>> Cortex-M4F has an FPU, i.e., hardware floating point support

Maybe I wasn't clear. I know it has an FPU. I originally wrote the code in fixed point because I knew it would be fast and didn't trust the FPU performance on such a small chip. Now I converted it to float and get the same performance.

I also used an "f" suffix on all constants to avoid accidental software double precision. Also used the GCC flags to force it all to single precision and use the hard float libs.

On smaller chips I used to expect fixed point to be faster than a hardware FPU, but that's no longer the case. They are about equal for me.