(I maybe arguing semantics here) 'Same' could be misleading... Same instruction set sure, but not necessarily the same code, nor as performant or predictable. In many coding scenarios neither matters much or at all, but sometimes for outright speed, or guaranteed timing (e.g. generating video signals) assembly is the only way.
Possibly a side point to the OP though, because if I was trying to tackle FFT for the first time, I'd do it in C first, then consider optimising inner loops into assembly. The whole thing done in assembly, from the get go, would be some painful coding I'd imagine. 