  High Level Synthesis (HLS) tools offer rapid hardware design from C code, but
their compatibility is limited by code constructs. This paper investigates
Large Language Models (LLMs) for refactoring C code into HLS-compatible
formats. We present several case studies by using an LLM to rewrite C code for
NIST 800-22 randomness tests, a QuickSort algorithm and AES-128 into
HLS-synthesizable c. The LLM iteratively transforms the C code guided by user
prompts, implementing functions like streaming data and hardware-specific
signals. This evaluation demonstrates the LLM's potential to assist hardware
design refactoring regular C code into HLS synthesizable C code.
