Guard time_spent_in/out_isr with MULTISTEPPING_LIMIT > 1
#27147
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Description
Guard
time_spent_in_israndtime_spent_out_isrwithMULTISTEPPING_LIMIT > 1since the values are not actually used/useful in this case. The compiler doesn't do it for us especially since it won't optimize away even reads on anyvolatilevariables.Benefits
Small speedup in max theoretically achievable stepping speed since there's less computation in the ISR. Example from LPC1769 with 80steps/mm: ~5400mm/s to ~6100mm/s (though note it was pre-optimized locally with
-fltobuild option - for better inlining - and a spattering of[[gnu::section(".ramcode")]]to make sure the stepper ISR code was contained in microcontroller RAM).Before, looking at the step/dir pins with a logic analyzer (at 16Mhz capture rate):
After: