Bit Bang SPI with Ruby+YJIT

In my previous post, I tested Ruby+YJIT against C, doing bit-bang I2C in the lgpio gem. The results convinced me to just do bit-bang SPI in Ruby. Testing YJIT vs. plain Ruby for this is trivial, but can I compare against C, without actually writing a C implementation? SPI is almost the same as I2C for the purpose of my OLED benchmark. Could I use the I2C results somehow? We’ll get to that, but…