .cpp and .h files for internal data tables and the code for the solid state machine to process them. It basically has nothing to do with "compiling" other than that it spits out code that needs to be compiled. A preprocessor of sorts if you want to view it that way.

It's a "hardcoded" optimization process whereby we generate all possible decisions into tables so that each decision making step is just a handfull of instructions rather than a lot of complex calculations.
Once generated, it comes out at about 1420Mb worth of sources that gets compiled into static arrays totalling about 470Mb.
Compiling those takes the compiler a while (the bigger part of the 5hours) but only needs to happen once (until they change, which isn't frequent). actual code we work on regularly is fairly limited hence the 10min 'normal dev build' time.

NDA's mean I can't say much about it, but it's related to avionics.