There have been many faster/better replacements for digitalWrite(). What I have not seen is a transparent replacement that works with the stock Arduino core. ArduinoShrink does just that; existing calls to the Arduino functions do not have to be changed, just include ArduinoShrink.
Props to Bill W. for figuring out that LTO allows gcc to evaluate PROGMEM arrays at compile time. Without this technique, ArduinoShrink would've required it's own code for pin to port mapping. Using the digital_pin_to_xxx_PGM arrays defined for each board variant in the AVR core made it possible for me two write the initial release of ArduinoShrink in one evening.