There's no apparent documentation for this on the AVR variant of GCC.
Likely it means to optimize "more aggressively". Uhm, is gcc
intentionally wasting cycles otherwise? Likely not.
Also, the compilation result is exactly the same size with or
without this attribute.
Before, endstops were checked on every step, wasting precious time.
Checking them 500 times a second should be more than sufficient.
Additionally, an endstop stop now properly decelerates the movement.
This is one important step towards handling accidental endstop hits
gracefully, as it avoids step losses in such situations.
Markus Hitter
Ben Gamari
Michael Moon