Numba - compile time constants optimizations

Question

I have artificial example code JIT-ed using Numba:

import numba
@numba.njit
def f(x, c):
    for i in range(3):
        if c == 0:
            x += 1
        elif c == 1:
            x *= 2
        else:
            assert False
    return x
print(f(3, 0), f(3, 1))

How do I optimize it if c is some constant from small final integer set of values e.g. 0 <= c <= 3?

It is not allowed to move if conditions regarding c out of the loop, of cause it would be an obvious optimization. Because it is an artificial example, in real example loops can be huge and it is not affordable to duplicate loop twice with just 1-2 lines inside of body changed.

Basically I want to make c compile-time constant. Same like C++ can have compile-time constants as template parameters and do all code optimizations related to this.

So I want to tell Numba that parameters c0, c1, etc are compile-time constants and should be handled in such a way that whenever function is called with different value of c Numba should create and compile a separate function instance and do necessary optimization, same like C++ generates each instantiation of templated function when new set of template parameters is passed.

In other words somehow possible values for such constants c should be included into a signature of a function, as I understand Numba generatest separate function code for each different signature, same like C++ templates.

Another case that needs to be optimized is when c is not an argument of a function but a result of some complex expression computation before the beginning of a loop. In this case resulting c is also from a small set of possible values. Maybe this case can be converted to case above by creating a sub-function accepting c as an argument.

In general, I have some nested loops and each loop has some constants that are computed before loop run. Then inside corresponding loops these constants are used inside if conditions. How to force Numba to make optimizations of moving these constant-if conditions out of these loops bodies.

What are your suggestions?