Something doesn't count as speech if it makes sense only to the speaker. But machine code, you'll likely point out, makes sense to anyone trained to read it. And since it makes sense not only to the writer of the code, but to whoever reads the code, it is therefore a form of speech. Let's consider the case of a watch. Before you answer, consider also the following case.
Someone assembles a Swiss watch and drops it in the park.
I pick it up, bring it home, and take it apart. Once I get it apart, I figure out how to make Swiss watches. The difference between the first case and the latter case is intent . In the first case, the watch was intended to communicate something to me, and I recognized the specific intent behind the act. In the second case, the watch was intended to be a timekeeping device, but I used it to learn the art of Swiss watchmaking instead.