GCC if (thing - 12 < 3U) pattern

[zbanks]

From @ethteck

but just another thing I remembered: if you're doing an or check for consecutive values of thing like 12, 13, 14, gcc will optimize it as (thing - 12 < 3U)

if (thing - 12 < 3U) expands to if (thing == 12 || thing == 13 || thing == 14). Although they're both equivalent, usually the latter is more natural for smallish numbers of cases.