The Intel OpenCL SDK will allow you to get designs from code to running in hardware with no HDL. The problems you'll face won't be HDL related, they'll be crappy toolchain related.

Having said that, if you don't know what your design would look like in HDL then your performance will never be good enough to justify doing it on FPGA in the first place. Even if you do the performance will likely not be as good as GPU and probably an order of magnitude worse than an HDL implementation.