Is it possible to configure the decomplier so it will generate code for the entire function and not just the parts it thinks can be reached?
The disassemblier sees the alternate code path, but the decomplier won't generate the code for it.
As far as I know there is no such configuration for hex rays decompiler. However it is possible that this code was not generated because of incorrect definition of function prototype (for example the list of parameters of the function is incomplete). You can see a bit more details about this in decompler FAQ .
Another reason I can imagine is incomplete control flow graph of the function. This may happen because a lot of reasons, for example incorrectly defined switch statement in it.