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J. Nick Koston
0dc56d7a4d
On 32-bit targets GCC does not optimize 64-bit constant division into a multiply-by-reciprocal, emitting a call to __udivdi3 instead (~650-710 ns on Xtensa @ 240 MHz). Add micros_to_millis() which exploits 1000 = 8 * 125: a free right-shift by 3 followed by Euclidean decomposition with D=125, reducing the 64-bit division to a single 32-bit / 125U that GCC compiles to a multiply-by-reciprocal. Benchmarked at 258 ns per call on ESP32 classic — a 2.5-2.8x speedup. With ~21 millis() calls per loop iteration this saves ~9 us per loop.
