recursive to iterative mpn/mul_fft?

[Sven Bettscheider]

Is it possible to change the following functions So that they work 
iteratively rather than recursively?

Version is gmp-5.0.2.

File: /gmp/mpn/generic/mul_fft.c

Line 531:
static void
mpn_fft_fftinv (mp_ptr *Ap, int K, mp_size_t omega, mp_size_t n, mp_ptr tp)

Line 348:
static void
mpn_fft_fft (mp_ptr *Ap, mp_size_t K, int **ll, mp_size_t omega, 
mp_size_t n, mp_size_t inc, mp_ptr tp)