Clearing an arbitrary bit actually is supported (as mentioned in the article: "you can set, clear, or toggle any bit with one instruction"). The specific detai

Clearing an arbitrary bit actually is supported (as mentioned in the article: "you can set, clear, or toggle any bit with one instruction"). The specific details require you to dig a bit past explaining just the immediate encoding, but in the clearing case there's a dedicated instruction for clearing the bit specified by the immediate: BIC - Bit Clear (immediate) performs a bitwise AND of a register value and the complement of an immediate value, and writes the result to the destination register. As I mentioned in my other post, zero-rotation encodings are gamed out as well (to allow byte repetition).