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extmod/utime_mphal: ticks_diff(): Optimize to avoid if conditions.

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This commit is contained in:
Paul Sokolovsky 2016-11-02 02:50:48 +03:00
parent 5fae914326
commit 10bde6933e
1 changed files with 4 additions and 6 deletions
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10
extmod/utime_mphal.c
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@ -89,12 +89,10 @@ STATIC mp_obj_t time_ticks_diff(mp_obj_t end_in, mp_obj_t start_in) {
// we assume that the arguments come from ticks_xx so are small ints
uint32_t start = MP_OBJ_SMALL_INT_VALUE(start_in);
uint32_t end = MP_OBJ_SMALL_INT_VALUE(end_in);
int32_t diff = end - start;
if (diff < (signed)-(MICROPY_PY_UTIME_TICKS_PERIOD / 2)) {
diff += MICROPY_PY_UTIME_TICKS_PERIOD;
} else if (diff >= (signed)(MICROPY_PY_UTIME_TICKS_PERIOD / 2)) {
diff -= MICROPY_PY_UTIME_TICKS_PERIOD;
}
// Optimized formula avoiding if conditions. We adjust difference "forward",
// wrap it around and adjust back.
int32_t diff = ((end - start + MICROPY_PY_UTIME_TICKS_PERIOD / 2) & (MICROPY_PY_UTIME_TICKS_PERIOD - 1))
- MICROPY_PY_UTIME_TICKS_PERIOD / 2;
return MP_OBJ_NEW_SMALL_INT(diff);
}
MP_DEFINE_CONST_FUN_OBJ_2(mp_utime_ticks_diff_obj, time_ticks_diff);