Loop Unrolling from C to C [closed]

Question

I need to build a tool which can unroll loops of programs written in C. The only catch is that the target language has still to be C.

I thought about using llvm compiler to compile C to llvm-IR and to do the loop unrolling. Then I would use this llvm-C-backend to translate the unrolled code in llvm-IR back to C.

Does somebody have other Ideas?
Is there a tool that performs loop unrolling directly on an AST representation of C?
If there is no such tool how would I go about implementing it myself?

(I need to do this to extend a special tool which translates C code with "normal" arithmetic to C code with interval arithmetic. It should perform better when first unrolling loops)

Unfortunately my google search efforts did not turn up much, and I have come to the realization that what I want to do is a very niche thing.

I'd be very grateful if somebody could point me in the right direction.