Don't pass the buffer. Use self.output directly.
Don't pass the buffer. Use self.output directly.

No speed loss (maybe small gain). Results quite variable between runs
but I did see this result across 20 runs (others were typically worse):
FFT
  Min rate: 2.81 GFlops
  Max rate: 2.97 GFlops
  Avg rate: 2.92 GFlops

primatelabs/geekbench-swift