[masklinn]

The question is why one idiom won over the other, which happened a long time ago.

Because as the article notes on "any modern x86 processor" both xor r, r and sub r, r are handled by the frontend and have essentially no cost.

[fjjfnrnr]

Because of encoding size of the machine code, not because of any runtime cost

[masklinn]

> It encodes to the same number of bytes