It depends on whether the code is optimized or not. Sometimes, optimized code is next to impossible to decipher.
There may be disassemblers about that will do that for you but I don't know about the quality of code generation. The last time I did this was in 1986 and the reconstituted code was just full of 3 way jumps and gotos.
It might have been easier with the earlier versions of Fortran like Fortran II/58, IV/66 or 77 but not so easy with the later versions with all their module and OO features.